Matters of Gravity, The Newsletter of the Topical Group on Gravitation of the American Physical Society, Volume 44, December 2014
aa r X i v : . [ g r- q c ] J a n MATTERS OF GRAVITY
The newsletter of the Topical Group on Gravitation of the American Physical Society
Number 44 December 2014
Contents
GGR News: we hear that . . . , by David Garfinkle . . . . . . . . . . . . . . . . . . . . . GR Centenial Speakers Bureau, by Deirdre Shoemaker . . . . . . . . . . . GGR → DGR, by Nicolas Yunes . . . . . . . . . . . . . . . . . . . . . . GGR program at the APS meeting in Baltimore, MD, by David Garfinkle . Conference reports:
New Frontiers in Dynamical Gravity, by Helvi Witek . . . . . . . . . . . . Frontiers of Neutron Star Astrophysics, by David Nichols . . . . . . . . . . Quantum Information in Quantum Gravity, by Mark Van Raamsdonk . . . ditor
David GarfinkleDepartment of Physics Oakland University Rochester, MI 48309Phone: (248) 370-3411Internet: garfinkl-at-oakland.edu
WWW:
Associate Editor
Greg ComerDepartment of Physics and Center for Fluids at All Scales,St. Louis University, St. Louis, MO 63103Phone: (314) 977-8432Internet: comergl-at-slu.edu
WWW:
ISSN: 1527-3431DISCLAIMER: The opinions expressed in the articles of this newsletter represent the viewsof the authors and are not necessarily the views of APS. The articles in this newsletter arenot peer reviewed. 2 ditorial
Matters of Gravity has adopted a new publication schedule: it will appear in Decemberand June. The purpose of this change is so that a preliminary description of the GGRsessions of each upcoming April APS meeting can be shown to the GGR membership be-fore the deadline for submission of an abstract for the April meeting. The next newslet-ter is due June 2015. This and all subsequent issues will be available on the web at https://files.oakland.edu/users/garfinkl/web/mog/
All issues before number areavailable at Any ideas for topics that should be covered by the newsletter, should be emailed to me,or Greg Comer, or the relevant correspondent. Any comments/questions/complaints aboutthe newsletter should be emailed to me.A hardcopy of the newsletter is distributed free of charge to the members of the APSTopical Group on Gravitation upon request (the default distribution form is via the web) tothe secretary of the Topical Group. It is considered a lack of etiquette to ask me to mail youhard copies of the newsletter unless you have exhausted all your resources to get your copyotherwise. David Garfinkle
Correspondents of Matters of Gravity • Daniel Holz: Relativistic Astrophysics, • Bei-Lok Hu: Quantum Cosmology and Related Topics • Veronika Hubeny: String Theory • Pedro Marronetti: News from NSF • Luis Lehner: Numerical Relativity • Jim Isenberg: Mathematical Relativity • Katherine Freese: Cosmology • Lee Smolin: Quantum Gravity • Cliff Will: Confrontation of Theory with Experiment • Peter Bender: Space Experiments • Jens Gundlach: Laboratory Experiments • Warren Johnson: Resonant Mass Gravitational Wave Detectors • David Shoemaker: LIGO Project • Stan Whitcomb: Gravitational Wave detection • Peter Saulson and Jorge Pullin: former editors, correspondents at large.
Topical Group in Gravitation (GGR) Authorities
Chair: Beverly Berger; Chair-Elect: Deirdre Shoemaker; Vice-Chair: Laura Cadonati.Secretary-Treasurer: Thomas Baumgarte; Past Chair: Daniel Holz; Members-at-large: CurtCutler, Christian Ott, Andrea Lommen, Jocelyn Read, Kimberly Boddy, Steven Drasco, SarahGossan, Tiffany Summerscales. 3 e hear that . . .
David Garfinkle, Oakland University garfinkl-at-oakland.eduJacob Bekenstein has been awarded the APS Einstein Prize.Stanley Deser and Charles Misner have been awarded the Einstein Medal of the AlbertEinstein Society.Duncan Brown, Guido Mueller, Maria Alessandra Papa, and Robert Schofield have beenelected APS Fellows.Hearty Congratulations!
Centenial of General Relativity Speakers Bureau
Deirdre Shoemaker, Georgia Institute of Technology deirdre-at-gatech.edu2015 marks the centennial of Albert Einstein’s lectures first describing his theory of gen-eral relativity. The American Physical Society Topical Group in Gravitation is organizingthe Centennial of General Relativity Speakers Bureau to provide opportunities for expertsin astronomy, cosmology, and general relativity to visit colleges, universities, schools, andcommunities to give public talks, lectures, meet with students and faculty, or participate inother events. Assistance with travel funding for the speaker is available through this program,especially for minority serving institutions and for schools with little or no research activityin physics and astronomy.For more information and to request a speaker please visit the website: http://apsggr.org/?page_id=24
GGR → DGR
Nicolas Yunes, Montana State University nyunes-at-physics.montana.eduMany of you probably already know about the American Physical Society (the APS) –one of the most important physics organizations, representing over 50,000 physicists from allover. The APS sponsors meetings to promote the exchange of new results in physics, themost relevant of which for the gravity community is the April APS Meeting. The APS alsopublishes some of the most prestigious journals in our field, including the Physical Review Dand Physical Review Letters. Moreover, the APS also advocates for physics education andscience education in general, and in particular, in front of Congress, promoting funding forphysics research at NSF, DOE, and NASA.What many of you may be less familiar with is the role of “units” within the APS. Whenphysicists are left to interact freely, they will natural interact and coalesce to form “units”,which in the APS can be classified as follows: • Sections : regional groups that foster a spirit of community. • Forums : national groups built to address broad issues, such as graduate student edu-cation or international cooperation. 4
Technical Units : national groups that coalesce around a common interest in physics.Technical units are of two types:
Divisions and
Topical Groups , the main differencebeing primarily one of size – divisions have a total number of members that exceeds3% of total APS membership, while topical groups do not. Their mission, however,is similar: to bring together scientists with overlapping interests in physics and fostercooperation and communication.But size matters. Divisions play a much more important role in the APS governance. Theyhave the right to a permanent seat in the APS council, with greatly enhanced opportunitiesto advocate for their fields. Divisions also have a higher likelihood of getting plenary speakersfor the April Meeting, giving much broader visibility to their field. In addition, divisionsreceive a larger budget allocation from the APS and offer $600 in student travel support,compared to the $300 that Topical Groups offer. A larger budget allocation also means thatthey usually provide food and wine at their business meetings, during the April APS meeting,which are open to all members.Our community, gravitational physics, is represented by the Topical Group in GRavitation(GGR) in APS. Their members specialize in wide range of disciplines, including analyticaland computational studies of general relativity, mathematical and numerical relativity, testsof general relativity and experimental relativity as a whole, modified theories of gravity,relativistic astrophysics, cosmology, quantum gravity, and gravitational wave detection, toname a few. GGR was established in 1995, through an effort spearheaded by Beverly Bergerwith the invaluable assistance of Stan Whitcomb, Neil Ashby, and others. From the beginning,LIGO has been a key part of GGR, but by no means is GGR only a LIGO community. BothGGR and the LSC owe their existence to the growth of interest in gravitation which the pasttwo decades have seen.GGR provides a broadly-based but external voice to allow the gravitational physics com-munity to advocate for its interests and, as a member of GGR, you benefit directly fromthe activities the GGR executive committee organizes. GGR organizes a number of sessionsin the APS April meeting, including talks on quantum gravity, cosmology, relativistic astro-physics, and gravitational waves. This meeting, in fact, has become one of our main forumsfor releasing new results. GGR sponsors and selects the winner of the APS Einstein Prize,awarded to Jacob Bekenstein (2015), Irwin Shapiro (2013), Ted Newman (2011), Jim Hartle(2009), Rai Weiss and Ron Drever (2007), Bryce DeWitt (2005), and John Wheeler and PeterBergmann (2003). GGR has named over sixty APS fellows, an important and distinct honorsignifying recognition by one’s professional peers in the physics community. And, of course,GGR provides the much needed student travel support in these days of difficult funding.These activities don’t just happen – it is the GGR executive officers and the supportfor GGR membership that make them happen. Growth in GGR membership is one of thebest arguments we have to leverage more benefits for all of us, including increased fundingin physics and gravitation and more visibility at conferences. Joining GGR was your way ofstanding up to be counted in the community of gravitational physicists and you have donejust that. GGR is the largest topical group in the APS, but now it has grown and maturedto the point that we will be able to petition APS to become a Division. Your membershipdid that.But we are not there yet. To become a division, we must maintain our membershipnumbers above 3% of total APS membership for two consecutive years. (at this time we areeither just slightly below or just slightly above the 3% threshold). I have no doubt that thiscan be achieved, if we all work together to retain old members and make new ones. Thank5ou once more for your continuous support. Achieving this milestone makes me immenselyproud to be a member of this community.Nicolas Yunes Membership Czar 2012-2014
GGR program at the APS meeting in Baltimore, MD
David Garfinkle, Oakland University garfinkl-at-oakland.eduWe have a very exicting GGR related program at the upcoming APS April meeting inBaltimore, MD, in 2015 the Centenial of General Relativity. Our Chair-Elect, Deirdre Shoe-maker, did an excellent job of putting together this program.
Note that the deadline for submitting an abstract for this meeting is Friday,January 9, 2015 at 5:00 pm EST abstracts can be submitted at
At the APS meeting three of the plenary talks will be devoted to gravity:Clifford Will: Precision Tests of the Theory of General RelativityStuart Shapiro: Sources and Detection of Gravitational WavesJames Hartle: Quantum Gravity and CosmologyThere will be several invited sessions of talks sponsored by the Topical Group in Gravita-tion as follows:Innovative Computing in Relativity(Peter Diener, Zachariah Etienne, Tyson Littenberg)with DCOMPNeutron Stars as Laboratories for Neutrino, Nuclear and Gravitational Physics(Benjamin Lackey, Evan OConnor, Jorge Piekarewicz)with DNPDetecting GWs from the Ground and in Space(Shane Larson, Jason Hogan, David Shoemaker)with DAPAstrophysical Black holes on all mass scaleswith DAPQuantum Gravity in the 100th Anniversary of General Relativity(Joseph Polchinski, Thomas Faulkner, Walter Goldberger)with DPF 600 Years of GR, 20 Years of GGR Looking back and looking forward (panel session)(Rainer Weiss, Gabriela Gonzalez, James Hartle and Jorge Pullin)Precision experimental measurements of gravitation(Michael Hohensee, JamesFaller, Charles Hagedorn)with GPMFCHistory of Relativity(Saul Teukolsky, Diana Kormos-Buchwald )with FHPGGR Prize Session 7 ew Frontiers in Dynamical Gravity
Helvi Witek, DAMTP, University of Cambridge h.witek-at-damtp.cam.ac.ukIn March 2014 we hosted the workshop “New frontiers in dynamical gravity” or, in short,“Gauge/gravity duality meets Numerical Relativity meets fundamental math”, at the futur-istic site of DAMTP at the University of Cambridge, organised by P. Figueras, H. Reall,U. Sperhake and myself.The gauge/gravity correspondence provides a powerful tool to understand strongly coupledconformal field theories in D − D dimensions and vice versa. Nowadays, the duality is available inmany different flavours, employing calculations in GR to explore vastly different fields such ashydrodynamics and condensed matter physics. On the gravity side, which was the main focusof our workshop, this requires finding solutions in AdS and understanding their propertiesand stability as well as their dynamical evolution in time. Many of these issues cannot betackled by “pen and paper” calculations and demand a numerical treatment using both “soft”and “hard” numerics .In this workshop we brought together leading experts in these fields. The schedule of theconference – typically two one-hour long overview talks in the morning and four half-hourtalks in the afternoon – left plenty of time for fruitful discussions, the exchange of ideas andthe launching of new collaborations. The slides as well as the group photo are available onthe conference’s website .While the main focus of our workshop was gravity in AdS, there are still many open ques-tions concerning the stability of black holes (BHs) even in four dimensional, asymptoticallyflat spacetimes. This topic has been in the spotlight of a number of talks, kicking off withM. Dafermos who discussed the nature of BH singularities – we have learned that the genericBH singularity might not be space-like after all – and its importance for the (strong) cosmiccensorship conjecture. This is closely related to still open questions about the linear and non-linear stability of BHs which is an active field of research. In his talk, S. Hollands discussedthe thermodynamic stability of black objects (in four and higher dimensional spacetimes) andits implications for their dynamical properties. Although the “standard” lore states that BHsin four-dimensional, asymptotically flat spacetimes are stable this, in fact, only refers to modestability which excludes a vast number of possibly growing solutions. G. Holzegel presenteda very pedagogical summary of the state-of-the-art of the mathematical understanding of thestability of BHs: while it has been proven that Schwarzschild BHs are linearly stable, hereminded us that the linear stability in a strict mathematical sense even of the Kerr BH isstill a completely open question. Indeed, it has recently been shown that extremal BHs dosuffer from an instability, which failed to show up in a mode analysis.Nevertheless, such a mode analysis giving the characteristic response of a BH towardsperturbations provides substantial insight into BH phenomenology. C. Warnick discussedthe construction of quasi-normal modes (QNMs) for AdS BHs. As an illustrative examplehe presented computations of excitations of the Schwarzschild-AdS BH induced by scalarperturbations. Despite the importance and beauty of QNMs they do not form a completebasis for AdS BH spacetimes, thus hinting at more physics that await to be uncovered. These labels have been introduced by R. Emparan at yet another fantastic workshop on “NumericalRelativity and High Energy Physics” held at Madeira in 2011 to distinguish between solving ODEs or simplifiedPDEs using computer algebra tools like Mathematica on a desktop and the more complex computations ofBH dynamics (in at least 2+1 dimensions) requiring typically hundreds of computer cores.
BAM-PS . Ongoing, challenging numerical simulations probethe phase-space near the onset of criticality. We are looking forward to hear more about thefinal results.A couple of years ago investigations of critical phenomena in spherically symmetric AdSspacetimes brought forward a surprising outcome, which has been summarized in P. Biz´on’stalk. While the asympotically flat case provided a clear-cut transition between collapse anddispersion this picture changes dramatically in AdS. If the scalar field fails to form a BHupon its first interaction, in subsequent reflections at the AdS (timelike) boundary the fieldis focused more and more, thus eventually yielding collapse. Given that this mechanismgenerically involves a cascade towards higher energies and a transition from “pure” AdS toan AdS BH spacetime this phenomenon has been termed “turbulent instability”. However,the understanding of this instability is still in its infancy. Although pure AdS appears to begenerically non-linearly unstable there do exist “islands of stability” – a fine-tuned set in theparameter space of perturbations which evade this fate. Both M. Maliborski and S. Lieblinggave us an update on their ongoing work attempting to reveal the underlying mechanisms.These outcomes inspired investigations of gravitational turbulence in AdS BH spacetimesas L. Lehner demonstrated in his talk. Indeed, it has been observed in perturbative cal-culations that the interplay between the AdS BH and perturbations provokes a non-linearmode-coupling and cascade towards higher energies in certain regimes defined by the grav-itational analog of the Reynolds number. Additionally, these studies motivated numericalsimulations re-visiting turbulence in hydrodynamics. Features such as the formation andannihilation of vortices have been illustrated in beautiful animations.A further application of the fluid/gravity duality has been discussed in a series of talksby by R. Janik, M. Heller, P. Romatschke and K. Balasubramanian. They focused on shock-wave collisions in AdS spacetimes which can be interpreted as interactions between a stronglycoupled plasma and have specifically been employed to model heavy-ion collisions at RHICor LHC. Before starting to attack interesting physics’ questions one has to solve a numberof technical (numerical) challenges including (i) the representation of AdS spacetimes (i.e.Poincar´e versus global AdS), (ii) the specific space+time formulation of Einstein’s equations,which needs to be a well-posed initial boundary value problem, and (iii) means to extractrelevant physical information from the boundary stress-energy tensor. These challenges andnovelties for Numerical Relativity have recently been tackled. Simulations of the collisions ofshockwaves in (2+1) AdS indeed allowed to represent the strong dynamics of the collisionsof heavy ions in the field theory counterpart. It is exciting to note, that a proposed modelusing both GR simulations for the dynamical collision part followed by a hydrodynamicdescription after the equilibration shows excellent agreement with real-world particle collision.9or example, particle spectra resulting from Pb-Pb collisions at the LHC have been fittedwell with this new model while pure hydrodynamical models have been off by an order ofmagnitude.T. Wiseman reported on the latest news concerning plasma flows with space-dependenttemperature profiles. On the gravity side these fluids can be represented by recently discoveredAdS BHs with a non-Killing horizon. He gave a predagogical summary of the numericalmethods to construct these stationary solutions which requires solving a set of PDEs withmixed elliptic and hyperbolic characteristics. Via the correspondence, information about thesurface gravity and (linear) velocity of the horizon of these BHs provides insight into physicalparameters of the flowing plasma such as its (local) velocity. For a certain region of thephase-space, this plasma velocity seems to diverge hinting at an instability, possibly relatedto turbulent behaviour.A further exciting application of the gauge/gravity duality represents itself in the corre-spondence between gravity and condensed matter physics. In particular, J. Gauntlett, O.Dias and J. Santos discussed the holographic duals of metals, insulators and superconductors.A complete understanding of their phase transitions in condensed matter physics is still lack-ing. Via the correspondence these materials can be modelled in the context of gravity in AdScoupled to a Maxwell and, possibly, scalar fields. Using a periodic potential or constructingAdS BHs with non-Killing, “floppy” horizons allow to mimic so-called Q-lattices with bro-ken translational invariance. Computations on the gravity side recover, e.g., metal/insulatortransitions and the (DC) conductivity known from the solid-state physics side. Moreover,recent investigations predict the existence of new insulator and metal phases and it will beinteresting to see whether they can be discovered in real materials.A. Ishibashi addressed the instability of AdS and its connection with singularity theoremsin AdS by studying Bianchi black branes. The key requirements of known rigidity theorems(in asymptotically flat spacetimes) include the weak energy condition and the compactnessand analyticity of BH horizons. While the model presented in this talk still satisfies the weakenergy condition it is possible to construct solutions which have either non-smooth or non-compact horizons, such as stationary solutions with non-Killing horizons, and thus evade therigidity theorem.So far we have seen a number of applications of the gauge/gravity duality which exploitwell-understood physics on the gravity side to learn about hard-to-tackle problems in thedual field theory. However, we can also employ the duality to understand fundamental issuesin quantum gravity which should emerge near a BH singularity. Bearing in mind that bulkBHs can be described as thermal states in the boundary field theory this opens up the ex-citing possibility to learn about quantum gravity in AdS by investigating the gauge theory.G. Horowitz presented a holographic model which employs a conformal field theory, specifi-cally N = 4 super Yang-Mills theory in an anisotropic generalization of de Sitter spacetimes,to explore the nature of (quantum) gravity near singularities in the bulk theory. V. Hubenydiscussed how extremal surfaces and geodesics in Vaidya-AdS spacetimes, modelling BH for-mation through gravitational collapse, can be used to probe the spacetime region close to thesingularity. In contrast to static spacetimes they can penetrate the (event) horizon in the dy-namical setting at hand and, furthermore, exhibit a strikingly rich structure. The propertiesof these geodesics and surfaces can be interpreted in terms of thermodynamic quantities suchas entanglement entropy. In a related talk M. Taylor described how holography might help tobetter understand the nature of the BH interior. One of the key concerns are related to ourstill poor comprehension of the horizon and the information loss paradox, driven by (semi-)10lassical pictures. She gave a short review on recent proposals such as firewalls and fuzzballsto resolve these issues, and focused on a solution using BH microstates. These states repre-sent horizonless “stringy” geometries, thus escaping the “teething troubles” of our classicalmodels. Through a coarse-graining over these geometries we can recover the familiar classicalBH picture. C. Pope gave a talk reviewing the thermodynamics of BHs in asymptoticallyAdS spacetimes. M. Rangamani presented his ongoing work on computing the entanglemententropy in a boundary field theory using minimal surfaces in the bulk. While this constructionin principle is well understood, ensuring the causality of these solutions is fundamental. Infact, causality can be violated in the presence of time-like singularities in the bulk. He dis-cussed a number of examples including negative-mass Schwarzschild-AdS solutions or chargedscalar solitons with positive boundary energy. The requirement that causality should holdtherefore yields non-trivial constraints on these extremal surfaces.J. Armas illustrated how membranes in hydrodynamics can be mimicked using blackfolds.In particular, he discussed how this approach in higher order perturbation theory can be em-ployed to compute transport coefficients for surfaces or (mem-) branes in hydrodynamics. K.Skenderis discussed the dynamics of non-equilibrium solutions using the fluid/gravity duality.In particular, it is possible to capture the dynamics in the long wavelength regime, when thefield theory is close to a thermal equilibrium, using a hydrodynamic description. This regimecan be modelled in the gravity dual by constructing solutions in a gradient expansion givinga good prescription at long distances and late times. One such solution is the Robinson-Trautman metric, which can be seen as the dynamical (non-linear) version of algebraicallyspecial perturbations of the Schwarzschild-AdS solution, allowing us to investigate the effectof non-linearities and the approach to equilibrium.A further focus of this meeting were the properties of BHs in higher dimensional, butasymptotically flat spacetimes. R. Emparan gave a pedagogical review about his work onBHs in the large-D limit. In a nutshell, one can treat the spacetime dimension D simply as afurther parameter. Then, in the limit that the dimension becomes very large the equations ofmotion decouple into a far region (essentially described by flat spacetime), and a near region,in which the gravitional field is concentrated in a thin shell around the BH. Employing thisapproach facilitates an analytic treatment of generically rather complicated problems, such asthe computation of QNMs or the understanding of the stability of higher-dimensional BHs.In order to study the non-linear stability properties of singly-spinning Myers-Perry solu-tions in finite spacetime dimensions a fully numerical treatment is mandatory. M. Shibatapresented new results of evolutions of Myers-Perry BHs in five dimensions obtained with theimproved Sacra-5D code which uses the constraint damping mechanism facilitated in theso-called Z4c formulation of Einstein’s equations. These new numerical simulations are inexcellent agreement with a perturbative calculation published earlier this year. Because thistype of “hard” numerical evolutions are extremely demanding in terms of computational re-sources, they have not yet covered the entire parameter space and we are looking forward toread and hear about the latest results.Wednesday night we all gathered for a feast at the beautiful Trinity college. After indulgingin excellent food and wine H. Reall gave an inspiring speech recapturing the first days of ourconference and recalled some amazing anecdotes about I. Newton. Apparently, once upon atime science could come with a large amount of suffering and physical pain.One of the highlights of this conference was the visit to the
Cosmos supercomputer whichis part of the DiRAC HPC Facility funded by STFC and BIS. Thank you for the tour, Juhaand James! 11n Thursday we had a special lunch to celebrate the recent creation by the University ofCambridge of a Stephen W. Hawking Professorship in Cosmology. This chair was endowedby a donation from Dennis Avery and Sally Wong Avery. Sadly, Dennis died in 2012 but wewere delighted that Mrs Avery and members of her family were able to join the workshopparticipants for this celebration.G. Horowitz announced that J. Santos has been awarded the 2014 General Relativity andGravitation Young Scientist Prize by the International Union of Pure and Applied Physics.Congratulations, Jorge!
Acknowledgements:
We thank all the participants for their invalueable input in manyilluminating talks and discussions making this workshop a great success.We acknowledge financial support for this conference from the Institute of Physics/ Grav-itational Physics Group, STFC, the
ERC-2011-StG 279363–HiDGR
ERC Starting Grant andIntel through the Centre for Theoretical Cosmology in Cambridge.12 rontiers of Neutron Star Astrophysics
David Nichols, Cornell University david.nichols-at-cornell.eduOn May 29 and 30, 2014, a meeting called “Frontiers of Neutron Star Astrophysics” washeld at Cornell University to review open problems in neutron-star astrophysics and discussfuture directions for their solution. It was also an opportunity to celebrate the 65 th birthdayof Jim Cordes and the 60 th birthday of Ira Wasserman at a conference banquet on the eveningof the 29 th . Over the two days, a wide range of topics were covered in seventeen invited talks,eleven contributed talks, and a concluding panel discussion. These areas include mechanismsof supernova explosions; properties of radio pulsars, magnetars, and accreting neutron stars;evolution of magnetic fields; models of neutron star interiors and equation of state; binaryneutron-star mergers and their accompanying gravitational waves and electromagnetic coun-terparts; and tests of general relativity using pulsars. Many of the slides from the talksare available on the conference website at .The conference would not have been possible without the work of the chair of the scientificcommittee (Lars Bildsten) and its members (Phil Arras, David Chernoff, Jim Cordes, ´EannaFlanagan, Dong Lai, Saul Teukolsky, and Ira Wasserman), and support from the CornellDepartment of Astronomy and Center for Radiophysics and Space Research.The conference started off with a bang with Adam Burrows’ talk on the status of simula-tions of core collapse supernovae and the mechanisms that drive the collapse. Lars Bildsten’spresentation followed along a similar note by discussing the link between superluminous su-pernovae and the birth of magnetars. This first session concluded with a lecture by DuncanLorimer on the populations of radio pulsars, focusing on how the current catalog of knownpulsars can help understand the formation and evolution of neutron stars in a variety ofenvironments.Vicki Kaspi began the next session with a talk entitled “Magnetars and their ilk.” DavidKaplan described the properties of nearby neutron stars that are emitting thermally, with anemphasis on the optical and x-ray emission from isolated neutron stars and what this emissioncan reveal about their physics. Andrew Cumming then gave the last talk of the section witha presentation on the evolution of magnetic fields in the crust of neutron stars.The third session of the day began with talks from the birthday honorees. Jim Cordesdiscussed the detection of fast radio bursts and commented on whether these are likely tobe local or cosmological sources. Ira Wasserman elaborated on the effects of superconductiv-ity on the behavior of neutron-star magnetic fields and how this could affect pulsar-timingmeasurements. The third presentation was given by Armen Sedrakian who described su-perfluidity and pair-breaking processes in baryonic matter and exotic cooling mechanisms inneutron stars. The final talk of the session was by Andrzej Szary, and he presented a modelof a partially screened gap in pulsars that helped to explain properties of the radio and x-rayemission.The last group of talks on the first day commenced with Anatoly Spitkovsky on thecomputational modeling of pulsar magnetospheres. Next was Konstantinos Gourgouliatoswho commented on the role of Hall drift in determining the braking indices of young pulsars.Describing a model for radio emission from magnetars was George Melikidze, and ending thesession was Wojciech Lewandowski, who discussed the emission from gigahertz-peaked pulsarspectra.Beginning the second day was Andrei Beloborodov, who reviewed the mechanisms re-sponsible for the activity in pulsars and magnetars. David Tsang presented a mechanism by13hich tidal gravitational fields in a compact binary containing a neutron star could resonantlyshatter the star’s crust leading to a precursor to short gamma-ray bursts. Next, Scott Ran-som gave a survey of several accurately timed pulsars in binaries (and hierarchical triples)that allow for measurements of the systems’ post-Keplerian parameters and mass-radius rela-tionship. The session concluded with Sebastien Guillot describing how measurements of thespectra of low-mass x-ray binaries can be modeled to determine the mass-radius relationship,and the neutron stars’ equation of state, accordingly.Michael Kramer started the next section of talks, in which he reviewed the ability of themost relativistic binary pulsars to test the predictions of general relativity in the strong-fieldregime and to put constraints on modified gravitational theories. Following this talk, MauraMcLaughlin reviewed the prospects for using a pulsar-timing array to detect gravitationalwaves from several types of low-frequency sources. The last speaker of the session was AnnaWatts, who described recent progress in understanding x-ray bursts and burst oscillations inneutron stars.The penultimate session began with a talk by Edo Berger explaining the observationssupporting compact-object mergers being the progenitors of short gamma-ray bursts. BenLackey then discussed the prospects for measuring information about neutron-star equationof state from the gravitational waves from binary neutron-star mergers in interferometricgravitational-wave detectors. James Clark described how burst gravitational-wave searchesmight be able to detect gravitational waves emitted after the merger of binary neutron stars,when the merger forms a hypermassive neutron-star. Finally, Brian Metzger gave the lasttalk in this part on kilonovae, powered by the decay of r-process elements, being an impor-tant electromagnetic counterpart to the gravitational-wave signal from binary neutron-starmergers.In the final session of talks, Francois Foucart discussed the status of numerical-relativitysimulations of black-hole–neutron-star binaries and binary neutron-star mergers. Marc Favatadescribed the systematic errors that arise when incomplete gravitational-wave models are usedto measure the neutron-star equation of state from binary neutron-star mergers. The last talkof the conference was delivered by Sinead Walsh, who reviewed the status of gravitational-wave searches for unknown isolated neutron stars.Before the conference ended, several of the invited speakers served on a panel discussionabout where the field of neutron-star astrophysics will be headed in the next decade. Whilethere were a range of opinions about the specific results that would be found, the generalconsensus was that the prospect for new discoveries is good.14 uantum Information in Quantum Gravity Mark Van Raamsdonk, University of British Columbia mav-at-phas.ubc.caDuring recent years, a truly remarkable connection between the physics of spacetime/gravitation and the physics of quantum information has emerged, largely via the AdS/CFTcorrespondence in string theory. While surely still far from being understood completely, thereis now intriguing evidence that the structure and geometry of spacetime in these examplesis related directly and quantitatively to the structure of entanglement of the fundamentaldegrees of freedom of the theory. Further, even the dynamics of spacetime, at least in thelimit of weak curvature, has been understood to emerge from fundamental constraints obeyedby entanglement. The new ideas have presented challenges to some long-held beliefs aboutgravitational physics, famously including the smoothness of spacetime at black hole horizons.In order to present and discuss the latest work on these exciting developments, the conferenceQuantum Information in Quantum Gravity was held during the week of August 18-22, 2014in Vancouver, Canada.The setting for much of the recent work presented at the conference is the AdS/CFTcorrespondence, by which the states of certain conformal quantum field theories are in one-to-one correspondence with the states of some corresponding quantum theory of gravity. Severalof the talks related to a conjecture by Ryu and Takayanagi (and its covariant generalizationby Hubeny, Rangamani, and Takayanagi), which suggests that the entanglement entropy (ameasure of quantum entanglement) for some spatial subset of degrees of freedom in the fieldtheory is directly proportional to the area of a certain surface in the corresponding spacetimegeometry. Specific topics included: understanding how this proposal can be used to extractdual spacetime geometry from a CFT state (Myers, Sully), understanding how the proposalgeneralizes to include quantum and higher curvature corrections (Dong, Wall), understandingthe quantum information-theoretic interpretation of more general geometrical observables inthe gravity theory (Hayden), and deriving the proposal for the case of 2D CFTs (Hartman)with special properties.Several of the other talks (Karch, Mathur, Berkooz) concerned a more general proposal forrelating entanglement and geometry, which suggests that entangling non-interacting subsetsof the fundamental degrees of freedom, amounts to creating a wormhole in spacetime betweentwo distant (or disconnected) parts of spacetime. This proposal has recently been dubbedER=EPR by Maldacena and Susskind.Connections between entanglement entropy and gravitational physics provide a general-ization and refinement of the now famous connections between gravitational quantities andthermodynamic quantities; in particular the entropy-area connection for black holes. Entan-glement entropy has the property that it can be evaluated for any quantum state withoutassumptions about equilibrium. Thus, certain previous conjectures involving entropy in thegravitational context can be made more general and precise if the entropy is interpreted asentanglement entropy (either directly in the gravitational theory, or for some dual degrees offreedom). Talks by Bousso (on a proof of his covariant entropy bound in certain contexts)and Marolf (on a version of the generalized second law) related to these entanglement entropygeneralizations of conjectures about gravitational thermodynamics.A subject of great debate in the recent quantum gravity literature is the firewall paradoxof Almheri, Marolf, Polchinski, and Sully. These authors have argued that the maximalentanglement of an old black hole with its Hawking radiation forbids the local entanglementof quantum fields across the black hole horizon that would be necessary to ensure a smooth15pacetime there. Thus, according to the argument, such a black hole must have a singularity(or firewall) at its would-be horizon. Talks by Giddings, Harlow, Verlinde and Silversteindealt with various aspects of this and the closely related black hole information paradox.The conference also featured talks aimed at better understanding entanglement in a purelyfield theory context, including understanding entanglement entropies in gapped theories (Nish-ioka), and understanding the evolution of entanglement/density matrices corresponding to along wavelength subset of degrees of freedom in field theory (Lawrence). In discrete fieldtheory systems, there is a useful representation of quantum states that makes the spatialentanglement structure manifest. This is known as the Multiscale Entanglement Renormal-ization Ansatz or MERA. It was conjectured by Brian Swingle that the MERA representationof a quantum state for a field theory system with gravity dual may be directly related to howthe dual spacetime is encoded. A number of talks (Swingle, Takayanagi) presented new resultsrelating to this MERA description of field theory states.Overall, the activities of the conference reinforced the impression that connections betweengravity and quantum information represents an extremely interesting frontier in gravitationalresearch.Note: slides for many of the talks can be found at: