text:
The Curator Behind the Acclaimed 'Art in the Streets' Show in LA Is Bringing a Follow-Up to New York
Graffiti historian and urban anthropologist Roger Gastman is bringing a massive street-art show "BEYOND THE STREETS" to New York.
Martha Cooper photograph of a Style Wars Car by NOC 617 at 96th Street station in 1981. Photo courtesy of the artist.
New York City, once the world's foremost graffiti mecca, will soon play host to a massive exhibition celebrating the history of street art, curated by graffiti historian and urban anthropologist Roger Gastman. The show, "BEYOND THE STREETS," is Gastman's follow up to his hit 2011 exhibition "Art in the Streets" at the Museum of Contemporary Art Los Angeles.
The show is set to open in an office building in Williamsburg, Brooklyn, on June 21. It will showcase street art's storied history, including, for example, Martha Cooper's classic photos of graffiti on the streets and subway cars of 1980s-era New York.
It will go on to explore the work of more than 150 artists, from Jean-Michel Basquiat and Keith Haring to Takashi Murakami and José Parlá, showing the art form's evolution from a symptom of urban blight and decay to a lucrative facet of the blue-chip art market. Other boldfaced names include Lady Pink, Lee Quiñones, Maripol, Maya Hayuk, Gordon Matta-Clark, Rammellzee, Nina Chanel Abney, Swoon, INVADER, Jenny Holzer, the Guerrilla Girls, and Kenny Scharf.
The exhibition will also pay tribute to the 30-year career of Shepard Fairey, who will debut a mini retrospective titled "Facing The Giant: Three Decades of Dissent." In addition, there will be a special focus on the intersection of street art and music, with a section featuring artifacts and ephemera from Brooklyn rap trio the Beastie Boys. Gastman will also highlight the long history of activism among street artists.
Martha Cooper photograph of Lil' Crazy Legs in Riverside Park in 1983. Photo courtesy of the artist.
At LA MOCA, the "Art in the Streets" retrospective set an all-time attendance record of 220,000 visitors. Gastman first staged "BEYOND THE STREETS" in a 40,000-square-foot Los Angeles warehouse last spring. The New York edition stands to be even bigger, taking over two floors—over 100,000 square feet in total—of what's being billed as a "creative" office building.
On the East Coast, the show will include "a curated gift shop" offering more than 150 items, according to the press release, which is a somewhat ironic addition considering that Gastman was the co-producer on Banksy's film Exit Through the Gift Shop.
Photo courtesy of "BEYOND THE STREETS."
"I'm really excited to bring this show to the art form's epicenter: New York," Gastman told amNewYork. "The city plays such a pivotal role in the origin and evolution of the culture—the iconic images of covered subway cars made graffiti famous worldwide."
Here are all the artists appearing in the show so far:
Al Diaz
Alexis Ross
Alicia McCarthy
André Saraiva
Bert Krak
Bill Barminski
Bill Daniel
Broken Fingaz
Buddy Esquire
buZ blurr
Carlos Mare
Carl Weston
Cey Adams
C.R. Stecyk III
Charlie Ahearn
Claudia Gold
COCO 144
Craig Costello
DABSMYLA
Dan Witz
Dash Snow
Dondi White
EARSNOT
Fab 5 Freddy
Faith XLVII
Glen E. Friedman
Henry Chalfant
Herb Migdoll
Husk Mit Navn
Jason REVOK
Jim Prigoff
John Fekner
John Tsombikos
Joe Conzo
LEE Quiñones
Lisa Kahane
MADSAKI
Maripol
MIKE 171
Mister CARTOON
Nina Chanel Abney
NOC 167
Pat Riot
Patrick Martinez
Randall Harrington
RETNA
Richard Colman
Sam Friedman
SANESMITH
Sayre Gomez
SJK 171
SNIPE1
STAY HIGH 149
Stephen Powers
TAKI 183
TATS CRU
TENGAone
Tim Conlon
Timothy Curtis
Todd James
Trash Records
VHILS
ZESER
"BEYOND THE STREETS" will be on view at Twenty Five Kent, 25 Kent Ave, Brooklyn, beginning June 21, 2019.
Street Art Pioneer Fab 5 Freddy Looks to Renaissance Art for Lessons About Race in His New BBC Film—and Rides a Horse While Doing It
By Taylor Dafoe , Jul 22, 2019
Henry Chalfant, One of the Definitive Photographers of Early Subway Art, Will Return to the Bronx This Fall For His First US Retrospective
By Taylor Dafoe , May 28, 2019
Sotheby's and a Former Banksy Dealer Team Up to Test the Market for Street-Artist Rammellzee in London
By Sarah Cascone , Aug 10, 2018
Lee Krasner Had to Fight Her Way Into the History Books. Here are 5 of the Biggest Battles She Faced
Crushed by Debt, the Biennial of Australian Art Has Folded With Dozens of Artists Still Awaiting Payment


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Second-generation Toyota Mirai to demo here in '21
Published on 30th November 2020 at 15:19
Toyota, having begun development of a hydrogen fuel cell electric vehicle in 1992,
when they introduced the Mirai saloon, have announced their second-generation
Mirai will be available in 2021. Toyota Ireland are looking to bring in a demonstrator
model here in 2021, with limited numbers arriving in 2023, in conjunction with the
Hydrogen Mobility Ireland Roadmap
No other emissions than pure water
With the launch of this second-generation Mirai, Toyota are confident that this is a car that takes FCEV technology to a higher level and includes a comprehensively redesigned fuel cell system, intelligent packaging and aerodynamic efficiency help extend the driving range to around 650 km, with no other emissions than pure water.
Dublin trial
News of the new Mirai comes just two weeks after Hydrogen Mobility Ireland (HMI) announced a multi week, in-service, trial of a fuel cell electric bus in the Dublin area. This will be the first ever Hydrogen Fuel Cell Electric Vehicle (FCEV), powered by a 60Kw Toyota Mirai fuel cell stack. The trial looks to demonstrate the many practical uses and environmental benefits of hydrogen towards a carbon-free society.
Toyota Ireland is looking to bring a Mirai demonstrator model to Ireland in 2021, along with a temporary refuelling station. Working closely with the Hydrogen Mobility Ireland, of which Toyota Ireland director Mark Teevan is Chairman, the ambition is to bring in limited numbers of the Mirai in 2023, when refuelling stations are available in Dublin.
Steve Tormey, Chief Executive of Toyota Ireland commented on the announcement: "The new Mirai represents a major step forward in sustainable motoring, emitting only water from the tail pipe, and going beyond zero emissions by cleaning the air as it moves.
"We are very excited about bringing the new Mirai to Ireland, and are looking to bring in demonstrator models next year. Hydrogen fuel cell can play a pivotal role in moving us towards a carbon-free environment and it is a real game changer for the health and wellbeing of our planet and future generations."
Cleaning the air as you drive
The environmental benefits of driving the Toyota Mirai go beyond zero emissions to "negative emissions" – as the car effectively 'cleans the air' as it moves. A Toyota innovation, a catalyst-type filter is incorporated in the air intake. As air is drawn into the vehicle to supply the fuel cell, an electric charge on the non-woven fabric filter element captures microscopic particles of pollutants, including sulphur dioxide (SO2), nitrous oxides (NOx) and PM 2.5 particulates. The system is effective in removing 90 to 100% of particles between 0 and 2.5 microns in diameter from the air as it passes into the fuel cell system.
Improvements in performance and design
In developing the new Mirai, Toyota has made it a priority to improve its driving range compared to the first-generation model and going beyond the distances typically achieved by battery electric vehicles. Increased power and hydrogen fuel capacity, improved efficiency and better aerodynamics all contribute to extending the driving range by 30% to around 650 km.
The new Mirai is built on Toyota's modular GA-L platform, which is already in use in the top-of-the range Lexus LS. This provides a more efficient and well-balanced arrangement of the new FCEV powertrain – notably with the fuel cell stack moved from beneath the cabin to the front compartment – has allowed for a more spacious, five-seat interior with improved legroom for rear seat passengers.
The new Mirai's overall height has been reduced by 65 mm to 1,470 mm, and there is a 140 mm increase in the wheelbase (2,920 mm). The rear overhang is extended by 85 mm, overall vehicle length is now 4,975 mm. A 75 mm increase in the track width and the use of larger, 19 and 20-inch wheels, (fitted with 235/55 R19 and 245/45 R20 tyres respectively), adding to give the Mirai a lower and more dynamic stance, plus a lower centre of gravity.
GA-L platform
Adopting the GA-L platform has resulted in the Marai being a spacious, five-seat cabin and a better chassis balance. It also enables three high-pressure hydrogen tanks to be fitted, increasing fuel capacity and the car's driving range – by 30%.
The tanks are arranged in a "T" configuration, the longest running longitudinally and centrally beneath the vehicle floor, with two smaller tanks set laterally beneath the rear seats and luggage compartment. Together they can hold 5.6 kg of hydrogen, compared to 4.6 kg in the current Mirai's two tanks.
The new architecture also permits the all-new hydrogen fuel cell to be moved r to the front compartment (equivalent to the engine bay), while the (more compact) high-voltage battery and electric motor are positioned above the rear axle. This powertrain layout has been optimised to give new Mirai a 50:50 front:rear weight distribution.
The new Mirai is equipped with lithium-ion high-voltage battery in place of the current model's nickel-metal hydride unit. Although smaller in size, it is more energy-dense, giving higher output and superior environmental performance. Containing 84 cells, it has a 310.8 rated voltage compared to 244.8, and a 6.5 Ah capacity, versus 4.0 Ah. Overall weight has been reduced from 46.9 to 44.6 kg. The output has improved from 25.5 kW x 10 seconds to 31.5 kW x 10 seconds.
The batteries are positioned behind the rear seats, avoiding intrusion in the load compartment. An optimised air-cooling path has been designed, with discreet inlets either side of the rear seats.
Targeting a 10-fold increase in sales
The introduction of the new Mirai will see Toyota target deeper market penetration with a 10-fold expansion in sales volume. This growth will be supported by the new model's stronger performance and greater customer appeal, notably as a more affordable vehicle with a selling price reduced by around 20%.
The practicality of hydrogen FCEV ownership will also steadily increase as markets improve their hydrogen infrastructure, the number of filling stations rises and Governments and local authorities introduce new incentives and regulations for cleaner mobility.

redpajama_set_name: RedPajamaCommonCrawl


However, formatting rules can vary widely between applications and fields of interest or study. Sloterdijk's father was Dutch, his mother German.
Please verify that you are not a robot. The Schelling Project has not even been intended as a novel; it has been launched as sheer act of provocation. Your list has reached the maximum number of items. To underline this he notes that "whomever turns away from Eros deprives himself of the vital form. In he received his PhD from the University of Hamburg.
Explore the Home Gift Guide. Retrieved 11 December Consequently, he proposes the creation of an "ontological constitution" that would incorporate all beings—humans, animals, plants, and machines.
More like this Similar Items. Sloterdijk has said that the first paragraphs of Spheres are "the book that Heidegger should have written", a companion volume to Being and Timenamely, "Being and Space".
ComiXology Thousands of Digital Comics. Another dispute emerged after Sloterdijk's article "Die Revolution der gebenden Hand" 13 June ; transl. You may send this item to up to five recipients. Please select Ok if you would like to proceed with this request anyway.
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Sloterdijk rejects the existence of dualisms —body and soul, subject and object, culture and nature, etc. Withoutabox Submit to Film Festivals. He is a professor of philosophy and media theory at the University of Art and Design Karlsruhe.
The exploration of these spheres begins with the basic difference between mammals and other kaapitals University of Munich University of Hamburg. Sloterdijk opened the text with the famous quote of leftist critics of capitalism made famous in the 19th century by Proudhon in his " What Is Property? Sloterdijk's provocative recommendation was that income taxes should imm deeply reduced, the difference being made up by donations from the rich in a system that would reward higher givers with social status.
Cancel Forgot your password? Breaking a German taboo on the discussion of genetic manipulation, Sloterdijk's essay suggests that the advent of new genetic technologies requires more forthright discussion and regulation of "bio-cultural" reproduction.
This becomes clear in the introduction to the trilogy, where Sloterdijk writes about Plato's academy which allegedly denied anyone access who was not a mathematician, or a very precise scientist. The E-mail Address es you entered is are not in a valid format.
Sloterdijk replied that this was, itself, resorting to "fascist" tactics to discredit him. In the eyes of Habermasthis made Sloterdijk a "fascist". For Sloterdijk, "God thus becomes the location of a transcendent repository of suspended human rage-savings and frozen plans of revenge. Your rating has been recorded. Phenomenologyphilosophical anthropologyposthumanism. This second criticism was based on the vagueness of Sloterdijk's position on how exactly society would be affected by developments in genetic science.
According to Sloterdijk, the institutions mi the welfare state lend themselves to a system that privileges the marginalized, but relies, unsustainably, on the class of citizens who are materially successful. The difference for Sloterdijk is that, weltinnenrauj the second wave created cosmopolitanismthe third is creating a global provincialism. Advanced Search Find a Library. Learn more about Amazon Prime. In Januaryan English translation was published, titled "A Grasping Hand — The modern democratic state pillages its productive citizens", in Forbes  and in the Winter issue of City Journal.
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The specific requirements or preferences of your reviewing publisher, classroom teacher, institution or organization should be applied. You already recently rated this item. Sloterdijk's book, Die nehmende Hand und die gebende Seitecontains the texts that triggered the — welfare state dispute. He co-hosted the German television show Im Glashaus: Search WorldCat Find items in libraries near you.
Spheres is in "spaces of coexistence", spaces commonly overlooked or taken for granted that conceal information crucial to developing an understanding of the human.
Allow this favorite library to be seen by others Keep this favorite library private. Male fantasies of women "dripping wet like a gravel lorry" "tropfte [ There Sloterdijk claimed that the national welfare state is a "fiscal kleptocracy" that had transformed the country into a "swamp of resentment" and degraded its citizens into "mystified subjects of tax law".


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Lincoln Allison
Lecturer & Essayist
Home » Travel » Isola di Paradossi
Isola di Paradossi
Posted on November 15, 2018 by Lincoln Allison
The highlight of a month's wandering round Europe this autumn was hearing Leo Nucci sing Rigoletto in the Teatro Massimo in Palermo. The duet with Gilda was so good it stopped the show: shouts of "Bravo" and also of a lot of comments which I didn't catch. The whole scene was played again. I thought it was very good and I didn't know than Nucci is seventy six years old and a legendary stalwart of Italian opera. The upshot is that the only two occasions on which we have been to operas in Sicily are also the only two occasions in which we have seen the show ground to a halt. At the Taormina Opera Festival in 2002 Cavalleria Rusticana was stopped by booing whereas here it was cheering. The have strong and clear opinions, these Sicilian chaps.
It was hot in the opera house so we went for a drink before strolling back to our extremely idiosyncratic two-storey hotel suite. There were tens of thousands of people on the streets. They were having a good look at each other and often greeting each other, talking and sometimes singing. There were many children and large families and very old people who in most countries would be cowering indoors at midnight. There were various street entertainments and you wouldn't have needed any money to have an enjoyable evening. There was no drunkenness, no violence and no sense of any threat, prompting the question as to whether there is another city in the entire world that you would rather walk through at midnight than Palermo? But, next morning, walking to the cathedral, the impression was different: there was litter everywhere and masses of uncollected rubbish. Parking is anarchic and driving aggressive. A lot of English people would respond by calling it "third world", but that's a misleading cliché. The social scientist in me saw a society which in its civic dimension is week, in its kinship dimension strong and in its civil dimension also weak, but complex and changing.
Monreale is a hill town just outside Palermo and easily accessed by regular buses. Its cathedral is a very confusing building. Seen from the north, the town side, it looks at first as if it could belong in many other parts of Europe further north (there is no further south). It is constructed in beige stone and reminded me of a building in Falaise in Normandy until I looked more closely at the lower and smaller of two lines of windows which look distinctly exotic and non-European. If you go round the other sides of the building it is a riot of orientalism which you might expect to find in Morocco. The is "Arabo-Norman" architecture, Sicily's unique marriage of the extreme ends of the then known world, created by Norman warrior-bosses and Arab craftsmen. Go inside the building and it is something else again, the greatest expanse of Byzantine mosaics in the world. These are as unlike the light, pastelly, domestic mosaics of a Roman villa as it is possible to be. They are dark, green and gold, redolent of the east, of mysticism and magic. The nine great buildings of the "Arabo-Norman" tradition, including also Palermo Cathedral, are (of course) a "World Heritage Site".
At Agrigento, in the middle of the south coast of Sicily, there are probably the most extensive ruins of any ancient Greek city, Greece included. They stretch along a ridge overlooking the sea whence came the Carthaginians who pestered and, eventually, destroyed the city. Apart from a few curators the ruins are inhabited, even well into the autumn, by thousands of tourists from most of the countries on the planet. But on the ridge inland from and above the ancient city lies the modern city of Agrigento, only a few hundred yards away. It is much smaller, around the same size as Leamington Spa where we live. So far as I can see there are no tourists in modern Agrigento; the litter and rubbish are at the level of Eminesque self-caricature. This is said to be the Mafia capital of Sicily and epicentre of the heroin industry.
Ah, yes – the Mafia. In Palermo Mafia references are ubiquitous; they are on the memorials to victims, on political posters, in the newspapers and referred to also in the shops and stalls of anti-Mafia civic campaign organisations. In Agrigento the word is nowhere to be seen or heard: it's the old style. Thus the Sicilian condition. Greek. Roman. Arab. Norman. Spanish. Italian. Whatever. Mafia. Not-Mafia. Beautiful, apart from where it's plug ugly. Friendly (but not at Catania Airport). Rich in essence, poor in practice. Everywhere layered, contradictory and complex, stuffed with ambivalence and paradox.
And – here I may annoy you if you're that nice sort of person who sees cosmopolitanism as an extension of your niceness and entertains the illusion that internationalism is essentially benign. Do I love Sicily? Is it high on my list of places to revisit? Yes and of course. Do I want England to be in any kind of political or financial union with Sicily? Of course not. Do I think the European Union has been bad for Sicily and good for the Mafia? Of course. On the boat to Palermo I read the great Sicilian novel, Tomassi Di Lampedusa's The Leopard (Il Gattopardo). The Prince who is the leading character is opposed to the unification of Italy on grounds similar to those of my opposition to European integration; he was right to be so – these unifications spread vices a good deal more efficiently than they spread virtues.
Finally, and on a lighter note, Sicily furnishes one of my favourite quiz questions:The highlight of a month's wandering round Europe this autumn was hearing Leo Nucci sing Rigoletto in the Teatro Massimo in Palermo. The duet with Gilda was so good it stopped the show: shouts of "Bravo" and also of a lot of comments which I didn't catch. The whole scene was played again. I thought it was very good and I didn't know than Nucci is seventy six years old and a legendary stalwart of Italian opera. The upshot is that the only two occasions on which we have been to operas in Sicily are also the only two occasions in which we have seen the show ground to a halt. At the Taormina Opera Festival in 2002 Cavalleria Rusticana was stopped by booing whereas here it was cheering. The have strong and clear opinions, these Sicilian chaps.
Finally, and on a lighter note, Sicily furnishes one of my favourite quiz questions:
QUESTION: From which king of England does the Godfather get his name?
ANSWER: Richard I.
EXPLANATION: When the boy Vito Andolini arrives at Ellis Island the incompetent American official dealing with his case confuses his family name with his birthplace so that he becomes Vito Corleone. The name, of course, means "Lionheart" and the town is called after Richard (I) the Lionheart.
Lincoln Allison November 2018
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© 2019 Lincoln Allison
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I made the mistake of having something shipped from The States to myself in Japan via Federal Express. FedEx has very un-Japanese (and hence horrible) service in Japan. My package cleared Japanese customs at about noon on Friday, and had I shipped with any other carrier I would have the package in my hands on Saturday. Yet here it is two days later and FedEx's tracking hasn't even updated. I called FedEx Japan, and they're closed!. "Call Back Monday".
I paid through the nose for the fastest shipment possible, only to find that I chose a lazy, clueless company. Sigh.
I should have known to expect this... this is a company that won't leave packages in the secure package boxes that modern condos have to hold deliveries for residents who aren't home at the time. Every other express delivery service uses them, and I've gotten bitten in the past by FedEx not using them, having to contort my schedule to match theirs. What a hassle.
Never again. FedEx, you are worthless in Japan.
That's a bummer, because (as you well know) in the US they're pretty much the cream of the crop for level of service in an express package service. I routinely "pay more for service" by using them instead of Brown or (shudder) the USPS.
I once had to FedEx something from Japan, and this involved going to their office down in Osaka.
There basically IS no FedEx in Japan. Just like four losers running around in purple shirts who get paid minimum wage. Since Kuroneko rocks so much, though, who cares?
Yup, FedEx, DHL, etc – steer well clear in Japan. Their other nice trick is to pay any import duty (usually the maximum possible) for you, and then bill you for it separately.
I one had my DHL customs declaration sent back to my house by a kindly member of the public, after the DHL guy left it blowing round the street in Shibuya, Tokyo.
Japan Post EMS on the other hand – as fast as Fedex – and a fraction the cost!
Fedex is a rubbish service in UK. More than 60% of their deliveries are not getting result. No messages left -cards nothing, plenty of loose because of their lack of customer care. Completely useless , one of the worst couriers i've ever had . For me they're just losers and their time is counted, looking forward their bankruptcy.


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Underdogs Tottenham head to Amsterdam with hope
George Sessions
Published: 4:00 PM May 1, 2019 Updated: 10:48 AM October 14, 2020
Ajax's Donny van de Beek (left) and Tottenham Hotspur's Kieran Trippier battle for the ball during the Champions League semi-final, first leg at Tottenham Hotspur Stadium (pic: Mike Egerton/PA Images). - Credit: PA Wire/PA Images
The equation is now pretty simple – Spurs have to find the net and win in the Champions League semi-final second leg
Tottenham Hotspur will be underdogs when they step out at the Johan Cruyff Arena on Wednesday, May 8, but everything is still to play for in the Champions League semi-final second leg.
Ajax hold a one-goal lead after the first meeting in London following a supremely cool finish by Donny van de Beek in the 15th minute at Spurs.
For large spells in the first half, it seemed only a matter of time before the visitors extended their advantage, but Mauricio Pochettino's team just about stood firm.
Moussa Sissoko's arrival in the 39th minute, coupled with a formation change to 4-3-2-1, helped them get back into the tie and some could argue they deserved a draw.
In the end it was a defeat, but the equation is now pretty simple – Tottenham have to find the net and win in Amsterdam.
Any victory will give them a great opportunity to reach a maiden European Cup final and the squad remain positive about their chances.
Right-back Kieran Trippier said: "We just need to go into the game knowing we need to win the game.
"We know we need to score more than one goal obviously, but we don't want to focus on who has got the advantage.
"Our aim is to go to Ajax with a clear mind and try to win the game."
Tottenham badly missed Heung-min Son on Tuesday, who would have watched from the stands with simmering frustration while Harry Kane and Harry Winks were sorely missed too.
After Hakim Ziyech sliced open the Spurs defence with a fine through ball, van de Beek showed brilliant composure to slot past Hugo Lloris.
It was almost two when van de Beek got in again, but this time Lloris saved with his feet in the 24th minute and a great chance had been wasted.
Slowly but surely the hosts grew into the game with the impact of substitute Sissoko clear for all to see.
Yet Tottenham struggled to fashion chances and the main efforts they had were headers by Fernando Llorente and Toby Alderweireld which failed to test Andre Onana.
Dele Alli did have one shot on target, but it was straight at the away custodian from 20-yards and snatched at.
Ajax almost put the fixture and semi-final to bed when David Neres fired towards goal from 10-yards in the 78th minute, but his effort hit the post and Spurs remain alive.


Glycine-l-arginine-alpha-ketoisocaproic acid (GAKIC) is a safe and natural blend of amino acids that is commonly used by bodybuilders, gym users and athletes to combat muscle fatigue, maintain muscle force during workouts and increase training intensity. Because GAKIC is supported by significant scientific research to offer immediate results when taken before intense exercise, it′s considered one of the best safe and natural training and performance aids available.
Intense weight training or exercise involving intense power output (such as sprinting) causes a rapid build-up of intra-muscular toxins - particularly ammonia which quickly increases the pH of muscle tissue. Unfortunately, the result is fatigue and a rapid decline in muscle power, strength and endurance (for example, the fatigue experienced when performing heavy barbell squats).
l-leucine dehydrogenase, which in turn increases ammonia removal via the production of the amino acid l-leucine.
Because GAKIC immediately increasing the body′s capacity to buffer muscle toxins, GAKIC offers gym users and athletes a way of rapidly increasing their performance and training intensity (unlike creatine, GAKIC does not need ′loading′ for several days). The ability to perform more repetitions and lift heavier weights is likely to significantly increase long-term muscle growth and strength development.
Arginine is a multi-functional nutrient, but plays a role in the excretion of ammonia from muscle cells. Since ammonia is known to cause acute muscle fatigue, the arginine in GAKIC may have significant effects in reducing fatigue. Arginine also promotes hormone production and nitric oxide synthesis, which may aid muscle pumps and nutrient delivery.
KIC is a branched-chain keto acid (BCKA) that has the capacity to remove ammonia from muscle tissue during ATP energy metabolism. The combination of arginine and KIC is believed to be very effective in reducing muscle toxins and buffering metabolic acids. In addition, KIC′s anti-catabolic action help to prevent muscle breakdown and aid long-term muscle development.
The latest research shows that growth hormone synthesis increases proportionally with the intake of the amino acid glycine . Because growth hormone is considered a factor in muscle growth, part of GAKIC′s benefits may be due to elevated growth hormone levels.
The current GAKIC research supports the view that the nutrient enhances resistance to fatigue and increases workout capacity.
Researchers at the University of Florida conducted a double-blind, randomized, crossover-study, comparing the effects of glycine-l-arginine-alpha-ketoisocaproic acid calcium (aka GAKIC) vs. a placebo (9.46 g sucrose) before resistance training on a knee extension machine. GAKIC was found to increase resistance to fatigue by 28%, and elevate muscle work by 10.5%, during a 15 minute workout .
This data may translate into real results in the gym. For example, if you can perform 8 reps with 80kg, GAKIC may enable you to lift the same weight 10 times (approximately 28% more resistance to fatigue).
Further research has reported that glycine-l-arginine-alpha-ketoisocaproic acid prevents fatigue-induced power reduction during cycle sprints, supporting the benefits of GAKIC as a muscle power and workout aid .
Another benefit of GAKIC supplementation is the nutrient′s rapid effects, which according to scientific research, can be experienced by consuming the supplement prior to exercise (i.e. you do not need to wait days to feel GAKIC working). This makes GAKIC a promising, non-stimulant pre-workout nutrient. Since GAKIC need only be taken on workout days, it′s also likely to appeal to trainers on a budget.
Who can benefit from GAKIC?
GAKIC is increasingly being used by a wide range of gym users, bodybuilders, athletes and sports players. Essentially, the nutrient may be useful for anyone performing high intensity exercise (such as weight trainers, bodybuilders, sprinters, boxers, football players and even endurance runners for bursts of power). GAKIC can be used as both a performance aid, and a muscle and strength builder ∼ depending on your goals.
How do I take GAKIC?
To get the performance effects detailed in research studies, it′s recommended to consume 8-10g of GAKIC 30 minutes before training. The effects of GAKIC are rapid, so there is no need to load the nutrient or take a serving on rest days. If you are considering using GAKIC, it is essential to use a full potency brand containing the genuine ingredients. GAKIC can be taken alone, but it can also be found in some cutting-edge pre-workout products where it is stacked with other research proven anti-fatigue nutrients such as creatine, beta alanine, histidine and citrulline malate.
What results can I expect from GAKIC?
Most GAKIC users experience a greater workout capacity the first time they use the supplement (GAKC is designed to work immediately when taken 30 minutes pre-workout). If you are training for muscle mass, by enabling significantly more reps in every set, GAKIC is likely to enable more productive workouts and subsequently more muscle growth over weeks and months.


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Sarah Walsh
USA Rugby Eagle Profile
Eagle No.
Berkeley All Blues W.R.C.
Colby College
@scwalsh
Walsh was an All-American basketball player at Colby College and played professional basketball in the Netherlands. Walsh began playing rugby once her basketball career was done. Walsh was a member of the Women's Division I National Champions North Shore in 2011, and the Women's Premier League Champions Berkeley All Blues in 2013. Walsh's first cap with the Women's Eagles was in 2008 against England.


Nearly five months after President Trump first confronted China with tariffs over its trade practices, the two countries are further than ever from resolving their differences and appear to be digging in for what is likely to be a long and bruising conflict.
China said Wednesday that it would impose tariffs on an additional $16 billion in U.S. autos and energy products, retaliating for the Trump administration's latest import levies on an equivalent value of Chinese goods.
Beijing signaled this week that it might target prominent American companies such as Apple if the trade dispute escalates. The iPhone maker relies upon China for one-fifth of its $229 billion in annual revenue, "leaving it exposed if Chinese people make it a target of anger and nationalist sentiment," warned a commentary in the state-owned China Daily.
Trump administration efforts to force China into concessions also have been complicated by the falling yuan, which has lost more than 8 percent of its value against the dollar since April. By making Chinese products less expensive for American buyers, the weaker yuan partially counteracts the effects of Trump's trade measures.
But within the administration, there is growing unease over where the U.S.-China tussle is headed. Initial diplomatic talks, which failed to reach agreement, have left both sides irritated and confused about the path to a deal.
Two senior administration officials, frustrated by what they say is Chinese President Xi Jinping's refusal to negotiate, have become increasingly certain that the standoff is only going to worsen. Economic threats will continue escalating before any settlement is possible, they said.
Even as Trump's approach to China thus far bears little fruit, administration officials say they are optimistic they will be able to announce by the end of this week agreement with Mexico on key elements of a new North American trade deal. U.S. and Mexican negotiators are finalizing new rules for granting automobiles duty-free treatment, which would require more manufacturing work to be done in high-wage factories, according to three sources familiar with the talks, who spoke on the condition of anonymity to discuss confidential conversations.
Any such agreement would still need to be reconciled with Canada, the third party in the original 1994 North American trade accord. But a U.S.-Mexico arrangement is expected to lead to the end of U.S. tariffs on steel and aluminum from Mexico as well as retaliatory Mexican tariffs that hurt American farmers' south-of-the-border sales, said Dan Ujczo, a trade lawyer with Dickinson Wright.
Still, the administration's hard-line stance on China is stirring doubts among congressional Republicans and business leaders, who fear it may rupture profitable commercial relations. With no formal talks taking place between Chinese and American officials, some analysts say Trump's use of tariffs may be designed to reverse a quarter-century of growing economic ties between the two countries, rather than to spur diplomatic bargaining.
The latest tariff salvos stem from Trump's complaint that China is unfairly acquiring American technology via coercive joint ventures with U.S. companies, cybertheft and other violations of intellectual property rights.
After months of skirmishing between the two economic powers, U.S. customs officers began collecting the first tariffs from importers of Chinese products on July 6. China immediately retaliated with similar tariffs on U.S. goods, including soybeans, pork and poultry, which were designed to hurt Trump voters in rural America.
When the additional tariffs go into effect on August 23, both countries will have taxes on about $50 billion worth of imports from the other.
Trump also is proceeding with plans to tax a further $200 billion in Chinese products as soon as September and has threatened to eventually impose tariffs on all Chinese imports, which totaled $505 billion last year, unless China capitulates.
The president remains confident that his "America First" overhaul of U.S. trade policy is paying dividends. At Tuesday's CEO dinner, Trump said his "powerful trade policies" had contributed to the economy's 4.1 percent growth rate in the second quarter.
As additional trade deals are signed, the president predicted that economic growth would "go much, much higher," a view at odds with his own administration's forecasts.
Trump has claimed in recent tweets that "tariffs are working far better than anyone ever anticipated," linking them to a downturn that has shaved nearly a quarter from the value of Chinese stocks since late January. Along with the trade spat, Chinese stocks have suffered from slowing growth in the debt-laden economy.
But China has notched a pair of concrete victories in the trade showdown, according to Jeff Moon, a former U.S. trade negotiator in the Obama administration.
After complaints by Chinese leaders, Trump agreed to reverse a U.S. enforcement action that would have caused ZTE, a prominent state-owned telecommunications company, to go out of business. And last month, Chinese regulators barred Qualcomm, an American telecom leader, from completing its $44 billion acquisition of Netherlands-based NXP, which would have made it a more formidable competitor for Chinese companies.
"There are only two hard outcomes so far and China's winning 2-0," Moon said.
Though months of verbal exchanges make it feel as if the two countries have been locked in protracted commercial combat, the first tariffs have been in effect for only about a month. The financial pain so far has been felt by individual companies or industries — and their workers — rather than by either the overall U.S. or Chinese economy.
China's announcement is a direct response to new duties on Chinese goods imported into the United States, announced Tuesday in Washington. Those new tariffs, totaling $16 billion, will be levied against 279 products, including motorcycles, steam turbines and railway cars.
Administration officials believe that the $505 billion Americans spend on Chinese products each year gives them leverage over China. Beijing already has stopped trying to match the U.S. tariffs on a dollar-for-dollar basis, threatening to hit just an additional $60 billion in U.S. imports if the president follows through on his threat to target a further $200 billion in Chinese products.
But the Chinese government can employ other tools if the conflict continues. In a dispute with South Korea last year over its role in hosting a U.S. missile defense system, the Chinese government orchestrated a boycott of Seoul-based Lotte Group that ultimately persuaded it to sell many of its stores in China.
"We'll know China is really feeling the pressure when they start stirring nationalist sentiment or calling for boycotts against U.S.," said Bruce Andrews, managing director of Rock Creek Global Advisors.
After months of escalation, business executives in both countries are wondering when and how the trade confrontation will end.
"With each successive round of tariffs, Trump continues to back China into a corner, forcing Beijing to respond in kind," said James Zimmerman, a partner in the Beijing office of Perkins Coie.
Kevin Sieff in Mexico City and Emily Rauhala contributed to this report.


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Vocal performing class for ages 6 and up.
Instruction of proper baton, hoop, flag, ribbon etc…twirling and field corps technique.
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TOP SPOTS TO BIKE: MÁLAGA, Dancing in the streets, at Feria time!
Málaga is more than a cheap flight option to get some winter sun in Southern Spain. With its Moorish influence in food and architecture, its bullfights, a museum celebrating the birth place of Picasso and a premiership football team, it offers the visitor the tang of real Andalusian Spain mixed with beach life and a lot of Sol especially in fiesta time.
Each year an estimated 8.5 million tourists visit the Costa del Sol - 35% of these land at Malaga's Pablo Picasso airport and most head straight to the beaches at the package holidayers Mecca of Tormelinos, Benidorm and Marbella. But just a few minutes away you're in for a shock, as Malaga's city centre is exceedingly Spanish and surprisingly untouched by the influence of the coastline visitors.
Compact and easily reached from the airport (the electric train costs 1euro) it sits by the sea side harbour and is a wonderful romantic warren of interconnecting streets full of interesting shops, patisseries selling sticky honeyed sweets, the strong smell of morning coffee from cafes and men hawking salted almonds by the paper cupful from small stalls.
Ancient roots secure this city with an exciting past and I virtually stumbled onto a 2nd century B.C. roman amphitheatre sunning itself on a quiet back street behind the Alcazba, an exceptional Moorish Citadel perched over the town.
Originally settled by Phoenicians as a trading port and called Malaka in the 800 years before Christ, it went from hand to hand through battle, onto the Romans, Moors and then Christians. After the devastating expulsion of Moors from the city by the Christians in the 15thcentury, it declined, not helped by severe aerial bombardment in the Civil War and population persecution in Franco's day.
Recently, the city has worked hard to bring this somewhat grimy reputation into check with beautifying reformations to the port promenade and new paint jobs and in the bright sunlight which lit the crimson potted geraniums in so many iron wrought balconies, this bloody history seems far off. Especially since the whole city was on holiday for the annual August festival or Gran Feria de Malaga, and laughter, fun and dare I say copious drinking was foremost on everyone's minds. Spectacular fireworks display a festival of booming fire colour and light began this years Feria, and the city residents, the Malagueños did not let up in the nine days of festivities, which actually commemorates the 1487 recovery of the city from the Moors.
Having been to other European city's festivals I was completely unprepared for this explosion of joyous emotion of which music and dance rock the city. As the local bus drove towards Malaga's' bus terminal, we became stuck behind several strutting handsome Andalusian horses, their long flowing locks pined with scarlet ribbons and a senorita perched on the back of each. "Ah Bueno, they're going to the Feria" and literally the whole bus beamed appreciatively with a collective air of excitement rather than complaint at the lateness in time schedule.
The Feria is spread out through the city like a long jubilant winding Congo line, with the Bullring (Plaza de Toros), Real de la Feria (large showground for exhibiters and main music programs) and downtown streets, host to singers, dancers and of course drinkers. With fans tucked in bosoms and small shot glasses hanging from leather straps around necks, this city parties with a vengeance. No training is needed here for Malaga's 2016 award of European city of Culture, these people already have celebration down to an art and the beer and tinto verano (a dangerously refreshing mix of red wine and sparkling lemonade on ice) that flows during this week only adds to this joy de vivre.
Dwarfing the tidy apartments on either side and the sombrero sellers below is the massive a la Picasso styled entrance way to the Fair, framing the main shopping high street's (Calle Marquis de Lariolos) boutiques and large pedestrian marble throughway. Through this the crowds throng, past food and souvenir stalls to Plaza Constitucion at the end, resplendent with blue and white bunting bobbing in the summer sun and the dancers starting to warm up. Through the week, 172 musical artists are showcased in Malaga with concerts and free street performances and the roads are busy with traditional flamenco guitar tunes and impromptu singalongs in which locals gather clapping and cheering around these wandering minstrels.
If you have ever attended any wedding in which someone's older aunt or uncle attempted to dance misguidedly and on somewhat shaky legs to a popular pop piece well then you will be absolutely amazed at what the elderly community get up to here in broad daylight in public avenues and streets without the slightest hint of embarrassment.
I stood on the baking sidewalk in 37degree heat frankly open-mouthed at the large roving groups of grannies in low necked frilly dresses, flowers behind ears, strutting their stuff without pausing to breath. I would draw the comparison to the extremely Spanish alluring character of Carmen, if she were not a prostitute, but her lust for life is there in each and everyone of these skirt twirling, coquettish ladies. Unbridled and utterly appealing all with the enthusiastic Malagueños on the side walks clapping along and often unable to contain themselves, jumping into the gathering to join the reel. Street after street after street. And despite the Costa del Sol and Malaga's reputation as a haven for lager louts (mainly British and German it must be said) the only unsavouriness I saw in the weeklong drinking fest was the use of some back alleys as public loos.
As I was told it is the Spanish culture and family atmosphere here that prevents any fracas and if you know you might run into your grandparents and their friends also drinking in the bar down the street you aren't as willing to embarrass your self by indulging too much.
With all this dancing I literally had to walk into the shady gardens of the massive conglomerate Cathedral and connecting Iglesia Del Sagrario to escape the throng. An interesting construction with some appealing lifelike sculptures, it is very close to the new (and wonderfully stocked) Museo Picasso (its 2004 fanfare opening was attended by King Juan). Malaga also has some lovely local beaches, plazas, promenades and view points (notably the Gibralfaro Castle, which has a nice café terrace). But the nicest way to spend the evening before your evening meal is to stroll in the cool with the Malagueños in the Paseo del Parque, a Mediterranean delight of overhanging palms.
However sight seeing wasn't on the agenda for this week, although shopping could have been as several shops stocking bright polka dotted dancers dresses were doing booming trade, I was dragged back for another drink of the clear local wine, Cartojal and more tapas.
Tapas, good everywhere in Spain is excellent in its home of Andalusia. A tradition of placing a piece of bread over the wine glass to keep flies off soon developed into placing small titbits of food on it as well, olives, gherkins.. Now if you imbibe at a bar or café except anything from soft crusty bread laden with mountain cured ham, several pink prawns with sharp green olives, anchovies on tomato, potato chips and cashews. The list and permutations are endless and different with each drink. You could spoil your supper but you would have lots of time to do that as the Spanish only sit down to eat after the rest of Europe is contemplating bedtime.
When to go: Malaga's fair is in August – beginning generally around the 17th - 24th. This is high season in Spain and so one should book hotels in advance and bring sunscreen, it is hot and the sun powerful.
Travelling: Special bus services are usually laid on for the Feria with one trip costing one euro and a Tarjeta Feria (Fair Card) giving you several trips (with some free) for reasonable prices. For those travelling from Canada, there are weekly flights with Air Transaat to Malaga from Montreal and other hubs.
Website Info: Further information on coming events and accommodation the websites www.andalucia.com and www.spaintour.com are quite helpful. www.CyclingCountry.com runs bike tours in Andalucia mixing the great terrain for road biking, training with these great aspects of Andalucian culture!


text:
Q: Android layouts under subfolders Is it possible to create subfolders under res/layout and place the layout XML files there so that one can call a view like setContentView(R.layout.questions.create); or setContentView(R.layout.questions/create); ?

A: From my tests, no.
You might want to consider a naming convention:

*

*questions_create

*questions_list

*answers_list

Or, investigate Android library projects: http://androidblogger.blogspot.com/2010/09/android-library-projects.html - seems pretty good to add more structure.

redpajama_set_name: RedPajamaStackExchange


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I recently stayed at the Wagga RSL Club Motel 2 bedroom apartment and had an excellent stay. Our family was there to see our son march out from Kapooka. I was looking for more than a motel room so as to spend quality time with our son during his leave. I am an accommodation manager and I could not fault anything with this apartment. It was spotlessly clean and the beds very very comfy!! Convenience of RSL next door was a bonus. I would definitely recommend this apartment!
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text:
Kitakyushu will host Artistic and Rhythmic Gymnastics World Championships in 2021
LAUSANNE (SUI), FIG Office, 8 November 2020
The International Gymnastics Federation (FIG) is delighted to announce that the city of Kitakyushu in Japan will hold both the 50th Artistic Gymnastics World Championships and the 38th Rhythmic Gymnastics World Championships in October 2021.
The FIG Executive Committee has entrusted the Japan Gymnastics Association (JGA) with the organisation of the two back-to-back World Championships. This dual allocation comes after the decision by the Danish Gymnastics Federation in July to withdraw from hosting the 2021 Artistic Gymnastics World Championships in Copenhagen.
The Artistic gymnasts will kick off what promises to be a vibrant fortnight in the Japanese city. The Kitakyushu General Gymnasium will be the venue as they vie for world titles; afterwards, the West Japan Exhibition Centre will stage the Rhythmic competitions. The exact dates of the two events will be confirmed soon.
Although Japan has already welcomed both the Artistic Gymnastics World Championships and the Rhythmic Gymnastics World Championships, this will be the first time that Kitakyushu hosts a world-class Gymnastics event.
This city of almost one million, located on the island of Kyushu, is counting on the powerful appeal of the sport to bring a new vitality to the region, which experienced rapid economic growth between 1960 and 1980.
FIG President Morinari Watanabe commented: "Kitakyushu, the city where I was born, was a prosperous city thanks to steelworks until forty years ago. However, it now has the oldest population of any city in Japan. From a steel city, it has become a top-class city promoting the United Nations' Sustainable Development Goals.
"This time, we are taking on the challenge of supporting economic activity and promoting the Sustainable Development Goals through sports. We are happy and proud that our Gymnastics family can take on the challenge of using sport as a tool for urban regeneration," he added.
After the success of the Rhythmic Worlds in Mie in 2009 and the Artistic Worlds in Tokyo in 2011, the JGA is ready to host both events again despite the uncertainties resulting from the current COVID-19 pandemic.
"As a post-Olympic legacy, these World Championships are a great opportunity to continue the promotion and development of Gymnastics in Japan. If we can show that the World Championships can be held in these difficult circumstances, we believe that it will act as a beacon of hope for all sports," said JGA President Hidenori Futagi.
How the health situation will be in one year's time remains a big question. Special protocols will be drawn up and adjusted according to the reality of the risks next year.


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

Topological semimetals with  quadratic band touching (QBT) in two dimensions constitute    examples of gapless band structures protected by point group and time reversal symmetries \cite{FradkinBook,Sun}. Microscopic  models exhibiting  QBT  have been proposed and studied on the checkerboard and kagome lattices \cite{Sun,Liu2010,Uebelacker2011,Dora2014}. Unlike Dirac points in   graphene, two-dimensional QBT points have a nonvanishing  density of states  and their  effective action  is scale invariant with dynamical exponent $z=2$ \cite{FradkinBook}. This makes the QBT unstable  against   weak short-range  interactions and leads to phase transitions where at least one symmetry is spontaneously broken. As a consequence, anomalous quantum Hall and nematic semimetal phases  were predicted based on a perturbative renormalization group (RG) approach and mean-field theory \cite{Sun}, and  were recently   investigated in  numerical studies \cite{Sur2018,Zeng2018}.  Experimental realizations of QBT systems  in optical lattices have also been discussed \cite{Olschlager2012,Sun2012,Li2016}.

In this work we consider a (pseudo-)spin-$1/2$ fermionic model where a single spin-down fermion  interacts with   a  QBT system  of majority, spin-up fermions. This limit of extreme population imbalance  has received considerable attention in the context of cold atomic realizations of  Fermi polarons \cite{Massignan2014,Zollner2011,Mathy2011,Parish2011,Klawunn2011,Schmidt2012}, where mobile impurity atoms are dressed by   particle-hole excitations of the Fermi gas in which they are immersed.  The quasiparticle properties of Fermi polarons have been measured using   radio-frequency spectroscopy  \cite{SchirotzekPRL2009,KoschorreckNature2012,KohstallNature2012,Scazza2017}. Beyond the conventional polaron picture,   mobile impurities can   probe exotic properties of many-body systems such as  topological phase transitions  \cite{Grusdt2016,Camacho2019,Qin2019,Grusdt2019} and quasiparticle breakdown associated with  quantum criticality  \cite{Caracanhas2013,Punk2013,Pereira,yan2019bose}.

In Ref. \cite{Pereira},   the fate of a polaron in a QBT system was shown to depend on the particle-hole asymmetry of the band structure. If the effective mass of the upper band (above the QBT point) is larger than that of the lower band, a  repulsive $s$-wave impurity-fermion interaction decreases logarithmically with decreasing energy scale, giving rise to a marginal Fermi polaron. On the other hand, if the lower band has   larger effective mass, the effective interaction increases at low energies, driving  the quasiparticle weight to zero and bringing about  an emergent orthogonality catastrophe   \cite{Pereira}.

The purpose of this paper is twofold: First, we generalize the  model  of Ref. \cite{Pereira} to include a long-range spin exchange interaction between the mobile impurity and the majority fermions. The motivation comes from dipolar quantum gases \cite{Lahaye2009}, in which   spin exchange has been demonstrated experimentally \cite{Yan2013,Hazzard2014}. In these systems, the spatial anisotropy of the dipolar interaction can be controlled by varying the direction of the molecular electric  dipole  moments.  We show that in the low-energy limit the anisotropic spin exchange generates an impurity-fermion interaction that locally breaks point group symmetries. This modifies the renormalization group flow of the effective couplings in the quantum impurity model. We find a regime in which a bare repulsive interaction    becomes effectively attractive at low energies. Second, we study the formation of bound states in analogy with  the corresponding phenomenon  in  two-dimensional Fermi gases with attractive   interactions \cite{Zollner2011,Mathy2011,Parish2011,Klawunn2011,Schmidt2012}.   We find that   the spectrum of an impurity coupled to a QBT system can exhibit zero, one or two bound states depending on the  relative strength of the $s$-wave contact interaction and the symmetry-breaking interaction due to   anisotropic   exchange. In particular, for an attractive  $s$-wave  interaction and no anisotropic   exchange, there are two bound states which become degenerate   for vanishing total momentum. Turning on a small anisotropic interaction, the degeneracy point can move to  finite momenta along specific directions determined by the QBT Hamiltonian.

The remainder of the paper  is organized as follows: In Sec. \ref{model}, we present the microscopic model on the checkerboard lattice and the effective field theory in the continuum limit. In Sec. \ref{sec:RG}, we analyze the interacting model  using a  perturbative RG approach, which reveals the existence of a crossover regime where the effective coupling  changes sign. In Sec. \ref{sec:spectral}, we calculate the two-particle propagator and the associated pair spectral function in the ladder approximation, and  discuss  the different regimes for the formation of bound states. Our concluding remarks can be found in Sec. \ref{sec:conclusion}. The Appendix  contains   expressions for functions that appear in the RG equations  and some discussion about the two-body problem with one particle near the QBT.

\section{Model\label{model}}
We start with the model
\begin{eqnarray}
H&=&-\sum_{\langle ij\rangle}t_{ij}(c^\dagger_{i\uparrow}c^{\phantom\dagger}_{j\uparrow}+c^\dagger_{i\downarrow}c^{\phantom\dagger}_{j\downarrow})+U\sum_{i}n_{i\uparrow}n_{i\downarrow}\nonumber\\
&&+\frac{J_\perp}4\sum_{  i\neq j}V_{ij}(S_i^+S_j^-+S_i^-S_j^+).\label{Hlattice}
\end{eqnarray}
Here, $c^\dagger_{j\alpha}$ creates a fermion  at site $j$ in one of two internal states, labeled by $\alpha=\uparrow,\downarrow$, and $n_{j\alpha}=c^\dagger_{j\alpha}c^{\phantom\dagger}_{j\alpha}$.  The hopping parameters $t_{ij}$ are defined on the checkerboard lattice. While the  nearest-neighbor hopping $t$ is uniform,   the next-nearest-neighbor hopping is either $t'$ or $t''$ depending on the sublattice and the direction of the link, as illustrated  in Fig. \ref{rededispersao}. For two next-nearest-neighbor sites in the A (B) sublattice, the hopping parameter is $t'$ along the $x$  ($y$) direction, but $t''$ along the $y$ ($x$) direction. In addition to the on-site Hubbard repulsion $U>0$, we consider a dipolar exchange interaction    \cite{Gorshkov2011,Zou2017} written in terms of   spin  operators $S_j^+=c^\dagger_{j\uparrow}c^{\phantom\dagger}_{j\downarrow}$ and $S_j^-=c^\dagger_{j\downarrow}c^{\phantom\dagger}_{j\uparrow}$.  The geometrical factor\begin{equation}
V_{ij}= \frac{1-3(\hat{\mathbf d}\cdot \hat {\mathbf r}_{ij})^2}{|\mathbf r_{ij}|^3}
\end{equation}
depends on the relative position  $\mathbf r_{ij}=\mathbf r_i-\mathbf r_j$ between sites. Here $\hat{\mathbf d}$ is a unit vector parallel to   the quantization axis,   set by  the direction of     the  polarized dipole moments \cite{Gorshkov2011}.  This type of exchange interaction  was  realized   using two rotational states of  polar molecules in optical lattices \cite{Yan2013}.  In terms of the angles shown in  Fig. \ref{rededispersao}, we can write $\hat{\mathbf d}\cdot \hat {\mathbf r}_{ij}=\sin\theta\cos(\phi-\varphi_{ij})$, where $\theta$ and $\phi$ are the angles of the $\mathbf d$ vector and $\varphi_{ij}$ is the angle between $\mathbf r_{ij}$ and the $x$ axis. Note that for  $\theta\neq0,\pi$ the  strength of the dipolar exchange interaction depends on the direction of $\mathbf r_{ij}$.

\begin{figure}[t]
{\includegraphics[width=0.7\columnwidth]{fig1.pdf}}
\caption{Checkerboard lattice.  Solid lines represent the nearest-neighbor hopping $t$ between sites in sublattice A (red) and B (green). Dashed and dotted lines represent next-nearest-neighbor hopping $t'$ and $t''$, respectively. The spin exchange interaction depends on the direction of   the dipolar moment $\mathbf d$, parametrized by the polar angle $\theta$  (with respect to the $z$ axis, perpendicular to the lattice plane) and the azimuthal angle $\phi$ (measured from the $x$ axis). A vector $\mathbf r_{ij}$ connecting two lattice sites forms an angle $\varphi_{ij}$ with the $x$ axis.}\label{rededispersao}
\end{figure}

In the noninteracting case, $U=J_\perp=0$, we can diagonalize the Hamiltonian using the mode expansion \begin{eqnarray}
c_{j\alpha}&=&\left\{\begin{array}{ll}\frac1{\sqrt {N_s}}\sum_{\mathbf k}a_{\mathbf k\alpha}e^{i\mathbf k\cdot \mathbf R_j},&\quad j\in\textrm{A}\\
\frac1{\sqrt {N_s}}\sum_{\mathbf k}b_{\mathbf k\alpha}e^{i\mathbf k\cdot (\mathbf R_j+\boldsymbol\delta)},&\quad j\in\textrm{B}\end{array}\right.,
\end{eqnarray}
where $\mathbf R_j$ are positions on the square lattice with  lattice spacing set equal to $1$,  $N_s$ is the number of unit cells of the checkerboard lattice, and $\boldsymbol \delta=(\hat{\mathbf x}+\hat{\mathbf y})/2$ connects two sites in the same unit cell. The noninteracting Hamiltonian has the form
$H_0=\sum_{\mathbf k,\alpha}c^\dagger_{\mathbf k\alpha}\mathcal{H}_0(\mathbf k)c^{\phantom\dagger}_{\mathbf k\alpha}$, with \begin{eqnarray}
\mathcal H_0(\mathbf k)&=& -(t'+t'')(\cos k_x+\cos k_y)\openone \nonumber\\
&&-(t'-t'')(\cos k_x-\cos k_y)\sigma^z\nonumber\\
&&-4t\cos(k_x/2)\cos(k_y/2)\sigma^x.
\end{eqnarray}
Here $c_{\mathbf k\alpha}=(a_{\mathbf k \alpha},b_{\mathbf k \alpha})$ is a two-component spinor and $\sigma^{x},\sigma^{y},\sigma^{z}$ are Pauli matrices acting in the sublattice space. The noninteracting Hamiltonian has a    C$_4$ rotational symmetry  corresponding to $\sigma^y\mathcal H_0(k_x,k_y)\sigma^y=\mathcal H_0(k_y,2\pi-k_x)$. In addition, $H_0$ is invariant under complex conjugation, equivalent to time reversal  in  sectors of the Fock space with fixed   $N_\uparrow=\sum_{j }c^\dagger_{j\uparrow}c^{\phantom\dagger}_{j\uparrow}$ and $N_\downarrow=\sum_j c^\dagger_{j\downarrow}c^{\phantom\dagger}_{j\downarrow}$. For $|t'+t''|<|t|$ and $|t'+t''|<|t'-t''|$, the band structure has a  QBT point at the corner of the Brillouin zone, $\mathbf Q=(\pi,\pi)$ \cite{Sun}, as illustrated  in Fig. \ref{bandstructure}. This  QBT point does not require fine tuning, since it carries  Berry phase $\pm 2\pi $   and is protected by C$_4$ and time reversal symmetries.

\begin{figure}[t]
{\includegraphics[width=0.7\columnwidth]{QBTbands.pdf}}
\caption{Band structure for the noninteracting checkerboard lattice model showing the quadratic band touching at $\mathbf Q=(\pi,\pi)$. Here we set $t'=0.6t$ and $t''=-0.4t$.}\label{bandstructure}
\end{figure}

Let us focus on the single-impurity model with $N_{\uparrow}=N_s$ and $N_\downarrow=1$ in the thermodynamic limit $N_s\to\infty$. In this case, the Fermi level of the spin-up (majority) fermions lies at the QBT point. We can describe their low-energy excitations  by expanding around momentum $\mathbf Q$. Hereafter we assume   $t''<0$ and $t=t'-t''>0$, in which case the dispersion around the QBT point becomes isotropic in the continuum limit \cite{Sun,Pereira}. By contrast, the low-energy limit for the impurity is obtained by expanding around the bottom of the lower band, at $\mathbf k=0$. The non-interacting Hamiltonian in the continuum limit becomes, up to a constant, \begin{equation}
H_0=\int d^2r \left[\Psi^\dagger(\mathbf r) h_0(\mathbf r)\Psi(\mathbf r)-d^\dagger(\mathbf r)\frac{\nabla^2}{2M}d(\mathbf r)\right],\label{H0cont}
\end{equation}
where $\Psi(\mathbf r)=(\psi_A(\mathbf r),\psi_B(\mathbf r))^t$ is the two-component spinor associated with  the majority fermions and $d(\mathbf r)$ is the mobile impurity field with effective mass $M=(2t')^{-1}$. The operator \begin{eqnarray}
h_0(\mathbf r)&=&\frac{m_+-m_-}{4m_+m_-}\openone \nabla^2+\nonumber\\
&&+\frac{m_++m_-}{4m_+m_-}\left[\sigma^z(\partial_x^2-\partial_y^2)+2\sigma^x\partial_x\partial_y\right]
\end{eqnarray}
involves the effective masses  in the vicinity of the QBT point:  $m_+=[2(t-t')]^{-1}$ and   $m_-=(2t')^{-1}$ for the upper and lower bands, respectively.

We now switch on the interactions in the weak coupling regime $U,|J_\perp|\ll t$. The interacting Hamiltonian in the continuum limit has the form $H=H_0+H_{int}$, with $H_0$ given in Eq. (\ref{H0cont}) and the impurity-fermion interaction given by\begin{equation}
H_{int}=\frac{4\pi}{m_+}\int d^2r \, \Psi^\dagger(\mathbf r)(g\openone +g_\perp\sigma^x) \Psi(\mathbf r)d^\dagger(\mathbf r)d(\mathbf r),\label{Hint}
\end{equation}
where we define the dimensionless couplings
\begin{eqnarray}
g&=&\frac{m_+}{8\pi}\left[U-\kappa J_\perp \left(\frac{3}2\sin^2\theta-1\right)\right],\nonumber\\
g_\perp&=&-\frac{3m_+}{4\pi}\kappa_\perp J_\perp \sin^2\theta\sin(2\phi).\label{gamma1}
\end{eqnarray}
The latter stem from the Fourier transform of the on-site   and dipolar   exchange interactions and  contain the constants
\begin{eqnarray}
\kappa&=&\frac32\zeta(3)-2\sum_{m=1}^\infty\sum_{n=1}^\infty\frac{(-1)^{m+n}}{(m^2+n^2)^{3/2}}\approx 1.322, \\
\kappa_\perp&=&\sum_{m=0}^{\infty}\sum_{n=0}^{\infty}\frac{(-1)^{m+n}\left(m+\frac12\right)\left(n+\frac12\right)}{\left[\left(m+\frac12\right)^2+\left(n+\frac12\right)^2\right]^{5/2}}\approx 1.312,\nonumber
\end{eqnarray}
where $\zeta(s)$ is the Riemann zeta function.

We interpret   $g$  in Eq. (\ref{Hint}) as the usual $s$-wave scattering amplitude between the impurity and the majority fermions, whereas the new interaction $g_\perp$ scatters fermions between different sublattice states.
Note that $g_\perp$ depends on the spatial anisotropy of the exchange interaction, and it vanishes when  the dipolar moment is polarized along the $z$ axis.
In fact, the    $g_\perp$ interaction  breaks the C$_4$ symmetry, which in the continuum limit  becomes $\Psi(x,y)\mapsto \sigma^y\Psi(y,-x)$.   Importantly, both $g$ and $g_\perp$ are local interactions at  the position of the   mobile impurity and there are no interactions between majority fermions in the bulk. Thus, the single-impurity model allows us to explore the effects of a local symmetry-breaking interaction without destabilizing the QBT.

\section{Renormalization group analysis\label{sec:RG}}

Short-range interactions are known to be marginal perturbations of two-dimensional semimetals with a QBT \cite{Sun,Murray2014,Pereira}. To treat the interactions  within perturbation theory,  we introduce  the   impurity Green's function     \begin{equation}
G_d(\mathbf r,\tau)=-\langle T_\tau d(\mathbf r,\tau)d^\dagger(\mathbf 0,0)\rangle,
\end{equation}
where  $d(\mathbf r,\tau)=e^{H\tau}d(\mathbf r)e^{-H\tau}$ is the impurity field  evolved in imaginary time, $T_\tau$ denotes time ordering with respect to $\tau$,  and the expectation value is calculated  in the ground state   with $N_\downarrow=0$.  To zeroth order in the interactions, we have the noninteracting Green's function in momentum-frequency domain:
\begin{equation}
G^{(0)}_d(\mathbf k,i\nu)=\frac1{i\nu-k^2/(2M)}.
\end{equation}
For the majority  fermions, we define  the  matrix Green's function
\begin{equation}
\mathbbm G=\left(\begin{array}{cc}
\mathcal G_{AA}&\mathcal G_{AB}\\
\mathcal G_{BA}&\mathcal G_{BB}
\end{array}\right),
\end{equation}
with components
\begin{equation}
\mathcal G_{ll'}(\mathbf r,\tau)=- \langle T_\tau \psi^{\phantom\dagger}_l(\mathbf r,\tau) \psi^{\dagger}_{l'}(\mathbf 0,0)\rangle,
\end{equation}
where    $l=A, B$ is the sublattice index.
The Fourier-transformed noninteracting Green's function reads
\begin{eqnarray}
\mathcal G^{(0)}_{ll'}(\mathbf p,i\nu)&=&\left\{[i\omega\openone-\mathcal H_0(\mathbf Q+\mathbf p)]^{-1}\right\}_{ll'}\nonumber\\
&=&\sum_{\lambda=\pm}\frac{U_{l\lambda}(\mathbf p)U_{l'\lambda}(\mathbf p)}{i\nu-\lambda p^2/(2m_\lambda)}.
\end{eqnarray}
Here  $U_{l\lambda}(\mathbf p)$, with $\lambda=\pm$ the band index,  are the matrix elements  of the unitary  transformation that diagonalizes $h_0(\mathbf p)=\mathcal H_0(\mathbf Q+\mathbf p)$  with $|\mathbf p|\ll1$.  Due to the Berry phase associated with the QBT, $U(\mathbf p)$ depends on the angle $\varphi_{\mathbf p}=\arctan(p_y/p_x)$, in the form  \begin{equation}
U(\mathbf p)=U(\varphi_{\mathbf p})=\left(\begin{array}{cc}
\sin\varphi_{\mathbf p}&\cos\varphi_{\mathbf p}\\
-\cos\varphi_{\mathbf p}&\sin\varphi_{\mathbf p}
\end{array}\right).\label{Umatrix}
\end{equation}

We analyze the effects of the impurity-fermion interaction using a weak-coupling Wilsonian RG approach \cite{Shankar,Cardy1996}. We derive the RG equations for the coupling constants at one-loop level and for the impurity effective mass and quasiparticle weight at two-loop level by integrating out high-energy fermion states in the  momentum shell   $\Lambda(1-d\ell)<p^2/(2m_+)<\Lambda$, where $\Lambda$ is the ultraviolet  cutoff and $d\ell \ll 1$ is the infinitesimal parameter in the RG step. For instance, the diagrams that contribute to the renormalization of the interaction vertex   are shown in Fig. \ref{vertex}.  We obtain the set of coupled RG equations:
 \begin{eqnarray}
   \frac{dg}{d\ell}&=& \frac{\left(\mu_--\mu_+\right)Z_d}{m_+}(g^2+g_{\perp}^2),\nonumber\ \\
  \frac{dg_{\perp}}{d\ell}&=& \frac{2(\mu_--\mu_+)Z_d }{m_+}gg_{\perp},\label{RGeqns}\\
   \frac{dZ_d}{d\ell}&=&-\frac{2\mu_-\mu_+Z_d}{m_+}\left[
   g^2 F_1(r_+,r_-)+g_{\perp}^2 F_2(r_+,r_-)\right],\nonumber\\
   \frac{dM}{d\ell}&=&\frac{2(\mu_-\mu_+)^{3/2}}{m_+}\left[
   g^2 F_3(r_+,r_-)+g_{ \perp}^2 F_4(r_+,r_-)\right],\nonumber
 \end{eqnarray}
where $Z_d$ is the impurity quasiparticle weight, $\mu_\pm=m_\pm M/(M+m_\pm)$ are reduced masses, and $r_\pm =m_\pm/M$ are mass ratios.
The functions $F_i(r_+,r_-)$, with $i=1,\dots,4$,  are given  in terms of  integrals in Appendix \ref{AppFunctions} and return positive values of order 1. Note that  bulk properties, such as the effective   masses $m_+$ and $m_-$ for the majority fermions, are not renormalized in the single-impurity problem.

\begin{figure}[t]
{\includegraphics[width=0.85\columnwidth]{fig2.pdf}}
\caption{Effective interaction vertex at tree level ($\Gamma^{(1)}$) and at one-loop level ($\Gamma^{(2)}$). Solid lines represent the bare propagator for majority fermions, while dashed lines represent the  impurity propagator. The matrices in the interaction vertex act on the fermion sublattice degree of freedom.}\label{vertex}
\end{figure}

The case $g>0$ and $g_\perp=0$ was studied in Ref. \cite{Pereira}. In this case, $g$ can be marginally relevant or irrelevant   depending on the difference between the effective masses $m_+$ and $m_-$. The reason is that  the two one-loop diagrams in the vertex renormalization (see  Fig. \ref{vertex}) have opposite signs.  For $m_->m_+$,   the diagram with a   hole propagator in the loop dominates and  the repulsive impurity-fermion interaction   flows to strong coupling. Ultimately, the quasiparticle weight $Z_d$ vanishes and  the effective impurity mass $M$ diverges logarithmically in the low-energy limit \cite{Pereira}.

\begin{figure}[t]
\centering
\includegraphics[width=0.9\columnwidth]{fig3.pdf}
\caption{Renormalization group  flow of the couplings in the single-impurity model with $m_-<m_+$. In the crossover region $|g|<|g_\perp|$ (orange), an initially repulsive $s$-wave scattering amplitude $g>0$ can change sign and become   attractive.}\label{rgflow1}
\end{figure}

Here we are interested in the case $m_-<m_+$, in which the diagram with a fermionic particle propagator in the loop dominates the vertex renormalization. The RG flow diagram for the couplings  $g$ and $g_\perp$ in Fig. \ref{rgflow1} reveals three regions with qualitatively different behavior. For $|g_\perp|<g$ (blue region in Fig. \ref{rgflow1}), the interaction is marginally irrelevant. As a result, in the low-energy limit the impurity decouples from the fermionic bath and one recovers Fermi polaron behavior with logarithmic corrections \cite{Pereira}. When we start off with an attractive interaction in the regime   $g<-|g_\perp|$ (green region in Fig. \ref{rgflow1}), the system exhibits monotonic flow to strong coupling.  Finally and most remarkably, for $|g|<|g_\perp|$ (orange region in Fig. \ref{rgflow1}), we observe a crossover from weak repulsive interaction  to strong attractive interaction, $g<0$. Our goal in the following will be to analyze the fate of the impurity in the latter two regions.

\section{Pair spectral function\label{sec:spectral}}

The flow of the effective couplings to strong attraction signals the formation of bound states between the impurity and a majority fermion. In two dimensions, at least one bound state exists in the two-body problem for an arbitrarily weak attractive interaction \cite{Mathy2011,Parish2011,Klawunn2011,Schmidt2012}.   To investigate the presence of  bound states, we consider  the pair creation  operator\begin{equation}
P^\dagger(\mathbf r_j)=c^\dagger_{j\uparrow}c^\dagger_{j\downarrow}.
\end{equation}
We then define the two-particle propagator as a matrix in sublattice space, with components\begin{eqnarray}
\Pi_{ll'}(\mathbf R,\tau)&=&-(-1)^{s_l+s_{l'}}2\langle T_\tau P(\mathbf R+s_l\boldsymbol\delta,\tau)
P^\dagger(s_{l'} \boldsymbol\delta,0)\rangle,\nonumber\\ \label{2pprop}
\end{eqnarray}
where   $\mathbf R$ is a position vector in sublattice A and   $s_A=0$, $s_B=1$. At low energies, we can work with   the two-particle propagator in the continuum limit:
\begin{equation}
\Pi_{ll'}(\mathbf r,\tau)=-\langle T_\tau \psi_l^{\phantom\dagger}(\mathbf r,\tau)d(\mathbf r,\tau)d^\dagger(\mathbf 0,0)\psi_{l'}^\dagger(\mathbf 0,0)\rangle,
\end{equation}
where the factor of $(-1)^{s_l+s_{l'}}2$ in Eq. (\ref{2pprop}) gets cancelled in the projection of $c_{j\downarrow}$ onto the impurity field. Taking  the Fourier transform, \begin{equation}
\Pi_{ll'}(\mathbf q,i\omega)=\int  d^2rd\tau\, e^{i\omega\tau}e^{-i\mathbf q\cdot \mathbf r}\, \Pi_{ll'}(\mathbf r,\tau),
\end{equation}
and the analytic continuation $i\omega\to \omega+i0^+$, we define the pair  spectral function \begin{equation}
\mathcal A_{\textrm{pair}}(\mathbf q,\omega)=-2\textrm{Im}\{\textrm{Tr}[\Pi(\mathbf q,\omega+i0^+)]\}.
\end{equation}
When interpreting the result for $\mathcal A_{\textrm{pair}}(\mathbf q,\omega)$ in the continuum limit in terms of the original lattice model, we must recall that zero energy corresponds to the impurity at the bottom of the lower band and the spin-up fermion at the QBT point.

 \begin{figure}[t]
\centering
\includegraphics[width=.95\columnwidth]{fig4.pdf}
\caption{Feynman diagrams included in the ladder approximation for the two-particle propagator.  The convention for the interaction vextex  and for impurity and fermion propagators is the same as in Fig. \ref{vertex}. }\label{ladder}
\end{figure}

We calculate the two-particle propagator in the ladder   approximation \cite{Mahan,Massignan2014}. This approximation is justified because, according to the RG analysis in Sec. \ref{sec:RG},  for  $m_-<m_+$ the perturbative expansion is dominated by  diagrams with a particle propagator in the   loops. The ladder series is illustrated in Fig. \ref{ladder}.
The diagrams involve the bare two-particle propagator\begin{eqnarray}
\Pi_0(\mathbf{q},i\omega)&=& \int \frac{d^2pd\nu}{(2\pi)^3} \mathbb G^{(0)}(\mathbf p+\mathbf q,i\omega+i\nu) G^{(0)}_{d}(-\mathbf p,-i\nu)\nonumber\\
&=&\frac{\mu_+}{4\pi}\left\{ \log\left(\frac{W-i\omega}{\Omega(q)-i\omega}\right)\openone\right.\nonumber \\
  & &-\left[ 1+ \frac{Mq^2-2iM^2\omega}{\mu_+q^2}\log\left(\frac{i\omega-\Omega(q)}{  i\omega-\frac{q^2}{2M} }\right) \right] \nonumber\\
 & & \times \left[\cos{(2\varphi_{\mathbf q})}\sigma^z+\sin{(2\varphi_{\mathbf q})}\sigma^x  \right]\Big\},\label{Iq}
\end{eqnarray}
where $W$ is a high-energy cutoff and
 $\Omega(q) = \frac{q^2}{2(M+m_+)}$ is the lower threshold of the two-particle  continuum in the absence of interactions, corresponding to the minimum energy for   one fermion and the impurity carrying total momentum $\mathbf q$.  Note that $\Pi_0(\mathbf{q},i\omega)$ contains ``$d$-wave'' terms with nontrivial dependence on the angle $\varphi_{\mathbf q}$.

The two-particle propagator  is determined by   the Bethe-Salpeter equation in the ladder approximation
\begin{equation}
\Pi(\mathbf q,i\omega)=\Pi_0(\mathbf q,i\omega)\left[\openone +(g\openone +g_\perp\sigma^x)\Pi(\mathbf q,i\omega)\right],
\end{equation}
which we solve by summing up a   geometric series of matrices.
 We can identify   bound states by searching for  poles of $\Pi(\mathbf{q},\omega)$  below the two-particle continuum. We find two possible bound state dispersion relations, $E^{\pm}_{bs}(\mathbf q)$, given by the solutions to    \begin{eqnarray}
  E^{\pm}_{bs}&=&\frac{\Omega(q)}{1-e^{X_\pm(\mathbf q,E^{\pm}_{bs})}} +\frac{W}{1- e^{-X_\pm(\mathbf q,E_{bs}^\pm)}}, \label{Enbs}
  \end{eqnarray}
  where \begin{eqnarray}
 X_{\pm}(\mathbf{q},E_{bs}^\pm)&=&\frac{(1+r_+)g}{g^2-g_\perp^2}  \pm \frac{1+r_+}{g^2-g_\perp^2}    \nonumber\\
 &&\times \Bigg\{ \left[|g_\perp|-\frac{(g^2-g_\perp^2)}{1+r_+}\,C\left(\frac{q^2/(2M)}{-E^\pm_{bs}}\right)\right]^2   \nonumber\\
 && \qquad +\frac{2|g_\perp|(g^2-g_\perp^2)}{1+r_+}\,C\left(\frac{q^2/(2M)}{-E^\pm_{bs}}\right)\nonumber\\
 &&\qquad\times[1-\textrm{sgn}(g_\perp)\sin(2\varphi_{\mathbf q})]\Bigg\}^{1/2}.\label{epmbs}
\end{eqnarray}
The function $C(x)$ appearing in Eq. (\ref{epmbs}) is given by
\begin{eqnarray}
C(  x)&=&-1+\frac{(1+r_+)(1+x)}{r_+x}\ln\left(\frac{1+x}{1+\frac{x}{1+r_+}}\right) , \label{dwav}
\end{eqnarray}
and is such that  $C(x)\geq 0$ $\forall x\geq0$.

 \begin{figure}[b]
\centering
\includegraphics[width=0.95\columnwidth]{fig5.pdf}
\caption{Pair spectral function $\mathcal A_{\textrm{pair}}(\mathbf q,\omega)$ for    $g=0.1$, $g_\perp=-0.5$,  and $r_+=1.2$. In this case,    $|g|<|g_\perp|$ and   only one bound state appears  below the two-particle continuum.  Panel (a) shows $\mathcal A_{\textrm{pair}}(\mathbf q,\omega)$ as a function of $q$ and $\omega$ at fixed angle   $\varphi_{\mathbf q}=\pi/4$. Panels (b) and (c) show $\mathcal A_{\textrm{pair}}(\mathbf q,\omega)$ as a function of momentum at fixed $\omega=0$ and $\omega=0.03W$, respectively.  }\label{spectf1}
\end{figure}

For $q\to0$, the result simplifies as $C( x)\sim x\to 0$ and the angle-dependent terms in Eq. (\ref{epmbs}) vanish. In this case, $X_\pm(\mathbf q=0,E_{bs}^\pm)= (1+r_+)/(g\mp |g_\perp|)$ become constant. The  bound state solutions at $\mathbf q=0$, with energies \begin{equation}
E^\pm_{bs}(\mathbf q=0)=\frac{W}{1-\exp\left(-\frac{1+r_+}{g\mp |g_\perp|}\right)}<0,\label{binding}\end{equation}
exist   as long as $g\pm g_\perp<0$. Therefore, the criterion for the number of bound states at $\mathbf q=0$ matches the three regions depicted in Fig. \ref{rgflow1}. For $g>|g_\perp|$, corresponding to the regime of marginally irrelevant interactions, there are no bound states. We find one bound state with energy $E_{bs}^+$ in  the crossover regime $|g|<|g_\perp|$ and two bound states in the attraction-dominated  regime $g<-|g_\perp|$. For $g<0$ and $g_\perp=0$, the bound states are degenerate at $\mathbf q=0$.  Note also that at weak coupling, $|g|,|g_\perp|\ll1$, the binding energies $E^{\pm}_{bs}(0)\approx -W \exp\left(\frac{1+r_+}{g\mp |g_\perp|}\right)$  are exponentially small, as expected for marginal interactions.

For $g_\perp\neq0$ and $g<-|g_\perp|$,  the bound states     may become degenerate at   nonzero momenta $\mathbf q_0$ such that $X_{+}(\mathbf{q}_0,E_{bs})=X_{-}(\mathbf{q}_0,E_{bs})$. From Eqs. (\ref{Enbs}) and (\ref{epmbs}), we see that the degeneracy point happens along the directions where $\sin(2\varphi_{\mathbf q_0})=\textrm{sgn}(g_\perp)$,
i.e., for angles $\varphi_{\mathbf q_0}=\frac\pi4,\frac{5\pi}4$ for $g_\perp>0$ and $\varphi_{\mathbf q_0}=\frac{3\pi}4,\frac{7\pi}4$ for $g_\perp<0$. The value of $q_0$ is determined by the conditions
\begin{eqnarray}
E_{bs}(  q_0)&=&\frac{\Omega(q_0)}{1-e^{\frac{(1+r_+)g}{g^2-g_\perp^2} }} +\frac{W}{1- e^{-\frac{(1+r_+)g}{g^2-g_\perp^2} }},\\
C\left(\frac{q_0^2/(2M)}{-E_{bs}(q_0)}\right)&=&\frac{(1+r_+)|g_\perp|}{g^2-g_\perp^2}.
\end{eqnarray}

\begin{figure}[t]
\centering
\includegraphics[width=0.95\columnwidth]{fig6.pdf}
\caption{Same as Fig. \ref{spectf1} for    $g=-0.5$, $g_\perp=0.1$,  and $r_+=1.2$. In this case,   $g<-|g_\perp|$ and   there are two  bound states   below the continuum  at $\mathbf q=0$.  Note the touching of curves in panel (a), which is due to   the degeneracy of the bound states with momentum $\mathbf q_0\neq 0$ along the direction $\varphi_{\mathbf q}=\pi/4$. }\label{spectf2}
\end{figure}

Figures \ref{spectf1} and  \ref{spectf2} show    results for the   pair spectral function in the ladder approximation. The intensities are plotted in logarithmic scale and arbitrary units proportional to  $\ln[1+ A_{\textrm{pair}}(\mathbf q,\omega)/(\eta m_+)]$, with a small    broadening factor $\eta\sim 10^{-4}$. Figure  \ref{spectf1}  is representative of the crossover regime with $|g|<|g_\perp|$. Although the $s$-wave scattering amplitude $g>0$ is repulsive in this example, we do find a bound state below the two-particle continuum. This bound state originates from the effects of anisotropic exchange interaction encoded in $g_\perp$. On the other hand, in the attraction-dominated regime $g<-|g_\perp|$ illustrated by Fig.   \ref{spectf2}, we find two bound states  at $\mathbf q=0$. These bound  states  become degenerate at a finite value of $q$ in the direction $\varphi_{\mathbf q}=\pi/4$, see the anticrossing in Fig. \ref{spectf2}(a). This dependence on $\varphi_{\mathbf q}$ is a manifestation of the unitary transformation in Eq. (\ref{Umatrix}), which is responsible for the nontrivial Berry phase of the QBT point.  Note that the bound state dispersions only exhibit a C$_2$ rotational symmetry,  consistent with the anisotropy of the dipolar exchange interaction in the  lattice model. This contrasts with the   isotropic  single-fermion and impurity dispersions, which account for the  rotational invariance of the edge of two-particle continuum seen in Figs. \ref{spectf1} and  \ref{spectf2}.

\begin{figure}[t]
\centering
\includegraphics[width=0.95\columnwidth]{fig7.pdf}
\caption{A-sublattice component $\mathcal A^A_{\textrm{pair}}(\mathbf q,\omega)$ of the pair spectral function   for    $g=-0.5$, $g_\perp=0$,  and $r_+=1.2$. Panel (a) shows the result as a function of $q$ and $\omega$ at fixed   $\varphi_{\mathbf q}=\pi/4$. The two bound states become degenerate as $q\to0$.  Panels (b) and (c), taken at fixed $\omega=0$ and $\omega=0.02W$, respectively, show that  the first (second) bound state  has vanishing weight in the A sublattice    for $\varphi_{\mathbf q}=0,\pi$ ($\varphi_{\mathbf q}=\pi/2,3\pi/2$). The angle dependence of the B-sublattice component can be obtained by a C$_4$ rotation of   plots (b) and (c).     }\label{spectf3}
\end{figure}

Finally, consider the case $g<0$ and $g_\perp=0$, which holds  for the standard attractive    Fermi Hubbard model without the dipolar   exchange interaction.  In this case, we are left with the rotationally invariant $g$ interaction. Nevertheless, the bound states can still show signatures of the $d$-wave character of the QBT. Figure \ref{spectf3} displays  the A-sublattice component of the pair spectral function, defined as $ \mathcal A^A_{\textrm{pair}}(\mathbf q,\omega)=-2\textrm{Im}\{\Pi_{AA}(\mathbf q,\omega+i0^+)\}$. In Fig. \ref{spectf3}(a), we see that the two bound states are degenerate at $\mathbf q=0$, but the degeneracy is lifted as $q$ increases and the second bound state eventually merges with the continuum. Moreover, figures \ref{spectf3}(b) and  \ref{spectf3}(c)  show that the bound state contributions to $ \mathcal A^A_{\textrm{pair}}(\mathbf q,\omega)$ have nodes as a function of   $\varphi_{\mathbf q}$.  The weight of the first bound state in the A sublattice vanishes for $\varphi_{\mathbf q}=0,\pi$, while for the second bound state it vanishes for $\varphi_{\mathbf q}=\pi/2,3\pi/2$. Along these four directions,  $ \mathcal A^A_{\textrm{pair}}(\mathbf q,\omega)$ shows only one bound state below the continuum at small $q$.  The location of the nodes is reversed for the  B-sublattice component  of the pair spectral function.  If we add   A and B components, we find that the full pair spectral function is symmetric under C$_4$ rotations, with two bound states in any direction for small $q$. To gain more intuition about the symmetry properties  of the bound states, in Appendix \ref{App2body} we   study the two-body problem of  an impurity interacting with a single particle near the QBT point, without the constraint of a completely filled lower band.

\section{Conclusion\label{sec:conclusion}}

We  studied  the interaction between a    mobile quantum impurity  and a bath of  majority  fermions whose Fermi level is tuned to a quadratic band touching point. The low-energy effective model contains an $s$-wave contact interaction $g$ and a rotational-symmetry-breaking  interaction $g_\perp$ which  can be generated by  dipolar spin  exchange. A renormalization group approach shows a regime in which a  repulsive  impurity-fermion interaction     becomes effectively attractive at low energies.
This happens because the dipolar spin exchange switches the fermion and the impurity positions, lowering the ground state energy. The amplitude of this process decreases with distance.
This situation leads to the formation of  bound states. The anisotropic momentum dependence of the bound states stems  from the combined  effects of the $g_\perp$ interaction  and the $d$-wave terms in the two-particle propagator.   In the  ladder approximation, we find   a single bound state for $|g|<|g_\perp|$ and two bound states for  $g<-|g_\perp|$, in agreement with the existence of different regimes in the renormalization group flow diagram.  At weak coupling, the binding energies are exponentially small in the coupling constants.

Higher body bound states, as trimers or tetramers, are not expected to have important contribution to the spectral functions discussed in this work, unless one considers the impurity to be substantially lighter than the fermions and considers the regime of strong interactions, where $p$-wave interactions between the fermions could develop. In addition, the presence of a Fermi sea usually tends to suppress the formation of higher body bound states due to the Pauli exclusion principle, requiring the impurity to be even lighter to allow those bound states \cite{naidon17}.
Our model could be realized with dipolar molecules in an optical checkerboard lattice.
It should be interesting to extend our results to a low but finite density of minority fermions, with potential implications for unconventional superconductivity in quadratic band touching systems \cite{Pawlak2015}.

\begin{acknowledgments}
We thank T. Enss for helpful discussions. This work is supported by FAPESP/CEPID, FAPEMIG, CNPq, INCT-IQ, and CAPES, in particular through programs CAPES-COFECUB (project 0899/2018) and CAPES-PrInt UFMG (M.C.O.A.). Research at IIP-UFRN is funded by Brazilian ministries MEC and MCTIC.
\end{acknowledgments}

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