Title:    UNDERSTANDING COINCIDENCES

Abstract:   Coincidences astound us. They can affect where we live (and with whom), work and all sorts of things. I will review ideas of Freud and Jung on the psychology of coincidences. I will also show that sometimes, a bit of thought shows 'it's not so surprising after all'. A small set of tools and examples lead to a checklist and ways of quantifying things. This is a math talk, but aimed at a very general audience.

Title:   THE SEARCH FOR RANDOMNESS

Abstract:   I will review some of our most primitive notions of random phenomena; flipping a coin, shuffling cards and throwing a dart at the wall. Thinking about things, we can show that usually we are lazy and things are not at all random. Physics and mathematics and just plain common sense come in. This is a math talk aimed at an undergraduate audience--it has lots of stories (and you can also go make money in a casino).

Title:   When can spacetime emerge?    

Abstract:   Recent developments have taught us that some semiclassical spacetimes, in particular those containing closed universe components, cannot emerge from a usual holographic correspondence. In this talk, I will explain how one can get to this conclusion by using either quantum information theory or properties of the large N limit of AdS/CFT, and propose a criterion for detecting failures of spacetime emergence. If time permits, I will also comment on the connection to recent proposals for taking into account the presence of an observer in quantum gravity.

Reception at 4:00pm, Simons Center Lobby
Performance at 4:30pm, Simons Center Della Pietra Family Auditorium, room 103

For more information please visit: https://scgp.stonybrook.edu/archives/47634

Title:   A universal sum over topologies in 3d gravity
Abstract:   A careful analysis of the sum over topologies in 2d gravity led to an averaged form of the holographic correspondence: pure 2d gravity is dual to random matrix theory rather than to a single Hamiltonian. In this talk, I go one dimension higher and study the sum over topologies in 3d gravity and its relation to the statistical interpretation of the boundary theory. I formulate a statistical version of the conformal bootstrap that organizes universal properties of CFT data, namely typicality and crossing symmetry. I then identify a set of surgery moves on bulk manifolds that directly reflect these properties. These moves generate non-handlebodies, produce only hyperbolic manifolds, and do not generate all hyperbolic manifolds. This indicates a large range of possible choices for which manifolds may be included in the gravitational path integral, reflecting a broad class of ensembles consistent with crossing symmetry and typicality. Based on work with Alexandre Belin, Scott Collier, Lorenz Eberhardt and Boris Post (arXiv:2601.07906).

Tittle: RANDOM WALK ON THE RANDOM GRAPH

Abstract:   pick a random graph on n points by flipping a fair coin for each possible edge. Now do it again, independently. What's the chance the two graphs you get are isomorphic? Small? How small? When n= 100, less than 10^(-1300). Now, let n = infinity. Pick two graphs at random. the chance that they are isomorphic is one (!). this is THE random graph. I will illustrate its strange properties by studying random walk. This is a typical problem of probability in the presence of a random geometry. I will introduce 'Hardy's inequalities' for trees to get where we need to go. This is joint work with Sourav Chatterjee and Laurent Miclo.

Title:   Semiclassical analysis of finite cut-off JT gravity on a disk
Abstract:   In this talk I will present the computation of the partition function of finite cut-off JT gravity (with positive, zero or negative curvature) defined on a disk and coupled to conformal matter with central charge c. The analysis is done in a regime where c is a large negative number, while the magnitude of the cosmological constant scales linearly with |c| and the length of the boundary of the disk is kept finite. In this regime, the gravitational path integral is dominated by a smooth geometry corresponding to a saddle point of the action. By systematically taking into account the quantum fluctuations about this saddle point, one can obtain a perturbative expansion of the partition function in powers of 1/|c|. I will present the results for the leading and the first subleading terms in this expansion.

Students can begin to submit major/minor changes effective Fall Semester.