the Perimeter spring/summer 2018 Remembering Stephen Hawking The riddle of the quantum Sphinx AI solves quantum challenges Taming the Langlands program Editor Natasha Waxman [email protected] Managing Editor Tenille Bonoguore Contributing Authors Tenille Bonoguore Erin Bow Mike Brown Dan Falk Colin Hunter Stephanie Keating Robert Spekkens Neil Turok Copy Editors Tenille Bonoguore Mike Brown Colin Hunter Stephanie Keating Sonya Walton Natasha Waxman Graphic Design Gabriela Secara Cover Illustration Center for Astrophysics / M. Weiss Photo Credits Adobe Stock Mitch Altman Michael Bennett Mike Brown Stephanie Keating Jens Langen John Matlock NASA Jennifer Roberts Photography Gabriela Secara UCSB/Sonia Fernandez Inside the Perimeter is published by Perimeter Institute for Theoretical Physics. www.perimeterinstitute.ca To subscribe, email us at [email protected]. 31 Caroline Street North, Waterloo, Ontario, Canada p: 519.569.7600 I f: 519.569.7611 02 IN THIS ISSUE 04/ Goodbye, dear Stephen, Neil Turok 06/ Remembering Stephen Hawking 08/ Three new appointments bolster mathematics and cosmology, Tenille Bonoguore 10/ Emmy Noether Fellowships expand, Tenille Bonoguore 12/ California connections, Stephanie Keating 13/ The riddle of the quantum Sphinx, Robert Spekkens 16/ Artificial intelligence teaches itself to solve gnarly quantum challenges, Tenille Bonoguore 18/ Taming the Langlands program, Dan Falk 21/ Slice of PI: My favourite equation 25/ People of PI: Ghanaian trailblazer Prince Osei, Mike Brown 27/ G7 Sherpas hold planning sessions at Perimeter, Colin Hunter 28/ Thanks to our supporters 30/ Remodelling science, Tenille Bonoguore and Stephanie Keating 33/ WGSI: How to build a better future 33/ Upcoming conferences 34/ “Aim high, work hard, and bring your swagger,” Tenille Bonoguore 36/ What’s physics good for? The incredible MRI, Erin Bow 39/ Particles 42/ PI kids are asking: Rainbows, Stephanie Keating 03 NEIL'S NOTES GOODBYE, DEAR STEPHEN I was an undergraduate physicist in technicalities. Even more wonderful, He declared himself wrong in 2002, Cambridge when I was fortunate to we became close friends. and gave John an encyclopedia on attend Stephen Hawking’s inaugural baseball but encouraged him to burn lecture as the Lucasian Chair, the There is so much to say about him, it, saying that would be as useful as position Isaac Newton once held. The it’s hard to know where to begin. It the information which survived an lecture was provocatively titled: “Is the goes without saying that he was a evaporating black hole. He bet me that end of theoretical physics in sight?” brilliant scientist of the very first rank. cosmic inflation would be confirmed by Through a series of light-hearted The concepts he formulated and future measurements – unfortunately, vignettes, Stephen explained some of the questions he started to address, we never did settle that one. physics’ greatest advances. He kept many decades ago, are so deep and the audience on tenterhooks to the farsighted that they continue to inspire Stephen loved the idea of Perimeter end, as we awaited his oracular answer the whole field. How can space and Institute. It was younger and much more to the question. When it came, it was time be quantum? What happens of a gamble when I was approached as surprising as it was unambiguous. inside black holes? What principles to become its second Director. Taking Yes, he said, the newly constructed govern the universe? I feel today we the position would mean leaving theory of supergravity, developed by are approaching the answers, guided Cambridge and Stephen behind, so I other theorists, was the answer. All in large part by observations that went rather gingerly to his office to tell that remained was to work out a few were largely lacking when Stephen him and ask for his advice. But when details. I left the lecture wondering if pioneered the field. Even if the details I described Perimeter’s mission – to physics was really over and whether I of some of Stephen’s favourite theories unify quantum theory and spacetime should switch to another field. – like inflation and supergravity – – his eyes literally shone. Although he don’t survive, I believe that his basic said he would be sorry to see me go, I Eighteen years later, I joined Stephen as intuition – that quantum mechanics could tell he shared my excitement and a Professor at Cambridge. Supergravity will connect beautifully with gravity, would lend his fullest support. Which had not worked out as the ultimate and the combination will answer deep he did, time and time again. theory (but interest in it continues questions – will turn out to be right. to this day). I knew something of First, he lent his name to our new Stephen’s elegant and influential work Despite Stephen’s stature, he never building, the Stephen Hawking Centre. combining quantum theory with gravity became stuck in his ideas. He was And then he visited, twice, despite in the context of black holes and open to questioning everything, to the massive effort and risk involved, cosmology, and I was keen to interact rigorous argument, and to finding because he wanted to see for himself with him and, if possible, to learn new connections. It made working with what this “grand experiment,” as he from him. So I presented a seminar him enormous fun; it was as if all the called it, was like. He loved being on a topic I hoped might pique his physical constraints on his body were here, having scientific discussions in interest – the birth of an inflationary mirrored by a total freedom and power the Bistro, and inviting many of us over universe. I showed how quantum of thought. You always got the sense, to barbecues at his house. He met effects in inflation, like a cosmic when discussing science with him, with everyone – the PSI students, the magician, allowed you to conjure an that in the next 30 seconds, we might scientists, and countless visitors who infinite universe out of a finite one. To change everything. wanted to be introduced to him. my delight, after the lecture, Stephen said he found the ideas interesting He loved speed and risks and jokes. In many ways, Perimeter epitomizes and he wanted to discuss more. Thus And bets! In 1975, he bet Kip Thorne Stephen’s aspirations and his vision. He began our work together, spending that black holes did not exist – a believed, as I do, that the astonishing many wonderful afternoons scribbling bet he lost. He bet John Preskill that simplicity and unity in the universe cries on the blackboard and teasing out the black holes destroyed information. out for simple, principled explanations. 04 The popular theories like inflation and playground, a little boy started yelling, Stephen very graciously (and typically) supersymmetry – which Stephen, like “That’s Stephen Hawking!” We agreed to meet the boy and thumbprint most others, went along with – remain thought no more about it, but the next the books. The photo of the two of them unconvincing and lack compelling day I received an email from the kid’s together is one of my favourites. The evidence in their favour. Physics now dad saying, “Was that really Stephen thing I love about it most is that they’re has, I believe, to return to the basic Hawking in the park?” both wearing the same shirt! Two little challenges and questions that Stephen kids at heart, driven by curiosity and posed in the earliest and most fruitful It turned out that the kid, although only a desire to have fun making sense of phase of his career. There isn’t a better six, had already read five of Stephen’s the world. place in the world for doing so than books. When he told his mom it was Perimeter. In many ways, we have Stephen, she said “it can’t be!” But – Neil Turok taken on his scientific mission at a time he desperately wanted to bring the when other places are either unable books in and have them autographed. or have lost the confidence to do so. Stephen strongly supported the Centre for the Universe we have recently created here, kindly endorsing the Stephen Hawking Fellowship to which we hope to attract an extraordinary young cosmologist. On Stephen’s very first night in Waterloo, I invited him and his team out to a local restaurant. We shared a lovely, memorable meal together. When I went to pay, I was told that a regular patron (who insisted on remaining anonymous) had settled our bill, as a welcome gift to Stephen. Stephen was delighted, telling me that, on all his travels, such a thing had never happened to him before. One fine afternoon, during Stephen’s second visit to Perimeter, he and I decided to take a walk in the park behind the Institute. As we walked around Silver Lake by the public 05 Ray Laflamme was a graduate student under Stephen Hawking at Cambridge when he was tasked with proving a theory of Hawking’s. The problem was, the theory turned out to be wrong. Stephen, although being well known and having an incredible reputation, with many people looking up to him, was a scientist. And science is very democratic. You discuss ideas, and ideas can be right or wrong. The math in theoretical physics tells you what is right and what is wrong. So I slowly, painstakingly, went through the math and showed that the original idea could not work. Fortunately, there was a colleague, Don Page, who had a very similar result to mine. We slowly convinced Stephen, and when he learned that he had made a mistake, he turned around and said, “You guys are right.” He was incredibly gracious.