Triangle Seminars

Abstract:
This is the live session included as part of the LonTI lecture on the Superconformal Index. Please register at https://lonti.weebly.com/registration.html to receive joining instructions for this live session which will be held via Zoom.
The superconformal index is a very useful tool that allows us to probe the protected spectrum of a superconformal field theory (SCFT). After a brief review of the construction of unitary irreducible representations of the superconformal algebra, I will then motivate and give its definition for generic SCFTs before specialising to 4D N=2. Special limits of the index with additional supersymmetry, as well as applications will also be discussed. No prior knowledge of the topic is required.

Abstract:
The NANOGrav Collaboration has recently reported strong evidence for a stochastic common-spectrum process, which we interpret as a SGWB in the framework of cosmic strings. The possible NANOGrav signal would correspond to a string tension Gμ∈(4×10^{−11},10^{−10}) at the 68% confidence level, with a different frequency dependence from supermassive black hole mergers. The SGWB produced by cosmic strings with such values of Gμ would be beyond the reach of LIGO, but could be measured by other planned and proposed detectors such as SKA, LISA, TianQin, AION-1km, AEDGE, Einstein Telescope and Cosmic Explorer. If this interpretation is confirmed future GW measurements would also allow us to probe the expansion history of the Universe to times much before what we can infer from the currently known data.

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

Abstract:
Motivated by the desire to understand the dynamics of light modes on
various gravitational backgrounds,
this talk summarizes recent results concerning properties of scalar,
vector, and tensor excitations of black holes and integrable stringy
geometries.

For rotating black holes and for certain Wess-Zumino-Witten models,
full separability of all dynamical equations is demonstrated, and
symmetries underlying this property are uncovered. For other classes
of integrable backgrounds, the energy spectra of various fields are
evaluated, and the algebraic constructions of the corresponding
eigenfunctions are presented.




Join Zoom Meeting
https://zoom.us/j/94137164225?pwd=ZTV3Z2c3aStOdk5sSFRRbkhQRUh5dz09

Meeting ID: 941 3716 4225
Passcode: 500873

Abstract:
I will discuss the tools we are developing to calculate correlation functions of primordial inflationary perturbations. In this talk, we will focus on the limit where gravitational excitations are neglected and the cosmological spacetime is assumed to be exactly de Sitter. Even in this simplifying limit, which corresponds to a Quantum Field Theory on a de Sitter background, very few examples of explicit analytic calculations exist and little is known about basic properties of the correlators. I will show that for any dS QFT there exists a theory formulated in a Euclidean Anti-de SItter space and which reproduces all the correlation functions. This leads to major technical simplifications and allows to demonstrate various analytic properties of the cosmological observables. Understanding of these properties has both phenomenological applications in inflation, as well as provides some hints about more fundamental description for cosmological spacetimes.
[please email alejandro.cabo_bizet@kcl.ac.uk for the zoom link]

Abstract:
We study operators with a bare dimension that grows as N^2 in the large N limit. These operators are labeled by a Young diagram with p long rows, as well as a graph, with p nodes. The dilatation operator describing the mixing of these operators defines a Hamiltonian for excitations hopping on this graph. The scrambling and equilibration of the resulting dynamics is studied. [For zoom link please contact jung-wook(dot)kim(at)qmul(dot)ac(dot)uk]

Abstract:
In this talk, I will discuss how the formalism of affine Gaudin models can be used to construct new integrable sigma-models. I will start by reviewing the construction of affine Gaudin models and their interpretation as integrable two-dimensional field theories. I will then explain how well-chosen realisations of these models give integrable coupled sigma model on an arbitrary number of copies of a Lie group G^N as well as integrable coset models on the quotient of G^N by a diagonal subgroup. In particular, I will discuss application of the latter construction to T^11 manifolds. –- Part of the London Integrability Journal Club. If you are a new participant, please register at integrability-london.weebly.com. The link will be emailed.