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M. S. Turner

Publications and source records attributed to M. S. Turner.

26 records · Page 2Linked to original sources
arXiv1993

Why is the Temperature of the Universe 2.726K?

NASA's Cosmic Background Explorer (COBE) Satellite has recently made the most accurate measurement of the temperature of the Universe determining it to be $2.726\pm 0.01\,$K. In trying to understand why the temperature has this value, one is led to discover the most fundamental features of the Universe---an early, radiation-dominated epoch, enormous entropy per nucleon, synthesis of the light elements around three minutes after the bang, and a small excess of matter over antimatter---as well as some of the most pressing issues in cosmology today, the development of structure in the Universe and the identification of the nature of the ubiquitous dark matter.

astro-ph↗
arXiv1993

Recovering the Inflationary Potential

A procedure is developed for the recovery of the inflationary potential over the interval that affects astrophysical scales ($\approx 1\Mpc - 10^4\Mpc$). The amplitudes of the scalar and tensor metric perturbations and their power-spectrum indices, which can in principle be inferred from large-angle CBR anisotropy experiments and other cosmological data, determine the value of the inflationary potential and its first two derivatives. From these, the inflationary potential can be reconstructed in a Taylor series and the consistency of the inflationary hypothesis tested. A number of examples are presented, and the effect of observational uncertainties is discussed.

astro-ph↗
arXiv1993

On the Production of Scalar and Tensor Perturbations in Inflationary Models

The amplitude and spectrum of the scalar and tensor perturbations depend upon the shape of the inflationary potential in the small interval where the scalar field responsible for inflation was between about 46 and 54 e-folds before the end of inflation. By expanding the inflationary potential in a Taylor series in this interval we show that the amplitude of the perturbations and the power-law slope of their spectra can be expressed in terms of the value of the potential 50 e-folds before the end of inflation, $V_{50}$, the steepness of the potential, $x_{50} \equiv \mpl V_{50}^\prime /V_{50}$, and the rate of change of the steepness, $x_{50}^\prime$ (prime denotes derivative with respect to the scalar field).

astro-ph↗
arXiv1993

Constraints on Dirac Neutrinos from SN 1987A

The Livermore Supernova Explosion Code was used to calculate the effect of a massive Dirac neutrino on neutrino emission from SN 1987A in a fully self-consistent manner. Spin-flip interactions lead to the copious emission of sterile, right-handed neutrinos and cool the core faster than the observed neutrino emission time for Dirac masses exceeding about 3$\,$keV. This limit is relaxed to $7\,$keV if pion emission processes in the core are neglected. These limits are compared with the previous less stringent limits of Burrows et al.

astro-ph↗
arXiv1992

Effect of Neutrino Heating on Primordial Nucleosynthesis

We have modified the standard code for primordial nucleosynthesis to include the effect of the slight heating of neutrinos by $e^\pm$ annihilations. There is a small, systematic change in the $^4$He yield, $ΔY \simeq +1.5\times 10^{-4}$, which is insensitive to the value of the baryon-to-photon ratio $η$ for $10^{-10}\la η\la 10^{-9}$. We also find that the baryon-to-photon ratio decreases by about 0.5\% less than the canonical factor of 4/11 because some of the entropy in $e^\pm$ pairs is transferred to neutrinos. These results are in accord with recent analytical estimates.

astro-ph↗
arXiv1992

Inflation at the Electroweak Scale

We present a simple model for slow-rollover inflation where the vacuum energy that drives inflation is of the order of $G_F^{-2}$; unlike most models, the conversion of vacuum energy to radiation (``reheating'') is moderately efficient. The scalar field responsible for inflation is a standard-model singlet, develops a vacuum expectation value of the order of $4\times 10^6\GeV$, has a mass of order $1\GeV$, and can play a role in electroweak phenomena.

astro-ph↗
arXiv1992

Cosmic Microwave Background Probes Models of Inflation

Inflation creates both scalar (density) and tensor (gravity wave) metric perturbations. We find that the tensor mode contribution to the CMB anisotropy on large-angular scales can only exceed that of the scalar mode in models where the spectrum of perturbations deviates significantly from scale invariance (e.g., extended and power-law inflation models and extreme versions of chaotic inflation). If the tensor mode dominates at large-angular scales, then the value of $ΔT/T$ predicted on $1^\circ$ is less than if the scalar mode dominates, and, for cold dark matter models, $b>1$ can be made consistent with the COBE DMR results.

astro-ph↗