Search Talks

Several puzzles and issues in quantum gravity are related to the question of what type of high-energy information is actually available to low-energy observers. In this talk I will try to argue that the best description available to a low-energy observer is probably of a statistical nature. Such a statistical description naturally connects to e.g. the eigenstate thermalization hypothesis, and wormholes and the apparent lack of factorization. I will describe this statistical picture and the evidence we have for it, and what we could possibly learn from it. Partially based on work in progress.

Zoom Link: https://pitp.zoom.us/j/96646337719?pwd=UVRKN3Y4Q05xNXk1VExOenYwSFZvZz09

In this talk, we will discuss the late time behavior of out of time ordered correlators (OTOC). First part of the talk, we argue the nonlinear behavior of OTOC for general chaotic system is controlled by a Dray t’Hooft like action. Second part of the talk, we will discuss the late time nonperturbative effects in OTOC and its relation with random unitary behavior.

Higgs inflation introduces a large non-minimal coupling between the Ricci scalar and Higgs that makes the cut-off scale well below the Planck scale. In the first part of the talk, we show that unitarity is indeed violated by a resonant production of longitudinal gauge bosons after inflation, calling for UV completion of Higgs inflation. We then show that unitarity is restored after summing over vacuum polarization-type diagrams that are leading-order in the large-N limit. Scattering amplitude develops a pole after the resummation, which we identify as the scalar component of the metric, or the scalaron. This phenomenon can be understood in the language of the non-linear sigma model (NLSM), with the scalaron identified as the sigma-meson that linearizes the NLSM.

Zoom Link: https://pitp.zoom.us/j/98015814051?pwd=YWdrWTJzbzJkdnFXRUxPWFJnNXVNQT09

A salient feature of black holes near extremality is the appearance of an AdS$_2$ throat in their near-horizon geometry. Depending on the underlying theory, these AdS$_2$ throats may be unstable to fragmentation, wherein a single throat is instead replaced by a tree-like structure of branched AdS$_2$ throats. For Einstein-Maxwell theory, the underlying reason behind this instability is the existence of multi-centered configuration in the moduli space of black hole solutions at fixed total charge. Given the success of the Schwarzian/SYK paradigm for understanding a single AdS$_2$ it is time to revisit the fragmentation story. To build up intuition, I will present a model, studied in the statistical mechanics literature, that shares many features with SYK, including exact solvability at large-N and an emergent conformal symmetry that gets weakly broken in the UV. The novel feature of this model is the appearance of a spin glass phase at O(1) temperatures, which I will try to relate to the fragmentation story.

In this talk I will review work on `decomposition,' a property of 2d theories with 1-form symmetries and, more generally, d-dim'l theories with (d-1)-form symmetries. Decomposition is the observation that such quantum field theories are equivalent to ('decompose into’)  disjoint unions of other QFTs, known in this context as "universes.” Examples include two-dimensional gauge theories and orbifolds with matter invariant under a subgroup of the gauge group. Decomposition explains and relates several physical properties of these theories -- for example, restrictions on allowed instantons arise as a "multiverse interference effect" between contributions from constituent universes. First worked out in 2006 as part of efforts to understand string propagation on stacks, decomposition has been the driver of a number of developments since. In the first half of this talk, I will review decomposition; in the second half, I will focus on the recent application to anomaly resolution of Wang-Wen-Witten in two-dimensional orbifolds.

The quantization of a non-linear sigma model in 1+1 dimensional space-time, whose target space is equipped with a non positive definite metric is an interesting open problem having potential applications to string theory and Condensed Matter Physics. Perhaps the simplest example where it can be studied is the 2D Lorentzian black hole sigma model that was introduced by Witten in '91. The purpose of this talk is to discuss the results of  the paper arXiv:2010.10613. There it was found that the scaling limit of a certain spin chain, that lies within the integrability class of an inhomogeneous six-vertex model, is closely related to the Lorentzian black hole sigma model and its Euclidean version.

Zoom Link: https://pitp.zoom.us/j/91519988720?pwd=RTdrT1NWc3V0SXZVTGxETVBlTm5YUT09

The talk will present the status and plans of the search for low mass dark matter using electron counting semiconductor detectors. In this talk I will describe the skipper-CCD technology and the results of the SENSEI experiment using this technology for direct dark matter search. Finally, I will present the ongoing efforts to develop the next generation of experiments using this technology (Oscura).

Zoom Link: https://pitp.zoom.us/j/91739887327?pwd=V2ZiajlENjlrY1pyNWN2OFBaTUduZz09

Fractons are relatively new types of quasiparticles which have recently been inspiring activity within several branches of physics. I will offer some motivations and perspectives from quantum information theory, condensed matter physics, and high energy physics, focusing mainly on my work in the latter two subjects. This talk is primarily based on https://arxiv.org/abs/2108.08322 and a paper to appear shortly with Dominic Williamson.

Paleo-Detectors are natural minerals which record damage tracks from nuclear recoils over geological timescales. Minerals commonly found on Earth are as old as a billion years, and modern microscopy techniques may allow to reconstruct damage tracks with nanometer scale spatial resolution. Thus, paleo-detectors would constitute a technique to achieve keV recoil energy threshold with exposures comparable to a kiloton-scale conventional "real-time" detector. In this talk, I will discuss the potential of paleo-detectors for the direct detection of dark matter as well as for detecting low-energy neutrinos as are e.g. emitted by core collapse supernovae or our Sun. Furthermore, the age of the minerals provides the ability to look back across gigayear-timescales, giving paleo detectors the unique ability to probe changes in the cosmic ray rate or the galactic supernova rate over such timescales as well as dark matter substructure Earth might have encountered during its past few trips around our Galaxy.

I will present a class of recently computed holographic correlators between half-BPS operators in a vast array of SCFTs with non-maximal superconformal symmetry in dimensions d=3,4,5,6. Via AdS/CFT, these four-point functions are dual to gluon scattering amplitudes in AdS. Exploiting the notion of MRV limit I will show that, at tree level, all such correlators are completely fixed by symmetries and consistency conditions. Our results encode a wealth of novel CFT data and exhibit various emergent structures, including Parisi-Sourlas supersymmetry, hidden conformal symmetry and color-kinematics duality. This talk will be based on https://arxiv.org/pdf/2103.15830.pdf.

A generic low-energy prediction of string theory is the existence of a large collection of axions, commonly known as a string axiverse. String axions can be distributed over many orders of magnitude in mass, and are expected to interact with one another through their joint potential. In this talk, I will show how non-linearities in this potential lead to a new type of resonant energy transfer between axions with nearby masses. This resonance generically transfers energy from axions with larger decay constants to those with smaller decay constants, leading to a multitude of signatures. These include enhanced direct detection prospects for a resonant pair comprising even a small subcomponent of dark matter, and boosted small-scale structure if the pair is the majority of DM. Near-future iterations of experiments such as ADMX and DM Radio will be sensitive to this scenario, as will astrophysical probes of DM substructure.

Despite years of research into dark matter, little has been done to explore models which are heavier than most WIMPs and lighter than most primordial black hole models, "blobs".  This parameter space is particularly difficult to probe, due to low number densities and low masses.  This talk will present a new model-independent mechanism that can be used to probe this difficult to reach region of dark matter parameter space.  Blobs form binaries which spin down and merge at high rates in the present and recent past.  The abundance of mergers can produce observable gravitational wave and electromagnetic signals.  I describe some of these unique signals and show how they already constrain parts of blob parameter space.

Zoom Link: https://pitp.zoom.us/j/98024869740?pwd=eDlPSTB3UzhIcEVYVGNQakRHVUtFQT09