Victor Rodriguez (UCSB) | c=1 strings as a matrix integral | April 8, 2026
We study the perturbative S-matrix of the c=1 string and show that it admits a description in terms of a double-scaled matrix integral. Together with the well-known duality to matrix quantum mechanics, this leads to a triality between worldsheet string theory, matrix quantum mechanics, and a matrix integral.
Stefano Antonini (Berkeley) | Comments on the gravitational path integral approach to cosmology | March 18, 2026
In this talk, I will discuss various aspects of the gravitational path integral (GPI) approach to cosmology. First, I will revisit the Hartle-Hawking no-boundary proposal taking into account the norms of states computed using the GPI, and explain how this dramatically alters the predictions of the proposal. I will then propose an alternative prescription, which relates cosmological initial conditions to asymptotically AdS boundary conditions. Preliminary results show this approach predicts a long inflationary period ending in a metastable de Sitter universe (modulo some technical issues I will discuss). Finally, if time allows, I will comment on recent results that the Hilbert space of closed universes is one-dimensional, and discuss the role of an ingredient common to all proposed resolutions of this issue: ensemble averaging.
Mykhailo Usatyuk (UCSB) | Near-extremal black hole evaporation | March 11, 2026
Over the last few years it has been understood that black holes sufficiently close to extremality receive large quantum corrections that modify their thermodynamic properties. In this talk, I will explain how these large corrections modify the real time dynamics of near-extremal black holes. As an example, the spectrum of emitted Hawking radiation differs drastically from the standard predictions of QFT in curved spacetime for such black holes.
Gautam Satishchandran (Princeton) | Bulk Locality from Infrared Entanglement | February 18, 2026
For quantum field theories coupled to any massless fields, one generally encounters “IR divergences” which arise due to the fact that the asymptotic description of the state contains an infinite number of soft radiative quanta. These quanta have recently gained interest due to their connections to unitarity, asymptotic symmetries and the memory effect. However, for the description of any bulk experiment, these quanta are generally viewed as a nuisance with little physical relevance for the predictions of any bulk, finite time observable.
In this talk, I will explain that this is not the case. In fact, the situation is quite the opposite: all local physical observables and phenomena depend on the entanglement and absorption of soft radiation. I will explain (1) how this phenomenon arises and (2) why it was missed in the literature and (3) why this result agrees with the predictions of collider experiments. I will primarily focus on the case of QED with and will comment on the analogous issues in QED with massless electrons, Yang-Mills theories and Quantum Gravity.
Miguel Correia (McGill) | Maximizing the Interaction Strength | February 11, 2026
QCD remains intractable in the high-energy soft regime, where all standard methods break down. This regime governs total hadronic cross-sections, which have long been observed to grow with energy, a phenomenon that is still very poorly understood today. In this talk, I will argue that the modern S-matrix bootstrap provides a systematic way to tackle this regime of QCD. I will derive an upper bound on the total cross-section at finite energy and present the strongest interacting amplitude that the bootstrap outputs. I will compare these results with proton–proton experimental data.
Shreya Vardhan (Caltech) | Negative energies and the breakdown of bulk lengths in JT gravity | January 30, 2026
One central puzzle in quantum gravity is to understand how and why predictions from semiclassical gravity can sometimes break down in a regime where we naively expect the semiclassical approximation to be valid. In particular, overlaps among states that are orthonormal in the semiclassical approximation can receive large corrections from quantum fluctuations of the geometry. I will examine such overlaps among states of fixed length in the theory of pure JT gravity, which is dual to the random matrix ensemble of Saad-Shenker-Stanford. Previously, it has been discussed that the discreteness of the boundary spectrum must cause a breakdown of the bulk length basis for lengths proportional to the boundary inverse level spacing, e^{S_0}. I will discuss how the sum over quantum fluctuations at all orders in the bulk genus expansion indicates a more dramatic breakdown than previously expected, at shorter lengths of O(e^{S_0/3}). From the perspective of the boundary spectrum, these corrections arise from the presence of negative energies in rare members of the random matrix ensemble. Work in progress with John Preskill and Mykhaylo Usatyuk.
Arash Ardehali | Cardy limit of the 3d superconformal index | January 28, 2026
Cardy limit of SUSY indices in diverse dimensions are of interest for studying black hole microstates and supersymmetric gauge dynamics, among other things. This talk will review recent results on the Cardy limit of the superconformal index of rank-one 3d N=2 gauge theories. We shall encounter mathematical structures reminiscent of those in Seiberg-Witten theory. This motivates future attempts at applying some of the new 3d N=2 techniques to 4d N=2 theories.
