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in subjects: "Universe"

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Cosmological Constraints on the Properties of Weakly Interacting Massive Particles

Considerations of the age and density of, as well as the evolution of structure in, the Universe lead to constraints on the masses and lifetimes of weakly interacting massive particles (WIMPs). 26 references.

Date: October 1, 1984

Creator: Steigman, G. & Turner, M. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Origin of cosmological density fluctuations

The density fluctuations required to explain the large-scale cosmological structure may have arisen spontaneously as a result of a phase transition in the early Universe. There are several ways in which such fluctuations may have ben produced, and they could have a variety of spectra, so one should not necessarily expect all features of the large-scale structure to derive from a simple power law spectrum. Some features may even result from astrophysical amplification mechanisms rather than grav… more

Date: November 1, 1984

Creator: Carr, B.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Dark matter in the Universe

What is the quantity and composition of material in the universe This is one of the most fundamental questions we can ask about the universe, and its answer bears on a number of important issues including the formation of structure in the universe, and the ultimate fate and the earliest history of the universe. Moreover, answering this question could lead to the discovery of new particles, as well as shedding light on the nature of the fundamental interactions. At present, only a partial answer… more

Date: March 1, 1991

Creator: Turner, M.S. (Fermi National Accelerator Lab., Batavia, IL (USA) Chicago Univ., IL (USA). Enrico Fermi Inst.)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Effect of inflation on anisotropic cosmologies

The effects of anisotropic cosmologies on inflation are studied. By properly formulating the field equations it is possible to show that any model that undergoes sufficient inflation will become isotropic on scales greater than the horizon today. Furthermore, we shall show that it takes a very long time for anisotropies to become visible in the observable part of the Universe. It is interesting to note that the time scale will be independent of the Bianchi Model and of the initial anisotropy. 6… more

Date: March 1, 1986

Creator: Jensen, L.G. & Stein-Schabes, J.A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Finite Temperature Instability for Compactification

We consider finite temperature effects upon theories with extra dimensions compactified via vacuum stress energy (Casimir) effects. For sufficiently high temperature, a static configuration for the internal space is impossible. At somewhat lower temperatures, there is an instability due to thermal fluctuations of radius of the compact dimensions. For both cases, the Universe can evolve to a de Sitter-like expansion of all dimensions. Stability to late times constrains the initial entropy of the… more

Date: March 1, 1986

Creator: Accetta, F. S. & Kolb, E. W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Cosmic relics from the big bang

A brief introduction to the big bang picture of the early universe is given. Dark matter is discussed; particularly its implications for elementary particle physics. A classification scheme for dark matter relics is given. 21 refs., 11 figs., 1 tab.

Date: December 1, 1988

Creator: Hall, L.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Physics at the superconducting supercollider

Summary of lectures presented in the Shell Seminar Series at the national convention of the National Science Teachers Association, April 7-10, 1988. Topics covered are: The Standard model, symmetry breaking, the superconducting supercollider, physics at the TEV scale, and the early universe.

Date: May 23, 1988

Creator: Gaillard, M. K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Neutrino number of the universe

The influence of grand unified theories on the lepton number of the universe is reviewed. A scenario is presented for the generation of a large (>> 1) lepton number and a small (<< 1) baryon number. 15 references.

Date: August 10, 1981

Creator: Kolb, E.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Possible Significance of a New Dimensionless Ratio in Cosmology

Observations suggest that the mass density of the Universe is dominated, not by ordinary matter, but by exotic particles which are a relic of the Big Bang. In this case, a new dimensionless cosmological ratio arises, the ratio of the mass density in ordinary matter to that in exotic matter, whose value is about 0.1. A priori it might seem remarkable that this ratio should be so close to unity. However, we point out that, for many exotic dark matter candidates, the ratio is related to the fundam… more

Date: May 1, 1986

Creator: Turner, M. S. & Carr, B. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Double Inflation

The Zel'dovich spectrum of adiabatic density perturbations is a generic prediction of inflation. There is increasing evidence that when the spectrum is normalized by observational data on small scales, there is not enough power on large scales to account for the observed large-scale structure in the Universe. Decoupling the spectrum on large and small scales could solve this problem. As a means of decoupling the large and small scales we propose double inflation (i.e., two episodes of inflation… more

Date: April 1, 1986

Creator: Silk, J. & Turner, M. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Dark matter: Theoretical perspectives

I both review and make the case for the current theoretical prejudice: a flat Universe whose dominant constituent is nonbaryonic dark matter, emphasizing that this is still a prejudice and not yet fact. The theoretical motivation for nonbaryonic dark matter is discussed in the context of current elementary-particle theory, stressing that: (1) there are no dark matter candidates within the standard model of particle physics; (2) there are several compelling candidates within attractive extension… more

Date: January 1, 1993

Creator: Turner, M.S. (Chicago Univ., IL (United States). Enrico Fermi Inst. Fermi National Accelerator Lab., Batavia, IL (United States))

Item Type: Article

Partner: UNT Libraries Government Documents Department

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An analytic treatment for a model of superclustering in the universe

Recently, Weinberg, Ostriker, and Dekel (WOD) have proposed a model of many spherical explosions which reproduces the large scale structure of the universe quite well. Because of the success of the model, we have developed an analytic treatment which gives the cluster-cluster correlation function and the cluster mass distribution in terms of the distribution of radii of the spherical voids. We also derive an expression for the distribution in terms of the cluster mass distribution. Thus, the cl… more

Date: January 1, 1989

Creator: Kulsrud, R.M. & Cowley, S.C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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The dialogue between particle physics and cosmology

In the last decade, a very close relationship has developed between particle physics and cosmology. The purpose of these lectures is to introduce particle physicists to the many scientific connections between the two fields. Before entering into the discussion of specific topics, it will first be shown that particle physics and cosmology are completely interdependent. 173 refs., 35 figs., 5 tabs.

Date: April 1, 1988

Creator: Sadoulet, B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Decaying Particles Do Not Heat Up the Universe

It is usually assumed that a massive relic species, which comes to dominate the mass density of the Universe and later decays, heats up the Universe when the age of the Universe approx. = its lifetime. We show that if its decay follows the usual exponential decay law, then the Universe is never reheated, rather it tust cools more slowly. We calculate the evolution of the temperature and entropy, and find that to within numerical factors of order unity, the usual estimates for the entropy increa… more

Date: September 1, 1984

Creator: Scherrer, R. J. & Turner, M. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Quantum ontologies

Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988.… more

Date: December 1, 1988

Creator: Stapp, Henry P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The Best-Fit Universe

Inflation provides very strong motivation for a flat Universe, Harrison-Zel'dovich (constant-curvature) perturbations, and cold dark matter. However, there are a number of cosmological observations that conflict with the predictions of the simplest such model -- one with zero cosmological constant. They include the age of the Universe, dynamical determinations of {Omega}, galaxy-number counts, and the apparent abundance of large-scale structure in the Universe. While the discrepancies are not y… more

Date: October 1, 1990

Creator: Turner, Michael S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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An analytic description of thick-wall bubbles

A new approximation scheme to the false-vacuum decay is suggested. In this scheme the bounce solutions can be obtained in an explicit and analytic way even for thick-wall bubbles. The result is compared with Coleman's thin-wall description, which shows that is nicely comprises the result of the latter prescription. Some applications are also discussed.

Date: January 1, 1992

Creator: Hong, Jooyoo.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Energy and Technology Review

Individual abstracts were prepared for the three items in this issue. These include age estimation of the universe, measurement of equations of state for tantalum, and inertial confinement fusion. (GHT)

Date: December 1, 1982

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Phase transitions as the origin of large scale structure in the universe

A review of the formation of large scale structure through gravitational growth of primordial perturbations is given. This is followed by a discussion of how symmetry breaking phase transitions in the early universe might have produced the required perturbations, in particular through the formation and evolution of a network of cosmic strings. Finally the statistical mechanics of string networks, for both cosmic and fundamental strings is discussed, leading to some more speculative ideas on the… more

Date: August 1, 1988

Creator: Turok, N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nuclear Constraints on the Age of the Universe

In this paper a review is made of how one can use nuclear physics to put rather stringent limits on the age of the universe and thus the cosmic distance scale. As the other papers in this session have demonstrated there is some disagreement on the distance scale and thus the limits on the age of the universe (if the cosmological constant ..lambda.. = 0). However, the disagreement is only over the last factor of 2, the basic timescale seems to really be remarkably well agreed upon. The universe … more

Date: December 1, 1982

Creator: Schramm, D. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The meaning of EROS/MACHO

Most of the mass density in the Universe and in the halo of our own galaxy -- exists in the form of dark matter. Overall, the contribution of luminous matter (in stars) to the mass density of the Universe is less than 1%; primordial nucleosynthesis indicates that baryons contribute between 1% and 10% of the critical density (0.01h{sup {minus}2} {approx_lt} {Omega}{sub B} {approx_lt} 0.02h{sup {minus}2}; h = the Hubble constant in units of 100 kms{sup {minus}1}Mpc{sup {minus}1}); and other evide… more

Date: November 1, 1993

Creator: Turner, M. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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The influence of CDM on the dynamical estimate of {Omega} in the local neighborhood

Peebles has suggested an interesting method to trace back in time positions of galaxies called the least action method. This method applied on the Local Group galaxies seems to indicate that we live in an {Omega}{approx} 0.1 Universe. We have studied a CDM N-body simulation with {Omega} = 0.2 and H = 50kms{sup {minus}1}/Mpc and compare trajectories traced back from the Least Action Principle and the center of mass of the particle forming CDM halos. We have shown that the agreement between these… more

Date: December 31, 1994

Creator: Dunn, A. M. & Laflamme, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Data acquisition systems for the Sloan Digital Sky Survey

The Sloan Digital Sky Survey (SDSS) will image {Pi} steradians about the north galactic cap in five filters, and acquire one million spectra using a dedicated 2.5 meter telescope at the Apache Point Observatory in New Mexico. The authors describe the data acquisition system for the survey`s three main detectors: an imaging camera, mounting 54 Tektronix charge-coupled devices (CCD); a pair of spectrographs, each mounting a pair of CCDs; and a smaller monitor telescope camera. The authors describ… more

Date: March 1, 1994

Creator: Petravick, D.; Berman, E.; MacKinnon, B.; Nicinski, T.; Pordes, R.; Sergey, G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Predictions of a non-Gaussian model for large scale structure

A modified CDM model for the origin of structure in the universe based on an inflation model with two interacting scalar fields, is analyzed to make predictions for the statistical properties of the density and velocity fields and the microwave background anisotropy. The initial gauge-invariant potential {zeta} which is defined as {zeta} = {delta}{rho}/({rho} + p) + 3{var_phi}, where {var_phi} is the curvature perturbation amplitude and p is the pressure, is the sum of a Gaussian field {phi}{su… more

Date: June 26, 1992

Creator: Fan, Z. H. & Bardeen, J. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department