Speaker: Quentin Bonnefoy
Title: Positivity bounds on nonlinear supersymmetry
Room: 3024
Host: Da Liu
Abstract:
Effective theories of spontaneously broken supersymmetry (SUSY) couple Goldstinos and matter fields. A convenient formalism, that of constrained superfields, recycles the techniques used to build theories with unbroken SUSY. However, the associated constraints are not unique. Using positivity bounds, I will argue that the use of some of those constraints is forbidden by the requirement that there should exist a UV completion. I will also illustrate how this is captured by explicit matching computations. These results resonate with causality issues caused by gravitinos during inflation.
Speaker: Rachel Houtz
Title: Discrete Goldstone Bosons
Room: 3024
Zoom: https://zoom.us/j/186024391
Host: Da Liu
Abstract:
In this talk, I will discuss discrete Goldstone bosons (dGB's), light particles arising from spontaneously broken exact discrete symmetries. These dGB's are guaranteed to have nonzero masses, while the associated discrete symmetry protects them from quadratically divergent mass contributions. The nonzero masses of dGB's arise directly from the discrete symmetry, without requiring an explicit symmetry breaking mechanism, setting dGB's apart from other pseudo-Goldstone bosons. After explaining the mass protection mechanism, I will discuss the generic experimental signals of dGB's. Below the spontaneous symmetry breaking scale, typically a preserved subset of the discrete symmetry remains, leading to a telltale signal of degenerate dGB's being produced simultaneously. Moreover, ratios of multi-scalar production amplitudes give a probe of the full UV discrete symmetry.
Speaker: Lingfeng Li
Title: New inflationary probes of axion dark matter
Room: 3024
Host: Da Liu
Abstract:
If a light axion is present during inflation and becomes part of dark matter afterwards, its quantum fluctuations contribute to dark matter isocurvature. In this article, we introduce a whole new suite of cosmological observables for axion isocurvature, which could help test the presence of axions, as well as its coupling to the inflaton and other heavy spectator fields during inflation such as the radial mode of the Peccei-Quinn field. They include correlated clock signals in the curvature and isocurvature spectra, and mixed cosmological-collider non-Gaussianities involving both curvature and isocurvature fluctuations with shapes and running unconstrained by the current data. Taking into account of the existing strong constraints on axion isocurvature fluctuations from the CMB, these novel signals could still be sizable and potentially observable. In some models, the signals, if observed, could even help us significantly narrow down the range of the inflationary Hubble scale, a crucial parameter difficult to be determined in general, independent of the tensor mode.
