# Enhanced asymptotic $BMS_3$ algebra of the flat spacetime solutions of generalized minimal massive gravity

## TL;DR

This paper studies the asymptotic symmetries of flat spacetime solutions in generalized minimal massive gravity, revealing an enhanced algebra structure and non-zero cosmological parameters, with implications for conserved charges and thermodynamics.

## Contribution

It demonstrates an enhanced asymptotic symmetry algebra combining BMS_3 and U(1) currents in generalized minimal massive gravity, extending previous results from Einstein gravity.

## Key findings

- Asymptotic symmetry algebra is a semidirect product of BMS_3 and two U(1) currents.
- Non-trivial solutions allow non-zero cosmological parameters in flat spacetime.
- Conserved charges satisfy the first law of flat space cosmologies.

## Abstract

We apply the new fall of conditions presented in the paper \cite{10} on asymptotically flat spacetime solutions of Chern-Simons-like theories of gravity. We show that the considered fall of conditions asymptotically solve equations of motion of generalized minimal massive gravity. We demonstrate that there exist two type of solutions, one of those is trivial and the others are non-trivial. By looking at non-trivial solutions, for asymptotically flat spacetimes in the generalized minimal massive gravity, in contrast to Einstein gravity, cosmological parameter can be non-zero. We obtain the conserved charges of the asymptotically flat spacetimes in generalized minimal massive gravity, and by introducing Fourier modes we show that the asymptotic symmetry algebra is a semidirect product of a $BMS_{3}$ algebra and two $U(1)$ current algebras. Also we verify that the $BMS_{3}$ algebra can be obtained by a contraction of the AdS$_3$ asymptotic symmetry algebra when the AdS$_3$ radius tends to infinity in the flat-space limit. Finally we find energy, angular momentum and entropy for a particular case and deduce that these quantities satisfy the first law of flat space cosmologies.