Speaker: Grant Remmen
Title: Veneziano Variations: How Unique are String Amplitudes?
Room: 3024
Host: Da Liu
Abstract:
String theory offers an elegant and concrete realization of how to consistently couple states of arbitrarily high spin. But how unique is this construction? In this talk, I will derive a novel, multi-parameter family of four-point scattering amplitudes exhibiting i) polynomially bounded high-energy behavior and ii) exchange of an infinite tower of high-spin modes, albeit with a finite number of states at each resonance. These amplitudes take an infinite-product form and, depending on parameters, exhibit mass spectra that are either unbounded or bounded, thus corresponding to generalizations of the Veneziano and Coon amplitudes, respectively. For the bounded case, masses converge to an accumulation point, a peculiar feature seen in the Coon amplitude but more recently understood to arise naturally in string theory. Importantly, our amplitudes contain free parameters allowing for the customization of the slope and offset of the spin-dependence in the Regge trajectory. We compute all partial waves for this multi-parameter class of amplitudes and identify unitary regions of parameter space. For the unbounded case, we apply similar methods to derive new deformations of the Veneziano and Virasoro-Shapiro amplitudes.
Speaker: Christina Gao
Title: Axion wind detection with the homogeneous precession domain of superfluid helium-3
Room: 3024
Host: Markus Luty
Abstract: Axions and axion-like particles may couple to nuclear spins like a weak oscillating effective magnetic field. Existing proposals for detecting this "axion wind" sourced by dark matter exploit analogies to nuclear magnetic resonance (NMR) and aim to detect the small transverse field generated when the axion wind resonantly tips the precessing spins in a polarized sample of material. In this talk, I will describe a new proposal using the homogeneous precession domain of superfluid He-3 as the detection medium, where the effect of the axion wind is a small shift in the precession frequency of a large-amplitude NMR signal. This setup can provide broadband detection of multiple axion masses simultaneously, and has competitive sensitivity to other axion wind experiments such as CASPEr-Wind at masses below 0.1 micro-eV by exploiting precision frequency metrology in the readout stage.
Kwanzaa ends