arXiv subjects

M. Trodden

Publications and source records attributed to M. Trodden.

10 recordsLinked to original sources

arXiv2006

Brane Cosmology in an Arbitrary Number of Dimensions

We derive the effective cosmological equations for a non-$\mathbb{Z}_2$ symmetric codimension one brane embedded in an arbitrary D-dimensional bulk spacetime, generalizing the $D=5,6$ cases much studied previously. As a particular case, this may be considered as a regularized codimension (D-4) brane avoiding the problem of curvature divergence on the brane. We apply our results to the case of spherical symmetry around the brane and to partly compactified AdS-Schwarzschild bulks.

gr-qc↗

arXiv1996

Cosmic Vortons and Particle Physics Constraints

We investigate the cosmological consequences of particle physics theories that admit stable loops of superconducting cosmic string - {\it vortons}. General symmetry breaking schemes are considered, in which strings are formed at one energy scale and subsequently become superconducting in a secondary phase transition at what may be a considerably lower energy scale. We estimate the abundances of the ensuing vortons, and thereby derive constraints on the relevant particle physics models from cosmological observations. These constraints significantly restrict the category of admissible Grand Unified theories, but are quite compatible with recently proposed effects whereby superconducting strings may have been formed close to the electroweak phase transition.

hep-ph↗

arXiv1995

Decaying Vacuum Energy and Deflationary Cosmology in Open and Closed Universes

We consider a nonsingular deflationary cosmological model with decaying vacuum energy density in universes of arbitrary spatial curvature. Irrespective of the value of $k$, the models are characterized by an arbitrary time scale $H_I^{-1}$ which determines the initial temperature of the universe and the largest value of the vacuum energy density, the slow decay of which generates all the presently observed matter-energy of the universe. If $H_I^{-1}$ is of the order of the Planck time, the models begin with the Planck temperature and the present day value of the cosmological constant satisfies $Λ_I/Λ_0 \simeq 10^{118}$ as theoretically suggested. It is also shown that all models allow a density parameter $Ω_0 <2/3$ and that the age of the universe is large enough to agree with observations even with the high value of $H_0$ suggested by recent measurements.

astro-ph↗

arXiv1994

Particle Physics Models, Topological Defects and Electroweak Baryogenesis

We demonstrate the viability of electroweak baryogenesis scenarios in which the necessary departure from equilibrium is realized by the evolution of a network of topological defects. We consider several effective models of TeV physics, each addressing a fundamental particle physics problem, and in which the conditions necessary for defect-mediated electroweak baryogenesis are naturally satisfied. In each case we compare the strength of the model with that expected from scenarios in which baryogenesis proceeds with the propagation of critical bubbles.

hep-ph↗

arXiv1994

Singularity-Free Two Dimensional Cosmologies

We present a class of theories of two dimensional gravity which admits homogeneous and isotropic solutions that are nonsingular and asymptotically approach a FRW matter dominated universe at late times. These models are generalizations of two dimensional dilaton gravity and both vacuum solutions and those including conformally coupled matter are investigated. In each case our construction leads to an inflationary stage driven by the gravitational sector. Our work comprises a simple example of the `Nonsingular Universe' constructions of ref. [1].

gr-qc↗

arXiv1994

Electroweak Baryogenesis with Topological Defects

Electroweak baryogenesis has become a topic of much recent activity [1]. Here we discuss a new scenario which has the advantage of being insensitive to the order of the electroweak phase transition. We briefly review a mechanism [2] using unstable electroweak strings [3] and discuss in detail a mechanism [4] using topological defects (in particular cosmic strings) left behind after a previous phase transition.

hep-ph↗

arXiv1994

Cosmic Strings and Electroweak Symmetry Restoration in the Two-Higgs Doublet Model

We investigate the region of restored electroweak symmetry around a superconducting cosmic string coupled to the Weinberg-Salam model with an extra Higgs doublet. We show that the presence of the extra Higgs fields, and in particular their CP violating relative phase, does not qualitatively affect the results of Perkins and Davis[1] obtained for the standard electroweak theory. This result is neccessary to ensure the validity of some recently proposed string-mediated electroweak baryogenesis scenarios.

hep-ph↗

arXiv1994

Cosmic Strings and Electroweak Baryogenesis

The electroweak symmetry is unbroken in the core of cosmic strings originating from a symmetry breaking at an energy higher than the electroweak scale $η_{EW}$. The dynamics of such strings may generate a baryon asymmetry below the electroweak symmetry breaking scale. This mechanism for electroweak baryogenesis is most efficient if the scale of string formation is only slightly higher than $η_{EW}$ \eg \ in theories of dynamical symmetry breaking) and if the strings are superconducting. The mechanism is also effective if the electroweak phase transition is second order.

hep-ph↗

arXiv1993

A Nonsingular Two Dimensional Black Hole

We construct a model of gravity in 1+1 spacetime dimensions in which the solutions approach the Schwarzschild metric at large $r$ and de Sitter space far inside the horizon. Our model may be viewed as a two dimensional application of the `Limiting Curvature Construction' recently proposed by two of the authors.

hep-th↗

arXiv1993

Gamma Ray Bursts from Ordinary Cosmic Strings

We give an upper estimate for the number of gamma ray bursts from ordinary (non-superconducting) cosmic strings expected to be observed at terrestrial detectors. Assuming that cusp annihilation is the mechanism responsible for the bursts we consider strings arising at a GUT phase transition and compare our estimate with the recent BATSE results. Further we give a lower limit for the effective area of future detectors designed to detect the cosmic string induced flux of gamma ray bursts.

hep-ph↗