3,608 research outputs found

    Exploring the CPT violation and birefringence of gravitational waves with ground- and space-based gravitational-wave interferometers

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    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

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    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 101410^{-14}. 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

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    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 TT,TE,EE,BBTT,TE,EE,BB angular correlation coefficients with l=l+1l'=l+1 and TB,EBTB,EB with l=ll'=l. The numerical results show that the anisotropic contributions to angular correlation coefficients depend on mm, and TETE and ETET 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

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    Considering the mass splitting between three active neutrinos, we represent the new constraints on the sum of neutrino mass mν\sum m_\nu 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 Planck\textit{Planck}~2015 data of temperature anisotropy and polarizations of Cosmic Microwave Background (CMB), we find that the 95%95\% C.L. upper bounds on mν\sum m_\nu refer to mν,NH<0.18\sum m_{\nu,\rm NH}<0.18 eV for normal hierarchy (NH), mν,IH<0.20\sum m_{\nu,\rm IH}<0.20 eV for inverted hierarchy (IH) and mν,DH<0.15\sum m_{\nu,\rm DH}<0.15 eV for degenerate hierarchy (DH) respectively, and the normal hierarchy is slightly preferred than the inverted one (Δχ2χNH2χIH23.4\Delta \chi^2\equiv \chi^2_{\rm NH}-\chi^2_{\rm IH} \simeq -3.4). 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

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    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