bluuebunny/crossref_metadata_2025_split huggingface dataset:
The dual curvature tensors and dynamics of gravitomagnetic matter
Authors: Shen J.Q. 
Published: June 2022

AbstractGravitomagnetic charge that can also be referred to as the dual mass or magnetic mass is the topological charge in gravity theory. A gravitomagnetic monopole at rest can produce a stationary gravitomagnetic field. Due to the topological nature of gravitomagnetic charge, the metric of spacetime where the gravitomagnetic matter is present will be nonanalytic. In this paper both the dual curvature tensors (which can characterize the dynamics of gravitational charge/monopoles) and the antisymmetric gravitational field equation of gravitomagnetic matter are presented. We consider and discuss the mathematical formulation and physical properties of the dual curvature tensors and scalar, antisymmetric source tensors, dual spin connection (including the low‐motion weak‐field approximation), dual vierbein field as well as dual current densities of gravitomagnetic charge. It is shown that the dynamics of gravitomagnetic charge can be founded within the framework of the above dual quantities. In addition, the duality relationship in the dynamical theories between the gravitomagnetic charge (dual mass) and the gravitoelectric charge (mass) is also taken into account in the present paper.
On gravitational radiation and the energy flux of matter
Authors: Maluf J.W. , Faria F.F. 
Published: June 2022

AbstractA suitable derivative of Einstein's equations in the framework of the teleparallel equivalent of general relativity (TEGR) yields a continuity equation for the gravitational energy‐momentum. In particular, the time derivative of the total gravitational energy is given by the sum of the total fluxes of gravitational and matter fields energy. We carry out a detailed analysis of the continuity equation in the context of Bondi and Vaidya's metrics. In the former space‐time the flux of gravitational energy is given by the well known expression in terms of the square of the news function. It is known that the energy definition in the realm of the TEGR yields the ADM (Arnowitt‐Deser‐Misner) energy for appropriate boundary conditions. Here we show that the same energy definition also describes the Bondi energy. The analysis of the continuity equation in Vaidya's space‐time shows that the variation of the total gravitational energy is determined by the energy flux of matter only.
On the correspondence between a screw dislocation in gradient elasticity and a regularized vortex
Authors: Lazar M. 
Published: June 2022

AbstractWe show the correspondence between a screw dislocation in gradient elasticity and a regularized vortex. The effective Burgers vector, nonsingular distortion and stress fields of a screw dislocation and the effective circulation, smoothed velocity and momentum of a vortex are given and discussed.
Deep inside the pion. Reconciling QCD theory with data *
Authors: Bakulev A.P. , Mikhailov S.V. , Stefanis N.G. 
Published: June 2022

AbstractRecent developments in the QCD description of the pion structure are reviewed. The CLEO pion‐photon transition data analysis favors a distribution amplitude for the pion that is double‐humped but endpoint‐suppressed. After a short outline of the derivation of this amplitude from QCD sum rules with nonlocal condensates, we present the fully fledged analysis of the CLEO data prefaced by predictions for the Fγρπ form factor and commenting on the inherent theoretical uncertainties due to higher twists and NNLO perturbative corrections. We supplement our discussion by considering within QCD factorization theory, the electromagnetic pion form factor at NLO accuracy on one hand, and diffractive di‐jets production on the other, comparing our predictions with the respective experimental data from JLab and the Fermilab E791 collaboration. In all cases, the agreement is impressive.
Transversity in the chiral quark–soliton model and single spin asymmetries ***
Authors: Efremov A.V. 
Published: June 2022

AbstractA short review of single spin asymmetries in deep inelastic semi‐inclusive processes, connected with prediction of chiral quark‐soliton model for the nucleon transversity distributions, its possible theoretical understanding in the framework of QCD‐induced approach and arising difficulties is given.
Some comments on the handbag approach to wide‐angle exclusive scattering*
Authors: Kroll P. 
Published: June 2022

AbstractThe handbag mechanism for wide‐angle exclusive scattering reactions is discussed and compared to other theoretical approaches. The role of power laws in observables is critically examined. Applications of the handbag mechanism to Compton scattering and meson photoproduction are presented. The soft physics input to these processes are specific form factors which represent 1/x moments of generalized parton distributions at zero skewness. A recent analysis of the nucleon form factors provides these GPDs and, hence, the new form factors.
Recent progress in the understanding of single spin asymmetries*
Authors: Metz A. , Schlegel M. 
Published: June 2022

AbstractOver the past years a lot of progress has been made in the understanding of single spin asymmetries in hard scattering processes. We briefly review this subject, covering the non‐vanishing of time‐reversal odd parton distributions, universality of fragmentation functions, and the discovery of previously unknown time‐reversal odd parton distributions at subleading twist. Interestingly enough, all these developments were initiated by simple model calculations.
SU(3) constraints on cryptoexotic pentaquarks*
Authors: Praszałowicz M. 
Published: June 2022

AbstractWe examine SU(3) constraints on the spectrum and decay widths of cryptoexotic nucleon‐like states in antidecuplet of pentaquarks. We show that in the ideal mixing scenario the number of free matrix elements describing splittings reduces from 4 to 2. Model‐independent sum rules are derived. Using as input Θ+ and Ξ3/2 masses we show that it is difficult to interpret Roper and N*(1710) nucleon resonances as cryptoexotic pentaquarks. Large Nc limit for antidecuplet and accompanying octet in the diqaurk picture and the analogy with the soliton model is also discussed.
New insight into nuclear structure from QCD*
Authors: Thomas A.W. 
Published: June 2022

AbstractThe natural building blocks of atomic nuclei within the framework of QCD are colorless clusters of quarks, with the quantum numbers of nucleons but with internal structure modified by the local mean scalar field. A key parameter of the nucleon in such an approach is the scalar polarizability, which characterizes the response of a nucleon to an applied scalar field. This response leads naturally to 3‐, 4‐ and higher‐body effective forces, each proportional to a higher power of the scalar polarizabilty. Recent progress on the important problem of chiral extrapolation of lattice QCD data suggests a way to estimate the scalar polarizability of the nucleon, with initial results consistent with successful phenomenlogical estimates. This may be seen as a first step in the struggle to derive nuclear structure from QCD itself.
Special Relativity and Lorentz Invariance
Authors: Lämmerzahl C. 
Published: June 2022

AbstractLorentz Invariance, the main ingredient of Special Relativity, is one of the pillars of modern physics. Though Special Relativity has been replaced by General Relativity, Lorentz Invariance is still valid locally. All physical fields have to obey the laws of local Lorentz Invariance. This is also the reason why gravity within the theory of General Relativity has to be described by the metric tensor. Here we give a short introduction into the early experiments and show that they disproved the exact validity of the Galilean framework for the description of classical mechanics. After a short summary of Special Relativity, the procedure of synchronization is analyzed. It is emphasized that no experiment should depend on the synchronization. Otherwise it might be possible to simulate or compensate effects by choosing another synchronization. Accordingly, the requirement of synchronization independence is a guideline for the choice of appropriate measurable quantities which then reveal relativistic physics in an unambiguous manner. Examples are given. In a subsequent article the modern experiments implementing this kind of notions will be discussed. Also some remarks are made on the importance of Lorentz Invariance in daily life. Finally we comment on possible violations of Lorentz Invariance and their measurability.
On the interaction of mesoscopic quantum systems with gravity
Authors: Kiefer C. , Weber C. 
Published: June 2022

AbstractWe review the different aspects of the interaction of mesoscopic quantum systems with gravitational fields. We first discuss briefly the foundations of general relativity and quantum mechanics. Then, we consider the non‐relativistic expansions of the Klein‐Gordon and Dirac equations in the post‐Newtonian approximation. After a short overview of classical gravitational waves, we discuss two proposed interaction mechanisms: (i) the use of quantum fluids as generator and/or detector of gravitational waves in the laboratory, and (ii) the inclusion of gravitomagnetic fields in the study of the properties of rotating superconductors. The foundations of the proposed experiments are explained and evaluated.
Tidal dynamics of relativistic flows near black holes
Authors: Chicone C. , Mashhoon B. 
Published: June 2022

AbstractWe point out novel consequences of general relativity involving tidal dynamics of ultrarelativistic relative motion. Specifically, we use the generalized Jacobi equation and its extension to study the force‐free dynamics of relativistic flows near a massive rotating source. We show that along the rotation axis of the gravitational source, relativistic tidal effects strongly decelerate an initially ultrarelativistic flow with respect to the ambient medium, contrary to Newtonian expectations. Moreover, an initially ultrarelativistic flow perpendicular to the axis of rotation is strongly accelerated by the relativistic tidal forces. The astrophysical implications of these results for jets and ultrahigh energy cosmic rays are briefly mentioned.
The relativistic energy spectrum of hydrogen
Authors: Marsch E. 
Published: June 2022

AbstractThe method originally used by Dirac to derive his equation for a single electron is here applied to the two‐particle system electron plus proton, considered as an elementary fermion, to obtain a relativistic two‐particle Dirac‐Breit‐type Hamiltonian for the hydrogen atom. This problem can be solved exactly. Thus the relativistic energy levels of the hydrogen atom as a system bound by the static Coulomb force are obtained. The radial part of the resulting Hamiltonian operates in a four‐dimensional space describing particles, respectively antiparticles, i. e. electron and positron as well as proton and antiproton. The spin of a particle is described by the normal two‐component Pauli spinor, and therefore standard theoretical tools for dealing with angular‐momentum coupling can be exploited. The classical energy states of the hydrogen atom are retained in the appropriate non‐relativistic limit, in particular the energy levels resulting from Schrödinger's equation. The exact energy spectrum shows the expected dependence on the reduced mass of the two‐particle system, and thus describes the recoil of the core properly. The fine structure of the hydrogen spectrum arises from a dependence of the energy levels upon the quantum number of the total angular momentum.
Spontaneous emission of light from atoms: the model
Authors: Marecki P. , Szpak N. 
Published: June 2022

AbstractWe investigate (non‐relativistic) atomic systems interacting with quantum electromagnetic field (QEF). The resulting model describes spontaneous emission of light from a two‐level atom surrounded by various initial states of the QEF. We assume that the quantum field interacts with the atom via the standard, minimal‐coupling Hamiltonian, with the A2 term neglected. We also assume that there will appear at most single excitations (photons). By conducting the analysis on a general level we allow for an arbitrary initial state of the QEF (which can be for instance: the vacuum, the ground state in a cavity, or the squeezed state). We derive a Volterra‐type equation which governs the time evolution of the amplitude of the excited state. The two‐point function of the initial state of the QEF, integrated with a combination of atomic wavefunctions, forms the kernel of this equation.
Non‐Volkov solutions for a charge in a plane wave
Authors: Bagrov V. , Gitman D. 
Published: June 2022

AbstractAs it is known, a set of solutions of the Klein‐Gordon and Dirac equations with a plane‐wave field was found for the first time by Volkov. We construct new solutions of these equations different from the Volkov ones. In particular, the new solutions are characterized by quantum numbers different from Volkov solutions. In fact, our result is based on the demonstration that the transversal charge motion in a plane wave can be mapped by a special quantum transformation to transversal free particle motion. Similarly, we find new sets of solutions of the Klein‐Gordon and Dirac equations with the combined electromagnetic field.
Massive supersymmetric quantum gauge theory
Authors: Grigore D.R. , Gut M. , Scharf G. 
Published: June 2022

AbstractWe continue the study of the supersymmetric vector multiplet in a purely quantum framework. We obtain some new results which make the connection with the standard literature. First we construct the one‐particle physical Hilbert space taking into account the (quantum) gauge structure of the model. Then we impose the condition of positivity for the scalar product only on the physical Hilbert space. Finally we obtain a full supersymmetric coupling which is gauge invariant in the supersymmetric sense in the first order of perturbation theory. By integrating out the Grassmann variables we get an interacting Lagrangian for a massive Yang‐Mills theory related to ordinary gauge theory; however the number of ghost fields is doubled so we do not obtain the same ghost couplings as in the standard model Lagrangian.
Effective descriptions of complex quantum systems: path integrals and operator ordering problems
Authors: Eckern U. , Gruber M.J. , Schwab P. 
Published: June 2022

AbstractDedicated to Bernhard Mühlschlegel on the occasion of his 80th birthdayWe study certain aspects of the effective, occasionally called collective, description of complex quantum systems within the framework of the path integral formalism, in which the environment is integrated out. Generalising the standard Feynman‐Vernon Caldeira‐Leggett model to include a non‐linear coupling between “particle” and environment, and considering a particular spectral density of the coupling, a coordinate‐dependent mass (or velocity‐dependent potential) is obtained. The related effective quantum theory, which depends on the proper discretisation of the path integral, is derived and discussed. As a result, we find that in general a simple effective low‐energy Hamiltonian, in which only the coordinate‐dependent mass enters, cannot be formulated. The quantum theory of weakly coupled superconductors and the quantum dynamics of vortices in Josephson junction arrays are physical examples where these considerations, in principle, are of relevance.
Proximity effect between superconductors and ferromagnets: from thin films to nanostructures
Authors: v. Löhneysen H. , Beckmann D. , Pérez‐Willard F. , Schöck M. , Strunk C. , Sürgers C. 
Published: June 2022

AbstractDedicated to Bernhard Mühlschlegel on the occasion of his 80th birthdayExperimental investigations of superconductor/ferromagnet (S/F) interfaces which probe the penetration of the superconducting pairing amplitude into the ferromagnet are reviewed. The microscopic basis for this proximity effect is the process of Andreev reflection which can be used to extract the current spin‐polarization in F from current‐voltage characteristics. Initial studies focused on S/F layers and multilayers, while more recent experiments investigated nanostructured point contacts in local and nonlocal configurations.
Green functions for nearest‐ and next‐nearest‐neighbor hopping on the Bethe lattice
Authors: Kollar M. , Eckstein M. , Byczuk K. , Blümer N. , van Dongen P. , Radke de Cuba M.H. , Metzner W. , Tanasković D. , Dobrosavljević V. , Kotliar G. , Vollhardt D. 
Published: June 2022

AbstractDedicated to Bernhard Mühlschlegel on the occasion of his 80th birthdayWe calculate the local Green function for a quantum‐mechanical particle with hopping between nearest and next‐nearest neighbors on the Bethe lattice, where the on‐site energies may alternate on sublattices. For infinite connectivity the renormalized perturbation expansion is carried out by counting all non‐self‐intersecting paths, leading to an implicit equation for the local Green function. By integrating out branches of the Bethe lattice the same equation is obtained from a path integral approach for the partition function. This also provides the local Green function for finite connectivity. Finally, a recently developed topological approach is extended to derive an operator identity which maps the problem onto the case of only nearest‐neighbor hopping. We find in particular that hopping between next‐nearest neighbors leads to an asymmetric spectrum with additional van‐Hove singularities.
Symmetries and pre‐metric electromagnetism
Authors: Delphenich D.H. 
Published: June 2022

AbstractThe equations of pre‐metric electromagnetism are formulated as an exterior differential system on the bundle of exterior differential 2‐forms over the spacetime manifold. The general form for the symmetry equations of the system is computed and then specialized to various possible forms for an electromagnetic constitutive law, namely, uniform linear, non‐uniform linear, and uniform nonlinear. It is shown that in the uniform linear case, one has four possible ways of prolonging the symmetry Lie algebra, including prolongation to a Lie algebra of infinitesimal projective transformations of a real four‐dimensional projective space. In the most general non‐uniform linear case, the effect of non‐uniformity on symmetry seems inconclusive in the absence of further specifics, and in the uniform nonlinear case, the overall difference from the uniform linear case amounts to a deformation of the electromagnetic constitutive tensor by the electromagnetic field strengths, which induces a corresponding deformation of the symmetry Lie algebra that was obtained in the linear uniform case.
The gravitational energy‐momentum tensor and the gravitational pressure
Authors: Maluf J.W. 
Published: June 2022

AbstractIn the framework of the teleparallel equivalent of general relativity it is possible to establish the energy‐momentum tensor of the gravitational field. This tensor has the following essential properties: (1) it is identified directly in Einstein's field equations; (2) it is conserved and traceless; (3) it yields expressions for the energy and momentum of the gravitational field; (4) is is free of second (and highest) derivatives of the field variables; (5) the gravitational and matter energy‐momentum tensors take place in the field equations on the same footing; (6) it is unique. However it is not symmetric. We show that the spatial components of this tensor yield a consistent definition of the gravitational pressure.
A gravitational mechanism for the acceleration of ultrarelativistic particles
Authors: Chicone C. , Mashhoon B. 
Published: June 2022

AbstractImagine a swarm of free particles near a point P outside a gravitating mass M and a free reference particle at P that is on a radial escape trajectory away from M. Relative to this reference particle and in a Fermi normal coordinate system constructed along its worldline, the particles in the swarm that move along the radial direction and are ultrarelativistic (that is, they have speeds above c/√2) decelerate toward this terminal speed. On the other hand, the swarm particles that are ultrarelativistic and move in directions normal to the radial (jet) directions accelerate to almost the speed of light by the gravitational tidal force of the mass M. The implications of these effects as well as the influence of the higher‐order terms on the tidal acceleration mechanism are investigated. The observational evidence in support of these general relativistic effects is briefly discussed.
Gravitational lensing as a powerful astrophysical tool: Multiple quasars, giant arcs and extrasolar planets
Authors: Wambsganss J. 
Published: June 2022

AbstractIn the 25 years since the discovery of the first double quasar Q0957+561, gravitational lensing has established itself as a valuable tool in many branches of astronomy. Fields as different as galactic structure, cosmology, or extrasolar planets benefit from the gravitational lensing effect. This article starts with a brief historic reflection, then the basics of light deflection are reviewed. Observable lensing effects and a few examples of strong lensing phenomena are shown. In the main part four applications of ''strong'' lensing will be presented and discussed:
The determination of the Hubble constant from time delay measurements in multiple quasars; it is argued that this method of determining H0 is competitive with other methods by now. The lensing‐derived values of H0 are on the low side.
Microlensing of quasars– the effects of compact stellar‐mass objects on the apparent brightness – allows us to constrain the quasar size and the occurrence of dark matter objects.The frequency of giant luminous arcs strongly depends on the high mass end of the galaxy cluster distribution. Recent investigations show that arc statistics is in agreement with the concordance cosmological model.
Searching for extrasolar planets is one of the most recent applications of gravitational lensing. The first detection shows that the method works well. This planet‐search method is complementary to other programs and has the potential to detect exo‐planets with lower masses than other ground‐based techniques.An outlook is provided on the prospects of gravitational lensing in the next few years. In particular the magnification effect on faint high‐redshift sources will be used for the investigation of the early universe, and the detection of low‐mass extrasolar planets will provide a valuable sample for statistical evaluations of the frequency of exoplanets.
Topological censorship and chronology protection
Authors: Friedman J. , Higuchi A. 
Published: June 2022

AbstractOver the past two decades, substantial efforts have been made to understand the way in which physics enforces the ordinary topology and causal structure that we observe on observed scales – from subnuclear to cosmological. We review the status of topological censorship and the topology of event horizons; chronology protection in classical and semiclassical gravity; and related progress in establishing quantum energy inequalities.
Gauge fixing procedure in the extended BRST theory. The example of the abelian 2‐forms
Authors: Constantinescu R. , Ionescu C. 
Published: June 2022

AbstractThe paper proposes a general procedure to find the form of the gauge fixing term in the extended BRST quantization of the gauge theories, a difficult problem in the standard approach. Our proposal is based on the many level structure of the extended spaces and leads to a simple form of the gauge fixing term. The abelian 2‐form model is completely analyzed as an example.