Showing papers by "Graham G. Ross published in 2017"

Weyl current, scale-invariant inflation, and Planck scale generation

Abstract: Scalar fields, ${\ensuremath{\phi}}_{i}$, can be coupled nonminimally to curvature and satisfy the general criteria: (i) the theory has no mass input parameters, including ${M}_{P}=0$; (ii) the ${\ensuremath{\phi}}_{i}$ have arbitrary values and gradients, but undergo a general expansion and relaxation to constant values that satisfy a nontrivial constraint, $K({\ensuremath{\phi}}_{i})=\text{constant}$; (iii) this constraint breaks scale symmetry spontaneously, and the Planck mass is dynamically generated; (iv) there can be adequate inflation associated with slow roll in a scale-invariant potential subject to the constraint; (v) the final vacuum can have a small to vanishing cosmological constant; (vi) large hierarchies in vacuum expectation values can naturally form; (vii) there is a harmless dilaton which naturally eludes the usual constraints on massless scalars These models are governed by a global Weyl scale symmetry and its conserved current, ${K}_{\ensuremath{\mu}}$ At the quantum level the Weyl scale symmetry can be maintained by an invariant specification of renormalized quantities

No fifth force in a scale invariant universe

Abstract: We revisit the possibility that the Planck mass is spontaneously generated in scale-invariant scalar-tensor theories of gravity, typically leading to a ``dilaton.'' The fifth force, arising from the dilaton, is severely constrained by astrophysical measurements. We explore the possibility that nature is fundamentally scale invariant and argue that, as a consequence, the fifth-force effects are dramatically suppressed and such models are viable. We discuss possible obstructions to maintaining scale invariance and how these might be resolved.