Lorentz Symmetry Violation Research Articles

Wave packets in QFT: Leading order width corrections to decay rates and clock behavior under Lorentz boosts

Decay rates in quantum field theory (QFT) are typically calculated assuming the particles are represented by momentum eigenstates (i.e., plane waves). However, strictly speaking, localized free particles should be represented by wave packets. This yields width corrections to the decay rate and to the clock behavior under Lorentz boosts. We calculate the decay rate of a particle of mass $M$ modeled as a Gaussian wave packet of width $a$ and centered at zero momentum. We find the decay rate to be ${\mathrm{\ensuremath{\Gamma}}}_{0}[1\ensuremath{-}\frac{3{a}^{2}}{4{M}^{2}}+\mathcal{O}(\frac{{a}^{4}}{{M}^{4}})]$, where ${\mathrm{\ensuremath{\Gamma}}}_{0}$ is the decay rate of the particle at rest treated as a plane wave. The leading correction is then of order $\frac{{a}^{2}}{{M}^{2}}$. We then perform a Lorentz boost of velocity $v$ on the above Gaussian and find that its decay rate does not decrease exactly by the Lorentz factor $\sqrt{1\ensuremath{-}{v}^{2}}$. There is a correction of order $\frac{{a}^{2}{v}^{2}}{{M}^{2}}$. Therefore, the decaying wave packet does not act exactly like a typical clock under Lorentz boosts, and we refer to it is a ``WP clock'' (wave packet clock). A WP clock does not move with a single velocity relative to an observer but has a spread in velocities (more specifically, a spread in momenta). Nonetheless, it is best viewed as a single clock as the wave packet represents a one-particle state in QFT. WP clocks do not violate Lorentz symmetry and are not based on new physics; they are a consequence of the combined requirements of special relativity, quantum mechanics, and localized free particles.

Lorentz Symmetry and High-Energy Neutrino Astronomy

The search of the violation of Lorentz symmetry, or Lorentz violation (LV), is an active research field. The effects of LV are expected to be very small, and special systems are often used to search it. High-energy astrophysical neutrinos offer a unique system to search signatures of LV, due to the three factors: high neutrino energy, long propagation distance, and the presence of quantum mechanical interference. In this brief review, we introduce tests of LV and summarize existing searches of LV, using atmospheric and astrophysical neutrinos.

Klein-Gordon oscillator under a linear central potential induced by Lorentz symmetry violation

The Klein-Gordon oscillator under Lorentz symmetry violation determined by the tensor out of the Standard Model Extension (SME) is analyzed. We introduce angular frequency of the oscillator with a Klein-Gordon particle by replacing the momentum vector in the wave equation. We choose the scenario of Lorentz symmetry violation with the field configuration of a constant magnetic field along the z-direction and a cylindrical electric field along the radial direction. We then solved the wave equation and obtained the bound state solutions of the modified Klein-Gordon oscillator. We see that the angular frequency of oscillator depends on the quantum numbers of the system which shows a quantum effect and on Lorentz symmetry breaking parameters.

Searching for New Physics in two-neutrino double beta decay with CUPID

In the past few years, attention has been drawn to the fact that a precision analysis of two-neutrino double beta decay (2υββ) allows the study of interesting physics cases like the emission of Majoron bosons and possible Lorentz symmetry violation. These processes modify the summed-energy distribution of the two electrons emitted in 2υββ. CUPID is a next-generation experiment aiming to exploit 100Mo-enriched scintillating Li2MoO4 crystals, operating as cryogenic calorimeters. Given the relatively fast half-life of 100Mo 2υββ and the large exposure that can be reached by CUPID, we expect to measure with very high precision the 100Mo 2υββ spectrum shape, reaching great sensitivities in the search for distortions induced by the physics beyond the Standard Model. In this contribution, we present the CUPID exclusion sensitivity for such New Physics processes, as well as the preliminary projected background of CUPID.

Lorentz-symmetry violation in the electroweak sector: Scattering processes in future e+ e− colliders

We study CPT-odd non-minimal Lorentz-symmetry violating couplings in the electroweak sector modifying the interactions between leptons, gauge mediators and the Higgs boson. The tree-level (differential) cross sections for three important electroweak processes are discussed: e+e−→ZH, e+e−→ZZ and γγ→W+W−. By considering next-generation e+e− colliders reaching center-of-mass energies at the TeV scale and the estimated improved precision for the measurements of the respective cross sections, we are able to project upper bounds on the purely time-like background 4-vector as strict as ≲10−5GeV−1, in agreement with previous work on similar Lorentz-violating couplings.

Effects of Lorentz symmetry violation on a relativistic scalar particle in quantum systems

In this paper, the relativistic quantum dynamics of a scalar particle under the effect of Lorentz symmetry violation determined by a tensor out of the Standard Model Extension is investigated. We see that the bound-state solutions of the modified Klein-Gordon equation can be obtained, and the spectrum of energy and the wave function depends on the Lorentz symmetry breaking parameters.

Effects of a harmonic-type potential on a scalar field in a background of CPT-odd Lorentz symmetry violation

Effects of a harmonic-type potential on a scalar field in a background of CPT-odd Lorentz symmetry violation

Bumblebee field as a source of cosmological anisotropies

In this work, a bumblebee field is adopted in order to generate cosmological anisotropies. For that purpose, weassume a Bianchi I cosmology, as the background geometry, and a bumblebee field coupled to it.Bumblebee models are examples of a mechanism for the Lorentz symmetry violation byassuming a nonzero vacuum expectation value for the bumblebee field. When coupled tothe Bianchi I geometry, which is not in agreement with a cosmological principle, the bumblebee fieldplays the role of a source of anisotropies and produces a preferred axis. Thus, a fraction of the cosmic anisotropieswould come from the Lorentz symmetry violation.In the last part of the article, we try to assume an upper bound on the bumblebee field usingthe quadrupole and octopole moments of the cosmic microwave background radiation.

Ultrahigh-energy photons from LHAASO as probes of Lorentz symmetry violations

The Large High Altitude Air Shower Observatory (LHAASO) is one of the most sensitive gamma-ray detector arrays currently operating at TeV and PeV energies. Recently the LHAASO experiment detected ultra-high-energy (UHE; ${E}_{\ensuremath{\gamma}}\ensuremath{\gtrsim}100\text{ }\text{ }\mathrm{TeV}$) photon emissions up to 1.4 PeV from twelve astrophysical gamma-ray sources. We point out that the detection of cosmic photons at such energies can constrain the photon self-decay motivated by superluminal Lorentz symmetry violation (LV) to a higher level, thus can put strong constraints to certain LV frameworks. Meanwhile, we suggest that the current observation of the PeV-scale photon with LHAASO may provide hints to permit a subluminal type of Lorentz violation in the proximity of the Planckian regime, and may be compatible with the light speed variation at the scale of $3.6\ifmmode\times\else\texttimes\fi{}{10}^{17}\text{ }\text{ }\mathrm{GeV}$ recently suggested from gamma-ray burst (GRB) time delays. We further propose detecting PeV photons coming from extragalactic sources with future experiments, based on LV-induced threshold anomalies of ${e}^{+}{e}^{\ensuremath{-}}$ pair-production, as a crucial test of subluminal Lorentz violation. We comment that these observations are consistent with a D-brane/string-inspired quantum-gravity framework, the space-time foam model.

Non-Hermitian topological phase transitions in superlattices and the optical Dirac equation.

Optical superlattices with sublattice symmetry subjected to a synthetic imaginary gauge field undergo a topological phase transition in the Bloch energy spectrum, characterized by the change of a spectral winding number. For a narrow gap, the phase transition is of universal form and described by a non-Hermitian Dirac equation with Lorentz-symmetry violation. A simple photonic system displaying such a phase transition is discussed, which is based on light coupling in co-propagating gratings.

Lorentz symmetry violation and beyond semiclassical theory in the curved space–time of the arbitrarily dimensional Reissner–Nordström black hole

The quantum tunneling radiation of arbitrarily dimensional Reissner–Nordström black hole is corrected by beyond semiclassical theory and Lorentz symmetry violation theory, resulting in new expressions for the tunneling rate of scalar particles and the Hawking temperature at the horizon of the black hole. The physical significance of our results and the thermodynamic evolution characteristics of the black hole are also discussed.

Lorentz symmetry violation and accurate correction of bosons Hawking tunneling radiation for a stationary axisymmetric black hole

We study the characteristics of the quantum tunneling radiation of scalar bosons in the stationary Kerr-anti-de Sitter black hole based on Lorentz symmetry violation theory. First, the Klein-Gordon equation and Hamilton-Jacobi equation of bosons that are corrected by Lorentz symmetry violation theory in curved space-time are obtained. After solving the corrected dynamic equation of bosons, it is shown that the Lorentz-violating theory has an effect on the stationary Kerr-anti-de Sitter black hole's Hawking tunneling radiation rate, temperature and entropy. At last, some comments are made on the results of our work.

Thermodynamic Properties in Higher-Derivative Electrodynamics

In this work, we study the thermodynamic properties of a photon gas in a heat bath within the context of higher-derivative electrodynamics. Specifically, we analyze Podolsky's theory and its extension involving the Lorentz symmetry violation recently proposed in the literature. First, we use the concept of the number of available states of the system in order to construct the partition function. Next, we calculate the main thermodynamic functions: Helmholtz free energy, mean energy, entropy, and heat capacity. In particular, we verify that there exist significant changes in heat capacity and mean energy due to Lorentz violation. Additionally, the modification of the black body radiation and the correction to the Stefan-Boltzmann law in the context of the primordial inflationary universe are provided for both theories as well.

Improved Bounds on Lorentz Symmetry Violation from High-Energy Astrophysical Sources

Observations of the synchrotron and inverse Compton emissions from ultrarelativistic electrons in astrophysical sources can reveal a great deal about the energy–momentum relations of those electrons. They can thus be used to place bounds on the possibility of Lorentz violation in the electron sector. Recent γ-ray telescope data allow the Lorentz-violating electron cνμ parameters to be constrained extremely well, so that all bounds are at the level of 7×10−16 or better.

Attractive inverse-square–type interaction induced by Lorentz symmetry violation by fixed vector background

Based on a model that goes beyond the Standard Model, we study quantum effects of the violation of the Lorentz symmetry at a low-energy regime. From a background of the Lorentz symmetry violation determined by a space-like vector field and electric fields, we obtain an attractive inverse-square–type interaction. In addition, we obtain the bound-states solutions to the Schrödinger equation.

Attractive inverse-square interaction from Lorentz symmetry breaking effects at a low energy scenario

We analyze nonrelativistic quantum effects on a neutral particle due to the presence of an attractive inverse-square potential that stems from the effects of the Lorentz symmetry violation determined by the parity-even sector of the tensor [Formula: see text]. We show that bound states solutions to the Schrödinger equation can be achieved. We go further by considering a repulsive inverse-square potential yielded by Lorentz symmetry breaking effects, which are also determined the parity-even sector of the tensor [Formula: see text]. Then, we analyze the influence of this repulsive inverse-square potential on a neutral particle confined to two cylindrical surfaces and a cylindrical surface.

Black hole superradiance in the presence of Lorentz symmetry violation

In this paper we consider the massive scalar perturbation on the top of a small spinning-like black hole in context of Einstein-bumblebee modified gravity in order to probe the role of spontaneous Lorentz symmetry breaking on the superradiance scattering and corresponding instability. We show that at the low-frequency limit of the scalar wave the superradiance scattering will be enhanced with the Lorentz-violating parameter $\alpha<0$ and will be weakened with $\alpha>0$. Moreover, by addressing the black hole bomb issue, we extract an improved bound in the instability regime indicating that $\alpha<0$ increases the parameter space of the scalar field instability, while $\alpha>0$ decreases it.

Kink properties in Lorentz-violating scalar field theory

We consider topological defects for the λϕ4 theory in (1+1) dimensions with a Lorentz-violating background. It has been shown, by M. Barreto et al. (2006) [34], one cannot have original effects in (the leading order of) single scalar field model. Here, we introduce a new Lorentz-violating term, next to leading order which cannot be absorbed by any redefinition of the scalar field or coordinates. Our term is the lowest order term which leads to concrete effects on the kink properties. We calculate the corrections to the kink shape and the corresponding mass. Quantization of the kink is performed and the revised modes are obtained. We find the bound and continuum states are affected due to this Lorentz symmetry violation.

Black holes with a cosmological constant in bumblebee gravity

In this work, we present black hole solutions with a cosmological constant in bumblebee gravity, which provides a mechanism for the Lorentz symmetry violation by assuming a nonzero vacuum expectation value for the bumblebee field. From the gravitational point of view, such solutions are spherically symmetric black holes with an effective cosmological constant and are supported by an anisotropic energy-momentum tensor, conceived of as the manifestation of the bumblebee field in the spacetime geometry. Then we calculate the shadow angular radius for the proposed black hole solution with a positive effective cosmological constant. In particular, our results are the very first relation between the bumblebee field and the shadow angular size.

SNO: Recent new results

The Sudbury Neutrino Observatory (SNO), whose main purpose was to study the neutrinos produced in the Sun, demonstrated that neutrinos can change flavor and, thus, they are massive particles. SNO detected and recorded neutrino and cosmic ray interactions from 1999 to 2006 and several analyses have been completed in the past year using legacy data. We present the results of the most recent ones: the measurements of neutron production in atmospheric neutrino interactions and neutron production by cosmic muons, a search for Lorentz symmetry violation in neutrino oscillations and a search for neutrino decay. A few other analyses are ongoing and we comment about their goal and status.