45 research outputs found
Gravity from Lorentz Symmetry Violation
In general relativity, the masslessness of gravitons can be traced to
symmetry under diffeomorphisms. Here we consider another possibility, whereby
the masslessness arises from spontaneous violation of Lorentz symmetry.Comment: Presented at the XXVIII Spanish Relativity Meeting, E.R.E. 2005, "A
Century of Relativity Physics", Oviedo, Spain, September 6-10, 200
Ghost Sector of Vacuum String Field Theory and the Projection Equation
We study the ghost sector of vacuum string field theory where the BRST
operator Q is given by the midpoint insertion proposed by Gaiotto, Rastelli,
Sen and Zwiebach. We introduce a convenient basis of half-string modes in terms
of which Q takes a particularly simple form. We show that there exists a field
redefinition which reduces the ghost sector field equation to a pure projection
equation for string fields satisfying the constraint that the ghost number is
equally divided over the left- and right halves of the string. When this
constraint is imposed, vacuum string field theory can be reformulated as a
cubic matrix model. Ghost sector solutions can be constructed from
projection operators on half-string Hilbert space just as in the matter sector.
We construct the ghost sector equivalent of various well-known matter sector
projectors such as the sliver, butterfly and nothing states.Comment: 25 pages, no figures. Typos corrected, published versio
The Boltzmann equation and equilibrium thermodynamics in Lorentz-violating theories
In this work we adapt the foundations of relativistic kinetic theory and the
Boltzmann equation to particles with Lorentz-violating dispersion relations.
The latter are taken to be those associated to two commonly considered sets of
coefficients in the minimal Standard-Model Extension. We treat both the cases
of classical (Maxwell-Boltzmann) and quantum (Fermi-Dirac and Bose-Einstein)
statistics. It is shown that with the appropriate definition of the entropy
current, Boltzmann's H-theorem continues to hold. We derive the equilibrium
solutions and then identify the Lorentz-violating effects for various
thermodynamic variables, as well as for Bose-Einstein condensation. Finally, a
scenario with non-elastic collisions between multiple species of particles
corresponding to chemical or nuclear reactions is considered
Lorentz and CPT violation
During the past two decades there has been a growing interest in the possibility that Lorentz and/or CPT might not be exact symmetries of Nature. In this short review, we present the current state of affairs, addressing both theoretical and experimental/observational issues. We pay particular attention to the role that has been played by the so-called Standard Model Extensio
Lorentz-violating photons with a mass term
Perturbative calculations in quantum field theory often require the
regularization of infrared divergences. In quantum electrodynamics, such a
regularization can for example be accomplished by a photon mass introduced via
the Stueckelberg method. The present work extends this method to the QED limit
of the Lorentz- and CPT-violating Standard-Model Extension.Comment: 4 pages, presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 201
Cherenkov radiation with massive, CPT-violating photons
The source of CPT violation in the photon sector of the Standard Model Extension arises from a Chern-Simons-like contribution that involves a coupling to a fixed background vector field k(AF)(mu). These Lorentz- and CPT-violating photons have well-known theoretical issues that arise from missing states at low momenta when k(AF)(mu) is timelike. In order to make the theory consistent, a tiny mass for the photon can be introduced, well below current experimental bounds. The implementation of canonical quantization can then be implemented as in the CPT-preserving case by using the Stuckelberg mechanism. We explicitly construct a covariant basis of properly normalized polarization vectors at fixed three-momentum satisfying the momentum space field equations, in terms of which the vector field can be expanded. As an application of the theory, we calculate the Cherenkov radiation rate for the case of purely timelike k(AF)(mu) and find a radiation rate at high energies that has a contribution that does not depend on the mass used to regulate the photons
Gupta-Bleuler Photon Quantization in the SME
Photon quantization is implemented in the standard model extension (SME)
using the Gupta-Bleuler method and BRST concepts. The quantization prescription
applies to both the birefringent and non-birefringent CPT-even couplings. A
curious incompatibility is found between the presence of the Lorentz-violating
terms and the existence of a nontrivial conjugate momentum yielding
problems with covariant quantization procedure. Introduction of a mass
regulator term can avoid the vanishing of and allows for the
implementation of a covariant quantization procedure. Field-theoretic
calculations involving the SME photons can then be performed using the mass
regulator, similar to the conventional procedure used in electrodynamics for
infrared-divergence regulation.Comment: 13 page