arXiv subjects

Ian G. Moss

Publications and source records attributed to Ian G. Moss.

At least 55 records · Page 3Linked to original sources

arXiv2013

Geometrical terms in the effective Hamiltonian for rotor molecules

An analogy between asymmetric rotor molecules and anisotropic cosmology can be used to calculate new centrifugal distortion terms in the effective potential of asymmetric rotor molecules which have no internal 3-fold symmetry. The torsional potential picks up extra $\cosα$ and $\cos2α$ contributions, which are comparable to corrections to the momentum terms in methanol and other rotor molecules with isotope replacements.

physics.chem-ph↗

arXiv2012

Anomalies, boundaries and the in-in formalism

In the context of quantum field theory, an anomaly exists when a theory has a classical symmetry which is not a symmetry of the quantum theory. This short exposition aims at introducing a new point of view, which is that the proper setting for anomaly calculations is the `in-in', or closed-time path formulation of quantum field theory. There are also some new results for anomalies in the context of boundary value problems, and a new correction to the $a_5$ heat-kernel coefficient.

hep-th↗

arXiv2012

Cosmological bounds on tachyonic neutrinos

Recent time-of-flight measurements on muon neutrinos in the OPERA neutrino oscillation experiment have found anomalously short times compared to the light travel-times, corresponding to a superluminal velocity, $v-1=2.37\pm0.32\times 10^{-5}$ in units where $c=1$. We show that cosmological bounds rule out an explanation involving a Lorentz invariant tachyonic neutrino. At the OPERA energy scale, nucleosynthesis constraints imply $v-1<0.86\times 10^{-12}$ and the Cosmic Microwave Background observations imply $v-1<7.1\times 10^{-23}$. The CMB limit on the velocity of a tachyon with an energy of 10 MeV is stronger than the SN1987A limit. Superluminal neutrinos that could be observed at particle accelerator energy scales would have to be associated with Lorentz symmetry violation.

astro-ph.CO↗

arXiv2011

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.

hep-th↗

arXiv2010

Balancing the vacuum energy in heterotic $M$-theory

Moduli stabilisation is explored in the context of low-energy heterotic $M$-theory to show that a small value of the cosmological constant can result from a balance between the negative potential energy left over from stabilising the moduli and a positive Casimir energy from the higher dimensions. Supersymmetry breaking is induced by the fermion boundary conditions on the two branes in the theory. An explicit calculation of the Casimir energy for the gravitino reveals that the energy has the correct sign, although the size of the contribution is close to the edge of the parameter range for which the calculation is valid.

hep-th↗

arXiv2009

Warm Inflation and its Microphysical Basis

The microscopic quantum field theory origins of warm inflation dynamics are reviewed. The warm inflation scenario is first described along with its results, predictions and comparison with the standard cold inflation scenario. The basics of thermal field theory required in the study of warm inflation are discussed. Quantum field theory real time calculations at finite temperature are then presented and the derivation of dissipation and stochastic fluctuations are shown from a general perspective. Specific results are given of dissipation coefficients for a variety of quantum field theory interaction structures relevant to warm inflation, in a form that can readily be used by model builders. Different particle physics models realising warm inflation are presented along with their observational predictions.

hep-ph↗

arXiv2008

Lack of initial conditions dependence of fluctuations in warm inflation

Warm inflation dynamics is fundamentally based on a system-reservoir configuration in which the dynamics is dictated by a fluctuation-dissipation relation. Recent work by Cerioni et. al. (arXiv:0804.0163) examined dissipative dynamics with no associated fluctuation component. Their results, which are heavily dependent on initial conditions, are at odds with results in the warm inflation literature, especially the spectral indices. The inconsistency of their formalism is outlined here and it is shown how this would lead to their erroneous conclusions. It is then shown how, following the correct dynamical equations of warm inflation, the results in the literature are correct.

astro-ph↗

arXiv2008

Local Approximations for Effective Scalar Field Equations of Motion

Fluctuation and dissipation dynamics is examined at all temperature ranges for the general case of a background time evolving scalar field coupled to heavy intermediate quantum fields which in turn are coupled to light quantum fields. The evolution of the background field induces particle production from the light fields through the action of the intermediate catalyzing heavy fields. Such field configurations are generically present in most particle physics models, including Grand Unified and Supersymmetry theories, with application of this mechanism possible in inflation, heavy ion collision and phase transition dynamics. The effective evolution equation for the background field is obtained and a fluctuation-dissipation theorem is derived for this system. The effective evolution in general is nonlocal in time. Appropriate conditions are found for when these time nonlocal effects can be approximated by local terms. Here careful distinction is made between a local expansion and the special case of a derivative expansion to all orders, which requires analytic behavior of the evolution equation in Fourier space.

hep-ph↗

arXiv2007

Superfluidity in Super-Yang-Mills Theory

The AdS/CFT correspondence suggests that there is a point in the phase diagram of strongly interacting gauge-theory matter where the viscosity approaches zero. This paper analyses the possibility that this point represents a superfluid and that the the system near this point in the phase diagram can be described by a Landau fluid. Superfluid vortices are constructed and the AdS analogue of vorticity quantisation is described. The production of vortices in the quark-gluon plasma during heavy ion collisions is discussed.

hep-th↗

arXiv2005

Boundary terms for supergravity and heterotic M-Theory

This paper considers eleven dimensional supergravity on a manifold with boundary and the theories related to heterotic $M$-theory, in which the matter is confined to the boundary. New low energy actions and boundary conditions on supergravity fields are derived. Previous problems with infinite constants in the action are overcome. The new boundary conditions are shown to be consistent with supersymmetry, and their role in the ten dimensional reduction and gaugino condensation is briefly discussed.

hep-th↗

arXiv2004

Radiation back reaction on moving branes

This paper addresses the radiation back reaction problem for cosmological branes. A general framework is provided in which results are given for the radiation reaction with massles and massive scalar fields with flat extra dimensions and massless conformal fields in anti-de Sitter extra dimensions. For massless scalar field radiation the back reaction terms in the equation of motion are non-analytic. The interpretation of the radiation reaction terms is discussed and the equations of motion solved in simple cases. Nucleosynthesis bounds on dark radiation give a lower bound on the string vacuum energy scale of $\sqrt{A_T} m_p$, where $A_T$ is the tensor perturbation amplitude in the cosmic microwave background.

hep-th↗

arXiv2004

Constraining Warm Inflation with the Cosmic Microwave Background

We discuss the spectrum of scalar density perturbations from warm inflation when the friction coefficient $Γ$ in the inflaton equation is dependent on the inflaton field. The spectral index of scalar fluctuations depends on a new slow-roll parameter constructed from $Γ$. A numerical integration of the perturbation equations is performed for a model of warm inflation and gives a good fit to the WMAP data for reasonable values of the model's parameters.

astro-ph↗

arXiv2004

One loop effective potential in heterotic M-theory

We have calculated the one loop effective potential of the vector multiplets arising from the compactification to five dimensions of heterotic M-theory on a Calabi-Yau manifold with h^{1,1}>1. We find that extensive cancellations between the fermionic and bosonic sectors of the theory cause the effective potential to vanish, with the exception of a higher order curvature term of the type which might arise from string corrections.

hep-th↗

arXiv2003

Scalar perturbation spectra from warm inflation

We present a numerical integration of the cosmological scalar perturbation equations in warm inflation. The initial conditions are provided by a discussion of the thermal fluctuations of an inflaton field and thermal radiation using a combination of thermal field theory and thermodynamics. The perturbation equations include the effects of a damping coefficient $Γ$ and a thermodynamic potential $V$. We give an analytic expression for the spectral index of scalar fluctuations in terms of a new slow-roll parameter constructed from $Γ$. A series of toy models, inspired by spontaneous symmetry breaking and a known form of the damping coefficient, lead to a spectrum with $n_s>1$ on large scales and $n_s<1$ on small scales.

astro-ph↗

arXiv2003

Boundary terms for eleven-dimensional supergravity and M-theory

A new action for eleven dimensional supergravity on a manifold with boundary is presented. The action is a possible low energy limit of $M$-theory. Previous problems with infinite constants in the action are overcome and a new set of boundary conditions relating the behaviour of the supergravity fields to matter fields are obtained. One effect of these boundary conditions is that matter fields generate gravitational torsion.

hep-th↗

arXiv2003

Bulk quantum effects for de Sitter branes in AdS(5)

We investigate some issues regarding quantum corrections for de Sitter branes in a bulk AdS(5) spacetime. The one-loop effective action for a Majorana spinor field is evaluated and compared with the scalar field result. We also evaluate the cocycle function for various boundary conditions, finding that the quantum corrections naturally induce higher order curvature terms in the original action and, in general, it is not possible to eliminate the cocycle function by renormalisation. In the one brane limit care must be taken on how one extracts physical results. The effective potential is found to be zero on the conformally related cylinder. However, using the actual metric, the contribution from the cocycle function is non-zero and must be included. Subtleties with any zero modes are also discussed.

hep-th↗

arXiv2003

Fermion Casimir energy for a de Sitter brane in AdS(5)

Based on some recent work of the authors, we focus on the relationship between the Casimir energy of a Majorana spinor field for a Euclidean Einstein universe $S^4\times R$ and for a Euclidean de Sitter brane ($S^4$) embedded in AdS(5). This is for a conformally coupled massless field. Interestingly, the one brane effective potential is zero and the results are equivalent, as for the scalar case, when evaluated on the conformally related cylinder. However, using the actual metric this equivalence no longer holds because a non-trivial contribution from the path integral measure (known as the cocycle function) is non-zero.

hep-th↗

arXiv2002

Effective action for bubble nucleation rates

We develop a method to calculate the prefactor in the expression for the bubble nucleation rate. A fermion with Yukawa coupling is considered where a step potential can be used as a good approximation in the thin wall limit. Corrections due to thicker walls are considered by perturbing about the thin wall case. We derive the thermal one loop effective action, calculating it numerically, and find that the prefactor in the nucleation rate can both suppress and enhance, for a given temperature, when the usual renormalisation conditions are applied to the effective potential.

hep-ph↗