Talks

May 12 (Fri)


Time: 10:00 - 11:30 (1hour 30min)

Zoom Link: Click

Title: Quantum chaos and eigenstate thermalization

Abstract: Understanding the emergence of the rules of statistical mechanics for an isolated many-body system from an underlying quantum-mechanical microdynamics is a longstanding problem of fundamental physics. Concepts from the theory of quantized classically chaotic systems can be used to resolve at least some of the key issues, and lead to the notion of "eigenstate thermalization": individual energy eigenstates of the system as a whole appear to be states of thermal equilibrium when probed by local (few-body) observables.


Time: 14:00 - 15:30 (1hour 30min)

Title: One-shot holography

Abstract: The quantum extremal surface (QES) formula computes the entropy of a holographic CFT in terms of its dual gravity description, and has led to significant breakthroughs like the computation of the Page curve. However, a naive application of this important formula leads to inconsistencies and it must be corrected at leading order. I will explain how to understand these corrections, drawing heavily on the tools of one-shot quantum Shannon theory, and I will explain what these corrections imply about the AdS/CFT duality.


Time: 16:30 - 17:30

Slide: Link

May 13 (Sat)


Time: 10:30 - 12:00 (1hour 30min)

Title: Target space entanglement in quantum mechanics of fermions and matrices

Abstract: In QFTs or spin models, the quantum entanglement of the base space where fields or spins live has been extensively studied. On the other hand, in some models (e.g. string theory and matrix models), the target space where the fields take values is thought to be related to our spacetime. To discuss entanglement in our spacetime in these models, we need a concept of the target space entanglement. An operator algebraic approach enables us to introduce the target space entanglement. I review the approach and explain our results on the target space entanglement for quantum mechanics of one-matrix or fermions.

Slide: link


Time: 14:00 - 14:30 (30min)

Title: Krylov Complexity in Scalar QFTs

Abstract: We study a notion of operator growth known as Krylov complexity in free and interacting massive scalar quantum field theories in d-dimensions at finite temperature. We consider the effects of mass, one-loop self-energy due to perturbative interactions, and finite ultraviolet cutoffs in continuous momentum space. These deformations change the behavior of Lanczos coefficients and Krylov complexity, breaking the smoothness of the former ("staggering") and decreasing the exponential growth rate of the latter. We discuss the relation between the existence of a mass gap and the staggering, as well as the relation between UV cutoffs in continuous theories and lattice models. Finally, we comment on the implications of our results for a generalization of the Maldacena-Shenker-Stanford chaos bound.

Slide: Link


Time: 14:00 - 15:30 (30min)

Title: Operator growth and complexity in SYK model 

Abstract: Under the Hamiltonian evolution, a simple operator turns into a complicated operator. We probe such growth via a recently explored measure of scrambling known as Krylov complexity. As an example, I will present some analytical and numerical results for the SYK model and interpret the results from the dual holographic side.

Slide: link

May 14 (Sun)


Time: 10:30 - 12:00 (1hour 30min)

Title: Emergence of Space and Time in Holographic Duality

Abstract: In holographic duality, a higher dimensional quantum gravity system emerges from a lower dimensional conformal field theory (CFT) with a large number of degrees of freedom. We propose a formulation of duality for a general causally complete bulk spacetime region, called subalgebra-subregion duality, which provides a framework to describe how geometric notions in the gravity system, such as spacetime subregions, different notions of times, and causal structure, emerge from the dual CFT. Subalgebra-subregion duality generalizes and brings new insights into subregion-subregion duality (or equivalently entanglement wedge reconstruction). It provides a mathematically precise definition of subregion-subregion duality and gives an independent definition of entanglement wedges without using entropy. Geometric properties of entanglement wedges, including those that play a crucial role in interpreting the bulk as a quantum error correcting code, can be understood from the duality as the geometrization of the additivity anomaly of certain algebras. Using general boundary subalgebras rather than those associated with geometric subregions makes it possible to find duals for general bulk spacetime regions, including those not touching the boundary.

Slide: link


Time: 14:00 - 15:00 (1hour)

Title: Towards the Large N Expansion for Heavy Operators

Abstract: In this talk I will explain how representation theory can be used to evaluate correlation  functions of operators whose dimension grows either as N or as N^2. The one loop dilatation operator acting on these operators can be evaluated and, in a certain limit, it can be diagonalized at large N. Drawing inspiration from the representation theory, we will write down integral representations of generating functions of these heavy operators. These integral representations provide a promising starting point for a systematic 1/N expansion, something that is under current investigation.

May 15 (Mon)


Time: 10:30 - 12:00 (1hour 30min)

Title: From JT to 3d pure gravity

Abstract: Tking inspiration from our understanding of 2d JT gravity, we develop aspects of 3d pure gravity. In particular, we propose an effective model of 3d pure gravity and discuss its factorization across entangling surfaces. Finally, we highlight some differences between gravity in its metric formulation and its first order gauge theoretic formulation, focussing on the underlying algebraic structure. Largely based on arXiv:2210.14196 and the earlier JT story in arXiv:1812.00918.

Slide: Link


Time: 14:00 - 14:30 (30min)

Title: Islands in the fluid

Abstract: We discuss the possibility of entanglement islands in cosmological spacetimes with a general perfect fluid with an equation of state ww. We find that flat universes with time-symmetric slices where the Hubble parameter vanishes always have islands on that slice. We then move away from such slices, considering still universes with a general perfect fluid. Under the local thermal equilibrium assumption, the comoving entropy density is constant. As a result, the conditions for an island become an inequality between the energy density (or Hubble parameter) and the temperature at some time of normalization. The consequences are that islands can exist for practically all fluids that are not radiation, i.e. w\neq 1/3. We also discuss the ramifications of our results for universes with spatial curvature. Finally, we show that islands occur in the Simple Harmonic Universe model which has no classical singularity at the background level, in contrast to all previous examples where islands occurred only in space-times with singularities.


Time: 14:00 - 15:30 (30min)

Title: Black hole evaporation and spontaneous collapse theory 

Abstract: We consider a general correspondence between evaporating black holes and of collapsing wave functions and use this correspondence order to explore properties of black hole evaporation. In order to do that we assume an evolution from Hartle-Hawking state to one of the superselection sectors for a specific model. The model considered is Marolf-Maxfield topological toy model for 2D gravity which gives the full spectrum of boundary theories. By equating the Marolf-Maxfield topological toy model and to the Bonifacio model of spontaneous collapse theory, an equation for the evolution of a matrix element due to a generator of a parameter in MM model is obtained.


Time: 16:00 - 16:30 (30min)

Title: Gravitational edge mode for asymptotic AdS2

Abstract: We consider a gravitational edge mode for asymptotic AdS2 in Jackiw-Teitelboim (JT) gravity. We review the edge mode of U(1) Chern-Simons theory which leads to the chiral boson living on the boundary. In the JT gravity, we discuss the gravitation edge mode from the metric fluctuation with fixed boundary which is described by the Schwarzian theory. We also discuss the alternative description of edge mode from the wiggling boundary. We discuss the relation between two descriptions.


Time: 16:30 - 17:00 (30min)

Title: Reflected entropy in non-inertial frame

Abstract: I will describe the results of our upcoming work on reflected entropy between two modes of a free Dirac field observed by two relatively accelerated parties. First I will explain the potential problems related to the reflected entropy which is considered as a correlation measure in literature in the context of a qudit-qudit-qubit (more specifically nxmx2) system. Taking care of these problems I will explain bipartite and tripartite entangled states describe by Bell state and Werner state respectively under acceleration. Here we observe that the reflected entropy decreases monotonically due to the Unruh effect, ultimately reaching a non-zero minimum value in the limit of infinite acceleration for both cases. Additionally, we find that the Markov gap exhibits a monotonic behavior with respect to acceleration in both scenarios. We also observe a particular behavior of reflected entropy which has a close resemblance to the c-function.

May 16 (Tue)


Time: 10:30 - 12:00 (1hour 30min)

Title: Decoding Supersymmetric Black Holes

Abstract: I will discuss a constructive enumeration of 1/16-BPS states in the maximally supersymmetric Yang-Mills in four dimensions, and search for ones that are not of graviton form. I will show you a handful of such states for gauge group SU(2) at relatively high energies, resolving a decade-old enigma. Along the way, I will discuss the proof of a non-renormalization theorem about the exactness of the enumeration in perturbation theory under some assumptions. Finally, I will give some preliminary results on the 1-loop anomalous dimensions of classically BPS operators at high energies and charges. This could potentially match with the spectrum of N=2 JT supergravity living at the near-horizon region of near-supersymmetric black holes.

Slide: Link


Time: 14:00 - 15:00 (1hour)

Title: Hilbert Space and Symmetries of Large N Extended StatesBA

Abstract: We discuss the large N expansion in the background of extended states with implementation of (Goldstone )symmetries and the construction of the Hilbert space. The large N thermofield represents the main focus, with the emergent dynamics of Left-Right bulk fields and collective symmetry coordinates providing the basis for a systematic 1/N expansion.

May 18 (Thu)


Time: 10:30 - 12:00 (1hour 30min)

Title: Towards quantum black hole microstates

Abstract: I will talk about the cohomology of local BPS operators in N=4 Yang-Mills theory. We will see an infinite tower of non-graviton cohomologies in the SU(2) theory and discuss to what extent they simulate quantum black holes. We will find signals for partial no-hair behaviors by showing that certain gravitons are forbidden to dress these cohomologies. This is in qualitative agreement with the perturbative hairs allowed around black holes, which also leads us to a natural setup to construct hairy BPS black holes. These cohomologies are simpler to study in the BMN matrix model truncation of the classical field theory.


Time: 14:00 - 15:00 (1hour)

Title: The endpoint of Kerr-AdS instability

Slide: Link


Time: 16:00 - 17:00 (1hour)

Title: Covariant Worldline Actions from Coadjoint Orbits and Dual Pair Correspondences

Abstract: I will demonstrate how one can derive a manifestly covariant worldline action starting from Poincare and (A)dS algebra. Starting from a coadjoint orbit of the latter algebra and using the Kostant-Kirillov-Souriau symplectic structure on it, we first derive the unconstrained Hamiltonian action on a “curved" phase space, whose quantization would lead to a unitary irreducible representation of the starting Lie algebra. We then reformulate this action as a constrained Hamiltonian action on a “flat” embedding phase space. The set of constraints is in general a mixture of the first and second class constraints, and it defines a new coadjoint orbit of a “dual” symmetry. Upon quantization, this construction provides the reductive dual pair correspondence. I will also briefly comment about this correspondence, a very powerful tool to handle a large class of representation.

May 19 (Fri)


Time: 10:00 - 11:30 (1hour 30min)

Zoom Link: Click

Title: Duality defects, entropic order parameters and Noether's theorem

Abstract: I will first review the existence of Haag duality defects in quantum field theories. These appear in theories where the assignment of local operator algebras to regions of the space is not unique. Examples include the free Maxwell field and non abelian gauge theories. These ideas give a precise way to understand completeness and the existence of generalized symmetries. I will show how entropic order parameters for confinement or spontaneous symmetry breaking can be defined through the existence of the multiple algebras for a region and the entropic certainty relation obeyed by dual order parameters. I will sketch the way different phases of QFT show up in terms of these order parameters. The interplay between duality defects and global symmetries leads to possible obstructions to the Noether theorem (existence of a conserved current for continuous symmetries) and illuminates the reason behind known cases where this theorem does not apply. Several further consequences are suggested, such as the impossibility of charge-less electrodynamics.


Time: 14:00 - 15:30 (1hour 30min)

Title: Black Hole Microstates from Giant Gravitons 

Abstract: The entropy of black holes in AdS can be understood quantitatively in terms of their CFT duals but the identifications between the two sides remain somewhat obscure. We propose an intermediate physical realization where black holes (with entropy ~N^2) are build from giant gravitons (each with entropy ~N) rather than ~N^2 ordinary gravitons. 


Time: 16:30 - 17:00 (30min)

Title: Aspects of 1/2-BPS Giant Gravitons and Their Duals


Time: 17:00 - 17:30 (30min)

Title: Thermodynamics of accelerating black holes from the covariant phase space 

Abstract: There has been recent interest in accelerating black hole solutions of Einstein-Maxwell theory due to the remarkable property that they uplift smoothly into supergravity when the black hole horizon has the topology of a “spindle”. In this talk I will discuss the thermodynamics of accelerating black holes in AdS4: I will explain how to generalize the allowed boundary conditions at conformal infinity in order to apply the covariant phase space formalism to such solutions. This will allow for a derivation of a first law of accelerating black hole mechanics, improving upon previous forms of the law which were forced to include a specific scaling of the time coordinate. I will conclude with some comments on how the supersymmetry conditions constrain the first law and implications for supergravity. This talk is based on work in collaboration with Nakwoo Kim, Hyojoong Kim and Yein Lee.

Slide: link

May 20 (Sat)


Time: 10:30 - 12:00 (1hour 30min)

Title: MATRIX MODELS AND ENTANGLEMENT OF INTERNAL DEGREES OF FREEDOM

Abstract: I will discuss notions of entanglement of internal degrees of freedom in theories of large N matrices. One such notion is target space entanglement, which appears  as entanglement of D branes in the bulk. Yet another notion relates to geometriztion of internal symmetries, as in familiar examples of holography in AdS X Y


Time: 14:00 - 15:00 (1hour)

Title: Classical and Quantum Simulations for superstring theory

Slide: link

May 21 (Sun)


Time: 10:30 - 12:00 (1hour 30min)

Title: JT gravity in dS space

Abstract: We will discuss the canonical quantisation of JT gravity in deSitter space and its implications.


Time: 14:00 - 14:30 (30min)

Title: Matrix entanglement

Abstract: In gauge/gravity duality, matrix degrees of freedom on the gauge theory side play important role for the emergent geometry. In this paper, we discuss how the entanglement on the gravity side can be described as the entanglement between matrix degrees of freedom in the dual gauge theory. We consider several classes of quantum states to which our approach can be crucial. When applied to fuzzy sphere, matrix entanglement can be used to define the usual spatial entanglement in two-brane or five-brane world-volume theory nonperturbatively in a regularized setup. Another application is to a small black hole in AdS_5 X S^5 that can evaporate without being attached to a heat bath, for which our approach suggests a gauge theory origin of the Page curve. The confined degrees of freedom in the partially-deconfined states play a crucial role in recovery of the Page curve.


Time: 14:30 - 15:00 (30min)

Title: Holography beyond AdS from the worldsheet

Abstract: I'll talk about certain novel worldsheet construction that allows us to realize holography in backgrounds that are asymptotically not AdS. I'll show how to construct operators of the spacetime theory and calculate their correlation functions. I'll also discuss black hole entropy in such a non-AdS setup. Finally, I'll talk about entanglement entropy and signatures of non-locality in the entanglement and holographic c-function.

May 22 (Mon)


Time: 10:30 - 12:00 (1hour 30min)

Title: Entanglement Area Laws in Noncommutative Matrix Backgrounds 

Abstract: I will review recent progress on defining and calculating target space entanglement entropy in matrix quantum mechanics, and if time permits touch on the emergence of area laws from Susskind-Uglum-like open strings anchored to the boundary of the entanglement cut.