arXiv subjects

Douglas Singleton

Publications and source records attributed to Douglas Singleton.

At least 73 records · Page 4Linked to original sources

arXiv2014

Stokes' theorem, gauge symmetry and the time-dependent Aharonov-Bohm effect

Stokes' theorem is investigated in the context of the time-dependent Aharonov-Bohm effect -- the two-slit quantum interference experiment with a time varying solenoid between the slits. The time varying solenoid produces an electric field which leads to an additional phase shift which is found to exactly cancel the time-dependent part of the usual magnetic Aharonov-Bohm phase shift. This electric field arises from a combination of a non-single valued scalar potential and/or a 3-vector potential. The gauge transformation which leads to the scalar and 3-vector potentials for the electric field is non-single valued. This feature is connected with the non-simply connected topology of the Aharonov-Bohm set-up. The non-single valued nature of the gauge transformation function has interesting consequences for the 4-dimensional Stokes' theorem for the time-dependent Aharonov-Bohm effect. An experimental test of these conclusions is proposed.

hep-th↗

arXiv2014

Reply to Comment on "Inflation with a graceful exit and entrance driven by Hawking radiation"

The comment [1, arXiv:1308.5573] raises two points in regard to our work [2, arXiv:1207.0230]. The first is that one cannot use the tunneling picture to obtain the temperature and particle production rate in the Friedman-Robertson-Walker (FRW) space-time. The second comment raised by [1] is that the Hawking-like radiation model for inflation presented in [2,3] is inconsistent with the observed scalar and tensor perturbation spectrum. We show that the first comment is beside the point -- we do not use the tunneling method in our works [2,3]. The second criticism in [1] comes from the author evaluating quantities at different times -- he evaluates the parameters of our model at the ``beginning'' of inflation and then compares this with the scalar and tensor perturbations evaluated at ``the horizon exit'' point.

gr-qc↗

arXiv2013

Field localization and Nambu Jona-Lasinio mass generation mechanism in an alternative 5-dimensional brane model

We consider a 5-dimensional brane world model with a single brane which is distinct from the well known Randall-Sundrum model. We discuss the similarities and differences between our brane model and the Randall-Sundrum brane model. In particular we focus on the localization of 5D fields with different spins -- spin 0, spin 1/2, spin 1 -- to the brane, and a self-consistent mass generation mechanism. We find that the brane model studied here has different (and in some cases superior) localization properties for fields/particles with different spins to the brane, as compared to the original 5-dimensional brane models. In addition this alternative 5D brane model exhibits a self generation mechanism which recalls the self-consistent approach of Nambu and Jona-Lasinio.

gr-qc↗

arXiv2013

Effect of circular Unruh radiation on bound nucleons and a possible answer to the Lithium 7 puzzle

In the shell model of nuclei, protons and neutrons move in a phenomenological nuclear potential much in the same manner as electrons move in Coulomb based potential in the shell model of atoms. As in the atomic case, the protons and neutrons of certain nuclear energy levels will have a non-zero orbital angular momentum (i.e. l =/= 0) and will therefore experience a centripetal potential and a centripetal acceleration. We advance the hypothesis, based on justification via the path integral formalism, that if one associates an Unruh temperature with this quantum centripetal acceleration then there is a potentially experimentally observable effect on certain nuclei -- the shifting of the naive expectations of the relative occupation of the ground and lowest lying energy levels. In particular we find that this effect should be most prominent in Li-7 nuclei. We speculate that this effect of the Unruh temperature might offer an answer to the Li-7 problem in Big Bang Nucleosynthesis.

nucl-th↗

arXiv2013

The covariant, time-dependent Aharonov-Bohm Effect

We discuss two possible covariant generalizations of the Aharonov-Bohm effect - one expression in terms of the space-time line integral of the four-vector potential and the other expression in terms of the space-time "area" integral of the electric and magnetic fields written in terms of the Faraday 2-form. These expressions allow one to calculate the Aharonov-Bohm effect for time-dependent situations. In particular, we use these expressions to study the case of an infinite solenoid with a time varying flux and find that the phase shift is zero due to a cancellation of the Aharonov-Bohm phase shift with a phase shift coming from the Lorentz force associated with the electric field, ${\bf E} = - \partial_t {\bf A}$, outside the solenoid. This result may already have been confirmed experimentally.

hep-th↗

arXiv2013

Dynamics of Dirac-Born-Infeld dark energy interacting with dark matter

We study the dynamics of Dirac-Born-Infeld (DBI) dark energy interacting with dark matter. The DBI dark energy model considered here has a scalar field with a nonstandard kinetic energy term, and has potential and brane tension that are power-law functions. The new feature considered here is an interaction between the DBI dark energy and dark matter through a phenomenological interaction between the DBI scalar field and the dark matter fluid. We analyze two different types of interactions between the DBI scalar field and the dark matter fluid. In particular we study the phase-space diagrams of and look for critical points of the phase space that are both stable and lead to accelerated, late-time expansion. In general we find that the interaction between the two dark components does not appear to give rise to late-time accelerated expansion. However, the interaction can make the critical points in the phase space of the system stable. Whether such stabilization occurs or not depends on the form of the interaction between the two dark components.

gr-qc↗

arXiv2012

Inflation with a graceful exit and entrance driven by Hawking radiation

We present a model for cosmological inflation which has a natural "turn on" and a natural "turn off" mechanism. In our model inflation is driven by the Hawking-like radiation that occurs in Friedman-Robertson-Walker (FRW) space-time. This Hawking-like radiation results in an effective negative pressure "fluid" which leads to a rapid period of expansion in the very early Universe. As the Universe expands the FRW Hawking temperature decreases and the inflationary expansion turns off and makes a natural transition to the power law expansion of a radiation dominated universe. The "turn on" mechanism is more speculative, but is based on the common hypothesis that in a quantum theory of gravity at very high temperatures/high densities Hawking radiation will stop. Applying this speculation to the very early Universe implies that the Hawking-like radiation of the FRW space-time will be turned off and therefore the inflation driven by this radiation will turn off.

gr-qc↗

arXiv2012

A two measure model of dark energy and dark matter

In this work we construct a unified model of dark energy and dark matter. This is done with the following three elements: a gravitating scalar field, phi with a non-conventional kinetic term, as in the string theory tachyon; an arbitrary potential, V(phi); two measures -- a metric measure (sqrt{-g}) and a non-metric measure (Phi). The model has two interesting features: (i) For potentials which are unstable and would give rise to tachyonic scalar field, this model can stabilize the scalar field. (ii) The form of the dark energy and dark matter that results from this model is fairly insensitive to the exact form of the scalar field potential.

gr-qc↗

arXiv2012

Hawking Radiation as a Mechanism for Inflation

The Friedman-Robertson-Walker (FRW) space-time exhibits particle creation similar to Hawking radiation of a black hole. In this essay we show that this FRW Hawking radiation leads to an effective negative pressure fluid which can drive an inflationary period of exponential expansion in the early Universe. Since the Hawking temperature of the FRW space-time decreases as the Universe expands this mechanism naturally turns off and the inflationary stage transitions to a power law expansion associated with an ordinary radiation dominated Universe.

gr-qc↗

arXiv2012

A test of the circular Unruh effect using atomic electrons

We propose a test for the circular Unruh effect using certain atoms - fluorine and oxygen. For these atoms the centripetal acceleration of the outer shell electrons implies an effective Unruh temperature in the range 1000 - 2000 K. This range of Unruh temperatures is large enough to shift the expected occupancy of the lowest energy level and nearby energy levels. In effect the Unruh temperature changes the expected pure ground state, with all the electrons in the lowest energy level, to a mixed state with some larger than expected occupancy of states near to the lowest energy level. Examining these atoms at low background temperatures and finding a larger than expected number of electrons in low lying excited levels, beyond what is expected due to the background thermal excitation, would provide experimental evidence for the Unruh effect.

hep-th↗

arXiv2012

Hawking radiation, chirality, and the principle of effective theory of gravity

In this paper we combine the chirality of field theories in near horizon regions with the principle of effective theory of gravity to define a new energy-momentum tensor for the theory. This new energy-momentum tensor has the correct radiation flux to account for Hawking radiation for space-times with horizons. This method is connected to the chiral anomaly cancellation method, but it works for space-times for which the chiral anomaly cancellation method fails. In particular the method presented here works for the non-asymptotically flat de Sitter space-time and its associated Hawking-Gibbons radiation, as well as Rindler space-time and its associated Unruh radiation. This indicates that it is the chiral nature of the field theory in the near horizon regions which is of primary importance rather than the chiral anomaly.

gr-qc↗

arXiv2012

Exercices de style: a homotopy theory for set theory, I

We construct a model category (in the sense of Quillen) for set theory, starting from two arbitrary, but natural, conventions. It is the simplest category satisfying our conventions and modelling the notions of finiteness, countability and infinite equi-cardinality. In a subsequent paper \cite{GaHa1} we give a homotopy theoretic dictionary of set theoretic concepts, most notably Shelah's covering number $\cov(λ, \aleph_1,\aleph_1,2)$, recovered from this model category. We argue that from the homotopy theoretic point of view our construction is essentially automatic following basic existing methods, and so is (almost all) the verification that the construction works.

math.LO↗

arXiv2012

Relativistic polytropic spheres embedded in a chameleon scalar field

In this paper we investigate gravitationally bound, spherically symmetric equilibrium configurations consisting of ordinary (polytropic) matter nonminimally coupled to an external chameleon scalar field. We show that this system has static, regular, asymptotically flat general relativistic solutions. The properties of these spherical configurations, such as total mass, distribution of matter, and size, depend strongly on the surrounding scalar field. The mass is found in terms of the parameter $σ$, which is proportional to the central mass density of the ordinary matter. We perform a stability analysis of these spherical solutions and find an upper bound for $σ$ where dynamical instability occurs.

astro-ph.SR↗

arXiv2011

Entropic derivation of F=ma for circular motion

We examine the entropic picture of Newton's second law for the case of circular motion. It is shown that one must make modifications to the derivation of F=ma due to a change in the effective Unruh temperature for circular motion. These modifications present a challenge to the entropic derivation of Newton's second law, but also open up the possibility to experimentally test and constrain this model for large centripetal accelerations.

gr-qc↗

arXiv2011

Electromagnetism with Magnetic Charge and Two Photons

The Dirac approach to include magnetic charge in Maxwell's equations places the magnetic charge at the end of a string on which the the fields of the theory develop a singularity. In this paper an alternative formulation of classical electromagnetism with magnetic and electric charge is given by introducing a second pseudo four-vector potential, C_mu, in addition to the usual four- vector potential, A_mu. This avoids the use of singular, non-local variables (i.e. Dirac strings) in electrodynamics with magnetic charge, and it makes the treatment of electric and magentic charge more symmetric, since both charges are now gauge charges.

hep-th↗

arXiv2011

Insights and possible resolution to the information loss paradox via the tunneling picture

This paper investigates the information loss paradox in the WKB/tunneling picture of Hawking radiation. In the tunneling picture one can obtain the tunneling amplitude to all orders in $\hbar$. However all terms beyond the lowest, semi-classical term involve unknown constants. Despite this we find that one can still arrive at interesting restrictions on Hawking radiation to all orders in $\hbar$: (i) Taking into account only quantum corrections the spectrum remains thermal to all orders. Thus quantum corrections by themselves will not resolve the information loss paradox. (ii) The first quantum correction give a temperature for the radiation which goes to zero as the mass of the black hole goes to zero. Including higher order corrections changes this nice result of the first order corrections. (iii) Finally we show that by taking both quantum corrections and back reaction into account it is possible under specific conditions to solve the information paradox by having the black hole evaporate completely with the information carried away by the correlations of the outgoing radiation.

gr-qc↗

arXiv2010

On the stability of spherically symmetric and wormhole solutions supported by the sine-Gordon ghost scalar field

In this paper we investigate wormhole and spherically symmetric solutions in 4D gravity plus a matter source consisting of a ghost scalar field with a sine-Gordon potential. For the wormhole solutions we also include the possibility of electric and/or magnetic charges. For both types of solutions we perform a linear stability analysis and show that the wormhole solutions are stable and that when one turns on the electric and/or magnetic field the solution remains stable. The linear stability analysis of the spherically symmetric solutions indicates that they can be stable or unstable depending on one of the parameters of the system. This result for the spherically symmetric solution is nontrivial since a previous investigation of 4D gravity plus a ghost scalar field with a $λϕ^4$ interaction found only unstable spherically symmetric solutions. Both the wormhole and spherically symmetric solutions presented here asymptotically go to anti-de-Sitter space-time.

gr-qc↗

arXiv2010

Energy spectrum of simply constant chromoelectric flux tubes

In this article we obtain the energy spectrum of colored, spinor particles in chromoelectric flux tubes. The chromoelectric field of the flux tubes considered here comes from {\em simply} constant gauge potentials rather than from covariantly constant gauge potential, as is usually the case. The energy spectrum of the simply constant flux tubes is different than that of the covariantly constant flux tubes. The spectrum is discrete due to the walls of the tube and with a plus/minus constant shift depending on the magnitude of the constant chromoelectric background. This goes against the classical intuition where one would expect a charged particle in a uniform "electric" field to accelerate with ever increasing velocity/energy i.e. there would be no constant energy eigenvalue.

hep-th↗