This week

Monday

Lonti: (Holographic) Fermi Surfaces

Regular Seminar David Vegh (QMUL)

at:
10:30 Other
room Youtube
abstract:

Lonti Autumn 2021 Series: Lecture 2. Release of Recorded Lecture. Abstract: In this lecture, we present a few elementary facts about Fermi surfaces, then discuss how to find interesting "non-Fermi liquids" via the AdS/CFT correspondence. We study different backgrounds (e.g. AdS, BTZ, and Reissner-Nordstrom), and the wave-equation of probe fields on top of these geometries. We discuss how to compute boundary two-point functions by solving the bulk equations and then explore the results.

Lonti: What is an Anomaly?

Regular Seminar Chris Herzog (KCL)

at:
10:30 KCL
room Online
abstract:

Lonti Autumn 2021 Series: Lecture 1. Live Tutorial. Please register at https://lonti.weebly.com/registration.html to receive joining instructions for this live session which will be held via Zoom. Four examples of an anomaly are presented, two from quantum mechanics and two from quantum field theory. The first example is a charged bead on a wire in the presence of a magnetic field. This example of a 't Hooft anomaly is related to the theta angle in Yang-Mills theory. The remaining three examples present scale and conformal anomalies. We will scatter a plane wave off an attractive delta function in two dimensions. We also look at a massless scalar field, both in two dimensions without a boundary and in three dimensions with one.

Tuesday

In Conversation with Sir Roger Penrose

Colloquium Roger Penrose (Oxford)

at:
19:00 Other
room Faraday Theatre, Royal Institution
abstract:

In conversation: Sir Roger Penrose, Thomas Fink & Yang-Hui He Live at the Royal Institution + Livestream Sir Roger Penrose is a mathematical physicist with the eye of an artist and the soul of a philosopher. He won the 2020 Nobel Prize in Physics for his work on the mathematical foundations of black holes. The tilings which bear his name can cover the plane in a never-repeating pattern. His work on the theory of mind suggests consciousness is a peculiarly human capability. He is a master word-smither, capable of rendering the most complex ideas clear, and his popular books have inspired a generation of physicists and laymen alike. In this event, Sir Roger joins Thomas Fink and Yang-Hui He on stage for a conversation about the man behind the science. We take a rare look into the workings of this singular mind. How does he get his ideas? Is beauty a guide to truth? What’s the basis of free will? Is AI a threat? Can art inform science? And is man different from machine? https://www.rigb.org/whats-on/events-2021/october/public-in-conversation-with-sir-roger-penrose https://lims.ac.uk/event/in-conversation-with-sir-roger-penrose/

Black hole microstates from the worldsheet

Regular Seminar David Turton (Southampton)

at:
14:00 IC
room Huxley 342
abstract:

I will describe recent studies of bound states of NS5 branes carrying momentum and/or fundamental string charge, in the decoupling limits leading to little string theory and to AdS3/CFT2 duality. This work involves a class of exactly solvable worldsheet models that describe families of BPS and non-BPS black hole microstates. These models have enabled studies of string and D-brane probes of these microstates, yielding insight into their stringy structure in the gravitational bulk description.

Wednesday

Supersymmetric Yang--Mills theories on the lattice

Regular Seminar David Schaich (Liverpool)

at:
14:00 IC
room H503
abstract:

Lattice field theory provides a non-perturbative regularization suitable for strongly interacting systems, which has proven crucial to the study of quantum chromodynamics among many other theories. Lattice investigations of supersymmetric field theories have a long history but often struggle due to the interplay of supersymmetry with the lattice discretization of space-time. I will discuss a way around these difficulties for d-dimensional supersymmetric Yang--Mills theories with at least 2^d supercharges. After informally reviewing some highlights of the lattice formulation, I will survey a selection of results from recent and ongoing numerical studies, including tests of holographic dualities.

Analyticity and Unitarity for Cosmological Correlators

Triangular Seminar Shota Komatsu (CERN)

at:
14:30 KCL
room online
abstract:

I will discuss the fundamentals of quantum field theory on a rigid de Sitter space. First, I will show that the perturbative expansion of late-time correlation functions to all orders can be equivalently generated by a non-unitary Lagrangian on a Euclidean AdS geometry. This finding simplifies dramatically perturbative computations, as well as allows us to establish basic properties of these correlators, which comprise a Euclidean CFT. Second, I use this to infer the analytic structure of the spectral density that captures the conformal partial wave expansion of a late-time four-point function, to derive an OPE expansion, and to constrain the operator spectrum. Third, I will prove that unitarity of the de Sitter theory manifests itself as the positivity of the spectral density. This statement does not rely on the use of Euclidean AdS Lagrangians and holds non-perturbatively.

Comments on Large Charge and Holography

Triangular Seminar Shota Komatsu (CERN)

at:
16:00 KCL
room online
abstract:

I will discuss two topics on the large charge limit and holography. First, I will discuss general features of the large-charge limit of superconformal field theories at large N. In particular, I will point out a simple setup to analyze the large charge expansion of the planar N=4 super Yang-Mills and discuss its holographic interpretation. Second, I will discuss the large-charge limit of the defect CFT on the Wilson line and its relation to the matrix model.

Thursday

T.b.a.

Journal Club Mykola Dedushenko (SUNY, Stony Brook)

at:
15:45 Other
room Zoom, instructions in abstract
abstract:

T.b.a. ------------------- Part of the London Integrability Journal Club. Please register at integrability-london.weebly.com if you are a new participant. The link will be emailed on Tuesday.