Search Talks

I will show that quasinormal modes of black holes could be used to investigate quantum gravity or modified gravity in specific situations. Some general comments about isospectrality will also be made. Finally a few other quantum gravity phenomena associated with black holes will be underlined.

Abstract: Gamma-ray bursts (GRBs) associated with gravitational wave events are, and will likely continue to be, viewed at a much larger inclination than GRBs without gravitational wave detections.  Viewing GRBs and their afterglows at large inclination can massively affect the observed electromagnetic emission, as dramatically demonstrated by the binary neutron star merger event GW170817.  Analyzing this event and future ones requires an extension of the common GRB afterglow models which typically assume emission from a structureless (top-hat) jet viewed on-axis. I will review the evidence for inclination effects in GRB afterglows, and present a characterization of afterglows viewed at all angles from jets with and without structure. We find new closure relations for off-axis structured jets: the slope of the light curve is found in many cases to be a simple function of the inclination angle. With our theoretical tools in hand I will discuss new candidate kilonova events found in the GRB archive, showing features very similar to GW170817. Finally I will discuss our numerical model to calculate synthetic light curves and spectra, publicly available as the open source Python package afterglowpy, and the steps needed to improve our capabilities for the next LIGO observing run.

A vibrant program has formed in recent years in various scientific disciplines to take advantage of near-term and future quantum-simulation and quantum-computing hardware to study complex quantum many-body systems, building upon the vision of Richard Feynman for quantum simulation. Such activities have recently started in nuclear and particle physics, hoping to bring new and powerful experimental and computational tools to eventually address a range of challenging problems in strongly interacting quantum field theories and nuclear many-body systems. In this talk, I review a number of important developments, including proposals for simulating strongly interacting field theories with the ultimate goal of studying strong dynamics of quarks and gluons, and of nucleons. Some of the requirements for hardware technologies that are expected to enable both the analog simulations and the digital quantum computations of these problems will be enumerated, and an experiment-theory co-development program will be motivated with an emphasis on trapped-ion platforms.

There is a deep relation between classical error-correcting codes, Euclidean lattices, and chiral 2d CFTs. We show this relation
extends to include quantum codes, Lorentzian lattices, and non-chiral CFTs. The relation to quantum codes provides a simple way to solve
modular bootstrap constraints and identify interesting examples of conformal theories. In particular we construct many examples of physically distinct isospectral theories, examples of "would-be" CFT partition function -- non-holomorphic functions satisfying all constraints of the modular bootstrap, yet not associated with any

known CFT, and find theory with the maximal spectral gap among all Narain CFTs with the central charge c=4. At the level of code theories the problem of finding maximal spectral gap reduces to the problem of finding optimal code, leading to "baby bootstrap" program. We also discuss averaging over the ensemble of all CFTs associated with quantum codes, and its possible holographic interpretation. The talk is based on arXiv:2009.01236 and arXiv:2009.01244.

I will study quantum error correcting codes that model aspects of the AdS/CFT correspondence. In an algebraic approach I will demonstrate the existence of a consistent assignment, to each boundary region, of conditional expectations that preserve the code subspace. This allows us to give simple derivations of well known results for these holographic code, and also to derive a few new results. 

I will also make a connection to the theory of QFT super-selection sectors.

In the first part of the talk I will review some recent progress in large-scale structure theory and show how it can be used to measure cosmological parameters from current and future redshift surveys. Then I will discuss some ongoing challenges in the modeling of galaxy clsutering data and covariance matrices. Finally, I will present a systematic calculation of the probability distribution function for the dark matter density field and discuss its potential as a cosmological probe.

Axion-like particles (ALPs) are one of the most attractive solutions to the dark matter issue. In this talk, I will discuss new ideas in the search for ALPs in astrophysical structures. In particular, I will focus on the emission associated with their decay into photons. The discussion will involve different ALP mass ranges and wavelength bands.

Quantum circuits, relevant for quantum computing applications, present a new kind of many-body problem. Recently it was discovered that the quantum state evolved by random unitary gates, interrupted by occasional local measurements undergoes a phase transition from a highly entangled (volume law) state at small measurement rate to an area law state above a critical rate. I will review the current understanding of this transition from the statistical mechanics and the information perspectives. I will then argue that a circuit with intrinsic symmetries admits more phases, which represent distinct patterns of protection and flow of quantum information. These states can be studied and classified by mapping to an effective ground state problem of a Hamiltonian with enlarged effective symmetry. I will give two simple examples to illustrate these ideas: (i) a circuit with intrinsic Z2 spin symmetry; (ii) A circuit with Gaussian Majorana fermion gates showing a surprising Kosterlitz-Thouless transition in the entanglement content.

A proposal is made for a fundamental theory,  in which the history of the universe is constituted of views of itself.  Views are attributes of events, and the theory's only be-ables; they comprise information about energy and momentum transferred to an event from its causal past. 

The  theory is called the causal theory of views (CTV) and is a candidate for a completion of QM.  It is partly based on energetic causal sets (ECS),   an approach developed  with Marina Cortes.  A key result that applies also here is that spacetime is emergent from the ECS dynamics.  This implies that the fundamental dynamics involve no notion of space, distance or derivatives.  Instead I propose that a measure of similarity of views replaces derivatives as the basic measure of change and difference.

A measure of the diversity of views in a  causal network is introduced, called the variety (originally invented with Julian  Barbour).  I postulate a dynamics for CTV based on an action involving the variety and show that in an appropriate limit, it reduces to Schrodinger quantum mechanics.  A key result is that  the variety reduces to Bohm's quantum potential.

Based on arXiv:1307.6167,  arXiv:1308.2206 , arXiv:1712.0479 and a paper in preparation.