Jarunee Sanongkhun | Searcharxiv

arXiv2020

Non-linear Schrödinger-type formulation of scalar field cosmology: two barotropic fluids and exact solutions

Time-independent non-linear Schrödinger-type (NLS) formulation of FRW cosmology with canonical scalar field are considered in case of two barotropic fluids. We derived Friedmann formulation variables in terms of NLS variables. Seven exact solutions found by D'Ambroise \cite{DAmbroise:2010dgl} and one new found solution are explored and tested in cosmology. The result suggests that time-independent NLS formulation of cosmology case should be upgraded to the time-dependent case.

gr-qc↗

arXiv2019

On constrained analysis and diffeomorphism invariance of generalised Proca theories

In this paper we consider generalised Proca theories coupled to any background field and with time-time and time-space components of Hessian of the vector sector are zero, whereas the space-space part is non-degenerate. By using Faddeev-Jackiw analysis, we derive the conditions that these theories have to satisfy in order for the vector sector to have three propagating degrees of freedom. Most of these conditions are trivialised due to diffeomorphism invariance requirements. This leaves only a condition that a complicated combination of terms should not be trivially zero. This condition is therefore easy to be fulfilled. For completeness, we have also investigated on how diffeomorphism invariance helps in simplifying Faddeev-Jackiw brackets.

hep-th↗