Unimodular cosmology and the weight of energy

Abstract

Some models are presented in which the strength of the gravitational coupling of the potential energy relative to the same coupling for the kinetic energy is, in a precise sense, adjustable. The gauge symmetry of these models consists of those coordinate changes with unit jacobian.

Quantum corrections to unimodular gravity

“…This will allow us to make sense of a gauge fixing which takes care of the transversality condition imposed by TDiff at the cost of introducing new Batalin-Vilkovisky [7] fields which may be interpreted as a combination of Faddeev-Poppov and Nielsen-Kallosh [8] ghosts. Some previous work in Unimodular Gravity can be found in [9][10][11][12][13][14][15]. The closest in spirit to the present work is [16] where Unimodular Gravity is studied as a gauge fixed theory of a full Diff invariant extension using compensator fields.…”

Conformal and non conformal dilaton gravity

“…In those works CDG was considered as a conformally invariant offmass shell extension of quantum gravity in the context of the early attempts to understand the physical meaning 2 of the conformal anomaly [13,14]. 1 Let us agree once and for all to denote in future formulas the riemannian volume element as…”

“…which is of course only accessible as long as we are in the broken phase; and to unimodular gravity [1][2][3] 4 in the gauge φ + 2 with κ 2 ≡ 8πG. 4 Unimodular gravity is a speculative approach towards explaining why (the zero mode of) the vacuum energy seems to violate the equivalence principle (the active cosmological constant problem).…”

The Renormalization Group flow of unimodular f(R) gravity

“…It is thus of interest to investigate a quantum theory of unimodular gravity. Unimodular gravity in both its quantum and classical form has sparked considerable interest since it was originally proposed [3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”