Kavli Institute for Theoretical Physics www.kitp.ucsb.edu UC Santa Barbara NewsletterSpring 2018 open this Newsletter with a heavy heart. interior due to the poor air quality. This was a tough time for everyone, I Our good friend and colleague Joe but the spirit of KITP allowed for the event to continue unabated. Read Polchinski passed away in early February the article on page 2 to get a sense for the exciting science enabled by this 2018. I’ve since had a chance to meet with singular discovery of the electromagnetic signatures from the merger of his wife Dorothy and speak with her about two neutron stars! Joe’s remarkable legacy across all of science. The Montecito debris flow in the early morning of January 9, 2018 was Much of what was special about Joe is nicely only a few days after the arrival of a KITP program entitled: “The Physics described by Eva Silverstein in her Quanta of Dense Suspensions”. To a physicist, a dense suspension is a liquid (such Magazine article. Eva and Quanta Magazine as water) which has many small solid particles within it. The intellectual allowed us to excerpt much of that article puzzle is to find the cause of the dramatic increase in the liquid’s viscosity JAKUB OSTROWSKI on page 3. Working with David Gross, Rob as the concentration of the solids increases. What once flowed like water Lars Bildsten suddenly behaves more like molasses! This description is also very Leigh and Eva, KITP is organizing a Science Symposium in honor of close to the mud that was present in the Montecito debris flow. One of Joe on December 15, 2018. Given Joe’s exceptional impact across all the program participants, Douglas Jerolmack, a faculty member from of physics and his remarkable mentoring of early career scientists, I’m University of Pennsylvania, became very involved in scientific diagnostic sure it will be an exciting event. In the meanwhile, we are working with field work in Montecito with Professor Thomas Dunne of UCSB’s Bren the University Archivist to ensure that Joe’s original calculations are School. Douglas described their work at the conclusion of his visit to preserved and cataloged for all to see. KITP in a remarkable “Chalk Talk” that you can find on our website at: On the science front, entanglement has become a large part of what http://online.kitp.ucsb.edu/online/friends/jerolmack/ physicists think about every day, especially when together at KITP. I noted in our last Newsletter that we were in the midst of our renewal Permanent Member Leon Balents focused his inaugural lecture for the of support from the National Science Foundation. We were renewed but Pat and Joe Yzurdiaga Chair in Theoretical Physics on just this topic, as at a substantially lower level than the prior grant. This decline in federal well as the physics of magnetism (see page 4). One of our recent visitors, funding only highlights the continued need for philanthropy to support Roger Melko, was kind enough to write (see page 5) about his experience KITP’s mission. In that regard, we have added one staff member, Megan as a visitor in 2015 when Alexei Kitaev (then KITP Permanent Member, Turley, who will work with Kristi Newton and myself on development now at Caltech) gave a series of talks that triggered an avalanche of new efforts, the Friends of KITP and other important outward looking work exposing deep relations between phase transitions and the quantum activities. I look forward to introducing you to her at one of our next structure of space-time. Science takes time to yield, and on Page 6 is a KITP events! story from Thomas Gasenzer about the germination of an idea while at As of May 2018, we have been operating the Charles T. Munger Physics KITP that has since been published in Science. Residence for 16 months, and its impact continues to be felt across all The tragedies of the Thomas Fire and the later debris flow in Montecito of physics. Gerald Dunne, one of our Fall 2017 program coordinators, impacted many in our community. The smoke and ash from the Thomas shares his perspective on the physics impact of the Munger Residence on Fire had an immediate impact on our December 2017 Rapid Response the back cover. program on the double neutron star merger discovered by LIGO and In closing, I also note the passing of Stephen Hawking, a long-time VIRGO. I applaud KITP’s staff for their steadfast efforts during this period friend and supporter of KITP. Indeed, he gave the inaugural KITP Public to keep the KITP functioning despite recurrent power outages, and Lecture many years ago, as described in the article on page 7. the need to move all of the outdoor conference dining into Kohn Hall’s ~ Lars Bildsten, KITP Director A New Window on the Universe KITP hosts a rapid-response program to explore myriad new astrophysical insights from a double neutron star merger platinum in a process known as rapid neutron capture (r-process) nucleosynthesis, this latest event provides solid direct observation. “For years, people have been trying to study how the heaviest elements were formed by looking at trace fossil remnants of those elements in the sun or in meteorites,” explained UC Berkeley astrophysicist Daniel Kasen, a coordinator of the KITP program. “Finally, with this event we had the pure sample of heavy elements ejected from the neutron star merger and we were able to probe it directly, observationally, by looking at the light from the radioactive glow of those heavy elements.” For a number of years, physicists and astronomers — many of GRECO, ARNAUD, BRANCHESI, VICERE whom attended a longer KITP program on a similar topic in The blue regions show the localization by the two LIGO detectors, 2012 — have been modeling what a double neutron star merger and the much smaller white region includes the Virgo network of would look like. It turns out that many models of these extremely detectors. complicated phenomena were uncannily accurate. wo years ago, scientists from the Laser Interferometer “The gravitational waves told us that these were neutron stars and T Gravitational-Wave Observatory (LIGO) detected gravitational the electromagnetic observations told us about the spectrum of the waves for the first time, proving Einstein’s theory of relativity and his radioactive decay that produce r-process elements,” said Duncan prediction of their existence. The waves were triggered by two black Brown, the Charles Brightman Endowed Professor of Physics holes colliding. at Syracuse University and lead coordinator of the KITP rapid- response program. “You put those two together and they complete On Aug. 17, 2017, LIGO and the French-Italian Virgo detector our knowledge of the origin of the periodic table.” observed a completely new class of gravitational-wave signal: a binary neutron star merger. This merger and its afterglow were Another hot topic of the program was the immediate studied by telescopes spanning the entire electromagnetic spectrum electromagnetic counterpart to the neutron star merger. The from gamma rays to radio waves. gamma ray burst raced the gravitational waves 130 million light- years through the universe to be observed on Earth only two Of fundamental interest to both physicists and astronomers, seconds apart. This demonstrated that neutron star mergers are gravitational-wave observations have ushered in a new era of science. the long-sought origin of gamma ray bursts. It also showed that to In fact, so many scientific papers about the neutron star merger were extremely high accuracy the speed of gravity and the speed of light published in one day that researchers created an online index to keep are the same, which, according to Brown, rules out a large class of track of them. modified theories of gravity. And, less than two months after that first detection of colliding “What has been surprising to me are the discussions of the neutron stars, the KITP convened a rapid-response program for possible gamma ray burst emission mechanisms,” Brown said. “In scientists from around the world, directly supported by the Kavli gravitational-wave astronomy, the theory has been 50 years ahead Foundation. More than 75 physicists and astronomers discussed the of the observations, whereas the electromagnetic side is the other astrophysics of the neutron star merger and listened to dozens of way around; the observations are 50 years ahead of the theory. It’s presentations that delved into the details of this most recent game- going to be interesting to see how this evolves.” changing event. Physicists and astronomers will have another chance to explore “The intent of ‘GW170817: The First Double Neutron Star Merger’ is to gravitational-wave science in a future KITP program slated for broaden awareness of the results produced by the vast collaboration 2019. “The New Era of Gravitational-Wave Physics and Astrophysics” that made these exciting discoveries,” said KITP director Lars will bring together a broad group of experts to discuss the Bildsten “KITP provides a place for interested scientists not only to astrophysics and fundamental physics that can be learned from take in the vast amount of data generated by the latest event but also the observations available at that time, which hopefully will be to push interpretations of that data.” considerable. The August gravitational-wave signal produced the first distance LIGO and Virgo are updating their instrumentation with the measurement to a nearby galaxy from the merger of two neutron hope that when they come back online in fall 2018 with increased stars and explored the equation of state of matter at super-nuclear sensitivity, their efforts will yield additional observations of densities.