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Journal articles on the topic 'Lorentz Violations'

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Author: Grafiati

Published: 14 March 2023

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1

Jentschura, Ulrich D. "Squeezing the Parameter Space for Lorentz Violation in the Neutrino Sector with Additional Decay Channels." Particles 3, no. 3 (August 26, 2020): 630–41. http://dx.doi.org/10.3390/particles3030041.

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The hypothesis of Lorentz violation in the neutrino sector has intrigued scientists for the last two to three decades. A number of theoretical arguments support the emergence of such violations, first and foremost for neutrinos, which constitute the “most elusive” and “least interacting” particles known to mankind. It is of obvious interest to place stringent bounds on the Lorentz-violating parameters in the neutrino sector. In the past, the most stringent bounds have been placed by calculating the probability of neutrino decay into a lepton pair, a process made kinematically feasible by Lorentz violation in the neutrino sector, above a certain threshold. However, even more stringent bounds can be placed on the Lorentz-violating parameters if one takes into account, additionally, the possibility of neutrino splitting, i.e., of neutrino decay into a neutrino of lower energy, accompanied by “neutrino-pair Čerenkov radiation.” This process has a negligible threshold and can be used to improve the bounds on Lorentz-violating parameters in the neutrino sector. Finally, we take the opportunity to discuss the relation of Lorentz and gauge symmetry breaking, with a special emphasis on the theoretical models employed in our calculations.

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2

Hashimoto, Koji. "Lorentz violation and vacuum structure in string theories." International Journal of Modern Physics: Conference Series 30 (January 2014): 1460274. http://dx.doi.org/10.1142/s2010194514602749.

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We briefly describe what is expected in superstring theory for the Lorentz violation and related CPT violation, for non-experts. Superstring theory is an advanced theory for quantum gravity, but we are still not at a stage of evaluating possible Lorentz violations, although there are proposals for compactification mechanisms of space-time.

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3

Bailey, Quentin G. "Lorentz violation and gravity." Proceedings of the International Astronomical Union 5, S261 (April 2009): 409–13. http://dx.doi.org/10.1017/s1743921309990706.

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AbstractIn the last decade, a variety of high-precision experiments have searched for miniscule violations of Lorentz symmetry. These searches are largely motivated by the possibility of uncovering experimental signatures from a fundamental unified theory. Experimental results are reported in the framework called the Standard-Model Extension (SME), which describes general Lorentz violation for each particle species in terms of its coefficients for Lorentz violation. Recently, the role of gravitational experiments in probing the SME has been explored in the literature. In this talk, I will summarize theoretical and experimental aspects of these works. I will also discuss recent lunar laser ranging and atom interferometer experiments, which place stringent constraints on gravity coefficients for Lorentz violation.

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4

Mewes, Matthew. "Non-Minimal Lorentz Violation in Macroscopic Matter." Symmetry 12, no. 12 (December 7, 2020): 2026. http://dx.doi.org/10.3390/sym12122026.

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The effects of Lorentz and CPT violations on macroscopic objects are explored. Effective composite coefficients for Lorentz violation are derived in terms of coefficients for electrons, protons, and neutrons in the Standard-Model Extension, including all minimal and non-minimal violations. The hamiltonian and modified Newton’s second law for a test body are derived. The framework is applied to free-fall and torsion-balance tests of the weak equivalence principle and to orbital motion. The effects on continuous media are studied, and the frequency shifts in acoustic resonators are calculated.

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5

Moura, Celio A., and Fernando Rossi-Torres. "Searches for Violation of CPT Symmetry and Lorentz Invariance with Astrophysical Neutrinos." Universe 8, no. 1 (January 11, 2022): 42. http://dx.doi.org/10.3390/universe8010042.

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Neutrinos are a powerful tool for searching physics beyond the standard model of elementary particles. In this review, we present the status of the research on charge-parity-time (CPT) symmetry and Lorentz invariance violations using neutrinos emitted from the collapse of stars such as supernovae and other astrophysical environments, such as gamma-ray bursts. Particularly, supernova neutrino fluxes may provide precious information because all neutrino and antineutrino flavors are emitted during a burst of tens of seconds. Models of quantum gravity may allow the violation of Lorentz invariance and possibly of CPT symmetry. Violation of Lorentz invariance may cause a modification of the dispersion relation and, therefore, in the neutrino group velocity as well in the neutrino wave packet. These changes can affect the arrival time signal registered in astrophysical neutrino detectors. Direction or time-dependent oscillation probabilities and anisotropy of the neutrino velocity are manifestations of the same kind of new physics. CPT violation, on the other hand, may be responsible for different oscillation patterns for neutrino and antineutrino and unconventional energy dependency of the oscillation phase or of the mixing angles. Future perspectives for possible CPT and Lorentz violating systems are also presented.

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6

Halprin, Arthur, and Hang Bae Kim. "Mapping Lorentz invariance violations into equivalence principle violations." Physics Letters B 469, no. 1-4 (December 1999): 78–80. http://dx.doi.org/10.1016/s0370-2693(99)01258-7.

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7

Voss, D. "PHYSICS: Looking for Lorentz Violations." Science 315, no. 5812 (February 2, 2007): 574d—575d. http://dx.doi.org/10.1126/science.315.5812.574d.

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8

Santos, A. F., and Faqir C. Khanna. "Lorentz violation, gravitoelectromagnetic field and Bhabha scattering." International Journal of Modern Physics A 33, no. 02 (January 20, 2018): 1850015. http://dx.doi.org/10.1142/s0217751x1850015x.

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Lorentz symmetry is a fundamental symmetry in the Standard Model (SM) and in General Relativity (GR). This symmetry holds true for all models at low energies. However, at energies near the Planck scale, it is conjectured that there may be a very small violation of Lorentz symmetry. The Standard Model Extension (SME) is a quantum field theory that includes a systematic description of Lorentz symmetry violations in all sectors of particle physics and gravity. In this paper, SME is considered to study the physical process of Bhabha Scattering in the Gravitoelectromagnetism (GEM) theory. GEM is an important formalism that is valid in a suitable approximation of general relativity. A new nonminimal coupling term that violates Lorentz symmetry is used in this paper. Differential cross-section for gravitational Bhabha scattering is calculated. The Lorentz violation contributions to this GEM scattering cross-section are small and are similar in magnitude to the case of the electromagnetic field.

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9

Cortés, J. L., and Justo López-Sarrión. "Fine-tuning problems in quantum field theory and Lorentz invariance: A scalar-fermion model with a physical momentum cutoff." International Journal of Modern Physics A 32, no. 15 (May 23, 2017): 1750084. http://dx.doi.org/10.1142/s0217751x17500841.

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In this paper, we study the consistency of having Lorentz invariance as a low energy approximation within the quantum field theory framework. A model with a scalar and a fermion field is used to show how a Lorentz invariance violating high momentum scale, a physical cutoff rendering the quantum field theory finite, can be made compatible with a suppression of Lorentz invariance violations at low momenta. The fine tuning required to get this suppression and to have a light scalar particle in the spectrum are determined at one loop.

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10

MACCIONE, LUCA, ANDREA M. TAYLOR, DAVID M. MATTINGLY, and STEFANO LIBERATI. "ULTRA-HIGH-ENERGY COSMIC RAYS AND PLANCK-SUPPRESSED LORENTZ INVARIANCE VIOLATION." International Journal of Modern Physics D 18, no. 10 (October 2009): 1621–25. http://dx.doi.org/10.1142/s0218271809015527.

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We investigate the consequences of higher dimension Lorentz violating, CPT even kinetic operators that couple standard model fields to a non-zero vector field in an Effective Field Theory framework. Comparing the ultra-high energy cosmic ray spectrum reconstructed in the presence of such terms with data from the Pierre Auger Observatory allows us to establish stringent bounds on O(E/M Pl )2 suppressed violations of Lorentz invariance.

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11

Wei, Jin-Nan, Zi-Ke Liu, Jun-Jie Wei, Bin-Bin Zhang, and Xue-Feng Wu. "Exploring Anisotropic Lorentz Invariance Violation from the Spectral-Lag Transitions of Gamma-Ray Bursts." Universe 8, no. 10 (October 6, 2022): 519. http://dx.doi.org/10.3390/universe8100519.

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The observed spectral lags of gamma-ray bursts (GRBs) have been widely used to explore possible violations of Lorentz invariance. However, these studies were generally performed by concentrating on the rough time lag of a single highest-energy photon and ignoring the intrinsic time lag at the source. A new way to test nonbirefringent Lorentz-violating effects has been proposed by analyzing the multi-photon spectral-lag behavior of a GRB that displays a positive-to-negative transition. This method gives both a plausible description of the intrinsic energy-dependent time lag and comparatively robust constraints on Lorentz-violating effects. In this work, we conduct a systematic search for Lorentz-violating photon dispersion from the spectral-lag transition features of 32 GRBs. By fitting the spectral-lag data of these 32 GRBs, we place constraints on a variety of isotropic and anisotropic Lorentz-violating coefficients with mass dimension d=6 and 8. While our dispersion constraints are not competitive with existing bounds, they have the promise to complement the full coefficient space.

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12

Bekaert, Xavier, Nicolas Boulanger, and Justin F. Vázquez-Poritz. "Gravitational Lorentz Violations from M-Theory." Journal of High Energy Physics 2002, no. 10 (October 24, 2002): 053. http://dx.doi.org/10.1088/1126-6708/2002/10/053.

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13

Sidharth, B. G. "Different Routes to Lorentz Symmetry Violations." Foundations of Physics 38, no. 1 (November 27, 2007): 89–95. http://dx.doi.org/10.1007/s10701-007-9193-x.

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14

Martínez, María Rodríguez, and Tsvi Piran. "Constraining Lorentz violations with gamma ray bursts." Journal of Cosmology and Astroparticle Physics 2006, no. 04 (April 19, 2006): 006. http://dx.doi.org/10.1088/1475-7516/2006/04/006.

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15

Cowsik, R., and B. V. Sreekantan. "A bound on violations of Lorentz invariance." Physics Letters B 449, no. 3-4 (March 1999): 219–22. http://dx.doi.org/10.1016/s0370-2693(99)00016-7.

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16

Kostelecký, V. Alan, and Matthew Mewes. "Lorentz and diffeomorphism violations in linearized gravity." Physics Letters B 779 (April 2018): 136–42. http://dx.doi.org/10.1016/j.physletb.2018.01.082.

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17

Camacho, Abel. "White dwarfs as test objects of Lorentz violations." Classical and Quantum Gravity 23, no. 24 (November 3, 2006): 7355–68. http://dx.doi.org/10.1088/0264-9381/23/24/009.

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18

Napolitano, Fabrizio, Sergio Bartalucci, Sergio Bertolucci, Massimiliano Bazzi, Mario Bragadireanu, Cesidio Capoccia, Michael Cargnelli, et al. "Testing the Pauli Exclusion Principle with the VIP-2 Experiment." Symmetry 14, no. 5 (April 27, 2022): 893. http://dx.doi.org/10.3390/sym14050893.

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Violations of the Pauli Exclusion Principle (PEP), albeit small, could be motivated by physics beyond the Standard Model, ranging from violation of Lorentz invariance to extra space dimensions. This scenario can be experimentally constrained through dedicated, state-of-the-art X-ray spectroscopy, searching for a forbidden atomic transition from the L shell to the K shell already occupied by two electrons. The VIP-2 Experiment located at the underground Gran Sasso National Laboratories of INFN (Italy) tests PEP violations by introducing new electrons via a direct current in a copper conductor, measuring the X-ray energies through a silicon drift detector. Bayesian and frequentist analyses of approximately six months of data taken with the fully operational setup is presented, setting the strongest limit to date on the PEP violation shown by the VIP collaboration. The upper bound on PEP violation are placed at 90% CL β2/2≤6.8×10−42 with the Bayesian approach, and β2/2≤7.1×10−42 with the frequentist CLs technique.

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19

Díaz, Jorge S. "Neutrinos as Probes of Lorentz Invariance." Advances in High Energy Physics 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/962410.

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Neutrinos can be used to search for deviations from exact Lorentz invariance. The worldwide experimental program in neutrino physics makes these particles a remarkable tool to search for a variety of signals that could reveal minute relativity violations. This paper reviews the generic experimental signatures of the breakdown of Lorentz symmetry in the neutrino sector.

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20

LIPA, J. A., SUWEN WANG, J. NISSEN, M. KASEVICH, and J. MESTER. "DETECTING LORENTZ INVARIANCE VIOLATIONS IN THE 10-20 RANGE." International Journal of Modern Physics D 16, no. 12b (December 2007): 2393–98. http://dx.doi.org/10.1142/s0218271807011528.

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In recent years the possibility has been raised of Lorentz invariance violations arising from physics beyond the Standard Model. Some of these effects manifest themselves as small anisotropies in the velocity of light, c. By comparing the resonant frequencies of cavity modes with different spatial alignments, limits on the order δ c/c < 10-15 have been set and some further improvement can be expected. However, the largest Lorentz violations originating at the Planck scale are expected to manifest themselves as a fractional frequency variation at the 10-17 level in the absence of suppression factors. Space experiments have been proposed to approach the 10-18 level. Here we explore the possibilities for pushing further and show that it is possible in principle to reach well into the 10-20 range with existing technology. This could be done in a very quiet cryogenic environment, such as the drag-free orbiter being developed for the Satellite Test of the Equivalence Principle (STEP).

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21

BODOOR, K., H. J. WEBER, T. FREDERICO, and M. BEYER. "VIOLATIONS OF LORENTZ COVARIANCE IN LIGHT FRONT QUARK MODELS." Modern Physics Letters A 15, no. 36 (November 30, 2000): 2191–204. http://dx.doi.org/10.1142/s0217732300002814.

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Electromagnetic form factors of the nucleon from relativistic quark models are analyzed: Results from null-plane projection of the Feynman triangle diagram are compared with a Bakamjian–Thomas model. The magnetic form factors of the models differ by about 15% at spacelike momentum transfer 0.5 GeV2, while the charge form factors are much closer. Spurious contributions to electromagnetic form factors due to violations of rotational symmetry are eliminated for both models. One method changes magnetic form factors by about 10%, whereas the charge form factors remain nearly the same. Another one changes the charge form factor of the Bakamjian–Thomas model by more than 50%.

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22

Leon, David, Jonathan Kaufman, Brian Keating, and Matthew Mewes. "The cosmic microwave background and pseudo-Nambu–Goldstone bosons: Searching for Lorentz violations in the cosmos." Modern Physics Letters A 32, no. 02 (December 29, 2016): 1730002. http://dx.doi.org/10.1142/s0217732317300026.

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One of the most powerful probes of new physics is the polarized cosmic microwave background (CMB). The detection of a nonzero polarization angle rotation between the CMB surface of last scattering and today could provide evidence of Lorentz-violating physics. The purpose of this paper is two-fold. First, we review one popular mechanism for polarization rotation of CMB photons: the pseudo-Nambu–Goldstone boson (PNGB). Second, we propose a method to use the Polarbear experiment to constrain Lorentz-violating physics in the context of the Standard Model Extension (SME), a framework to standardize a large class of potential Lorentz-violating terms in particle physics.

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23

Sfarti, A. "The Mansouri–Sexl formalism for the Michelson–Morley experiment in nonvacuum media." Canadian Journal of Physics 86, no. 12 (December 1, 2008): 1417–19. http://dx.doi.org/10.1139/p08-019.

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In the present paper, we construct the complete Mansouri–Sexl formalism for the Michelson–Morley and Kennedy–Thorndike experiments executed in a refractive medium by extending their previous formalism derived for vacuum-based experiments. This is an important step since we will show that the experiments executed in a refractive medium give new possibilities for testing for Lorentz violations. In a previous paper, we developed the correct nonparametric treatment under the framework of special relativity, so no violation testing was possible. On the other hand, a parameterized theory, like that of Mansouri–Sexl is the standard way of testing for Lorentz symmetry violations. While other parameterized theories, like the Standard Model extension (SME) emerged in the late 1990s The Mansouri–Sexl formalism is still very much employed in experiments due to its relative simplicity and its lower number of parameters (three) versus the 19 parameters used in SME. This is why we are undertaking the novel step of constructing the corresponding Mansouri–Sexl formalism. Yet another novel attempt is to describe an unprecedented variation of the Kennedy–Thorndike experiment employing different refractive media for the interferometer arms. We will also demonstrate the advantages of deferring the expansion of the Mansouri–Sexl parameters a, b, and d as long as possible, thus obtaining a higher level of precision in deriving the violations.PACS No.: 03.30.+p

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24

Chen, Ya-Fen, Yu-Jie Tan, and Cheng-Gang Shao. "Experimental Design for Testing Local Lorentz Invariance Violations in Gravity." Symmetry 9, no. 10 (October 10, 2017): 219. http://dx.doi.org/10.3390/sym9100219.

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25

ALFARO, J., A. A. ANDRIANOV, M. CAMBIASO, P. GIACCONI, and R. SOLDATI. "BARE AND INDUCED LORENTZ AND CPT INVARIANCE VIOLATIONS IN QED." International Journal of Modern Physics A 25, no. 16 (June 30, 2010): 3271–306. http://dx.doi.org/10.1142/s0217751x10049293.

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We consider QED in a constant axial vector background (Æther). Further Lorentz invariance violations (LIV) might occur owing to radiative corrections. The phenomenology of this model is studied, clarifying issues related to the various regularizations employed, with a particular emphasis on the induced photon mass. To this concern, it is shown that in the presence of LIV dimensional regularization may produce a radiatively induced finite photon mass. The possible physical role of the large momentum cutoff is elucidated and the finite temperature radiative corrections are evaluated. Finally, various experimental bounds on the parameters of the model are discussed.

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26

Andrianov, Alexander A., Paola Giacconi, and Roberto Soldati. "Lorentz and CPT violations from Chern-Simons modifications of QED." Journal of High Energy Physics 2002, no. 02 (February 21, 2002): 030. http://dx.doi.org/10.1088/1126-6708/2002/02/030.

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27

Stoica, Horace. "Comment on 4D Lorentz invariance violations in the brane-world." Journal of High Energy Physics 2002, no. 07 (July 29, 2002): 060. http://dx.doi.org/10.1088/1126-6708/2002/07/060.

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28

Carmona, J. M., and J. L. Cortés. "Testing Lorentz invariance violations in the tritium beta-decay anomaly." Physics Letters B 494, no. 1-2 (November 2000): 75–80. http://dx.doi.org/10.1016/s0370-2693(00)01182-5.

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29

Vacaru, Sergiu I. "Finsler branes and quantum gravity phenomenology with Lorentz symmetry violations." Classical and Quantum Gravity 28, no. 21 (September 20, 2011): 215001. http://dx.doi.org/10.1088/0264-9381/28/21/215001.

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30

Roberts, Ágnes. "Astrophysical Neutrinos in Testing Lorentz Symmetry." Galaxies 9, no. 3 (July 8, 2021): 47. http://dx.doi.org/10.3390/galaxies9030047.

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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.

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31

Gallerati, Antonio, Matteo Luca Ruggiero, and Lorenzo Iorio. "Impact of Lorentz Violation Models on Exoplanets’ Dynamics." Universe 8, no. 11 (November 18, 2022): 608. http://dx.doi.org/10.3390/universe8110608.

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Many exoplanets have been detected by the radial velocity method, according to which the motion of a binary system around its center of mass can produce a periodical variation of the Doppler effect of the light emitted by the host star. These variations are influenced by both Newtonian and non-Newtonian perturbations to the dominant inverse-square acceleration; accordingly, exoplanetary systems lend themselves to testing theories of gravity alternative to general relativity. In this paper, we consider the impact of the Standard Model Extension (a model that can be used to test all possible Lorentz violations) on the perturbation of radial velocity and suggest that suitable exoplanets’ configurations and improvements in detection techniques may contribute to obtaining new constraints on the model parameters.

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32

Mavromatos, Nick E. "Models & Searches of CPT Violation: a personal, very partial, list." EPJ Web of Conferences 166 (2018): 00005. http://dx.doi.org/10.1051/epjconf/201816600005.

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In this talk, first I motivate theoretically, and then I review the phenomenology of, some models entailing CPT Violation (CPTV). The latter is argued to be responsible for the observed matter-antimatter asymmetry in the Cosmos, and may owe its origin to either Lorentz-violating background geometries, whose effects are strong in early epochs of the Universe but very weak today, being temperature dependent in general, or to an ill-defined CPT generator in some quantum gravity models entailing decoherence of quantum matter as a result of quantum degrees of freedom in the gravity sector that are inaccessible to the low-energy observers. In particular, for the latter category of CPTV, I argue that entangled states of neutral mesons (Kaons or B-systems), of central relevance to KLOE-2 experiment, can provide smoking-gun sensitive tests or even falsify some of these models. If CPT is ill-defined one may also encounter violations of the spin-statistics theorem, with possible consequences for the Pauli Exclusion Principle, which I only briefly touch upon.

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33

Battistel, O. A., and G. Dallabona. "Consistency in perturbative calculations and radiatively induced Lorentz and CPT violations." Journal of Physics G: Nuclear and Particle Physics 28, no. 8 (June 28, 2002): L23—L32. http://dx.doi.org/10.1088/0954-3899/28/8/101.

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34

Grojean, Christophe, Fernando Quevedo, Ivonne Zavala C., and Gianmassimo Tasinato. "Branes on charged dilatonic backgrounds: self-tuning, Lorentz violations and cosmology." Journal of High Energy Physics 2001, no. 08 (August 2, 2001): 005. http://dx.doi.org/10.1088/1126-6708/2001/08/005.

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35

Escobar, C. A., and R. Potting. "Bounding CPT and Lorentz symmetry violations through ultra-high-energy cosmic rays." Journal of Physics: Conference Series 1586 (August 2020): 012015. http://dx.doi.org/10.1088/1742-6596/1586/1/012015.

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36

Csáki, Csaba, Joshua Erlich, and Christophe Grojean. "ESSAY: The Cosmological Constant Problem in Brane-Worlds and Gravitational Lorentz Violations." General Relativity and Gravitation 33, no. 11 (November 2001): 1921–27. http://dx.doi.org/10.1023/a:1013094709013.

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37

Atoyev, Konstantin, Lilia Vovk, and Sergey Shpyga. "STUDYING THE INTERCONNECTION OF FOOD, ENERGY AND WATER RESOURCES USING THE THREE-SECTORAL LORENTZ MODEL." Journal of Automation and Information sciences 3 (May 1, 2021): 141–56. http://dx.doi.org/10.34229/1028-0979-2021-3-12.

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The work is devoted to the problem of creating new methods for complex modeling and risk management, which will allow to study synergistic interactions between sources of risks of various origins under conditions of uncertainty. The paper proposes an approach to the study of the relationship between food, water and energy resources using the three-sectoral Lorenz model, combining in a single structure similarly described sectors of the economy, each of which is considered in terms of the productivity level, the workplaces number and the structural disturbances level. As a mathematical modeling result, the conditions of the deterministic chaos origin in the minimum economic development model were determined and possible reasons of the global economy growing vulnerability to small changes in management parameters were identified. The problem of determining effective controls for minimizing the total structural violations on selected time interval is considered. As a result of model experiments, the trajectories of control parameters changes were determined, which make it possible to reduce the structural violations number. This is achieved through changes in the ratio of supply and demand levels for products, demand and supply for workplaces creation. The influence of random perturbations on the deterministic attractors stochastic deformation of the Lorentz model is considered. It is shown that, under random perturbations, the trajectories of the stochastic system leave a deterministic attractor and form around it a certain bundle with the corresponding probabilistic distribution. The further model complicating possibility by taking into account other sectors of the economy using the Lorenz model in a complex form is considered. In this case the task of studying n sectors of economy is reduced to considering the behavior of an ensemble of n coupled oscillators that generate oscillations with frequencies ωn, respectively. Collective synchronization of oscillator data can be investigated using Kuramoto’s model. The problem of managing socio-economic development under the chaotic modes origin conditions is reduced for a complex model to controlling the frequency of a nonzero mean field generated by coupled oscillators.

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38

Csáki, Csaba, Joshua Erlich, and Christophe Grojean. "Gravitational Lorentz violations and adjustment of the cosmological constant in asymmetrically warped spacetimes." Nuclear Physics B 604, no. 1-2 (June 2001): 312–42. http://dx.doi.org/10.1016/s0550-3213(01)00175-4.

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39

Gambini, Rodolfo, Saeed Rastgoo, and Jorge Pullin. "Small Lorentz violations in quantum gravity: do they lead to unacceptably large effects?" Classical and Quantum Gravity 28, no. 15 (June 28, 2011): 155005. http://dx.doi.org/10.1088/0264-9381/28/15/155005.

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40

SIDHARTH, B. G. "AN ULTRA HIGH ENERGY DIRAC EQUATION." International Journal of Modern Physics E 14, no. 06 (September 2005): 927–29. http://dx.doi.org/10.1142/s0218301305003594.

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Violations in Lorentz symmetry at very high energies are being discussed by Glashow, Coleman, the author and others. The motivation comes from certain observed events pertaining to ultra high energy cosmic rays, and also from theoretical quantum gravity studies, which require a discrete spacetime at the Planck scale. We examine the modification to the usual energy momentum relation, and in light of this, deduce a modified Dirac equation and examine some consequences.

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41

Gambini, Rodolfo, and Jorge Pullin. "Emergence of stringlike physics from Lorentz invariance in loop quantum gravity." International Journal of Modern Physics D 23, no. 12 (October 2014): 1442023. http://dx.doi.org/10.1142/s0218271814420231.

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We consider a quantum field theory on a spherically symmetric quantum spacetime described by loop quantum gravity. The spin network description of spacetime in such a theory leads to equations for the quantum field that are discrete. We show that to avoid significant violations of Lorentz invariance, one needs to consider specific nonlocal interactions in the quantum field theory similar to those that appear in string theory. This is the first sign that loop quantum gravity places restrictions on the type of matter considered, and points to a connection with string theory physics.

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42

Zhou, Qi-Qi, Shuang-Xi Yi, Jun-Jie Wei, and Xue-Feng Wu. "Constraints on Lorentz Invariance Violation with Multiwavelength Polarized Astrophysical Sources." Galaxies 9, no. 2 (June 20, 2021): 44. http://dx.doi.org/10.3390/galaxies9020044.

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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 (UBVRI). 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 −9.63×10−8<η<6.55×10−6 at the 2σ 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.

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Escors, David, and Grazyna Kochan. "Covariant Space-Time Line Elements in the Friedmann–Lemaitre–Robertson–Walker Geometry." Axioms 11, no. 7 (June 26, 2022): 310. http://dx.doi.org/10.3390/axioms11070310.

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Most quantum gravity theories quantize space-time on the order of Planck length (ℓp ). Some of these theories, such as loop quantum gravity (LQG), predict that this discreetness could be manifested through Lorentz invariance violations (LIV) over travelling particles at astronomical length distances. However, reports on LIV are controversial, and space discreetness could still be compatible with Lorentz invariance. Here, it is tested whether space quantization on the order of Planck length could still be compatible with Lorentz invariance through the application of a covariant geometric uncertainty principle (GeUP) as a constraint over geodesics in FRW geometries. Space-time line elements compatible with the uncertainty principle are calculated for a homogeneous, isotropic expanding Universe represented by the Friedmann–Lemaitre–Robertson–Walker solution to General Relativity (FLRW or FRW metric). A generic expression for the quadratic proper space-time line element is derived, proportional to Planck length-squared, and dependent on two contributions. The first is associated to the energy–time uncertainty, and the second depends on the Hubble function. The results are in agreement with space-time quantization on the expected length orders, according to quantum gravity theories, and within experimental constraints on putative LIV.

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AMELINO-CAMELIA, GIOVANNI. "KINEMATICAL SOLUTION OF THE UHE-COSMIC-RAY PUZZLE WITHOUT A PREFERRED CLASS OF INERTIAL OBSERVERS." International Journal of Modern Physics D 12, no. 07 (August 2003): 1211–26. http://dx.doi.org/10.1142/s0218271803003645.

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Among the possible explanations for the puzzling observations of cosmic rays above the GZK cutoff there is growing interest in the ones that represent kinematical solutions, based either on general formulations of particle physics with small violations of Lorentz symmetry or on a quantum-gravity-motivated scheme for the breakdown of Lorentz symmetry. An unappealing aspect of these cosmic-ray-puzzle solutions is that they require the existence of a preferred class of inertial observers. Here I propose a new kinematical solution of the cosmic-ray puzzle, which does not require the existence of a preferred class of inertial observers. My proposal is a new example of a type of relativistic theories, the so-called "doubly-special-relativity" theories, which have already been studied extensively over the last two years. The core ingredient of the proposal is a deformation of Lorentz transformations in which also the Planck scale Ep (in addition to the speed-of-light scale c) is described as an invariant. Just like the introduction of the invariant c requires a deformation of the Galileian transformations into the Lorentz transformations, the introduction of the invariant Ep requires a deformation of the Lorentz transformations, but there is no special class of inertial observers. The Pierre Auger Observatory and the GLAST space telescope should play a key role in future developments of these investigations. I also emphasize that the doubly-special-relativity theory here proposed, besides providing a solution for the cosmic-ray puzzle, is also the first doubly-special-relativity theory with a natural description of macroscopic bodies, and may find applications in the context of a recently-proposed dark-energy scenario.

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Polchinski, Joseph. "Comment on ‘Small Lorentz violations in quantum gravity: do they lead to unacceptably large effects?’." Classical and Quantum Gravity 29, no. 8 (March 22, 2012): 088001. http://dx.doi.org/10.1088/0264-9381/29/8/088001.

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Maccione, Luca, Stefano Liberati, and David M. Mattingly. "Violations of Lorentz invariance in the neutrino sector: an improved analysis of anomalous threshold constraints." Journal of Cosmology and Astroparticle Physics 2013, no. 03 (March 28, 2013): 039. http://dx.doi.org/10.1088/1475-7516/2013/03/039.

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AMELINO-CAMELIA, GIOVANNI, GIANLUCA MANDANICI, ANDREA PROCACCINI, and JERZY KOWALSKI-GLIKMAN. "PHENOMENOLOGY OF DOUBLY SPECIAL RELATIVITY." International Journal of Modern Physics A 20, no. 26 (October 20, 2005): 6007–37. http://dx.doi.org/10.1142/s0217751x05028569.

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Investigations of the possibility that some novel "quantum" properties of space–time might induce a Planck-scale modification of the energy/momentum dispersion relation focused at first on scenarios with Planck-scale violations of Lorentz symmetry, with an associated reduced n-parameter (n<6) rotation-boost symmetry group. More recently several studies have also considered the possibility of a "doubly special relativity," in which the modification of the dispersion relation emerges from a framework with both the Planck scale and the speed-of-light scale as characteristic scales of a 6-parameter group of rotation-boost symmetry transformations (a deformation of the Lorentz transformations). For the schemes with broken Lorentz symmetry at the Planck scale there is a large literature on the derivation of experimental limits. Here we show that the analysis of the experimental limits could be significantly different in a doubly-special-relativity framework. We find that the study of photon stability, synchrotron radiation, and threshold conditions for particle production in collision processes, the three contexts which are considered as most promising for constraining the broken-Lorentz-symmetry scenario, should not provide significant constraints on a doubly-special-relativity parameter space. However, certain types of analyses of gamma-ray bursts should be sensitive to the symmetry deformation. A key element of our study is an observation that removes a possible sign ambiguity for the doubly-special-relativity framework. This result also allows us to characterize more sharply the differences between the doubly-special-relativity framework and the framework of κ-Poincaré Hopf algebras, two frameworks which are often confused with each other in the literature.

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Antonelli, Vito, Lino Miramonti, and Marco Danilo Claudio Torri. "Phenomenological Effects of CPT and Lorentz Invariance Violation in Particle and Astroparticle Physics." Symmetry 12, no. 11 (November 3, 2020): 1821. http://dx.doi.org/10.3390/sym12111821.

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It is well known that a fundamental theorem of Quantum Field Theory (QFT) set in flat spacetime ensures the CPT invariance of the theory. This symmetry is strictly connected to the Lorentz covariance, and consequently to the fundamental structure of spacetime. Therefore it may be interesting to investigate the possibility of departure from this fundamental symmetry, since it can furnish a window to observe possible effects of a more fundamental quantum gravity theory in a “lower energy limit”. Moreover, in the past, the inquiry of symmetry violations provided a starting point for new physics discoveries. A useful physical framework for this kind of search is provided by astroparticle physics, thanks to the high energy involved and to the long path travelled by particles accelerated by an astrophysical object and then revealed on Earth. Astrophysical messengers are therefore very important probes for investigating this sector, involving high energy photons, charged particles, and neutrinos of cosmic origin. In addition, one can also study artificial neutrino beams, investigated at accelerator experiments. Here we discuss the state of art for all these topics and some interesting new proposals, both from a theoretical and phenomenological point of view.

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URRUTIA, LUIS. "QUANTUM GRAVITY CORRECTIONS TO PARTICLE INTERACTIONS." Modern Physics Letters A 17, no. 15n17 (June 7, 2002): 943–54. http://dx.doi.org/10.1142/s0217732302007648.

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An heuristic semiclassical procedure that incorporates quantum gravity induced corrections in the description of photons and spin 1/2 fermions is reviewed. Such modifications are calculated in the framework of loop quantum gravity and they arise from the granular structure of space at short distances. The resulting effective theories are described by power counting non-renormalizable actions which exhibit Lorentz violations at Planck length scale. The modified Maxwell an Dirac equations lead to corrections of the energy momentum relations for the corresponding particle at such scale. An action for the relativistic point particle exhibiting such modified dispersion relations is constructed and the first steps towards the study of a consistent coupling between these effective theories are presented.

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Halprin, A., and R. R. Volkas. "Closing the neutrinoless double beta decay window into violations of the equivalence principle and/or Lorentz invariance." Physics Letters B 459, no. 1-3 (July 1999): 183–85. http://dx.doi.org/10.1016/s0370-2693(99)00652-8.

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