Ethnic Studies is an interdisciplinary study focused on the history and current context of race, ethnicity, and indigeneity. This program explores the varied experiences of people of color in the U.S. while critiquing the systems put into place that continue to oppress and marginalize. Today, higher educational institutions across the country are celebrating 50 years of Ethnic Studies. But the road to establishing programs around addressing issues of race and ethnicity wasn't an easy one. Student strikes, student activism, and student labor became the catalyst for the Ethnic Studies movement in higher education.
Edmund Fong, chair of Ethnic Studies at the University of Utah, discusses the conception of Ethnic studies nationally and the hopes for its future at the U.
Could you give me a little background on the history of Ethnic Studies at a national level?
In the United States, the field of Ethnic Studies evolved out of the Civil Rights Movement and protests over the Vietnam War. At San Francisco State University in 1968, students with the Black Student Union, Latin American Students Organization, Asian American Political Alliance, Pilipino American Collegiate Endeavor, and Native American Students Union joined together into the Third World Liberation Front and launched the nation's longest student strike in American history, calling for the creation of a "School of Ethnic Studies." Over the course of the winter of 1968-69 and spreading to UC Berkeley as well, the student coalitions achieved the creation of the first Ethnic Studies Department nationally at UC Berkeley on March 7, 1969 followed by the nation's first College of Ethnic Studies at San Francisco State on March 20, 1969. Since then, Ethnic Studies departments have continued to spread and evolve across the country providing critical insight, knowledge and scholarship into the experiences and structures of power that shape communities of color both nationally and globally.
Meanwhile, how did this play out at the U?
At the University of Utah, the first programs encompassing Black Studies, Chicano/a Studies and Native American Studies began coalescing in 1968 as separate entities. In 1973, the Ethnic Studies Program was officially established on an interdisciplinary/interdepartmental basis with separate programs for Black, Chicano/a, and Native American Studies. The Ethnic Studies Program began offering a minor degree in 1982 and in order to continue to grow and raise its visibility, the Ethnic Studies Program in 1983 was moved under the supervision of the Office for Equity and Diversity. An Asian Pacific American Studies program was added in 1989, an Ethnic Studies major degree was approved in 2011, and in 2016, the Ethnic Studies Program became the Division of Ethnic Studies now housed within the newly created School for Cultural and Social Transformation. These changes have continued to reflect student driven needs and the dedicated labor over decades of community partners, staff and faculty at the U.
While the Ethnic Studies Program and now the Division of Ethnic Studies at the U did not arise out of student protests, we honor the 50th anniversary of these landmark events that provided crucial momentum and emphatically stamped the student and community-centered spirit of Ethnic Studies as a field.
So, what's unique about the Ethnic Studies program/department at the U today?
We are the only degree and tenure-granting Ethnic Studies Division in the intermountain west, giving us a newly gained national prominence across the country. Whereas other Ethnic Studies departments and programs have faced political and institutional challenges, the Ethnic Studies Division is experiencing a renaissance, thanks to the support of University Administration and a felt commitment to serve and represent the growing diversity of the state and on-campus. Our expertise as a field lies in forging critical awareness and knowledge of racial and ethnic differences and how these have shaped the landscapes we live in. We hope to equip our students with the ability to be lifelong learners and leaders wherever group differences, including other significant intersecting vectors of difference, vitally shape the landscapes they inhabit. We hope to provide transformative experiences for our students, to enable them to be worldly and wise, so they in turn can transform the world towards a more just and equitable future. From building a sustainable environment to crafting policies that shape communities to elevating the understanding of the human condition, our majors have a unique perspective to contribute to their future endeavors.
Tell me about your theme and why it was chosen.
Our theme for our celebration is "Insurgent Knowledge: 50 years of Ethnic Studies." We chose the theme "Insurgent Knowledge" to foreground the driving spirit of Ethnic Studies as a field. The field gained national prominence out of student-driven needs and demands in response to an academia that had chronically marginalized the role of race in constructing the world we inhabit and was institutionally, not very representative of their experiences. The knowledge they called for was therefore insurgent, arising in revolt against a traditional establishment. We foreground this theme in multiple ways, not just because we still inhabit a world structured by injustice and inequity, but also because we take to heart that Ethnic Studies as a field must always critically question its own established orthodoxies, remain critically aware of its own assumptions, especially as they come to marginalize other important dynamics and experiences. We must be alive to our own insurgencies from within, that is the driving spirit we honor in our celebration.
How do you envision Ethnic Studies evolving in the future? What's the hope?
Now that we are housed within the School for Cultural and Social Transformation, this offers Ethnic Studies new dynamic synergies that can take our students to another level of transformative experiences and intersectional knowledge. We have been blessed with a whole new generation of leading scholars, scholars who can forge connections between Ethnic Studies and some of the most pressing and vital issues of the day, from migration and human trafficking, to sustainable practices and workers movements around the world, to the unacknowledged wisdom of community experiences. Alongside our existing faculty, we all feel the wind behind our back and the inspiration to take flight in new directions. We hope to globalize our curriculum, to offer robust internships with community partners who can help our students imagine transformative praxis in new ways, and develop our own graduate program so that the Division of Ethnic Studies at the U is seen as a leading program nationally. The School itself is a wonderful cauldron of ferment and imagination and we are proud to be partners with the developing Pacific Island Studies Initiative, with Disability Studies, and with Gender Studies.


That's Scott Grimbleby, Blackhouse's Managing Director, talking about the revamp that the restaurant has been undergoing for the past fortnight, while closed to the public.
As well as keeping its architectural personality, it's also added to it, with a brand new extension - an all-weather conservatory with views of the newly revamped Bond Court to the restaurant's north side, adding space for twenty extra guests.
The menu has undergone similar refinement, keeping upmarket grill house favourites led by steak and seafood. Each table will be given the "Book of Beef" - a guide on how to pick the right steak for you from their selection of classic cuts, as well as more contemporary and premium options like English Galician (15+ year dairy cows, all the rage in North Spain babes), and Wagyu.
All steaks are aged for a minimum of 28 days, before given 24 hours to rest before cooking. A bit of dinner theatre will come courtesy of the new "Butchers Block", where steaks are weighed and cut at the table.
That's the turf covered, but Blackhouse will also be looking to fill a gap in the market for a truly great seafood restaurant in Leeds by putting an emphasis on the "surf" side of the menu, sourcing high quality seafood and shellfish for dishes like seared sashimi tuna, and whole baked seabass.


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Китайската централна телевизия (, също , съкращава се CCTV; () е основната телевизия на територията на континентален Китай.

История

1958 – 1995 години
Първото излъчване на CCTV се е състояло на 2 септември 1958 г. под названието Пекинска телевизия, след експериментално излъчване от 1 май 1958 г. През 1973 г. е пусната II програма. Названието е променено на CCTV на 1 май 1978 га. На 1 януари 1986 г. тръгва III програма. На 1 октомври 1992 г. чрез спътникова телевизия по всички направления за чужбина е пусната IV (Международна) програма. През 1994 г. чрез кабелна телевизия тръгват V, VI, VII и VIII програми.

След 1995 г.
През 1995 г. ТВ каналите са преименувани на CCTV News and Comprehersion Channel, CCTV Economic and Comprehersion Channel, CCTV Opera and Music Channel, CCTV International Channel, CCTV Movie Channel, CCTV Sports Channel, CCTV Literature Channel, от 2000 г. носят вече съвременните си названия. През 2008 г. е открито новото седалище на CCTV (построено по проект на Рем Колхас).

Канали

Основни телевизионни канали
 CCTV-1 – универсален канал
 CCTV-2 – финансов (до 24 август 2009 г. – "Икономика и живот")
 CCTV-3 – изкуство и развлечения

Каналите са достъпни чрез ефирна (цифрова (DVB-T), преди – аналогова (PAL)), кабелна и спътникова телевизия.

Международни телевизионни канали
 CCTV-4 – международен (на китайски)
 CGTN (CCTV News) – международен новинарски (на английски език)
 CCTV-9 (CCTV-9 Documentary) – международен документален (има две версии, на китайски и на английски езици)
 CCTV-E – международен (на испански)
 CCTV-F – международен
 CCTV-العربية – международен (на арабски)
 CCTV-Русский – международен
 CCTV-3 (CCTV-Entertainment)] – общ развлекателен (на китайски)
 CCTV-14 (CCTV-Children) – детски (на китайски)
 CCTV-11 (CCTV-Opera) – опера (на китайски)

Достъпни са чрез спътникова телевизия, Интернет и чрез мобилното приложение SPB TV China.

Специализирани телевизионни канали
 CCTV-5 – спорт
 CCTV-6 – кино
 CCTV-7 – военен и селскостопански
 CCTV-8 – сериали
 CCTV-10 – наука и образование
 CCTV-11 – китайска опера
 CCTV-12 – юридически
 CCTV-13 – новини
 CCTV-14 – детски
 CCTV-15 – музикален
 CCTV-HD

Източници

Външни препратки

 Онлайн транслация на CCTV
 CCTV-Русский
 Пряко предаване на CCTV на руски език
 CCTV-News
 Кулата на Централната телевизия на Китай

Телевизионни канали на китайски език
Телевизия в Китай

redpajama_set_name: RedPajamaWikipedia


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2014 ABIE Award Winner to Chair Georgia Tech's School of Interactive Computing
Dr. Ayanna Howard, a professor and the Linda J. and Mark C. Smith Endowed Chair in Bioengineering in the School of Electrical and Computer Engineering at the Georgia Institute of Technology, has a new title to add to her already impressive career. The Georgia Tech College of Computing announced that Ayanna would be its new chair for its School of Interactive Computing.
"I am thrilled for the opportunity to work with the amazing faculty, staff, and students within the School of Interactive Computing," Ayanna said, adding that she looks forward to "continuing to pursue research and innovation that addresses real challenges facing our world today."
Ayanna has taught, mentored, and encouraged countless underrepresented students in engineering and science throughout her academic career. In 2013, she founded Zyrobotics, an award-winning educational technology company that makes STEM learning accessible to all children. For her contributions, Ayanna received the 2014 A. Richard Newton Educator ABIE Award, and was asked to give a keynote speech about her work at this year's Grace Hopper Celebration (GHC 17).
Congratulations, Ayanna, on your new role! Read the full Georgia Tech News Center article here.
AnitaB.org Mentions
AnitaB.org brings women in computing together to uncover new ideas.
AnitaB.org Policy Issues and Goals
Support The Building Blocks of STEM Act and Engage Girls Early
AnitaB.org is Moving to a New Global Tech Center Headquarters Location

redpajama_set_name: RedPajamaCommonCrawl


It's not often that a customizable makeup product comes along, but when it does, we roll up our sleeves and dig in. Here, watch as we create totally new lipstick shades with the recently debuted Anastasia Beverly Hills Lip Palette. You've already seen it all around Instagram, and we're pretty sure it will become a staple in every beauty junkie's makeup stash.


The init program is a user-space program like any other program on the Linux system, and you'll find it in /sbin along with many of the other system binaries. Its main purpose is to start and stop the essential service processes on the system, but newer versions have more responsibilities.
A traditional sequenced init (Sys V, usually pronounced "sys-five"). Red Hat Enterprise Linux and several other distributions use this version.
The emerging standard for init. Many distributions have moved to systemd, and most that have not yet done so are planning to move to it.
The init on Ubuntu installations. However, as of this writing, Ubuntu has also planned to migrate to systemd.
There are many different implementations of init because System V init and other older versions relied on a sequence that performed only one startup task at a time. Under this scheme, it is relatively easy to resolve dependencies. However, performance isn't terribly good, because two parts of the boot sequence cannot normally run at once. Another limitation is that you can only start a fixed set of services as defined by the boot sequence: When you plug in new hardware or need a service that isn't already running, there is no standardized way to coordinate the new components with init.
systemd is goal oriented. You define a target that you want to achieve, along with its dependencies, and when you want to reach the target. systemd satisfies the dependencies and resolves the target. systemd can also defer the start of a service until it is absolutely needed.
Upstart is reactionary. It receives events and, based on those events, runs jobs that can in turn produce more events, causing Upstart to run more jobs, and so on.
The systemd and Upstart init systems also offer a more advanced way to start and track services. In traditional init systems, service daemons are expected to start themselves from scripts. A script runs a daemon program, which detaches itself from the script and runs autonomously. To find the PID of a service daemon, you need to use ps or some other mechanism specific to the service. In contrast, Upstart and systemd can manage individual service daemons from the beginning, giving the user more power and insight into exactly what is running on the system.
Because the new init systems are not script-centric, configuring services for them also tends to be easier. In particular, System V init scripts tend to contain many similar commands designed to start, stop, and restart services. You don't need all of this redundancy with systemd and Upstart, which allow you to concentrate on the services themselves, rather than their scripts.
Finally, systemd and Upstart both offer some level of on-demand services. Rather than trying to start all the services that may be necessary at boot time (as the System V init would do), they start some services only when needed. This idea is not really new; this was done with the traditional inetd daemon, but the new implementations are more sophisticated.
Both systemd and Upstart offer some System V backward compatibility. For example, both support the concept of runlevels.


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SportsHigh SchoolBoys Basketball
Pandolfi, Stony Brook try valiantly in Southeast Regional loss
Stony Brook's Tim Pandolfi is surrounded by Blind Brook defenders. (March 12, 2010) Photo Credit: Photo by
By BOB HERZOG bob.herzog@newsday.com Updated March 12, 2010 11:26 PM
PLEASANTVILLE, N.Y. - The notes of Aretha Franklin's classic "Respect" had barely faded to echoes after a timeout when Blind Brook's Mike Tomasula dribbled, turned and nailed a fadeaway jumper that gave his team an eight-point lead with 2:48 remaining. As he raced back on defense, Tomasula punched the air fiercely, an exclamation point of a gesture that said: "That's how I spell respect!"
Tomasula's dagger, and his tough, hanging bank shot moments earlier, highlighted a 12-0 run that gave Blind Brook an insurmountable lead. The Trojans, from Rye Brook in Westchester, posted a 47-35 victory over Long Island champion Stony Brook Friday night in the Southeast Regional Class C boys basketball final at Goldstein Center at Pace University in Westchester.
"The kid was a little bullet and that shot was a back-breaker," Stony Brook coach Mike Hickey said. "It really hurt us. It was a dramatic moment. We had some set plays to hopefully get back in it."
SEE PHOTOS High school sports -- March
Instead, the Bears (14-5) were in the midst of a fourth-quarter scoring drought that lasted 6 minutes, 20 seconds, and they were outscored 16-4 in that final period.
Tim Pandolfi, Stony Brook's leading scorer, had given his team a 33-31 lead with a jumper off a screen to start the quarter. But neither he nor his teammates scored again until Pandolfi sank two free throws with 1:20 left. By then it was 43-33.
"They did a good job taking Tim away," Hickey said. "He's our top gun and it was challenging for him to get his shots off."
Tomasula - who scored 16 points, 10 in the fourth quarter - gave Blind Brook a 29-21 lead in the third quarter, but Stony Brook fought back. With Pandolfi being harassed, freshman point guard Marko Masakayan stepped up with consecutive three-pointers to help tie the score at 29.
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But the Bears didn't have much offense left for the final eight minutes. "It wasn't that we turned the ball over," Hickey said. "We just didn't knock down shots."
Pandolfi scored 15 points and Logan Vimont had nine points and seven rebounds for a team that won its first-ever Long Island championship. "This is the farthest we've ever been," Hickey said of reaching the regional final. "Glens Falls would've been a big deal for us."
That's where Blind Brook (16-7) is headed for a state semifinal on Friday - and where Vimont, a senior, very much wanted to go. He clearly was forlorn as he shuffled out of the locker room after commiserating with his teammates.
"I know we've had a successful season, but I'm not thinking about that," he said softly. "I'm kind of sad right now. We were expecting to go places this year, so this is definitely disappointing."
For the coach, too. "This was a special group of kids. I feel bad for them," said Hickey, in his 22nd season. The Bears got a little respect on Long Island, but they wanted to find out what it means to go upstate.
By BOB HERZOG bob.herzog@newsday.com
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I had a great time capturing Elise and James' incredible wedding day in San Francisco! We started at Elise's childhood home (and got to play with her family's Shiba Inu Yoshi!) before we went to Casa de la Vista on Treasure Island. We had an incredible view of the SF skyline during the day and in the evening for an incredible night shot. Thank you to the beautiful couple for having me there to capture your gorgeous wedding!
To view the images from their guestbook, please click here.


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FIFA Ranking: Super Eagles Drop By One Spot To 32nd Position
Nigerian Super Eagles
Reports from the sporting sphere have revealed that the Nigerian Super Eagles have dropped again by one spot and they are now to be ranked 32nd in the world in the October world ranking by FIFA which is the global football governing body.
In the recent ranking table which had been released on Thursday, the Nigerian senior men's national team had also garnered up to 1498.47 points in September as against the 1504.7 which had been garnered in August.
Read Also: FIFA Ranking: Super Eagles Sit Tight At World`s 31st
On the continental level, Nigeria has also been placed fourth behind Senegal (world 18th), Morocco (23rd) and Tunisia (30th).
On the global scene, a total of 53 UEFA Nations League matches and 119 friendlies had been played during the last international break before the FIFA World Cup Qatar 2022 which would be kicking off on the 20th of November.
Brazil have also been placed first as Ranking leaders, which is enough to boost their confidence in the bid to win a sixth world title and Belgium who had also lost to eighth-placed Netherlands in the Nations League are second, after dropping a step, and Argentina in third place complete the podium.
Just behind them also lie the reigning world champions France in fourth place who are also followed by England in fifth place. The only change in the top 10 saw Italy in sixth place leapfrogging Spain who are now seventh.
In another related report, after a couple of weeks, the Canada football players have finally ended their strike to continue their preparations for the 2022 FIFA World Cup but warned "questions have yet to be answered and actions have yet to be taken".
The team, who qualified for the World Cup finals for the first time since 1986, had taken action in a dispute over Qatar 2022 prize money.
As a friendly against Panama had to be called off, the country's football ruling body reacted. Canada Soccer responded to reports players would receive only 10 per cent of the pot it received from FIFA.
Africa Daily News, New York
Nigerian Super Eagles, sporting sphere
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We also believe feline onychectomy should be performed only with the medically appropriate use of anesthetics and analgesics and adherence to careful surgical and post-surgical protocols. If you are shopping around for a competitive price on this procedure, be sure to question the type of anesthetic used, the type of pain management provided, and the monitoring equipment and procedures followed. All of our surgery patients have IV catheters placed and receive IV fluids. We use several monitoring devices during your pet's procedure. A veterinary technician continually assesses your pet's vital signs during the procedure.
Your pet's safety and comfort are our primary concerns when performing a declaw. We use advanced pain management techniques in conjunction with anesthesia to make sure your pet is as comfortable as possible during the procedure and after they are discharged. Our declaw patients receive injectable pain medications during the procedure and injectable or oral pain medications after the procedure. If needed, cats will go home with an oral pain medication. We perform nerve blocks of the feet that provide additional pain relief immediately after the surgery. Our declaw patients stay with us for two nights so that we can be sure they are quiet and comfortable. It is very common to see these kitties pawing playfully through the kennel door following this surgery.


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Home » Fashion » Mike Tindall doesn't follow Meghan Markle and Prince Harry or Kate Middleton and Prince William on his newly opened Instagram account – The Sun
Mike Tindall doesn't follow Meghan Markle and Prince Harry or Kate Middleton and Prince William on his newly opened Instagram account – The Sun
10/10/2019 Fashion Comments Off on Mike Tindall doesn't follow Meghan Markle and Prince Harry or Kate Middleton and Prince William on his newly opened Instagram account – The Sun
MIKE Tindall became the latest member of the royal family to join social media when he launched his own Instagram account @mike_tindall12 last month.
But while the rugby star, 40, is already following 126 accounts, royal fans may be surprised to hear that the Prince William and Kate Middleton nor Prince Harry and Meghan Markle are not among those.
The dad-of-two doesn't not follow the official Sussexroyal nor Kensingtonroyal accounts.
Former rugby union star Mike is currently following famous faces who he has brushed shoulders with at high-profile events, such as Ant and Dec and former Westlife singer Brian McFadden.
Equally neither the Cambridges nor the Sussexes follow Zara's husband.
In fact the Duke and Duchess of Sussex follow just 17 accounts belonging to their charities.
The Tindalls famously prefer to keep their family out of the spotlight and Hello! suggests that this could be the reason he has chosen not to follow Zara's cousins.
The down-to-earth dad joined Instagram at the end of September, following Princess Eugenie, Sarah Ferguson and Prince Andrew opening accounts.
One of the first photos he has shared shows Zar, 38,a taking part in a clay shooting event to raise money for wildlife conservation charity Tusk.
Dedicated husband Mike added the caption: "Great day clay shooting for @tusk_org supported by @landrover_uk. Finished up 3rd but it was a lot of fun!!"
Other shots include him playing golf, pictures with his friends and a shot thanking The Stafford Hotel in London for his visit.
Currently there are no pictures of his adorable children, Mia Grace, five, and Lena Elizabeth, one.
He currently boasts almost 3,000 followers.
Eugenie and Beatrice's parents Sarah Ferguson and Prince Andrew have their own accounts, with 242,000 and 219,000 followers respectively.
Meghan Markle deleted her personal Instagram account when she started dating Prince Harry, but their official SussexRoyal account has over 9.6million followers.
This follows just behind Kate Middleton and Prince William's KensingtonRoyal account which has 10.1million fans.
Zara, the daughter of Princess Anne and Mark Phillips, married to Mike in 2011 and they have been dubbed the most "down to earth" royals in the family.
In other royal news, Sarah Ferguson has admitted to having Botox, two types of facelift and vitamin injections in a bid to stay youthful ahead of her 60th birthday.
And Meghan and Kate's "powerful and brilliant" mental health awareness ad is praised by fans.
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Queen Lauren London Salutes Her Fallen King
April 17, 2019 April 17, 2019 Wilfred Kanu Jr.ROMANCE
I've always appreciated Lauren London as the right type of wifey. At a time in the world when feminazis have hijacked the masculine energy with a household, Lauren referred to Nipsey Hussle as her shield and protector. She said he made her feel like a woman. Now that is powerful! I love this woman because she's strong and bold and she's the embodiment of everything feminine in a real woman and a queen.
If your woman does not feel like this about you, bruh, you ain't blessed. Lauren London – "Ermias, I'm in bed with you while you're sleeping and I wanted to tell u something. I want you to know I feel real Joy in my heart when I'm around you. I feel safe around you. Protected. Like a shield over me when you're around. I am totally myself with you (which is prob why I'm annoying) because I don't wear a cool mask anymore lol."
I want you to know I feel real Joy in my heart when I'm around you. I feel safe around you. Protected. "
London continued, "You've made me into more of a woman. You've given me an opportunity to really love a man. You've been with me while I've been sick through my fears. You have encouraged me and inspired me to reach higher. I've learned so much more about myself with you. You've been my turn up and my church. I wouldn't want to go thru this journey with anyone but you. I look up to you in a lot of ways and strive to educate myself more like you have. And when we're at odds…. I feel defeated and sad, knowing we are so much better than that."*
Did Feminism Contribute to the Perpetual Destruction of Ancient Egyptian
To understand the History Behind the Worldwide Victimization that is Easily Exploited in Women


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Dieter Helmut Stolz (* 20. September 1916 in Karlsruhe; † 17. November 1999 in Salem-Neufrach) war ein deutscher Germanist und Kulturreferent.

Leben
Stolz wurde als Sohn des Hauptschriftleiters Ernst Stolz und seiner Gattin Elisabeth geboren und studierte in Freiburg i. Br. und München Germanistik, Geschichte, Kunst- und Theaterwissenschaft. 1942 wurde er an der Universität München bei Hans-Heinrich Borcherdt mit einer Untersuchung über Rudolf G. Binding und seine Lyrik promoviert. Später schrieb er für die NDB den Artikel über Rudolf G. Binding. Nach kurzen Berufsjahren in München als Assistent am Institut für Theatergeschichte kam er Anfang 1944 an den Bodensee, wo er zunächst als Lehrer in Salem, später als Journalist wirkte. Von 1959 bis 1966 war er Kulturreferent von Überlingen. Bei der Verleihung des Bodensee-Literaturpreises an Jacob Picard hielt er die Laudatio. Er gehörte dem Vorstand des Vereins für Geschichte des Bodensees und seiner Umgebung an. Von 1966 bis 1978 war er Kulturreferent von Lüdenscheid. 1978 zog er wieder an den Bodensee nach Unteruhldingen. In Überlingen arbeitete er mit Siegfried Lauterwasser zusammen.

Schriften
 Rudolf G. Binding und seine Lyrik. Schloss Birkeneck 1942 (= Dissertation).
 Überlingen. Ein Fotobuch. Lindau 1952.

 Handschriften der Überlinger Leopold-Sophien-Bibliothek. In: Bodensee-Hefte 11, 1960, 213–217.
 500 Jahre Reichlin-Meldeggsches Patrizierhaus in Überlingen, in: Schriften des Vereins für Geschichte des Bodensees und seiner Umgebung, 80. Jg. 1962, S. 40–51
 Illustrierte Kräuter- und Medizinbücher des 15.-17. Jahrhunderts. Handschriften und Druckwerke aus dem Besitz der Leopold-Sophien Bibliothek Überlingen. Sonderausstellg Mai/Juni 1964. Überlingen 1964
 Lüdenscheid. Die 700-jährige Bergstadt im Sauerland. Lüdenscheid 1965.
 Überlinger Inkunabelkatalog. Katalog der Inkunabeln der Leopold-Sophien-Bibliothek Überlingen. Konstanz 1966 (Nachdruck Allensbach 1970)
 Geliebtes Überlingen. Ein Gang durch Geschichte und Kultur der Stadt am Bodensee. Allensbach 1971. 2. Auflage Konstanz 1981.

Literatur
 Guntram Brummer: Nachruf in: Schriften des Vereins für Geschichte des Bodensees und seiner Umgebung, 118. Jg. 2000, S. V–VII (Digitalisat)

Einzelnachweise

Germanist
Landeshistoriker (Baden-Württemberg)
Deutscher
Geboren 1916
Gestorben 1999
Mann


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text:
\section{Introduction}
\label{sec:intro}
Due to the existence of many powerful theoretical methods for one-dimensional systems such as bosonization,\cite{giamarchi}
the density matrix renormalization group,\cite{schollwoeck05,schollwoeck11} or approaches that
exploit integrability,\cite{kluemper-review} many properties of strongly correlated one-dimensional
systems are well studied. A paradigmatic model is the spin-1/2 $XXZ$ chain which maps to interacting
spinless fermions via the Jordan-Wigner transformation.\cite{jordan28} While  ground-state and
thermodynamic properties (see, e.g., Refs.~\onlinecite{eggert94,kluemper00}) as well as many static and dynamical response functions (see, e.g., Refs.~\onlinecite{klauser11,pereira06}) are very well understood,
a complete theory of transport in this model still poses a formidable challenge to theorists.
A question that has attracted considerable attention for a long time is whether spin transport at finite temperature is
ballistic or diffusive and whether or  not ballistic transport properties are
related to integrability through the existence of non-trivial local conservation laws.\cite{zotos97,castella95}
Moreover, weakly violated conservation laws can also cause anomalous transport properties with long relaxation rates in one-dimensional systems.\cite{rosch00,jung06}
For the most part, such questions have been studied in the framework of linear response theory (see Refs.~\onlinecite{zotos-review,hm07} and references therein),
yet more recent work has also addressed the non-equilibrium regime (see, e.g., Refs.~\onlinecite{gobert05,prosen09,langer09,benenti09,langer11,jesenko11,znidaric11,znidaric11a,karrasch12a}).
Spin-transport in different experimental realizations of
quasi one-dimensional spin systems has been probed indirectly by
NMR\cite{takigawa_dynamics_1996,thurber_^17o_2001,pratt_low-temperature_2006}
and $\mu$-SR\cite{master_low_2012}  experiments. Yet, there is no consistent interpretation
of these various experiments
with regard to the question of ballistic or diffusive spin dynamics.
The latest results for
SrCuO$_2$, though, are consistent with  ballistic
dynamics at elevated temperatures.\cite{master_low_2012}

Here we revisit the problem of finite-temperature spin transport in the spin-1/2 $XXZ$ chain by using
two complementary methods, exact diagonalization and the time-dependent density matrix renormalization group.\cite{vidal04,white04,daley04}
The Hamiltonian is given by:
\begin{equation}
H = J_H \sum_{i} \lbrack S^x_iS^x_{i+1} + S^y_iS^y_{i+1} + \Delta S^z_iS^z_{i+1}\rbrack,
\label{eq:ham}
\end{equation}
where $S^{\mu}_i$, $\mu=x,y,z$, are the components of a spin-1/2 operator acting on site $i$ of
a chain of length $L$ (boundary conditions will be specified later). $\Delta$ parameterizes the
exchange anisotropy, $J_H$ sets the energy scale and will be set to unity hereafter ($\hbar=1$).
The model has a critical gapless phase for $|\Delta| \leq 1$ and  gapped  phases
with antiferromagnetic order and ferromagnetic order for $\Delta>1$ and $\Delta<-1$, respectively.\cite{kolezhuk-review}
We will focus on the gapless phase $|\Delta| \leq 1$ and study spin transport in the linear response regime.

Within linear response, one decomposes the real part of the spin conductivity $\sigma(\omega)$ into
a singular, zero-frequency part weighted with the so-called Drude weight $D$ and a regular contribution at finite frequencies, $\sigma_\tn{reg}(\omega)$:
\begin{equation}
\tn{Re } \sigma(\omega) = 2\pi D \delta(\omega) + \sigma_\tn{reg}(\omega)\,.
\end{equation}
Note that the present notation for $D$ differs from the one of Ref.~\onlinecite{hm03} by a factor of $2\pi$. We define transport at finite temperatures to be ballistic if $D(T)>0$ and our work focusses on the dependence of $D$ on temperature and exchange anisotropy $\Delta$.
A regular part with a nonzero contribution to the total weight $I_0 =\int d\omega\, \tn{Re } \sigma(\omega)$
is present for $\Delta \not=0$ and $|\Delta|<\infty$. Its precise low-frequency behavior determines whether
this regular channel is diffusive or not (see, e.g., Refs.~\onlinecite{naef98,prelovsek04,sirker09,sirker11,grossjohann10,steinigeweg09,steinigeweg12,herbrych12}).
More recently, the momentum dependence of current response functions\cite{steinigeweg12} as well as the transverse component of the spin current correlations\cite{steinigeweg11}
have also been investigated.

For the Drude weight, most studies agree that it vanishes in the massive regime.\cite{zotos96,peres99,hm03,prelovsek04,sirker11,sachdev}
At $\Delta=0$, $D$ is finite for any temperature since the model maps onto non-interacting fermions.
For $T=0$, $D$ can be obtained exactly via Bethe ansatz.\cite{shastry90}
Very involved generalizations of the Bethe ansatz to finite temperatures\cite{zotos99,benz05} consistently yield $D>0$ for all $0\leq\Delta<1$; however, the results of
Refs.~\onlinecite{zotos99,benz05} differ quantitatively regarding the temperature dependence of $D$ and the point of SU(2)-symmetric exchange, $\Delta=1$ (see the discussion in Refs.~\onlinecite{benz05,sirker09,sirker11}). Both approaches have also been argued to violate exact relations at infinite temperatures.\cite{benz05,sirker11}

For nonzero magnetization $S^z=\sum_{i=1}^L S_i^z$, a lower  bound to $D$,
\begin{equation}
0<D_{\mathrm{bound}} \leq D\,,\label{eq:bound}
\end{equation}
can be easily constructed from local conserved quantities known from the Bethe ansatz,\cite{zotos97}
exploiting the existence of the so-called Mazur inequality. A finite bound requires a non-zero overlap $\langle J Q\rangle$  of the current operator $J$ with at least one conserved quantity $Q$. The existence of such non-zero bounds has been used in Refs.~\onlinecite{zotos97,hm05,sirker09,sirker11} to study the temperature and $\Delta$-dependence
of $D$ at finite magnetizations.
For $S^z=0$, however, the overlap of all local conserved  quantities known from the Bethe ansatz solution with the current operator vanishes for symmetry reasons.\cite{zotos97} Only recently, a {\it non-zero} bound $D_{\mathrm{bound}}>0$ was derived by Prosen for the case of vanishing total magnetization $S^z=0$ and $0<\Delta<1$.\cite{prosen11} This bound exploits the existence of a quasi-local conserved quantity that has a finite overlap with $J$, which can be viewed as the  formal reason as to why $D(T)$ is finite (see also Ref.~\onlinecite{ilievski12} for an extended discussion).
It remains unclear whether or not this conserved
quantity is related to integrability and whether the bound presented in Ref.~\onlinecite{prosen11} is exhaustive [equality in Eq.~\eqref{eq:bound}] at all $0<\Delta<1$.
Despite this great progress in understanding why $D(T)$ is nonzero in this model, a result that previously was mostly based on numerical simulations,\cite{zotos96,narozhny98,hm03,hm07,heidarian07,herbrych11,karrasch12} there are still relevant open questions. First, at $\Delta=1$, there is no agreement as to whether or not $D$ is finite. Second, the temperature dependence of $D(T)$ for $|\Delta|<1$, albeit studied in previous work,\cite{zotos99,benz05,fujimoto03,alvarez02,hm03,herbrych11,heidarian07,karrasch12}
is not fully understood yet and is closely related to the question of which fraction of the total weight $I_0$ is in the Drude weight compared to finite-frequency
contributions.\cite{sirker09,sirker11,herbrych12} Finally, when evaluating expressions for $D$ with exact diagonalization, one can either elect to work
in a grand-canonical picture (i.e., averaging over all subspaces with a given total $S^z$) or in the canonical ensemble (i.e., only one sector with a fixed
$S^z$ is taken into account). While one would, on general grounds,  expect that in the thermodynamic limit both approaches should yield the same result,
a vastly  different behavior can emerge on finite systems.\cite{herbrych11,hm03} This calls for a more detailed investigation.

The first method that we employ  is the time-dependent density matrix renormalization group for finite temperatures. Various approaches for using tDMRG at finite temperatures
have been suggested and pursued in the literature.\cite{sirker05,barthel09,white09,feiguin05,verstraete04,karrasch12,barthel13a,barthel13b}
The main restriction of this method, which can otherwise provide highly accurate results, is the maximally accessible time scale
due to the entanglement encoded in the time-evolved wave-function (see Ref.~\onlinecite{schollwoeck11} for a discussion).
Here, we use the purification method originally proposed in Ref.~\onlinecite{verstraete04} complemented by a {\it disentangler} that allows one to go
to longer times than previously possible.\cite{karrasch12} In a nutshell, the purification approach relies on embedding the actual physical system for which one seeks to know
finite-temperature properties into some environment (which in our case is simply a copy of the physical system). One can then show that a pure-state time-evolution of the full system, which is amenable to tDMRG, yields the
thermal statistical operator for the system after tracing out the environment's degrees of freedom.
An advantage of this tDMRG approach is that the results for the accessible time-scales are virtually in the
thermodynamic limit. In Ref.~\onlinecite{karrasch12}, this method was used to extract the Drude weight
of the spin-1/2 $XXZ$ chain from the time dependence of current-current autocorrelation functions. The results of Ref.~\onlinecite{karrasch12}
confirm the prevailing picture that $D(T)>0$ for $|\Delta|<1$ while for $\Delta =1$, the accessible time scales are too short to arrive
at definite conclusions. Here, we provide a more detailed error analysis of this method and we present extensive results for the
temperature-dependence of $D(T)$ for $|\Delta| <1$, in particular including  $\Delta <0$. It was recently suggested\cite{barthel13a,barthel13b} to rewrite a correlation function as $\langle A(t)A\rangle=\langle A(t/2)A(-t/2)\rangle$, which allows to reach times twice as large without much additional programming effort. By exploiting this trick we can extract the Drude weight via tDMRG for significantly lower temperatures than the ones studied in Ref.~\onlinecite{karrasch12}.

Our second method is exact diagonalization which allows to compute transport coefficients for typically $L\lesssim 20$ sites.\cite{hm03,hm07,herbrych11}
The expression for the Drude weight is:\cite{shastry90,castella95}
\begin{equation}
D = \frac{1}{2L}\left\lbrack \langle  - \hat T\rangle -\frac{2}{Z_T} \sum_{m, n\atop E_m\not=E_n}
 e^{-\beta E_n}\frac{|\langle m |
J|n\rangle|^2}{E_m-E_n} \right\rbrack\,,\label{eq:drude}
\end{equation}
where $Z_T=\sum_n \mbox{exp}(-\beta E_n)$ is the partition function,  $| n\rangle$ and $E_n$ are the eigenstates and eigenvalues of $H$, $J$ is the spin-current operator,
and $\hat T= \sum_i (S_i^x S_{i+1}^x +S_i^y S_{i+1}^y)$ is the kinetic energy.
We present a detailed comparison of a grand-canonical versus a canonical evaluation of Eq.~\eqref{eq:drude}.
A canonical evaluation of Eq.~\eqref{eq:drude} was  systematically used in a recent work\cite{herbrych11} by Herbrych {\it et al.} to
compute the dependence of $D$ on temperature  and exchange anisotropy.
We argue that over a wide range of parameters ($\Delta$ and temperature $T$) the grand-canonical and canonical extrapolations
yield quantitatively similar results.
Moreover, we observe that the {\it grand-canonical} data often exhibits weaker finite-size dependencies than the canonical ones, agrees better with tDMRG data, and it seems to depend on system size in
a  more systematic way throughout the parameter range of interest, i.e.,
$|\Delta|\leq 1$. Furthermore, it has long been realized that results for $D$ from systems with an odd number of sites versus an even number of sites
exhibit a different finite-size dependence,\cite{hm03,jung07,herbrych11} which appears to be related to non-trivial finite-size effects
of the regular part $\sigma_\textnormal{reg}(\omega)$ at small frequencies.\cite{naef98,rigol08,herbrych11} The interplay of the Drude weight and finite-frequency contributions was
systematically studied by Herbrych {\it et al.}\cite{herbrych11} who show that these effects have
to be taken into account into the finite-scaling at incommensurate $\Delta$
(i.e., those values of $\Delta$ that cannot be written as $\Delta=\cos(\pi/\nu)$, $\nu$ integer).  These finite-size dependencies can be understood by considering  that the Drude weight is related to the curvature of many-body levels upon changing boundary conditions via a flux.\cite{castella95,zotos97,herbrych11} To avoid this complication, we focus on odd system sizes and commensurate values of $\Delta$.\cite{naef98} Under these three premises, grand-canonical evaluation of Eq.~\eqref{eq:drude}, consideration of odd $L$, commensurate values of $\Delta$,
we analyze the temperature dependence of $D(T)$ throughout the gapless phase and we present results for $D(T)$ extrapolated to the thermodynamic limit.
Unfortunately, there is no theory for the finite-size dependence of $D(T)$ which is the main drawback of the exact diagonalization approach.
However, for those parameters for which reliable results from ED and tDMRG are available, we report an excellent quantitative agreement between
these two methods.
To elucidate the behavior in the vicinity of $\Delta=1$, we follow $D=\cos(\pi/\nu)$ as a function of $\nu$ and observe that
$D(\nu)$ seems to approach finite values as $\nu\to\infty$ (corresponding to $\Delta=1$).

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{trick.eps}
\caption{(Color online) DMRG data for the real-time current-current correlation function of an $XXZ$  chain with $\Delta=0.707$ at intermediate temperatures $T \leq 5$. Its asymptotic value at long times  determines the Drude weight through Eq.~(\ref{eq:drude1}). The calculation was carried out for  $L=200$ and using a discarded weight $\epsilon=10^{-5}$ during the real time evolution. Dashed lines were obtained by exploiting Eq.~(\ref{eq:curr2}).}
\label{fig:trick}
\end{figure}

To summarize, the main results of our work are an extensive analysis of $D=D(T)$ using both tDMRG and ED which are in very good agreement, a discussion
of the numerical quality of the tDMRG data, and a detailed comparison of the finite-size dependencies of ED data.
Exploiting time translation invariance allows to access lower temperatures than in previous tDMRG studies.\cite{karrasch12}

The structure of this exposition is as follows. In Sec.~\ref{sec:coeffs}, we summarize the expressions for the transport coefficients that are studied
in this work. In Sec.~\ref{sec:tdmrg}, we discuss details of the tDMRG approach while Sec.~\ref{sec:ed} focusses on aspects specific to ED.
We present our main results and a discussion thereof in Sec.~\ref{sec:results} and conclude with a brief summary, contained in Sec.~\ref{sec:sum}.

\section{Definitions of transport coefficients}
\label{sec:coeffs}

\begin{figure}[t]
\includegraphics[width=0.95\linewidth]{corr1.eps}
\caption{(Color online) Current-current correlation function for various anisotropies $\Delta>0$. The calculation was carried out using $L=100$, $\epsilon=10^{-4}$ without exploiting Eq.~(\ref{eq:curr2}). }
\label{fig:corr1}
\end{figure}

Our aim is to compute the Drude weight of the integrable $XXZ$  chain defined in Eq.~\eqref{eq:ham}.
The Kubo formula for the spin conductivity reads
\begin{equation}\begin{split}
\sigma(\omega) & = \frac{1}{\omega L}\int_0^\infty e^{i\omega t} \langle [J(t),J(0)]\rangle dt \\
& = \frac{1-e^{-\omega/T}}{\omega L} \int_0^\infty e^{i\omega t} \langle J(t)J(0)\rangle dt~,
\end{split}\end{equation}
where the finite-temperature real-time current-current correlation function is given by
\begin{equation}\label{eq:corr}
\langle J(t) J(0) \rangle = \tn{Tr}\left( \rho_T\, e^{iHt} J e^{-iHt} J\right) ~,~~\rho_T = \frac{e^{-H/T}}{Z_T}~.
\end{equation}
 The current operator $J=\sum_i j_i$ is defined via a continuity equation
\begin{equation}
\partial_t S_i^z = j_{i}-j_{i+1} ~~\Rightarrow~~  j_i = i S^+_iS^-_{i+1}/2 + \tn{H.c.}~~.
\end{equation}

By inserting a full set of eigenstates $| n\rangle$ and eigenvalues $E_n$ in Eq.~\eqref{eq:corr},  the Drude weight can  be
cast  into Eq.~\eqref{eq:drude}.\cite{shastry90,castella95}
This expression can be evaluated using exact diagonalization.

The Drude weight is further related to the long-time asymptote of of the current-current correlation function $\langle J(t) J(0)\rangle$ (see Ref.~\onlinecite{zotos97}):
\begin{equation}\label{eq:drude1}
D = \lim_{t\to\infty}\lim_{L\to\infty} \frac {\textnormal{Re } \langle J(t)J(0)\rangle}{2LT}~.
\end{equation}
Using time-dependent DMRG, the current-current correlation function can be computed, thus yielding access to the
Drude weight.

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{corr2.eps}
\caption{(Color online) The same as in Fig.~\ref{fig:corr1} but for $\Delta<0$ and over the full range of  temperatures $0.05 \leq T\leq 5$. For $T\to0$ one approaches the $T=0$ Bethe ansatz result.\cite{shastry90} The calculations were carried out using $L=200$ as well as $\epsilon=10^{-5}$ for $T=\{5,2,1,0.5\}$, $\epsilon=10^{-6}$ for $T=\{0.33,0.2\}$, and $\epsilon=10^{-7}$ for $T=\{0.1,0.05\}$.}
\label{fig:corr2}
\end{figure}

\section{Density matrix renormalization group simulations}
\label{sec:tdmrg}

\subsection{Method}

In order to evaluate Eq.~(\ref{eq:corr}) by a DMRG algorithm\cite{white92,white93,schollwoeck11} that evolves a wave-function (as opposed to the time-evolution of a matrix product operator), one first needs to purify the thermal density matrix $\rho_T$ by introducing an auxiliary Hilbert space $Q$ such that  $\rho_T = \tn{Tr\,}_{Q} |\Psi_T\rangle\langle\Psi_T|$. This is analytically possible only at $T=\infty$ where $\rho_T$ factorizes. However, $|\Psi_T\rangle$ can be obtained from $|\Psi_\infty\rangle$ by applying an imaginary time evolution, $|\Psi_T\rangle=e^{-H/(2T)}|\Psi_\infty\rangle$.\cite{verstraete04,feiguin05,barthel09} The current-current correlation function of Eq.~(\ref{eq:corr}) can then be \textit{exactly} recast as
\begin{equation}\label{eq:curr1}
\langle J(t)J(0)\rangle = \frac{\langle \Psi_\infty| e^{-H/2T}e^{iHt} J e^{-iHt} J e^{-H/2T}|\Psi_\infty\rangle}{\langle\Psi_\infty| e^{-H/T}|\Psi_\infty\rangle}~,
\end{equation}
and this object is directly accessible in the time-dependent DMRG framework\cite{white04,daley04,vidal04} outlined in Ref.~\onlinecite{karrasch12}. In DMRG simulations, we use
open boundary conditions.

It is convenient to first express $|\Psi_\infty\rangle$ in terms of a matrix product state
\begin{equation}\label{eq:mps}
|\Psi_\infty\rangle = \sum_{\sigma_n} A^{\sigma_0}A^{\sigma_1}\cdots A^{\sigma_{2L-1}}|\sigma_0\sigma_1\ldots\sigma_{2L-1}\rangle~,
\end{equation}
where
\begin{align}
A^{\uparrow_\tn{even}}& = (1~~0) &
A^{\downarrow_\tn{even}}& = (0~~-1) \nonumber \\
A^{\uparrow_\tn{odd}}& = (0~~1/\sqrt{2})^T &
A^{\downarrow_\tn{odd}}& = (1/\sqrt{2}~~0)^T ~.
\end{align}
Physical (auxiliary) sites are denoted by even (odd) indices. After factorizing the evolution operators $\exp(-\lambda H)$ using a fourth-order Trotter decomposition, they can be successively applied to Eq.~(\ref{eq:mps}). At each time-step $\Delta\lambda$, two singular value decompositions are carried out to update three consecutive matrices. The matrix dimension $\chi$ is dynamically increased such that at each time step the sum of all squared discarded singular values is kept below a threshold value $\epsilon$. As mentioned above, we do not only time-evolve the physical but also the auxiliary sites (using the physical Hamiltonian but with reversed time). As outlined in Ref.~\onlinecite{karrasch12}, this is an exact modification to the DMRG algorithm (auxiliary sites are traced over, and one can thus apply an arbitrary unitary transformation to them) which leads to a significantly slower build-up of entanglement; hence, longer time scales can be reached. The tDMRG approximation to $\langle J(t)J(0)\rangle$ becomes exact in the limit of $\epsilon\to0$ and $\Delta\lambda\to0$. We ensure that both are chosen small enough and that the system size $L$ is large enough to obtain results which are converged w.r.t.~those parameters (this is discussed below).

The main cost of time-dependent DMRG simulations, both at finite and zero temperature, depends on the entanglement growth as a function of time.\cite{schollwoeck11}
For the methods used here, this problem was discussed  in Refs.~\onlinecite{barthel13b} and \onlinecite{karrasch13} which we refer the reader to for details and
examples.

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{params.eps}
\caption{(Color online) DMRG data for the current-current correlation function obtained using (a) different discarded weights $\epsilon$ during the real-time evolution and (b) different system sizes $L$ ($\nu=4$, $T=0.5$). }
\label{fig:params}
\end{figure}

In Refs.~\onlinecite{barthel13a,barthel13b} it was recently suggested to exploit time translation invariance to rewrite any correlation function as
\begin{equation}\label{eq:curr2}
\langle A(t)A(0)\rangle = \langle A(t/2)A(-t/2)\rangle~.
\end{equation}
This trick allows to access times \textit{twice as large} without much additional effort. Within the framework of purification, one needs to compute\cite{karrasch13}
\begin{equation}
e^{-iHt/2} A e^{iHt/2} e^{-H/2T}|\Psi_\infty\rangle~.
\end{equation}
It is most straightforward to calculate $\langle J(t/2)J(-t/2)\rangle$ by evaluating every term $j_i$ that contributes to $J=\sum_ij_i$ separately. Thus, the effort to obtain the current-current correlation function via $\langle J(t/2)J(-t/2)\rangle$ is larger (but not exponentially larger) than it is for $\langle J(t)J(0)\rangle$ where it is sufficient to carry out a single time evolution $e^{-iHt}j_{L/2}e^{-H/2T}|\Psi_\infty\rangle$.\cite{sirker11} We therefore mostly stick to Eq.~(\ref{eq:curr1}) and only exemplary (i.e., for a single anisotropy $\Delta=0.707$ and temperatures $T=0.25\ldots5$) exploit Eq.~(\ref{eq:curr2}).

\subsection{Real-time data}

tDMRG data for the current-current correlation function are shown in Figs.~\ref{fig:trick}-\ref{fig:d1m}. The calculation is stopped once the matrix dimension has reached values of $\chi\approx 1000-2000$. This generically allows to access time scales $t\approx20-40$ which are much larger than the intrinsic scale $t=1/J_H=1$. For antiferromagnetic anisotropies $0<\Delta<1$ and intermediate to large temperatures $T\gtrsim0.25$, $\langle J(t)J(0)\rangle$ has saturated for $t\approx40$ (see Fig.~\ref{fig:trick}); thus, the Drude weight can be obtained via Eq.~(\ref{eq:drude1}). At smaller $T$, a large diffusive contribution with a small decay rate prevents us from reaching the asymptotic regime.\cite{sirker09,sirker11} Data for the isotropic chain $\Delta=1$ are shown in Figs.~\ref{fig:corr1} and \ref{fig:d1m}; these will be discussed in Sec.~\ref{sec:gapless}.

In the ferromagnetic case $-1<\Delta < 0$ (Fig.~\ref{fig:corr2}), the current-current correlation function seems to saturate fast for any $T$. Field theory suggests that a diffusive contribution (of unknown total magnitude) with an exponentially small decay rate exists for $-1<\Delta<0$.\cite{sirker09,sirker11} There are thus two possibilities to interpret our data at small $T$: either $\langle J(t)J(0)\rangle$ saturates slowly on a large scale which does not manifest itself for times $t\lesssim20$; or the magnitude of the diffusive contribution is small. The facts  that first, we successively approach the exact Bethe ansatz result for $T\to0$ (see Fig.~\ref{fig:corr2}) and second, the observation of large ballistic contribution relative to the total weight of $\sigma(\omega)$ (compare Sec.~\ref{sec:weight}) support the latter, and in the following we will rely on  this interpretation and discuss the available
numerical data.

As mentioned above, we have to ensure that the discarded weight and the Trotter step size are chosen small enough and that the system size $L$ is chosen large enough to obtain results which are converged w.r.t.~those parameters. Typical values are $L=200$, $\Delta\lambda=0.2$, and $\epsilon=10^{-9}$ as well as $\epsilon=10^{-4}\ldots10^{-7}$ during the imaginary and real-time evolutions, respectively. The dependencies on $L$ and $\epsilon$ are illustrated in Figs.~\ref{fig:params} and \ref{fig:d1m}. The finite system size manifests itself on time scales $t\gtrsim L/v$ with $v$ being a proportionality factor which has the dimension of a velocity. This is the so-called light-cone effect in nonrelativistic systems: correlation functions $\langle A(t)B(0)\rangle$ of local operators $A$ and $B$ fall off exponentially for $x>vt$ with $x$ denoting the spatial distance between the regions on which $A$ and $B$ act.\cite{liebrobinson} Note that in our case for times $t\lesssim20$ and temperatures $T\gtrsim0.5$, the data for all $L>75$ coincides (see Fig.~\ref{fig:params}). Moreover, if $L$ is chosen too small or if $\epsilon$ is chosen too large, one generically \textit{underestimates} the Drude weight.

\begin{figure}[t]
\includegraphics[width=0.95\linewidth]{D1P.eps}
\caption{(Color online) Error analysis  as a function of various discarded weights for $\Delta=\pm1$, $L=200$ and (a) $T=\infty$, (b) $T=1$ and (c) $T=0.5$. Note that for $T=\infty$ curves at $\pm\Delta$ coincide.\cite{benz05}}
\label{fig:d1m}
\end{figure}

\section{Exact Diagonalization}
\label{sec:ed}
Our ED analysis of the Drude weight is based on an evaluation of Eq.~\eqref{eq:drude}. We use periodic boundary
conditions and we compute transport coefficients for  systems as large as $L\leq 19$.
We will make a distinction between a {\it grand-canonical} versus a {\it canonical} evaluation of Eq.~\eqref{eq:drude},
which includes the evaluation of the kinetic energy from
\begin{equation}
\langle \hat T\rangle  = \frac{1}{Z} \sum_{n} e^{-\beta E_n} \langle n | \hat T | n\rangle\,. \label{eq:T}
\end{equation}
To be specific about grand- versus canonical interpretation, the sums over eigenstates in Eqs.~\eqref{eq:drude} and \eqref{eq:T} have to
be read as:
$$
\sum_{n} \to \sum_{S^z} \sum_{E_n(S^z)}
$$
in the former case, whereas in the latter case, we fix $S^z$ to a desired value and sum over all eigenstates $E_n(S^z)$ in that
subspace only. For odd $L$, the smallest $S^z$ is $S^z=1/2$, which is non-zero (but the magnetization per sites goes to zero as $1/2L$).\cite{herbrych11}

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{ED_extN_C.eps}
\caption{
(Color online) ED data for the leading coefficient $C(L)$ of $D(T)\approx C/T$ in the high-temperature limit (see Eq.~\eqref{eq:c}).
(a) Grand-canonical and (b) canonical  data at $\Delta=0.5$, comparing data from odd $L$ to even $L$. The lines are an extrapolation in system size using
$C(L) = C + A/L + B/L^2$ using data-points with $5 \leq L \leq 19$. (c) Comparison between grand-canonical and canonical data for $C$
for odd $L$ and $\Delta=0,0.5,1$. The ED results are extrapolated to $L=\infty$ using Eq.~\eqref{eq:extra_c}.}
\label{fig:ED_extN_C}
\end{figure}

Let us first compare data obtained from chains with an {\it even} versus an {\it odd} number of sites in the example of
$\Delta=0.5$ and in the high-temperature limit.
We compute the leading coefficient of $D(T)=C/T+\mathcal{O}(T^{-2})$ in a high-temperature expansion in $1/T$ from\cite{hm03}
\begin{equation}
C=\lim_{T\to \infty} \lbrack T D(T)\rbrack\,.
\label{eq:c}
\end{equation}
The results are shown in Fig.~\ref{fig:ED_extN_C}(a) for the grand-canonical case and in Fig.~\ref{fig:ED_extN_C}(b) for the canonical one.
In the latter case, odd system sizes correspond to working with $S^z=1/2$ whereas for even system sizes, we work in the $S^z=1$ subspace (note that $S^z/L\to0$ as $L\to\infty$).\cite{herbrych11}
The figure further contains fits to the data using
\begin{equation}
C(L)= C +A/L+B /L^2\,. \label{eq:extra_c}
\end{equation}
The results for $C$ are all consistent with each other, with a somewhat larger deviation for the canonical data with $S^z=1$.
However, the coefficient $B$ is {\it larger} for chains with an even number of sites, which is particularly evident in the grand-canonical case [see Fig.~\ref{fig:ED_extN_C}(a)],
indicating that the data for odd system sizes
approaches the large-$L$ limit faster at $T\to \infty$. This behavior extends down to temperatures of $T\sim 0.5$.  In the following, we therefore
restrict our analysis to odd $L=5,7, \dots, 19$.

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{ED_extN_D.eps}
\caption{
(Color online) ED data for the Drude weight $D$ for $\Delta=0.5$.  The filled (open) symbols are the results for the grand-canonical (canonical) calculation of $D$.
The solid (dashed) lines are an extrapolation of $D$ in system-size using  a second-order polynomial in $1/L$, Eq.~\eqref{eq:d_l}, for grand-canonical (canonical) data.  }
\label{fig:ED_extN_D}
\end{figure}

Next we compare grand-canonical data to canonical data  for $C$ for $\Delta=0,0.5,1$ which is shown in Fig.~\ref{fig:ED_extN_C}(c), extrapolated
using Eq.~\eqref{eq:extra_c}.
We observe that in the high-temperature limit,  $B\approx 0$.\cite{hm03}
Generally, one would expect both the grand-canonical and the canonical data sets  to result in the exact same number as $L\to \infty$. This is consistent with our data
for $\Delta=0$. Clearly, though, the grand-canonical data exhibits {\it no} finite-size dependence at all for $\Delta=0$ in contrast
to the canonical data. Therefore, we conclude that data obtained from a canonical evaluation of Eq.~\eqref{eq:drude} approaches the large
$L$ limit {\it slower} than grand-canonical data.
At $\Delta=0.5$, the grand-canonical data and the canonical data  extrapolate to the same value. At $\Delta=1$, the grand-canonical
data still follows the simple function given in Eq.~\eqref{eq:extra_c} quite well and extrapolates to a finite value of $C(L=\infty)$ (this reproduces the results
of Refs.~\onlinecite{hm03,hm07}), whereas the canonical
data do not follow any low-order polynomial in $1/L$.
The authors of Ref.~\onlinecite{herbrych11} argue that the canonical data for $\Delta=1$ can only be interpreted in terms of $C(L=\infty)=0$.
Our point of view is different: since there is no theory for the finite-size dependence of $D$, one can only use the canonical
data at $\Delta=1$  extracted from the largest $L$ as an {\it upper bound} to the true $D$, assuming that the finite-size dependence
is monotonous. To summarize, while the grand-canonical data can be well fitted to a simple polynomial in $1/L$ of low order
for all $|\Delta| \leq 1$, it is at present unclear how to extrapolate the canonical data close to $\Delta=1$ to $L\to \infty$.

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{D_T_posDelta.eps}
\caption{
(Color online) Comparison of tDMRG and ED data (extrapolated in $L$) for the Drude weight for (a) $\Delta=0.5$, (b) $\Delta=\cos(\pi/4)$, and (c) $\Delta=\cos(\pi/5)$.
Circles are the exact $T=0$ Bethe ansatz results taken from Ref.~\onlinecite{shastry90}, the stars are the $T>0$ Bethe ansatz results from Ref.~\onlinecite{zotos99}, the dashed
line in (a) are the Bethe ansatz results from Ref.~\onlinecite{benz05}.}
\label{fig:D_T_posDelta}
\end{figure}

The main goal of our work is to obtain $D=D(T)$ from exact diagonalization by means of an extrapolation in $1/L$, in  order to compare with tDMRG data.
In Fig.~\ref{fig:ED_extN_D}, we demonstrate, for   the example of $\Delta=0.5$, that  the fitting function
\begin{equation}
D(T,L) =D(T) +A(T)/L + B(T)/L^2
\label{eq:d_l}
\end{equation}
describes the available data relatively well at {\it all} temperatures, which has previously not been appreciated in
exact diagonalization studies (Herbrych {\it et al.} also present results for $D(T)$ from such extrapolations of canonical data as a function of $T$ in Ref.~\onlinecite{herbrych11}).
However,  in the temperature regime of $0.1<T\lesssim 0.5$, the monotony behavior of $D(T,L)$ as a function of $L$ changes
dramatically, which is particularly evident by comparing data from odd to even $L$ (see the discussion and figures in Ref.~\onlinecite{hm03}), rendering this regime the most difficult one and the least reliable for finite-size extrapolations. In Ref.~\onlinecite{herbrych11}, it was observed that $D= C/T$ approximates the full $D(T)$ well down
to temperatures of $T\sim 0.5$, suggesting that it should be possible to obtain an estimate for $D(T)$ from finite-size extrapolations in the regime $0.5<T<\infty$.
As $T\to 0$, we observe $A\to 0$ (see the discussion in Ref.~\onlinecite{hm03} and references therein).
In the following, we will use Eq.~\eqref{eq:d_l} to obtain $D(T)$ for several $\Delta=\cos(\pi/\nu)$, with $\nu=3,4,\dots,25$ and at $\Delta=1$ (corresponding to $\nu\to\infty$).
Error bars in the figures are obtained from excluding either the largest or smallest system size from the fits. We have also tried other possible extrapolation functions, yet we
find that a second order polynomial in $1/L$ consistently approximates the data the best.

\section{Results and comparison of tDMRG with exact diagonalization}
\label{sec:results}
In this section, we present our main results, namely ED and tDMRG data for the temperature dependence
of $D(T)$, a comparison of canonical versus grand-canonical ED data, and we revisit the case of $\Delta=1$,
for which no exact results are available on whether $D(T)$ is finite or not.
 Note that results for $D(T)$ from an extrapolation of canonical ED data were previously presented in Ref.~\onlinecite{herbrych11} (we quantitatively agree with their data for $\Delta=0.5$),
while grand-canonical ED data for finite systems was extensively discussed in Ref.~\onlinecite{hm03} (see also further references mentioned in that work).

\subsection{Gapless regime:  $|\Delta|<1$}
\label{sec:gapless}

Figure~\ref{fig:D_T_posDelta} contains representative examples of our results for $D(T)$ for three positive values of
$\Delta=\cos(\pi/\nu)$ ($\nu=3,4,5$).
We emphasize the main observations. First, the
canonical and grand-canonical ED data agree well with each other both at low and high temperatures.
At low temperatures, the subspace with the smallest value of $S^z$ dominates the grand-canonical sum in Eq.~\eqref{eq:drude}
and since this smallest $S^z$-subspace enters in the canonical calculation of $D$, the agreement at low temperatures is
to be expected. Second, the deviations between the canonical and grand-canonical data are the largest at intermediate temperatures
$T\sim 0.5$, and increase as $\nu$ increases. Third, the agreement between the tDMRG data and the ED data is excellent, and the
tDMRG appears to be closer to the grand-canonical ED curves. In all cases, the extrapolated ED data are consistent with the exactly known zero-temperature result\cite{shastry90} (circles in Fig.~\ref{fig:D_T_posDelta}).

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{D_T_negDelta.eps}
\caption{(Color online)
Comparison between tDMRG and ED data  for (a) $\Delta=0.5$, (b) $\Delta=-0.707$ and (c) $\Delta=-0.809$.}
\label{fig:D_T_negDelta}
\end{figure}

Our grand-canonical data further agree with the available finite-temperature Bethe ansatz results from Ref.~\onlinecite{zotos99} at $T\geq 0.4$ (while the canonical data
exhibit larger deviations). Yet, upon lowering temperature, these Bethe ansatz results are systematically below the ED data and follow
a quantitatively different temperature dependence with a non-zero slope at $T=0$ (see also Ref.~\onlinecite{fujimoto03}).

Our ED data suggest a vanishing slope of $D(T)$
as $T\to 0$ at $\Delta=0.5$, in agreement with the results of a different finite-temperature Bethe ansatz calculation.\cite{benz05}
For $T>0.1$, the results by Benz {\it et al.} \cite{benz05} [dashed line in Fig.~\ref{fig:D_T_posDelta}(a)] lie systematically above
the results of all other methods and therefore put too much weight into the Drude weight, compared to finite-frequency
contributions (see also the discussion in Ref.~\onlinecite{sirker11}). In fact, for $\Delta=0.5$,  the data of Ref.~\onlinecite{benz05}
for $D(T)$ is approximately equal to the kinetic energy.

 The discrepancy between ED and Ref.~\onlinecite{zotos99} can at present not be resolved
yet may be amenable to alternative tDMRG methods for finite temperature.\cite{white09,barthel13a,barthel13b}
Our tDMRG results for $T=0.1$ at $\Delta=0.707$ (see Fig.~\ref{fig:trick})
agree better with the ED data yet the time-dependent tDMRG still exhibits a noticeable slope at the longest times reached in the simulations.
Note, though, that {\it if} the Drude weight at $\Delta=1$ is finite, then its zero-temperature slope $dD/dT$ has been predicted to be {\it positive}.\cite{benz05,fujimoto03,sirker09,hm03}

As examples for the behavior of $D(T)$ in the ferromagnetic, critical regime $-1<\Delta<0$, we present results
for $\Delta=-\cos(\pi/\nu)=-0.5,-0.707,-0.809$ ($\nu=3,4,5$) in Fig.~\ref{fig:D_T_negDelta}. In these cases, we were able to extract accurate tDMRG data down to
very low temperatures (compare the discussion of Sec.~\ref{sec:tdmrg} and the real-time data presented in Fig.~\ref{fig:params}).
The agreement between ED data on the one hand -- both canonical and grand-canonical data -- and tDMRG on the other hand is excellent, at all
temperatures considered. Small deviations occur at temperatures $T\sim 0.3$ for $\Delta=-0.809$ where the error bars of the extrapolation
of the ED data are the largest.

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{D_nu_neu.eps}
\caption{
(Color online) (a) Drude weight versus $\nu$, where $\Delta = \cos\left(\frac{\pi}{\nu}\right)$. (a), (b) Comparison of tDMRG (filled symbols; shown for $\nu\leq10$) and ED (open symbols) using grand-canonical data
in a log-log plot. Thin solid lines connecting the ED data are guides to the eyes.
(b) $C$ vs $\nu$ ($C=\lim_{T\to \infty} \lbrack T \, D(T)\rbrack$).
The thick dashed line in  (a) shows an extrapolation using $D(\nu) = A \cdot (\nu)^{-B}$ using $\nu = 3,\dots,7$.}
\label{fig:D_nu}
\end{figure}

We next study how $D(T)$ behaves as $\Delta=1$ is approached, sending $\nu$ to large values.
We compute $D(T,\nu)$ from grand-canonical ED data for various values of $\nu$ from an extrapolation of $D(T,\nu,L)$ in system size
that is carried out for each pair of $T,\nu$, along the lines discussed in Sec.~\ref{sec:ed} (see Fig.~\ref{fig:ED_extN_D}).
Thus, for each temperature $T$, we obtain a series of data points $D(T,\nu)$ as a function of $\nu$, where $\Delta\to 1$ as
$\nu\to \infty$. Examples are shown in Fig.~\ref{fig:D_nu}(a). For $\nu\leq 10$, we include tDMRG data
that is in reasonable qualitative agreement with the ED results (for $\nu > 10$,  we cannot reliably extract results for $D(T)$ from the real-time tDMRG simulations).
The figure further shows that the ED data do not follow a power-law in $\nu$ (dashed line in the figure), but rather, $D(T,\nu)$ seems to level off at finite and infinite temperature, suggesting a non-zero value
of $D(T)$ at $\Delta=1$. Based on the available real-time DMRG data for $\Delta=\pm 1$ (Figs.~\ref{fig:corr1} and \ref{fig:d1m}), we cannot unambiguously discern between a finite Drude weight at $\Delta=1$ and a current correlation function that decays on a fairly large time scale.

\subsection{Spectral weight of the Drude peak}
\label{sec:weight}
Finally, we study how much of the total weight $I_0$ of the spin conductivity is in the Drude weight, compared to finite-frequency contributions.
A similar analysis of ED data  was presented in Ref.~\onlinecite{herbrych11} using canonical ED data at $T=\infty$ exploring the dependence on $\Delta$ and $S^z$, which we here complement by
using grand-canonical data and consideration of finite temperatures $0<T<2$.

The real part of the spin conductivity obeys a sum rule:
\begin{equation}
I_0=\int d\omega\, \mbox{Re}\,\sigma(\omega)= \frac{\pi}{L} \langle -\hat T\rangle\,.
\end{equation}
We plot $2\pi D/I_0$ in Fig.~\ref{fig:ED_D_over_I} as a function of temperature for $\Delta=-0.5,0.5$ and $1$.
 These data are obtained from grand-canonical ED results plus an extrapolation
using Eq.~\eqref{eq:d_l}. The units are chosen such that the vertical axis can be read in \%, implying that $2\pi D/I_0=1$ corresponds to the absence
of any finite-frequency contributions.

\begin{figure}[t]
\includegraphics[width=0.95\linewidth,clip]{ED_D_over_I.eps}
\caption{
(Color online)
Fraction of the Drude weight $2 \pi D /I_0$ to the total spectral weight of the spin conductivity, $I_0$, obtained from ED by grand-canonical calculation of Eq.~\eqref{eq:drude}.
 $I_0 = \int \tn{Re } \sigma (\omega) d\omega$, through the f-sum rule given by\cite{shastry90} $I_0 = \frac{\pi}{L} \langle-\hat{T}\rangle$.
The extrapolation to $L\rightarrow\infty$ is done as in Fig.~\ref{fig:ED_extN_D}.   }
\label{fig:ED_D_over_I}
\end{figure}

At $\Delta=\pm 0.5$ and in the low temperature limit, practically all the weight sits in the Drude weight which then monotonously
drops to values larger than 50\% of the total weight at high temperatures (at $T=\infty$, the values for $\Delta=0.5$ and $-0.5$ should agree with each other).\footnote{$C(\Delta)=C(-\Delta)$ is strictly correct for even $L$ and in the thermodynamic limit, yet not for finite, odd $L$. Since our extrapolations include small odd $L$, we recover
$C(\Delta)=C(-\Delta)$ only approximately as $L\to \infty$.}
By all means, the contribution of the Drude weight is therefore substantial
at all temperatures.
At $\Delta=1$, the low-temperature regime is difficult to obtain from ED data due to several reasons.
It is well-known that the low-temperature behavior of thermodynamic quantities at $\Delta=1$ is strongly
influenced by the appearance of a marginally irrelevant perturbation to the effective low-energy field theory, which otherwise, in the
gapless phase, is simply a Luttinger liquid.  This cannot be captured by ED on short chains (compare the work by Laflorencie {\it et al.}, Ref.~\onlinecite{laflorencie04}),
and we thus expect the temperature dependence of the true Drude weight to deviate from our result at low temperatures $T\lesssim 0.1$.
 The exact $T=0$ result
for $2\pi D/I_0$ (circle) sits well below the ED data.\cite{hm03} Based on the available ED data, we conjecture that one possible
behavior of $D(T)$ and $2\pi D/I_0$ in the thermodynamic limit at $\Delta=1$ is a {\it maximum} at some intermediate $T\sim 0.1$ if $D(T)$ is non-zero at all.
This would imply a positive slope of $D(T)$ at zero temperature, in agreement with Refs.~\onlinecite{fujimoto03,benz05}.
The existence of the additional maximum in $D(T)$ at $T\sim 0.8$ cannot be resolved with the available system sizes and should thus
be considered as spurious.
 An intriguing observation from Fig.~\ref{fig:ED_D_over_I} for $\Delta=1$ is that
the Drude weight amounts to 80\% of the total weight at temperatures $T\sim 0.1$, which drops to less than 10\% at high temperatures.

Our results indicate that the contribution of the Drude peak is
substantial for all $\Delta>0$ and $\Delta$ sufficiently smaller than $1$,
and may even be large at low temperatures (see the Fig.~\ref{fig:ED_D_over_I} with $\Delta=0.5$).
We further suggest that our data for the temperature dependence of $2\pi D(T)/I_0$ at $\Delta=\pm0.5$ could be used to
obtain estimates on the diffusion rate $\gamma$ introduced in Refs.~\onlinecite{sirker09,sirker11} along the lines of Ref.~\onlinecite{sirker11} or for a comparison with QMC results.\cite{grossjohann10}
Finally, we observe that for the commensurate values of $\Delta=\cos(\pi/\nu)$ studied in our work, the lower bound to $D(T)$ from Prosen's work\cite{prosen11} seems to
be almost exhaustive.

\section{Summary}
\label{sec:sum}

In this paper we studied the problem of the spin Drude weight of the spin-$1/2$ $XXZ$  chain at finite temperature using the time-dependent density matrix renormalization group as well as exact diagonalization. This complements earlier works in various ways. First, we elaborated on numerical details of both methods. tDMRG yields the real-time current-current correlation function $\langle J(t)J(0)\rangle$, and $D$ can be extracted from its asymptote provided that the asymptotic time regime where $\langle J(t)J(0)\rangle$ saturates can be reached. We presented data for various discarded weights which controls the accuracy of tDMRG calculations. While the thermodynamic limit $L\to\infty$ can be accessed easily within tDMRG, exact diagonalization is bound to system sizes $L\lesssim20$ and thus requires an extrapolation to $L\to\infty$. We showed that canonical and grand-canonical ED
data are in good agreement at small $\Delta <1$. Grand-canonical data appear to have more systematic finite-size dependencies all across the gapless phase.  As a second key aspect of our work, we presented extensive data for the temperature-dependence of the Drude weight. For parameters where the asymptote of $\langle J(t)J(0)\rangle$ can be accessed by tDMRG (antiferromagnetic chains at intermediate-to-high temperatures as well as for ferromagnetic chains at any $T$), results are in perfect agreement with ED extrapolated to $L\to\infty$.
Finally, we investigated how $D(T)$ behaves in the vicinity of $\Delta=1$
by sending $\nu$ to large values ($\Delta=\cos(\pi/\nu)$). These data are consistent with $D(T)>0$ at $\Delta=
1$ (in disagreement with Refs.~\onlinecite{zotos99,herbrych11}), and a final clarification of this open question is left for  future work, exploiting, for instance,
  alternative and recently developed finite-temperature tDMRG methods.\cite{white09,barthel13a,barthel13b}

\emph{Acknowledgments} --- We thank W. Brenig, J. E. Moore, T. Prosen, and F. Verstraete for very helpful discussions and we thank A. Kl\"umper for his comments on a previous version of the manuscript and for sending us data from Ref.\onlinecite{benz05}. We gratefully  acknowledge  support from to the Deutsche Forschungsgemeinschaft through  grant-no.
KA3360-1/1 (C.K.) and through  Research unit FOR 912 (grant no. HE-5242/2-2 (J.H. and F.H.-M.)) as well as from the Nanostructured Thermoelectrics program of LBNL (C.K.).

\bibliographystyle{apsrev}

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text:
Q: Using XMLReader to parse deeply nested value quickly I am new to XMLReader and I want to extract some deeply nested nodes. I am unable to grab the values I wanted. Below I have an example of the element I am parsing, the code I am using, and what value I want. Link to xml file: http://datastore.unm.edu/schedules/current.xml
XML element:
<unmschedule version="1.0.4" pubdate="2016-10-30-13:00:02" source="UNM">
<usage>
  <guideline url="http://xmlschedule.unm.edu/docs/xml-schedule-usage-guideline.html"/>
</usage>
<lookups>
  <parts-of-term>...</parts-of-term>
  <statuses>...</statuses>
</lookups>
<semester code="201680" name="Fall 2016" index="1">
  <campus code="ABQ" name="Albuquerque/Main">
    <college code="AP" name="School of Arch. and Planning">
      <department code="ABM" name="School Architecture Planning">
        <subject code="ARCH" name="Architecture">
          <course number="109" title="Design Fundamentals">
        <catalog-description>
         Studio/lecture.
        </catalog-description>

          <text>Cancel/Reschedule to CRN 57664 04/20/2016.</text>
          <instructional-method code=""/>
          <delivery-type code="LC">Lecture</delivery-type>
          <enrollment max="18">0</enrollment>
          <waitlist max="0">0</waitlist>
          <credits>3</credits>

          <text/>
          <instructional-method code="ENH">Web Enhanced</instructional-method>
          <delivery-type code="LC">Lecture</delivery-type>

Code:
$map_url = 'http://datastore.unm.edu/schedules/current.xml';

$xml = new XMLReader;
$xml->open($map_url);

$xml->read();

while ($xml->read()) {
    if ($xml->nodeType == XMLReader::ELEMENT) {
            print $xml->semester->campus->college->department->subject->course.': ';
    } else if ($xml->nodeType == XMLReader::TEXT) {
            print $xml->semester->campus->college->department->subject->course->value.PHP_EOL;
    }
}

Nodes I want to extract:
1) In the <course> tag I want the "number" and "title" e.g. 109 and Design Fundamentals.
2) In the
 tag I want the "crn" and number e.g. 41646 and 002

redpajama_set_name: RedPajamaStackExchange


text:
<?php
namespace af\kernel\core;

use af\kernel\event\Event_Dispatcher;
use af\kernel\core\Node;
use af\kernel\core\Null_Node;
use af\kernel\core\Kernel;

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  public function construct3($name, $owner, $permission) {
    $this->name = $name;
    $this->parent = new Null_Node();
    $this->childs = array();
    $this->owner = $owner;
    $this->permission = $permission;
  }

  public function get_name() {
    return $this->name;
  }

  public function get_path() {
    $nodes = array(); $current_node = $this;
    do {
      $parent_node = $current_node->get_parent();
      array_push($nodes, $current_node);
      $current_node = $parent_node;
    }
    while (!$parent_node->is_null());

    $nodes = array_reverse($nodes);
    end($nodes);
    $last_key = key($nodes);
    $result = '';
    foreach ($nodes as $key=>$node) {
      $result .= $node->get_name();
      if ($node->get_name() != '/' && $key != $last_key)
        $result .= '/';
    }
    return $result;
  }

  public function add_child($node) {
    $child = $this->find_child($node->get_name());
    if (!$child->is_null())
      throw new Node_Is_Exist_Error('Node is already exist. name is ' . $node->get_name());
    array_push($this->childs, $node);
    $node->set_parent($this);
  }

  public function find_child($name) {
    for ($i = 0; $i < count($this->childs); $i++) {
      if ($this->childs[$i]->get_name() == $name)
        return $this->childs[$i];
    }
    return new Null_Node();
  }

  public function remove_child($name) {
    for ($i = 0; count($this->childs); $i++) {
      if ($this->childs[$i]->get_name() == $name) {
        $this->childs[$i]->set_parent(new Null_Node());
        array_splice($this->childs, $i, 1);
        break;
      }
    }
  }

  public function get_childs() {
    return $this->childs;
  }

  public function set_parent($node) {
    $this->parent = $node;
  }

  public function get_parent() {
    return $this->parent;
  }

  /**
   * 액터의 소유자 명을 설정한다.
   *
   * @param owner Owner 소유자
   */
  public function set_owner($owner) {
    $this->owner = $owner;
  }

  public function get_owner() {
    return $this->owner;
  }

  /**
   * 액터의 접근권한을 설정한다.
   *
   * @param permission Permission 접근 권한
   */
  public function set_permission($permission) {
    $this->permission = $permission;
  }

  public function get_permission() {
    return $this->permission;
  }

  public function release() {
    // 부모에서 나를 제거
    $this->parent->remove_child($this->get_name());
    // 나의 부모를 제거
    $this->set_parent(new Null_Node());
    // 내 자식들을 모두 삭제
    foreach ($this->childs as $child) {
      $child->release();
    }
    $this->childs = array();
  }

  public function update() {
    foreach ($this->childs as $child) {
      $child->update();
    }
  }

  public function is_null() {
    return false;
  }

  private $name;
  private $parent;
  private $childs;
  private $owner;
  private $permission;
}

redpajama_set_name: RedPajamaGithub


There has been much talk about Netflix these past few weeks with the stock seeing ups and downs like it hasn't in years.
The NFLX stock, along with all the other FAANG stocks, has fallen to lows unseen by the company this year, wiping out all stock gains and now heading to unknown territory.
Previous articleCould GE's Aviation Segment be Their Final Hope of a Turnaround?
How Much Is Netflix Spending on Original Content in Europe?
eerr, yeah. Netflix stock is the best buy out of the Fang stocks.
Tesla has lifted one of the biggest overhangs on the stock, with the electric-car maker reportedly producing 1,000 Model 3 cars in a day.


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text:
Sidsel Galthen Bech
Frederikke Amalie Bodil Foss
Jim Wegener Lyngvild
Hedvig Pitzner-Jørgensen (nee Ørum)
Nick MacGregor Sadolin
Camilla Sløk
NobleCircles Genealogy © Haceldama
NobleCircles Genealogy © Haceldama is a searchable genealogical relationship database consisting of more than 440,000 people and 165,000 families at 30,000 places worldwide – all gathered in one single family tree; mapping their ancestors, descendants and various relatives and all of them somehow related to each other. The database also includes all European and some Middle Eastern royal families, many European noble families, 28 US Presidents, 33 British Prime Ministers and all 141 Danish Privy Councillors and Danish Prime Ministers and many of their relatives. You can follow NobleCircles Genealogy © Haceldama if you join our Facebook Page and our Facebook Group. You can at on the Log File see what other people latest looked at in the database, which were last updated on July 01 2019.
中文; / zhōngwén (Chinese) Afrikaans (Afrikaans) Dansk (Danish) Deutsch (German) English (English) Español (Spanish) Français (French) Hrvatski (Croatian) íslenska (Icelandic) Italiano (Italian) Nederlands (Dutch) Norsk (Norwegian) Polski (Polish) Português (Portuguese) Română (Romanian) Srpski (Serbian) Suomi (Finnish) Svenska (Swedish)
Manhattan, New York City, New York, USA
1 Davis, Nancy 6 Jul 1921 Manhattan, New York City, New York, USA I392557
2 Deveau, Frederick Joseph 23 Feb 1895 Manhattan, New York City, New York, USA I440317
3 Harttung (Harttung), Maria Johanna Dorothea 22 Jun 1870 Manhattan, New York City, New York, USA I282311
4 Kane, Emily Astor 1854 Manhattan, New York City, New York, USA I440261
5 Shields, Brooke Christa I21679
6 Thaanum, Alfrida Georgine 1 Oct 1888 Manhattan, New York City, New York, USA I410454
7 Thaanum, Peter Elias 4 Sep 1887 Manhattan, New York City, New York, USA I410455
8 Trump (Trump), Donald John I257215
9 Trump (Trump), Eric Frederick I257217
10 Trump (Trump), Ivanka Marie I257216
11 Vanderbilt (Vanderbilt), Gloria Laura 20 Feb 1924 Manhattan, New York City, New York, USA I242920
1 Ashley-Cooper (Ashley), Lord Anthony Nils Christian The 11Th Earl of Shaftesbury 15 May 2005 Manhattan, New York City, New York, USA I227017
2 Boettiger, John 31 Oct 1950 Manhattan, New York City, New York, USA I227090
3 Passano (Passano) 30 Oct 1926 Manhattan, New York City, New York, USA I255064
4 Passano (Passano), William Ramsey 23 Aug 1927 Manhattan, New York City, New York, USA I45542
5 Rockefeller (Rockefeller), Laurance Spelman 11 Jul 2004 Manhattan, New York City, New York, USA I283414
6 Willard, Belle Wyatt 30 Mar 1968 Manhattan, New York City, New York, USA I227110
1 Bruun / Hornwain 4 Jun 1869 Manhattan, New York City, New York, USA F50569
2 Harttung (Harttung) / Grimm 28 Jun 1905 Manhattan, New York City, New York, USA F111190
3 Harttung (Harttung) / Intemann 12 Nov 1867 Manhattan, New York City, New York, USA F110578
4 Malatesta / Seierup 10 Oct 1929 Manhattan, New York City, New York, USA F85299
5 Omann (Omann) / Larsen 17 May 1934 Manhattan, New York City, New York, USA F60514
6 Roosevelt (Roosevelt of Benelux) / Perrin 31 Aug 1949 Manhattan, New York City, New York, USA F94580
Maintained by Nick MacGregor Sadolin (NobleCircles Genealogy © Haceldama). | Data Protection Policy.


Three scholarships are awarded annually to students entering a baccalaureate nursing program in New Brunswick. Applicants must be a relative of a current or former NBNU member.
On a provincial basis, NBNU offers one (1) $1,000 scholarship to a full-time second year student and one (1) $1,000 scholarship to a full-time third year student studying in the baccalaureate program and enrolled in either the Francophone or Anglophone program. Applicants must be a relative of a current or former NBNU member.
Each year, NBNU offers three (3) $1,000 scholarships to the children of NBNU members enrolled in a community college or university program.
One $1000 scholarships will be awarded by the Canadian Federation of Nurses' Union to a recipient selected by NBNU. Recipients must be a relative of a current or former NBNU member.
On an annual basis, NBNU grants a total of fourteen $800 scholarships for nursing students in the BN program at all of the seven teaching institutions (U de M and UNB – Moncton, Edmundston, Fredericton, Bathurst, Shippagan, Saint John). The student body of each site will select the most deserving student from their group to receive the bursary.
NBNU members and their children are also eligible for some scholarships and bursaries as an affiliate of the NBFL and CLC. Below is a list which can also be accessed on the NBNU website.
o Two $500 scholarships are for first year attendance at any university in the Atlantic province or first year attendance in a two-year program of the New Brunswick Community College, excepting where the desired academic program is not available in the region. Deadline is June 30th of each year.
o Two $500 bursaries open to any person regardless of union membership pursuing post secondary education full-time or enrolled in high school at the grade 12 level. Deadline is June 30th of each year.
o Local union members and labour councils affiliated with the NBFL undertaking labour history projects, labour libraries, Day of Mourning monuments, etc., as well retraining programs due to plant downsizing or closures. Deadline is June 30th of each year.
o Eligible for consideration are NBFL affiliates, as well as provincial and community organizations undertaking or sponsoring, partially or fully, literacy projects and workplace related training activities including union developed programs. Deadline is June 30th of each year.
o $2,500 to support a young activist who is starting their first year of full-time post-secondary study in September 2018. Applicants must be 30 or under as of September 1, 2018 and enrolled for September 2018 to enter their first year of full-time study at a Canadian public post-secondary institution (leading to a degree) or college program (leading to a diploma or certificate); does not have any prior post-secondary studies and; currently enrolled or not more than two years out of secondary school.