100 research outputs found
Loop quantum gravity induced modifications to particle dynamics
The construction of effective Hamiltonians arising from Loop Quantum Gravity
and incorporating Planck scale corrections to the dynamics of photons and spin
1/2 particles is summarized. The imposition of strict bounds upon some
parameters of the model using already existing experimental data is also
reviewed.Comment: 9 pages, 0 figures, talk presented at the X Mexican School of
Particles and Fields, latex, aipproc style 6x
Flat space modified particle dynamics induced by Loop Quantum Gravity
Starting from an heuristic approach to the semiclassical limit in loop
quantum gravity, the construction of effective Hamiltonians describing Planck
length corrections to the propagation of photons and spin 1/2 fermions, leading
to modified energy-momentum relations, is summarized. Assuming the existence of
a privileged reference frame, we also review the determination of stringent
bounds upon the parameters labelling such corrections, based upon already
existing experimental data, which are found to be from five to nine orders of
magnitude below the expected values.Comment: 10 pages, no figures, ws-procs 975x65.cls, extended version of the
talk given at the Tenth Marcel Grossmann Meeting, Rio de Janeiro, July 20-26,
200
Loop Quantum Gravity induced corrections to fermion dynamics in flat space
A summary of recent work related to the calculation of loop quantum gravity
induced corrections to standard particle (photons and spin 1/2 fermions)
dynamics in flat space is presented. Stringent bounds upon the parameters
characterizing the corrections in the fermionic sector, arising from already
known clock-comparison experiments, are reviewed.Comment: 6 pages, no figures, ws-procs9x6.tex, Talk presented at the Third
International Symposium on Quantum Theory and Symmetries, U. of Cincinnati,
September 10-14, 200
Slowly rotating Kerr black hole as a solution of Einstein-Cartan gravity extended by a Chern-Simons term
We consider the nondynamical Chern-Simons (CS) modification to General
Relativity (GR) in the framework of the Einstein-Cartan formulation, as
providing a way to incorporate a slowly rotating Kerr black hole in the space
of solutions. Our proposal lies on considering the CS term as a source of
torsion and on an iterative procedure to look for vacuum solutions of the
system, by expanding the tetrad, the connection and the embedding parameter, in
powers of a dimensionless small parameter which codifies the CS
coupling. Starting from a torsionless zeroth-order vacuum solution we derive
the second-order differential equation for the corrections
to the metric, for an arbitrary embedding parameter. Furthermore we can show
that the slowly rotating Kerr metric is an solution of the
system either in the canonical or the axial embeddings.Comment: "Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 2010
An extended solution space for Chern-Simons gravity: the slowly rotating Kerr black hole
In the Einstein-Cartan formulation, an iterative procedure to find solutions
in non-dynamical Chern-Simons (CS) gravity in vacuum is proposed. The
iterations, in powers of a small parameter which codifies the CS
coupling, start from an arbitrary torsionless solution of Einstein equations.
With Schwarzschild as the zeroth-order choice, we derive a second-order
differential equation for the corrections to the metric,
for an arbitrary zeroth-order embedding parameter. In particular, the slowly
rotating Kerr metric is an solution in either the
canonical or the axial embeddings.Comment: 5 pages, PRD accepte
Radiation from a dipole perpendicular to the interface between two planar semi-infinite magnetoelectric media
We consider two semi-infinite magnetoelectric media with constant dielectric
permittivity separated by a planar interface, whose electromagnetic response is
described by non-dynamical axion electrodynamics and investigate the radiation
of a point-like electric dipole located perpendicularly to the interface. We
start from the exact Green's function for the electromagnetic potential, whose
far-field approximation is obtained using a modified steepest descent
approximation. This procedure yields the standard spherical waves as well as
axially symmetric cylindrical superficial waves, which nevertheless are
restricted to a region very close to the interface. We compute the angular
distribution of the radiation and the total radiated power finding different
interference patterns, depending on the relative position dipole-observer, and
polarization mixing effects which are all absent in the standard dipole
radiation. They are a manifestation of the magnetoelectric effect induced by
axion electrodynamics. We illustrate our findings with some numerical
estimations employing realistic media as well as some hypothetical choices in
order to illuminate the effects of the magnetoelectric coupling which is
usually very small.Comment: 29 pages, 18 figures, new references added, results unchanged,
improved explanations, matches accepted version in Rev. Mex. Fi
- …