The Best Aquariums in the U.S.
Dive into family fun with a visit to one of our favorite aquariums in the U.S. From coast to coast, there are lots of amazing institutions that offer up-close animal encounters and conservation education. A few of our favorites are the Georgia Aquarium, the Shedd Aquarium, the Monterey Bay Aquarium and the National Aquarium in Baltimore, but you'll have to keep reading to find out which other spots should be on your must-visit list.
This Texas hot spot is well worth a visit, focusing mainly on plants and animals that live in the Gulf of Mexico and the Caribbean Sea. It's home to more than 13,000 animals, from macaws to stingrays to bats.
Star Attraction: Check out the Caribbean Journey, where you can walk through an underwater tunnel and watch sharks swim overhead, see schools of fish in a coral reef and watch 4D movies in a state-of-the-art theater.
Located in scenic La Jolla, the Birch Aquarium at Scripps is a must-visit the next time you're in Southern California. It's filled with hands-on and interactive experiences and encounters, like shark feedings and starfish petting. Step into the Infinity Cube, where you'll see cool bioluminescent creatures that shine in the dark. Click here to see our insider's guide to making the most of your visit.
Star Attraction: Be sure to catch the Kelp Forest Dive show, during which you'll get to watch divers feed the animals and answer kids' questions. Head to the show early to snag a good spot.
Home to over 11,000 animals, there's no shortage of things to do at the Aquarium of the Pacific. Ooh and ahh at the two-story tank right at the aquarium's entrance, head over to the smaller touch pools to get hands-on with aquatic life and participate in parent-and-me classes that teach littles all about a certain animal.
Star Attraction: You can purchase access to Animal Encounters experiences ($109 per person), where you'll get a behind-the-scenes tour of the aquarium and some of its most in-demand inhabitants, including the penguins, sea lions and even sharks for a feeding.
With seabirds, marine mammals, fish and other animals native to the Oregon coast, this gem overlooking Yaquina Bay is the perfect spot for an educational day trip. Interact with critters like sea stars, anemones and crabs in tide pools, ooh and ahh at moon jellies and check out a submerged shipwreck where lots of different species hang out.
Star Attraction: Take a stroll through the shark tunnel, which will make you feel like you're walking beneath the sea as you get 360-degree views of the creatures.
2820 SE Ferry Slip Rd.
Over a day at the North Carolina Aquarium at Pine Knoll Shores, you can follow the journey of loggerhead sea turtles, watch divers swim with the fishes and sharks and say hello to friendly sea otters, and that's just scratching the surface. Be sure to check out their special events too, from summer camps to scavenger hunts.
Star Attraction: If you need a break from the exhibits, head outside to the nature play area, where kiddos can explore two slides, a climbing net, a treehouse platform and a swinging bridge.
Located in Sarasota, Mote Marine Laboratory & Aquarium is home to world-class marine scientists committed researching and educating the public on conservation and sustainable use of our oceans. Say hello to manatees, sea turtles, river otters and other critters, and learn how the scientists take care of them.
Star Attraction: Mote is home to the only Center for Shark Research recognized by the U.S. Congress, where, believe it or not, they're doing cancer research. Check out their 135,000-gallon Shark Habitat and learn all about the ocean's top predators.
While primarily dedicated to marine research and education, the Alaska Sealife Center is also the only permanent marine mammal rescue and rehabilitation facility in the state. During your visit, you'll have the chance to get up close and personal with puffins, octopus, harbor seals, sea lions and other marine life.
Star Attraction: Cozy up to the touch tanks to learn about sea anemones, shrimp, urchins and sea stars. Be sure to chat with staff members to find out more about each of the creatures you're feeling.
It's easy to fill up a day at Florida Keys Aquarium Encounters—go on a guided tour with a marine biologist, watch sharks, grouper and eels in the coral reef tank and touch various shallow water marine species in a tide pool.
Star Attraction: For an extra fee, you can participate in a cool animal encounter, where you'll get to pet stingrays, snorkel with fish or feed and interact with sharks.
Hop over to the Newport Aquarium for a day of nonstop fun. Kids will get to touch sea stars and other creatures in the Touch Pool, see frogs as they climb through tunnels and tubes in the Frog Bog jungle gym and even get up close and personal with stingrays.
Star Attraction: Don't miss the new exhibit Ring of Fire: World of the Octopus, where you'll get to see and learn about the giant Pacific octopus, moon jellyfish and Japanese spider crab.
This small but mighty aquarium is totally worth a visit the next time you're on Oahu. Geared toward the unique aquatic life of Hawaii and the tropical Pacific, you'll have the chance to see everything from jellyfish to giant clams.
Star Attraction: Check out the vibrant Coral Farm, home to lots of colorful fish. The water here is ideal for coral growth, so scientists grow colonies here that are then carefully transferred and shipped to other aquariums and researchers around the world.
The New England Aquarium is home to thousands of animals, from northern fur seals to giant Pacific octopus to African penguins. Learn how sharks have evolved over the years, check out the birds and crabs that live in the Gulf of Maine and get up close and personal with sharks and rays in a touch tank.
Star Attraction: The four-story Giant Ocean Tank is the centerpiece of the aquarium, and you'll see lots of creatures inside, like Myrtle the green sea turtle, moray eels and hundreds of colorful reef fishes.
At the South Carolina Aquarium, you'll get to venture through the state's different regions and see each one's animal inhabitants: bald eagles and river otters in the mountain forest, alligators and rattlesnakes in the coastal plain and sea turtles and fish off the coast.
Star Attraction: Be sure to visit the Zucker Family Sea Turtle Recovery, which is both a hospital and a guest experience. You'll get to watch, as sick and injured turtles are nursed back to health and eventually released.
Located along the banks of the Mississippi River in the historic French Quarter, the Audubon Aquarium of the Americas is home to 10,000 animals of 400 species, including rare and endangered species. Walk through a 30-foot tunnel surrounded by lionfish, yellowtail snapper and moray eels, and see rescued southern sea otters in a specially designed exhibit.
Star Attraction: Check out the aquarium's behind-the-scenes encounters, giving you a chance to pet penguins, snorkel with fish and more.
You might not expect to find an aquarium right in the Mall of America, but you'd be surprised! At Sea Life, you'll see stingrays, sea turtles, sharks, jellyfish and lots more sea creatures—not a bad way to take a break from shopping.
Star Attraction: Pay a visit to the Ray Lagoon. For a fee, you can feed the rays yourself and watch as they gobble up their treats.
Home to both delighted marine animals and a waterfront view, the Monterey Bay Aquarium is a tranquil space for water lovers to stroll through 200 exhibits—from the stingray petting tank to the plexiglass splash cove—and learn about ocean conservation. This aquarium does amazing work for local water-loving creatures by helping out sea otters, bluefin tunas, albatrosses and more with their rescue and release program. Click here to see our insider's guide to making the most of your visit.
Star Attraction: Who can resist feeding times? Younger visitors will love watching penguins gobble down their meal and exploring the kelp forest as divers hand-feed sharks, fishes and other animals. Take a peek into the aquarium now by watching the live webcams here.
A frontrunner for "Largest Aquarium in the World," the Georgia Aquarium is a stunning facility that boasts a huge deep water tank, an award-winning dolphin exhibit and a 4-D theater for a truly unique underwater experience. And when it comes to ocean life, this aquarium is all about rescue, research, rehabilitation and responsibility. Their conservation program extends around the world to help marine mammals all the way in Mexico, Africa, the Amazon and more. Get all our insider tips and tricks by clicking here.
Star Attraction: Their absolutely mind-boggling 6.3 million gallon Ocean Voyager tank is home to four (yes, four) Whale Sharks. And since the Georgia Aquarium is the only place outside of Asia that has successfully been able to house Whale Sharks, it's definitely a must-see exhibit.
As Chattanooga's top attraction, the Tennessee Aquarium is a gem. Their River Journey highlights freshwater species around the country, and the more recent Ocean Journey exhibit includes a large variety of hands-on encounters with rays, macaws, and even has its own butterfly garden. There are even 3D IMAX movies with features like "Flight of the Butterflies" or "Great White Shark" for jaw-dropping entertainment.
Star Attraction: The River Journey exhibit, which earned the title of "largest freshwater aquarium in the world," and showcases their collection of river otters, turtles, alligators and giant catfish.
Mystic Aquarium is way more than a huge fish tank. It's also an oceanography institute that studies the Earth's waters beyond its living things. There's even a theatre where audience members can talk to crew members under the sea directly! And of course, there are plenty of marine animals, from Beluga whales to penguins, for little eyes to enjoy.
Star Attraction: As the Mystic Aquarium has an animal rescue program, it's best to visit one of their rescued friends! Ziggy Star is the Northern fur seal who was found starving and barely alive. After her rehabilitation period in California, she then became a permanent resident of the Mystic Aquarium.
A popular destination for native Chicagoans and tourists alike, Shedd Aquarium homes over 1500 species of fish, marine mammals, birds, snakes, amphibians and insects. Pint-sized patrons can get their hands wet at the touch pool filled with starfish or, through their informative exhibits, become a know-it-all in aquatic ecosystems and the Great Lakes. Click here to see our guide to making the most of your day at the aquarium.
Star Attraction: Meet the belugas, the only all-white whales in the world. Their tank has viewing options both above and below the water for different vantage points. And if you're willing to part with $250/person to meet them, then Shedd Aquarium is the place to do it.
With over 2,200,000 gallons of water, 17,000 specimens and over five floors of themed displays, the National Aquarium is one great way to experience the sea. Each exhibit teaches viewers about different aquatic animals, their survival tactics and environment. The National Aquarium also regularly rescues, rehabilitates and releases marine mammals so the flipper friend you saw last time may not be there the next! Get all our insider's tips and tricks by clicking here.
Star Attraction: Calypso, a 500-pound sea green turtle, is a rescued friend from Long Island when her front left flipper had to be amputated to save her life. She now lives in the Blacktip Reef exhibit.
Be on the lookout for this amazing aquarium in the upcoming years. It's currently expanding (with a goal of doubling in size!) to wow visitors and become Seattle's centerpiece to the waterfront. There are six major exhibits that cover not only underwater life, but also birds that depend on the shores, which includes an impressive 120,000-gallon viewing tank. Check out our insider's guide by clicking here.
Star Attraction: The dive show at Seattle Aquarium is pretty interactive. The divers wear special masks that let them talk to the crowd and even answer their questions—all while underwater!
Splashdown: The Best Aquariums in L.A.
Family Travel > Family Vacation Ideas > The Best Aquariums in the U.S.


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24 dead, more than 230 injured in Oklahoma tornado
0 Comment(s) Print E-mail Xinhua, May 22, 2013
Twenty-four people were killed and 237 others injured when a massive tornado blasted the southern suburbs of Oklahoma City, the capital of the U.S. state of Oklahoma, on Monday, state officials said Tuesday.
Twenty-four people were killed and 237 others injured when a massive tornado blasted the southern suburbs of Oklahoma City, the capital of the U.S. state of Oklahoma, on Monday, state officials said Tuesday. [Xinhua]
The tornado reportedly ripped through Moore in the southern part of the Oklahoma city metropolitan area Monday afternoon, devastating homes and buildings.
The state medical examiner's office said 24 people were confirmed dead, including nine children.
Earlier reports of at least 51 deaths were erroneous, said Amy Elliot, chief administrative officer for the Oklahoma Office of the Chief Medical Examiner. The earlier number likely reflected some double-counted deaths, said Elliot.
Oklahoma Governor Mary Fallin said the death toll could rise because some bodies may have been taken to funeral homes without the government's knowledge.
At a Tuesday afternoon news conference, Fallin said the twister was one of the "most horrific storms and disasters that this state has ever faced." All that remained in some places were "sticks and bricks," she said.
The tornado carved a trail through the area as much as two miles wide (3.2 kilometers) and 17 miles (27.36 kilometers) long, officials said.
Thunderstorms and lightning slowed the rescue effort Tuesday. But more than 100 people had reportedly been pulled from the debris alive.
Firefighters from local fire departments and rescuers from other states worked all night trying to find survivors, and the search and rescue continued on Tuesday.
Monday afternoon's tornado in Moore came after tornadoes and powerful storms ripped through Oklahoma and the Midwest on Sunday and earlier Monday. Two people, both in their 70s, were confirmed dead after tornadoes hit Oklahoma on Sunday, officials said Monday. As many as 28 tornadoes were reported in Oklahoma, Kansas, Illinois and Iowa, according to the U.S. National Weather Service. A combination of factors, including strong winds and warm, moist air banging against dry air, means severe weather could continue sweeping across a wide swath of the U.S. for days, according to CNN.
Deadly tornadoe strikes US state of Oklahoma
Tornadoes slam US state of Oklahoma, for second day
Deadly tornadoes rip through Oklahoma
Powerful tornado strikes Texas town of Granbury
24 people were killed and 237 others injured when a massive tornado blasted the southern suburbs of Oklahoma City, the capital of the U.S. state of Oklahoma, on Monday, state officials said Tuesday.

redpajama_set_name: RedPajamaCommonCrawl


Rain Rain Go Away! And some ARMADA stuff!
Rain rain go away... come again another day (when I'm not here!).
I had a very nice shoot planned today with a Dutch photographer in a sand dune to make some pretty pictures for my members section. Unfortunately it had to be cancelled as the weather is just terrible :(. Good weather for the ducks, as they say. So instead, i'll do some blogging and share some recent images.
The image across is actually a back stage image. It was taken at a shoot a few weeks ago in Belgium when I was trying to get heated up by a radiator by in window in between shots. I think it works well with the rain theme (OK it wasn't raining during the shoot, but it could have been :P).


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Q: How to find min and max in dplyr?
*

*I know the sum of points for each person.

*I need to know: what is the minimum number of points that a person could have. And what is the maximum number of points that a person could have.

What I have tried:
min_and_max <- dataset %>%
 group_by(person) %>%
 dplyr::filter(min(sum(points, na.rm = T))) %>%
 distinct(person) %>%
 pull()
 min_and_max

My dataset:
id   person   points
201  rt99   NA
201  rt99   3
201  rt99   2
202  kt     4
202  kt     NA
202  kt     NA
203  rr     4
203  rr     NA
203  rr     NA
204  jk     2
204  jk     2
204  jk     NA
322  knm3   5
322  knm3   NA
322  knm3   3
343  kll2   2
343  kll2   1
343  kll2   5
344  kll    NA
344  kll    7
344  kll    1

A: Here is the data.table solution -
dataset[, min_points := min(points, na.rm = T), by = person]
dataset[, max_points := max(points, na.rm = T), by = person]

Since I don't have your data, I cannot test this code, but it should work fine.

A: The summarize() verb is what you want for this. You don't even need to filter out the NA values first since both min() and max() can have na.rm = TRUE.
library(dplyr)
min_and_max <- dataset %>%
  group_by(person) %>%
  summarize(min = min(points, na.rm = TRUE),
            max = max(points, na.rm = TRUE))
min_and_max
# A tibble: 7 x 3
 person   min   max
  <chr>  <dbl> <dbl>
1 jk         2     2
2 kll        1     7
3 kll2       1     5
4 knm3       3     5
5 kt         4     4
6 rr         4     4
7 rt99       2     3

dput(dataset)
structure(list(id = c(201, 201, 201, 202, 202, 202, 203, 203,
203, 204, 204, 204, 322, 322, 322, 343, 343, 343, 344, 344, 344
), person = c("rt99", "rt99", "rt99", "kt", "kt", "kt", "rr",
"rr", "rr", "jk", "jk", "jk", "knm3", "knm3", "knm3", "kll2",
"kll2", "kll2", "kll", "kll", "kll"), points = c(NA, 3, 2, 4,
NA, NA, 4, NA, NA, 2, 2, NA, 5, NA, 3, 2, 1, 5, NA, 7, 1)), class = "data.frame", row.names = c(NA,
-21L), spec = structure(list(cols = list(id = structure(list(), class = c("collector_double",
"collector")), person = structure(list(), class = c("collector_character",
"collector")), points = structure(list(), class = c("collector_double",
"collector"))), default = structure(list(), class = c("collector_guess",
"collector")), skip = 1), class = "col_spec"))

A: I would suggest this dplyr approach. You have to summarize data like this:
library(tidyverse)
#Code
df %>% group_by(id,person) %>%
  summarise(Total=sum(points,na.rm = T),
            min=min(points,na.rm = T),
            max=max(points,na.rm=T))

Output:
# A tibble: 7 x 5
# Groups:   id [7]
     id person Total   min   max
  <int> <chr>  <int> <int> <int>
1   201 rt99       5     2     3
2   202 kt         4     4     4
3   203 rr         4     4     4
4   204 jk         4     2     2
5   322 knm3       8     3     5
6   343 kll2       8     1     5
7   344 kll        8     1     7

redpajama_set_name: RedPajamaStackExchange


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Codes, Guidelines and Policies
2014 revised Guidelines for use of...
Advertising a regulated health servicecollapseexpand
Fact Sheets and FAQcollapseexpand
Download a PDF copy of these FAQ on the 2014 revised Guidelines for use of scheduled medicines (161 KB,PDF)
At a meeting on 24 November 2014, the Optometry Board of Australia (the Board) in collaboration with the Royal Australian and New Zealand College of Ophthalmologists (RANZCO) and the Australian Society of Ophthalmologists (ASO) agreed to modify the March 2013 Guidelines for use of scheduled medicines. The Board formally approved the amended 2014 Guidelines for use of scheduled medicines (the guidelines) on 27 November Board 2014.
The amended guidelines aim to make sure that optometrists, as the providers of primary eye care, utilise clear referral pathways to support patient safety and wellbeing in the management of chronic glaucoma.
The Board has developed these frequently asked questions (FAQ) to guide applicants, registrants and their employers. The FAQ aim to answer common queries you might have about the amended 2014 Guidelines for use of scheduled medicines.
1. Who needs to use the revised guideline for scheduled medicines?
The guideline applies to all optometrists who use scheduled medicines. The amended sections refer to treatment of patients with chronic glaucoma; and accordingly apply to optometrists with an endorsement for scheduled medicines.
2. When will these guidelines apply?
These guidelines take effect on 8 December 2014.
3. What has changed?
The change requires that an optometrist who has commenced treating a patient for chronic glaucoma must provide a referral to an ophthalmologist within four months for ophthalmological assessment and advice. The patient must be provided with a copy of the referral.
In the section describing the circumstances when a referral must be made to an ophthalmologist, a new referral trigger has been added for the patient experiencing side effects of treatment for chronic glaucoma.
4. What does referral mean?
A referral means providing a referral letter to the patient and sending a copy to the ophthalmologist or ophthalmology service.
A referral must take place if:
the anti-glaucoma treatment does not stabilise the patient's condition
a patient needs assessment by an ophthalmologist or ophthalmology service for possible surgical intervention or laser treatment, or
a patient experiences side effects of initial treatment.
In any event, the optometrist must provide the patient with a referral to an ophthalmologist or ophthalmology service within four months of commencing treatment for chronic glaucoma.
5. What if a patient does not act on the referral to the ophthalmologist and continues to elect to have their glaucoma managed by an optometrist?
The guideline defines a referral as providing a referral letter to the patient and sending a copy to the ophthalmologist or ophthalmology service.
In any collaborative care arrangement, patients must consent to the arrangement and be clearly informed about who is responsible for their primary eye care and when they are required to attend reviews with each practitioner.
6. I am managing patients with chronic glaucoma without a referral to an ophthalmologist under the March 2013 version of the guideline. What do I have to do now?
It is advised that a patient currently being treated by an optometrist for chronic glaucoma who has not previously been referred to an ophthalmologist should be referred in accordance with this change at the next scheduled review, or prior, if the next scheduled review is later than 8 April 2015.
7. What happens if a patient is transferred to my care or presents who has received initial treatment for chronic glaucoma from another optometrist?
The relevant clinical records should indicate that a referral to an ophthalmologist or ophthalmology service has been made within four months of commencing initial treatment for chronic glaucoma. If there is no evidence of a referral or the patient is unable to confirm or provide evidence that a referral has been made, a referral must be completed.
8. What happens if a patient is transferred to my care or presents who has received initial treatment for chronic glaucoma from another treating health professional such as a general medical practitioner?
If there is no evidence of a referral to an ophthalmologist or the patient is unable to confirm or provide evidence that a referral has been made, a referral must be completed within four months of presentation to the optometrist.
9. What happens if a patient has been referred to a public ophthalmology service within four months of commencing treatment for chronic glaucoma and the patient has yet to be seen by an ophthalmologist?
A clinical record is to be made that confirms the patient is still awaiting consultation by an ophthalmologist and treatment for chronic glaucoma can continue.


Congratulations to the Ohio Historical Society on reaccreditation by American Association of Museums, as well as to the OHS sites newly accredited for the first time. Among those are the Adena Mansion (Chillicothe) and the Johnston Farm (Piqua) [check out their blog], both of which I have visited and really enjoyed. The house museums and the stories at both sites are just fascinating. Furthermore, another newly accredited site is the Armstrong Air & Space Museum (Wapakoneta), which is directed by a friend of mine – so special congrats to him as well.


Serie 204 "150 Jahre Märklin"
AC/Digital/MFX/Sound - In mint condition - In original packaging.
Märklin H0 - 37671 - diesel locomotive series 204 of the SNCB/NMBS - collectors Edition "150 Jahre Märklin - in representative collection showcase.
Metal chassis and enclosure - with digital decoder mfx and sound source-controlled high efficiency propulsion-top speed and acceleration / deceleration adjustable - special engine with electronically supported weight distribution or in compact clock anchor type - 3 axles powered - traction tyres - two-front lights alternating with direction of travel.
Apart from a trial run, the model is unplayed and free of (paint) damage and delivered with all the papers.
Has been tested and works properly.
Please take a good look at the photos for an accurate impression of this lot. The photos are an integral part of the description of this lot.
Bien emballé, la loco roule bien, est un peu bruyante, on dirait qu'elle râle.
Packet erhalten. Gut verpackt. Ware OK.
Over de aanbiedingen en de afhandeling ben ik tevreden. Het product wordt conform afspraak bezorgd, voldoet aan de omschrijving en de betaling wordt op eenvoudige manier geregeld.
Bien reçue (enfin ), emballage trop peu rembouré , un des boggies (les roues) de la locomotive se détachait, j'ai pu le réparer, locomotive capricieuse sur les aiguillages.
Die Lampen sind ja nur gesteckt !! Dieser Modelltyp BR 117 ist tatsächlich etwas problematisch an manchen Weichen aber dafür kann ich nichts!! Das ist Herstellungsbedingt !!!!
Alles prima verzorgd en ingepakt. Hou er rekening mee dat de verzending vanuit Duitsland meer tijd vergt.
Objekte, Verpackung und Transport.Besser geht eben nicht.
Tadelloser sehr schneller Vèrsand. Empfehlenswert.
Essieux bloqués, ne fonctionne pas contrairement au descriptif... gros boulot de nettoyage en perspective.
Sorry but Gauge Z items witch bee send in the Wintertimes often have this Problem!! Only a little bit Lighters petrol on the gear then all is ok !!
Tutto bene solo molta lentezza nella ricezione della merce, opterei per un corriere espresso per la spedizione.
El artículo se ajusta a mis espectativas,la entrega muy rápida, aunque el paquete de envío lo he visto un poco debil.
You can pick up this lot from the seller: Hausen am Tann (), Germany.


The American labor force is undergoing a fundamental shift as more people become freelancers, contract workers, and part-timers – bringing new flexibility but also new insecurities.
Clockwise, temp manager Chris Aguilar, waitress Kristin Ezell, and attorney Laura Rojas (far left). This is the cover story in the June 9 issue of The Christian Science MonitorWeekly.
Laura Rojas simply couldn't find the time anymore to help her daughter with her homework. And it wasn't as if there was an overwhelming amount to do: Her daughter is in preschool.
But by the time the Florida state public defender left work, picked her children up, and had fixed and finished dinner, it was bedtime for her kids. Nowhere in their conveyor-belt evenings was there a moment to go over the number-of-the-week and letter-writing exercises that her 5-year-old had been assigned.
The final indignity was an orientation workshop for kindergarten. Ms. Rojas found out that next year, when her daughter enrolled in public school, she would face even more demands on her time. Something had to yield: Either she would have to put her daughter in after-school child care or stop working full time.
In January, Rojas made a life-changing – and risky – decision: She quit her job to start her own practice with another lawyer.
Rojas symbolizes a fundamental shift in the American labor force – people becoming independent workers. From the high-tech halls of Silicon Valley to the bedsides of hospital patients, from Miami to Seattle, a growing number of people are forgoing full-time jobs in order to work independently – either by starting their own businesses, freelancing, or becoming contract, on-call, or temp workers.
In some cases, they are being forced out on their own by businesses cutting costs or avoiding benefit payments. In other cases, the move is by choice – a desire to control their lives and shape their futures.
The rise of the independent workforce is reshaping the life-work balance for thousands of Americans and altering the relationship many others have with their employers. Its emergence marks one more change in the often one-dimensional work model that existed for much of the postwar era, in which people toiled loyally for one firm for 40 years, then took a pension and retired to Tampa or Tucson.
In today's work world, people shift jobs and careers at the click of a mouse. Now comes the independent economy, which takes the culture of flexibility one step further – with some people working on their own terms, others scrambling for whatever short-term gigs they can find, and virtually all missing out on traditional company-provided dental plans and 401(k)s.
•The share of workers that had temporary, contract, or other nontraditional jobs rose from 11 percent in 2005 to 18 percent in 2013, according to a survey of large companies by Staffing Industry Analysts.
•A business survey conducted by Ardent Partners, a management research firm, found that about 30 percent of company workforces are now made up of non-full-time employees – up from an estimated 10 to 12 percent before the recession.
•Since 2011, the overall number of independent workers has grown more than 15 percent, to 17.7 million, according to a survey from MBO Partners, a business services firm.
And experts for all three research companies expect the growth to continue. Staffing Industry Analysts projects that the number of temporary employees, a subset of independent workers, will grow 3.1 percent annually through 2022, compared with overall employment growth of 1 percent. Ardent Partners foresees 30 percent growth in the broader nontraditional workforce over the next three years, while MBO Partners estimates that the number of independent workers will rise 35 percent by 2018.
Analysts cite a plethora of reasons for the rise in nontraditional jobs. Companies are looking for more flexible workforces. Millennials want more control over their time. Technology is allowing workers and businesses to find each other more efficiently than ever before.
The shift was also accelerated by the Great Recession.
The effect on workers is mixed. Many people opt out of full-time jobs so they can choose the type of work they want and the venue in which to do it – on the back deck, for instance, with an espresso in their hand and an Irish setter at their feet. But the tailored schedule and canine companionship comes with a price – less predictable paychecks and no paid vacations.
Who wins and loses in the flex economy?
In 2012, E. Dumond was working as a nurse in the obstetrics and gynecology ward of Jackson Memorial Hospital in Miami. The hospital is the flagship institution of Miami-Dade County's Jackson Health System (JHS).
The big health-care provider wasn't doing well at the time. Coming out of the recession and facing stiff competition, JHS had lost hundreds of millions of dollars over the previous four years. So the company decided to lay off 900 full-time employees and hire 350 workers on a flexible schedule in a bid to make the troubled network more competitive. Ms. Dumond was one of the employees who received a notice: She could either come back to work as a part-timer or look for work elsewhere.
The native of Haiti took the part-time job, which was working as a nurse at a local county jail serviced by JHS. Over the past two years, she has logged about the same number of hours as she did when she was a full-time employee. She enjoys working at the correctional facility, has kept most of her benefits, and is paid about $4 per hour more, because jail wages are higher than those in the hospitals.
Still, she wants to go back to being officially full time. Last December, when a family member died, she was told she would have to use vacation days to attend his funeral, rather than take a funeral leave, which is offered only to full-time employees. And while her hours have been consistent in the past, she has no guarantee that they won't be cut in the future.
Dumond's predicament reflects a new reality behind the rise of the independent economy. Traditionally, temporary and other contingent workers have been the first fired, first rehired in times of economic distress. The recent downturn, in one way, was no exception. Companies quickly shed their payrolls of temporary employees early in the recession – their numbers declined by more than 30 percent from the beginning of the downturn to its lowest point.
But this time, almost five years after the official end of the recession, many companies haven't sought to rehire workers and return to prerecession employment levels. Instead, some have found that having a large nontraditional workforce makes them more competitive.
A more adaptable workforce can help companies more easily scale production up or down to meet demand. While industries across the board are embracing a less permanent workforce, the technology and health-care industries have been among the most aggressive in adopting it.
That was certainly the professed rationale behind the JHS moves. The health-care system's president and CEO, Carlos Migoya, argued at the time that he had no other choice.
In 2012, the hospital system turned a profit for the first time since 2007, which Mr. Migoya credited in part to the $97 million in savings from reduced personnel expenses. It's set to see another surplus this year. JHS has hired back many of the workers it laid off, though the number of full-time staff is still not as high as it was before the peak, says Martha Baker, president of SEIU Local 1991, a union that represents 4,000 nurses, physicians, and other medical professionals at the health-care firm. Dumond is one of those still considered part time.
Not everyone is convinced that the sudden boom in independent employees represents a permanent shift in the economy. Some believe the trend won't outlive a robust economic recovery. Their argument is that companies may want a flexible workforce, but in a stronger economy they will have to compete for talent and hire full-time workers.
But at least two factors suggest it may be the new normal: new technology and increased access of independent employees to benefits. The Internet has made it a lot easier for people to market their skills directly to clients.
And it's not just LinkedIn. Writers, Web developers, lawyers, and other freelancers can access online employment marketplaces, such as Elance and oDesk, which recently merged, and FlexJobs. Artists can sell their works directly to consumers on Etsy. Cooks can market their knife skills and prosciutto-wrapped cod on Kitchensurfing, couriers their delivery services on Postmates, and people with other talents on an infinite number of websites linking entrepreneurs with customers.
Indeed, two of the fastest-growing fields of independent workers are personal services, such as fitness training, dog walking, and wealth management, and creative arts, such as writers and musicians, which benefit from Internet marketing, says Emergent Research's Mr. King.
Companies looking to hire temporary workers are also aided by what can be done with the click of a mouse. Advanced scheduling software that lets businesses determine how many employees they need daily, or even hourly, has led retail outlets to increasingly hire on-call workers.
Another factor driving the gig economy is that independent workers no longer have to be tied to a corporation to receive benefits. The passage of the Affordable Care Act, commonly known as "Obamacare," has caused some companies to replace full-time workers with part-timers to avoid having to pay for coverage, but it has also made it easier, and in some cases cheaper, for independent workers to get health insurance. Private entities, such as MBO Partners and the Freelancers Union, are also offering entrepreneurs a variety of benefits, from health and life insurance to retirement plans.
He works as an Internet marketer while traveling the world. He got the idea from a freelancer he met, serendipitously, on a trip to Thailand.
"It just totally blew my mind that this was a thing," says the 20-something from Minnetonka, Minn., via a Skype video call, as he sits in a safari lodge on the outskirts of Kruger National Park in South Africa. Ginsburg picks up his computer and turns the camera toward a dark corner. "There's a bat!" he says.
The bat was hardly the most exciting encounter he'd had that day. In the morning, Ginsburg watched a panther stalk an impala. In the afternoon, on safari, he witnessed a pod of hippopotamuses flash their "fangs" at a watering hole. In between, he did some work – responding to e-mails about monthly Web traffic reports. Ginsburg will return in a few days to Ho Chi Minh City, Vietnam, where he has run his business – developing online marketing campaigns for companies – for six months out of a cafe.
Ginsburg represents perhaps the extreme end of the independent worker movement. It would be easy to dismiss him as just another footloose youth traveling the world while he can – this generation's equivalent of backpacking around Europe.
Except in this case Ginsburg is actually working while he's being itinerant, something that an interconnected world allows him to do. Like many other Millennials, he eschews the corporate world of wingtips and pumps. To be sure, that sense of freedom may not last as young people get older and confront their first mortgage payments and the cost of high-tech strollers. But for now, at least, they are adding to the rise of the independent class.
Some 54 percent of Millennials 18 and older want to start a business, or have already started one, according to a 2011 survey by the Ewing Marion Kauffman Foundation, a Kansas City, Mo.-based group that promotes entrepreneurship and economic independence.
The iGeneration is more likely to quit a job to work for themselves: 57 percent of Millennial freelancers who formerly had traditional jobs say they left because they wanted to work on their own, compared with 42 percent of people from other generations, according to a survey published by oDesk in May 2013. The Great Recession also reinforced that a full-time job is not a guarantee of stability.
Of course, you still have to make money, whether you're working out of an Internet cafe in Bucharest or an industrial park in Buffalo. Independent workers generally don't earn as much as full-time employees. The average yearly income of independent workers is $46,800, which is roughly the same as that of a traditional worker, but since they lose out on benefits, overall compensation is lower, says King.
Ginsburg has his struggles but is surviving. He now earns $2,500 to $3,000 a month. He is working to grow his business – by developing marketing initiatives for a law firm and a credit-card processing company, through Google AdWords and Bing Ads; by publishing a class on marketing through Pinterest; and by generating ad revenue through a skin care and natural health website.
Some actually find it more lucrative to work on their own. Web developer Daniel Cronin quit his job at a marketing firm when he started making more money in the 10 hours a week he freelanced than as a full-time programmer. Now, he regularly charges $100 to $200 an hour for his work. Because he deals directly with clients, he can tailor his talents and energies to what his customers want. He's his own boss. He doesn't have to wait around until a company decides if he deserves a raise.
Mr. Cronin's experience is hardly universal, though. Many independent workers don't even get to choose their own projects, much less make a platinum living.
As many as one-third of nontraditional workers are "task takers," meaning they take whatever work a company that won't hire them full time channels their way, says King. In the retail sector, more employees are getting pushed into on-call jobs, in which they often don't know when they will work until moments before a shift begins.
In other cases, the problem isn't uncertain hours as much as uncertain status. Critics accuse many companies of classifying people who are clearly employees as independent contractors, so they can block them from joining unions, negotiating pay increases, and being eligible for unemployment compensation and other benefits.
"For truck drivers and many others in related blue-collar occupations, classification can mean the difference between a decent, family-supporting job, and working in poverty," says economist Jared Bernstein, in the forward to a recent report by the National Employment Law Project, the Los Angeles Alliance for a New Economy, and the Change to Win Strategic Organizing Center.
Certainly it's been a struggle for Alex Paz. He gave up a job working full time for a trucking company in 2009, soon after his first daughter was born. He no longer wanted to spend so much time on the road. Instead, he signed up with Total Transportation Services Inc. (TTSI) as an "independent owner operator," driving cargo locally.
But, he says, he has little independence, drives a company truck instead of his own, and can't negotiate his rates. Now a father of two, Mr. Paz says he receives no benefits. He's filed a labor claim to get reclassified as an official employee with TTSI instead of an independent contractor.
TTSI spokesman Alex Cherin says that the company wouldn't comment beyond statements it made during trucker protests in April. At the time, the company told local media outlets that contract drivers could apply for "hundreds" of unfilled positions if they wanted to become employees and blamed "outside groups" for stirring up discontent.
Since starting her own law firm, Rojas has faced frustrations of her own. She doesn't like looking for office furniture. She chafes at administrative duties.
But standing in her office's half-furnished waiting room – it's got the essentials, such as a coffee maker, a water cooler, two chairs pilfered from her law partner's former dining room table – she's happy she made the move.
"I like it enough to make it work," she says.
More family time is the biggest benefit. She no longer worries about an interminable commute – her office is 10 minutes from her home – or having to spend so much time in court.


text:
\section{Introduction}
\label{intro}

The thermal emission rate of photons from strongly interacting matter
encodes several interesting properties of the radiating medium (see,
{\it e.g.},
Refs.~\cite{Alam:1999sc,Peitzmann:2002,Arleo:2004gn,Rapp:2009yu,Gale:2009gc}
for reviews). Its spectral slope reflects the temperature of the system
while its magnitude is related to the interaction strength of the charge
carriers. In ultrarelativistic heavy-ion collisions (URHICs), the size
of the interacting fireball is much smaller than the mean-free path of
photons. Thus, the latter can probe the hot and dense interior of the
medium. However, the observed photon spectra receive contributions from
all reaction stages, {\it i.e.}, primordial $NN$ collisions, pre-equilibrium,
quark-gluon plasma (QGP) and hadronic phases, plus final-state decays of
short-lived resonances (these so-called ``direct'' photons exclude
decays of long-lived hadrons, {\it e.g.}, $\pi$ and $\eta$). Calculations of
direct-photon spectra require good control over both the microscopic
emission rates and the space-time evolution of the medium. The latter
not only determines the local emission temperature, but also the
collective-flow field which generally imparts a net blue-shift on the
radiated photons. In addition, the azimuthal asymmetry of the thermal
photon spectra, $v_2^\gamma$, is of
interest~\cite{Chatterjee:2006,Liu:2009kta,Holopainen:2011pd,vanHees:2011vb,Dion:2011pp,Mohanty:2011fp,Shen:2013cca,Linnyk:2013wma}:
since the bulk $v_2$ requires several $\mathrm{fm}/c$ to build up, the observed
value for photons helps to further constrain their emission history.

Direct-photon spectra in URHICs have been extracted in
Pb-Pb($\sqrt{s}=0.017\, A \mathrm{TeV}$) collisions at the Super Proton
Synchrotron (SPS)~\cite{Aggarwal:2000th}, in Au-Au($\sqrt{s} =0.2\, A
\mathrm{TeV}$) at the Relativistic Heavy-Ion Collider
(RHIC)~\cite{Adare:2008fq}, and in Pb-Pb($\sqrt{s}=2.76\,A \mathrm{TeV}$) at the
Large Hadron Collider (LHC)~\cite{Wilde:2012wc}. At SPS, various
theoretical models could approximately reproduce the measured spectra by
adding thermal radiation from an equilibrated expanding fireball to a
primordial component estimated from pp
data~\cite{Srivastava:2000pv,Huovinen:2001wx,Turbide:2003si,Mohanty:2009cd,Bauchle:2010sr}.
The thermal yield prevailed over the primordial one up to transverse
momenta of $q_T \approx2$-$4\, \mathrm{GeV}$. However, a decomposition into
contributions from QGP and hadronic radiation, which would allow for a
better characterization of the origin of the signal, remains
ambiguous. By subtracting the primordial component from their data, the
PHENIX collaboration extracted the ``excess radiation'' and determined
its inverse-slope parameter (``effective temperature'') in Au-Au
collisions at RHIC as
$T_\mathrm{eff}=221\pm19^\mathrm{stat}\pm19^\mathrm{syst} \, \mathrm{MeV}$.
Accounting for the aforementioned blue-shift effect, this result
indicates that most of the radiation emanates from matter temperatures
$T<200 \, \mathrm{MeV}$, challenging the notion of early QGP
radiation~\cite{vanHees:2011vb}. A subsequent first measurement of the
direct-photon $v_2$ supports this finding~\cite{Adare:2011zr}: in the
regime where thermal radiation is expected to be large, $q_T \lesssim 3
\,\mathrm{GeV}$, $v_2^\gamma(q_T)$ turns out to be comparable to that of pions,
which are only emitted at the end of the fireball evolution, {\it i.e.}, at
thermal freezeout, $T_\mathrm{fo} \simeq 100\, \mathrm{MeV}$. The large
$v_2^\gamma$, also found at LHC~\cite{Lohner:2012ct}, thus puts rather
stringent constraints on the origin of the excess photons.

In previous work~\cite{vanHees:2011vb} we have calculated thermal photon
spectra at RHIC, differing from existing calculations in mainly two
aspects. First, a more extensive set of hadronic thermal photon rates
has been employed~\cite{Turbide:2003si}, which, in particular, includes
the contributions from baryons and antibaryons (known to be important in
the dilepton context~\cite{Rapp:2000pe,Rapp:2013nxa}). These rates
approximately match complete leading-order (LO) QGP rates around the
pseudo-critical temperature, $T_\mathrm{pc}\simeq 170
\,\mathrm{MeV}$~\cite{Arnold:2001ms}, thus rendering a near continuous
emissivity across the transition region. Second, a schematic medium
evolution was constructed utilizing a blast-wave type elliptic-fireball
model, quantitatively fit to spectra and $v_2$ of bulk hadrons ($\pi$,
K, p) at $T_\mathrm{fo} \simeq 100\,\mathrm{MeV}$ and multistrange hadrons
(e.g., $\phi$ and $\Omega^-$) at $T_\mathrm{ch}=170\,\mathrm{MeV}$. The
implementation of this ``sequential freezeout'' is phenomenologically
motivated~\cite{He:2010vw}, and, in particular, leads to a saturation of
the bulk-medium $v_2$ close to the transition regime, after about
4-$6\,\mathrm{fm}/c$ for central and semi-central Au-Au collisions at RHIC. As a
result, the direct-photon $v_2$ increased by a factor of $\sim 3$ over
existing calculations, reaching into the error bars of the PHENIX data.

In the present paper we expand on and scrutinize these findings by
extending the calculations to LHC energy and then employing a previously
constructed ideal hydrodynamic bulk-evolution~\cite{He:2011zx} to
conduct a detailed comparison to the emission characteristics of the
fireball.  Much like the latter, this hydro evolution has been
quantitatively constrained by bulk-hadron spectra and $v_2$, utilizing
the concept of sequential freezeout. Both evolutions will be based on a
lattice-QCD equation of state (EoS) for the QGP, matched to a hadron
resonance gas (HRG) with chemical freezeout. The comparisons will
encompass the time evolution of radial and elliptic flow, temperature,
four volume and photon emission profile. Motivated by these comparisons,
which identify the transition region as a key contributor to thermal
photon spectra, we conjecture an enhancement of the currently available
photon emission rates around $T_{\rm pc}$ and explore in how far this
could help to resolve the discrepancies with the data.

Our article is organized as follows. In Sec.~\ref{sec_bulk} we
recall basic ingredients and features of the fireball
(Sec.~\ref{ssec_fb}) and hydrodynamic (Sec.~\ref{ssec_hydro}) bulk
evolutions, including analyses of their time and temperature profiles
of collective flow and four volume (Sec.~\ref{ssec_comp}). In
Sec.~\ref{sec_gam} we investigate the spectra and elliptic flow of
thermal photons emitted from the fireball (Sec.~\ref{ssec_gam-fb}) and
hydro (Sec.~\ref{ssec_gam-hydro}), and (after adding
primordial production) compare to recent RHIC and LHC data. In
Sec.~\ref{sec_disc} we analyze the differences in the fireball and hydro
photon results in view of the insights from Sec.~\ref{sec_bulk} and
discuss possible origins of current discrepancies with data. We
conclude and outline future investigations in Sec.~\ref{sec_sum}.

\section{Bulk Evolution Models}
\label{sec_bulk}
The calculation of thermal-photon spectra in URHICs is based on the
differential emission rate per unit phase space from a strongly
interacting medium of temperature $T$ and baryon-chemical potential
$\mu_B$,
\begin{equation}
\begin{split}
\label{rate}
q_0\frac{dN_{\gamma}}{d^4xd^3q} = &-\frac{\alpha_\mathrm{EM}}{\pi^2}
\ f^B(q_0;T) \\
&\times \im \Pi_\mathrm{EM}^T(q_0=q;\mu_B,T) \ .
\end{split}
\end{equation}
Here, the rate is written in terms of the 3-D transverse part of the
electromagnetic current correlator, $\Pi_\mathrm{EM}^T$, and the thermal
Bose distribution function, $f^\mathrm{B}$, where $q_0=q$ denote the
energy and three-momentum of the photon in the local rest frame of the
medium. This expression is leading order in the electromagnetic (EM)
coupling $\alpha_\mathrm{EM}$, required to produce the photon without
further EM interaction when traversing the fireball. Alternatively, one
may express the rate in terms of photon-production scattering matrix
elements, appropriately convoluted over the thermal distribution
functions of the incoming particles. This approach is usually more
convenient when evaluating tree-level diagrams ({\it e.g.}, $t$-channel meson
exchanges) which are expected to prevail at high photon
energies~\cite{Turbide:2003si}.

The calculation of a thermal photon spectrum in URHICs requires to
integrate the above rate over the entire four-volume of the reaction,
$V_4=\int \text{d}^4x$, accounting for the local temperature and collective
expansion velocity of the emission point. In the following, we will
briefly recall how this four-volume integration is done in two different
models, {\it i.e.}, a schematic blast-wave type fireball (Sec.~\ref{ssec_fb})
and ideal hydrodynamics (Sec.~\ref{ssec_hydro}); both are based on the
same equation of state and fits to the same set of bulk-hadron
observables. This will be followed by a detailed comparison of the flow,
temperature and four-volume profiles (Sec.~\ref{ssec_comp}).

\subsection{Thermal Fireball}
\label{ssec_fb}
The thermal fireball model is based on an isotropically expanding
cylinder with volume
\begin{equation}
V_\mathrm{FB}(t) = \pi a(t) b(t) (z_0 +ct),
\label{V_fb}
\end{equation}
where the elliptic transverse area is characterized by semi-major and
-minor axes, $a(t)$ and $b(t)$, respectively. Their initial values are
estimated from the nuclear overlap at given impact parameter, while the
initial longitudinal size, $z_0$, controls the formation time of the
thermal medium. Assuming a constant total entropy, $S_\mathrm{tot}$, of
the fireball at given collision centrality (fixed by the observed number
of charged particles), the time evolution of the entropy density follows
as $s(t)=S_\mathrm{tot}/V_\mathrm{FB}(t)$. Once the EoS is specified,
i.e., the temperature dependence of $s$, one can convert $s(t)$ into
$T(t)$. In our previous calculations of thermal-photon
spectra~\cite{vanHees:2011vb} we used a quasi-particle QGP EoS with a
first-order transition into a HRG and chemical freezeout at
$T_\mathrm{c}=T_\mathrm{ch}=180\, \mathrm{MeV}$~\cite{Rapp:2000pe}. Here, we
update the EoS with a fit to lattice-QCD data for the QGP
part~\cite{He:2011zx}, smoothly matched to a HRG at
$T_\mathrm{pc}=170\,\mathrm{MeV}$ and chemical freezeout at
$T_\mathrm{ch}=160\,\mathrm{MeV}$, at both RHIC and LHC
energies~\cite{Andronic:2005yp,Stachel:2013zma}. For $T<T_\mathrm{ch}$,
effective chemical potentials for pions, kaons, antibaryons etc., are
introduced~\cite{Rapp:2002fc} to preserve the finally observed hadron
ratios extracted from the chemical-freezeout fits, while strong
processes ({\it e.g.}, $\pi\pi\leftrightarrow\rho$) are assumed to maintain
chemical equilibrium (so-called \emph{partial} chemical equilibrium).
Following Ref.~\cite{He:2011zx} we refer to this EoS as
``\textit{latPHG}''.

\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{pi-pT-spec-0-20-RHIC-lEoS}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{pi-v2-0-20-RHIC-lEoS}
\end{minipage}
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{phi-pT-spec-0-20-RHIC-lEoS}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{phi-v2-0-20-RHIC-lEoS}
\end{minipage}
\caption{(Color online) Fits to the spectra and elliptic flow of light
  hadrons ($T_\mathrm{fo}\simeq110\,\mathrm{MeV}$, upper two panels) and $\phi$
  mesons ($T_\mathrm{fo}=160\,\mathrm{MeV}$, lower two panels) in
  Au-Au($\sqrt{s}=200\,A \mathrm{GeV}$) collisions, using EoS \textit{latPHG}
  within either the fireball (dashed lines) or ideal hydrodynamic model
  (solid lines). The data are taken from
  Refs.~\cite{Abelev:2007rw,Adler:2003kt,Adler:2003cb,Adams:2003xp}.}
\label{fig_hadrons}
\end{figure}

With this set-up, the time dependence of the elliptic radii, $a(t)$ and
$b(t)$, can be constructed with guidance from hydrodynamic
models~\cite{Kolb:2003dz} to approximately reproduce their time
evolution of the radial and elliptic flow, as well as momentum-space
anisotropy~\cite{vanHees:2011vb}. In addition, the idea of sequential
freeze-out has been implemented, {\it i.e.}, a kinetic decoupling of
multistrange hadrons ({\it e.g.}, $\phi$ and $\Omega^-$) at chemical
freezeout. This requires a somewhat faster transverse expansion than in
the original hydro models~\cite{Kolb:2003dz}, but is consistent with the
observed phenomenon of constituent-quark number scaling of elliptic
flow. Importantly, it implies that the bulk-$v_2$ essentially saturates
close to $T_\mathrm{c}\simeq T_\mathrm{ch}$. With a suitable choice in
initial conditions this can be recovered in hydrodynamic
simulations~\cite{He:2011zx}, as we will see below. For a more accurate
reproduction of the final-state hadron multiplicities compared to our
previous work~\cite{vanHees:2011vb} (accounting for the modified EoS,
feeddown and a narrowing of the fireball rapidity distributions due to
the large transverse flow), we have reduced the total entropy in our
fireball by ca.~20\%.  With a freeze-out temperature of $T_\mathrm{fo}
\simeq 100(160) \,\mathrm{MeV}$, the measured $p_T$ spectra and elliptic flow of
light (multistrange) hadrons can be reasonably well described,
cf.~dashed lines in Fig.~\ref{fig_hadrons}\footnote{We have not removed
  the entropy lost to multistrange hadrons (which amounts to $\sim$2\%)
  from the fireball; we neglect this correction in both fireball and
  hydro evolution.}.  One might be concerned that the calculated
$v_2(p_T)$ for thermal pions and protons exceeds the data toward higher
$p_T$, in a regime which is still relevant for thermal photon
production. However, the thermal $p_T$ spectra start to underpredict the
experimental yields data in this regime.  For example, for pions with
$p_T\simeq3\,\mathrm{GeV}$, the thermal spectrum accounts for ca.~65\% of the
experimental yield;
weighting the thermal pion-$v_2$ of $\sim 22\%$ with this fraction gives
$\sim 14\%$, which is not far from the data, $v_2(p_T=3\mathrm{GeV})\simeq11\%$.
While these estimates pertain to kinetic freezeout, the calculations for
the $\phi$ meson represent a snapshot at $T_{\mathrm{ch}}=160\,\mathrm{MeV}$;
they approximately follow the measured spectra and $v_2$ out to higher
$p_T$.

\subsection{Ideal Hydrodynamics}
\label{ssec_hydro}

The hydrodynamic model used in the present study has been described in
detail in Ref.~\cite{He:2011zx}. It is based on the 2+1-dimensional
ideal hydro code of Ref.~\cite{Kolb:2003dz} (AZHYDRO), augmented with the
updated EoS described above (\textit{latPHG}) and initial conditions tuned
to reproduce bulk and multistrange hadron yields, spectra and $v_2$ in
central and semicentral Au-Au collisions at full RHIC energy. Specifically,
a rather compact initial-entropy density profile was adopted, proportional
to the binary-collision density in the optical Glauber model (this is not
unlike what has been obtained in gluon saturation models); with a
thermalization time of $\tau_0=0.6 \; \mathrm{fm}/c$, the central initial
temperature amounts to $T_0=398 \;\mathrm{MeV}$ in 0-20\%
Au-Au($\sqrt{s_{NN}}=200\;\mathrm{GeV}$). Furthermore, a sizable initial radial
flow with a surface value of around $0.13 c$ has been introduced (and a
very small positive $v_2$ to optimize the hadron fits). All of these
features (lattice EoS, compact initial profile and initial radial flow)
lead to a more violent radial expansion, which enables an improved
description of the bulk-hadron $v_2$ at kinetic freezeout even within
ideal hydrodynamics.  At the same time, it generates an earlier
saturation of the bulk-medium $v_2$, which, in particular, requires
multistrange hadrons to freeze out at the chemical freezeout temperature
$T_{\rm ch}$ to reproduce their $p_T$ spectra and $v_2$ (this is not
unwelcome as their hadronic cross sections might be too small to
maintain kinetic equilibrium at lower temperatures). A more violent
expansion has also been identified as a key to the solution of the ``HBT
puzzle''~\cite{Pratt:2008qv}. As emphasized in Ref.~\cite{He:2011zx},
the ideal-hydro tunes are not meant to supplant principally more
realistic viscous evolutions, but rather to explore limitations and
flexibilities in the (ideal-) hydro description, within ``reasonable''
variations of the input. In Fig.~\ref{fig_hadrons}, the solid lines show
some of the hydro results for bulk spectra and elliptic flow in comparison
to RHIC data, which turn out to be very similar to the schematic fireball.

\subsection{Comparison of Space-Time Properties}
\label{ssec_comp}
We are now in position to systematically compare the space-time
evolutions of the schematic fireball and the ideal hydro solution. We
focus on 0-20\% central Au-Au collisions at RHIC energy
($\sqrt{s}=200\,A\mathrm{GeV}$), where both models describe the bulk spectra and
$v_2$ fairly well, based on the same EoS (\textit{latPHG}). Since the
isotropic nature of the fireball is rather schematic compared to the
more elaborate profiles in the hydro evolution, we investigate in this
Section how this difference manifests itself in suitably averaged bulk
quantities, which are expected to play an important role in the photon
emission observables discussed in the next Section.

\begin{figure}[!t]
\begin{center}
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{temp-vs-time-comparison-0-20-RHIC-lEoS}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{RHIC_020p_average_vT}
\end{minipage}

\vspace*{5mm}
\includegraphics[width=0.48\linewidth]{av-int-v2-comparison-0-20-RHIC-lEoS}
\end{center}
\caption{(Color online) Time evolution of average temperature (upper
  left panel), average transverse flow velocity (upper right panel) and
  elliptic flow (lower panel, using a particle mass of $m=300\,\mathrm{MeV}$) in
  the expanding fireball (dashed lines) and hydrodynamic evolution
  (solid lines).  In addition, the upper left panel contains the
  temperature evolution of the central hydro cell (short-dashed
  line).}
\label{fig_T-eps}
\end{figure}
Let us first investigate the time evolution of (average) temperature,
radial and elliptic flow, see Fig.~\ref{fig_T-eps}. The temperature of
the fireball is generally rather close to the average one from the hydro
model, but exhibits systematically slightly higher values in the late
states of the evolution (see upper left panel). This goes along with a
10-15\% longer lifetime of the fireball evolution, indicating a somewhat
slower cooling in the later stages.  The radial flow (upper right panel
of Fig.~\ref{fig_T-eps}) starts out higher in the hydro (due to finite
initial flow), but then levels off more quickly than in the fireball,
eventually dropping below the latter's. For the elliptic flow
comparison, we evaluate the $v_2$ coefficient of the momentum spectra of
particles with an average mass of $300\; \mathrm{MeV}$ at fixed proper time
(lower panel of Fig.~\ref{fig_T-eps}). For the hydrodynamic evolution
this involves a varying temperature while the fireball is spatially
homogeneous at each time.

\begin{figure}[!t]
\begin{center}
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{V4-temp-comparison-0-20-RHIC-lEoS}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}

\vspace*{5mm}
\includegraphics[width=\textwidth]{phot-rate-temp-histo-0-20-RHIC-lEoS-pT05}
\end{minipage}
\includegraphics[width=0.48 \linewidth]{phot-rate-temp-histo-0-20-RHIC-lEoS-pT20}
\end{center}
\caption{(Color online) Temperature evolution of the differential
  emission four-volume (upper left panel) and the double-differential
  photon emission rate (QGP for $T>T_\mathrm{pc}$ and hadronic for
  $T<T_\mathrm{pc}$) for two transverse momenta ($q_T=0.5 \, \mathrm{GeV}$ and
  $q_T=2 \, \mathrm{GeV}$ in the upper right and lower panel, respectively), in
  the expanding fireball (dashed lines) and hydrodynamic evolution
  (solid lines).}
\label{fig_V4-spec}
\end{figure}
To properly interpret the observed photon spectra it is important to
understand how the different emission stages contribute to the total.
From the rate expression, Eq.~(\ref{rate}), one sees that the weighting
is governed by three ingredients: the (differential) four-volume, the
thermal weight (Bose factor) and the EM spectral function (at the photon
point). The former two are governed by the bulk-medium evolution. To
make a closer connection to the underlying matter properties, we now
plot pertinent quantities as a function of temperature, rather than
time. The upper left panel in Fig.~\ref{fig_V4-spec} shows the $T$
dependence of the differential four-volume, $\Delta V_4/\Delta T$,
over temperature intervals of $\Delta T=10\,\mathrm{MeV}$ (and per unit
rapidity). For both fireball and hydro evolution this quantity shows
a distinct maximum structure around the pseudocritical temperature of
$T_\mathrm{pc}\simeq170 \,\mathrm{MeV}$, as a consequence of the rapid change in
the entropy density in the EoS (a remnant of the latent heat). One also
finds a pronounced increase in the differential four-volume in the
late(r) hadronic stages of the collision (stipulating the importance of
a realistic hadronic photon emission rate). Again we find that the ideal
hydro evolution seems to cool somewhat faster than the fireball (this
might slightly change in a viscous evolution where some of the expansion
work is dissipated into heat). Whereas hadron emission at kinetic
freezeout in the hydro evolution is a continuous process, the fireball
freezeout of the entire three-volume occurs at the end of the
evolution. This difference is illustrated in Fig.~\ref{fig_entro}, where
we plot the {\em time} dependence of the fraction of the total entropy
that is above the kinetic-freezeout temperature in the hydro
evolution. This fraction shows a marked departure from one at times
already well before the total lifetime; in contrast, this fraction is
equal to one throughout the fireball evolution.  Recall, however, that
the three-volume at small temperatures must be very similar in both
evolutions, since the total three-volume at freeze-out figures into the
calculation of hadron multiplicities (and spectra), which agree rather
well. Our hydro evolution, on the other hand, does not allow for the
possibility that the freeze-out front ``re-swallows'' previously
frozen-out matter cells. This effect has been studied, {\it e.g.}, in
Ref.~\cite{Grassi:2004dz}, where it was found to be significant even in
the context of hadron observables. It would be interesting to
investigate its impact on thermal-photon spectra.
\begin{figure}[!t]
\centering{\includegraphics[width=0.48\linewidth]{Sfrac}}
\caption{(Color online) Time evolution of the entropy fraction (relative
  to the total) which is in fluid cells at temperatures above the
  kinetic freezeout temperature in the hydrodynamic model.}
\label{fig_entro}
\end{figure}

The increase in emission four-volume is counteracted by the drop in
temperature, suppressing the thermal distribution function in the rate.
This renders the energy argument in the Bose function as an important
scale. As is well known (see, {\it e.g.}, Ref.~\cite{Rapp:2011is} for an
analogous study in the dilepton context), larger energies increase the
sensitivity of the exponential to temperature variations and thus will
lead to a stronger weighting of earlier phases. To exhibit this interplay
in a more realistic way, we include the weights from the QGP and hadronic
spectral functions, $\im \Pi_\mathrm{EM}$, in plotting the
temperature-differential photon spectra for two representative transverse
energies (see upper right and lower panel of Fig.~\ref{fig_V4-spec}); in
other words, we use the full rate expression - the same for both
evolution models - figuring in our comparisons to data in the following
sections (recall that the AMY QGP rates (full LO
result)~\cite{Arnold:2001ms} and the TRG hadronic
rates~\cite{Turbide:2003si} are nearly degenerate around
$T_\mathrm{pc}$, thus avoiding a ``bias'' for either phase). For low
photon momenta (energies), $q_T=0.5\,\mathrm{GeV}$, the ``phase transition''
peak observed in the four-volume is remarkably enhanced, but also the
high-temperature part now exhibits significant emission strength. As
expected, the high-temperature component increases further at larger
momentum ($q_T =2\, \mathrm{GeV}$), albeit not dramatically. A pronounced peak
around $T_\mathrm{pc}$ persists also for these kinematics.

This analysis clearly identifies the importance of the
``pseudo-critical'' regime, around $T_\mathrm{pc}$, for thermal photon
radiation, as found in Ref.~\cite{vanHees:2011vb}. The macrophysics
encoded in the underlying EoS plays an important role through a rapid
change in entropy density over a rather small temperature window,
possibly augmented by a reduction in the velocity of sound,
$c_{\mathrm{s}}^2$, figuring into the hydro evolution (a pertinent
slowing down has not been implemented into the fireball evolution). An
equally important role is plaid by the microphysics, {\it i.e.}, relatively
large hadronic emission rates, comparable to the QGP ones, in the
transition region. Together with substantial flow-induced blue shifts,
this led to generating a sizable photon $v_2$ in our previous fireball
calculations~\cite{vanHees:2011vb}.  These features can be recovered
within hydrodynamic evolutions, \emph{if} the collective flow is built
up sufficiently fast, which can be realized via a modest initial
radial-flow field and a compact initial-density profile. However,
quantitative differences remain, which we further analyze in the
following two sections by comparing the photon spectra from both
approaches with each other and to direct photon data at RHIC and LHC.

\section{Direct Photon Spectra at RHIC and LHC}
\label{sec_gam}
All thermal photon spectra presented in this Section are based on the
same emission rates, from a complete LO calculation in a perturbative
QGP~\cite{Arnold:2001ms} and hadronic many-body calculations
supplemented with $t$-channel meson exchange
reactions~\cite{Turbide:2003si} as well as $\pi\pi$ and $\pi K$
Bremsstrahlung~\cite{Liu:2007zzw}. We also note that short-lived (strong)
resonance decays are usually not subtracted from the experimental spectra.
To account for these ``strong feeddown'' photons ({\it e.g.}, $\Delta\to N\gamma$,
etc.), we follow Refs.~\cite{Rapp:1999us,vanHees:2011vb} by running our
evolution for an extra $1\,\mathrm{fm}/c$ after kinetic freezeout. Strictly speaking,
as elaborated in Ref.~\cite{vanHees:2007th}, these final-state decays would
have to be calculated with slightly modified kinematics compared to thermal
processes (with an extra Lorentz-$\gamma$ factor), but we neglect this
difference in the present study. Ultimately, their contribution to the total
direct-$\gamma$ $v_2$ turns out to be rather modest (e.g., increasing it
by typically 5-10\% around $q_T=2$\,GeV), and even less for the spectra.

\subsection{Thermal Fireball}
\label{ssec_gam-fb}
\begin{figure}[!t]
\centering{\includegraphics[width=0.48 \linewidth]{dnphdqtAu020-eos}}
\caption{(Color online) Comparison of thermal photon spectra in
  Au+Au($\sqrt{s}=0.2A \, \mathrm{TeV}$) collisions from an expanding fireball
  using either a first-order quasiparticle-QGP + HRG EoS with
  $T_\mathrm{c}=T_\mathrm{cm}=180\,\mathrm{MeV}$~\cite{vanHees:2011vb} (dashed
  lines) or a cross-over lQCD + HRG EoS with $T_\mathrm{pc}=170\, \mathrm{MeV}$
  and $T_\mathrm{ch}=160\, \mathrm{MeV}$; red, blue and purple/pink lines
  represent QGP, hadronic and total contributions, respectively.}
\label{fig_fb-rhic-comp}
\end{figure}

We start by updating the fireball calculations at RHIC, which in
Ref.~\cite{vanHees:2011vb} where conducted with a first-order EoS (and a
by now outdated chemical-freezeout temperature of $T_\mathrm{ch}=180\,
\mathrm{MeV}$), by implementing the \textit{latPHG} EoS of Ref.~\cite{He:2011zx}
with chemical freezeout at $T_\mathrm{ch}=160\, \mathrm{MeV}$.  The resulting
thermal spectra are compared to the results of
Ref.~\cite{vanHees:2011vb} in Fig.~\ref{fig_fb-rhic-comp} using the same
total entropy. Since the partitioning of hadronic and QGP emission in
the mixed phase of the first-order transition is now entirely assigned
to the nonperturbative QGP phase, and due to a lower critical
temperature in the \textit{latPHG}, the QGP contribution significantly
increases while the hadronic part decreases compared to the first-order
scenario. This ``reshuffling'' by itself corroborates that the major
portion of the thermal emission originates from around the phase
transition region, independent of the details of the EoS. While the
total (integrated) photon yield is not changed much (analogous to what
has been found for low-mass dileptons~\cite{Rapp:2013nxa}), the
high-$q_T$ part of the spectrum benefits from the increased temperature
in the QGP close to $T_\mathrm{pc}$ and from the later chemical
freezeout in the hadronic phase, which slows down the drop in
temperature that arises in the presence of pion (and other effective)
chemical potentials (for the inclusive yields, and at low $q_T$, the
faster temperature drop is (over-) compensated by the fugacity factors).

\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{photon-rate-0-20-ellfb-RHIC-lEoS}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{photon-v2-0-20-ellfb-RHIC-lEoS}
\end{minipage}
\caption{(Color online) Direct photon spectra (left panel) and elliptic
  flow (right panel) from the expanding fireball in 0-20\%
  Au+Au($\sqrt{s}=0.2\,A \mathrm{TeV}$) collisions with updated total entropy
  using the \textit{latPHG} EoS, compared to PHENIX
  data~\cite{Adare:2008fq,Adare:2011zr}. In the left panel, blue dashed,
  red dashed-dotted, green short-dashed-dotted and purple solid lines
  correspond to hadronic, QGP and primordial contributions, and their
  sum (``total''), respectively. The primordial conribution is based on
  the PHENIX pp parameterization. In the right panel, the red
  short-dashed line is the combined thermal $v_2$; the purple solid and
  long-dashed lines are the total direct-photon $v_2$ using two
  different primordial contributions, either the PHENIX pp
  parameterization (as in the left panel) or an $x_t$-scaling ansatz
  (labeled ``total-2'').  Both primoridial contributions are assumed to
  carry vanishing $v_2$.}
\label{fig_fb-rhic}
\end{figure}
\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{photon-rate-lhc-cent0-40}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{photon-v2-0-40central-ellfb-lhc}
\end{minipage}
\caption{(Color online) Direct photon spectra (left panel) and elliptic
  flow (right panel) from the expanding fireball in 0-40\%
  Pb+Pb($\sqrt{s}=2.76\,A\mathrm{TeV}$) collisions using \textit{latPHG} EoS,
  compared to preliminary ALICE data~\cite{Wilde:2012wc,Lohner:2012ct}.
  In the left panel, red, blue, green and purple lines represent QGP,
  hadronic and primordial contributions, as well as the total, respectively.
  In the right panel we show the combined thermal $v_2$ (red dashed line) and
  the total $v_2$ (purple solid line).}
\label{fig_fb-lhc}
\end{figure}

As mentioned above, we have further updated our fireball calculations by
a careful readjustment of the entropy when using \textit{latPHG}, leading
to a 20\% decrease compared to Ref.~\cite{vanHees:2011vb}. With our nonlinear
dependence of thermal photon production on the charged-particle multiplicity,
$\propto N_\mathrm{ch}^x$ with $x \simeq 1.5$~\cite{Turbide:2003si,Rapp:2013nxa}
(larger at higher $q_T$), the thermal yields are somewhat reduced compared to
our earlier results. The comparison to the PHENIX data for direct photons in
Fig.~\ref{fig_fb-rhic} shows discrepancies at low $q_T$ for both
spectral yields and $v_2$, while for $q_T \ge 2 \, \mathrm{GeV}$ the
calculations are within the experimental errors. We illustrate
uncertainties in the determination of the primordial photon component
due to initial hard $NN$ scatterings: on the one hand, we used a
phenomenological parameterization by the PHENIX collaboration of their pp
data~\cite{Adare:2008fq}; on the other hand, we used the $x_t$-scaling
ansatz of Ref.~\cite{Srivastava:2001bw}, fitted to the high-$q_T$ part
of the PHENIX pp data with a $K$-factor of $2.5$.  The latter spectrum
turns out to be somewhat smaller than the PHENIX parameterization at
small $q_T$. This has rather little impact on the total $q_T$ spectrum,
but it affects the $v_2$ more significantly, inducing an increase of the
total direct-photon $v_2$ of up to $\sim 25\%$ around $q_T\simeq2.5 \,
\mathrm{GeV}$. Further theoretical studies of the hard component are needed to
better quantify this effect, {\it e.g.}, via a suppression of fragmentation
photons or nuclear effects on the initial parton distribution functions.

Finally, we turn to LHC energies, where preliminary direct-photon data
are available from ALICE for 0-40\% central Pb+Pb($\sqrt{s}=2.76\,A
\mathrm{TeV}$) collisions~\cite{Wilde:2012wc,Lohner:2012ct}. We model these
reactions with an average charged-particle multiplicity of $\text{d}
N_\mathrm{ch}/\text{d} y=1040$ over a rapidity interval of $|y|<0.75$. For
primordial photon production from binary $NN$ collisions, we employ the
$x_t$-scaling ansatz~\cite{Srivastava:2001bw}, fitted to the high-$q_T$
ALICE photon spectra with a $K$-factor of 2. The description of the
spectra and $v_2$ is at a comparable level as at RHIC, with indications
for an underestimate in both observables in the regime where thermal
radiation is most significant, cf.~Fig.~\ref{fig_fb-lhc}.

\subsection{Ideal Hydrodynamics}
\label{ssec_gam-hydro}

The direct-photon results from the ideal-hydro tune with \textit{latPHG}
EoS and default emission rates at RHIC are displayed in
Fig.~\ref{fig_hy-rhic}. The QGP contribution to the $q_T$ spectra agrees
within ca.~30\% with the fireball results, but the hadronic portion
falls short by a larger margin, especially toward higher $q_T$. This is
not unexpected as the lifetime of the hydro evolution in the hadronic
phase is noticeably smaller, due to a faster cooling in the local rest
frame of the ideal hydro cells (leading to smaller four-volumes, recall
Fig.~\ref{fig_V4-spec}). In addition, the average temperature in the
late stages is smaller in hydrodynamics than in the fireball (cf.~upper
left panel of Fig.~\ref{fig_T-eps}), which leads to a reduction especially in
the high-$q_T$ region of the hadronic emission. Consequently, the hydro
spectra and $v_2$ come out lower than for the fireball evolution; this
increases the discrepancy with the PHENIX data for both observables,
although not by much. Both evolution models result in an underestimate
of the first two data points of the PHENIX spectra, and barely reach
into the lower portions of the error bars of the $v_2$ data: the maximal
$v_2$ reaches $\sim 4.4\%$ for the hydrodynamic evolution, compared to
$\sim 5.7\%$ for the fireball, both when using the PHENIX pp baseline
spectra (larger for the $x_t$ scaling ansatz).  However, our hydro
results are well above other hydrodynamic calculations reported in the
literature~\cite{Holopainen:2011pd,Dion:2011pp,Shen:2013vja}.  One
difference lies in a faster build-up of the $v_2$, which essentially
saturates when the system reaches the pseudo-critical region in the
cooling process, for both fireball and hydro (cf.~lower panel of
Fig.~\ref{fig_T-eps}). As mentioned above, this feature is essential in
describing the spectra and $v_2$ of multistrange hadrons with an early
kinetic freezeout close to the chemical freezeout temperature, and thus
rather well motivated by hadron phenomenology (including the
constituent-quark number scaling of $v_2$). In the hydrodynamic modeling
this can be realized by initial conditions including a finite transverse
flow at thermalization, together with a compact energy-density profile.
Both features increase the transverse flow early on, which ultimately
leads to an earlier saturation of $v_2$ (since the initial spatial
anisotropy is converted faster into momentum space); it also increases
the blue shift of the photons emitted from around $T_\mathrm{pc}$, which
helps to build up the photon yield with large $v_2$ in the $q_T=2$-$3\,
\mathrm{GeV}$ region. Another difference to existing hydro calculations is the
larger rate in the hadronic phase, in particular the contributions
associated with the photon point of the in-medium $\rho$ spectral
function, which includes sources from interactions involving baryons and
antibaryons~\cite{Rapp:1999us} and higher excited meson
resonances~\cite{Rapp:1999qu}.
\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{dN2piqTdqTdy_original}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{v2-rhic020-hy}
\end{minipage}
\caption{(Color online) Direct photon spectra (left panel) and $v_2$
  (right panel) in Au+Au($\sqrt{s}=0.2\, A\mathrm{TeV}$) using ideal
  hydrodynamics, compared to PHENIX
  data~\cite{Adare:2008fq,Adare:2011zr}; line identifications as
  Fig.~\ref{fig_fb-rhic}.}
\label{fig_hy-rhic}
\end{figure}

Next, we turn to our hydro results at LHC, adopting a similar ansatz for
the initial conditions as at RHIC, {\it i.e.}, with a finite transverse flow
and compact entropy density profile. A factor of $\sim 2$ underestimate of
the preliminary photon spectra measured by ALICE in 0-40\%
Pb-Pb($\sqrt{s} =2.76\, A\mathrm{TeV}$) is found for momenta below $q_T \simeq
2\, \mathrm{GeV}$, see left panel of Fig.~\ref{fig_hy-lhc}. The calculated $v_2$ is
not inconsistent with these data within the current experimental
uncertainties, see right panel of Fig.~\ref{fig_hy-lhc}. Although the hadronic
component in the thermal spectra is again considerably smaller than in
the fireball spectra, the relatively stronger QGP component in both
calculations compared to RHIC renders the overall impact of the hadronic
emission less relevant. The QGP component from the hydro is now somewhat
stronger than from the fireball (especially at high $q_T$), leading to
closer agreement in the total photon spectra and $v_2$, and also with
the data.  Note that the $v_2$ of the thermal component at
$q_T\gsim3\,\mathrm{GeV}$ is significantly larger for the fireball than for the
hydro (cf.~dashed lines in the right  panels of Figs.~\ref{fig_fb-lhc}
and \ref{fig_hy-lhc}, respectively), due to the larger hadronic
component in the former.

\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{dndpt-lhc040-hy}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{v2-lhc040-hy}
\end{minipage}
\caption{(Color online) Direct photon spectra (left panel) and $v_2$
  (right panel) in 0-40\% Pb+Pb($\sqrt{s}=2.76\,A \mathrm{TeV}$) using ideal
  hydrodynamics, compared to preliminary ALICE
  data~\cite{Wilde:2012wc,Lohner:2012ct}; line identifications as in
  Fig.~\ref{fig_hy-rhic}.}
\label{fig_hy-lhc}
\end{figure}

\section{Discussion}
\label{sec_disc}

The general trend of our results reported above for both fireball and
hydrodynamic evolutions is an underestimate of both spectra and $v_2$
for both PHENIX and preliminary ALICE data for photon momenta $q_T \le
3\, \mathrm{GeV}$, which is the region where the thermal radiation is
expected to be most relevant. In the following, we will investigate
possibilities how these deficits may be overcome. For simplicity, we
concentrate on the hydrodynamic space-time evolution for these studies.

One option to increase thermal radiation in URHICs is a decrease of the
thermalization time, $\tau_0$, of the medium, as investigated, {\it e.g.}, in
Refs.~\cite{Chatterjee:2008tp,vanHees:2011vb,Chatterjee:2012dn}.  While
the total yield generally increases above $q_T>1\, \mathrm{GeV}$, its slope
becomes harder and the total $v_2$ becomes smaller, both not favored by
the data. This reiterates the need for a softer radiation source with
larger $v_2$. In the following, we will stick to our default value of
$\tau_0=0.6\,\mathrm{fm}/c$.

\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{dN2piqTdqTdy_comparison}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{v2-rhic020-hy-en}
\end{minipage}
\caption{(Color online) Direct photon spectra (left panel) and $v_2$
  (right panel) from hydrodynamics at RHIC when introducing a
  ``pseudo-critical'' enhancement of QGP and hadronic rates around
  $T_{\rm pc}$, compared to PHENIX
  data~\cite{Adare:2008fq,Adare:2011zr}; line identifications as
  Fig.~\ref{fig_fb-rhic}.}
\label{fig_rhic-ampl}
\end{figure}

In Refs.~\cite{vanHees:2011vb,Rapp:2013ema,Shen:2013vja} an enhancement
of the photon emission rates in the pseudo-critical region, beyond the
default rates used above, has been conjectured. This may not be
unexpected, from a theoretical point of view. On the QGP side, the AMY
rates are based on perturbative parton rescattering, which in other
contexts tends to fall short in producing sufficient interaction
strength, {\it e.g.}, in both phenomenology and lattice calculations of
$\eta/s$ or the heavy-quark diffusion
coefficient~\cite{Schafer:2009dj,Rapp:2009my}. Especially close to the
hadronization transition, confining interactions are expected to play an
important role (as, {\it e.g.}, borne out of lattice calculations for the
heavy-quark free energies~\cite{Kaczmarek:2005ui}). An increase in
partonic scattering rates is a natural mechanism to also increase photon
radiation (see, {\it e.g.}, Ref.~\cite{Goloviznin:2012dy}), which is quite
different from a perturbative scenario with weakly interacting
quasi-particles. On the hadronic side, an enhancement of the current
rates is conceivable as well, since the TRG rates (includiung
contributions from the in-medium $\rho$ spectral function) may not
exhaust all relevant reaction channels in hadronic resonance matter;
investigations to identify and calculate possibly important channels not
considered thus far are in progress~\cite{Holt:2014} (we note in passing
that hadronic Bremsstrahlung is an unlikely candidate since its spectrum
tends to be too soft~\cite{Liu:2007zzw}). To mimic a ``pseudo-critical"
enhancement of our default rates, we increase the latter by a baseline
factor of 2, further amplified up to a maximum factor of 3 at $T_{\rm
  pc}=170\, \mathrm{MeV}$, linearly ramped up from $T=140\,\mathrm{MeV}$ and down until
$T=200\, \mathrm{MeV}$ again. The results are encouraging
(cf.~Figs.~\ref{fig_rhic-ampl} and ~\ref{fig_lhc-ampl}): the description
of both PHENIX and preliminary ALICE spectra and $v_2$ improves
significantly. The calculated $v_2$ at RHIC still tends to only reach
into the lower portions of the experimental errors, but we recall that
larger hadronic contributions, as suggested by the fireball
calculations, would help to increase it further.
\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{dndpt-lhc040-hy-en}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{v2-lhc040-hy-en}
\end{minipage}
\caption{(Color online) Direct photon spectra (left panel) and $v_2$
  (right panel) at LHC with enhanced photon rates around
  $T_\mathrm{pc}$, compared to preliminary ALICE
  data~\cite{Wilde:2012wc,Lohner:2012ct}.}
\label{fig_lhc-ampl}
\end{figure}

Let us briefly expand on a speculation raised in
Ref.~\cite{vanHees:2011vb}, that there might be an hitherto undetermined
uncertainty in the subtraction of the radiative $\omega \rightarrow
\pi^0\gamma$ decays, since the latter have not been explicitly measured
in the low-$q_T$ region in the Au-Au environment. For this purpose, and
to obtain an absolute upper estimate, we simply add to our thermal
spectra (calculated with the amplified rates) the photon contribution
from final-state $\omega$ decays based on our hydro $\omega$ spectra at
thermal freezeout (as a three-pion or $\rho\pi$ resonance, the $\omega$
receives a pion fugacity factor to the third power). The result of this
exercise is shown in Fig.~\ref{fig_rhic-omg}, illustrating an
appreciable effect on both spectra and $v_2$ which would still be
significant if reduced by a factor of 2.
\begin{figure}[!t]
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{dN2piqTdqTdy_omegadecay}
\end{minipage}\hfill
\begin{minipage}{0.48\linewidth}
\includegraphics[width=\textwidth]{v2_omegadecay}
\end{minipage}
\caption{(Color online) Direct photon spectra (left panel) and $v_2$
  (right panel) from hydrodynamics at RHIC when adding $\omega
  \rightarrow\pi^0 + \gamma$ decays at thermal freezeout to the scenario
  with enhanced rates (dash-dotted line), compared to the enhanced-rate
  (dashed line) and default-rate (solid line) scenarios, as well as
  the PHENIX data~\cite{Adare:2008fq,Adare:2011zr}; all calculations use
  the PHENIX pp baseline for the primordial component.}
\label{fig_rhic-omg}
\end{figure}

Finally, we conduct a schematic study of the effect of quark
undersaturation in the early (Q)GP phases, as expected from gluon
saturation models~\cite{McLerran:2014hza}. Similar to earlier
calculations for thermal EM
emission~\cite{Strickland:1994rf,Srivastava:1996qd,Rapp:2000pe}, we find
the gluon Compton process, $gq\to q\gamma$, to still contribute
appreciably (and with a harder slope than in a chemically equilibrated
QGP at the same total entropy), unless the $q\bar q$ undersaturation is
strong enough to largely suppress the early thermal yield altogether.
This suppression would have to be made up by an even larger
enhancement in the later phases compared to what we assumed above.

\section{Summary and Conclusions}
\label{sec_sum}
In this paper we have studied the properties of thermal photon radiation
at collider energies, in an attempt to better understand recent
measurements of direct photon spectra and their elliptic flow. Using QGP
and hadronic thermal emission rates as available from the literature, we
first focused on a detailed comparison of the space-time evolution as
given by a blast-wave type fireball and ideal hydrodynamics. Both were
based on the same equation of state and fits to the same set of hadron
data using the concept of sequential freeze-out for multistrange and
light hadrons. The relevance of this concept for photon radiation lies in
a rather early saturation of $v_2$ and larger blue shifts by the time
the expanding system reaches the phase transition region (in the hydro
model, this can be realized by compact initial conditions with non-zero
radial flow). We have found that the emission characteristics of the QGP
part agree rather well between hydro and fireball, while the latter
leads to significantly larger photon radiation in the hadronic phase,
especially toward higher $q_T$. We traced this back to a slower cooling
with larger average temperatures and radial flow in the fireball, which,
at least in part, is due to a continuous freezeout in hydrodynamics
leading to an appreciable reduction of the ``active'' matter cells in the
later stages of the evolution. Both evolution models clearly identify the
transition region around $T_{\rm pc}\simeq170\,\mathrm{MeV}$ as a key source of
thermal photon emission. After the addition of primordial photons
extrapolated from pp collisions, both hydro and fireball results tend to
be somewhat (although not dramatically) below the measured spectra and
$v_2$ in Au-Au and Pb-Pb collisions at RHIC and LHC, with a preference
for the fireball due to its larger hadronic contribution. We then
shifted our focus to the microscopic emission rates. We argued that an
enhancement of the currently employed emission rates is plausible,
especially in the pseudo-critical region where the medium is expected to
be most strongly coupled. Upon amplifying our default rates by a
baseline factor of 2, reaching up to 3 around $T_{\rm pc}\pm 30\, \mathrm{MeV}$,
we found that the photon results from the hydro model come rather close
to the experimental spectra and $v_2$ within current uncertainties. The
additional hadronic contributions suggested by the fireball model would
further improve the situation. Microscopic calculations of photon rates
to search for additional sources not considered thus far are underway.

\textit{ Acknowledgments.--}
We thank C.~Gale and R.J.~Fries for discussions, and gratefully
acknowledge fruitful exchanges at the EMMI RRTF workshop on
``Direct-photon flow puzzle'' organized by K.~Reygers and
J.~Stachel. This work has been supported by the U.S. National Science
Foundation through grants PHY-0969394 and PHY-1306359, by the
A.-v.-Humboldt Foundation, by NSFC grant 11305089, by the German Federal
Ministry of Education and Research (BMBF F{\"o}rderkennzeichen
05P12RFFTS), and by the Hessian initiative for excellence (LOEWE)
through the Helmholtz International Center for FAIR (HIC for FAIR).

redpajama_set_name: RedPajamaArXiv


Cloud-based video conferencing or video conferencing-as-a-service (VCaaS) allows two or more locations to communicate by simultaneous two-sided audio and video transmissions. In cloud solutions, cloud server is used to transfer, access, and storage data. Video conferencing is different from videophone calls as the former is designed to process multiple locations rather than individuals. VCaaS provides organizations the benefits of high-quality HD video conferencing technology without any major investment in hardware, infrastructure, and network. Cloud-based video conferencing makes video transmissions easily accessible to anyone at any point of time from anywhere.
TechNavio's analysts forecast the Global Cloud-based Video Conferencing market to grow at a CAGR of 39.06 percent over the period 2014-2019.
This report covers the present scenario and the growth prospects of the Global Cloud-based Video Conferencing market for the period 2015-2019. To calculate the market size, the report considers revenue generated from cloud-based video conferencing solutions, software, tools, applications, services, support, and maintenance.
TechNavio's report, Global Cloud-based Video Conferencing Market 2015-2019, has been prepared based on an in-depth market analysis with inputs from industry experts. It covers the Global Cloud-based Video Conferencing market landscape and its growth prospects in the coming years. The report also includes a discussion of the key vendors operating in this market.


text:
Q: org.bukkit.plugin.InvalidPluginException: Abnormal plugin type ------------------------------------------------------------------------------------------------------------------------------------------
I try to code my first plugin, and it's not working, someone help me please. I'm using i use Spigot 1.17.1 to make the plugin, and i run on PaperMC 1.17.1.
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Server message
org.bukkit.plugin.InvalidPluginException: Abnormal plugin type
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:87) ~[patched_1.17.1.jar:git-Paper-100]
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:153) ~[patched_1.17.1.jar:git-Paper-100]
        at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:414) ~[patched_1.17.1.jar:git-Paper-100]
        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:322) ~[patched_1.17.1.jar:git-Paper-100]
        at org.bukkit.craftbukkit.v1_17_R1.CraftServer.loadPlugins(CraftServer.java:393) ~[patched_1.17.1.jar:git-Paper-100]
        at net.minecraft.server.dedicated.DedicatedServer.initServer(DedicatedServer.java:276) ~[patched_1.17.1.jar:git-Paper-100]
        at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1126) ~[patched_1.17.1.jar:git-Paper-100]
        at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:316) ~[patched_1.17.1.jar:git-Paper-100]
        at java.lang.Thread.run(Thread.java:831) [?:?]
Caused by: java.lang.InstantiationException: me.sakuraidev.main
        at java.lang.Class.newInstance(Class.java:636) ~[?:?]
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:83) ~[patched_1.17.1.jar:git-Paper-100]
        ... 8 more
Caused by: java.lang.NoSuchMethodException: me.sakuraidev.main.<init>()
        at java.lang.Class.getConstructor0(Class.java:3517) ~[?:?]
        at java.lang.Class.newInstance(Class.java:623) ~[?:?]
        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:83) ~[patched_1.17.1.jar:git-Paper-100]
        ... 8 more

My code
package me.sakuraidev;

import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.plugin.java.JavaPlugin;

public class main extends JavaPlugin implements CommandExecutor{
    @SuppressWarnings("unused")
    private main Plugin;
    public main(main Plugin) {
        this.Plugin = Plugin;
        Plugin.getCommand("hello").setExecutor(this);
    }
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("Sorry, only players can run this command");
            return true;
        }
        Player p = (Player) sender;

        if(p.hasPermission("hello.use")) {
            sender.sendMessage("hi");
        } else {
            sender.sendMessage("Sorry, but you don't have permission to use this command");
        }
        return false;
    }
}

plugin.yml
main: me.sakuraidev.main
name: plugin
version: '1.0'
description: A plugin
author: SakuraiDev
commands:
  hello:
   description: Hello Command
   permission: hello.use
   permission-message: You do not have permission!
permissions:
  hello.use:
   description: Allows use hello
   default: op

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if necessery, here is the download link
https://file.io/IXD3wqBZ6VJh
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A: The Bukkit API doesn't take constructor methods. Try changing the main method to @Override and named "onEnable". Your main.java should look like this:
package me.sakuraidev;

import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.plugin.java.JavaPlugin;

public class main extends JavaPlugin implements CommandExecutor{
    @SuppressWarnings("unused")
    private main Plugin;
    @Override
    public void onEnable(main Plugin) {
        this.Plugin = Plugin;
        Plugin.getCommand("hello").setExecutor(this);
    }
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("Sorry, only players can run this command");
            return true;
        }
        Player p = (Player) sender;

        if(p.hasPermission("hello.use")) {
            sender.sendMessage("hi");
        } else {
            sender.sendMessage("Sorry, but you don't have permission to use this command");
        }
        return false;
    }
}

Hope that helped :)