On Carroll partition functions and flat space holography

We continue the study of Carroll limits on partition functions of relativistic conformal theories and their thermodynamics. By introducing imaginary chemical potentials v conjugate to momenta, one can access and study the Carroll regime in which v ≫ c. We analyze examples of free massless particles, 2d CFTs and some free field theories in d spatial dimensions. For 2d holographic CFTs, we revisit and clarify further the connection between the Carroll limit and the flat space limit of BTZ black holes. The general picture, valid in any dimension, is that, starting from AdS/CFT, the boundary Carrollian field theory lives on the horizon of a large black hole in AdS, which is pushed to the null boundary in the flat space limit.