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Mark Trodden

Publications and source records attributed to Mark Trodden.

At least 163 records · Page 9Linked to original sources
arXiv1999

Baryogenesis Below The Electroweak Scale

We propose a new alternative for baryogenesis which resolves a number of the problems associated with GUT and electroweak scenarios, and which may allow baryogenesis even in modest extensions of the standard model. If the universe never reheats above the electroweak scale following inflation, GUT baryon production does not occur and at the same time thermal sphalerons, gravitinos and monopoles are not produced in abundance. Nevertheless, non-thermal production of sphaleron configurations via preheating could generate the observed baryon asymmetry of the universe.

hep-ph↗
arXiv1999

Causality and Cosmic Inflation

In the context of inflationary models with a pre-inflationary stage, in which the Einstein equations are obeyed, the weak energy condition is satisfied, and spacetime topology is trivial, we argue that homogeneity on super-Hubble scales must be assumed as an initial condition. Models in which inflation arises from field dynamics in a Friedman-Robertson-Walker background fall into this class but models in which inflation originates at the Planck epoch, {\it eg.} chaotic inflation, may evade this conclusion. Our arguments rest on causality and general relativistic constraints on the structure of spacetime. We discuss modifications to existing scenarios that may avoid the need for initial large-scale homogeneity.

gr-qc↗
arXiv1999

Recent Progress in Baryogenesis

We provide an up to date account of progress in understanding the origin of the observed baryon asymmetry of the universe. While our primary goal is to be current, we have attempted to give a pedagogical introduction to the primary areas of research in this field, giving a detailed description of the different scenarios. The very recent developments in GUT baryogenesis, leptogenesis, electroweak baryogenesis and the Affleck-Dine mechanism are presented. In particular, we focus on specific particle physics implementations, mostly in the context of supersymmetry, which lead to specific testable predictions.

hep-ph↗
arXiv1999

Dirichlet Solitons in Field Theories

I briefly describe a new class of soliton configurations in field theories. These consist of topological defects which can end when they intersect other defects of equal or higher dimensionality. Such configurations may be termed ``Dirichlet topological defects'', in analogy with the D-branes of string theory. I provide a specific example - cosmic strings that terminate on domain walls - and discuss some new directions for this work, including an interesting and qualitatively different extension to supersymmetric theories.

hep-th↗
arXiv1998

Electroweak Baryogenesis

Contrary to naive cosmological expectations, all evidence suggests that the universe contains an abundance of matter over antimatter. This article reviews the currently popular scenario in which testable physics, present in the standard model of electroweak interactions and its modest extensions, is responsible for this fundamental cosmological datum. A pedagogical explanation of the motivations and physics behind electroweak baryogenesis is provided, and analytical approaches, numerical studies, up to date developments and open questions in the field are also discussed.

hep-ph↗
arXiv1998

Creation and Structure of Baby Universes in Monopole Collisions

Under certain circumstances, the collision of magnetic monopoles, topologically locked-in regions of false vacuum, leads to topological inflation and the creation of baby universes. The future evolution of initial data represented by the two incoming monopoles may contain a timelike singularity but this need not be the case. We discuss the global structure of the spacetime associated with monopole collisions and also that of topological inflation. We suggest that topological inflation within magnetic monopoles leads to an eternally reproducing universe.

gr-qc↗
arXiv1998

CP Violation from Surface Terms in the Electroweak Theory without Fermions

We consider the effect of adding a CP-odd, theta FFdual-term to the electroweak Lagrangian without fermions. This term affects neither the classical nor perturbatively quantum physics, but can be observed through non-perturbative quantum processes. We give an example of such a process by modifying the theory so that it supports Higgs-winding solitons and showing that the rates of decay of these solitons to specific final states are CP violating. We also discuss how the CP symmetry is restored when fermions are included.

hep-ph↗
arXiv1998

Electroweak Baryogenesis: A Brief Review

A brief review of the fundamental ideas behind electroweak baryogenesis is presented. Since a successful implementation of these ideas requires an extension of the minimal standard model, I comment on the necessary physics and how experimental constraints make these scenarios testable at the LHC, and perhaps at existing colliders.

hep-ph↗
arXiv1998

Topological Inflation with Multiple Winding

We analyze the core dynamics of critically coupled, superheavy gauge vortices in the (2+1) dimensional Einstein-Abelian-Higgs system. By numerically solving the Eistein and field equations for various values of the symmetry breaking scale, we identify the regime in which static solutions cease to exist and topological inflation begins. We explicitly include the topological winding of the vortices into the calculation and extract the dependence on the winding of the critical scale separating the static and inflating regimes. Extrapolation of our results suggests that topological inflation might occur within high winding strings formed at the Grand Unified scale.

gr-qc↗
arXiv1998

Phase Transitions in the Core of Global Embedded Defects

We demonstrate the existence of global monopole and vortex configurations whose core exhibits a phase structure. We determine the critical values of parameters for which the transition from the symmetric to the non-symmetric phase occurs and discuss the novel dynamics implied by the non-symmetric cores for defect interactions. We model phase transitions in the core of global embedded topological defects by identifying the relevant parameters with the vacuum expectation value of a dynamical scalar field. Finally, we argue that superheavy defects that undergo a core phase transition in the very early universe provide a novel realization for topological inflation.

hep-ph↗
arXiv1997

Dirichlet Topological Defects

We propose a class of field theories featuring solitonic solutions in which topological defects can end when they intersect other defects of equal or higher dimensionality. Such configurations may be termed ``Dirichlet topological defects'', in analogy with the D-branes of string theory. Our discussion focuses on defects in scalar field theories with either gauge or global symmetries, in (3+1) dimensions; the types of defects considered include walls ending on walls, strings on walls, and strings on strings.

hep-th↗
arXiv1997

Cosmic Strings, Zero Modes and SUSY breaking in Nonabelian N=1 Gauge Theories

We investigate the microphysics of cosmic strings in Nonabelian gauge theories with N=1 supersymmetry. We give the vortex solutions in a specific example and demonstrate that fermionic superconductivity arises because of the couplings and interactions dictated by supersymmetry. We then use supersymmetry transformations to obtain the relevant fermionic zero modes and investigate the role of soft supersymmetry breaking on the existence and properties of the superconducting strings.

hep-ph↗
arXiv1997

Microphysics of Gauge Vortices and Baryogenesis

I give a brief overview of a novel mechanism for generating the baryon asymmetry of the universe at the electroweak scale. This scenario circumvents the need for a strongly first order electroweak phase transition by utilizing gauged topological solitons to realize the requisite departure from thermal equilibrium.

hep-ph↗
arXiv1997

Semi-Analytical Approaches to Local Electroweak Baryogenesis

We examine two semi-analytical methods for estimating the baryon asymmetry of the universe (BAU) generated in scenarios of ``local'' electroweak baryogenesis (in which the requisite baryon number violation and CP violation occur together in space and time). We work with the standard electroweak theory augmented by the addition of a CP violating dimension six operator. We work in the context of a first order phase transition, but the processes we describe can also occur during the evolution of a network of topological defects. Both the approaches we explore deal with circumstances where the bubble walls which convert the high temperature phase to the low temperature phase are thin and rapidly moving. We first consider the dynamics of localized configurations with winding number one which remain in the broken phase immediately after the bubble wall has passed. Their subsequent decay can anomalously produce fermions. In a prelude to our analysis of this effect, we demonstrate how to define the C and CP symmetries in the bosonic sector of the electroweak theory when configurations with nonzero winding are taken into account. Second, we consider the effect of the passage of the wall itself on configurations which happen to be near the crest of the ridge between vacua as the wall arrives. We find that neither of the simple approaches followed here can be pushed far enough to obtain a convincing estimate of the BAU which is produced. A large scale numerical treatment seems necessary.

hep-ph↗
arXiv1997

N=1 Supersymmetric Cosmic Strings

We investigate the microphysics of supersymmetric cosmic strings. In particular we focus on the vortices admitted by N=1 supersymmetric abelian Higgs models. We find the vortex solutions and demonstrate that the two simplest supersymmetric cosmic string models admit fermionic superconductivity. Further, by using supersymmetry transformations, we show how to solve for the fermion zero modes giving rise to string superconductivity in terms of the background string fields.

hep-ph↗
arXiv1995

Dynamical Breaking of CPT Symmetry in Defect Networks and Baryogenesis

Based on a study of {\it charge,} (C), {\it parity} (P) and {\it time reversal} (T) symmetries we show how a CP violating network of defects in the early Universe may bias baryon number production. A static network, even though it violates CP, respects CPT and hence does not bias baryon number production. On the other hand, the {\it ordering dynamics\/} of defects in a network, governed by the interplay of string tension, friction, inertia and the expansion of the Universe, results in the dynamical breakdown of CPT symmetry and may lead to a net baryon number production.

hep-ph↗
arXiv1994

Local and Nonlocal Defect-Mediated Electroweak Baryogenesis

We consider the effects of particle transport in the topological defect-mediated electroweak baryogenesis scenarios of Ref. 1. We analyze the cases of both thin and thick defects and demonstrate an enhancement of the original mechanism in both cases due to an increased effective volume in which baryogenesis occurs. This phenomenon is a result of imperfect cancellation between the baryons and antibaryons produced on opposite faces of the defect.

hep-ph↗