arXiv subjects

Matthew R. Martin

Publications and source records attributed to Matthew R. Martin.

12 recordsLinked to original sources

arXiv2025

An Extended-MHD Model for Handling Low-density Plasmas with Tabular Material Models

An extended-MHD model, interfaced with tabular equation-of-state and conductivity models, has been developed in PERSEUS (Physics as an Extended-MHD Relaxation System with an Efficient Upwind Scheme) for simulating a plasma-vacuum interface under experimentally-relevant conditions for a pulsed-power system, and with minimal sensitivity to parameters characterizing the numerical vacuum. For several test problems, we demonstrate convergence of this model for sufficiently low density floors and with respect to certain vacuum parameters. This capability is crucial for predictively modeling the coupling of energy and current onto a target in a pulsed-power system.

physics.plasm-ph↗

arXiv2006

Chiral Lattice Gauge Theories from Warped Domain Walls and Ginsparg-Wilson Fermions

We propose a construction of a 2-dimensional lattice chiral gauge theory. The construction may be viewed as a particular limit of an infinite warped 3-dimensional theory. We also present a "single-site'' construction using Ginsparg-Wilson fermions which may avoid, in both 2 and 4 dimensions, the problems of waveguide-Yukawa models.

hep-lat↗

arXiv2006

Counting Pockets with World Lines in Eternal Inflation

We consider the long standing puzzle of how to obtain meaningful probabilities in eternal inflation. We demonstrate a new algorithm to compute the probability distribution of pocket universe types, given a multivacua inflationary potential. The computed probability distribution is finite and manifestly gauge-independent. We argue that in some scenarios this technique can be applied to disfavor some eternally inflating potentials.

astro-ph↗

arXiv2005

Towards a chiral gauge theory by deconstruction in AdS5

We describe an implementation of a deconstructed gauge theory with charged fermions defined on an interval in five dimensional AdS space. The four dimensional slices are Minkowski, and the end slices support four dimensional chiral zero modes. In such a theory, the energy scales warp down as we move along the fifth dimension. If we augment this theory with localized neutral 4-dimensional Majorana fermions on the low energy end, and implement a Higgs mechanism there, we can arrange the theory such that the lightest gauge boson mode and the chiral mode on the wall at the high energy end are parametrically lighter than all the other states in the theory. If this semiclassical construction does not run into problems at the quantum level, this may provide an explicit construction of a chiral gauge theory. Instanton effects are expected to make the gauge boson heavy only if the resulting effective theory is anomalous.

hep-lat↗

arXiv2005

Warped Domain Wall Fermions

We consider Kaplan's domain wall fermions in the presence of an Anti-de Sitter (AdS) background in the extra dimension. Just as in the flat space case, in a completely vector-like gauge theory defined after discretizing this extra dimension, the spectrum contains a very light charged fermion whose chiral components are localized at the ends of the extra dimensional interval. The component on the IR boundary of the AdS space can be given a large mass by coupling it to a neutral fermion via the Higgs mechanism. In this theory, gauge invariance can be restored either by taking the limit of infinite proper length of the extra dimension or by reducing the AdS curvature radius towards zero. In the latter case, the Kaluza-Klein modes stay heavy and the resulting classical theory approaches a chiral gauge theory, as we verify numerically. Potential difficulties for this approach could arise from the coupling of the longitudinal mode of the light gauge boson, which has to be treated non-perturbatively.

hep-lat↗

arXiv2005

Boundary Localized Symmetry Breaking and Topological Defects

We discuss the structure of topological defects in the context of extra dimensions where the symmetry breaking terms are localized. These defects develop structure in the extra dimension which differs from the case where symmetry breaking is not localized. This new structure can lead to corrections to the mass scale of the defects which is not captured by the effective theory obtained by integrating out the extra dimension. We also consider the Higgsless model of symmetry breaking and show that no finite energy defects appear in some situations where they might have been expected.

hep-ph↗

arXiv2003

The enhancement of inflaton loops in an alpha-vacuum

While inflaton loops in the Euclidean vacuum generally have a negligible contribution to the power spectrum, loop effects can be substantially larger when the inflaton is in a non-thermal vacuum state. As an example, we show that in a truncated alpha-vacuum these loop effects are enhanced by the ratio of the Planck scale to the Hubble scale during inflation. The details of the inflationary models determine whether the coupling constants suppress the loop corrections relative to the tree level result.

hep-ph↗

arXiv2003

The Fate of the Alpha-Vacuum

de Sitter space-time has a one complex parameter family of invariant vacua for the theory of a free, massive scalar field. For most of these vacua, in an interacting scalar theory the one loop corrections diverge linearly for large values of the loop momentum. These divergences are not of a form that can be removed by a de Sitter invariant counterterm, except in the case of the Euclidean, or Bunch-Davies, vacuum.

hep-th↗

arXiv2003

Radion Induced Baryogenesis

Recent work in two brane Randall-Sundrum models has shown that the radion can drive parametric amplification of particles on the TeV brane leading to a stage of cosmology similar to preheating. We consider radion induced preheating as a mechanism for electroweak scale baryogenesis and estimate the baryon to entropy ratio for some regions of parameter space. We also predict an upper bound for the radion mass which makes this baryogenesis mechanism testable. Finally, we verify some assumptions with numerical calculations of the 1+1 dimensional Abelian Higgs model.

hep-ph↗

arXiv2002

Radion Induced Brane Preheating

When the interbrane separation in compact Randall-Sundrum models is stabilized via the Goldberger-Wise mechanism, a potential is generated for the four dimensional field that encodes this geometric information, the so-called radion. Due to its origin as a part of the full five dimensional metric, the radion couples directly to particles on both branes. We exhibit the exponential growth in the number of brane particles due to parametric amplification from radion oscillations and discuss some of the consequences of this process for brane cosmology.

hep-ph↗

arXiv2002

RS1 Cosmology as Brane Dynamics in an AdS/Schwarzschild Bulk

We explore various facets of the cosmology of the Randall-Sundrum scenario with two branes by considering the dynamics of the branes moving in a bulk AdS/Schwarzschild geometry. This approach allows us both to understand in more detail and from a different perspective the role of the stabilization of the hierarchy in the brane cosmology, as well as to extend to the situation where the metric contains a horizon. In particular, we explicitly determine how the Goldberger-Wise stabilization mechanism perturbs the background bulk geometry to produce a realistic cosmology.

hep-ph↗

arXiv2001

Non-Equilibrium Large N Yukawa Dynamics: marching through the Landau pole

The non-equilibrium dynamics of a Yukawa theory with N fermions coupled to a scalar field is studied in the large N limit with the goal of comparing the dynamics predicted from the renormalization group improved effective potential to that obtained including the fermionic backreaction. The effective potential is of the Coleman-Weinberg type. Its renormalization group improvement is unbounded from below and features a Landau pole. When viewed self-consistently, the initial time singularity does not arise. The different regimes of the dynamics of the fully renormalized theory are studied both analytically and numerically. Despite the existence of a Landau pole in the model, the dynamics of the mean field is smooth as it passes the location of the pole. This is a consequence of a remarkable cancellation between the effective potential and the dynamical chiral condensate. The asymptotic evolution is effectively described by a quartic upright effective potential. In all regimes, profuse particle production results in the formation of a dense fermionic plasma with occupation numbers nearly saturated up to a scale of the order of the mean field. This can be interpreted as a chemical potential. We discuss the implications of these results for cosmological preheating.

hep-ph↗