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Edward W. Kolb

Publications and source records attributed to Edward W. Kolb.

At least 91 records · Page 5Linked to original sources
arXiv1998

Superheavy dark matter

We show that in large-field inflationary scenarios, superheavy (many orders of magnitude larger than the weak scale) dark matter will be produced in cosmologically interesting quantities if superheavy stable particles exist in the mass spectrum. We show that these particles may be produced naturally during the transition from the inflationary phase to either a matter-dominated or radiation-dominated phase as a result of the expansion of the background spacetime acting on vacuum quantum fluctuations of the dark matter field. We find that as long as there are stable particles whose mass is of the order of the inflaton mass (presumably around $10^{13}$GeV), they will be produced in sufficient abundance to give $Ω_0 =1$ quite independently of any details of the non-gravitational interactions of the dark-matter field.

hep-ph↗
arXiv1998

On the reliability of inflaton potential reconstruction

If primordial scalar and tensor perturbation spectra can be inferred from observations of the cosmic background radiation and large-scale structure, then one might hope to reconstruct a unique single-field inflaton potential capable of generating the observed spectra. In this paper we examine conditions under which such a potential can be reliably reconstructed. For it to be possible at all, the spectra must be well fit by a Taylor series expansion. A complete reconstruction requires a statistically-significant tensor mode to be measured in the microwave background. We find that the observational uncertainties dominate the theoretical error from use of the slow-roll approximation, and conclude that the reconstruction procedure will never insidiously lead to an irrelevant potential.

astro-ph↗
arXiv1997

Are ultrahigh energy cosmic rays signals of supersymmetry?

We investigate the possibility that cosmic rays of energy larger than the Greisen-Zatsepin-Kuzmin cutoff are not nucleons, but a new stable, massive, hadron that appears in many extensions of the standard model. We focus primarily on the S^0, a uds-gluino bound state. The range of the S^0 through the cosmic background radiation is significantly longer than the range of nucleons, and therefore can originate from sources at cosmoglogical distances.

astro-ph↗
arXiv1997

Ribbons on the CBR Sky: A Powerful Test of a Baryon Symmetric Universe

If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the Cosmic Background Radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width $θ_W\sim 0.1^\circ$, separated by angle $θ_L\simeq 1^\circ(L/100h^{-1}{Mpc})$ where L is the characteristic domain size, and y-distortion parameter $y \approx 10^{-6}$. Such a pattern could potentially be detected by the high-resolution CBR anisotropy experiments planned for the next decade, and such experiments may finally settle the question of whether or not our Hubble volume is baryon symmetric.

astro-ph↗
arXiv1997

On the relic abundance of light photinos

We solve the coupled Boltzmann equation for the system of light photinos interacting with pions and $R^0$'s (the gluon-gluino bound state) to determine the relic abundance of light photinos in the light gaugino scenario. Cosmology bounds the ratio r of the R^0 mass to the photino mass to be less than about 1.8. We also use a model Lagrangian embodying crossing symmetry between the $R^0 \leftrightarrow \photino ππ$ and $R^0 π\leftrightarrow \photino π$ reactions to identify cosmologically favored regions of $R^0$ lifetime as a function of $R^0$ and photino masses.

astro-ph↗
arXiv1997

Evolution of the Order Parameter after Bubble Collisions

If a first-order phase transition is terminated by collisions of new-phase bubbles, there will exist a period of nonequilibrium between the time bubbles collide and the time thermal equilibrium is established. We study the behavior of the order parameter during this phase. We find that large nonthermal fluctuations at this stage tend to restore symmetry, i.e., the order parameter is smaller than its eventual thermal equilibrium value. We comment on possible consequences for electroweak baryogenesis.

astro-ph↗
arXiv1997

Cosmic microwave background measurements can discriminate among inflation models

Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosmic microwave background (CMB). Observations of CMB anisotropies can be used to falsify many currently popular models. In this paper we discuss the prospectus for observations of CMB anisotropies at the accuracy of planned satellite missions to reject currently popular inflation models and to provide some direction for model building.

astro-ph↗
arXiv1996

Inflation in the Postmodern Era

In this lecture I will review some recent progress in improving the accuracy of the calculation of density perturbations resulting from inflation.

astro-ph↗
arXiv1996

GUT Baryogenesis after Preheating

At the end of inflation the universe is frozen in a near zero-entropy state with energy density in a coherent scalar field and must be ``defrosted'' to produce the observed entropy and baryon number. We propose that the baryon asymmetry is generated by the decay of supermassive Grand Unified Theory (GUT) bosons produced non-thermally in a preheating phase after inflation. We show that baryogenesis is possible for an inflaton masses of order 10^{13} GeV and a GUT Higgs boson mass of order 10^{14} GeV, thus solving many drawbacks facing GUT baryogenesis in the old reheating scenario.

hep-ph↗
arXiv1996

Searching for stellar mass black holes in the solar neighborhood

We propose a strategy for searching for isolated stellar mass black holes in the solar neighborhood with the Sloan Digital Sky Survey. Due to spherical accretion of the inter-stellar medium and the ambient magnetic field, an isolated black hole is expected to emit a blended, thermal synchrotron spectrum with a roughly flat peak from the optical down to the far infra-red. We find that the Sloan Survey will be able to detect isolated black holes, in the considered mass range of 1--100$M_{\odot}$, out to a few hundred parsecs, depending on the local conditions of the ISM. We also find that the black holes are photmetrically distinguishable from field stars and they have a photometry similar to QSOs. They can be further singled out from QSO searches because they have a featureless spectrum with no emission lines. The Sloan Survey will likely find hundreds of objects that meet these criteria, and to further reduce the number of candidates, we suggest other selection criteria such as infra-red searches and proper motion measurements. Estimates indicate that dozens of black holes may exist out to a few hundred parsecs. If no black hole candidates are found in this survey, important limits can be placed on the local density of black holes and the halo fraction in black holes, especially for masses greater than about $20 M_{\odot}$.

astro-ph↗
arXiv1996

Cosmological Bounds to the Magnetic Moment of Heavy Tau Neutrinos

The magnetic moment of tau neutrinos in the MeV mass range may be large enough to modify the cosmological freeze-out calculation and determine the tau-neutrino relic density. In this paper we revisit such a possibility. We calculate the evolution and freeze-out of the tau neutrino number density as a function of its mass and magnetic moment. We then determine its relic density, then calculate its effect upon primordial nucleosynthesis including previously neglected effects.

astro-ph↗
arXiv1996

Preheating and symmetry restoration in collisions of vacuum bubbles

In first-order inflation a phase transition is completed by the collisions of expanding true-vacuum bubbles. If bubble collisions produce large numbers of soft scalar particles carrying quantum numbers associated with a spontaneously broken symmetry, then symmetry restoration may occur in a ``pre-heating'' phase in a manner similar to symmetry restoration in the pre-heating phase of slow-roll inflation. Since bubble collisions lead to inhomogeneities, there is the possibility of inhomogeneous symmetry restoration where restoration occurs only in the regions of wall collisions.

astro-ph↗
arXiv1996

Eternal annihilations of light photinos

In a class of low-energy supersymmetry models the photino is a natural dark matter candidate. We investigate the effects of post-freeze-out photino annihilations which can generate electromognetic cascades and lead to photo-destruction of $^4$He and subsequent overproduction of D and $^3$He. We also generalize our analysis to a generic dark matter component whose relic abundance is {\it not} determined by the cross section of the self-annihilations giving rise to electromagnetic showers.

astro-ph↗
arXiv1995

Modeling Thermal Fluctuations: Phase Mixing and Percolation

We consider the nonequilibrium dynamics of a a real scalar field in a degenerate double-well potential. The system is prepared in the lowest free energy state in one of the wells and the dynamics is driven by the coupling of the field to a thermal bath. Using a simple analytical model, based on the subcritical bubbles method, we compute the fraction of the total volume which fluctuates to the opposite phase as a function of the parameters of the potential. Furthermore, we show how complete phase mixing, {\em i.e.} symmetry restoration, is related to percolation, which is dynamically driven by domain instability. Our method describes quantitatively recent results obtained by numerical simulations, and is applicable to systems in the Ising universality class.

cond-mat↗
arXiv1995

LIGHT PHOTINOS AS DARK MATTER

There are good reasons to consider models of low-energy supersymmetry with very light photinos and gluinos. In a wide class of models the lightest $R$-odd, color-singlet state containing a gluino, the $\r0$, has a mass in the 1-2 GeV range and the slightly lighter photino, $\pho$, would survive as the relic $R$-odd species. For the light photino masses considered here, previous calculations resulted in an unacceptable photino relic abundance. But we point out that processes other than photino self-annihilation determine the relic abundance when the photino and $R^0$ are close in mass. Including $\r0\longleftrightarrow\pho$ processes, we find that the photino relic abundance is most sensitive to the $\r0$-to-$\pho$ mass ratio, and within model uncertainties, a critical density in photinos may be obtained for an $\r0$-to-$\pho$ mass ratio in the range 1.2 to 2.2. We propose photinos in the mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a strategy to test the hypothesis.

astro-ph↗
arXiv1994

Testing Inflation with the Cosmic Microwave Background

Cosmic microwave background (CMB) anisotropy may result from both scalar and tensor perturbations. For a sufficiently narrow range of angular scales, CMB perturbations can be characterized by four parameters. Results from the Cosmic Background Explorer fix one combination of the parameters, reducing the parameters to three. If CMB perturbations are from inflation, there is an additional relation, reducing the parameters to two. An appropriate combination of a medium-angle and a small-angle CMB observation can test the inflation hypothesis because inflation cannot explain a high signal in one experiment and a low signal in the other.

astro-ph↗
arXiv1994

Relating Spectral Indices to Tensor and Scalar Amplitudes in Inflation

Within an expansion in slow-roll inflation parameters, we derive the complete second-order expressions relating the ratio of tensor to scalar density perturbations and the spectral index of the scalar spectrum. We find that ``corrections'' to previously derived formulae can dominate if the tensor to scalar ratio is small. For instance, if $V V''/(V')^2\neq 1$ or if $m_{Pl}^2/(4π) ~|V'''/V'|\ga 1$, where $V(ϕ)$ is the inflaton potential and $m_{Pl}$ is the Planck mass, then the previously used simple relations between the indices and the tensor to scalar ratio fails. This failure occurs in particular for natural inflation, Coleman--Weinberg inflation, and ``chaotic'' inflation.

astro-ph↗