Speaker
Description
We develop a covariant first-order thermodynamic description of Jordan-frame tensor–multi-scalar gravity by interpreting the additional gravitational degrees of freedom as an effective imperfect fluid. Unlike the single-field case, the presence of several scalar directions introduces independent thermal channels that cannot, in general, be reduced to a single effective temperature variable. We identify distinct contributions associated with the nonminimal coupling, the full time-like motion in scalar field space, and residual spatial scalar gradients, and derive their corresponding transport equations. This structure shows that freezing the effective gravitational coupling is generally insufficient to guarantee relaxation toward General Relativity: non-equilibrium degrees of freedom may remain in field-space directions orthogonal to the coupling. In homogeneous and isotropic cosmology, spatial contributions vanish by symmetry, while the intrinsically multi-field time-like dynamics survives. The resulting framework provides a covariant thermodynamic characterization of relaxation and GR-like behavior in multi-scalar extensions of gravity.
| Topic | Scalar-tensor gravity |
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