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Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
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 …
Production Of Cosmological Observables During The Inflationary Epoch, Cody Goolsby-Cole
Production Of Cosmological Observables During The Inflationary Epoch, Cody Goolsby-Cole
Doctoral Dissertations
This dissertation proposal explores the production of present day cosmological observables which might have been produced during the inflationary era. The first observable is the current net electric charge of our observable universe produced by charge fluctuations during inflation. Next, we examine the possibility of a signal in the primordial gravitational wave power spectrum produced by a scalar field with a time dependent mass. Finally, we examine primordial magnetic fields produced during inflation through the Ratra model coupling with the Schwinger effect.
Non-Vacuum Ads Cosmologies And The Approach To Equilibrium Of Entanglement Entropy, Sebastian Fischetti, David Kastor, Jennie Traschen
Non-Vacuum Ads Cosmologies And The Approach To Equilibrium Of Entanglement Entropy, Sebastian Fischetti, David Kastor, Jennie Traschen
David Kastor
We extend standard results for vacuum asymptotically locally AdS (AlAdS) spacetimes, showing that such spacetimes can be constructed as foliations where the induced metric on each hypersurface satisfies Einstein's equation with stress-energy. By an appropriate choice of stress-energy on the hypersurfaces, the resulting AlAdS spacetime satisfies Einstein's equation with a negative cosmological constant and physical stress tensor. We use this construction to obtain AlAdS solutions whose boundaries are FRW cosmologies sourced by a massless scalar field or by a perfect fluid obeying the strong energy condition. We focus on FRW universes that approach Minkowski spacetime at late times, yielding AlAdS …
The Morphology Of Passively Evolving Galaxies At Z ~ 2 From Hst/Wfc3 Deep Imagin In The Hubble Ultradeep Field, P Cassata, M Giavalisco, Yc Guo, H Ferguson, Am Koekemoer, A Renzini, A Fontana, S Salimbeni, M Dickinson, S Casertano, Cj Conselice, N Grogin, Jm Lotz, C Papovich, Ra Lucas, A Straughn, Jp Gardner, L Moustakas
The Morphology Of Passively Evolving Galaxies At Z ~ 2 From Hst/Wfc3 Deep Imagin In The Hubble Ultradeep Field, P Cassata, M Giavalisco, Yc Guo, H Ferguson, Am Koekemoer, A Renzini, A Fontana, S Salimbeni, M Dickinson, S Casertano, Cj Conselice, N Grogin, Jm Lotz, C Papovich, Ra Lucas, A Straughn, Jp Gardner, L Moustakas
Astronomy Department Faculty Publication Series
We present near–IR images, obtained with the Hubble Space Telescope (HST) and the WFC3/IR camera, of six passive and massive galaxies at redshift 1.3 < z < 2.4 (SSFR< 10−2 Gyr−1; stellar mass M ∼ 1011 M⊙), selected from the Great Observatories Origins Deep Survey (GOODS). These images, which have a spatial resolution of ∼ 1.5 kpc, provide the deepest view of the optical rest–frame morphology of such systems to date. We find that the light profile of these galaxies is regular and well described by a Sérsic model with index typical of today’s spheroids. Their size, however, …
Recovery Of The Power Spectrum Of Mass Fluctuations From Observations Of The Ly Alpha Forest, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Recovery Of The Power Spectrum Of Mass Fluctuations From Observations Of The Ly Alpha Forest, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Astronomy Department Faculty Publication Series
We present a method to recover the shape and amplitude of the power spectrum of mass fluctuations, P(k), from observations of the high-redshift Lyα forest. The method is motivated by the physical picture that has emerged from hydrodynamic cosmological simulations and related semianalytic models, in which typical Lyα forest lines arise in a diffuse, continuous, fluctuating intergalactic medium. The thermal state of this low-density gas (δρ/ρ 10) is governed by simple physical processes, which lead to a tight correlation between the Lyα optical depth and the underlying matter density. To recover the mass power spectrum, we (1) …
Intergalactic Helium Absorption In Cold Dark Matter Models, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Intergalactic Helium Absorption In Cold Dark Matter Models, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Astronomy Department Faculty Publication Series
Observations from the Hopkins Ultraviolet Telescope and the Hubble Space Telescope have recently detected He II absorption along the lines of sight to two high-redshift quasars. We use cosmological simulations with gas dynamics to investigate He II absorption in the cold dark matter (CDM) theory of structure formation. We consider two Ω = 1 CDM models with different normalizations and one open universe (Ω0 = 0.4) CDM model. The simulations incorporate the photoionizing UV background spectrum computed by Haardt & Madau, which is based on the output of observed quasars and reprocessing by the Lyα forest. The simulated …
Testing Cosmological Models Against The Abundance Of Damped Lyman-Alpha Absorbers, Jp Gardner, N Katz, Dh Weinberg, L Hernquist
Testing Cosmological Models Against The Abundance Of Damped Lyman-Alpha Absorbers, Jp Gardner, N Katz, Dh Weinberg, L Hernquist
Astronomy Department Faculty Publication Series
We calculate the number of damped Lyα absorbers expected in various popular cosmological models as a function of redshift and compare our predictions with observed abundances. The Press-Schechter formalism is used to obtain the distribution of halos with circular velocity in different cosmologies, and we calibrate the relation between circular velocity and absorption cross section using detailed gasdynamical simulations of a standard cold dark matter (CDM) model. Because of this calibration, our approach makes more realistic assumptions about the absorption properties of collapsed objects than previous, analytic calculations of the damped Lyα abundance. CDM models with Ω0 = 1, …