Triangle Seminars

Abstract:
The first recorded lecture of the London Theory Institute for PhD Students. Link to recording and problems (to be solved in live Zoom session next Monday) as well as registration details at

https://lonti.weebly.com/

and

https://youtu.be/CGDNipeuVEs

Instantons, or solutions to the self dual Yang Mills (SDYM) equations are well known solutions, introduced in the mid 70s and played a role in a host of applications in QFT and String Theory. This talk will show a simple brane construction which allows the computation of the moduli space of solutions to the SDYM equations, introduce the student to the world of quivers, and demonstrate simple computations which allow evaluations of these moduli spaces.

Abstract:
I will show that metastable higher spin particles, free or interacting, cannot couple to gravity while preserving causality unless there exist higher spin states in the gravitational sector much below the Planck scale. Causality imposes an upper bound on the mass of the lightest higher spin particle in the gravity sector in terms of quantities in the non-gravitational sector. I will argue that any weakly coupled UV completion of such a theory must have a gravity sector containing infinite towers of asymptotically parallel, equispaced, and linear Regge trajectories. This implies that the gravity sector has a stringy structure with an upper bound on the string scale. Another consequence of this bound is that all metastable higher spin particles in 4d with masses below the string scale must satisfy a weak gravity condition. Moreover, these bounds also have surprising implications for large N QCD coupled to gravity and cosmology.

[please email a.held@imperial.ac.uk for zoom link or password]

Abstract:
In has become clear in recent years that working in sectors of large global charge of strongly coupled and otherwise inaccessible CFTs leads to important simplifications. It is indeed possible to formulate an effective action in which the large charge appears as a control parameter. In this talk, I will explain the basic notions of the large-charge expansion using the simple example of the O(2) model and then generalize to models with a richer structure which showcase other effects. [For the zoom link please email alejandro.cabo_bizet@kcl.ac.uk]

Abstract:
(for Zoom link please email Silvia Nagy s.nagyATqmul.ac.uk There will be a pre-seminar for students at 13.30)
ABSTRACT:
A universal relationship between asymptotic symmetries, QFT soft theorems, and low energy observables has reinvigorated attempts at flat space holography. We will begin by introducing a map from 4d S-matrix elements to 2d correlators in a putative dual Celestial CFT, and then re-examine the IR triangle from the perspective of our Celestial CFT.

Abstract:
Part of London Integrability Journal Club. New participants should register using the form at integrability-london.weebly.com. The link will be emailed.

Abstract:
t.b.a. –––––––––– Part of the London Integrability Journal Club. New participants please register using the form at integrability-london.weebly.com.