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3 pages, 190 KiB

Open AccessEditorial

Lorentz Violation in Astroparticles and Gravitational Waves

by Marco Schreck

Galaxies 2022, 10(1), 13; https://doi.org/10.3390/galaxies10010013 - 17 Jan 2022

Cited by 1 | Viewed by 2284

Abstract

Lorentz invariance is one of the fundamental continuous symmetries of the laws of nature [...] Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

Research

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26 pages, 409 KiB

Open AccessArticle

Lorentz Violation by the Preferred Frame Effects and Cosmic and Gamma Ray Propagation

by Georgy I. Burde

Galaxies 2021, 9(4), 119; https://doi.org/10.3390/galaxies9040119 - 14 Dec 2021

Cited by 4 | Viewed by 2662

Abstract

The ‘relativity with a preferred frame’, designed to reconcile the relativity principle with the existence of the cosmological preferred frame, incorporates the preferred frame at the level of special relativity (SR) while retaining the fundamental spacetime symmetry, which, in the standard SR, manifests [...] Read more.

The ‘relativity with a preferred frame’, designed to reconcile the relativity principle with the existence of the cosmological preferred frame, incorporates the preferred frame at the level of special relativity (SR) while retaining the fundamental spacetime symmetry, which, in the standard SR, manifests itself as Lorentz invariance. In this paper, the processes, accompanying the propagation of cosmic rays and gamma rays through the background radiation from distant sources to Earth, are considered on the basis of particle dynamics and electromagnetic field dynamics developed within the framework of the ‘relativity with a preferred frame’. Applying the theory to the photopion-production and pair-production processes shows that the modified particle dynamics and electrodynamics lead to measurable signatures in the observed cosmic and gamma-ray spectra which can provide an interpretation of some puzzling features found in the observational data. Other processes responsible for gamma-ray attenuation are considered. It is found, in particular, that electromagnetic cascades, developing on cosmic microwave background and extragalactic background light, may be reduced or suppressed due to the preferred frame effects which should influence the shape of the very high-energy gamma-ray spectra. Other possible observational consequences of the theory, such as the birefringence of light propagating in vacuo and dispersion, are discussed. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

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25 pages, 1183 KiB

Open AccessArticle

Quantum Gravity Phenomenology Induced in the Propagation of UHECR, a Kinematical Solution in Finsler and Generalized Finsler Spacetime

by Marco Danilo Claudio Torri

Galaxies 2021, 9(4), 103; https://doi.org/10.3390/galaxies9040103 - 14 Nov 2021

Cited by 8 | Viewed by 2361

Abstract

It is well-known that the universe is opaque to the propagation of Ultra-High-Energy Cosmic Rays (UHECRs) since these particles dissipate energy during their propagation interacting with the background fields present in the universe, mainly with the Cosmic Microwave Background (CMB) in the so-called [...] Read more.

It is well-known that the universe is opaque to the propagation of Ultra-High-Energy Cosmic Rays (UHECRs) since these particles dissipate energy during their propagation interacting with the background fields present in the universe, mainly with the Cosmic Microwave Background (CMB) in the so-called GZK cut-off phenomenon. Some experimental evidence seems to hint at the possibility of a dilation of the GZK predicted opacity sphere. It is well-known that kinematical perturbations caused by supposed quantum gravity (QG) effects can modify the foreseen GZK opacity horizon. The introduction of Lorentz Invariance Violation can indeed reduce, and in some cases making negligible, the CMB-UHECRs interaction probability. In this work, we explore the effects induced by modified kinematics in the UHECR lightest component phenomenology from the QG perspective. We explore the possibility of a geometrical description of the massive fermions interaction with the supposed quantum structure of spacetime in order to introduce a Lorentz covariance modification. The kinematics are amended, modifying the dispersion relations of free particles in the context of a covariance-preserving framework. This spacetime description requires a more general geometry than the usual Riemannian one, indicating, for instance, the Finsler construction and the related generalized Finsler spacetime as ideal candidates. Finally we investigate the correlation between the magnitude of Lorentz covariance modification and the attenuation length of the photopion production process related to the GZK cut-off, demonstrating that the predicted opacity horizon can be dilated even in the context of a theory that does not require any privileged reference frame. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

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33 pages, 978 KiB

Open AccessArticle

Astrophysical Neutrinos in Testing Lorentz Symmetry

by Ágnes Roberts

Galaxies 2021, 9(3), 47; https://doi.org/10.3390/galaxies9030047 - 8 Jul 2021

Cited by 5 | Viewed by 2785

Abstract

An overview of searches related to neutrinos of astronomical and astrophysical origin performed within the framework of the Standard-Model Extension is provided. For this effective field theory, key definitions, intriguing physical consequences, and the mathematical formalism are summarized within the neutrino sector to [...] Read more.

An overview of searches related to neutrinos of astronomical and astrophysical origin performed within the framework of the Standard-Model Extension is provided. For this effective field theory, key definitions, intriguing physical consequences, and the mathematical formalism are summarized within the neutrino sector to search for effects from a background that could lead to small deviations from Lorentz symmetry. After an introduction to the fundamental theory, examples of various experiments within the astronomical and astrophysical context are provided. Order-of-magnitude bounds of SME coefficients are shown illustratively for the tight constraints that this sector allows us to place on such violations. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

10 pages, 345 KiB

Open AccessFeature PaperArticle

Constraints on Lorentz Invariance Violation with Multiwavelength Polarized Astrophysical Sources

by Qi-Qi Zhou, Shuang-Xi Yi, Jun-Jie Wei and Xue-Feng Wu

Galaxies 2021, 9(2), 44; https://doi.org/10.3390/galaxies9020044 - 20 Jun 2021

Cited by 10 | Viewed by 2100

Abstract

Possible violations of Lorentz invariance (LIV) can produce vacuum birefringence, which results in a frequency-dependent rotation of the polarization plane of linearly polarized light from distant sources. In this paper, we try to search for a frequency-dependent change of the linear polarization angle [...] Read more.

Possible violations of Lorentz invariance (LIV) can produce vacuum birefringence, which results in a frequency-dependent rotation of the polarization plane of linearly polarized light from distant sources. In this paper, we try to search for a frequency-dependent change of the linear polarization angle arising from vacuum birefringence in the spectropolarimetric data of astrophysical sources. We collect five blazars with multiwavelength polarization measurements in different optical bands

(U B V R I)

. Taking into account the observed polarization angle contributions from both the intrinsic polarization angle and the rotation angle induced by LIV, and assuming that the intrinsic polarization angle is an unknown constant, we obtain new constraints on LIV by directly fitting the multiwavelength polarimetric data of the five blazars. Here, we show that the birefringence parameter

η

quantifying the broken degree of Lorentz invariance is limited to be in the range of $- 9.63 \times 10^{- 8} < η < 6.55 \times 10^{- 6}$ at the

2 σ

confidence level, which is as good as or represents one order of magnitude improvement over the results previously obtained from ultraviolet/optical polarization observations. Much stronger limits can be obtained by future multiwavelength observations in the gamma-ray energy band. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

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10 pages, 277 KiB

Open AccessFeature PaperArticle

On Plane Wave Solutions in Lorentz-Violating Extensions of Gravity

by J. R. Nascimento, A. Yu. Petrov and A. R. Vieira

Galaxies 2021, 9(2), 32; https://doi.org/10.3390/galaxies9020032 - 8 May 2021

Cited by 8 | Viewed by 2276

Abstract

In this paper, we obtain dispersion relations corresponding to plane wave solutions in Lorentz-breaking extensions of gravity with dimension 3, 4, 5 and 6 operators. We demonstrate that these dispersion relations display a usual Lorentz-invariant mode when the corresponding additive term involves higher [...] Read more.

In this paper, we obtain dispersion relations corresponding to plane wave solutions in Lorentz-breaking extensions of gravity with dimension 3, 4, 5 and 6 operators. We demonstrate that these dispersion relations display a usual Lorentz-invariant mode when the corresponding additive term involves higher derivatives. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

9 pages, 289 KiB

Open AccessFeature PaperArticle

Constraints on Space-Time-Matter Theory in the Framework of the Standard-Model Extension

by James Overduin, Hamna Ali and Francis Walz

Galaxies 2021, 9(2), 26; https://doi.org/10.3390/galaxies9020026 - 26 Apr 2021

Cited by 3 | Viewed by 2732

Abstract

We use experimental limits on Lorentz violation within the framework of the Standard-Model Extension to derive quantitative constraints on Space-Time-Matter theory, a version of Kaluza–Klein theory in which the cylinder condition is relaxed so that four-dimensional physics can in principle depend on the [...] Read more.

We use experimental limits on Lorentz violation within the framework of the Standard-Model Extension to derive quantitative constraints on Space-Time-Matter theory, a version of Kaluza–Klein theory in which the cylinder condition is relaxed so that four-dimensional physics can in principle depend on the extra coordinates. The extra dimensions are not necessarily compact or length-like. We find that the associated variation in fundamental quantities such as rest mass must occur slowly, on cosmological scales. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

10 pages, 595 KiB

Open AccessFeature PaperArticle

Signatures of Lorentz Violation in Continuous Gravitational-Wave Spectra of Ellipsoidal Neutron Stars

by Rui Xu, Yong Gao and Lijing Shao

Galaxies 2021, 9(1), 12; https://doi.org/10.3390/galaxies9010012 - 29 Jan 2021

Cited by 10 | Viewed by 3448

Abstract

We studied the effects of the Lorentz invariance violation on the rotation of neutron stars (NSs) in the minimal gravitational Standard-Model Extension framework, and calculated the quadrupole radiation generated by them. Aiming at testing Lorentz invariance with observations of continuous gravitational waves (GWs) [...] Read more.

We studied the effects of the Lorentz invariance violation on the rotation of neutron stars (NSs) in the minimal gravitational Standard-Model Extension framework, and calculated the quadrupole radiation generated by them. Aiming at testing Lorentz invariance with observations of continuous gravitational waves (GWs) from rotating NSs in the future, we compared the GW spectra of a rotating ellipsoidal NS under Lorentz-violating gravity with those of a Lorentz-invariant one. The former were found to possess frequency components higher than the second harmonic, which does not happen for the latter, indicating those higher frequency components to be potential signatures of Lorentz violation in continuous GW spectra of rotating NSs. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

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9 pages, 823 KiB

Open AccessFeature PaperArticle

Oscillating Cosmological Force Modifies Newtonian Dynamics

by Igor I. Smolyaninov

Galaxies 2020, 8(2), 45; https://doi.org/10.3390/galaxies8020045 - 22 May 2020

Cited by 3 | Viewed by 2868

Abstract

In the Newtonian limit of general relativity a force acting on a test mass in a central gravitational field is conventionally defined by the attractive Newtonian gravity (inverse square) term plus a small repulsive cosmological force, which is proportional to the slow acceleration [...] Read more.

In the Newtonian limit of general relativity a force acting on a test mass in a central gravitational field is conventionally defined by the attractive Newtonian gravity (inverse square) term plus a small repulsive cosmological force, which is proportional to the slow acceleration of the universe expansion. In this paper we considered the cosmological-force correction due to fast quantum oscillations of the universe scale factor as a potential solution of the cosmological constant problem. These fast fluctuations of the cosmological scale factor violate Lorentz invariance at the Planck scale, and they induce strong changes to the current sign and magnitude of the average cosmological force, thus making it one of the potential probable causes for the modification of Newtonian dynamics in galaxy-scale systems. The modified cosmological force may be responsible for the recently discovered “cosmic-clock” behavior of disk galaxies in the low-redshift universe. The obtained results have strong implications for astroparticle physics since they demonstrate that typical galaxy rotation curves may be obtained without (or almost without) dark-matter particles. Full article

(This article belongs to the Special Issue Lorentz Violation in Astroparticles and Gravitational Waves)

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