Covariant Approach Research Articles

1+1+2 covariant formulation of light propagation in spacetime

We present a covariant approach to the problem of light beam propagation in a spacetime. We develop our considerations within the framework of classical geometric optics in general relativity. Using the concept of a screen surface orthogonal to the observer velocity and to the bundle of geodesics, we introduce covariant four-dimensional definitions for Sachs and Jacobi optical fields and for the area distance. Then we give relationships between them and derive their propagation equations together with initial conditions for these equations. Ultimately, for practical use, we transform the resulting formulas into the redshift-dependent form.

New higher derivative action for tensor multiplet in mathcal{N} = 2 conformal supergravity in four dimensions

We will use the covariant superform approach to develop a new density formula for mathcal{N} = 2 conformal supergravity which is based on a fermionic multiplet whose lowest component is a dimension-5/2 spinor. We will show that this density formula admits an embedding of the real scalar multiplet of [1]. Upon using the embedding of the tensor multiplet into the real scalar multiplet, we will construct a new higher derivative action of the tensor multiplet in mathcal{N} = 2 conformal supergravity.

Form factors for the Nucleon-to-Roper electromagnetic transition at large-Q2

We report on a recent calculation of all Roper-related electromagnetic transtions form factors, cov ering the range of energies that next-to-come planned experiments are expected to map. Direct reliable cal culations were performed, within a Poincaré covariant approach of the three-body bound-state problem, up to Q2/m2N=6; approximated then by applying the Schlessinger point method and the results eventually extended up to Q2/m2N ≃12 via analytic continuation.

Robust mixed source localization in WSN using swarm intelligence algorithms

Passive localization and classification algorithms for mixed near-field and far-field sources have mainly been investigated for antenna arrays with regular or symmetrical geometry. However, these algorithms may not be applicable to wireless sensor networks, where spatially distributed sensor nodes form an array of random geometry. This paper proposes squared error norm of residual fitting error matrix (SRFEM) cost function for mixed source localization, which does not place any constraint on the geometry of antenna array. The proposed cost function is optimized using computationally simple swarm intelligence (SI) algorithms. Convergence performance of three SI algorithms, i.e., particle swarm optimization, Whale optimization, and Grey Wolf optimization is investigated to obtain estimates of the source location parameters with a minimal number of iterations or computational complexity. In order to provide robustness for the SRFEM cost function, this paper proposes an impulse denoising technique based on the long-short term memory recurrent neural network (LSTM-RNN). Simulation results confirm that, in the presence of AWGN, the proposed SRFEM cost function outperforms existing techniques based on the uniform linear array and approaches the theoretical Cramer-Rao lower bound even for a fewer number of snapshots. Further, simulation analysis also reveals that LSTM-RNN provides better mixed localization performance under impulse noise as compared to the bounded noise covariance approach at high signal-to-noise values.

Form factors of V\u2032 \u2192 V\u2033 transition within the light-front quark models

In this paper, we calculate the matrix element and form factors of vector-to- vector (VI→ VII) transition within the standard light-front (SLF) and covariant light- front (CLF) quark models (QMs), and investigate the self-consistency and Lorentz covari- ance of the CLF QM within two types of correspondences between the manifest covariant Bethe-Salpeter approach and the LF approach. The zero-mode and valence contributions to the form factors of VI→ VII transition in the CLF QM and their relation to the SLF results are analyzed, and the main conclusions obtained via the decay constants of vector and axial-vector mesons and the form factors of P → V transition in the previous works are confirmed again. Furthermore, we present our numerical predictions for the form factors of c → (q, s) (q = u, d) induced D*→ (K*, ρ), D∗→ (ϕ, K*), J/Ψ → left({D}_s^{ast },{D}^{ast}right) , {B}_c^{ast}to left({B}_s^{ast },{B}^{ast}right) transitions and b → (c, s, q) induced B∗ → (D∗, K∗, ρ), {B}_s^{ast}to left({D}_s^{ast },phi, {K}^{ast}right) , {B}_c^{ast}to left(J/varPsi, {D}_s^{ast },{D}^{ast}right),varUpsilon (1S)to left({B}_c^{ast },{B}_s^{ast },{B}^{ast}right) the relevant phenomenological studies of meson decays.

Gauge covariant approach to the electroweak interactions of mesons in the Nambu–Jona-Lasinio model with spin-1 states

An extended Nambu–Jona-Lasinio (NJL) model with chiral group [Formula: see text] and spin-0 and spin-1 four quark interactions is used to develop the gauge covariant approach to the diagonalization of the [Formula: see text] mixing in the presence of electroweak forces. This allows for manifestly gauge covariant description of both the non-anomalous and anomalous parts of the effective Lagrangian. It is shown that in the non-anomalous sector the theory is equivalent to the standard non-covariant approach.

Building a path-integral calculus: a covariant discretization approach

Path integrals are a central tool when it comes to describing quantum or thermal fluctuations of particles or fields. Their success dates back to Feynman who showed how to use them within the framework of quantum mechanics. Since then, path integrals have pervaded all areas of physics where fluctuation effects, quantum and/or thermal, are of paramount importance. Their appeal is based on the fact that one converts a problem formulated in terms of operators into one of sampling classical paths with a given weight. Path integrals are the mirror image of our conventional Riemann integrals, with functions replacing the real numbers one usually sums over. However, unlike conventional integrals, path integration suffers a serious drawback: in general, one cannot make non-linear changes of variables without committing an error of some sort. Thus, no path-integral based calculus is possible. Here we identify which are the deep mathematical reasons causing this important caveat, and we come up with cures for systems described by one degree of freedom. Our main result is a construction of path integration free of this longstanding problem, through a direct time-discretization procedure.

Influence of Activity Ratio to The Performance of Financial Statement of Badan BPJS Ketenagakerjaan Indonesia

In this study, the writer will analyze the influence of activity ratios on the performance of BPJS Ketenagakerjaan Agency's financial statements with the linear regression model approach. In this research, the author uses the measurement method of Standard Deviation, Historical Simulation and Variance Covariance approaches . The time span used in this research is from 2014 to 2018. This study is to find out how much influence the ratio of activity to return on assets on the BPJS ketenagakerjaan.

A Brief Review on Canonical Loop Quantum Gravity: The Kinematical Part

In this article, we briefly review the kinematical part of canonical loop quantum gravity. This article starts with tetradic formulation of gravity both in the covariant approach and canonical approach. The next step is to introduce Ashtekar new variables and to apply the Dirac canonical quantization procedure of gravity. By the holonomy representation, one obtains the loop representation of quantum gravity.

Quantum aspects of antisymmetric tensor field with spontaneous Lorentz violation

We study the quantization of a simple model of antisymmetric tensor field with spontaneous Lorentz violation in curved spacetime. We evaluate the 1-loop corrections at first order of metric perturbation, using a general covariant effective action approach. We revisit the issue of quantum equivalence, and find that it holds for non-Lorentz-violating modes but breaks down for Lorentz violating modes.

Large enhancement of conductivity in Weyl semimetals with tilted cones: Pseudorelativity and linear response

We study the conductivity of two-dimensional graphene-type materials with tilted cones as well as their three-dimensional Weyl counterparts and show that a covariant quantum Boltzmann equation is capable of providing an accurate description of these materials' transport properties. The validity of the covariant Boltzmann approach is corroborated by calculations within the Kubo formula. We find a strong anisotropy in the conductivities parallel and perpendicular to the tilt direction upon increase of the tilt parameter $\eta$, which can be interpreted as the boost parameter of a Lorentz transformation. While the ratio between the two conductivities is $\sqrt{1-\eta^2}$ in the two-dimensional case where only the conductivity perpendicular to the tilt direction diverges for $\eta\rightarrow 1$, both conductivities diverge in three-dimensional Weyl semimetals, where $\eta=1$ separates a type-I (for $\eta<1$) from a type-II Weyl semimetal (for $\eta>1$).

Covariant approach to magnetic anisotropy

In view of recent experiments, the determination of magnetic anisotropy (MA) is revisited, thus leading to unexpected relations between the pertinent tensors. The sudden perturbation of the preferential magnetic direction triggers magnetization dynamics, which can be traced on the femtosecond timescale. Modeling this process provides indirect information on magnetic anisotropy. In magnetic molecular systems, the interplay between the zero-field splitting given by the $D$ tensor and the Zeeman interaction given by the $G$ tensor can be measured spectroscopically, likewise indirectly providing information on MA, but never fully uncovering these tensors. Here, a theory that bridges the gap between the physical experiments, the microscopic mechanisms, and the effective models is established. Expressions for the magnetic anisotropy in terms of the $D$ and $G$ tensors are derived in a covariant form. A minimal experiment where these parameters can be determined is proposed. In particular, by means of the Hellmann-Feynman theorem, we are able to account for the mutual orientation of the principal axes of the $G$ and $D$ tensors, which is an important effect for molecular magnets.

The Preference for Joint Attributions Over Contrast-Factor Attributions in Causal Contrast Situations.

A current issue about causal attribution is whether people take simple contrast-factor attributions or complex joint attributions in contrast situations. For example, a stone does not dissolve in water and a piece of salt dissolves in water. That the piece of salt dissolves in water is due to: (A) the influence of the piece of salt; (B) the influence of the water; (C) the joint influence of the piece of salt and the water. We propose a mechanism-based sufficiency account for such questions. It argues that causal attributions are guided by mechanism-based explanatory sufficiency, and people prefer a mechanism-based attribution with explanatory sufficiency. This account predicts the sufficient joint attribution (the C option), whereas the conventional covariation approach predicts the contrast-factor attribution (the A option). Two experiments investigated whether contrast situations affect causal attributions for compound causation with explicit mechanism information and simple causation without explicit mechanism information, respectively. Both experiments found that in both the presence and absence of contrast situations, the majority of participants preferred sufficient joint attributions to simple contrast-factor attributions regardless of whether explicit mechanism information was present, and contrast situations did not affect causal attributions. These findings favor the mechanism-based sufficiency account rather than the covariation approach and the complexity account. In contrast situations, the predominance of joint attributions implies that explanatory complexity affects causal attributions by the modulation of explanatory sufficiency, and people prefer mechanism-based joint attributions that provide sufficient explanations for effects. The present findings are beyond the existing approaches to causal attributions.

Replication of ecologically relevant hydrological indicators following a modified covariance approach to hydrological model parameterization

Abstract. Hydrological models can be used to assess the impact of hydrologic alteration on the river ecosystem. However, there are considerable limitations and uncertainties associated with the replication of ecologically relevant hydrological indicators. Vogel and Sankarasubramanian's 2003 (Water Resources Research) covariance approach to model evaluation and parameterization represents a shift away from algorithmic model calibration with traditional performance measures (objective functions). Using the covariance structures of the observed input and simulated output time series, it is possible to assess whether the selected hydrological model is able to capture the relevant underlying processes. From this plausible parameter space, the region of parameter space which best captures (replicates) the characteristics of a hydrological indicator may be identified. In this study, a modified covariance approach is applied to five hydrologically diverse case study catchments with a view to replicating a suite of ecologically relevant hydrological indicators identified through catchment-specific hydroecological models. The identification of the plausible parameter space (here n≈20) is based on the statistical importance of these indicators. Evaluation is with respect to performance and consistency across each catchment, parameter set, and the 40 ecologically relevant hydrological indicators considered. Timing and rate of change indicators are the best and worst replicated respectively. Relative to previous studies, an overall improvement in consistency is observed. This study represents an important advancement towards the robust application of hydrological models for ecological flow studies.

U-Dualities in Type II and M-Theory: A Covariant Approach

In this review, a short description of exceptional field theory and its application is presented. Exceptional field theories provide a U-duality covariant description of supergravity theories, allowing addressing relevant phenomena, such as non-geometricity. Some applications of the formalism are briefly described.

Light pseudoscalar meson and doubly charmed baryon scattering lengths with heavy diquark-antiquark symmetry

We adopt the heavy baryon chiral perturbation theory (HBChPT) to calculate the scattering lengths of $\phi B_{cc}^{(*)}$ up to $\mathcal{O}(p^3)$, where $\phi$ is the pseudoscalar mesons. The recoil effect and the mass splitting between the spin-$1\over 2$ and spin-$3\over 2$ doubly charmed baryons are included. In order to give the numerical results, we construct the chiral Lagrangians with heavy diquark-antiquark (HDA) symmetry in a formally covariant approach. Then, we relate the low energy constants (LECs) of the doubly charmed baryons to those of $D^{(*)}$ mesons. The LECs for the $\phi D^{(*)}$ scattering are estimated in two scenarios, fitting lattice QCD results and using the resonance saturation model. The chiral convergence of the first scenario is not good enough due to the the large strange quark mass and the presence of the possible bound states, virtual states and resonance. The final results for two scenarios are consistent with each other. The interaction for the $[\pi\Xi^{(*)}_{cc}]^{(1/2)}$, $[K\Xi^{(*)}_{cc}]^{(0)}$, $[K\Omega^{(*)}_{cc}]^{(1/2)}$, $[\eta\Xi^{(*)}_{cc}]^{(1/2)}$, $[\eta\Omega^{(*)}_{cc}]^{(0)}$ and $[\bar{K}\Xi^{(*)}_{cc}]^{(0)}$ channels are attractive. The most attractive channel $[\bar{K}\Xi^{(*)}_{cc}]^{(0)}$ may help to form the partner states of the $D_{s0}^*(2317)$ ($D_{s1}(2460)$) in the doubly heavy sector.

Transdiagnostic modulation of brain networks by electroconvulsive therapy in schizophrenia and major depression

Major depressive disorder (MDD) and schizophrenia (SCZ) share neurobiological and clinical commonalities. Altered functional connectivity of large-scale brain networks has been associated with both disorders. Electroconvulsive therapy (ECT) has proven to be an effective treatment in severe forms of MDD and SCZ. However, the role of ECT on the modulation of the dynamics of brain networks is still unknown. In this study, we used resting state functional magnetic resonance imaging (rs-fMRI) to investigate functional connectivity in 16 pharmacoresistant patients with SCZ or MDD and a matched group of normal controls. Patients were scanned before and after right-sided unilateral ECT. Group spatial independent component analysis was carried out with a multiple analysis of covariance (MANCOVA) approach to estimate the effects of ECT treatment on intrinsic components (INs). Functional network connectivity (FNC) was calculated between pairs of INs. Patients had reduced connectivity within a striato-thalamic network in the thalamus as well as increased low frequency oscillations in a striatal network. ECT reduced low frequency oscillations (LFOs) on a striatal network along with increasing functional connectivity in the medial prefrontal cortex within the DMN. Following ECT treatment, the FNC of the executive network was reduced with the DMN and increased with the salience network, respectively.Our findings suggest transnosological effects of ECT on the connectivity of large-scale networks as well as at the level of their interplay. Furthermore, they support a transnosological approach for the investigation not only of the neural correlates of the disease but also of the brain mechanism of treatment of mental disorders.

Polysymplectic formulation for BF gravity with Immirzi parameter

The polysymplectic formulation of the CMPR action, which is a BF-type formulation of general relativity that involves an arbitrary Immirzi parameter, is performed. We implement a particular scheme within this covariant Hamiltonian approach to analyze the constraints that characterize the CMPR model. By means of the privileged -forms and the Poisson–Gerstenhaber bracket, inherent to the polysymplectic framework, the BF field equations associated to the CMPR action are obtained and, in consequence, the Einstein equations naturally emerge by solving the simplicity constraints of the theory. Further, from the polysymplectic analysis of the CMPR action the De Donder–Weyl Hamiltonian formulation of the Holst action is recovered, which is consistent with the Lagrangian analysis of this model as reported in the literature.

SAT-097 Weight Loss With Liraglutide 3.0 Mg Versus Placebo For Individuals Who Adhere To The Trial Drug: A Secondary Analysis From SCALE IBT

The objective of the SCALE IBT trial (NCT02963935) was to compare the weight loss of liraglutide 3.0 mg, a medication approved by the Food and Drug Administration for chronic weight management, to placebo, both in combination with 56 weeks of intensive behavior therapy (IBT) (i.e. reduced calorie intake, increased physical activity [max target: 250 mins/week], and 23 counseling sessions). The primary outcomes of the study were assessed in the intention-to-treat sample, regardless of individuals’ medication adherence. The weight loss estimated in the primary analysis, regardless of drug adherence, was 7.5% versus 4.0% for liraglutide 3.0 mg and placebo, respectively, reflecting a treatment difference favoring liraglutide 3.0 mg of 3.5% (95% CI: 1.6%; 5.3%; p=0.0003). In this pre-specified secondary analysis, we sought to determine the expected effect of liraglutide 3.0 mg on weight loss, as compared to placebo, if all randomized individuals had adhered to study drug for 56 weeks. A total of 282 individuals with obesity (BMI ≥30 kg/m2) were randomized in a 1:1 ratio to 56 weeks of IBT combined with daily injections of either liraglutide 3.0 mg or placebo. The weight loss, based on the assumption that all individuals adhered to the medication, was estimated using two different approaches. The first approach (mixed model repeated measures; MMRM) estimated the weight loss that would have been achieved if all individuals adhered to the trial drug by utilizing information from individuals still on drug after the point of a given individual’s discontinuation to provide a (counter-factual) weight change as if the individual in question had not discontinued the drug. The second (covariate) approach used a regression model to calculate the weight change of individuals with full adherence to trial drug by including adherence as a moderator of the effect of treatment condition on weight change. The MMRM approach yielded a weight loss difference of 4.6% (95% CI: 2.6%; 6.5%; p<0.0001), and the covariate approach yielded a weight loss difference of 4.6% (95% CI: 2.8%; 6.5%; p<0.0001), with both estimates favoring liraglutide 3.0 mg. As such, there was good agreement between the two statistical approaches for estimating the effect of liraglutide 3.0 mg versus placebo for individuals who adhere to trial product for 56 weeks. The estimated placebo-subtracted weight loss for liraglutide at week 56 of approximately 4.6% in medication-adherent individuals therefore indicates that underlying assumptions are robust. We believe this finding is an important supplement to the study’s primary outcome and can inform practitioners’ expectations when prescribing liraglutide 3.0 mg in combination with IBT for 56 weeks. Supported by Novo Nordisk.

Simultaneous cooling the coupled nano-mechanical resonators in the strong optomechanical coupling regime

Coupled nano-mechanical resonators (NRs) have recently attracted great attention for both practical applications and fundamental studies. As a preparation step, it is needed to cool the coupled NRs to their ground states. In this paper, we investigate the coupled mechanical resonators cooling by employing the covariance approach for the identical and nonidentical cases, special attention is paid to the strong optomechanical coupling regime. Using numerical investigations, we show that the two coupled NRs can be simultaneously cooled down to nearly the vibrational ground state with the strong optomechanical coupling with the RWA. For these reasons, our scheme may provide a new paradigm for the coherent manipulation of NRs in the strong optomechanical coupling regime.