12 research outputs found
Ultraviolet modified photons and anisotropies in the cosmic microwave background radiation
We discuss a minimal canonical modification of electrodynamics in order to
account for ultraviolet Lorentz violating effects. This modification creates a
birefringence that rotates the polarization planes from different directions.
Such effects might be detectable in the anisotropic polarization of the Cosmic
Microwave Background radiation.Comment: RevTeX, 4p
String solutions in Chern-Simons-Higgs model coupled to an axion
We study a d=2+1 dimensional Chern-Simons gauge theory coupled to a Higgs
scalar and an axion field, finding the form of the potential that allows the
existence of selfdual equations and the corresponding Bogomolny bound for the
energy of static configurations. We show that the same conditions allow for the
N=2 supersymmetric extension of the model, reobtaining the BPS equations from
the supersymmetry requirement. Explicit electrically charged vortex-like
solutions to these equations are presented.Comment: 11 pages, 3 figure
Microcausality and quantization of the fermionic Myers-Pospelov model
We study the fermionic sector of the Myers and Pospelov theory with a general
background . The spacelike case without temporal component is well defined
and no new ingredients came about, apart from the explicit Lorentz invariance
violation. The lightlike case is ill defined and physically discarded. However,
the other case where a nonvanishing temporal component of the background is
present, the theory is physically consistent. We show that new modes appear as
a consequence of higher time derivatives. We quantize the timelike theory and
calculate the microcausality violation which turns out to occur near the light
cone.Comment: 9 pages and 3 figures, new version accepted in EPJC, Volume 72, Issue
9, includes lee-wick review, microcausalit
Finite Temperature Induced Fermion Number In The Nonlinear sigma Model In (2+1) Dimensions
We compute the finite temperature induced fermion number for fermions coupled
to a static nonlinear sigma model background in (2+1) dimensions, in the
derivative expansion limit. While the zero temperature induced fermion number
is well known to be topological (it is the winding number of the background),
at finite temperature there is a temperature dependent correction that is
nontopological -- this finite T correction is sensitive to the detailed shape
of the background. At low temperature we resum the derivative expansion to all
orders, and we consider explicit forms of the background as a CP^1 instanton or
as a baby skyrmion.Comment: 10 pp, revtex
Astrophysical Origins of Ultrahigh Energy Cosmic Rays
In the first part of this review we discuss the basic observational features
at the end of the cosmic ray energy spectrum. We also present there the main
characteristics of each of the experiments involved in the detection of these
particles. We then briefly discuss the status of the chemical composition and
the distribution of arrival directions of cosmic rays. After that, we examine
the energy losses during propagation, introducing the Greisen-Zaptsepin-Kuzmin
(GZK) cutoff, and discuss the level of confidence with which each experiment
have detected particles beyond the GZK energy limit. In the second part of the
review, we discuss astrophysical environments able to accelerate particles up
to such high energies, including active galactic nuclei, large scale galactic
wind termination shocks, relativistic jets and hot-spots of Fanaroff-Riley
radiogalaxies, pulsars, magnetars, quasar remnants, starbursts, colliding
galaxies, and gamma ray burst fireballs. In the third part of the review we
provide a brief summary of scenarios which try to explain the super-GZK events
with the help of new physics beyond the standard model. In the last section, we
give an overview on neutrino telescopes and existing limits on the energy
spectrum and discuss some of the prospects for a new (multi-particle)
astronomy. Finally, we outline how extraterrestrial neutrino fluxes can be used
to probe new physics beyond the electroweak scale.Comment: Higher resolution version of Fig. 7 is available at
http://www.angelfire.com/id/dtorres/down3.html. Solicited review article
prepared for Reports on Progress in Physics, final versio