Invariance Violation Research Articles

A novel energy reconstruction method for the MAGIC stereoscopic observation

We report the successful development of a novel methodology of energy reconstruction for very high energy gamma rays detected with Imaging Atmospheric Cherenkov Telescopes (IACTs). This methodology, based on the machine learning algorithm Random Forest, and named RF-Erec, has been adjusted for being used with data from the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) stereo telescope system, which is a worldwide leading instrument for gamma-ray astronomy in the energy range from about 20GeV to beyond 100TeV.The RF-Erec has been evaluated using different realistic scenarios with Monte Carlo simulated data and real observations from the Crab Nebula (the standard candle for the VHE gamma-ray community). This new methodology has been validated by the MAGIC software board, and it is implemented and ready-to-use in the MAGIC Analysis and Reconstruction Software (MARS). This new methodology, validated by the MAGIC software board, has been implemented and is ready for use in the MAGIC Analysis and Reconstruction Software (MARS). We demonstrate that, in comparison to the previous energy reconstruction methodology for MAGIC data, which relied on Look-Up-Tables (LUTs- Erec) and has been utilized in over 100 scientific publications over the last decade, RF-Erec significantly enhances the energy reconstruction of gamma rays. This improvement extends the capabilities of the MAGIC telescopes.Specifically, when quantifying the energy resolution with the width of a Gaussian fitted to the error distribution (resolution-σ), the RF-Erec energy resolution-σ is 20% at 100 GeV and 11% above 1 TeV for Zenith distances (Zd) below 35 degrees, while it is 20% at 1TeV and 13% above 10TeV for Zd above 55 degrees. For a wide range of the observable energies, the improvement of energy resolution-σ, compared to LUTs-Erec, reaches roughly a factor of two, and the improvement is even larger for high Zd observations. Differently to many other works in the literature, our evaluation also considers the energy dispersion and the actual energy migration of events, where RF-Erec improves the performance of LUTs-Erec by factors of a few. The manuscript also demonstrates the importance of energy reconstruction methods with a small energy migration in order to prevent the appearance of artificial spectral features. These artifacts are particularly important at the high end of the gamma-ray spectra, where a few extra high-energy photons could have dramatic consequences for studies related to the EBL attenuation, Lorentz invariance violation, or searches for Axion-like-particles.

Probing for Lorentz Invariance Violation in Pantheon Plus Dominated Cosmology

The Hubble tension in cosmology is not showing signs of alleviation and thus, it is important to look for alternative approaches to it. One such example would be the eventual detection of a time delay between simultaneously emitted high-energy and low-energy photons in gamma-ray bursts (GRB). This would signal a possible Lorentz Invariance Violation (LIV) and in the case of non-zero quantum gravity time delay, it can be used to study cosmology as well. In this work, we use various astrophysical datasets (BAO, Pantheon Plus and the CMB distance priors), combined with two GRB time delay datasets with their respective models for the intrinsic time delay. Since the intrinsic time delay is considered the largest source of uncertainty in such studies, finding a better model is important. Our results yield as quantum gravity energy bound EQG≥1017 GeV and EQG≥1018 GeV respectively. The difference between standard approximation (constant intrinsic lag) and the extended (non-constant) approximations is minimal in most cases we conside. However, the biggest effect on the results comes from the prior on the parameter cH0rd, emphasizing once again that at current precision, cosmological datasets are the dominant factor in determining the cosmology. We estimate the energies at which cosmology gets significantly affected by the time delay dataset.

Algebraic Localization–Delocalization Phase Transition in Moving Potential Wells on a Lattice

AbstractThe localization and scattering properties of potential wells or barriers uniformly moving on a lattice are strongly dependent on the drift velocity, owing to a violation of the Galilean invariance of the discrete Schrödinger equation. Here a type of localization–delocalization phase transition of algebraic type is unraveled, which does not require any kind of disorder and arises when a power‐law potential well drifts fast on a lattice. While for an algebraic exponent α lower than the critical value dynamical delocalization is observed, for asymptotic localization, corresponding to asymptotic frozen dynamics, is instead realized. At the critical phase transition point an oscillatory dynamics is found, corresponding to Bloch oscillations. An experimentally accessible photonic platform for the observation of the predicted algebraic phase transition, based on light dynamics in synthetic mesh lattices, is suggested.

Assessing experiences with discrimination in multiple social groups: invariance analysis of the Explicit Discrimination Scale in university students

This study evaluated the ability of the Explicit Discrimination Scale (EDS) to produce comparable estimates among respondents according to gender, color/race, and socioeconomic status. Analysis was based on data from two studies with students from Brazilian public universities. An abridged version of the EDS with eight items was evaluated by the alignment method. Findings indicated violation of invariance between color/race and gender groups. Reports of discriminatory experiences had better comparability between socioeconomic status strata. This study showed that EDS should be used with caution, especially to compare discrimination estimates between respondents of different colors/races and genders. The observed violation of invariance reinforces the need for additional research examining whether such a scenario persists in larger and more diverse samples from Brazil.

Measurement and Construct-Level Invariance of the Revised Child Anxiety and Depression Scale (RCADS)

Abstract: Measurement and construct-level invariance of the Dutch Revised Child Anxiety and Depression Scale’s test scores (RCADS) across gender and ethnic (minority) backgrounds of the four largest ethnic groups of children living in the Netherlands (i.e., native Dutch; Moroccan; Turkish; or Surinamese/Antillean) was evaluated. Symptoms of generalized anxiety disorder, social phobia, separation anxiety disorder, panic disorder, obsessive-compulsive disorder, and major depressive disorder were rated by 2,679 mainstream elementary schoolchildren ( Mage = 10.61). Results from discrete multiple-group confirmatory factor analyses showed that factor means were generally insensitive to gender bias. However, moderate violations of measurement invariance between native Dutch and the three ethnic minority groups were found for social phobia, panic disorder, and separation anxiety disorder symptoms. Girls had higher mean levels on all RCADS subscales compared to boys. Furthermore, with a few exceptions, children from ethnic minority groups reported higher levels of symptoms of panic disorder, generalized anxiety disorder, and obsessive-compulsive disorder compared to native Dutch children. Scores derived from the RCADS are largely comparable between elementary school boys and girls, but for three out of six subscales, caution is warranted when comparing mean level differences of native Dutch children with children of Turkish, Moroccan, and Surinamese/Antillean ethnic backgrounds.

Spontaneous and Explicit Spacetime Symmetry Breaking in Einstein–Cartan Theory with Background Fields

Explicit and spontaneous breaking of spacetime symmetry under diffeomorphisms, local translations, and local Lorentz transformations due to the presence of fixed background fields is examined in Einstein–Cartan theory. In particular, the roles of torsion and violation of local translation invariance are highlighted. The nature of the types of background fields that can arise and how they cause spacetime symmetry breaking is discussed. With explicit breaking, potential no-go results are known to exist, which if not evaded lead to inconsistencies between the Bianchi identities, Noether identities, and the equations of motion. These are examined in detail, and the effects of nondynamical backgrounds and explicit breaking on the energy–momentum tensor when torsion is present are discussed as well. Examples illustrating various features of both explicit and spontaneous breaking of local translations are presented and compared to the case of diffeomorphism breaking.

Separation of pair and single top quark production in tWb-associated final state using a neural network

The paper presents a method for separating the contribution of pair and single top quark production in tWb-associated final state using a neural network. The proposed method makes possible to calculate such processes in a gauge-invariant way with fully taking into account interference contributions and dividing the phase space into single-resonant and double-resonant regions, which is necessary to increase the accuracy of the search for possible deviations from the predictions of the Standard Model in these processes. To train the neural network, the optimized set of observables is used to separate single-resonance and double-resonance contributions to the overall process. The use of this method allows us to avoid the disadvantages inherent in the schemes used in collider physics for calculating the processes of tWb-associated top quark production with the removal of Feynman diagrams, which leads to violation of gauge invariance, or the addition of a subtraction scheme, which leads to the appearance of negative weights for the part of simulated events. The proposed method can be used to increase the efficiency of searching for deviations from the predictions of the Standard Model in the interaction of the top quark with the W boson and b quark.

Searches for beyond-standard-model physics with astroparticle physics instruments

Many instruments for astroparticle physics are primarily geared towards multi-messenger astrophysics, to study the origin of cosmic rays and to understand high-energy astrophysical processes. Since these instruments observe the Universe at extreme energies and in kinematic ranges not accessible at accelerators these experiments provide also unique and complementary opportunities to search for particles and physics beyond the standard model of particle physics. In particular, the reach of IceCube, Fermi and KATRIN to search for and constrain Dark Matter, Axions, heavy Big Bang relics, sterile neutrinos and Lorentz invariance violation will be discussed. The contents of this article are based on material presented at the Humboldt–Kolleg ‘Clues to a mysterious Universe—exploring the interface of particle, gravity and quantum physics’ in June 2022. This article is part of the theme issue ‘The particle-gravity frontier’.

Investigating the Lorentz invariance violation effect using different cosmological backgrounds

Familiar concepts in physics, such as Lorentz symmetry, are expected to be broken at energies approaching the Planck energy scale as predicted by several quantum-gravity theories. However, such very large energies are unreachable by current experiments on Earth. Current and future Cherenkov telescope facilities may have the capability to measure the accumulated deformation from Lorentz symmetry for photons traveling over large distances via energy-dependent time delays. One of the best natural laboratories to test Lorentz invariance violation (LIV) signatures are gamma-ray bursts. The calculation of time delays due to the LIV effect depends on the cosmic expansion history. In most of the previous works calculating time lags due to the LIV effect, the standard ΛCDM (or concordance) cosmological model is assumed. In this paper, we investigate whether the LIV signature is significantly different when assuming alternatives to the ΛCDM cosmological model. Specifically, we consider cosmological models with a non-trivial dark-energy equation of state (EoS) (), such as the standard Chevallier–Polarski–Linder parameterization, the quadratic parameterization of the dark-energy EoS, and the Pade parameterizations. We find that the relative difference in the predicted time lags is small, of the order of at most a few percent, and thus likely smaller than the systematic errors of possible measurements currently or in the near future.

Inhibition of non-Hermitian topological phase transitions in sliding photonic quasicrystals.

Non-Hermitian (NH) quasicrystals have been a topic of increasing interest in current research, particularly in the context of NH topological physics and materials science. Recently, it has been suggested and experimentally demonstrated using synthetic photonic lattices that a class of NH quasicrystals can feature topological spectral phase transitions. Here we consider a NH quasicrystal with a uniformly-drifting (sliding) incommensurate potential and show that, owing to violation of Galilean invariance, the topological phase transition is washed out and the quasicrystal is always in the delocalized phase with an entirely real-energy spectrum. The results are illustrated by considering quantum walks in synthetic photonic lattices.

Bayesian evidence for spectral lag transition due to Lorentz invariance violation for 32 Fermi/GBM Gamma-ray bursts

We use the spectral lag data of 32 long GRBs detected by Fermi/GBM, which has been recently collated in Liu et al. (2022) to quantify the statistical significance of a transition in the spectral lag data based on Lorentz invariance violation (LIV) (for both sub-luminal and super-luminal propagation) using Bayesian model selection. We use two different parametric functions to model the null hypothesis of only intrinsic emission: a smooth broken power law model (SBPL) (proposed in Liu et al. (2022)) as well as a simple power law model, which has been widely used before in literature. We find that for sub-luminal propagation, when we use the SBPL model as the null hypothesis, five GRBs show “decisive evidence” based on Jeffreys' scale for linear LIV and quadratic LIV. When we use the simple power-law model as the null hypothesis, we find that 10 and 9 GRBs show Bayesian “decisive evidence” for linear and quadratic LIV, respectively. However these results should not be construed as evidence for LIV, as they would be in conflict with the most stringent upper limits. When we did a test for super-luminal LIV, we find that only four and two GRBs show Bayesian “decisive evidence” for linear and quadratic LIV, respectively, assuming a simple power law for the intrinsic emission. When we use the SBPL model, one GRB shows Bayesian “decisive evidence” for linear and quadratic LIV. This underscores the importance of adequately modeling the intrinsic emission while obtaining constraints on LIV using spectral lags, since inadequate modeling could masquerade as a signature of LIV.

Measuring the development of social-emotional competence using behavioral rating scales in the context of school-based social and emotional learning

Universal progress monitoring of student social-emotional competence (SEC) has increasingly been adopted as part of regular educational practices in the context of schoolwide social and emotional learning (SEL). However, an evidence base has not yet been established on the extent of SEC growth to expect across school years under a multiyear school-based SEL implementation setting. An essential but often overlooked prerequisite when measuring student SEC growth is to examine longitudinal measurement invariance of the assessment tools. To address these gaps, this study first tested the longitudinal measurement invariance of a widely-used teacher-completed behavioral rating scale, and then examined the average SEC growth trajectory of elementary school students under a three-year SEL practice initiative. The data involve six waves of teacher ratings of student SEC, collected for three consecutive years using the DESSA-Mini (N = 1146; Grades K-2 at baseline). Using longitudinal confirmatory factor analysis, this study found no violations of measurement invariance across all six occasions, suggesting that the same construct of SEC was measured across different seasons, raters, and grade levels. Then, using second-order latent growth modeling that did not impose any predetermined shape of growth, this study found that (a) student SEC increased within each year, (b) student SEC decreased over each summer by about a half of the yearly gain, and (c) the rate of yearly growth gradually decreased across years. Implications and limitations of these findings are discussed with suggestions for future research and practices.

Fermions dynamic equation with Lorentz invariance violation and the corrected Hawking temperature in arbitrarily accelerating black hole* *Supported by the National Natural Science Foundation of China under Grant No. U2031121.

Containing Lorentz invariance violation (LIV), a new form of the fermions dynamic equation under the background of the curved space-time of the arbitrarily accelerating black hole, is studied. Firstly, we consider the new form of the fermions dynamic equation with arbitrary spin containing LIV in curved space-time, and research the fermions dynamic equation with spin containing LIV. On this basis, according to the semi-classical theory and black hole quantum tunneling radiation theory, the quantum tunneling radiation of the arbitrarily accelerating Kinnersly black hole is modified correctly, and the corrected physical quantities such as black hole temperature and quantum tunneling rate are deeply discussed. The fermions dynamic equation with arbitrary spin in the arbitrarily accelerating black hole space-time and its solution are explained in detail. In order to further obtain the correction effect of the Planck scale, this article considers beyond the semi-classical theory and further obtains new expressions of the black hole temperature and tunneling radiation rate.

Different rules for binocular combination of luminance flicker in cortical and subcortical pathways

How does the human brain combine information across the eyes? It has been known for many years that cortical normalization mechanisms implement ‘ocularity invariance’: equalizing neural responses to spatial patterns presented either monocularly or binocularly. Here, we used a novel combination of electrophysiology, psychophysics, pupillometry, and computational modeling to ask whether this invariance also holds for flickering luminance stimuli with no spatial contrast. We find dramatic violations of ocularity invariance for these stimuli, both in the cortex and also in the subcortical pathways that govern pupil diameter. Specifically, we find substantial binocular facilitation in both pathways with the effect being strongest in the cortex. Near-linear binocular additivity (instead of ocularity invariance) was also found using a perceptual luminance matching task. Ocularity invariance is, therefore, not a ubiquitous feature of visual processing, and the brain appears to repurpose a generic normalization algorithm for different visual functions by adjusting the amount of interocular suppression.

Different rules for binocular combination of luminance flicker in cortical and subcortical pathways.

How does the human brain combine information across the eyes? It has been known for many years that cortical normalization mechanisms implement 'ocularity invariance': equalizing neural responses to spatial patterns presented either monocularly or binocularly. Here, we used a novel combination of electrophysiology, psychophysics, pupillometry, and computational modeling to ask whether this invariance also holds for flickering luminance stimuli with no spatial contrast. We find dramatic violations of ocularity invariance for these stimuli, both in the cortex and also in the subcortical pathways that govern pupil diameter. Specifically, we find substantial binocular facilitation in both pathways with the effect being strongest in the cortex. Near-linear binocular additivity (instead of ocularity invariance) was also found using a perceptual luminance matching task. Ocularity invariance is, therefore, not a ubiquitous feature of visual processing, and the brain appears to repurpose a generic normalization algorithm for different visual functions by adjusting the amount of interocular suppression.

Universal horizons and black hole spectroscopy in gravitational theories with broken Lorentz symmetry

The violation of Lorentz invariance (LI) in gravitational theories, which allows superluminal propagations, dramatically alters the causal structure of the spacetime and modifies the notion of black holes (BHs). Instead of metric horizons, now universal horizons (UHs) define the boundaries of BHs, within which a particle cannot escape to spatial infinities even with an infinitely large speed. Then, a natural question is how the quasi-normal modes (QNMs) of a BH are modified, if one considers the UH as its causal boundary. In this paper, we study in detail this problem in Einstein–Aether theory, a vector-tensor theory that violates LI but yet is self-consistent and satisfies all observations to date. Technically, this poses several challenges, including singularities of the perturbation equations across metric horizons and proper identifications of ingoing modes at UHs. After overcoming these difficulties, we show that the QNMs of the Schwarzschild BH, also a solution of Einstein–Aether theory, consist of two parts, the metric and aether parts. The QNMs of the metric perturbations are quite similar to those obtained in general relativity and are consistent with current observations of gravitational waves. But the ones from aether perturbations are different, and our numerical studies indicate that they are even not stable. The latter is consistent with our previous studies, which showed that the stealth Schwarzschild BH suffers a Laplacian instability along the angular direction. The method and techniques developed in this paper can be applied to the studies of QNMs in other theories of gravity with broken LI.

Measurement Invariance of the Neurobehavioral Symptom Inventory in Male and Female Million Veteran Program Enrollees Completing the Comprehensive Traumatic Brain Injury Evaluation.

This study evaluated measurement invariance across males and females on the Neurobehavioral Symptom Inventory (NSI) in U.S. military veterans enrolled in the VA Million Veteran Program. Participants (N = 17,059; males: n = 15,450; females: n = 1,609) included Veterans who took part in the VA Traumatic Brain Injury (TBI) Screening and Evaluation Program and completed the NSI. Multiple-group confirmatory factor analyses investigated measurement invariance of the NSI 4-factor model. The configural (comparative fit index [CFI] = 0.948, root mean square error of approximation [RMSEA] = 0.060) and metric (CFI = 0.948, RMSEA = 0.058) invariance models showed acceptable fit. There was a minor violation of scalar invariance (Δχ2 = 232.50, p < .001); however, the degree of noninvariance was mild (ΔCFI = -0.002, ). Our results demonstrate measurement invariance across sex, suggesting that the NSI 4-factor model can be used to accurately assess symptoms in males and females following TBI. Findings highlight the importance of considering validity of measurement across study groups to increase confidence that a measure is interpreted similarly by respondents from different subgroups.

Comparing MIMIC and MIMIC-interaction to Alignment Methods for Investigating Measurement Invariance concerning a Continuous Violator

Measurement invariance holds when a latent construct is measured in the same way across different levels of background variables (continuous or categorical) while controlling for the true value of that construct. Using Monte Carlo simulation, this paper compares the multiple indicators, multiple causes (MIMIC) model and MIMIC-interaction to a novel use of alignment optimization (AO) for detecting measurement noninvariance when the violator is a continuous variable. Results showed that MIMIC and MIMIC-interaction in sequential likelihood ratio tests and Wald tests with a Bonferroni correction provided a good balance between identifying invariant and noninvariant (linear violations) items when n ≥ 500 in terms of classification accuracy (CA). AO (CA ≥ .86) was as competitive as MIMIC and MIMIC-interaction to linear invariance violations but was far better under nonlinear quadratic violations when n ≥ 1,000 (i.e., 100 per group for 10 groups).

Impact of cosmology on Lorentz Invariance Violation constraints from GRB time-delays

Putting constraints on a possible Lorentz Invariance Violation (LIV) from astrophysical sources such as gamma-ray bursts (GRBs) is essential for finding evidences of new theories of quantum gravity (QG) that predict an energy-dependent speed of light. This search has its own difficulties, so usually, the effect of the cosmological model is understudied, with the default model being a fixed-parameters ΛCDM.In this work, we use various astrophysical datasets to study the effect of a number of dark energy models on LIV constraints. To this end, we combine two public time-delay (TD) GRB datasets with the supernovae Pantheon dataset, several measurements of angular baryonic acoustic oscillations (BAO), the cosmic microwave background (CMB) distance prior and an optional GRB or quasars dataset. For the LIV parameter α, we find the expected from previous works average value of , corresponding to GeV for both TD datasets, with the second one being more sensitive to the cosmological model. The cosmology results in a minimum 20% deviation in our constraints on the energy. Interestingly, adding the TD points makes the DE models less-preferable statistically and shifts the value of the parameter down, making it smaller than the expected value. We observe that possible LIV measurements critically depend on the transparency of the assumptions behind the published data concerning cosmology, and taking this into account may be an important contribution in the case of possible detection.

Magnetic corrections to the fermionic Casimir effect in Horava-Lifshitz theories

In this paper, I investigate the effect of a magnetic field on the Casimir effect due to a massless and charged fermion field that violates Lorentz invariance according to the Horava-Lifshitz theory. I focus on the case of a fermion field that obeys MIT bag boundary conditions on a pair of parallel plates. I carry out this investigation using the [Formula: see text]-function technique that allows me to obtain Casimir energy and pressure in the presence of a uniform magnetic field orthogonal to the plates. I investigate the cases of the parameter associated with the violation of Lorentz invariance being even or odd and the cases of weak and strong magnetic field, examining all possible combinations of the above quantities. In all cases I obtain simple and very accurate analytic expressions of the magnetic field-dependent Casimir energy and pressure.