1,759 research outputs found
Violating Electrodynamics and Chern-Simons Modified Gravity
The electrodynamics with a Chern-Simons term
violates Lorentz and symmetries
with a non-vanishing . For a fixed vector , in this paper we
point out that the energy-momentum tensor of this theory coupled to the gravity
minimally is symmetric but not divergence free, which consequently makes the
gravitational field equation inconsistent. To preserve the consistency, we
introduce a Chern-Simons term in the gravity sector with the coefficient
determined by the Lorentz and violating term in the electromagnetic
field. Further we study the phenomenologies of the model on the cosmic
microwave background radiation and the relic gravitational waves.Comment: 11 pages, 1 figure, the version to appear in Physics Letters
Generation of higher derivatives operators and electromagnetic wave propagation in a Lorentz-violation scenario
We study the perturbative generation of higher-derivative operators as
corrections to the photon effective action, which are originated from a Lorentz
violation background. Such corrections are obtained, at one-loop order, through
the proper-time method, using the zeta function regularization. We focus over
the lowest order corrections and investigate their influence in the propagation
of electromagnetic waves through the vacuum, in the presence of a strong,
constant magnetic field. This is a setting of experimental relevance, since it
bases active efforts to measure non linear electromagnetic effects. After
surprising cancellations of Lorentz violating corrections to the Maxwell's
equation, we show that no effects of the kind of Lorentz violation we consider
can be detected in such a context.Comment: v2: 13 pages, no figures, section IV considerably rewritten, main
results unchanged and are now obtained in a simpler way. To appear in PL
Anisotropic cubic curvature couplings
To complement recent work on tests of spacetime symmetry in gravity, cubic
curvature couplings are studied using an effective field theory description of
spacetime-symmetry breaking. The associated mass dimension 8 coefficients for
Lorentz violation studied do not result in any linearized gravity modifications
and instead are revealed in the first nonlinear terms in an expansion of
spacetime around a flat background. We consider effects on gravitational
radiation through the energy loss of a binary system and we study two-body
orbital perturbations using the post-Newtonian metric. Some effects depend on
the internal structure of the source and test bodies, thereby breaking the Weak
Equivalence Principle for self-gravitating bodies. These coefficients can be
measured in solar-system tests, while binary-pulsar systems and short-range
gravity tests are particularly sensitive.Comment: 11 page
Gravitational waves effects in a Lorentz-violating scenario
This paper focuses on how the production and polarization of gravitational
waves are affected by spontaneous Lorentz symmetry breaking, which is driven by
a self-interacting vector field. Specifically, we examine the impact of a
smooth quadratic potential and a non-minimal coupling, discussing the
constraints and causality features of the linearized Einstein equation. To
analyze the polarization states of a plane wave, we consider a fixed vacuum
expectation value (VEV) of the vector field. Remarkably, we verify that a
space-like background vector field modifies the polarization plane and
introduces a longitudinal degree of freedom. In order to investigate the
Lorentz violation effect on the quadrupole formula, we use the modified Green
function. Finally, we show that the space-like component of the background
field leads to a third-order time derivative of the quadrupole moment, and the
bounds for the Lorentz-breaking coefficients are estimated as well.Comment: 19 pages and 1 figur
Velocity-dependent inverse cubic force and solar system gravity tests
Higher mass dimension terms in an effective field theory framework for tests
of spacetime symmetries are studied. Using a post-Newtonian expansion method,
we derive the spacetime metric and the equations of motion for a binary system.
This reveals an inverse cubic force correction to General Relativity that
depends on the velocity of the bodies in the system. The results are studied in
the context of laboratory and space-based tests including the effects on
solar-system ephemeris, laser ranging observations, and gravimeter tests. This
work reveals the coefficient combinations for mass dimension 5 operators
controlling CPT violation for gravity that can be measured using analysis from
these tests. Other tests including light propagation can be used to probe these
coefficients. Sensitivity estimates are provided and the results are contrasted
with the minimal mass dimension 4 terms in the gravity sector.Comment: 10 pages, matches published versio
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