Speaker
Description
We investigate the thermodynamics of a hadron gas in de Sitter spacetime using the hadron resonance gas model. QCD thermodynamics is sensitive to external environments because changes in the vacuum structure, hadron spectrum, and effective degrees of freedom can modify the thermodynamic behavior of the system. Curved spacetimes provide a particularly rich setting, since vacuum states and thermality can depend on the observer; in de Sitter spacetime, the Bunch-Davies vacuum is perceived as a thermal state by a static observer with the Gibbons-Hawking temperature. Motivated by this observer-dependent thermality, we study the temperature dependence of the energy density and entropy density within the causally accessible region of a static observer. We find that these quantities are dominated by vacuum contributions and geometric corrections associated with higher-spin fields. Our results indicate that the thermodynamics of hadronic matter in de Sitter spacetime is strongly governed by both vacuum structure and spacetime geometry, rather than by thermal excitations alone.