Search Talks

Cosmology and astrophysics with the extragalactic light: background and fluctuations

Abstract: The aggregate light emitted by all extragalactic sources can be measured either as an absolute intensity or through its spatial fluctuations; these are known as line-intensity mapping (LIM) when a particular line transition is targeted. I will discuss how these measurements can be used both to learn about galaxy evolution and to investigate the presence of more speculative sources of radiation, such as decaying dark matter. I will then discuss the prospects of LIM to probe the interstellar and intergalactic medium, as well as structure on large scales. In particular, I will focus on the joint information across different line transitions and across different tracers, such as galaxies and extragalactic CMB foregrounds.

Zoom Link: https://pitp.zoom.us/j/94959896129?pwd=QjhzWS9rczdBNGFndUhhNDZ1K1FLQT09

Variational methods have proven to be excellent tools to approximate the ground states of complex many-body Hamiltonians. Generic tools such as neural networks are extremely powerful, but their parameters are not necessarily physically motivated. Thus, an efficient parametrization of the wave function can become challenging. In this talk I will introduce a neural-network-based variational ansatz that retains the flexibility of these generic methods while allowing for a tunability with respect to the relevant correlations governing the physics of the system. I will illustrate the ansatz on a model exhibiting topological phase transitions: The toric code in the presence of magnetic fields. Additionally, I will talk about the use of variational wave functions to gain physical insights beyond lattice models, in particular for the real use-case of two-dimensional materials.

Information is physical, and for a physical theory to be universal, it
should model observers as physical systems, with concrete memories where
they store the information acquired through experiments and reasoning.
Here we address these issues in Spekkens' toy theory, a non-contextual
epistemically restricted model that partially mimics the behaviour of
quantum mechanics. We propose a way to model physical implementations of
agents, memories, measurements, conditional actions and information
processing. We find that the actions of toy agents are severely limited:
although there are non-orthogonal states in the theory, there is no way
for physical agents to consciously prepare them. Their memories are also
constrained: agents cannot forget in which of two arbitrary states a
system is. Finally, we formalize the process of making inferences about
other agents' experiments and model multi-agent experiments like
Wigner's friend. Unlike quantum theory or box world, in the toy theory
there are no inconsistencies when physical agents reason about each
other's knowledge.

Zoom Link: TBD

In this talk we combine integrability and conformal bootstrap to learn about correlation functions of planar maximally supersymmetric Yang- Mills theory. Focusing on correlators of four stress-tensor multiplets, we first introduce a set of dispersive sum rules that are only sensitive to single-traces in the OPE expansion (this is advantageous because this data is available from integrability). We then construct combinations of the sum rules which determine one-loop correlators. Further, we discuss how to employ the sum rules in numerical bootstrap to nonperturbatively bound planar OPE coefficients. As an example, we show a nontrivial upper bound on the OPE coefficient of the Konishi operator outside the perturbative regime. 

In this talk, I will show that supergravity on asymptotically flat spaces possesses a (nonlinear) asymptotic symmetry algebra, containing an infinite number of fermionic generators. Starting from the Hamiltonian action for supergravity with suitable boundary conditions on the graviton and gravitino fields, I will derive a graded extension of the BMS_4 algebra at spatial infinity, denoted by SBMS_4. These boundary conditions are not only invariant under the SBMS_4 algebra, but lead to a fully consistent canonical description of the supersymmetries, which have well-defined Hamiltonian generators. One finds, in particular, that the graded brackets between the fermionic generators yield BMS supertranslations, of which they provide therefore “square roots”.  I will comment on some key aspects of extending the asymptotic analysis at spatial infinity to fermions and on the structure of the SBMS_4 algebra in terms of Lorentz representations.

Zoom link: https://pitp.zoom.us/j/95951230095?pwd=eHIwUXB5SUkvd0IvZnVUN3JJMFE1QT09

As a recent combination of two strong global leaders in quantum computing, Honeywell Quantum Solutions and Cambridge Quantum, Quantinuum integrates quantum hardware and software, including solutions for drug discovery, materials science, finance, and other applications. Quantinuum aims to be a center of gravity for quantum computing, supporting collaboration across the ecosystem. For this we have also developed “TKET”, an open-source architecture-agnostic quantum software stack and ‘best in class’ compiler. This enables our partners, collaborators and clients to effortlessly work across multiple platforms and tackle some of the most intriguing and important problems in quantum computing. 

Bio: Dr. Mark Jackson is the Senior Quantum Evangelist at Quantinuum. He received his B.S. in Physics and Mathematics from Duke University and Ph.D. in Theoretical Physics from Columbia University. He then spent 10 years researching superstring theory and cosmology, co-authoring almost 40 technical articles. To promote the public understanding of science, he founded the science crowdfunding platform Fiat Physica and non-profit Science Partnership Fund. He is Adjunct Faculty at Singularity University and a Director of Astronomers Without Borders.

Zoom link: https://pitp.zoom.us/j/98433088425?pwd=UzgwcGpUYnBKNzJmMnQ1ZVNOdGVXZz09