34 research outputs found
Photon propagation in a cold axion condensate
We discuss some striking properties of photons propagating in a cold axion
condensate oscillating coherently in time with a frequency . Three
effects are discussed in this contribution: (a) due to the time dependence of
the background, photons moving in the cold axion background have no definite
energies and some momenta are not accessible to them. (b) we investigate the
combined influence of a magnetic field and the cold axion background and
propose a possible interferometric experiment to detect the latter. (c) if the
axion condensate has a space dependence, the photon refraction index is
modified in the medium, possibly leading to total reflection at the interface
with the ordinary vacuum.Comment: 6 pages, 4 figures, to appear in Proceedings of the Patras Workshop
2013, Mainz, June 201
Axions and Cosmic Rays
We investigate the propagation of a charged particle in a spatially constant
but time dependent pseudoscalar background. Physically this pseudoscalar
background could be provided by a relic axion density. The background leads to
an explicit breaking of Lorentz invariance; as a consequence processes such as
or are possible within some kinematical
constraints. The phenomenon is described by the QED lagrangian extended with a
Chern-Simons term that contains a 4-vector which characterizes the breaking of
Lorentz invariance induced by the time-dependent background. While the
radiation induced (similar to the Cherenkov effect) is too small to influence
the propagation of cosmic rays in a significant way, the hypothetical detection
of the photons radiated by high energy cosmic rays via this mechanism would
provide an indirect way of verifying the cosmological relevance of axions. We
discuss on the order of magnitude of the effect.Comment: 16 pages, 3 figures. To appear in Proceedings of the Quarks 2010
International Seminar, Kolomna, Russi
U(1) lattice gauge theory and N=2 supersymmetric Yang-Mills theory
We discuss the physics of four-dimensional compact U(1) lattice gauge theory
from the point of view of softly broken N=2 supersymmetric SU(2) Yang-Mills
theory. We provide arguments in favor of (pseudo-)critical mass exponents 1/3,
5/11 and 1/2, in agreement with the values observed in the computer
simulations. We also show that the J^{CP} assignment of some of the lowest
lying states can be naturally explained.Comment: 19 pages, LaTe