PASCOS 2026

Bounds on Goldstone Dispersion Relations

Not scheduled

20m

Richard Roberts Auditorium

Poster

Speaker

Warin Patrick McBlain (SISSA)

Description

Using the analyticity properties of retarded Green's functions, we show that the Goldstone dispersion relations can be written in terms of ‘typically-real functions’: a well-known class of functions in Geometric Function Theory. This identification yields optimal two-sided bounds on Wilson coefficients of higher-derivative operators as explicit functions of the sound speed $c_s$. We test these bounds against the $U(1)$ superfluid as a controlled UV completion, finding agreement across the physical range of $c_s$ and particularly in the relativistic limit $c_s\to 1$ regime. Our framework can be applied directly to the EFT of inflation and dark energy, constraining higher-derivative operators in terms of sound speed in both settings.