The poster session will be held from 15:30 to 18:00 on March 13th in the conference room (2F) and/or INAMORI Salon (1F).
Speaker: Ashutosh Tripathi
Title: Gauge Fixing and emergence of non diagonal saddle points in the type IIB Matrix Model: Non-Perturbative Insights into Spacetime Emergence
Abstract: The Type IIB matrix model provides a non-perturbative framework for superstring theory, wherein spacetime emerges from bosonic Hermitian matrices A_mu (mu = 0..., 9). Conventional regularization techniques frequently employ Lorentz-invariant mass terms or Euclideanization. In this study, we explore an alternative gauge-fixing approach to Lorentz symmetry, which dynamically generates a mass-like term, offering a natural and symmetry-preserving means of regularization.
We classify all saddle-point solutions of the d = 4, N = 2 bosonic model and perform numerical simulations using the generalized Lefschetz Thimble Hybrid Monte Carlo method to fully capture non-perturbative quantum effects. Our findings highlight substantial discrepancies between the gauge-fixed model and the traditional SO(d+1)-symmetric formulation, particularly concerning their saddle-point structures and quantum dynamics. This work underscores the pivotal role of gauge-fixing in shaping the model’s dynamics and provides novel insights into the mechanisms of spacetime emergence in the large-N limit.
Speaker: Bowen Chen
Title: Topology and Geometry of Holographic Toric Entropic Inequalities
Abstract: Holographic entropy inequalities describe the discrepancy of entanglement entropy between holographic states and general quantum states. Recently, an infinite family of holographic entropy inequalities, called toric inequalities, has been proposed. For a two-sided black hole, toric inequalities show that a cyclic sum of entanglement entropies from subregions on both sides is lower bound by the area of the black hole horizon. In this talk, I will provide a proof of toric inequalities, highlighting its non-trivial topological properties.
Speaker: Cristian Andres Rivera Medina
Title: One-Loop Effective Action for Schwinger Pair Production on (A)dS Charge Black Holes
Abstract: We derive the one-loop effective action for pair production in the near-horizon of a (near) extremal Reissner-Nordström black hole, using the Schwinger-De Witt in-out formalism, monodromies, and worldline instantons. All these methods rely on the enhanced symmetry of the near horizon (near) extremal geometry and the consequent solvability of the simplified wave equation of a scalar field surrounding the black hole in terms of hypergeometric functions. Back-reaction is considered as quantum corrections of Einstein equations via a regularized vacuum expectation value of an energy-momentum tensor obtained from scalar QED action, and compared with the back-reaction derived from one-loop effective action, also for the case of Nariai black holes. These corrections are important to analyze because the non-perturbative nature of the Schwinger effect driven by a constant electric field, could play a crucial role in dynamic processes, also intertwined with Hawking radiation, involving the time-dependence of the entropy of black holes and subsequently, prove their expected unitary evaporation. Beyond the semiclassical regime, we also analyze the constraints that regularized energy-momentum tensor imposes on the well-behaved charge-to- mass ratio parameter space of charged black holes. Our analysis suggests that the absence of naked singularities is protected by the BF bound in the AdS branch as expected. Still, for the corresponding dS branch, a bound that forbids superextremal configurations exists if the null energy condition for the perturbations is satisfied. For the case of generic gauge fields, large extremal Nariai black holes are unstable and decay into small black holes, satisfying in this way the weak gravity conjecture.
Speaker: Davide Bason
Title: F_AdS-maximization, Seiberg-Witten theory and Anti-de Sitter space
Abstract: We study the fate of pure SU(2) N=2 SYM theory on AdS4 as a function of the only parameter the theory depends on, namely ΛL, with Λ the strong coupling scale and L the AdS radius. At ΛL<<1, namely weak coupling/high curvature, we show that the origin of the Coulomb branch defines a stable boundary condition and the theory is un-Higgsed. We then argue how this is no longer true at intermediate coupling/curvature by showing the emergence of new stable boundary conditions, consistently with the flat space limit expectations we have for Sieberg-Witten theory. To show this we perform supersymmetric localization in AdS4, extending similar results valid for the hemisphere HS4. We finally conjecture a relation between the AdS4 partition function and the N=2 prepotential, tying some of the expected properties of this function to the process of Z-minimization for the boundary R-charge.
Speaker: Haruki Yagi
Title: Threefold Way for Typical Entanglement
Abstract: A typical quantum state with no symmetry can be realized by letting a random unitary act on a fixed state, and the subsystem entanglement spectrum follows the Laguerre unitary ensemble (LUE). For integer-spin time reversal symmetry, we have an analogous scenario where we prepare a time-reversal symmetric state and let random orthogonal matrices act on it, leading to the Laguerre orthogonal ensemble (LOE). However, for half-integer-spin time reversal symmetry, a straightforward analogue leading to the Laguerre symplectic ensemble (LSE) is no longer valid due to that time reversal symmetric state is forbidden by the Kramers' theorem. We devise a system in which the global time reversal operator is fractionalized on the subsystems, and show that LSE arises in the system. Extending this idea, we incorporate general symmetry fractionalization into the system, and show that the statistics of the entanglement spectrum is decomposed into a direct sum of LOE, LUE, and/or LSE. Here, various degeneracies in the entanglement spectrum may appear, depending on the non-Abelian nature of the symmetry group and the cohomology class of the non-trivial projective representation on the subsystem. Our work establishes the entanglement counterpart of the Dyson's threefold way for Hamiltonians with symmetries.
Speaker: Hiroki Wada
Title: Anomalies and D-branes in the Dabholkar-Park background
Abstract: We consider D-branes in the Dabholkar-Park (DP) background, a 9d orientifold theory obtained by gauging symmetry in the type IIB string theory compactified on a circle. Using anomalies in the world-sheet theory, we provide physical insights into the classification of stable D-branes by relative KR-theory. The nature, such as stability, of D-branes wrapping along the compactified circle can be extracted from information about 1d Majorana fermions on the boundary of the world-sheet. These Majorana fermions need to be introduced to consistently perform the GSO projection and the orientifold. We also construct D-brane states in the DP background. The spectrum of D-branes characterized by the relative KR-theory is correctly reproduced from the D-brane states.
Speaker: Jahmall Matteo Bersini
Title: The large charge sector of the NJL model
Abstract: The large-charge expansion offers a nonperturbative framework to study conformal field theories with global symmetries. After introducing the framework, I will discuss the large charge sector of the NJL model in 2<d<4 dimensions. In particular, I will present various results for the spectrum of the lowest-lying operators with fixed U(1) axial charge Q. For d=3 and large N, I will show that the 1/Q expansion is asymptotic and determine the exponential corrections using resurgence theory.
Speaker: Meenu .
Title: Some computation in non relativistic cft in momentum space
Abstract: Non-relativistic conformal field theory illustrates the critical
point of many-body systems. The structure of correlation functions in a con-
formal field theory (CFT) is highly constrained by the conformal symmetry.
A momentum space analysis is natural from the perspective of Feynman di-
agram computations, which are usually performed in the momentum space.
The analysis in the momentum space involves solving Ward identities which
are in general non-linear second-order differential equations. I will present
the solution for 2,3 and 4-point functions of scalar operators. The solution of
3- and 4-point functions contains the undetermined parameter that plays the
role of the conformal cross ratio in momentum space. I will also mention an
interesting connection of the 3-point function with Apell’s hypergeometric
function F2 in momentum space.I will discuss 2 point correlation in boundary cft in momentum space.
Speaker: Peng-Xiang Hao
Title: Bulk local states in flat spacetime holography
Abstract: One of the putative holographic dual to the gravitational theory in asymptotically flat spacetime is the BMS field theory in one dimensional lower spacetime, which shares the same symmetry as the asymptotic symmetry for gravitational theory. We construct states in BMS field theories to describe the local excitation in three and four dimensional bulk. For massive scalar type excitations in the bulk, we propose that they should be reconstructed by the states in induced representation of the BMS algebra. For massless scalars, they can be reconstructed by the states in both induced representation and the highest weight representation.
Speaker: Saswato Sen
Title: Non-perturbative analysis of QFT on regular trees
Abstract: We investigate scalar and fermionic theories on the Bethe lattice as a prototype for field theories on curved and random spaces. The central object in the computation is the free two-point function, which contains information about the spectrum of the theory. This is later used to study interacting theories non-perturbatively in the framework of the functional renormalization group. The two-point functions are calculated by mapping the computation to a tractable combinatorial problem on the graph. In the context of the functional renormalization group, we show that the critical behavior is influenced by the spectral dimension, which is determined to be three from the two-point function. We further comment on the possibility of the existence of a Wilson-Fisher fixed point in the Bethe lattice.
Speaker: Taiichi Nakanishi
Title: Subdimensional Particles and Foliation Field Theory from Godbillon-Vey Invariant
Abstract: Recently, subdimensional particles including fractons have attracted much attention from various areas. The notable features of such matter phases are mobility constraints and subextensive ground state degeneracies (GSDs). In this work, we propose a BF-like theory motivated by the Godbillon-Vey invariant, which is a mathematical invariant of the foliated manifold. Our theory hosts subsystem higher form symmetries which manifestly ensure the mobility constraint, and subextensive GSD through the spontaneous symmetry breaking. We also discuss some lattice spin models which realize the same low energy behaviours as BF-like theory. Furthermore, we explore matter theories which are coupled with the BF-like theory. This work is based on arXiv:2408.05048 with Hiromi Ebisu, Masazumi Honda, and Soichiro Shimamori.
Speaker: Toshiki Onagi
Title: Critical phenomena in dipolar-Heisenberg model
Abstract: The Landau-Ginzburg model, which describes the critical phenomena of three-dimensional isotropic ferromagnetic systems, has recently been proposed to exhibit a peculiar property: it possesses scale invariance but lacks conformal invariance in the limit of strong coupling when extended with non-local dipolar interactions. The universal properties of this model remain unexplored, requiring non-perturbative studies. In this talk, I will discuss the theoretical background of this model and present numerical results.
Speaker: Yuki Furukawa
Title: Lattice models with subsystem/weak non-invertible symmetry protected topological order
Abstract: We construct a series of lattice models which possess subsystem non-invertible symmetry protected topological (SPT) order and analyze their interface modes protected by their symmetry, whose codimension turns out to be more than one as with higher topological insulators. We also propose 2+1d lattice models in which belong to two different weak SPT phases distinguished by a combination of translational symmetry and non-invertible symmetry and argue that the interface between them exhibits a new type of Lieb-Schultz-Mattis anomaly coming from modulated symmetry.
