Lorentz Violation Research Articles

Fermionic greybody factors and quasinormal modes of black holes in Kalb–Ramond gravity

In non-minimally coupled Kalb–Ramond (KR) fields, the vacuum expectation value (VEV) leads to spontaneous local Lorentz symmetry violation, resulting in static spherically symmetric solution. In this solution, fermionic greybody factors (GFs) and quasinormal modes (QNMs) are investigated. First, we study the wave dynamics of fermions using the Dirac and Rarita–Schwinger equations. We have derived the equations of effective potential for fermions with different spins. The fermionic GFs radiated by the black holes (BHs) are calculated using rigorous bounds as well as semi-analytic methods. The fermionic QNM of spin- 1/2 of the BHs in the KR gravity was analyzed using the sixth order WKB method. Furthermore, we discuss how Lorentz violating (LV) parameters impact GFs and QNMs. According to our results, the effective potential curve increases significantly when the LV parameter value γ is high. Thus, as the LV parameter γ increases, the bound of the GF and the QNM’s wave oscillation frequency will increase, while the decay rate will slow down.

Vacuum polarization in Yang-Mills theories with Lorentz violation

Vacuum polarization in Yang-Mills theories with Lorentz violation

Research on the noise characteristics of a closed-loop 87Rb atom comagnetometer

Spin-based comagnetometers have essential applications in studying new physical effects such as the fifth force, Lorentz violations, and spin-gravity interactions. In this paper, a transfer function model of the spin precession phase (frequency) is derived to analyze the comagnetometer's noise mechanism. The theory combined with experiments reveals that the output frequency noise of the spin oscillator above 5 Hz is mainly phase noise from the phase-locked loop. The noise below 5 Hz is mainly from the biased magnetic field noise. When building a comagnetometer using two spin oscillators, the symmetry of the spin oscillator is significant. When the intrinsic physical parameters cannot be symmetrical, the comagnetometer's common-mode suppression capability to magnetic field fluctuations can be enhanced by optimizing the control parameters. In addition, the closed-loop control of Bz can significantly weaken the effect of system asymmetry in the low-frequency band. Finally, when considering the comagnetometer system in nuclear magnetic resonance gyroscopes, a trade-off between the bandwidth and sensitivity can be achieved using theory. This paper is an excellent reference for both the research and application of comagnetometers.

New Limits on Exotic Spin-Dependent Interactions at Astronomical Distances.

Exotic spin-dependent interactions involving new light particles address key questions in modern physics. Interactions between polarized neutrons (n) and unpolarized nucleons (N) occur in three forms: g_{S}^{N}g_{P}^{n}σ·r, g_{V}^{N}g_{A}^{n}σ·v, and g_{A}^{N}g_{A}^{n}σ·v×r, where σ is the spin and g's are the corresponding coupling constants for scalar, pseudoscalar, vector, and axial-vector vertexes. If such interactions exist, the Sun and Moon could induce sidereal variations of effective fields in laboratories. By analyzing existing data from laboratory measurements on Lorentz and CPT violation, we derive new experimental upper limits on these exotic spin-dependent interactions at astronomical ranges. Our limits on g_{S}^{N}g_{P}^{n} surpass the previous combined astrophysical-laboratory limits, setting the most stringent experimental constraints to date. We also report new constraints on vector-axial-vector and axial-axial-vector interactions at astronomical scales, with vector-axial-vector limits improved by ∼12 orders of magnitude. We extend our analysis to Hari Dass interactions and obtain new constraints.

Ultrahigh-Sensitivity Bragg Atom Gravimeter and its Application in Testing Lorentz Violation

Ultrahigh-Sensitivity Bragg Atom Gravimeter and its Application in Testing Lorentz Violation

Gaussian beam propagation in a Lorentz-violating vacuum in the presence of a semi-transparent mirror

In this paper we study the propagation of structured optical scalar beams in a Lorentz-violating (LV) vacuum parametrized by a constant 4-vector u μ and in the presence of a semi-transparent mirror. The two bosonic degrees of freedom of the electromagnetic field can be described by a LV extension of the massless scalar field theory, whose LV part is characterized by the term (u · ∂ϕ)2. The mirror at a surface Σ is modelled by a delta-type potential in the Lagrange density for the LV scalar field, i.e. λ δ(Σ)ϕ 2, where the parameter λ controls the degree of transparency of the mirror. Using Green’s function techniques, we investigate the propagation of a Gaussian beam in the presence of a mirror which is perpendicular to the propagation direction and for two particular choices of the background 4-vector: parallel and perpendicular to the propagation direction. To quantify the Lorentz-violating effects we introduce the fidelity as a measurement of the closeness of the propagated field distribution with respect to that in the conventional vacuum. In the absence of the mirror (λ = 0) the fidelity is found to be close to one, and hence LV effects are quite small. However in the presence of the mirror, there are regions where the fidelity drops to zero, thus implying that LV effects could be clearly differentiated from the propagation in vacuum. Within the paraxial approximation we determine analytically the LV effects upon the Rayleigh range, the radius of the beam, the Gouy phase and the radius of curvature of the wavefronts. We discuss possible scenarios where our results could apply, by using optically transparent multiferroic materials, which offer unprecedented opportunities to tailor structured beam propagation, as well as to simulate an LV vacuum.

Fermions tunneling of Kerr–Newman–de Sitter black hole in Lorentz violation theory

In this paper, the tunneling of fermions near the event horizon of Kerr–Newman–de Sitter (KNdS) black hole is investigated in frame dragging coordinate systems, Eddington coordinate system and Painleve coordinate system by using Dirac equation with Lorentz violation theory, Feynman prescription and WKB approximation. The Hawking temperature, heat capacity and change in black hole entropy of the black hole are modified due to the presence of Lorentz violation theory. The modified Hawking temperatures, heat capacities and change in black hole entropies at the event horizon of KNdS black hole would increase or decrease depending upon the choices of ether like vectors [Formula: see text]. In the absence of Lorentz violation theory, the original Hawking temperature, entropy and heat capacity are recovered.

Single-particle quantum mechanics of the free Klein–Gordon equation with Lorentz violation

Single-particle quantum mechanics of the free Klein–Gordon equation with Lorentz violation

Modified Hawking temperature and entropy of Kerr–de Sitter black hole in Lorentz violation theory

In this paper, we discuss the tunneling of scalar particles near the event horizon of stationary and nonstationary Kerr–de Sitter black hole using Lorentz violation theory in curved space time. The modified form of Hamilton–Jacobi equation is derived from the Klein–Gordon equation by applying Lorentz violation theory. The Hawking temperatures derived from stationary and nonstationary Kerr–de Sitter black holes are modified due to Lorentz violation theory. It is noted that the change in Bekenstein–Hawking entropy and modified Hawking temperatures of stationary and nonstationary Kerr–de Sitter black hole not only depends on the black hole parameters but also on ether-like vectors [Formula: see text].

Gravitational wave constraints on nonbirefringent dispersions of gravitational waves due to Lorentz violations with GWTC-3 events

The standard model extension (SME) is an effective field theory framework that can be used to study the possible violations of Lorentz symmetry in the gravitational interaction. In the SME's gauge invariant linearized gravity sector, the dispersion relation of GWs is modified, resulting in anisotropy, birefringence, and dispersion effects in the propagation of GWs. In this paper, we mainly focus on the non-birefringent and anisotropic dispersion relation in the propagation of GWs due to the violation of Lorentz symmetry. With the modified dispersion relation, we calculate the corresponding modified waveform of GWs generated by the coalescence of compact binaries. We consider the effects from the operators with the lowest mass dimension $d=6$ in the gauge invariant linearized gravity sector of the SME which are expected to have the dominant Lorentz-violating effect on the propagation of GWs. For this case, the Lorentz-violating effects are presented by 25 coefficients and we constrain them independently by the ``maximal-reach" approach. We use 90 high-confidence GW events in the GWTC-3 catalog and use {\tt Bilby}, an open source software, and {\tt Dynest}, a nested sampling package, to perform parameter estimation with the modified waveform. We do not find any evidence of Lorentz violation in the GWs data and give a $90\%$ confidence interval for each Lorentz violating coefficient.

Lorentz violation emergence in a superconductivity phase transition scenario

In this letter, we use a condensation of topological defects mechanism to show how a Lorentz-violating (LV) term can emerge. The approach used here was originally developed to describe phase transitions due to a vortice proliferation in systems such as superconductors. First, as a consequence of our approach, we obtain a Podolsky-like LV term as a result of this work. Second, a condensation of topological defects in the theory restores the original Lorentz symmetric phase of the theory. The approach presented here can be seen as an early description of a mechanism to describe a phase transition between a Lorentz symmetric phase and a non-symmetric one. Besides the usage of this mechanism to show how LV terms can emerge, we also show how to extend the condensation mechanism to scalar theories. The condensation mechanism was originally designed for gauge theories. As a result, our scalar extension recovers the Ginzburg-Landau (GL) description of both regular and non-local superconductors. The GL description, in our approach, arises as a consequence of the condensation of topological defects.

Perturbative aspects of CPT -even Lorentz-violating scalar chromodynamics

In this work, we formulate the theory of Lorentz-violating scalar Quantum Chromodynamics with an arbitrary non-Abelian gauge group. This theory belongs to the class of models encompassed by the standard model extension framework. At the lowest order in the theory's Lorentz violation parameters, we calculate the divergent quantum corrections, including the renormalization group $\beta$-functions of the theory. The Lorentz-violating sector is shown to be scale invariant if there is a particular relation between the couplings.

Thermodynamics of a quantum ring modified by Lorentz violation

In this work, we investigate the consequences of Lorentz-violating terms in the thermodynamic properties of a 1-dimensional quantum ring. In particular, we use the ensemble theory to obtain our results of interest. The thermodynamic functions as well as the spin currents are calculated as a function of the temperature. We observe that parameter ξ, which triggers the Lorentz symmetry breaking, plays a major role in low temperature regime. Finally, depending on the configuration of the system, electrons can rotate in two different directions: clockwise and counterclockwise.

Constraining the Lorentz-violating bumblebee vector field with big bang nucleosynthesis and gravitational baryogenesis

By assuming the cosmological principle i.e., an isotropic and homogeneous universe, we consider the cosmology of a vector-tensor theory of gravitation known as the bumblebee model. In this model a single Lorentz-violating timelike vector field with a nonzero vacuum expectation value (VEV) couples to the Ricci tensor and scalar, as well. Taking the ansatz B(t)sim t^beta for the time evolution of the vector field, where beta is a free parameter, we derive the relevant dynamic equations of the Universe. In particular, by employing observational data coming from the Big Bang Nucleosynthesis (BBN) and the matter–antimatter asymmetry in the baryogenesis era, we impose some constraints on the VEV of the bumblebee timelike vector field i.e., xi b^2, and the exponent parameter beta . The former and the latter limit the size of Lorentz violation, and the rate of the time evolution of the background Lorentz-violating bumblebee field, respectively.

Discriminating between Lorentz violation and non-standard interactions using core-passing atmospheric neutrinos at INO-ICAL

Precision measurements of neutrino oscillation parameters have provided a tremendous boost to the search for sub-leading effects due to several beyond the Standard Model scenarios in neutrino oscillation experiments. Among these, two of the well-studied scenarios are Lorentz violation (LV) and non-standard interactions (NSI), both of which can affect neutrino oscillations significantly. We point out that, at a long-baseline experiment where the neutrino oscillation probabilities can be well-approximated by using the line-averaged constant matter density, the effects of these two scenarios can mimic each other. This would allow the limits obtained at such an experiment on one of the above scenarios to be directly translated to the limits on the other scenario. However, for the same reason, it would be difficult to distinguish between LV and NSI at a long-baseline experiment. We show that the observations of atmospheric neutrinos, which travel a wide range of baselines and may encounter sharp density changes at the core-mantle boundary, can break this degeneracy. We observe that identifying neutrinos and antineutrinos separately, as can be done at INO-ICAL, can enhance the capability of atmospheric neutrino experiments to discriminate between these two new-physics scenarios.

Trajectories of astroparticles in pseudo-Finsler spacetime with the most general modified dispersion

Finsler geometry is a natural and fundamental generalization of Riemann geometry, and is a tool to research Lorentz invariance violation. We find the connection between the most general modified dispersion relation and a pseudo-Finsler structure, and then we calculate the arrival time delay of astroparticles with different modified dispersion relations in the framework of Finsler geometry. The result suggests that the time delay is irrelevant with the exact form of the modified dispersion relation. If the modified term becomes 0 when E=p, there is no arrival time difference, otherwise the time delays only depend on the Lorentz violation scale and the order at which the Lorentz invariance breaks.

Lorentz Violation in Finsler Geometry

Lorentz invariance is one of the foundations of modern physics; however, Lorentz violation may happen from the perspective of quantum gravity, and plenty of studies on Lorentz violation have arisen in recent years. As a good tool to explore Lorentz violation, Finsler geometry is a natural and fundamental generalization of Riemann geometry. The Finsler structure depends on both coordinates and velocities. Here, we simply introduce the mathematics of Finsler geometry. We review the connection between modified dispersion relations and Finsler geometries and discuss the physical influence from Finsler geometry. We review the connection between Finsler geometries and theories of Lorentz violation, such as the doubly special relativity, the standard-model extension, and the very special relativity.

Scalar Casimir effects in a Lorentz violation scenario induced by the presence of constant vectors

In this work, we consider a theoretical model that presents a violation of Lorentz symmetry in the approach of quantum field theory. The theoretical model adopted consists of a real massive scalar quantum field confined in the region between two large parallel plates. The violation of Lorentz symmetry is introduced by a CPT-even, aether-like approach, considering a direct coupling between the derivative of the scalar field with two orthogonal constant vectors. The main objective of this paper is to analyze the modification of the Casimir energy and pressure caused by the anisotropy of space–time as a consequence of these couplings. The confinement of the scalar quantum field between the plates is implemented by imposing boundary conditions on them.

New bound on Lorentz violation based on the absence of vacuum Cherenkov radiation in ultrahigh energy air showers

In extensive air showers induced by ultra-high energy (UHE) cosmic rays, secondary particles are produced with energies far above those accessible by other means. These extreme energies can be used to search for new physics. We study the effects of isotropic, nonbirefringent Lorentz violation in the photon sector. In case of a photon velocity smaller than the maximum attainable velocity of standard Dirac fermions, vacuum Cherenkov radiation becomes possible. Implementing this Lorentz-violating effect in air shower simulations, a significant reduction of the calculated average atmospheric depth of the shower maximum $\left<X_\text{max}\right>$ is obtained. Based on $\left<X_\text{max}\right>$ and its shower-to-shower fluctuations $\sigma(X_\text{max})$, a new bound on Lorentz violation is derived which improves the previous one by a factor of 2. This is the first such bound based on the absence of vacuum Cherenkov radiation from fundamental particles (electrons and positrons) in air showers. Options for further improvements are discussed.

Lorentz and CPT breaking in gamma-ray burst neutrinos from string theory

Previous studies on high-energy gamma-ray burst neutrinos from IceCube suggest a neutrino speed variation at the Lorentz violation (LV) scale of ~6.4 × 1017 GeV, with opposite velocity variances between neutrinos and antineutrinos. Within a spacetime foam model, inspired by string theory, we develop an approach to describe the suggested neutrino/antineutrino propagation properties with both Lorentz invariance and CPT symmetry breaking. A threshold analysis on the bremsstrahlung of electron-positron pair (ν → νee+) for the superluminal (anti)neutrino is performed. We find that, due to the energy violation caused by the quantum foam, such reaction may be restricted to occur at sufficient high energies and could even be kinematically forbidden. Constraints on neutrino LV from vacuum ee+ pair emission are naturally avoided. Future experiments are appealed to test further the CPT violation of cosmic neutrinos and/or neutrino superluminality.