Talks

The space-based gravitational wave detector LISA may be able to detect gravitational waves from a first order phase transition at the electroweak scale. Acoustic waves produced during the transition are largely responsible for the resulting signal. I will present results from a large campaign of simulations studying such phase transitions, determining the spectral shape of the gravitational wave power spectrum with unparalleled accuracy. Measuring a cosmological stochastic background could place constraints on the phase transition parameters, such as the nucleation rate and temperature, and therefore provide important information about physics beyond the Standard Model. However, better understanding of the source, as well as the underlying theories of physics beyond the Standard Model, is required before the launch of LISA. I will outline how this understanding can be developed.

In this talk we will review our physical proposal, with D. Persson and R. Volpato, to understand the genus zero property of monstrous moonshine. The latter was proven by Borcherds in 1992 by brute-force computation but has since resisted a conceptual understanding. We embed the Monster VOA of Frenkel-Lepowsky-Meurman into a heterotic string compactification and use physical arguments, i.e. T-dualities and decompactification limits, to understand the genus zero property. We find that the Monster Lie algebra (a Generalized, or Borcherds-Kac-Moody algebra) acts as a sort of "algebra of BPS states". We also sketch an analogous proposal, with S. Harrison and R. Volpato, for Conway moonshine using the type II string. Along the way we construct a new super Borcherds-Kac-Moody algebra on which the Conway group acts faithfully and prove its (twisted) denominator identities, which should be identified with BPS state counts in our string theory.