Damping of pseudo-Goldstone bosons

November 4, 2021
3:00pm to 4:00pm

IFT Seminar Room/Red Room and Zoom

Specialist level
Blaise Goutereaux
CPHT, E. Polytechnique

IFT Seminar Room/Red Room and Zoom


When a continuous symmetry is spontaneously broken, new gapless modes appear in the spectrum, the Goldstone bosons. A weak explicit breaking of the same symmetry generates a small mass for the Goldstones, now called pseudo-Goldstones. On the other hand, hydrodynamics is an effective description of interacting systems at scales large compared to the local equilibration scale, which relies on solving conservation equations following from the symmetries of the system, together with the knowledge of so-called constitutive relations for the associated spatial currents. How to incorporate the physics of spontaneous symmetry breaking in the formalism is well-known. In this talk, I will explain how basic arguments show that pseudo-Goldstones acquire a universal lifetime controlled by their mass, their stiffness and a diffusive transport coefficient. This has wide-ranging applications, from QCD in the chiral limit to phases with spontaneously broken spacetime symmetries. It sheds light on a number of results reported in recent holographic literature.