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We use the techniques of effective field theory in an expanding universe to examine the effect of choosing an excited inflationary initial state built over the Bunch-Davies state on the CMB bi-spectrum. We find that even for Hadamard states, there are unexpected enhancements in the bi-spectrum for certain configurations in momentum space due to interactionsâ€¦ (More)

- Samuel Clark Ligon, Branislav HusÃ¡r, Harald Wutzel, Richard Holman, Robert Liska
- Chemical reviews
- 2014

hydrogen from thiol, and as a result reinitiation occurs by a thiyl radical. While the thiolâˆ’ene reaction in Scheme 14 implies the formation of linear polymer from difunctional enes and difunctional thiols, the situation is in reality much more complicated with reactive vinyls such as acrylates. In such cases, both thiolâˆ’ene step growth and acrylate chainâ€¦ (More)

We study the decay of scalar fields, in particular the inflaton, into lighter scalars in a De Sitter spacetime background. After providing a practical definition of the rate, we focus on the case of an inflaton interacting with a massless scalar field either minimally or conformally coupled to the curvature. The evolution equation for the expectation valueâ€¦ (More)

In semilocal theories, the vacuum manifold is fibered in a non-trivial way by the action of the gauge group. Here we generalize the original semilocal theory (which was based on the Hopf bundle S3 S â†’ S2) to realize the next Hopf bundle S7 S â†’ S4, and its extensions S2n+1 S â†’ HP. The semilocal defects in this class of theories are classified by Ï€3(S 3), andâ€¦ (More)

Massless interacting scalar fields in de Sitter space have long been known to experience large fluctuations over length scales larger than Hubble distances. A similar situation arises in condensed matter physics in the vicinity of a critical point, and in this betterunderstood situation these large fluctuations indicate the failure in this regime ofâ€¦ (More)

D. Boyanovsky, H.J. de Vega, R. Holman and J. F. J. Salgado (a) Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA. 15260, U.S.A. (b) LPTHE, âˆ— UniversitÃ© Pierre et Marie Curie (Paris VI) et Denis Diderot (Paris VII), Tour 16, 1er. Ã©tage, 4, Place Jussieu 75252 Paris, Cedex 05, France (c) Department of Physics, Carnegie Mellonâ€¦ (More)

Perturbative corrections to correlation functions for interacting theories in de Sitter spacetime often grow secularly with time, due to the properties of fluctuations on super-Hubble scales. This growth can lead to a breakdown of perturbation theory at late times. We argue that Dynamical Renormalization Group (DRG) techniques provide a convenient frameworkâ€¦ (More)

- Hael Collins, Richard Holman, Matthew R. Martin
- Physical review letters
- 2003

When the interbrane separation in the compact Randall-Sundrum model is stabilized using the Goldberger-Wise mechanism, a potential is generated for the four-dimensional field, the radion, that encodes this separation. Coherent oscillations of the radion in the early universe will produce an exponential growth in the number of brane particles due toâ€¦ (More)

We study the process whereby quantum cosmological perturbations become classical within inflationary cosmology. By setting up a master-equation formulation we show how quantum coherence for super-Hubble modes can be destroyed by its coupling to the environment provided by sub-Hubble modes. We identify what features the sub-Hubble environment must have inâ€¦ (More)

We examine various solutions of the strong-CP problem to determine their sensitivity to possible violations of global symmetries by Planck scale physics. While some solutions remain viable even in the face of such effects, violations of the Pecceiâ€“Quinn (PQ) symmetry by non-renormalizable operators of dimension less than 10 will generally shift the value ofâ€¦ (More)