Amplitude's Positivity vs. Subluminality

17.05.2023 11:30 – 12:30

Effective Field Theories (EFTs) find applications in diverse branches of physics, in particular,
particle physics, cosmology, and condensed matter systems. Thus narrowing down the space
of ‘consistent’ EFTs is an important and useful exercise. In this talk, I will discuss causality and
unitarity constraints on dimension 6 and dimension 8 Gluon field strength operators in QCD.
In particular, I will compare the two different ways to get these bounds: the “IR avatar”—where one
demands that the speed of fluctuations about any non-trivial background should not exceed the
speed of light, and the “UV avatar”—where one uses dispersion relation for 2→2 scattering in
the forward limit. Finally, I will mention an interesting non-relativistic example where the IR avatar
(i.e., subluminality) produces a stronger bound than the UV avatar (i.e., S-matrix positivity).

Lieu

Bâtiment: Sciences I

Room 222

entrée libre