Lorentz Symmetry Violation Research Articles

On a massive scalar field subject to the relativistic Landau quantization in an environment of aether-like Lorentz symmetry violation

We analyze the effects of the aether-like Lorentz symmetry violation on a massive scalar field subject to a uniform magnetic field, where, analytically, we determine the relativistic Landau levels and note that this background governed by a constant vector field modifies the energy spectrum of the relativistic quantum system. We extend our analysis by including a hard-wall potential in the system, and, under some conditions, we determine the energy spectrum of the scalar field and show that the presence of this confinement potential drastically modifies the relativistic energy levels in this possible scenario of breaking of the Lorentz symmetry.

A Massive Scalar Field under the Effects of the Lorentz Symmetry Violation by a CPT-Odd Nonminimal Coupling

In this paper, based on the Standard Model Extended gauge sector, we made a nonminimal coupling in the Klein–Gordon equation which characterizes the Lorentz symmetry violation and, through this nonminimal CPT-odd coupling, we investigate the effects of possible scenarios of Lorentz symmetry violation by electrical and magnetic field configurations on a massive scalar field in this background, where, analytically, we determine solutions of bound states.

Bounds on Planck-scale Deformations of CPT from Lifetimes and Interference

Deformed relativistic kinematics, expected to emerge in a flat-spacetime limit of quantum gravity, predicts violation of discrete symmetries at energy scale in the vicinity of the Planck mass. Momentum-dependent deformations of the C, P and T invariance are derived from the \k{appa}-deformed Poincar\'e algebra. Deformation of the CPT symmetry leads to a subtle violation of Lorentz symmetry. This entails some small but measurable phenomenological consequences, as corrections to characteristics of time evolution: particle lifetimes or frequency of flavour oscillations in two-particle states at high energy. We argue here that using current experimental precisions on the muon lifetime one can bound the deformation parameter \k{appa} > 10^14 GeV at LHC energy and move this limit even to 10^16 GeV at Future Circular Collider, planned at CERN. Weaker limits on deformation can be also obtained from interference of neutral mesons. In case of B0s from {\Upsilon} decay it amounts to \k{appa} > 10^8 GeV at confidence level 99%.

Neutrino oscillations in a quantum processor

Quantum computing technologies promise to revolutionize calculations in many areas of physics, chemistry, and data science. Their power is expected to be especially pronounced for problems where direct analogs of a quantum system under study can be encoded coherently within a quantum computer. A first step toward harnessing this power is to express the building blocks of known physical systems within the language of quantum gates and circuits. In this paper, we present a quantum calculation of an archetypal quantum system: neutrino oscillations. We define gate arrangements that implement the neutral lepton mixing operation and neutrino time evolution in two-, three-, and four-flavor systems. We then calculate oscillation probabilities by coherently preparing quantum states within the processor, time evolving them unitarily, and performing measurements in the flavor basis, with close analogy to the physical processes realized in neutrino oscillation experiments, finding excellent agreement with classical calculations. We provide recipes for modeling oscillation in the standard three-flavor paradigm as well as beyond-standard-model scenarios, including systems with sterile neutrinos, non-standard interactions, Lorentz symmetry violation, and anomalous decoherence.

Singular Hamiltonians in models with spontaneous Lorentz symmetry breaking

Many current models which ``violate Lorentz symmetry'' do so via a vector or tensor field which takes on a vacuum expectation value, thereby spontaneously breaking the underlying Lorentz symmetry of the Lagrangian. One common way to construct such a model is to posit a smooth potential for this field; the natural low-energy solution of such a model would then be excepted to have the tensor field near the minimum of its potential. It is shown in this work that some such models, while appearing well posed at the level of the Lagrangian, have a Hamiltonian which is singular on the vacuum manifold and are therefore ill posed. I illustrate this pathology for an antisymmetric rank-2 tensor field and find sufficient conditions under which this pathology occurs for more general field theories.

Velocity-dependent deformations of the energy spectrum of a quantum cavity from Lorentz symmetry violations

Several approaches to quantum gravity suggest that Lorentz invariance will be broken at high energy. This can lead to modified dispersion relations for wave propagation, which can be concretely realized in effective field theories where the equation of motion involves higher order spatial derivatives in a preferred frame. We consider such a model in the presence of a finite cavity whose walls follow parallel inertial trajectories of speed $v$ with respect to the preferred frame. We find evidence that when the cavity wall speed exceeds the phase velocity, the system becomes classically unstable. For dispersion relations that do not lead to an instability, the energy levels of the cavity are non-trivial functions of $v$. In other words, an observer could in principle measure their velocity with respect to the preferred frame by studying the energy spectra of a quantum cavity, which is a stark violation of the principle of relativity. We also find that the energy levels of the cavity become infinitely large as its velocity approaches light speed.

Topological band theory for non-Hermitian systems from the Dirac equation

We identify and investigate two classes of non-Hermitian systems, i.e., one resulting from Lorentz-symmetry violation (LSV) and the other from a complex mass (CM) with Lorentz invariance, from the perspective of quantum field theory. The mechanisms to break, and approaches to restore, the bulk-boundary correspondence in these two types of non-Hermitian systems are clarified. The non-Hermitian system with LSV shows a non-Hermitian skin effect, and its topological phase can be characterized by mapping it to the Hermitian system via a non-compact $U(1)$ gauge transformation. In contrast, there exists no non-Hermitian skin effect for the non-Hermitian system with CM. Moreover, the conventional bulk-boundary correspondence holds in this (CM) system. We also consider a general non-Hermitian system in the presence of both LSV and CM, and we generalize its bulk-boundary correspondence.

Frame dependence of transition form factors in light-front dynamics

We calculate the transition form factor between vector and pseudoscalar quarkonia in both the timelike and the spacelike region using light-front dynamics. We investigate the frame dependence of the form factors for heavy quarkonia with light-front wavefunctions calculated from the valence Fock sector. This dependence could serve as a measure for the Lorentz symmetry violation arising from the Fock-space truncation. We suggest using frames with minimal longitudinal momentum transfer for calculations in the valence Fock sector, namely the Drell-Yan frame for the space-like region and a specific longitudinal frame for the timelike region; at $q^2=0$ these two frames give the same result. We also use the transition form factor in the timelike region to investigate the electromagnetic Dalitz decay $\psi_A\to \psi_B l^+l^-$ ($l = e,\mu$) and predict the effective mass spectrum of the lepton pair.

Relativistic scalar Aharonov–Bohm effect for a neutral particle under Lorentz symmetry breaking effects in the cosmic string space–time

We search for relativistic quantum phases for a Dirac neutral particle with a permanent magnetic dipole moment in the cosmic string space–time under the effects of the violation of the Lorentz symmetry. This general relativity background is built based on the modified Maxwell theory coupled to gravity. Hence, we analyze analogues of the scalar Aharonov–Bohm effect for neutral particles in two different scenarios of the Lorentz symmetry violation in the cosmic string space–time.

Fermionic Casimir effect in Horava–Lifshitz theories

In this paper, we analyze the fermionic Casimir effects associated with a massless quantum field in the context of Lorentz symmetry violation approach based on Horava–Lifshitz methodology. In order to obtain these observables, we impose the standard MIT bag boundary condition on the fields on two large and parallel plates. Our main objectives are to investigate how the Casimir energy and pressure depend on the parameter associated with the breaking of Lorentz symmetry.

Exploiting the violation of Lorentz symmetry for the planar Hall effect

The low energy Dirac and Weyl spectra are allowed to violate the Lorentz symmetry and thereby have a tilted energy dispersion. The tilt in the energy dispersion induces a Hall voltage in the plane spanned by the electric field and the tilt velocity. In the presence of a magnetic field the planar Hall conductivity and resistivity show Shubnikov de Haas oscillations. The oscillations in the planar Hall effect can become a fingerprint to spot the anomalous transport in Dirac and Weyl semimetals.

Planar phenomena in CPT -even chiral QED with Lorentz violation

Quantum gravity models as string theory, loop quantum gravity, and noncommutative field theories allow for the violation of Lorentz symmetry in the Planck scale. In order to examine the implications of such violation in planar models, we present here a $CPT$-even effective model, in the Standard Model extension framework, for Maxwell-Chern-Simons quantum electrodynamics $({\mathrm{QED}}_{3})$, with a Lorentz violation tensor parameter coupled to the photon field. The magnetoelectric effect induced by the space-time anisotropy in the model is discussed. We then derive the exact classical photon propagator. The electrostatic interaction is investigated and the long-range classical potential, corrected to second order in the Lorentz-violating tensor parameter, is obtained as well as its radiative correction in the isotropic violation scenario, derived at one-loop approximation from the vacuum polarization tensor. Also, the contribution of the space-time anisotropy to the magnetic moment of the fermion trough the vertex diagram is evaluated on shell and in the forward scattering approximation, in the absence of the topological Chern-Simons term.

A Central Potential with a Massive Scalar Field in a Lorentz Symmetry Violation Environment

We investigate the behaviour of a massive scalar field under the influence of a Coulomb-type and central linear central potentials inserted in the Klein-Gordon equation by modifying the mass term in the spacetime with Lorentz symmetry violation. We consider the presence of a background constant vector field which characterizes the breaking of the Lorentz symmetry and show that analytical solutions to the Klein-Gordon equation can be achieved.

Fermionic Casimir effect in a field theory model with Lorentz symmetry violation

In this paper, we evaluate the Casimir energy and pressure for a massive fermionic field confined in the region between two parallel plates. In order to implement this confinement we impose the standard MIT bag boundary on the plates for the fermionic field. In this paper we consider a quantum field theory model with a $CPT$ even, aetherlike Lorentz symmetry violation. It turns out that the fermionic Casimir energy and pressure depend on the direction of the constant vector that implements the Lorentz symmetry breaking.

Enhancing test precision for local Lorentz-symmetry violation with entanglement

A recent proposal for testing Lorentz-symmetry violation (LSV) presents a formulation where the effect of violation is described as a local interaction [R. Shaniv et al., Phys. Rev. Lett. 120, 103202 (2018)]. An entangled ion pair in a decoherence free subspace (DFS) is shown to double the signal-to-noise ratio (SNR) of one ion, while (even)-$N/2$ such DFS pairs in a collective entangled state improve SNR by $N$ times, provided the state parity or the even or odd numbers of ions can be measured. It remains to find out, however, how such fiducial entangled states can be prepared at nonexponentially small success rates. This work suggests two types of many-particle entangled states for testing LSV: the maximally entangled NOON state, which can achieve Heisenberg limited precision; and the balanced spin-1 Dicke state, which is readily available in deterministic fashion. We show that the latter also lives in a DFS and is immune to stray magnetic fields. It can achieve classical precision limit or the standard quantum limit (SQL) based on collective population measurement without individual atom resolution. Given the high interests in LSV and in entanglement assisted quantum metrology, our observation offers additional incentives for pursuing practical applications of many-atom entangled states.

Optical clockcomparison for Lorentz symmetry testing.

Questioning basic assumptions about the structure of space and time has greatly enhancedour understanding of nature. State-of-the-art atomic clocks1-3 make it possible to precisely test fundamental symmetry properties of spacetime and search for physics beyond the standard model at low energies of just a few electronvolts4. Modern tests of Einstein's theory of relativity try to measure so-far-undetected violations of Lorentz symmetry5; accurately comparing the frequencies of optical clocks is a promising route to further improving such tests6. Here we experimentally demonstrate agreement between two single-ion optical clocks at the 10-18 level, directly validating their uncertainty budgets, over a six-month comparison period. The ytterbium ions of the two clocks are confined in separate ion traps with quantization axes aligned along non-parallel directions. Hypothetical Lorentz symmetry violations5-7 would lead to periodic modulations of the frequency offset as the Earth rotates and orbits the Sun. From the absence of such modulations at the 10-19 level we deduce stringent limits of the order of 10-21 on Lorentz symmetry violation parameters for electrons, improving previous limits8-10 by two orders of magnitude. Such levels of precision will be essential for low-energy tests of future quantum gravity theories describing dynamics at the Planck scale4, which are expected to predict the magnitude of residual symmetry violations.

Phenomenology of minimal theory of quasidilaton massive gravity

The minimal theory of quasidilaton massive gravity with or without a Horndeski-type kinetic term for the quasidilaton field propagates only three physical modes: the two massive tensor polarizations and one scalar mode. This reduced number of degrees of freedom is realized by a Lorentz symmetry violation at cosmological scales and the presence of appropriate constraints that remove unwanted modes. Vacuum cosmological solutions have been considered in a previous work, and it has been shown that the late-time de Sitter attractor is stable under inhomogeneous perturbations. In this work, we explore the stability of cosmological solutions in the presence of matter fields. Assuming for simplicity that the quasidilaton scalar is on an attractor at the level of the background, we derive stability conditions in the subhorizon limit, and find the scalar sound speeds, as well as the modification with respect to general relativity to the gravitational potential in the quasistatic approximation. We also find that the speed limit of gravitational waves coincides with the speed of light for any homogeneous and isotropic cosmological background, on or away from the attractor.

On Lorentz violation in e− + e+ → μ− + μ+ scattering at finite temperature

Small violation of Lorentz and CPT symmetries may emerge in models unifying gravity with other forces of nature. An extension of the standard model with all possible terms that violate Lorentz and CPT symmetries are included. Here a CPT-even non-minimal coupling term is added to the covariant derivative. This leads to a new interaction term that breaks the Lorentz symmetry. Our main objective is to calculate the cross section for the e−+e+→μ−+μ+ scattering in order to investigate any violation of Lorentz and/or CPT symmetry at finite temperature. Thermo Field Dynamics formalism is used to consider finite temperature effects.

Effective Potential for binary mistures of a Bose-Einsten

It has a degree, a master’s degree and a doctorate from the University of the State of Rio de Janeiro (UERJ). He has postdated at the Brazilian Center for Physical Research (CBPF). Hasexperience in the field of condensed matter physics, phase transition to finite temperature such ascondensation of Bose-Eistein. He developed a study on BCS-BEC crossover (CBPF). His research isnow centered on the study of gauge theories for gravitation, effective gauge theories with violationof Lorentz symmetry, and effects of spin-orbit interaction on a more fundamental physics via theweakly relativistic boundary of the Dirac equation.

Constraints and degrees of freedom in Lorentz-violating field theories

Many current models which "violate Lorentz symmetry" do so via a vector or tensor field which takes on a vacuum expectation value, thereby spontaneously breaking the underlying Lorentz symmetry of the Lagrangian. To obtain a tensor field with this behavior, one can posit a smooth potential for this field, in which case it would be expected to lie near the minimum of its potential. Alternately, one can enforce a non-zero tensor value via a Lagrange multiplier. The present work explores the relationship between these two types of theories in the case of vector models. In particular, the na\"ive expectation that a Lagrange multiplier "kills off" one degree of freedom via its constraint does not necessarily hold for vector models that already contain primary constraints. It is shown that a Lagrange multiplier can only reduce the degrees of freedom of a model if the field-space function defining the vacuum manifold commutes with the primary constraints.