String Seminar
String seminar
Special string seminar
NB: non-standard day and time.
Title: Generalized Replica Manifolds: The Tailor's Guide to Entanglement
Abstract: We develop a simple framework for implementing a type of path integral "surgery" through a correlated averaging over codimension-one defects/extended operators. This technique is then used to construct replica manifolds by effectively cutting and gluing the path integral without explicitly modifying the underlying manifold. We argue that restricted forms of this averaging may be used to calculate Rényi entanglement entropy corresponding to a wide range of choices of subsystem partitioning. When the entanglement entropy being calculated in this way does not simply correspond to entanglement between sub-regions, we call the resulting objects from this surgery ``generalized replica manifolds.'' We show how this framework extends to gauge theories and, in particular, how in non‑Abelian gauge theories it establishes a connection between replica calculations of a gauge invariant notion of entanglement between color degrees of freedom and a quiver gauge theory structure. We also discuss further extensions of this framework as well as potential application to large N models and holography.
Date:
Location:
Zoom
Event Series:
String Seminar
Title: Physical instabilities and the phase of Euclidean path integrals.
Abstract: In this talk, I will discuss the phase of the Euclidean gravity path integral in the presence of a positive cosmological constant. I will begin by reviewing the gravitational partition function on the sphere and clarifying the procedure for determining its precise phase factor. Next, I will discuss how to compute the phase on product manifolds of the form $S^p\times M$, and explain how it connects to physical instabilities in the static patch of $dS_p$. For the special case $p=2$, I will comment on the relation to Jackiw-Teitelboim gravity. Time permitting, I will also mention the phase associated with Nariai solutions.
Date:
Location:
Zoom
Event Series:
String seminar: Large N Master Field Optimization for Multi-Matrix Systems
Abstract: It is shown how large N properties of multi-matrix systems can be obtained by minimization of a loop truncated effective Hamiltonian expressed directly in terms of gauge invariant operators. The large N loop space constraints are handled by the use of master variables. For two and three massless Yang-Mills coupled matrices, highly accurate results for large N planar correlators, as well as spectrum, are presented. Generalization to larger number of matrices, relevant for systems such as BFSS, are discussed.
Date:
Location:
Zoom
Event Series:
String seminar
Title: Superluminal Liouville walls in 2d String Theory and space-like singularities
Abstract: An interesting class of time dependent backgrounds in 1+1 dimensional string theory involves worldsheet Liouville walls which move in (target space) time. When a parameter in such a background exceeds a certain critical value, the speed of the Liouville wall exceeds the speed of light, and there is no usual S-Matrix. We examine such backgrounds in the dual c=1 matrix model from the point of view of fluctuations of the collective field, and determine the nature of the emergent space-time perceived by these fluctuations. We show that so long as the corresponding Liouville wall remains time-like, the emergent space time is conformal to full Minkowski space with a time-like wall. However, for the cases where the Liouville wall is superluminal, the emergent space-time has a space-like boundary where the collective field couplings diverge. This appears as a space-like singularity in perturbative collective field theory. We comment on the necessity of incorporating finite $N$, as well as finite (double-scaled) coupling, effects to understand the behavior of the exact theory near this boundary.
Date:
Location:
CP 303
Event Series:
Physics & Astronomy String Theory Seminar
NB: non-standard time!
Title: Symmetry-weighted ensemble averaging from TQFT gravity
Abstract: In a recently proposed framework of TQFT gravity (2310.13044, 2405.20366) -- a toy model of AdS3 gravity -- a bulk 3d TQFT summed over all topologies is shown to be dual to a unitary ensemble of boundary 2d CFTs. I will show that the CFTs in this ensemble are weighted by the inverse of the order of their symmetry group (relative to the categorical symmetry provided by the bulk TQFT as a SymTFT). Mathematically, this is the natural measure over the groupoid of the TQFT Lagrangian algebras that construct the CFTs, and the holographic duality then provides a generalization of the Siegel-Weil formula beyond averaging over bosonic lattice-CFTs. I will also discuss some examples for rational CFTs as well as implications to noncompact TQFTs and pure gravity.
Date:
-
Location:
CP 303
Event Series: