Invariance Violation Research Articles

Constraint of d = 8 Lorentz Invariance Violation with New Experimental Design

Short-range gravity experiments are more suitable for the testing of high-order Lorentz symmetry breaking effects. In our previous work, we proposed a new experimental design based on precision torsion balance technology to test the Lorentz violation force effect that varies inversely with the fourth power of distance (corresponding to mass dimension d = 6 term), and the corresponding experiment is currently underway. In this paper, we focus on analyzing the potential of this experimental scheme to test the Lorentz violation force that varies inversely with the sixth power of distance (corresponding to mass dimension d = 8 term). The results show that, compared with the current best limit, the new experimental scheme can improve the constraints on the Lorentz violation coefficients with d = 8 by at least one order of magnitude.

Experimental test of an extension of the Rosenzweig-Porter model to mixed integrable-chaotic systems experiencing time-reversal invariance violation

Abstract We report on the theoretical and experimental investigation of the transition of a typical quantum system with mixed regular-integrable classical dynamics to one with violated time-reversal (T) invariance. The measurements are performed with a flat superconducting microwave resonator with circular shape in which chaoticity is induced by using either long antennas or inserting two circular disks into the cavity, and by magnetizing a ferrite disk placed at its center, which leads to violation of T invariance. We propose an extension of the Rosenzweig-Porter (RP) model, which interpolates between mixed regular-chaotic instead of integrable dynamics and fully chaotic dynamics with violated T-invariance, and derive a Wigner-surmise like analytical expression for the corresponding nearest-neighbor spacing distribution. We propose a procedure involving this result and those for the RP model to determine the size of T-invariance violation and chaoticity and validate it employing the experimental eigenfrequency spectra.

Direct Evidence for Preburst Stage of Gamma-Ray Burst from GRB 221009A Data

Previous research on Lorentz invariance violation in photons from gamma-ray bursts (GRBs) suggested a scenario where multi-GeV photons could be emitted before lower-energy photons at the GRB source frame. This implies the existence of a new preburst phase in addition to the traditionally identified prompt and afterglow stages observed in earlier studies. In this study, we present direct evidence for this novel preburst phase in GRBs based on recent observations of GRB 221009A. Our analysis leverages data from the Fermi Gamma-ray Burst Monitor and Large Area Telescope detectors of the Fermi Gamma-ray Space Telescope, as well as data from the KM2A detector of the Large High Altitude Air-shower Observatory.

Fermi acceleration under Lorentz invariance violation

In this paper, the acceleration of particles in astrophysical sources by the Fermi mechanism is revisited under the assumption of Lorentz invariance violation (LIV). We calculate the energy spectrum and the acceleration time of particles leaving the source as a function of the energy beyond which the Lorentz invariance violation becomes relevant. Lorentz invariance violation causes significant changes in the acceleration of particles by the first and second-order Fermi mechanisms. The energy spectrum of particles accelerated by first-order Fermi mechanism under LIV assumption shows a strong suppression for energies above the break. The calculations presented here complete the scenario for LIV searches with astroparticles by showing, for the first time, how the benchmark acceleration mechanisms (Fermi) are modified under LIV assumption.

Violating Lorentz Invariance Minimally by the Emergence of Nonmetricity? A Perspective

AbstractLorentz invariance belongs to the fundamental symmetries of nature. It is basic for the successful Standard Model of Particle Physics. Nevertheless, within the last decades, Lorentz invariance has been repeatedly questioned. In fact, there exist different research programs addressing this problem. It is argued that a most adequate understanding of a possible violation of Lorentz invariance is achieved in the framework of the gauge‐theoretic approach to gravity: a non‐vanishing nonmetricity of a metric‐affine geometry of spacetime heralds the violation of the Lorentz symmetry.

Maxwell's equal area law for Vaidya-Bonner-de Sitter black hole under Lorentz invariance violation

In this study, we investigate the tunneling of fermions with arbitrary spin near the event horizon of a nonstationary Vaidya-Bonner-de Sitter (VBdS) black hole under Lorentz invariance violation (LIV). The modified Hawking temperature of VBdS black holes is calculated by using tortoise coordinate transformation, Feynman prescription, and Wentzel–Kramers–Brillouin approximation. By considering the cosmological constant as a thermodynamic pressure in the extended phase space, we construct a Maxwell's equal area law under LIV and study the phase transitions of VBdS black hole in , , and planes. The LIV increases the length of the liquid-gas coexistence region. The thermodynamic quantities such as the entropy, heat capacity, Helmholtz free energy, internal energy, enthalpy, and Gibbs free energy of the VBdS black hole are discussed. These quantities tend to increase under LIV. The stability of the black hole is also discussed in the presence of LIV.

Searches for violation of Lorentz invariance in top quark pair production using dilepton events in 13 TeV proton-proton collisions

A search for violation of Lorentz invariance in the production of top quark pairs (tt‾) is presented. The measured normalized differential tt‾ production cross section, as a function of the sidereal time, is examined for potential modulations induced by Lorentz-invariance breaking operators in an effective field theory extension of the standard model (SM). The cross section is measured from collision events collected by the CMS detector at a center-of-mass-energy of 13 TeV, corresponding to an integrated luminosity of 77.8 fb−1, and containing one electron and one muon. The results are found to be compatible with zero, in agreement with the SM, and are used to place upper limits at 68% confidence level on the magnitude of the Lorentz-violating couplings ranging from 1–8×10−3. This is the first precision test of the isotropy in special relativity with top quarks at the LHC, restricting further the bounds on such couplings by up to two orders of magnitude with respect to previous searches conducted at the Tevatron.

Stringent Tests of Lorentz Invariance Violation from LHAASO Observations of GRB 221009A.

On 9 October 2022, the Large High Altitude Air Shower Observatory (LHAASO) reported the observation of the very early TeV afterglow of the brightest-of-all-time gamma-ray burst 221009A, recording the highest photon statistics in the TeV band ever obtained from a gamma-ray burst. We use this unique observation to place stringent constraints on the energy dependence of the speed of light in vacuum, a manifestation of Lorentz invariance violation (LIV) predicted by some quantum gravity (QG) theories. Our results show that the 95% confidence level lower limits on the QG energy scales are E_{QG,1}>10 times the Planck energy E_{Pl} for the linear LIV effect, and E_{QG,2}>6×10^{-8}E_{Pl} for the quadratic LIV effect. Our limits on the quadratic LIV case improve previous best bounds by factors of 5-7.

Shower formation constraints on cubic Lorentz invariance violation parameters in quantum electrodynamics

We present shower formation constraints on the Lorentz invariance violation (LIV) energy scale for photons with a cubic dispersion relation from recent gamma-ray observations in the 100 TeV–PeV energy range by the Large High Altitude Air Shower Observatory (LHAASO). We assume a Myers–Pospelov effective field theory framework, and calculate the suppression for the Bethe–Heitler process which is mainly responsible for the formation of photon-initiated atmospheric showers. Comparing the high-energy photon events with the suppressed flux predictions, we obtain 95%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$95\\%$$\\end{document} CL constraints on the LIV energy scale. The obtained shower constraint ELIV≳O1020GeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_\ extrm{LIV} \\gtrsim \\mathcal {O} \\left( 10^{20} \ ext{ GeV }\\right) $$\\end{document} is significantly weaker than existing birefringence constraints but is independent.

Energy-dependent intrinsic time delay of gamma-ray bursts on testing Lorentz invariance violation

High-energy photons of gamma-ray bursts (GRBs) might be emitted at different intrinsic times with energy dependence at the source. In this letter, we expand the model from previous works on testing the Lorentz Invariance Violation (LV) with the observed GRB data from the Fermi Gamma-ray Space Telescope. We reanalyze the previous data with the full Bayesian parameter estimation method and get consistent results by assuming that the time delays are due to an LV term and a constant intrinsic time delay term. Subsequently, we neglect the LV effect and only consider the intrinsic time delay effect. We assume a common intrinsic time delay term along with a source energy correlated time delay of high-energy photons. We find that the energy-dependent emission times can also explain the observed GRB data of high-energy photon events. Finally, we integrate these two physical mechanisms into a unified model to distinguish and evaluate their respective contributions using the observed GRB data.

A many-facet Rasch measurement model approach to investigating objective structured clinical examination item parameter drift.

Objective Structured Clinical Examinations (OSCEs) are widely used for assessing clinical competence, especially in high-stakes environments such as medical licensure. However, the reuse of OSCE cases across multiple administrations raises concerns about parameter stability, known as item parameter drift (IPD). AIMS &OBJECTIVES: This study aims to investigate IPD in reused OSCE cases while accounting for examiner scoring effects using a Many-facet Rasch Measurement (MFRM) model. Data from 12 OSCE cases, reused over seven administrations of the Internationally Educated Nurse Competency Assessment Program (IENCAP), were analyzed using the MFRM model. Each case was treated as an item, and examiner scoring effects were accounted for in the analysis. The results indicated that despite accounting for examiner effects, all cases exhibited some level of IPD, with an average absolute IPD of 0.21 logits. Three cases showed positive directional trends. IPD significantly affected score decisions in 1.19% of estimates, at an invariance violation of 0.58 logits. These findings suggest that while OSCE cases demonstrate sufficient stability for reuse, continuous monitoring is essential to ensure the accuracy of score interpretations and decisions. The study provides an objective threshold for detecting concerning levels of IPD and underscores the importance of addressing examiner scoring effects in OSCE assessments. The MFRM model offers a robust framework for tracking and mitigating IPD, contributing to the validity and reliability of OSCEs in evaluating clinical competence.

P T-symmetric photonic lattices with type-II Dirac cones.

The type-II Dirac cone is a special feature of the band structure, whose Fermi level is represented by a pair of crossing lines. It has been demonstrated that such a structure is useful for investigating topological edge solitons and, more specifically, for mimicking the Klein tunneling. However, it is still not clear what the interplay between type-II Dirac cones and the non-Hermiticity mechanism will result in. Here, this question is addressed; in particular, we report the P T-symmetric photonic lattices with type-II Dirac cones for the first time to our knowledge. We identify a slope-exceptional ring and name it the type-II exceptional ring. We display the restoration of the P T symmetry of the lattice by reducing the separation between the sites in the unit cell. Curiously, the amplitude of the beam during propagation in the non-Hermitian lattice with P T symmetry only decays because of diffraction, whereas in the P T symmetry-broken lattice it will be amplified, even though the beam still diffracts. This work establishes the link between the non-Hermiticity mechanism and the violation of Lorentz invariance in these physical systems.

Separating source-intrinsic and Lorentz invariance violation induced delays in the very high-energy emission of blazar flares

The aim of the present study is to explore how to disentangle energy-dependent time delays due to a possible Lorentz invariance violation (LIV) at Planck scale from intrinsic delays expected in standard blazar flares. We first characterised the intrinsic time delays in BL Lacs and flat-spectrum radio quasars in standard one-zone time-dependent synchrotron self-Compton or external Compton models, during flares produced by particle acceleration and cooling processes. We simulated families of flares with both intrinsic and external LIV-induced energy-dependent delays. Discrimination between intrinsic and LIV delays is then investigated in two different ways. A technique based on Euclidean distance calculation between delays obtained in the synchrotron and in the inverse-Compton spectral bumps is used to assess their degree of correlation. A complementary study is performed using spectral hardness versus intensity diagrams in both energy ranges. We show that the presence of non-negligible LIV effects, which essentially act only at very high energy (VHE), can drastically reduce the strong correlation expected between the X-ray and the VHE gamma-ray emission in leptonic scenarios. The LIV phenomenon can then be hinted at measuring the Euclidean distance $d_ E $ from simultaneous X-ray and gamma-ray flare monitoring. Large values of minimum distance $d_ E,min $ would directly indicate the influence of non-intrinsic time delays possibly due to LIV in SSC flares. LIV effects can also significantly modify the VHE hysteresis patterns in hardness-intensity diagrams and even change their direction of rotation compared to the X-ray behaviour. Both observables could be used to discriminate between LIV and intrinsic delays, provided high-quality flare observations are available.

Constraints on Lorentz invariance violation from the extraordinary Mrk 421 flare of 2014 using a novel analysis method

The Lorentz Invariance Violation (LIV), a proposed consequence of certain quantum gravity (QG) scenarios, could instigate an energy-dependent group velocity for ultra-relativistic particles. This energy dependence, although suppressed by the massive QG energy scale E_QG, expected to be on the level of the Planck energy 1.22 × 1019 GeV, is potentially detectable in astrophysical observations. In this scenario, the cosmological distances traversed by photons act as an amplifier for this effect. By leveraging the observation of a remarkable flare from the blazar Mrk 421, recorded at energies above 100 GeV by the MAGIC telescopes on the night of April 25 to 26, 2014, we look for time delays scaling linearly and quadratically with the photon energies. Using for the first time in LIV studies a binned-likelihood approach we set constraints on the QG energy scale. For the linear scenario, we set 95% lower limits E_QG>2.7×1017 GeV for the subluminal case and E_QG> 3.6 ×1017 GeV for the superluminal case. For the quadratic scenario, the 95% lower limits for the subluminal and superluminal cases are E_QG>2.6 ×1010 GeV and E_QG>2.5×1010 GeV, respectively.

Spectral Lags of 90 Swift Gamma-Ray Bursts and the Constraint on the Lorentz Invariance Violation

The arrival times of photons with different energy could be different, even when they are emitted from the same source simultaneously. Such a spectral lag is a common property among high-energy astrophysics phenomena like gamma-ray bursts (GRBs). The potential violation of the Lorentz invariance caused by quantum fluctuations in background spacetime metrics could cause the spectral lag. In this paper, we try to make a constraint on Lorentz invariance violation (LIV) with multiple energy bands light curves of GRBs. With a sample of 90 Swift GRBs with redshifts, we calculate their spectral offsets from four fixed energy bands within their source frame. With help from the cross-correlation function and kernel smooth procedure, we extract improved spectral shifts. By using these more general spectral lags, we obtain an upper limit on LIV, equivalent to a lower limit on the quantum-gravitational energy scale of E QG ≥ 2.2 × 1014GeV.

In Support of Multidimensional Frailty: A Structural Equation Model from the Canadian Positive Brain Health Now Cohort.

The objective of this study was to estimate the structure and relationships between four h ypothesized frailty dimensions (physical, emotional, cognitive, and social) and the extent to which personal and HIV-related factors and comorbidity associate with these frailty dimensions. This is a secondary analysis of an existing dataset arising from Positive Brain Health Now study (n = 856) in people aging with HIV (mean age: 52.3 ± 8.1 years). Structural equation modeling (SEM) models were applied to two cross-sections of the data: one at study entry and one at second visit, 9-month apart. Multidimensional frailty was modeled based on the combined Wilson-Cleary and International Classification of Functioning, Disability and Health framework. Four dimensions were operationalized with patient-reported and self-report measures from standardized questionnaires. The SEM model from the first visit was replicated using data from the second visit, testing measurement invariance. The proposed model showed acceptable fit at both visits (including no violation of measurement invariance). The final model for the first visit showed that sex, body mass index, HIV diagnosis pre-1997, current or nadir CD4 counts, and comorbidity did not associate with any frailty dimension; however, age (β range: 0.12-0.25), symptoms (β range: -0.35 to -0.58), and measured cognition (β range: 0.10-0.24) directly associated with all frailty dimensions. The model remained stable across the two visits. This study contributes evidence for operationalizing multidimensional frailty. Evidence-based interventions are available for many of the measures considered here, offering opportunities to improve the lives of people with frailty in the context of HIV.

Aether-electromagnetic theory and the Casimir effect

In this study, we explore the impact of an additional dimension, as proposed in Kaluza-Klein’s theory, on the Casimir effect within the context of Lorentz invariance violation (LIV), which is represented by the “aether field.” We demonstrate that the Casimir energy is directly influenced by the presence of the fifth dimension, as well as by the aether parameter. Consequently, the force between the plates is also subject to variations of these parameters. Furthermore, we examine constraints on both the size of the extra dimension and the aether field parameter based on experimental data. The LIV parameter can provide insights into addressing the size-related challenges in Kaluza-Klein’s theory and offers a mean to establish an upper limit on the size of the extra dimension. This helps to rationalize the difficulties associated with its detection in current experiments. Published by the American Physical Society 2024

Studying Factorial Invariance With Nominal Items: A Note on a Latent Variable Modeling Procedure

A latent variable modeling procedure for studying factorial invariance and differential item functioning for multi-component measuring instruments with nominal items is discussed. The method is based on a multiple testing approach utilizing the false discovery rate concept and likelihood ratio tests. The procedure complements the Revuelta, Franco-Martinez, and Ximenez approach to factorial invariance examination, and permits localization of individual invariance violations. The outlined method does not require the selection of a reference observed variable and is illustrated with empirical data.

Frequency- and polarization-dependent lensing of gravitational waves in strong gravitational fields

The propagation of gravitational waves can be described in terms of null geodesics by using the geometrical optics approximation. However, at large but finite frequencies the propagation is affected by the spin-orbit coupling corrections to geometrical optics, known as the gravitational spin Hall effect. Consequently, gravitational waves follow slightly different frequency- and polarization-dependent trajectories, leading to dispersive and birefringent phenomena. We study the potential for detecting the gravitational spin Hall effect in hierarchical triple black hole systems, consisting of an emitting binary orbiting a more massive body acting as a gravitational lens. We calculate the difference in time of arrival with respect to the geodesic propagation and find that it follows a simple power-law dependence on frequency with a fixed exponent. We calculate the gravitational spin Hall-corrected waveform and its mismatch with respect to the original waveform. The waveform carries a measurable imprint of the strong gravitational field if the source, lens, and observer are sufficiently aligned, or for generic observers if the source is close enough to the lens. We present constraints on dispersive time delays from GWTC-3, translated from limits on Lorentz invariance violation. Finally, we address the sensitivity of current and future ground detectors to dispersive lensing. Our results demonstrate that the gravitational spin Hall effect can be detected, providing a novel probe of general relativity and the environments of compact binary systems. Published by the American Physical Society 2024

Effects on neutrino propagation in space-time foam of D-branes revisited

Neutrinos from the cosmos have proven to be ideal for probing the nature of space-time. Previous studies on high-energy events of IceCube suggested that some of these events might be gamma-ray burst neutrinos, with their speeds varying linearly with their energy, implying also the coexistence of subluminal and superluminal propagation. However, a recent reanalysis of the data, incorporating revised directional information, reveals stronger signals that neutrinos are actually being slowed down compared to previous suggestion of neutrino speed variation. Thus, it is worth discussing its implications for the brane/string inspired framework of space-time foam, which has been used to explain previous observations. We revisit effects on neutrino propagation from specific foam models within the framework, indicating that the implied violation of Lorentz invariance could necessarily cause the neutrino to decelerate. We therefore argue that this sort of model is in agreement with the updated phenomenological indication just mentioned. An extended analysis of the revised IceCube data will further test these observations and stringy quantum gravity.