4,301 research outputs found
Exploring the CPT violation and birefringence of gravitational waves with ground- and space-based gravitational-wave interferometers
In the gravitational sector, we study the CPT violation and birefringence of
gravitational waves. In presence of the CPT violation, a relative dephasing is
generated between two circular polarization states of gravitational waves. This
effect induces the birefringence of gravitational waves. We predict the
gravitational waveform corrected by it and estimate the expected constraints on
it from Advanced Laser Interferometer Gravitational-Wave Observatory, Einstein
Telescope and Laser Interferometer Space Antenna.Comment: Preprint, 16 pages, 1 figure, 1 table, 2 appendices. All comments are
welcom
Constraints on spacetime anisotropy and Lorentz violation from the GRAAL experiment
The GRAAL experiment could constrain the variations of the speed of light.
The anisotropy of the speed of light may imply that the spacetime is
anisotropic. Finsler geometry is a reasonable candidate to deal with the
spacetime anisotropy. In this paper, the Lorentz invariance violation (LIV) of
the photon sector is investigated in the locally Minkowski spacetime. The
locally Minkowski spacetime is a class of flat Finsler spacetime and refers a
metric with the anisotropic departure from the Minkowski one. The LIV matrices
used to fit the experimental data are represented in terms of these metric
deviations. The GRAAL experiment constrains the spacetime anisotropy to be less
than . In addition, we find that the simplest Finslerian photon
sector could be viewed as a geometric representation of the photon sector in
the minimal standard model extension (SME).Comment: 13 pages, 2 tables. Two typos are corrected in Table
Primordial power spectrum of tensor perturbations in Finsler spacetime
We first investigate the gravitational wave in the flat Finsler spacetime. In
the Finslerian universe, we derive the perturbed gravitational field equation
with tensor perturbations. The Finslerian background spacetime breaks
rotational symmetry and induces parity violation. Then we obtain the modified
primordial power spectrum of tensor perturbations. The parity violation feature
requires that the anisotropic effect contributes to angular
correlation coefficients with and with . The numerical
results show that the anisotropic contributions to angular correlation
coefficients depend on , and and angular correlation coefficients
are different.Comment: 15 pages, 12 fugures. arXiv admin note: text overlap with
arXiv:1502.0225
Constraints on the neutrino mass and mass hierarchy from cosmological observations
Considering the mass splitting between three active neutrinos, we represent
the new constraints on the sum of neutrino mass by updating the
anisotropic analysis of Baryon Acoustic Oscillation (BAO) scale in the CMASS
and LOWZ galaxy samples from Data Release 12 of the SDSS-III Baryon Oscillation
Spectroscopic Survey (BOSS DR12). Combining the BAO data of 6dFGS, MGS, LOWZ
and CMASS with ~2015 data of temperature anisotropy and
polarizations of Cosmic Microwave Background (CMB), we find that the
C.L. upper bounds on refer to eV for
normal hierarchy (NH), eV for inverted hierarchy
(IH) and eV for degenerate hierarchy (DH)
respectively, and the normal hierarchy is slightly preferred than the inverted
one (). In
addition, the additional relativistic degrees of freedom and massive sterile
neutrinos are neither favored at present.Comment: 12 pages, 3 tables, 1 figure; refs adde
Neutrino superluminality without Cherenkov-like processes in Finslerian special relativity
Recently, Cohen and Glashow [A.G. Cohen, S.L. Glashow, Phys. Rev. Lett. {\bf
107}, 181803 (2011)] pointed out that the superluminal neutrinos reported by
the OPERA would lose their energy rapidly via the Cherenkov-like process. The
Cherenkov-like process for the superluminal particles would be forbidden if the
principle of special relativity holds in any frame instead violated with a
preferred frame. We have proposed that the Finslerian special relativity could
account for the data of the neutrino superluminality (arXiv:1110.6673[hep-ph]).
The Finslerian special relativity preserves the principle of special relativity
and involves a preferred direction while consists with the causality. In this
paper, we prove that the energy-momentum conservation is preserved and the
energy-momentum is well defined in Finslerian special relativity. The
Cherenkov-like process is forbidden in the Finslerian special relativity. Thus,
the superluminal neutrinos would not lose energy in their distant propagation.Comment: 9 pages, no figure. Version for publication in PL
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