Invariance Violation Research Articles

Schiff moments of Hg isotopes in the nuclear shell model

Existence of the permanent electric dipole moment of a fundamental particle implies violation of time reversal invariance. The electric dipole moment of a diamagnetic neutral atom is mainly induced by the nuclear Schiff moment. In this study the Schiff moment induced by the interaction which violates parity and time reversal invariance is calculated for the 199Hg nucleus in terms of the nuclear shell model.

Predictions of Ultra-High Energy Cosmic Ray Propagation in the Context of Homogeneously Modified Special Relativity

Ultra high energy cosmic rays (UHECRs) may interact with photon backgrounds and thus the universe is opaque to their propagation. Many Lorentz Invariance Violation (LIV) theories predict a dilation of the expected horizon from which UHECRs can arrive to Earth, in some case even making the interaction probability negligible. In this work, we investigate this effect in the context of the LIV theory that goes by the name of Homogeneously Modified Special Relativity (HMSR). In this work, making use of a specifically modified version of the SimProp simulation program in order to account for the modifications introduced by the theory to the propagation of particles, the radius of the proton opacity horizon (GZK sphere), and the attenuation length for the photopion production process are simulated and the modifications of these quantities introduced by the theory are studied.

Aspects and applications of nonlocal Lorentz violation

We consider simple scalar theories with quadratic terms that are nonlocal and Lorentz violating. Unlike similar Lorentz-invariant nonlocal theories that we have considered previously, the theories studied here are both ghost-free and unitary as formulated in Minkowski space. We explore the possibility that the scale of nonlocality could be low in a dark sector, where the stringent constraints on the violation of Lorentz invariance may be accommodated via the weak coupling to the standard model. We point out that long-range forces may originate from such a sector and be distinguishable from more conventional beyond-the-standard model possibilities. We present a model in which a nonlocal, Lorentz-violating dark sector communicates with the standard model via a sector of heavy vector-like fermions, a concrete framework in which phenomenological constraints and signals can be investigated.

Phenomenological Effects of CPT and Lorentz Invariance Violation in Particle and Astroparticle Physics

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.

Constraints on Ho\u0159ava\u2013Lifshitz gravity from GRB 170817A

In this work we focus on a toy model: (3+1)-dimensional Hořava–Lifshitz gravity coupling with an anisotropic electromagnetic (EM) field which is generated through a Kaluza-Klein reduction of a (4+1)-dimensional Hořava–Lifshitz gravity. This model exhibits a remarkable feature that it has the same velocity for both gravitational and electromagnetic waves. This feature makes it possible to restrict the parameters of the theory from GRB 170817A. In this work we use this feature to discuss possible constraints on the parameter beta in the theory, by analyzing the possible Lorentz invariance violation effect of the GRB 170817A. This is achieved by analyzing potential time delay of gamma-ray photons in this event. It turns out that it places a stringent constraint on this parameter. In the most ideal case, it gives |1-sqrt{beta }|<(10^{-19}-10^{-18}).

Spherical-harmonic tensors

The connection between spherical harmonics and symmetric tensors is explored. For each spherical harmonic, a corresponding traceless symmetric tensor is constructed. These tensors are then extended to include nonzero traces, providing an orthonormal angular-momentum eigenbasis for symmetric tensors of any rank. The relationship between the spherical-harmonic tensors and spin-weighted spherical harmonics is derived. The results facilitate the spherical-harmonic expansion of a large class of tensor-valued functions. Several simple illustrative examples are discussed, and the formalism is used to derive the leading-order effects of violations of Lorentz invariance in Newtonian gravity.

Tunnelling radiation and the microstates of a black hole influenced by the Lorentz invariance violation

In this paper, we have employed the second-order Lorentz invariance violation (LIV) to carefully investigate the effect of quantum gravity on the Hawking radiation of the Dirac particle via tunneling from the Kerr black hole. Firstly, it turns out that the Hawking temperature is not only related to the angular momentum and mass of the black hole, but related to the energy and mass of the emitted particle. In particular, we find that the effective temperature is bigger and bigger with the increase of the energy ω, the angular momentum j and the LIV parameter l p , but is smaller and smaller with the increase of the black hole mass M. Also, it further shows that, although quantum gravity speeds up the black-hole evaporation, it will not evaporate completely, instead a remaining mass, temperature and entropy are left. Finally, through a careful count of the number of the microstates taken away by the black-hole radiation, the initial and remaining number of microstates for the Schwarzschild black hole are presented with the inclusion of the LIV-induced quantum gravity effects.

Limiting superluminal neutrino velocity and Lorentz invariance violation by neutrino emission from the blazar TXS 0506+056

The detection of high-energy neutrino coincident with the blazar TXS 0506+056 provides a unique opportunity to test Lorentz invariance violation (LIV) in the neutrino sector. Thanks to the precisely measured redshift, i.e., $z=0.3365$, the comoving distance of the neutrino source is determined. In this work, we obtain and discuss the constraints on the superluminal neutrino velocity $\delta_\nu$ and the LIV by considering the energy loss of superluminal neutrino during propagation. Given superluminal electron velocity ($\delta_e \ge 0$), a very stringent constraint on superluminal neutrino velocity can be reached, i.e., $\delta_\nu \lesssim 1.3\times 10^{-18}$, corresponding to the quantum gravity (QG) scale $M_{\rm QG,1} \gtrsim 5.7 \times 10^{3} M_{\rm Pl}$ and $M_{\rm QG,2} \gtrsim 9.3 \times 10^{-6} M_{\rm Pl}$ for linear (quadratic) LIV, which are $\sim 12$ orders of magnitude tighter for linear LIV and $\sim 9$ orders tighter for quadratic LIV compared to the time-of-flight constraint from MeV neutrinos of SN 1987A. While given the subluminal electron velocity, a weaker constraint on the superluminal neutrino velocity is obtained, i.e., $\delta_\nu \lesssim 8 \times 10^{-17}$, which is consistent with the conclusions of previous works. We also study the neutrino detection probability due to the distortion of neutrino spectral shape during propagation, which gives slightly weaker constraints than above by a factor of $\sim2$.

Effect of torsion on the radiation fields in curved spacetime

The torsion-free connection is one of the important assumptions in Einstein's General theory of Relativity which has not been verified so far from experimental observation. In this article, the effect of torsion on the on-shell action of radiation fields in curved spacetime is reported in order to show certain consequences and possible ways to probe torsion in curved spacetime. In order to describe non-vanishing torsion, we mostly use contorsion tensor in connection which can be written in the combination of torsion tensor and vice versa. We have discussed how does the field equation coming from the minimization of action with respect to torsion changes the matter part of the on-shell action of radiation through substitution of the spin tensor. We have also studied here the effect of torsion on the scalar and vector radiation field in curved spacetime. It is shown that the presence of torsion leads to extra polarizations in Gravitational waves or radiations other than the usual two polarizations already present in General Relativity. Further, it is also shown that in the presence of torsion, there exists a non-trivial vacuum configuration that is different from the trivial vacuum in the absence of coupling with torsion. It is also found that in a generic theory of vector field, the presence of torsion breaks the U(1) gauge invariance just like the presence of mass shows the violation of gauge invariance. The observational consequences of these results are also discussed.

Parity-nonconserving interactions of electrons in chiral molecules with cosmic fields

Pseudoscalar or pseudovector cosmic fields, that serve as a source of parity ($\mathcal{P}$) violation, are invoked in different models for cold dark matter or in the standard model extension that allows for Lorentz invariance violation. A direct detection of the timelike-component of such fields requires a direct measurement of $\mathcal{P}$-odd potentials or their evolution over time. Herein, advantageous properties of chiral molecules, in which $\mathcal{P}$-odd potentials lead to resonance frequency differences between enantiomers, for direct detection of such $\mathcal{P}$-odd cosmic fields are demonstrated. Scaling behavior of electronic structure enhancements of such interactions with respect to nuclear charge number and the fine-structure constant is derived analytically. This allows a simple estimate of the effect sizes for arbitrary molecules. The analytical derivation is supported by quasi-relativistic numerical calculations in the molecules H$_2$X$_2$ and H$_2$XO with X $=$ O, S, Se, Te, Po. Parity violating effects due to cosmic fields on the C--F stretching mode in CHBrClF are compared to electroweak parity violation and influences of non-separable anharmonic vibrational corrections are discussed. On this basis it was estimated from a twenty year old experiment with CHBrClF that bounds on Lorentz invariance violation as characterized by the parameter $|b^\mathrm{e}_0|$ can be pushed down to the order of $10^{-17}\,\mathrm{GeV}$ in modern experiments with suitably selected molecular system, which will be an improvement of the current best limits by at least two orders of magnitude. This serves to highlight the particular opportunities that precision spectroscopy of chiral molecules provides in the search for new physics beyond the standard model.

Description-dependent preferences

Abstract We propose a theoretical perspective on framing effects where decision makers violate the axiom of description invariance. We first propose a framework that makes this axiom explicit and then we weaken it to allow for description dependence. This framework provides a structure to disentangle different violations of description invariance. We then identify a particular class of violations that we call tidy description-dependent preferences, which are compatible with a transitive preference relation over the consequences of the choice set. We show that many violations observed in the literature are actually in this class.

Prospective Annual Detection Rate of High-energy Gamma-Ray Bursts with LHAASO-WCDA

Abstract Gamma-ray bursts (GRBs) are considered one of the most violent, explosive events in the universe and serve as high-redshift probes for cosmological study due to their high-energy observations. Such observations, particularly in the GeV regime, have already proven fruitful for deriving useful scientific results, such as the determination of extragalactic background light (EBL) and the stringent constraint on the Lorentz invariance violation effect. Owing to the advantages of a very large effective area, a low threshold energy, a wide field of view, and high duty cycle, the upcoming Large High Altitude Air Shower Observatory–Water Cerenkov Detector Array (LHAASO-WCDA) will have potential sensitivity for discovering GRBs in the 100 GeV energy region. In this work, a sample of GRBs has been generated and examined based on existing observations reported by the Large Area Telescope on board the Fermi satellite. The Fermi spectra are extrapolated to high energy by taking into account the absorption due to the pair production processes occurring between γ rays and EBL. With an assumption that an ultrahigh-energy component accounts for 10% of the total luminosity, it is found that LHAASO-WCDA has a GRB detection rate of ∼one GRB per year.

Examining the effect of mid-test warnings on factor structure of personality scores: A field experiment

Warning messages delivered in the middle of a personality test (i.e., mid-test warnings) have emerged as a promising method to mitigate applicant faking in terms of lowering personality mean scores. However, little is known about whether mid-test warnings might also affect personality factor structure. The present study investigated this prominent issue through a field experiment. Participants were applicants for graduate programs at a large public university in China, who were instructed to complete an online Big-Five personality test as part of the selection procedure. During the personality test, three messages (control, mid-test warning with accusation, and mid-test warning without accusation) were randomly delivered to applicants. Our analysis focused on the ten personality subscales included in both the initial block (before the mid-test messages) and the main block (after the mid-test messages). Results indicated that (a) the control message did not lead to the violation of configural, metric, and scalar invariance, and (b) the two mid-test warnings did not result in the violation of configural and metric invariance but led to scalar non-invariance. These findings suggest that mid-test warnings reduce faking by lowering intercepts, but do not adversely affect the configural and metric aspects of personality factor structure.

Bounds on Relativistic Deformed Kinematics from the Physics of the Universe Transparency

We analyze the kinematics of electron-positron production in a photon-photon interaction when one has a modification of the special relativistic kinematics as a power expansion in the inverse of a new high-energy scale. We derive the equation for the threshold energy of this reaction to first order in this expansion, including the effects due to a modification of the energy-momentum conservation equation. In contrast with the Lorentz invariance violation case, a scale of the order of a few TeV is found to be compatible with the observations of very high-energy cosmic gamma rays in the case of a modification compatible with the relativity principle.

Can Lorentz invariance violation affect the sensitivity of deep underground neutrino experiment?

We examine the impact of Lorentz Invariance Violation (LIV) in measuring the octant of theta _{23} and CP phases in the context of the Deep Underground Neutrino Experiment (DUNE). We consider the CPT-violating LIV parameters involving e - mu (a_{emu }) and e - tau (a_{etau }) flavors, which induce an additional interference term in neutrino and antineutrino appearance probabilities. This new interference term depends on both the standard CP phase delta and the new dynamical CP phase varphi _{emu }/varphi _{etau }, giving rise to new degeneracies among (theta _{23}, delta , varphi ). Taking one LIV parameter at-a-time and considering a small value of |a_{emu }| = |a_{etau }| = 5 times 10^{-24} GeV, we find that the octant discovery potential of DUNE gets substantially deteriorated for unfavorable combinations of delta and varphi _{emu }/varphi _{etau }. The octant of theta _{23} can only be resolved at 3sigma if the true value of sin ^2theta _{23} lesssim 0.42 or > rsim 0.62 for any choices of delta and varphi . Interestingly, we also observe that when both the LIV parameters a_{emu } and a_{etau } are present together, they cancel out the impact of each other to a significant extent, allowing DUNE to largely regain its octant resolution capability. We also reconstruct the CP phases delta and varphi _{emu }/varphi _{etau }. The typical 1sigma uncertainty on delta is 10–15^{circ } and the same on varphi _{emu }/varphi _{etau } is 25–30^{circ } depending on the choices of their true values.

Eicheons instead of Black holes

A new spherically-symmetric solution for a gravitational field is found in the conformally-unimodular metric. It is shown, that the surface of the black hole horizon in the standard Schwarzschild metric can be squeezed to a point by converting coordinates to the conformally-unimodular metric. In this new metric, there is no black hole horizon, while the naked singularity corresponds to a point massive particle. The reason for the study of this particular gauge (i.e., conformally-unimodular metric) is its relation to the vacuum energy problem. That aims to relate it to other physical phenomena (including black holes), and one could argue that they should be considered in this particular metric. That means the violation of the gauge invariance of the general theory of relativity. As a result, the nonsingular ‘eicheons’ appear as the non-point compact objects with different masses and structures. They are a final product of the stellar collapse, with the masses exceeding the Tolman-Oppenheimer-Volkoff limit.

Robust Haebara Linking for Many Groups: Performance in the Case of Uniform DIF

The comparison of group means in item response models constitutes an important issue in empirical research. The present article discusses a slight extension of the robust Haebara linking approach of He and Cui by proposing a flexible class of robust Haebara linking functions for comparisons of many groups. These robust linking functions are robust against violations of invariance. In this article, we investigate the performance of robust Haebara linking in the presence of uniform DIF effects. In an analytical derivation, it is shown that the robust Haebara linking approach provides unbiased estimates of group means in the limiting case p=0. In a simulation study, it is demonstrated that the proposed variant of the Haebara linking approach outperforms existing implementations of Haebara linking to some extent. In an empirical application using PISA data, it is illustrated that country means can be sensitive to the choice of linking functions.

Lorentz Invariance Violation Tests in Astroparticle Physics

In this review, we present the latest exclusion limits obtained from astroparticles on Lorentz Invariance Violation (LIV) in the photon sector. We discuss the techniques known as energy-dependent time delay or time lag, subluminal pair production threshold shift, suppression of air shower formation, superluminal photon decay, and superluminal photon splitting. Perspectives for future results on LIV with the next generation of experiments are also addressed.

Neutron spin dynamics in polarized targets

We present neutron elastic scattering amplitude for arbitrary polarized target in irreducible spherical tensor representation. The general approach for the description of neutron spin dynamics for the propagation trough the medium with an arbitrary polarization is discussed in a relation to the search for time reversal invariance violation in neutron scattering.

On the lightlike Lorentz violation

We consider the lightlike spontaneous Lorentz invariance violation (SLIV) appearing through the zero “length-fixing” constraint put on a gauge vector field, AμAμ=0, and discuss its physical consequences in the framework of a conventional QED and beyond. Again, as in the timelike and spacelike SLIV cases, AμAμ=±MA2 (MA is a scale of SLIV), while this constraint leads to an emergence of the Nambu-Goldstone modes collected in physical photon, the SLIV itself is still left unobservable unless gauge invariance in the theory is broken. At the same time, a crucial difference with the two former cases is that the asymmetrical vacuum corresponding to the lightlike Lorentz violation appears infinitely degenerated with all other vacua including the symmetrical one. We show that this degeneracy can be lifted out by introducing an extra gauge vector field being sterile with respect to an ordinary matter, though having some potential couplings with the basic Aμ field. A slight mixing of them makes the underlying gauge invariance to be partially broken due to which physical Lorentz invariance occurs broken as well. This may cause a variety of the Lorentz violating processes some of which are briefly discussed.