Lorentz-violating Parameters Research Articles

Quasinormal modes of bumblebee wormhole

In this work, we calculate the quasinormal frequencies from a bumblebee traversable wormhole. The bumblebee wormhole model is based on the bumblebee gravity, which exhibits a spontaneous Lorentz symmetry breaking. Supporting by the Lorentz violation parameter , this model allows for the fulfillment of the flare-out and energy conditions, granted non-exotic matter to the wormhole. We analyze the parameters of the bumblebee wormhole in order to obtain a Regge–Wheeler’s equation with a bell-shaped potential. We obtain the quasinormal modes (QNMs) via the WKB approximation method for both scalar and gravitational perturbations. The time domain has decreasing oscillation (damping) profiles for the bumblebee wormhole.

Parameter estimation for a Lorentz invariance violation

We employ techniques from quantum estimation theory (QET) to estimate the Lorentz violation parameters in the (1+3)-dimensional flat spacetime. We obtain and discuss the expression of the quantum Fisher information (QFI) in terms of the Lorentz violation parameter [Formula: see text] and the momentum [Formula: see text] of the created particles. We show that the maximum QFI is achieved for a specific momentum [Formula: see text]. We also find that the optimal precision of estimation of the Lorentz violation parameter is obtained near the Planck scale.

Final results of the Aurora experiment to study 2β decay of Cd116 with enriched Cd116WO4 crystal scintillators

The double-beta decay of $^{116}$Cd has been investigated with the help of radiopure enriched $^{116}$CdWO$_4$ crystal scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory. The half-life of $^{116}$Cd relatively to the $2\nu2\beta$ decay to the ground state of $^{116}$Sn was measured with the highest up-to-date accuracy as $T_{1/2}=(2.63^{+0.11}_{-0.12})\times10^{19}$ yr. A new improved limit on the 0$\nu$2$\beta$ decay of $^{116}$Cd to the ground state of $^{116}$Sn was set as $T_{1/2}\geq 2.2 \times 10^{23}$ yr at 90\% C.L., which is the most stringent known restriction for this isotope. It corresponds to the effective Majorana neutrino mass limit in the range $\langle m_\nu\rangle\le(1.0-1.7)$ eV, depending on the nuclear matrix elements used in the estimations. New improved half-life limits for the 0$\nu$2$\beta$ decay with majoron(s) emission, Lorentz-violating $2\nu2\beta$ decay and $2\beta$ transitions to excited states of $^{116}$Sn were set at the level of $T_{1/2}\geq 10^{20}-10^{22}$ yr. New limits for the hypothetical lepton-number violating parameters (right-handed currents admixtures in weak interaction, the effective majoron-neutrino coupling constants, R-parity violating parameter, Lorentz-violating parameter, heavy neutrino mass) were set.

Lorentz-violating dimension-five operator contribution to the black body radiation

We investigate the thermodynamics of a photon gas in an effective field theory model that describes Lorentz violations through dimension-five operators and Horava–Lifshitz theory. We explore the electrodynamics of the model which includes higher order derivatives in the Lagrangian that can modify the dispersion relation for the propagation of the photons. We shall focus on the deformed black body radiation spectrum and modified Stefan–Boltzmann law to address the allowed bounds on the Lorentz-violating parameter.

Higher-order one-loop contributions in Lorentz-breaking QED

We calculate higher-order quantum contributions in different Lorentz-violating parameters to the gauge sector of the extended QED. As a result of this one-loop calculation, some terms which do not produce corrections of first order in Lorentz-breaking parameters, contribute with nontrivial gauge-invariant quantum corrections of second order in these parameters.

One-loop correction to the photon velocity in Lorentz-violating QED

We calculate a finite momentum-dependent part of the photon polarization operator in a simple model of Lorentz-violating quantum electrodynamics nonperturbatively at all orders of Lorentz-violating parameters. We sum one-particle reducible diagrams into the modified photon propagator, and determine the physical photon dispersion relation as the location of its pole. The photon dispersion relation, as well as its group velocity, acquires the one-loop momentum-dependent radiative correction. We constrain the Lorentz-violating parameters for heavy charged fermions (muon, $\tau$-lepton, top-quark) from the photon timing observations.

Lorentz-violating neutral-pion decays in isotropic modified Maxwell theory

We consider an extension of the Standard Model with isotropic non-birefringent Lorentz violation in the photon sector and restrict the discussion to the case of a “fast” photon with a phase velocity larger than the maximum attainable velocity of the quarks and leptons. With our conventions, this case corresponds to a negative Lorentz-violating parameter [Formula: see text] in the action. The decay rate of a neutral pion into two nonstandard photons is calculated as a function of the 3-momentum of the initial pion and the negative Lorentz-violating parameter [Formula: see text] of the final photons.

Lorentz violation parameters and noncommutative scale

We consider the noncommutative Standard Model that contains Lorentz symmetry violation as a subset of the Standard Model extension. We introduce a constant electromagnetic field as a background to derive mutual relations between the free parameters of both theories. As the Lorentz violation parameters of the Standard Model extension are extensively explored in different experiments and many stringent bounds on these parameters are available, we can find new bounds on the scale of noncommutativity of the order of a few to tens of teraelectron volts.

Cherenkov-like emission of Z bosons

We study CPT and Lorentz violation in the electroweak gauge sector of the Standard Model in the context of the Standard-Model Extension (SME). In particular, we show that any non-zero value of a certain relevant Lorentz violation parameter that is thus far unbounded by experiment would imply that for sufficiently large energies one of the helicity modes of the Z boson should propagate with spacelike four-momentum and become stable against decay in vacuum. In this scenario, Cherenkov-like radiation of Z bosons by ultra-high-energy cosmic-ray protons becomes possible. We deduce a bound on the Lorentz violation parameter from the observational data on ultra-high energy cosmic rays.

Gluonic Lorentz violation and chiral perturbation theory

By applying chiral-perturbation-theory methods to the QCD sector of the Lorentz-violating Standard-Model Extension, we investigate Lorentz violation in the strong interactions. In particular, we consider the CPT-even pure-gluon operator of the minimal Standard-Model Extension. We construct the lowest-order chiral effective Lagrangian for three as well as two light quark flavors. We develop the power-counting rules and construct the heavy-baryon chiral-perturbation-theory Lagrangian, which we use to calculate Lorentz-violating contributions to the nucleon self energy. Using the constructed effective operators, we derive the first stringent limits on many of the components of the relevant Lorentz-violating parameter. We also obtain the Lorentz-violating nucleon-nucleon potential. We suggest that this potential may be used to obtain new limits from atomic-clock or deuteron storage-ring experiments.

Tree-level equivalence between a Lorentz-violating extension of QED and its dual model in electron\u2013electron scattering

S-matrix amplitudes for the electron–electron scattering are calculated in order to verify the physical equivalence between two Lorentz-breaking dual models. We begin with an extended Quantum Electrodynamics which incorporates CPT-even Lorentz-violating kinetic and mass terms. Then, in a process of gauge embedding, its gauge-invariant dual model is obtained. The physical equivalence of the two models is established at tree level in the electron–electron scattering and the unpolarized cross section is calculated up to second order in the Lorentz-violating parameter.

A nonlinear dynamics for the scalar field in Randers spacetime

Abstract We investigate the properties of a real scalar field in the Finslerian Randers spacetime, where the local Lorentz violation is driven by a geometrical background vector. We propose a dynamics for the scalar field by a minimal coupling of the scalar field and the Finsler metric. The coupling is intrinsically defined on the Randers spacetime, and it leads to a non-canonical kinetic term for the scalar field. The nonlinear dynamics can be split into a linear and nonlinear regimes, which depend perturbatively on the even and odd powers of the Lorentz-violating parameter, respectively. We analyze the plane-waves solutions and the modified dispersion relations, and it turns out that the spectrum is free of tachyons up to second-order.

Neutrino Pair Cerenkov Radiation for Tachyonic Neutrinos

The emission of a charged light lepton pair by a superluminal neutrino has been identified as a major factor in the energy loss of highly energetic neutrinos. The observation of PeV neutrinos by IceCube implies their stability against lepton pair Cerenkov radiation. Under the assumption of a Lorentz-violating dispersion relation for highly energetic superluminal neutrinos, one may thus constrain the Lorentz-violating parameters. A kinematically different situation arises when one assumes a Lorentz-covariant, space-like dispersion relation for hypothetical tachyonic neutrinos, as an alternative to Lorentz-violating theories. We here discuss a hitherto neglected decay process, where a highly energetic tachyonic neutrino may emit other (space-like, tachyonic) neutrino pairs. We find that the space-like dispersion relation implies the absence of a q2 threshold for the production of a tachyonic neutrino-antineutrino pair, thus leading to the dominant additional energy loss mechanism for an oncoming tachyonic neutrino in the medium-energy domain. Surprisingly, the small absolute values of the decay rate and energy loss rate in the tachyonic model imply that these models, in contrast to the Lorentz-violating theories, are not pressured by the cosmic PeV neutrinos registered by the IceCube collaboration.

Gupta-Bleuler’s quantization of a parity-odd CPT -even electrodynamics of the standard model extension

Following a successfully quantization scheme previously developed in Ref. [R. Casana, M. M. Ferreira, Jr., and F. E. P. dos Santos, Phys. Rev. D 90, 105025 (2014).] for a parity-even gauge sector of the SME, we have established the Gupta-Bleuler quantization of a parity-odd and $CPT$-even electrodynamics of the standard model extension (SME) without the need for a small photon mass regulator. Keeping the photons massless, we have adopted the gauge-fixing condition: $G({A}_{\ensuremath{\mu}})=({\ensuremath{\partial}}_{0}+{\ensuremath{\kappa}}^{0j}{\ensuremath{\partial}}_{j})({A}_{0}+{\ensuremath{\kappa}}^{0k}{A}_{k})+{\ensuremath{\partial}}_{i}{A}^{i}$. The four polarization vectors of the gauge field are exactly determined by solving an eigenvalue problem, exhibiting birefringent second-order contributions in the Lorentz-violating parameters. They allow us to express the Hamiltonian in terms of annihilation and creation operators whose positivity is guaranteed by imposing a weak Gupta-Bleuler constraint, defining the physical states. Consequently, we compute the field commutation relation that has been expressed in terms of Pauli-Jordan functions modified by Lorentz violation whose light-cone structures have allowed us to analyze the microcausality issue.

Changes in extensive air showers from isotropic Lorentz violation in the photon sector

We consider a theory with isotropic nonbirefringent Lorentz violation in the photon sector and explore the effects on the development of the electromagnetic component of extensive air showers in the Earth atmosphere. Specifically, we consider the case of a "fast" photon with a phase velocity larger than the maximum attainable velocity of a massive Dirac fermion (this case corresponds to a negative Lorentz-violating parameter $\kappa$ in the action). Shower photons with above-threshold energies decay promptly into electron-positron pairs, instead of decaying by the conventional production of electron-positron pairs in the background fields of atomic nuclei. This rapid production of charged leptons accelerates the shower development, decreasing the atmospheric depth of the shower maximum ($X_\text{max}$) by an amount which could be measured by cosmic-ray observatories. Precise measurements of $X_\text{max}$ could then improve existing limits on the negative Lorentz-violating parameter $\kappa$ by several orders of magnitude.

Topological self-dual configurations in a Maxwell–Higgs model with a CPT-odd and Lorentz-violating nonminimal coupling

We have studied the existence of topological self-dual configurations in a nonminimal CPT-odd and Lorentz-violating (LV) Maxwell–Higgs model, where the LV interaction is introduced by modifying the minimal covariant derivative. The Bogomol’nyi–Prasad–Sommerfield formalism has been implemented, revealing that the scalar self-interaction implying self-dual equations contains a derivative coupling. The CPT-odd self-dual equations describe electrically neutral configurations with finite total energy proportional to the total magnetic flux, which differ from the charged solutions of other CPT-odd and LV models previously studied. In particular, we have investigated the axially symmetrical self-dual vortex solutions altered by the LV parameter. For large distances, the profiles possess general behavior similar to the vortices of Abrikosov–Nielsen–Olesen. However, within the vortex core, the profiles of the magnetic field and energy can differ substantially from ones of the Maxwell–Higgs model depending if the LV parameter is negative or positive.

Kondo effect from a Lorentz-violating domain wall description of superconductivity

We extend recent results on domain wall description of superconductivity in an Abelian Higgs model by introducing a particular Lorentz-violating term. The temperature of the system is interpreted through the fact that the soliton following accelerating orbits is a Rindler observer experiencing a thermal bath. We show that this term can be associated with the {\sl Kondo effect}, that is, the Lorentz-violating parameter is closely related to the concentration of magnetic impurities living on a superconducting domain wall. We also found that the critical temperature decreasing with the impurity concentration as a non single-valued function, for the case $T_K < T_{c0}$, develops a negative curvature and presents deviations from the Abrikosov and Gor'kov theory, a phenomenon already supported by experimental evidence.

On the anomalies in Lorentz-breaking theories

In this paper, we discuss the chiral anomaly in a Lorentz-breaking extension of QED which, besides the common terms that are present in the Standard Model Extension, includes some dimension-five nonminimal couplings. We find, using the Fujikawa formalism, that these nonminimal couplings induce new terms in the anomaly which depend on the Lorentz-violating parameters. Perturbative calculations are also carried out in order to investigate whether new ambiguous Carroll–Field–Jackiw terms are induced in the effective action.

Topological self-dual configurations in a Lorentz-violating gaugedO(3)sigma model

We have studied the existence of topological Bogomol'nyi-Prasad-Sommerfield or self-dual configurations in a Lorentz-violating gauged $O(3)$ nonlinear sigma model, where $CPT$-even Lorentz-violating (LV) terms were introduced in both the gauge and $\sigma $% -field sectors. As happens in the usual gauged $\sigma $ model, purely magnetic self-dual configurations are allowed, maintaining some qualitative features of the standard ones. In a more involved configuration, Lorentz violation provides new self-dual magnetic solutions carrying an electric field but a null total electric charge. In both cases, the total energy of the self-dual configurations turns out to be proportional to the topological charge of the model and to the LV parameters introduced in the $% \sigma $ sector. It is shown that the LV terms yield magnetic flux reversion as well.

Parton-model calculation of a nonstandard decay process in isotropic modified Maxwell theory

We have performed a calculation in the parton-model approximation of a nonstandard decay process in isotropic modified Maxwell theory coupled to standard Dirac theory, with a single Lorentz-violating parameter $\kappa$ in the photonic sector. Previous calculations of this process (vacuum Cherenkov radiation by a proton for the theory with $\kappa>0$) were performed for pointlike particles, and an upper bound on $\kappa$ at the $10^{-19}$ level was obtained from experimental data on ultra-high-energy cosmic rays. The parton-model results change the decay rate by about an order of magnitude but give the same upper bound on $\kappa$ because the threshold energy is unchanged. The previous point-particle calculation of photon decay into an electron-positron pair for the theory with $\kappa<0$ remains valid, and experimental results on cosmic gamma rays provide a lower bound on $\kappa$ at the $-10^{-15}$ level.