This week


Polygon Seminar: Tree-level scattering amplitudes with the pure spinor formalism

Triangular Seminar Carlos Mafra (U. Southampton)

15:00 KCL
room S-1.27 floor minus 1

I will give a pedagogical review of how the pure spinor formalism was used to obtain all tree-level amplitudes of the superstring, including all their alpha' corrections.

Resurgence in Large N Gauge and String Theory

Regular Seminar Ricardo Schiappa (Lisbon University)

13:15 KCL
room G01 Norfolk Building

I will present a light introduction to resurgence, with applications in large N gauge theory and in string theory.


The a-function in 3 dimensions

Regular Seminar Ian Jack (Liverpool)

13:00 IC
room H503

The a-theorem expressing the monotonicity of renormalisation group flows in four (and other even) dimensions is now well-accepted. There is a function (the a-function) generating the RG beta-functions as a gradient flow via a positive-definite metric. However the standard definition of the a-function in terms of the trace anomaly of the energy-momentum tensor does not work in odd dimensions. In this talk we focus on the gradient-flow property of the a-function and show that a function with similar properties can be constructed order-by-order in three dimensions. We start by reviewing the a-function in even dimensions from a gradient-flow standpoint. Then we discuss our explicit calculations in three dimensions. Finally we present some progress towards relating our results to the F-function which has been shown to have the expected monotonicity properties at fixed points.