1,017 research outputs found
Erratum (astro-ph/0510172): Robust Limits on Lorentz Violation from Gamma-Ray Bursts
We correct the fitting formula used in refs. [1,2] to obtain a robust limit
on a violation of Lorentz invariance that depends linearly on the photon
energy. The correction leads to a slight increase of the limit on the scale of
the violation, to M > 1.4 x 10^{16} GeV.Comment: four pages latex, two eps figures, uses special macro
High contrast D line electromagnetically induced transparency in nanometric-thin rubidium vapor cell
Electromagnetically induced transparency (EIT) on atomic D line of
rubidium is studied using a nanometric-thin cell with atomic vapor column
length in the range of L= 400 - 800 nm. It is shown that the reduction of the
cell thickness by 4 orders as compared with an ordinary cm-size cell still
allows to form an EIT resonance for ( nm) with the
contrast of up to 40%. Remarkable distinctions of EIT formation in
nanometric-thin and ordinary cells are demonstrated. Despite the Dicke effect
of strong spectral narrowing and increase of the absorption for , EIT resonance is observed both in the absorption and the fluorescence
spectra for relatively low intensity of the coupling laser. Well resolved
splitting of the EIT resonance in moderate magnetic field for
can be used for magnetometry with nanometric spatial resolution. The presented
theoretical model well describes the observed results.Comment: Submitted to Applied Physics B: Lasers and Optics, 9 pages, 10
figure
Lorentz Invariance Violation induced time delays in GRBs in different cosmological models
Lorentz Invariance Violation (LIV) manifesting itself by energy dependent
modification of standard relativistic dispersion relation has recently
attracted a considerable attention. Ellis et al. previously investigated the
energy dependent time offsets in different energy bands on a sample of gamma
ray bursts and, assuming standard cosmological model, they found a weak
indication for redshift dependence of time delays suggestive of LIV. Going
beyond the CDM cosmology we extend this analysis considering also four
alternative models of dark energy (quintessence with constant and variable
equation of state, Chaplygin gas and brane-world cosmology). It turns out that
the effect noticed by Ellis et al. is also present in those models and is the
strongest for quintessence with variable equation of state.Comment: 14 pages, 1 figur
GRB 051221A and Tests of Lorentz Symmetry
Various approaches to quantum gravity suggest the possibility of violation of
Lorentz symmetry at very high energies. In these cases we expect a modification
at low energies of the dispersion relation of photons that contains extra
powers of the momentum suppressed by a high energy scale. These terms break
boost invariance and can be tested even at relatively low energies. We use the
light curves of the very bright short Gamma-Ray Burst GRB 051221A and compare
the arrival times of photons at different energies with the expected time delay
due to a modified dispersion relation. As no time delay was observed, we set a
lower bound of 0.0066 E_{pl} \sim 0.66 10^{17} GeV on the scale of Lorentz
invariance violation.Comment: 9 pages, 2 figure
Probing Lorentz Violation in Neutrino Propagation from a Core-Collapse Supernova
Supernova explosions provide the most sensitive probes of neutrino
propagation, such as the possibility that neutrino velocities might be affected
by the foamy structure of space-time thought to be generated by
quantum-gravitational (QG) effects. Recent two-dimensional simulations of the
neutrino emissions from core-collapse supernovae suggest that they might
exhibit variations in time on the scale of a few milliseconds. We analyze
simulations of such neutrino emissions using a wavelet technique, and consider
the limits that might be set on a linear or quadratic violation of Lorentz
invariance in the group velocities of neutrinos of different energies, v/c = [1
\pm (E/M_{nuLV1})] or [1 \pm (E/M_{\nuLV2})^2], if variations on such short
time scales were to be observed, where the mass scales M_{nuLVi} might appear
in models of quantum gravity. We find prospective sensitivities to M_{nuLV1} ~
2 X 10^{13} GeV and M_{nuLV2} ~ 10^6 GeV at the 95% confidence level, up to two
orders of magnitude beyond estimates made using previous one-dimensional
simulations of core-collapse supernovae. We also analyze the prospective
sensitivities to scenarios in which the propagation times of neutrinos of fixed
energies are subject to stochastic fluctuations.Comment: 29 pages, 9 figures. A subsection added. The version to appear in
Phys. Rev.
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