Focus Week on Quantum Gravity and Holography

Asia/Tokyo
Lecture Hall(1F), Kavli IPMU

Lecture Hall(1F), Kavli IPMU

Description

Dates: April 2nd - 6th, 2018

Venue: Lecture Hall (1F), Kavli IPMU

Invited Speakers include:

Tatsuo Azeyanagi (Bruxelles)
Valentina Forini (Humboldt University)
Monica Guica (Uppsala)
Yuta Hamada (Wisconsin, Madison)
Song He (Beijing ITP)
Simeon Hellerman (Kavli IPMU)
Petr Horava (Berkeley)
Jared Kaplan (Johns Hopkins)
Ami Katz (Boston)
Yasunori Nomura (Berkeley)
Hirosi Ooguri (Caltech/Kavli IPMU)
Xiaoliang Qi (Stanford)
Suvrat Raju (ICTS)
Bo Sundborg (Stockholm)
Nico Wintergerst (Stockholm)

Contributed invited talks:
Yuhma Asano (Dublin IAS/KEK)
Pallab Basu (ICTS)
Kanato Goto (UTokyo)
Goro Ishiki (Tsukuba)
Anosh Joseph (ICTS)
Rene Meyer (ITP Wuerzburg)
Max Riegler (Université libre de Bruxelles)
Takahiro Uetoko (Ritsumeikan)
Masataka Watanabe (Kavli IPMU)
Yun-Long Zhang (APCTP)

Organizers:
Tatsuo Azeyanagi (U. libre de Bruxelles)
Valentina Forini (City, U. of London)
Masanori Hanada (Kyoto U.)
Bert Vercnocke (KU Leuven)
Nico Wintergerst (Niels Bohr Inst.)
Masahito Yamazaki (Kavli IPMU)

Contact address:
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa City, Chiba 277-8583, Japan


file


Participants
  • Akihiro Miyata
  • Ami Katz
  • Anosh Joseph
  • Bikram Sapkota
  • Bo Sundborg
  • Cheng-Yong Zhang
  • Daisuke Kadoh
  • Goro Ishiki
  • Hirosi Ooguri
  • Innocent Opara
  • Jared Kaplan
  • Jin-Mann Wong
  • Kanato Goto
  • Kazumasa Okabayashi
  • Keigo Shimada
  • Kohdai Kuroiwa
  • Lento Nagano
  • Masahito Yamazaki
  • Masanori Hanada
  • Masataka Watanabe
  • Masoud Ghezelbash
  • Max Riegler
  • Miok Park
  • Moein Mirza Amraji
  • Monica Guica
  • Murli Manohar Verma
  • Nico WIntergerst
  • Nilay Kundu
  • pallab basu
  • PARTHAPRATIM PRADHAN
  • Peter Claver Nwagwu
  • Petr Horava
  • Rene Meyer
  • Seyed Morteza Hosseini
  • Shinobu Hikami
  • Shoichiro Miyashita
  • Sichun Sun
  • Simeon Hellerman
  • So Okano
  • Song He
  • Suvrat Raju
  • Takahiro UETOKO
  • Takehiro Azuma
  • tatsuyuki Sugawa
  • Tsukasa Tada
  • Valentina Forini
  • Xiaoliang Qi
  • Yasunori Nomura
  • Yuhma Asano
  • Yun-Long Zhang
  • Yuta Hamada
Contact
    • 09:55 10:00
      welcome address 5m
    • 10:00 11:00
      Constraints on Quantum Gravity (Hirosi Ooguri, Caltech, Kavli IPMU) 1h
    • 11:00 11:15
      Break (Tea Time) 15m
    • 11:15 12:15
      JT-bar deformed CFTs and their holographic interpretation (Monica Guica, IPhT/CEA Saclay /Uppsala) 1h

      It has been recently shown that the deformation of an arbitrary two-dimensional conformal field theory by the composite irrelevant operator
      TT-bar, built from the components of the stress tensor, is solvable; in particular, the finite-size spectrum of the deformed theory can be obtained from that of the original CFT through a universal formula. We study a similarly universal, Lorentz-breaking deformation of two-dimensional CFTs that possess a conserved U(1) current, J. The deformation takes the schematic form JT-bar and it is interesting because it preserves an SL(2,R) x U(1) subgroup of the original global conformal symmetries. For the case of a purely (anti)chiral current, we find the finite-size spectrum of the deformed theory and study its thermodynamic properties. Next, we show that the holographic dual of JT-bar deformed CFTs for J chiral is AdS_3 with certain modified boundary conditions. We then use holography to argue that the global symmetries of the model are enhanced to a Virasoro x Virasoro x U(1) Kac-Moody algebra, just as before the deformation; the only effect of the latter is to modify the
      spacetime dependence of the right-moving Virasoro generators, whose action becomes state-dependent and effectively non-local.

    • 12:15 13:45
      Lunch time 1h 30m
    • 13:45 14:45
      Exact Bulk Operators and the Fate of Locality (Jared Kaplan, Johns Hopkins) 1h

      Abstract: We recently used Virasoro symmetry considerations to propose an exact formula for a bulk proto-field φ in AdS3. In this talk we will explain the construction and study the propagator <φφ>. Many techniques from the study of conformal blocks can be generalized to compute it, and when the results are expanded at large central charge, they match gravitational perturbation theory for a free scalar field coupled to gravity in Fefferman-Graham gauge. Although the propagator appears to be local to all orders in perturbation theory, we explicitly compute non-perturbative effects in G ~ 1/c that spell the breakdown of bulk locality: the commutator (or retarded propagator) is non-vanishing at small spacelike separations.

    • 10:00 11:00
      Eternal traversable wormhole in two dimensions (Xiaoliang Qi, Stanford U) 1h

      We study two Sachdev-Ye-Kitaev models with a relevant coupling, and show that a subsector of this theory is dual to a gravity in nearly AdS2 geometry, with two causally connected boundaries. The coupling corresponds to matter with negative null energy in gravity theory. We study the ground state and finite temperature properties of this model. There is an interesting phase transition at finite temperature, similar to the Hawking-Page transition in higher dimensions, between a thermal AdS phase and a black hole phase.

    • 11:00 11:15
      Break (Tea Time) 15m
    • 11:15 12:15
      Non-perturbative QFT methods inspired by holography (Emanuel Katz, Boston Univ.) 1h

      I will describe a new numerical approach for calculating dynamical quantities in QFT in the non-perturbative regime.

      In this approach any QFT (including a gauge theory) can be formulated as a relevant perturbation of a UV CFT.

      The states of the CFT are used as a basis to describe the resulting RG-flow. Holography motivates a certain truncation
      of the CFT basis which allows for numerical calculation. I will provide numerical evidence in certain 2D and 3D theories that this truncation provides for an effective approximation for evaluating certain non-perturbative quantities (like the Zamolodchikov c-function along an RG-flow). Implementing the method in the context of light-cone quantization has various advantages including greatly simplifying flows in the large-N limit. Whether such a simplification occurs depends on properties of the UV large-N CFT and can be checked via a certain diagnostic. Here, again, holographic models are useful in clarifying the issues faced by the light-cone approach.

    • 12:15 13:45
      Lunch time 1h 30m
    • 13:45 14:45
      A Critique of the Fuzzball Program (Suvrat Raju, ICTS) 1h

      We explore the viability of fuzzballs as candidate microstate geometries for the black hole, and their possible role in resolutions of the information paradox. We argue that if fuzzballs provide a description of black-hole microstates, then the typical fuzzball microstate can only differ significantly from the conventional black-hole geometry at a Planck-scale-distance from the horizon. However, precisely in this region quantum fluctuations in the fuzzball geometry become large and the fuzzball geometry becomes unreliable. We verify these expectations through a detailed calculation of quantum expectation values and quantum fluctuations in the two-charge fuzzball geometries. We then examine a subset of the solutions discovered in arXiv:1607.03908. We show, based on a calculation of a probe two-point function in this background, that these solutions, and others in their class, violate robust expectations about the gap in energies between successive energy eigenstates and also violate the eigenstate thermalization hypothesis. We conclude that while fuzzballs are interesting star-like solutions in string theory, they do not appear to be relevant for resolving the information paradox, and cannot be used to make valid inferences about black-hole interiors.

    • 10:00 11:00
      Scattering Forms from Geometries at Infinity (Song He, ITP Chinese Academy of Science) 1h

      Abstract: Scattering amplitudes play a prominent role not only in high
      energy particle physics, but also for quantum gravity in
      asymptotically flat spacetime.The search for a "theory at infinity” of
      the S-Matrix has revealed surprising geometric structures underlying
      amplitudes ranging from the string worldsheet to the amplituhedron,
      but these are all geometries in auxiliary spaces as opposed to the
      space at infinity where amplitudes actually live. By thinking of
      amplitudes as differential forms, we propose a novel geometric picture
      directly in kinematic space for a wide range of massless theories in
      general dimensions.

      As a primary example, we show that tree amplitudes of bi-adjoint
      scalars are given by the “volume” of an associahedron living naturally
      in kinematic space, and scattering equations act as a diffeomorphism
      from the open-string moduli space (also an associahedron) to it. We
      find general “scattering forms” dual to color-dressed amplitudes e.g.
      for gluons and pions, which is possible due to a remarkable fact --
      “Color is Kinematics”. All these forms are well-defined in
      projectivized space, a property which provide a geometric origin for
      color-kinematics duality.

    • 11:00 11:15
      Break (Tea Time) 15m
    • 11:15 12:15
      Holography for General Spacetimes (Yasunori Nomura, UC Berkeley) 1h
    • 12:15 13:45
      Lunch time 1h 30m
    • 13:45 14:45
      Gravity and interacting O(N) model quantum mechanics (Bo Sundborg, Stockholm Univ.) 1h

      I wish to apply quantum field theory (and quantum mechanics) to define a quantum gravity theory in a simple case. AdS/CFT and gauge/gravity correspondences suggest calculating bulk quantities by boundary methods, by-passing bulk action principles. Interacting O(N) model quantum mechanics is a simple relative to higher dimensional boundary theories dual to gravity with broken higher spin symmetry. I present some calculations relevant to a connection to d=2 bulk physics, and to choosing between gauging or not gauging theories of N-component vectors in the large N limit.

    • 10:00 11:00
      Nonrelativistic Naturalness and Gravity (Petr Horava, UC Berkeley) 1h
    • 11:00 11:15
      Break (Tea Time) 15m
    • 11:15 12:00
      Black holes from singlet models (Nico Wintergerst, Niels Bohr Institute, Univ. of Copenhagen) 45m

      Thermal boundary correlation functions provide a direct and accessible way to probe features of an emergent bulk geometry. In free large N gauge theories dual to higher spin gravity and tensionless string theory, two point correlators of singlet operators encode propagation through an approximate AdS spacetime at low temperatures. Contrarily, in high temperature phases, we discover characteristic signatures of bulk black holes. This includes the existence of evanescent modes and the exponential decay of time dependent correlations, as well as significant departure of spatial correlators from their bulk thermal AdS form. Surprisingly, correlators reveal in addition the emergence of a new scale beyond which they recover their thermal AdS structure up to an overall temperature dependent normalization. This finite volume effect is most prominently seen in the O(N)/U(N) vector model in 2+1 dimensions, dual to 3+1-dimensional Vasiliev higher spin gauge theory.

    • 12:00 13:15
      Lunch time 1h 15m
    • 13:15 13:45
      Quantum Information and Topological Complexity in AdS/CFT (Rene Meyer, ITP Wuerzburg) 30m

      Recently, using the AdS/CFT correspondence exciting new relations are
      being established between aspects of quantum information theory and of
      the geometry of black holes in Anti de Sitter space-times. After a
      concise review of the roles of entanglement measures such as e.g. the
      entanglement entropy as well as of the computational complexity within
      the AdS/CFT correspondence, I discuss the notion of subregion
      complexity of a 2D critical state from three di erent viewpoints: the
      AdS3/CFT2 correspondence, random tensor networks, and kinematic space.

      From the AdS3/CFT2 point of view I explain how in the dis- continuity
      of subregion complexity as given by the volume within the
      Ryu-Takayanagi surface is related to the Euler characteristic of the
      re- spective bulk regions via the Gauss-Bonnet theorem. I then discuss
      how the volume of these sub regions can be calculated in kinematic
      space, which is the space of geodesics on the time-slice of AdS3, and
      present a new CFT expression of subregion complexity. Finally, I
      present re- sults that qualitatively reproduce the discontinuity in
      complexity in a tensor network approach. Based on arXiv:1710.01327
      [hep-th].

    • 13:45 14:15
      Bulk reconstruction of the black holes in AdS/CFT correspondence (Kanato Goto, UTokyo) 30m

      In the context of AdS/CFT, one of the most important problem is to
      understand how CFTs describe the bulk interior of the AdS spacetime.
      Especially, it is not clear whether CFTs can describe the black hole
      interior. In order to understand it, we construct the bulk local
      states which are dual to the the states locally excited by a scalar
      fields in the AdS black holes. For double-sided BHs dual to the
      thermofield double states and single-sided BHs dual to the CFT
      boundary states, our construction correctly reproduces the classical
      spacetime not only outside the horizon but also its inside. We also
      analyzed the spacetime structure dual to the high energy eigenstates
      in CFT with our construction. We found that classical black hole
      spacetime can be reproduced from CFT side unless we probe the deep
      interior in the bulk. We found the possibility that as we probe the
      deep interior, the classical notion of spacetime might break down and
      quantum corrections cannot be neglected. It might be related to the
      firewall problem which has been actively argued recently.

    • 14:15 14:30
      Break (Tea) 15m
    • 14:30 15:00
      Warped Black Holes in Lower Spin Gravity (Max Riegler, Université libre de Bruxelles) 30m

      In this talk I present a novel and very efficient description of
      spacelike warped Anti-de Sitter black holes in terms of a lower spin
      Chern-Simons theory that allows for various interesting extensions. A
      special focus will be on how to determine the thermal entropy as well
      as entanglement entropy holographically in this formulation. The
      validity of the results obtained in the Chern-Simons formalism will be
      verified by providing an additional metric interpretation.

    • 15:00 15:30
      Correlators in higher spin AdS_3 holography with loop corrections (Takahiro Uetoko, Ritsumeikan Univ., Japan) 30m

      We study the correlators of 2d W_N minimal models and quantum effects
      in the dual gravity theory. From boundary viewpoint, we develop a new
      method to compute three point functions with two scalar operators and
      a higher spin current and obtain new results at the next non-trivial
      order in 1/N expansion [arXiv : 1708.02017]. From bulk viewpoint, we
      propose new regularization prescription with the symmetry of dual CFT
      by utilization open Wilson lines and obtain two point functions of
      scalar operator up to two loop order [arXiv : 1708.08657]. I will
      explain these methods and results.

    • 15:30 16:00
      Break (Tea time) 30m
    • 16:00 16:30
      Big-J in 3D and O(4) (Masataka Watanabe, Kavli IPMU) 30m

      I will discuss conformal O(4) model at large global charges. Unlike
      the case in the O(2) model, the ground state configuration is
      inhomogeneous and its 2-point function exhibits an interesting
      behaviour.

    • 16:30 17:00
      The String Worldsheet as one Candidate Dual Description of SYK Model (Yun-Long Zhang, APCTP, China) 30m

      Recent studies of the fluctuations of an open string in AdS space show
      some pieces of evidence that the string with a worldsheet horizon
      could be a dual description of SYK model, as they saturate universal
      chaos bound and share the same symmetry. An open string hangs from the
      AdS boundary to the horizon of black brane could be dual to a 0+1
      dimensional boundary state. To be specific, we find that the
      fluctuation of the string in charged BTZ black hole has an asymptotic
      scaling symmetry, and its Euclidean IR fixed point is governed by the
      quadratic order of Schwarzian action, which is just the low energy
      effective theory of the SYK model. Considering the open string
      worldsheet also has natural reparametrization symmetry, we conjecture
      that the action of the string worldsheet is an effective dual
      description of SYK model.

    • 10:00 11:00
      Weak Gravity Conjecture, Multiple Point Principle and the Standard Model Landscape (Yuta Hamada, Univ. of Wisconsin-Madison) 1h

      The requirement for an ultraviolet completable theory to be well-behaved upon compactification has been suggested as a guiding principle for distinguishing the landscape from the swampland. Motivated by the weak gravity conjecture and the multiple point principle, we investigate the vacuum structure of the standard model compactified on S1 and T2. The measured value of the Higgs mass implies, in addition to the electroweak vacuum, the existence of a new vacuum where the Higgs field value is around the Planck scale. We explore two- and three-dimensional critical points of the moduli potential arising from compactifications of the electroweak vacuum as well as this high scale vacuum, in the presence of Majorana/Dirac neutrinos and/or axions. We point out potential sources of instability for these lower dimensional critical points in the standard model landscape. We also point out that a high scale AdS4 vacuum of the Standard Model, if exists, would be at odd with the conjecture that all non-supersymmetric AdS vacua are unstable. We argue that, if we require a degeneracy between three- and four-dimensional vacua as suggested by the multiple point principle, the neutrinos are predicted to be Dirac, with the mass of the lightest neutrino O(1-10) meV, which may be tested by future CMB, large scale structure and 21cm line observations.

    • 11:00 11:15
      Break (Tea) 15m
    • 11:15 12:15
      Simeon Hellerman 1h
    • 12:15 13:30
      Lunch time 1h 15m
    • 13:30 14:00
      N=2* Super Yang-Mills on a Lattice (Anosh Joseph, ICTS, Tata Institute) 30m

      Four-dimensional N=2 super Yang-Mills theory is obtained by introducing a one parameter
      mass deformation to the hypermultiplet of four-dimensional N=4 Yang-Mills.
      Four-dimensional N=2
      Yang-Mills is a non-conformal gauge theory and its gravitational
      dual has been constructed by Pilch and Warner. The theory exhibits many interesting
      properties at finite temperature. We formulate N=2* super Yang-Mills on a Euclidean
      spacetime lattice using the method of topological twisting. The lattice formulation is
      local, gauge invariant, doubler free and preserves one supersymmetry charge at finite
      lattice spacing. Such a construction can be used for finite temperature nonperturbative
      explorations of the theory and test the gauge-gravity duality conjecture in a
      non-conformal theory.

    • 14:00 14:10
      Break (Tea Time) 10m
    • 14:10 14:40
      Spherical transverse M5-branes from the plane wave matrix model (Goro Ishiki, Tsukuba) 30m

      We consider the matrix theoretical description of transverse M5-branes
      in M-theory on the 11-dimensional maximally supersymmetric pp-wave
      background. We apply the localization to the plane wave matrix model
      (PWMM) and show that transverse spherical fivebranes emerge as the
      distribution of low energy moduli of the scalar fields in PWMM.

    • 14:40 15:10
      Phase transitions in the BMN matrix model (Yuhma Asano, Dublin Institute for Advanced) 30m

      An idea to formulate string theory or M-theory by a gauge theory
      attracts theorists and has been extensively studied. The gauge theory
      should be lower dimensional so that a geometry in string or M-theory,
      which has higher dimensions, must emerge from it. This suggests that
      there should be a phase transition in the gauge theory and that the
      geometry would appear as its temperature decreases. In this talk, we
      focus on the BMN matrix model, which is considered as a
      non-perturbative formulation of M-theory on the pp-wave geometry and
      also conjectured to have a gauge/gravity duality, which relates each
      vacuum on the gauge theory side to a bubbling geometry in the type IIA
      supergravity. Our preliminary results of Monte Carlo simulations show
      two phase transitions and one of them looks related with emergent
      geometry.

    • 15:10 15:40
      Break (Tea time) 30m
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