1,556 research outputs found
Maxwell-Chern-Simons theory for curved spacetime backgrounds
We consider a modified version of four-dimensional electrodynamics, which has
a photonic Chern-Simons-like term with spacelike background vector in the
action. Light propagation in curved spacetime backgrounds is discussed using
the geometrical-optics approximation. The corresponding light path is modified,
which allows for new effects. In a Schwarzschild background, for example, there
now exist stable bounded orbits of light rays and the two polarization modes of
light rays in unbounded orbits can have different gravitational redshifts. An
Erratum with important corrections has been published, which appears as
Appendix E in this arXiv version.Comment: 28 pages with elsart, v6: published version of paper and Erratu
Models for low-energy Lorentz violation in the photon sector: Addendum to 'Consistency of isotropic modified Maxwell theory'
In a previous article [arXiv:1011.4258], we established the consistency of
isotropic modified Maxwell theory for a finite range of the Lorentz-violating
parameter \tilde{kappa}_{tr}, which includes both positive and negative values
of \tilde{kappa}_{tr}. As an aside, we mentioned the existence of a physical
model which, for low-energy photons, gives rise to isotropic modified Maxwell
theory with a positive parameter \tilde{kappa}_{tr} (corresponding to a "slow"
photon). Here, we present a related model which gives rise to isotropic
modified Maxwell theory with a negative parameter \tilde{kappa}_{tr}
(corresponding to a "fast" photon). Both models have an identical particle
content, photon and Dirac particles, but differ in the type of spacetime
manifold considered.Comment: 6 pages, v4: published versio
A sphaleron for the non-Abelian anomaly
A self-consistent Ansatz for a new sphaleron of SU(3) Yang-Mills-Higgs theory
is presented. With a single triplet of Weyl fermions added, there exists, most
likely, one pair of fermion zero modes, which is known to give rise to the
non-Abelian (Bardeen) anomaly as a Berry phase. The corresponding SU(3) gauge
field configuration could take part in the nonperturbative dynamics of Quantum
Chromodynamics.Comment: LaTeX with elsart.cls, 26 pages, v4: published versio
Construction of a New Electroweak Sphaleron
We present a self-consistent ansatz for a new sphaleron in the electroweak
standard model. The resulting field equations are solved numerically. This
sphaleron sets the height of the energy barrier for the global SU(2) anomaly.Comment: 13 pages, Latex, NIKHEF-H/93-09 (June 1993), postscript file
including figures 1 and 2 available by anonymous ftp, figure 3 available by
fax (send request to [email protected]
Fundamental time asymmetry from nontrivial space topology
It is argued that a fundamental time asymmetry could arise from the global
structure of the space manifold. The proposed mechanism relies on the CPT
anomaly of certain chiral gauge theories defined over a multiply connected
space manifold. The resulting time asymmetry (microscopic arrow of time) is
illustrated by a simple thought experiment. The effect could, in principle,
play a role in determining the initial conditions of the big bang.Comment: 9 pages, REVTeX, v5: version publishe
A New Perspective on Electroweak Strings
The vortex solution (Z-string) of the electroweak interactions can be
interpreted as the 2-dimensional sphaleron at the top of a non-contractible
sphere. The same holds for another type of solution, the W-string.Comment: 13 pages, Latex, NIKHEF-H/94-02 (February 2, 1994), 1 figure
available by fax or mail (send request to [email protected]
QCD-scale modified-gravity universe
A possible gluon-condensate-induced modified-gravity model with f(R) \propto
|R|^{1/2} has been suggested previously. Here, a simplified version is
presented using the constant flat-spacetime equilibrium value of the QCD gluon
condensate and a single pressureless matter component (cold dark matter, CDM).
The resulting dynamical equations of a spatially-flat and homogeneous
Robertson-Walker universe are solved numerically. This simple empirical model
allows, in fact, for a careful treatment of the boundary conditions and does
not require a further scaling analysis as the original model did. Reliable
predictions are obtained for several observable quantities of the homogeneous
model universe. In addition, the estimator E_{G}, proposed by Zhang et al. to
search for deviations from standard Einstein gravity, is calculated for linear
sub-horizon matter-density perturbations. The QCD-scale modified-gravity
prediction for E_{G}(z) differs from that of the LambdaCDM model by about \pm
10 % depending on the redshift z.Comment: 24 pages; v7: published versio
Fermion zero-modes of a new constrained instanton in Yang-Mills-Higgs theory
Self-consistent Ansaetze are presented for the left- and right-handed
isodoublet fermion zero-modes of the constrained instanton Istar in the vacuum
sector of euclidean SU(2) Yang-Mills-Higgs theory. These left- and right-handed
fermion wave functions do not coincide and, most likely, have maxima at
different positions. This may be important for the fermion zero-mode
contribution to the euclidean 4-point Green's function in chiral
Yang-Mills-Higgs theory and the high-energy behaviour of fermion-fermion
scattering processes.Comment: Version to be published, changes in last two sections. 20 pages LaTeX
Final version
The imaginary time Path Integral and non-time-reversal-invariant- saddle points of the Euclidean Action
We discuss new bounce-like (but non-time-reversal-invariant-) solutions to
Euclidean equations of motion, which we dub boomerons. In the Euclidean path
integral approach to quantum theories, boomerons make an imaginary contribution
to the vacuum energy. The fake vacuum instabilty can be removed by cancelling
boomeron contributions against contributions from time reversed boomerons
(anti-boomerons). The cancellation rests on a sign choice whose significance is
not completely understood in the path integral method.Comment: 19 pages, LaTex, 5 epsf figures. A new example from quantum mechanics
is included. The role of internal symmetries is discussed. To be published in
Nucl. Phys.
CPT anomaly: a rigorous result in four dimensions
The existence of a CPT anomaly is established for a particular
four-dimensional Abelian lattice gauge theory with Ginsparg-Wilson fermions.Comment: LaTeX with elsart.cls, 24 pages, v3: published versio
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