Theory HEP Seminar

Catastrophic Production of Slow Gravitinos

Evan McDonough

Chicago

In this talk I will discuss gravitational particle production of the massive spin-3/2 Rarita-Schwinger field, and its close relative, the gravitino. For masses lighter than the value of the Hubble expansion rate after inflation, there is catastrophic gravitational particle production, wherein the number of gravitationally produced particles is divergent, caused by a transient vanishing of the helicity-1/2 gravitino sound speed. In contrast with the conventional gravitino problem, the spectrum of produced particles is dominated by those with momentum at the UV cutoff. This suggests a breakdown of effective field theory, which might be cured by new degrees of freedom that emerge in the UV, i.e., in supergravity. A survey of supergravity models reveals those where the catastrophe is cured and models where it persists. Insofar as quantizing the gravitino is tantamount to quantizing gravity, as is the case in any UV completion of supergravity, the models exhibiting catastrophic production are prime examples of 4-dimensional effective field theories that become inconsistent when gravity is quantized, suggesting a link to the Swampland program. We propose the Gravitino Swampland Conjecture.