arXiv subjects

Alan Chodos

Publications and source records attributed to Alan Chodos.

29 records · Page 2Linked to original sources

arXiv1999

Cosmological Neutrino Condensates

We investigate the possibility that neutrinos form superfluid-type condensates in background cosmological densities. Such condensates could give rise to small neutrino masses and splittings, as well as an important contribution, perhaps, to the cosmological constant. We discuss various channels in the context of the standard model. Many of these do not support a condensate, but some mixed-flavor channels do. We also suggest a new interaction, acting only among neutrinos, that could induce a neutrino Majorana mass of order 1 eV.

hep-ph↗

arXiv1998

Cooper pairing at large N in a 2-dimensional model

We study a 2-dimensional model of Fermi fields that is closely related to the Gross-Neveu model, and show that to leading order in 1/N a condensate forms. This effect is independent of the chemical potential, a peculiarity that we expect to be specific to 2 dimensions. We also expect the condensate to be unstable against corrections at higher orders in 1/N. We compute the Green's functions associated with the composite psi-psi, and show that the Fermion acquires a Majorana mass proportional to the gap, and that a massless Goldstone pole appears.

hep-ph↗

arXiv1998

Modelling Sonoluminescence

In single-bubble sonoluminescence, a bubble trapped by a sound wave in a flask of liquid is forced to expand and contract; exactly once per cycle, the bubble emits a very sharp ($< 50 ps$) pulse of visible light. This is a robust phenomenon observable to the naked eye, yet the mechanism whereby the light is produced is not well understood. One model that has been proposed is that the light is "vacuum radiation" generated by the coupling of the electromagnetic fields to the surface of the bubble. In this paper, we simulate vacuum radiation by solving Maxwell's equations with an additional term that couples the field to the bubble's motion. We show that, in the static case originally considered by Casimir, we reproduce Casimir's result. In a simple purely time-dependent example, we find that an instability occurs and the pulse of radiation grows exponentially. In the more realistic case of spherically-symmetric bubble motion, we again find exponential growth in the context of a small-radius approximation.

hep-ph↗

arXiv1997

The TBA, the Gross-Neveu Model, and Polyacetylene

We summarize recent work showing how the Thermodynamic Bethe Ansatz may be used to study the finite-density first-order phase transition in the Gross-Neveu model. The application to trans-polyacetylene is discussed, and the significance of the results is addressed.

hep-th↗

arXiv1997

The Gross-Neveu Model with Chemical Potential; An Effective Theory for Solitonic-Metallic Phase Transition in Polyacetylene?

The Gross-Neveu model with chemical potential is investigated as a low-energy effective theory of polyacetylene. In particular, we focus on the abrupt change in the features of electric conductivity such as sharp rise in the Pauli paramagnetism at dopant concentration of about 6%. We will try to explain it by the finite density phase transition in the Gross-Neveu model. The thermodynamic Bethe ansatz is combined with the large-N expansion to construct thermodynamics of the Gross-Neveu model. A first-order phase transition is found in leading order in the 1/N expansion and it appears to be stable against the 1/N correction. The next to leading order correction to the critical dopant concentration is explicitly calculated.

hep-th↗

arXiv1996

The Thermodynamic Bethe Ansatz and the 1/N Correction to the Density Phase Transition in the Gross-Neveu Model

We compute the $1/N$ correction to the location of the previously found first-order phase transition in the Gross-Neveu model at a chemical potential $μ= μ_c = {1 \over \sqrt{2}} m$, where $m$ is the fermion mass. We employ an expression for the free energy $f(μ)$ given by the thermodynamic Bethe ansatz under the approximation that the fundamental fermions dominate the ground state, and combine it with the effective potential evaluated at zero chemical potential. Our result is $μ_c = {m \over \sqrt{2}} [1 - {0.47 \over N}]$.

hep-th↗

arXiv1996

Zeta function regularization in de Sitter space: the Minkowski limit

We study an integral representation for the zeta function of the one-loop effective potential for a minimally coupled massive scalar field in D-dimensional de Sitter spacetime. By deforming the contour of integration we present it in a form suitable for letting the de Sitter radius tend to infinity, and we demonstrate explicitly for the case D=2 that the quantities $ζ( 0 )$ and $ζ'( 0 )$ have the appropriate Minkowski limits.

hep-th↗

arXiv1996

Sonoluminescence and the Heimlich Effect

The phenomenon of sonoluminescence (SL), originally observed some sixty years ago, has recently become the focus of renewed interest, particularly with the discovery that one can trap a single bubble and induce it to exhibit SL stably over a large number of acoustical cycles. In this work we shall adopt a version of the provocative suggestion put forward by Schwinger: the mechanism responsible for the radiation in SL is a dynamic version of the Casimir effect. It has been known since Casimir's original work in 1948 that the zero-point energy of quantum fields can be modified by the presence of boundaries, and that these modifications generate observable effects. For example, in Casimir's original work, the quantum fluctuations of the electromagnetic field in the presence of a pair of uncharged, parallel, perfectly conducting plates were shown to give rise to an attractive force between the plates.

hep-ph↗

arXiv1995

Symmetry Breaking in the Static Coordinate System of de Sitter Spacetime

We study symmetry breaking in the static coordinate-system of de Sitter space. This is done with the help of the functional-Schrödinger approach used in previous calculations by Ratra [1]. We consider a massless, minimally coupled scalar field as the parameter of a continuous symmetry (the angular component of an O(2) symmetry). Then we study the correlation function of the massless scalar field, to derive the correlation function of the original field, which finally shows the restoration of the continuous symmetry.

hep-th↗

arXiv1994

Proper-time methods in the presence of non-constant background fields

A formalism is developed to enable the construction of the effective action and related quantities in QED for the case of time-varying background electric fields. Some examples are studied and evidence is sought for a possible transition to a phase in which chiral symmetry is spontaneously broken. YCTP-P14-94

hep-ph↗

arXiv1994

Nuclear Null Tests for Spacelike Neutrinos

Recently, a type of null experiment for spacelike neutrinos has been proposed. We examine in detail a class of null tests involving nuclear beta decay or capture in atoms and ions. The most promising candidate systems are identified.

hep-ph↗