Thermal representations in group field theory: squeezed vacua and quantum gravity condensates

Abstract

We apply the formalism of thermofield dynamics to group field theory quantum gravity and construct thermal representations associated with generalised equilibrium Gibbs states using Bogoliubov transformations. The newly constructed class of thermal vacua are entangled, two-mode squeezed, thermofield double states. The corresponding finite temperature representations are inequivalent to the standard zero temperature one based on a degenerate vacuum. An interesting class of states, coherent thermal states, are defined and understood as thermal quantum gravity condensates.

Quantum Fluctuations in the Effective Relational GFT Cosmology

“…Another important extension would be of course the inclusion of anisotropies (de Cesare et al, 2018), but this is something we need to control much better already at the level of expectation values of geometric observables, in order to be confident about the resulting physical picture. Finally, quantum fluctuations should be considered in parallel with thermal fluctuations, which we can now compute as well using the recently developed thermofield double formalism for GFTs (Assanioussi and Kotecha, 2003;Kotecha and Oriti, 2018;Assanioussi and Kotecha, 2020).…”

Quantum fluctuations in the effective relational GFT cosmology

“…Another important extension would be of course the inclusion of anisotropies [59], but this is something we need to control much better already at the level of expectation values of geometric observables, in order to be confident about the resulting physical picture. Finally, quantum fluctuations should be considered in parallel with thermal fluctuations, which we can now compute as well using the recently developed thermofield double formalism for GFTs [56,57,61].…”

Thermal quantum gravity condensates in group field theory cosmology

“…been very useful. It has allowed for tangible explorations of connections of group field theory quantum gravity (which in turn is strictly related to several other approaches, including loop quantum gravity [19][20][21][22], spin foams [23,24], causal dynamical triangulations [25], tensor models [26] and lattice quantum gravity [27]) with quantum information theory [28][29][30][31], and also with quantum statistical mechanics and thermal physics [14,[32][33][34][35][36]. It has further allowed for importing ideas and tools from condensed matter theory, which has been crucial for instance in the development of quantum condensate cosmology [1][2][3].…”