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Full-Text Articles in Cosmology, Relativity, and Gravity
Phenomenology Of Fermion Production During Axion Inflation, Michael Roberts
Phenomenology Of Fermion Production During Axion Inflation, Michael Roberts
Doctoral Dissertations
We study the production of fermions through a derivative coupling to an axion inflaton and the effects of the produced fermions on the scalar and tensor metric perturbations. We show how such a coupling can arise naturally from supergravity with an axion-like field driving large-field inflation and small instanton-like corrections. We present analytic results for the scalar and tensor power spectra, and estimate the amplitude of the non-Gaussianties in the equilateral regime. The scalar spectrum is found to have a red-tilted spectral index, small non-Gaussianities, and can be dominant over the vacuum contribution. In contrast, the tensor power spectrum from …
Boundary Terms Unbound! Holographic Renormalization Of Asymptotically Linear Dilaton Gravity, Robert Mcnees, Robert Mann
Boundary Terms Unbound! Holographic Renormalization Of Asymptotically Linear Dilaton Gravity, Robert Mcnees, Robert Mann
Robert A McNees IV
A variational principle is constructed for gravity coupled to an asymptotically linear dilaton and a p-form field strength. This requires the introduction of appropriate surface terms—also known as 'boundary counterterms'—in the action. The variation of the action with respect to the boundary metric yields a boundary stress tensor, which is used to construct conserved charges that generate the asymptotic symmetries of the theory. In most cases a minimal set of assumptions leads to a unique set of counterterms. However, for certain examples we find families of actions that depend on one or more continuous parameters. We show that the conserved …