bluuebunny/crossref_metadata_2025 huggingface dataset:
Option pricing theory for financial assets with memory*
Authors: Schulz M.
Published: June 2022

Diffusion processes play an important role in physics as well as in financial sciences. The usual description by stochstic differential equations considers the Wiener process as external stochastic term, while the deterministic drift term is local in time. However, the complexity of the interaction between the observed diffusive degree of freedom and the hidden dynamics of the whole system, e.g., the coupling between a certain particle and the surrounding liquid or the relations between the price of a financial asset and the global market, requires the consideration of possible memory effects.

In the present paper we analyze the effects of a non‐Markovian asset price model on the corresponding European option prices. This model considers drift terms which are non‐local in time, so that memory effects appear. As the main result we present a generalized Black‐Scholes equation considering the whole history of the asset price evolution.
Recent developments in quantum key distribution: Theory and practice*
Authors: Mauerer W. , Helwig W. , Silberhorn Ch.
Published: June 2022

Quantum key distribution is among the foremost applications of quantum mechanics, both in terms of fundamental physics and as a technology on the brink of commercial deployment. Starting from principal schemes and initial proofs of unconditional security for perfect systems, much effort has gone into providing secure schemes which can cope with numerous experimental imperfections unavoidable in real world implementations. In this paper, we provide a comparison of various schemes and protocols. We analyse their efficiency and performance when implemented with imperfect physical components. We consider how experimental faults are accounted for using effective parameters. We compare various recent protocols and provide guidelines as to which components propose best advances when being improved.
Electrodynamics of spin currents in superconductors
Authors: Hirsch J.E.
Published: June 2022

In recent work we formulated a new set of electrodynamic equations for superconductors as an alternative to the conventional London equations, compatible with the prediction of the theory of hole superconductivity that superconductors expel negative charge from the interior towards the surface. Charge expulsion results in a macroscopically inhomogeneous charge distribution and an electric field in the interior, and because of this a spin current is expected to exist. Furthermore, we have recently shown that a dynamical explanation of the Meissner effect in superconductors leads to the prediction that a spontaneous spin current exists near the surface of superconductors (spin Meissner effect). In this paper we extend the electrodynamic equations proposed earlier for the charge density and charge current to describe also the space and time dependence of the spin density and spin current. This allows us to determine the magnitude of the expelled negative charge and interior electric field as well as of the spin current in terms of other measurable properties of superconductors. We also provide a `geometric' interpretation of the difference between type I and type II superconductors, discuss how superconductors manage to conserve angular momentum, discuss the relationship between our model and Slater's seminal work on superconductivity, and discuss the magnitude of the expected novel effects for elemental and other superconductors.
Waiting times and noise in single particle transport
Authors: Brandes T.
Published: June 2022

The waiting time distribution w(τ), i.e. the probability for a delay τ between two subsequent transition (‘jumps’) of particles, is a statistical tool in (quantum) transport. Using generalized Master equations for systems coupled to external particle reservoirs, one can establish relations between w(τ) and other statistical transport quantities such as the noise spectrum and the Full Counting Statistics. It turns out that w(τ) usually contains additional information on system parameters and properties such as quantum coherence, the number of internal states, or the entropy of the current channels that participate in transport.
On the advancements of conformal transformations and their associated symmetries in geometry and theoretical physics*
Authors: Kastrup H.A.
Published: June 2022

The historical developments of conformal transformations and symmetries are sketched: Their origin from stereographic projections of the globe, their blossoming in two dimensions within the field of analytic complex functions, the generic role of transformations by reciprocal radii in dimensions higher than two and their linearization in terms of polyspherical coordinates by Darboux, Weyl's attempt to extend General Relativity, the slow rise of finite dimensional conformal transformations in classical field theories and the problem of their interpretation, then since about 1970 the rapid spread of their acceptance for asymptotic and structural problems in quantum field theories and beyond, up to the current AdS/CFT conjecture. The occasion for the present article: hundred years ago Bateman and Cunningham discovered the form invariance of Maxwell's equations for electromagnetism with respect to conformal space‐time transformations.
Maxwell's equations in Minkowski's world: their premetric generalization and the electromagnetic energy‐momentum tensor
Authors: Hehl F.W.
Published: June 2022

In December 1907, Minkowski expressed the Maxwell equations in the very beautiful and compact 4‐dimensional form: lor f = ‐s, lor F*= 0. Here ‘lor’, an abbreviation of Lorentz, represents the 4‐dimensional differential operator. We study Minkowski's derivation and show how these equations generalize to their modern premetric form in the framework of tensor and exterior calculus (valid also in general relativity). After mentioning some applications of premetric electrodynamics, we turn to Minkowski's discovery of the energy‐momentum tensor of the electromagnetic field. We discuss how he arrived at it and how its premetric formulation looks like.
Backwards on Minkowski's road. From 4D to 3D Maxwellian electromagnetism
Authors: Itin Y. , Friedman Y.
Published: June 2022

Minkowski's concept of a four‐dimensional physical space is a central paradigm of modern physics. The three‐dimensional Maxwellian electrodynamics is uniquely generalized to the covariant four‐dimensional form. Is the (1+3) decomposition of the covariant four‐dimensional form unique? How do the different sign assumptions of electrodynamics emerge from this decomposition? Which of these assumptions are fundamental and which of them may be modified? How does the Minkowski space‐time metric emerge from this preliminary metric‐free construction? In this paper we are looking for answers to the problems mentioned. Our main result is the derivation of four different possible sets of electrodynamic equations which may occur in different types of isotropic electromagnetic media. The wave propagation in each of these media is described by the Minkowskian optical metrics. Moreover, the electric and magnetic energies are nonnegative in all cases. We also show that the correct directions of the Lorentz force (as a consequence of the Dufay and the Lenz rules) hold true for all these cases. However, the differences between these four types of media must have a physical meaning. In particular, the signs of the three electromagnetic invariants are different.
No‐go result for supersymmetric gauge theories in the causal approach
Authors: Grigore D.R. , Scharf G.
Published: June 2022

We consider the massless supersymmetric vector multiplet in a purely quantum framework and propose a power counting formula. Then we prove that the interaction Lagrangian for a massless supersymmetric non‐Abelian gauge theory (SUSY‐QCD) is uniquely determined by some natural assumptions, as in the case of Yang‐Mills models. The result can be easily generalized to the case when massive multiplets are present, but one finds out that the massive and the massless Bosons must be decoupled, in contradiction with the standard model. Going to the second order of perturbation theory produces an anomaly which cannot be eliminated. We make a thorough analysis of the model working only with the component fields.
Approximate l‐state solutions of the D‐dimensional Schrödinger equation for Manning‐Rosen potential
Authors: Ikhdair S.M. , Sever R.
Published: June 2022

The Schrödinger equation in D‐dimensions for the Manning‐Rosen potential with the centrifugal term is solved approximately to obtain bound states eigensolutions (eigenvalues and eigenfunctions). The Nikiforov‐Uvarov (NU) method is used in the calculations. We present numerical calculations of energy eigenvalues to two‐ and four‐dimensional systems for arbitrary quantum numbers n and l with three different values of the potential parameter α. It is shown that because of the interdimensional degeneracy of eigenvalues, we can also reproduce eigenvalues of a upper/lower dimensional system from the well‐known eigenvalues of a lower/upper dimensional system by means of the transformation (n,l,D) → (n,l ± 1,D ∓ 2). This solution reduces to the Hulthén potential case.
DMRG studies of critical SU(N) spin chains
Authors: Führinger M. , Rachel S. , Thomale R. , Greiter M. , Schmitteckert P.
Published: June 2022

The DMRG method is applied to integrable models of antiferromagnetic spin chains for fundamental and higher representations of SU(2), SU(3), and SU(4). From the low energy spectrum and the entanglement entropy, we compute the central charge and the primary field scaling dimensions. These parameters allow us to identify uniquely the Wess–Zumino–Witten models capturing the low energy sectors of the models we consider.
Superfluid to Mott‐insulator transition in an anisotropic two‐dimensional optical lattice
Authors: Polak T.P. , Kopeć T.K.
Published: June 2022

We study the superfluid to Mott‐insulator transition of bosons in an optical anisotropic lattice by employing the Bose‐Hubbard model living on a two‐dimensional lattice with anisotropy parameter κ. The compressible superfluid state and incompressible Mott‐insulator (MI) lobes are efficiently described analytically, using the quantum U(1) rotor approach. The ground state phase diagram showing the evolution of the MI lobes is quantified for arbitrary values of κ, corresponding to various kind of lattices: from square, through rectangular to almost one‐dimensional.
A look at the abandoned contributions to cosmology of Dirac, Sciama, and Dicke
Authors: Unzicker A.
Published: June 2022

The separate contributions to cosmology of the above researchers are revisited and a cosmology encompassing their basic ideas is proposed. We study Dirac's article (1938) on the large number hypothesis, Sciama's proposal (1953) of realizing Mach's principle, and Dicke's considerations (1957) on a flat‐space representation of general relativity with a variable speed of light (VSL). Dicke's tentative theory can be formulated in a way which is compatible with Sciama's hypothesis on the gravitational constant G. Additionally, such a cosmological model is shown to satisfy Dirac's second ‘large number’ hypothesis on the total number of particles in the universe being proportional to the square of the epoch. In the same context, Dirac's first hypothesis on an epoch‐dependent G – contrary to his prediction – does not necessarily produce a visible time dependence of G. While Dicke's proposal reproduces the classical tests of GR in first approximation, the cosmological redshift is described by a shortening of measuring rods rather than an expansion of space. Since the temporal evolution of the horizon R is governed by , the flatness and horizon problems do not arise in the common form.
The momentum of electromagnetic waves in dielectric materials*
Authors: Dick R.
Published: June 2022

Variation of the generally covariant version of Minkowski's Lagrangian of macroscopic Maxwell theory with respect to the metric yields a symmetric tensor Tμν which reproduces the Poynting vector 𝒮i = cT0i, and therefore would seem to favor Abraham's proposal 𝒫Ai = 𝒮i/c2 for the momentum density in a macroscopic electromagnetic wave. However, the T00 component does not reproduce the standard energy density in the rest frame in the flat limit. The difference between the energy density and T00 has the same structure as the difference between the Minkowski momentum density 𝒫Mi = n2𝒮i/c2 and the Abraham momentum density. The result therefore adds further credibility to Minkowski's original energy‐momentum tensor and his proposal for the total momentum density of electromagnetic waves in dielectric materials. We draw attention to the facts that the covariant formulation of macroscopic Maxwell theory of dielectric materials requires a field strength‐velocity coupling term which could only be inferred in a long wavelength limit from quantum electrodynamics, and that the theory is clearly limited to interactions of sub‐UV photons with matter. Therefore, in spite of the fact that macroscopic Maxwell theory can formally be written in generally covariant terms, the theory for n ≠ 1 should be considered as inherently non‐relativistic, with non‐relativistic corrections of order n ‐ 1. The difference 𝒫M ‐ c‐2 𝒮 between Minkowski's momentum density and the rescaled Poynting vector is an example of an order n ‐ 1 correction.
Improved analytical approximation to arbitrary l‐state solutions of the Schrödinger equation for the hyperbolical potential
Authors: Ikhdair S.M. , Sever R.
Published: June 2022

A new approximation scheme to the centrifugal term is proposed to obtain the l ≠ 0 bound‐state solutions of the Schrödinger equation for an exponential‐type potential in the framework of the hypergeometric method. The corresponding normalized wave functions are also found in terms of the Jacobi polynomials. To show the accuracy of the new proposed approximation scheme, we calculate the energy eigenvalues numerically for arbitrary quantum numbers n and l with two different values of the potential parameter σ0. Our numerical results are of high accuracy like the other numerical results obtained by using program based on a numerical integration procedure for short‐range and long‐range potentials. The energy bound‐state solutions for the s‐wave (l = 0) and σ0 = 1 cases are given.
A new look at Bell's inequalities and Nelson's theorem
Authors: Schulz B.
Published: June 2022

In 1985, Edward Nelson, who formulated the theory of stochastic mechanics, made an interesting remark about Bell's theorem. Nelson analysed the latter in the light of classical fields that behave randomly. He found that if a stochastic hidden variable theory fulfils certain conditions, the inequality of Bell can be violated. Moreover, Nelson was able to prove that this may happen without any instantaneous communication between the two spatially separated measurement stations. Since Nelson's article got almost overlooked by physicists, we try to review his comments on the theorem. We argue that a modification of stochastic mechanics published recently by Fritsche and Haugk can be extended to a theory which fulfils the requirements of Nelson's analysis. The article proceeds to derive the quantum mechanical formalism of spinning particles and the Pauli equation from this version of stochastic mechanics. Then, we investigate Bohm's version of the EPR experiment. Additionally, other setups, like entanglement swapping or time and position correlations, are shortly explained from the viewpoint of our local hidden‐variable model. Finally, we mention that this theory could perhaps be relativistically extended and useful for the formulation of quantum mechanics in curved space‐times.
Rigorous solution of a Hubbard model extended by nearest‐neighbour Coulomb and isotropic exchange interaction on a triangle and tetrahedron
Authors: Schumann R.
Published: June 2022

In connection with the study of the extended Hubbard model on an isosceles triangular cluster, we discovered a factor two error in the coding of the Ising part of the Heisenberg term in the Hamiltonian. In consequence the rigorous results remain valid, but not for the isotropic Heisenberg model, but for an anisotropic Heisenberg model.
Quantum field theory and composite fermions in the fractional quantum Hall effect
Authors: Kossow M.
Published: June 2022

We derive a composite fermion model for the fractional quantum Hall effect from relativistic quantum electrodynamics. With simple arguments it is shown that a special Chern Simons transformation of the Dirac electrons in four spacetime dimensions leads in the low energy limit to a single particle Hamiltonian for composite fermions in three dimensions with correction terms such as Rashba‐ or Dresselhaus‐spin‐orbit coupling and zitterbewegung. Furthermore we provide a mechanism to quantum‐mechanically project the quantum fields defined in the four dimensional Minkowski space to three dimensions. This leads to a relativistic field theory and especially a composite fermion field theory in three dimension. This projection map can be combined with the projection onto a Landau level or composite fermion Landau level respectively. This results in a quasi relativistic quantum field theory on a noncommutative plane. The phenomenological models resulting from this approach are discussed and allow a systematical exploration of the effects of the spin and the condensation in a Landau level. We expect from the relativistic approach corrections in terms of spin‐orbit coupling effects. From the projection onto Landau levels we expect a modification of the dispersion relation and a modified composite fermion mass. Furthermore, the BRST quantization for Chern Simons theories with compact gauge group is reviewed and the phenomenological consequences within a composite fermion model with spin are discussed. The connection to Wess Zumino Witten theories is recalled and a possible link between the corresponding central charge of the related affine Lie algebra and the composite fermion filling factor is pointed out.
The mathematical pendulum from Gauß via Jacobi to Riemann
Authors: Dittrich W.
Published: June 2022

The goal of this article is to introduce double‐periodic elliptic functions on the basis of a “simple” mechanical system, that of the mathematical pendulum. Thereby it is not geometry that is in the foreground, as in Gauß's analysis of the lemniscatian curve, but rather the calculation of the specific attributes of elliptic functions with the aid of a periodic integrable system. Not the spatial degree of freedom, but the time variable is continued into the complex plane. This will make it possible for us to not only identify the known real period of the pendulum oscillation, but also to detect a second imaginary period. Only then does the solution of the equation of motion become a Jacobi‐type elliptic function. Using the Cauchy integral theorem, which Gauß was already familiar with, as well as the simplest Riemannian surface of the function

we want to calculate the analytic and topological characteristics of the oscillatory motion of a pendulum. Our intent is to show that elliptic functions could have appeared much earlier than 1796 in the literature. Admittedly, for this the field of complex numbers was necessary, as represented in the Gaußian plane of complex numbers. However, Gauß was unwilling to publish his findings because of his “fear of the cry of the Boeotians”.
Gravitoelectromagnetic cavitons in the kinetic regime
Authors: Li X.Q. , Liu S.Q. , Tao X.Y.
Published: June 2022

We consider the interaction of gravitational fields (including “gravitoelectromagnetism”) with interstellar matter dealing with resonant wave‐particle and wave‐wave interactions on the basis of magnetic‐type Maxwell‐Vlasov equations. It is found that the behavior of the perturbed GEM fields, the perturbed density and self‐generated gravitomagnetic field with very low frequency, can be described by the nonlinear coupling Eqs. (98–100). Numerical results show that they may collapse. In other words, due to self‐focusing, a stronger GEM fields magnified up to 103 times, could be produced; they are the GEM cavitons, describing gravity shielding and filament effects. And the self‐generated gravitomagnetic field is concurrently focused by the background material to a small space where it may be detected.
Intrinsic decoherence in the interaction of two fields with a two‐level atom
Authors: Juárez‐Amaro R. , Escudero‐Jiménez J.L. , Moya‐Cessa H.
Published: June 2022

We study the interaction of a two‐level atom and two fields, one of them classical. We obtain an effective Hamiltonian for this system by using a method recently introduced that produces a small rotation to the Hamiltonian that allows to neglect some terms in the rotated Hamiltonian. Then we solve a variation of the Schrödinger equation that models decoherence as the system evolves through intrinsic mechanisms beyond conventional quantum mechanics rather than dissipative interaction with an environment.
Ultra‐fast dynamics in solids: non‐equilibrium behaviour of magnetism and atomic structure
Authors: Bennemann K.H.
Published: June 2022

Non‐equilibrium physics is of fundamental interest, for example, for extensions of statistical mechanics and thermodynamics. In particular, it is important to understand how conservation laws like energy conservation and angular‐momentum conservation in magnetic solids control the time scale of the dynamics. Laser irradiation may cause intense electronic excitations and thus a strong non‐equilibrium state. Results are presented for the ultra‐fast response of magnetism in ferromagnetic transition metals like Ni, Co, Fe, and Gd and furthermore of the atomic structure in semiconductors like Si, Ge, and InSb. Non‐thermal melting is a most spectacular example of ultra‐fast bond breaking. Time‐resolved magnetooptical experiments yielding sub‐picosecond spin dynamics are discussed. The spin dynamics is accompanied by THz light emission. The structural changes in semiconductors, bond changes sp3 → s2p2, and phase transitions occur within about 100 fs. The results also shed light on electron‐transfer processes, on ionization, and on molecular dissociation dynamics, which may occur during fs and as times. We discuss the application of time‐resolved analysis to tunnelling problems and the phase diagram of high‐Tc superconductivity.
Entanglement of spin chains with general boundaries and of dissipative systems
Authors: Stauber T. , Guinea F.
Published: June 2022

We analyze the entanglement properties of spins (qubits) close to the boundary of spin chains in the vicinity of a quantum critical point and show that the concurrence at the boundary is significantly different from the one of bulk spins. We also discuss the von Neumann entropy of dissipative environments in the vicinity of a (boundary) critical point, such as two Ising‐coupled Kondo‐impurities or the dissipative two‐level system. Our results indicate that the entanglement (concurrence and/or von Neumann entropy) changes abruptly at the point where coherent quantum oscillations cease to exist. The phase transition modifies significantly less the entanglement if no symmetry breaking field is applied and we argue that this might be a general property of the entanglement of dissipative systems. We finally analyze the entanglement of an harmonic chain between the two ends as function of the system size.
Thermal dynamics at surfaces
Authors: Brune H.
Published: June 2022

The present paper describes what happens at the surface of a crystal as its temperature steadily increases from zero Kelvin close to the bulk melting temperature. We treat thermal motion, such as the diffusion of individual adatoms establishing mass transport, the formation of adatom or vacancy gases coexisting with islands or steps of the condensed phase, surface phonons and the anharmonicity of the surface potential being markedly different from the one in bulk, as well as thermally induced reconstructions, surface roughening, and finally surface melting, which usually well precedes bulk melting. The paper intends to give an overview with references to the original and review literature.
The “writing on the cosmic wall”: Is there a straightforward explanation of the cosmic microwave background?
Authors: Fahr H.J. , Zönnchen J.H.
Published: June 2022

TheCosmicMicrowaveBackground (CMB) is taken today as reflecting the thermodynamical state of the universe at these early cosmic times. Based on this assumption and standard cosmological principles meanwhile many fundamental cosmological facts have been deduced from the CMB state which, however, to some surprise reveal that the universe should be dominated by dark energy and dark matter, while for its energy content the usual baryonic matter is nearly negligible. Thus the question which we want to raise in this article is, whether this standard interpretation of the CMB phenomenon is solid and unequivocal enough to support the standard cosmological claims. We shall show, however, that in many details the standard explanation is not straightforward, but allows for important alternatives which seriously should be looked at. Especially arguments for a vanishing cosmic curvature (k = 0) are shown to be weak, and, contrary to the usual claim, the light distance to the recombination horizon is in fact strongly model‐biassed. We also show that the CMB dipole which is generally understood as a consequence of a peculiar motion by about 680 km/s with respect to rest system of the CMB can as well, and perhaps even better, be understood as indication of differerent cosmological expansion dynamics seen in an anisotropically expanding universe in different directions of the sky. We also discuss that the power amplitude (i.e. effective Planck temperature) in the dipolar CMB structure depends on wavelength even inverting the dipole maximum orientation in the Wien's branch. In addition unexpected properties of the lowest CMB multipoles could mean that we are at least partly seeing an unquantifyable foreground in the background. Only after its removal the CMB interpretation could at all then, but then on a completely new basis, become a subject of cosmological terms. At the end of this article we shall briefly discuss an alternative explanation of the CMB radiation which helps to better understand the mysterious cosmic photon‐to‐baryon ratio of about 109.
Improved analytical approximation to arbitrary l‐state solutions of the Schrödinger equation for the hyperbolical potentials
Authors: Ikhdair S.M. , Sever R.
Published: June 2022

The Schrödinger equation for the rotational‐vibrational (ro‐vibrational) motion of a diatomic molecule with empirical potential functions is solved approximately by means of the Nikiforov‐Uvarov method. The approximate energy spectra and the corresponding normalized total wavefunctions are calculated in closed form and expressed in terms of the hypergeometric functions or Jacobi polynomials Pn(μ, ν) (x), where μ >−1, ν >−1 and x in [−1, +1]. The s‐waves analytic solution is obtained. The numerical energy eigenvalues for selected H2 and Ar2 molecules are also calculated and compared with the previous models and experiments.
Reduction of quantum fluctuations by anisotropy fields in Heisenberg ferro‐ and antiferromagnets
Authors: Vogt B. , Kettemann S.
Published: June 2022

The physical properties of quantum systems, which are described by the anisotropic Heisenberg model, are influenced by thermal as well as by quantum fluctuations. Such a quantum Heisenberg system can be profoundly changed towards a classical system by tuning two parameters, namely the total spin and the anisotropy field: Large easy‐axis anisotropy fields, which drive the system towards the classical Ising model, as well as large spin quantum numbers suppress the quantum fluctuations and lead to a classical limit. We elucidate the incipience of this reduction of quantum fluctuations. In order to illustrate the resulting effects we determine the critical temperatures for ferro‐ and antiferromagnets and the ground state sublattice magnetization for antiferromagnets. The outcome depends on the dimension, the spin quantum number and the anisotropy field and is studied for a widespread range of these parameters. We compare the results obtained by: Classical Mean Field, Quantum Mean Field, Linear Spin Wave and Random Phase Approximation. Our findings are confirmed and quantitatively improved by numerical Quantum Monte Carlo simulations. The differences between the ferromagnet and antiferromagnet are investigated. We finally find a comprehensive picture of the classical trends and elucidate the suppression of quantum fluctuations in anisotropic spin systems. In particular, we find that the quantum fluctuations are extraordinarily sensitive to the presence of small anisotropy fields. This sensitivity can be quantified by introducing an “anisotropy susceptibility”.
Effect of electric field on diffusion in disordered materials
Authors: Jansson F. , Nenashev A.V. , Baranovskii S.D. , Gebhard F. , Österbacka R.
Published: June 2022

The effect of electric field on diffusion of charge carriers in disordered materials is studied by Monte Carlo computer simulations and analytical calculations. It is shown how an electric field enhances the diffusion coefficient in the hopping transport mode. The enhancement essentially depends on the temperature and on the energy scale of the disorder potential. It is shown that in one‐dimensional hopping the diffusion coefficient depends linearly on the electric field, while for hopping in three dimensions the dependence is quadratic.
Localization of excitons in weakly disordered semiconductor structures: A model study
Authors: Gögh N. , Thomas P. , Kuznetsova I. , Meier T. , Varga I.
Published: June 2022

Localization of the center‐of‐mass (com) motion of an exciton in a disordered semiconductor structure is studied theoretically by focusing on nonlinear optical spectroscopy. A one‐dimensional tight‐binding model with diagonal disorder is applied and the Coulomb interaction is treated consistently. In the ordered situation the center‐of‐mass momentum (K) selection rule leads to only the lowest transition for K = 0. The break down of the com‐K‐selection rule produces the well known asymmetric excitonic lines of disordered semiconductors. The coupling between the lowest dominant transition to this modified com‐continuum yields Fano‐like features in the nonlinear spectra.
Application of the photon's intrinsic flux to the 1s‐2p and 2p‐3d excitonic transitions in nanostructures
Authors: Saglam Z. , Saglam M.
Published: June 2022

We have applied our two recent results [depending on its helicity photon carries a quantum flux of ± Φ 0 = ± hc/e and the quantized magnetic fluxes through the electronic orbits of the Dirac hydrogen atom are given by: Φ (n,l,mj) = (n‐l‐mj)Φ0) ] to the 1s‐2p and 2p‐3d excitonic transitions in nanostructures. It is shown that the flux changes for the non‐zero matrix elements in the 1s‐2p and 2p‐3d excitonic transitions is either ± Φ0 or zero. The present result supports the previous results stated above. It is also shown that spin flip is possible in the 1s‐2p and 2p‐3d excitonic transitions.
Conductance asymmetry of a slot gate Si‐MOSFET in a strong parallel magnetic field
Authors: Shlimak I. , Golosov D.I. , Butenko A. , Friedland K.‐J. , Kravchenko S.V.
Published: June 2022

We report measurements on a Si‐MOSFET sample with a slot in the upper gate, allowing for different electron densities n1,2 across the slot. The dynamic longitudinal resistance was measured by the standard lock‐in technique, while maintaining a large DC current through the source‐drain channel. We find that the conductance of the sample in a strong parallel magnetic field is asymmetric with respect to the DC current direction. This asymmetry increases with magnetic field. The results are interpreted in terms of electron spin accumulation or depletion near the slot.
Angular and temperature‐related specific features of averaging of hole effective masses in p‐Ge at low temperatures
Authors: Tisnek T. , Veinger A. , Zabrodskii A. , Goloshchapov S.
Published: June 2022

Microwave magnetoresistance of lightly doped (nondegenerate) p‐Ge has been studied by the electron spin resonance method, which can record the derivative of the microwave absorption with respect to the magnetic field. The change in the absorption is proportional to that in the conductivity of the semiconductor in the magnetic field (magnetoresistance). It was found that the averaging time of the light and heavy holes effective masses depends on temperature and on the magnetic field direction in a sample. An analysis of the derivative made it possible to determine regions of the fastest effective mass averaging.
Lattice distortion (Peierls Transition) caused by spin interaction in the chaotic impurity system of a semiconductor
Authors: Zabrodskii A. , Veinger A. , Tisnek T. , Goloshchapov S.
Published: June 2022

The effect of an elastic spontaneous distortion of the crystal lattice of a doped semiconductor Ge:As near the insulator–metal (IM) phase transition has been discovered. The effect is manifested in the electron spin resonance (ESR) of neutral As atoms as a splitting of the single resonance absorption line. It observed at electron concentrations in the range 0.8 < n/nC < 1 at low temperatures T < 100 K (nC = 3.7 × 1017 cm‐3 is the critical electron concentration for the IM phase transition). The splitting is the strongest along each of the six [110] directions, which indicates that the local lattice distortion occurs just in these directions. As a result, a sample is possibly divided into separate domains differing in the directions of compressive or tensile deformations. A study of concentration, temperature, and angular dependences of the effect has shown that the phenomenon discovered can be understood in terms of the Peierls spin transition model.
Calculation of profile of charge carrier concentration in modulation doped structure with a wide potential well
Authors: Shchurova L.Yu.
Published: June 2022

We investigate the equilibrium state of interacting electron system with Fermi statistics in modulation doped structure with a wide quantum well. The model is formulated for the carrier system with a sufficiently high density, such that the de Broglie wavelength of electrons is smaller than the width of the quantum well. Due to a significant interaction of electrons with electric field of the doped layer, a state with strongly‐inhomogeneous density of electrons is formed. Within the hydrodynamic approach, we set up formalism for calculating the electron density across the width of the potential well. We have obtained the exact solution of the equations, which is expressed in terms of hypergeometric functions. Based on the deduced formulas, we performed numerical computations for the profile of carriers' concentrations in a potential well in the modulation doped Si/SiGe/Si structures.
Localised magneto‐optical collective excitations of impure graphene
Authors: Fischer A.M. , Dzyubenko A.B. , Römer R.A.
Published: June 2022

We study optically‐induced collective excitations of graphene in the presence of a strong perpendicular magnetic field and a single impurity. We determine the energies and absorption strengths of these excitations, which become localised on the impurity. Two different types of impurity are considered i. the long‐range Coulomb impurity, ii. a δ‐function impurity located at either an A or B graphene sublattice site. Both impurity types result in some bound states appearing both above and below the magnetoplasmon continuum, although the effect of the short‐range impurity is less pronounced. The dependence of the energies and oscillator strengths of the bound states on the filling factor is investigated.
Quadrupolar glass as a model for charge carrier transport in nonpolar organic materials
Authors: Novikov S.V.
Published: June 2022

Monte Carlo simulation of the charge carrier transport in disordered nonpolar organic materials has been carried out. As a suitable model we considered the model of quadrupolar glass. A general formula for the temperature and field dependence of the mobility was suggested. A comparison with experimental data has been carried out.
The dependence of polymer conductivity on the work function of metallic electrodes
Authors: Ionov A.N. , Dunaevskii M.S. , Nikolaeva M.N. , Rentzsch R.
Published: June 2022

It is shown that the occurrence of metallic conductivity in polymers is due to their electrification. In particular, the current density depends on the electron work function of metallic electrodes which are in contact with the polymer.
Superconductivity of polymers with charge injection doping
Authors: Ionov A.N. , Rentzsch R.
Published: June 2022

We show that conductivity measurements on sandwiches of a polymer between normal‐metal and superconducting‐metal electrodes can be interpreted in terms of intrinsic superconductivity due to injection of charge into the polymer.
Pair and impair, even and odd form fields, and electromagnetism
Authors: da Rocha R. , Rodrigues W.A.
Published: June 2022

In this paper after reviewing the Schouten and de Rham definition ofimpairandpairdifferential form fields (not to be confused with differential form fields of even and odd grades) we prove that in arelativistic spacetimeit is possible (despite claims in contrary) to coherently formulate electromagnetism (and we believe any other physical theory) using only pair form fields or, if one wishes, using pair and impair form fields together, in an appropriate way. Those two distinct descriptions involve only a mathematical choice and do not seem to lead to any observable physical consequence if due care is taken. Moreover, we show in details that a formulation of electromagnetic theory in the Clifford bundle formalism of differential forms where the two Maxwell equations of the so called metric‐free approach becomes a single equation is compatible with both formulations of electromagnetism just mentioned above. In addition we derive directly from Maxwell equation the density of force (coupling of the electromagnetic field with the charge current) that is a postulate in the free metric approach to electromagnetism. We recall also a formulation of the engineering version of Maxwell equations using electric and magnetic fields as objects of the same nature, i.e., without using polar and axial vectors.
An electric charge has no screw sense – a comment on the twistfree formulation of electrodynamics by da Rocha and Rodrigues
Authors: Itin Y. , Obukhov Yu.N. , Hehl F.W.
Published: June 2022

Da Rocha and Rodigues (RR) claim (i) that in classical electrodynamics in vector calculus the distinction between polar and axial vectors and in exterior calculus between twisted and untwisted forms is inappropriate and superfluous, and (ii) that they can derive the Lorentz force equation from Maxwell's equations. As to (i), we point out that the distinction of polar/axial and twisted/untwisted derives from the property of the electric charge of being a pure scalar, that is, not carrying any screw sense. Therefore, the mentioned distinctions are necessary ingredients in any fundamental theory of electrodynamics. If one restricted the allowed coordinate transformations to those with positive Jacobian determinants (or prescribed an equivalent constraint), then the RR scheme could be accommodated; however, such a restriction is illegal since electrodynamics is, in fact, also covariant under transformations with negative Jacobians. As to (ii), the “derivation” of the Lorentz force from Maxwell's equations, we point out that RR forgot to give the symbol F (the field strength) in Maxwell's equations an operational meaning in the first place. Thus, their proof is empty. Summing up: the approach of RR does not bring in any new insight into the structure of electrodynamics.
Broad band electromagnetic wave absorbers designed with nano‐metal films
Authors: Nimtz G. , Panten U.
Published: June 2022

In the thirties of the last century it was shown that nano‐metal films have a frequency independent absorption in the far infrared regime and below. Moreover, the absorption A of these films is 0.5 and at the same time both reflection R and transmission T are 0.25, complying with the relation A + R + T = 1 at a sheet resistance Z□of 60 πΩ. The latter property of nano‐metal films was shown by Woltersdorff in 1934. Multiple reflections between such films allow the design of low reflecting large scale absorbers for the wave length range from far infrared to low frequency radio waves. Experimental data of the novel absorber device measured in the GHz frequency range are presented. The electrical nano‐metal film properties are also useful for applications in IR‐photonics and IR‐communication systems. The article presents a brief review of the historical studies on free carrier electromagnetic wave absorption and on novel applications.
Transport through a Kondo quantum dot: Functional RG approach
Authors: Schmidt H. , Wölfle P.
Published: June 2022

We apply the functional renormalization group (FRG) method to calculate the conductance of a quantum dot in the Kondo regime. Starting from the exact FRG equations in Keldysh formulation for the Kondo exchange Hamiltonian in pseudo‐fermion (pf) representation, we solve the coupled equations for the pf self energy and the coupling function, neglecting three‐particle and higher correlation functions. The conductance G as a function of temperature T and bias voltage V is calculated using a renormalized Golden Rule expression. The limiting behavior at T and/or V >> TK (TK: Kondo temperature) agrees with known results. The difficulties when approaching strong coupling are analyzed and improvements are suggested.
Manifestly covariant classical correlation dynamics II. Transport equations and Hakim equilibrium conjecture
Authors: Tian C.
Published: June 2022

This is the second of a series of papers on special relativistic classical statistical mechanics. Employing the general theory developed in the first paper, we derive rigorously the relativistic Vlasov, Landau, and Boltzmann equations, respectively. The latter two equations advocate the Jüttner distribution as the equilibrium distribution. We thus, at the fully microscopic level, provide support for the recent numerical findings of Cubero and co‐workers of the special relativistic generalization of the Maxwell‐Boltzmann distribution. Furthermore, the present theory allows us to calculate rigorously various correlation functions at the relativistic many‐body equilibrium. Therefore, we demonstrate that the relativistic many‐body equilibrium conjecture of Hakim is justified.
Spatial Wilson loop in continuum, deconfining SU(2) Yang‐Mills thermodynamics
Authors: Ludescher J. , Keller J. , Giacosa F. , Hofmann R.
Published: June 2022

The uniquess of the effective actions describing 4D SU(2) and SU(3) continuum, infinite‐volume Yang‐Mills thermodynamics in their deconfining and preconfining phases is made explicit. Subsequently, the spatial string tension is computed in the approach proposed by Korthals‐Altes. This SU(2) calculation is based on a particular, effective two‐loop correction to the pressure needed for the extraction of the hypothetic number density of isolated and screened magnetic monopoles or antimonopoles in the deconfining phase. By exponentiating the exchange of the tree‐level massless but one‐loop dressed mode within a quadratic spatial contour of side‐length L in the effective theory we demonstrate that for L → ∞ the Wilson loop exhibits perimeter law. This is in contrast to a rigorous lattice result subject to the Wilson action and for this action valid at sufficiently high temperature. In the framework of the effective theory there is, however, a regime for small (spatially unresolved) L were the exponent of the spatial Wilson loop possesses curvature as a function of L.
The quasiorder‐disorder phase transition and peak effect in MgB2 type‐II superconducting materials and thin films
Authors: Chou M.J. , Horng H.E.
Published: June 2022

The peak effect and the quasiorder‐disorder first‐order phase transition for Magnesium diboride, MgB2, superconducting bulk materials have been studied. The peak values of the critical current density Jc, and the exact peak positions together with its corresponding half‐widths for a constant temperature as well as for a constant applied magnetic field have been calculated by considering the quantum, thermal as well as random fluctuations of the vortex lattice. The results for MgB2 bulk materials are in agreement with the experiment. The peak effect for MgB2 superconducting thin films is also predicted theoretically. The expected peak effect may be observed provided that doping or other experimental techniques are applied to improve the flux pinning of the MgB2 superconducting thin films.
Dmitrij Volkov, super‐Poincaré group and Grassmann variables
Authors: Zheltukhin A.A.
Published: June 2022

A fundamental role of the Hermann Grassmann anticommuting variables both in physics and mathematics is discussed on the example of supersymmetry. The talk describes how the D. Volkov question about possibility of the existence of Nambu‐Goldstone fermions, realized by the Grassmannian variables, resulted in the discovery of the super‐Poincaré group, its spontaneous breaking and gauging.
3+1+1 dimensional covariant gravitational dynamics on an asymmetrically embedded brane: The average equations
Authors: Keresztes Z. , Gergely L.Á.
Published: June 2022

We give the evolution and constraint equations arising from averaging the higher dimensional dynamics over the two sides of an asymmetrically embedded brane.
Algebraic geometry approach in gravity theory and new relations between the parameters in type I low‐energy string theory action in theories with extra dimensions
Authors: Dimitrov B.G.
Published: June 2022

On the base of the distinction between covariant and contravariant metric tensor components, a new (multivariable) cubic algebraic equation for reparametrization invariance of the gravitational Lagrangian has been derived and parametrized with complicated non‐elliptic functions, depending on the (elliptic) Weierstrass function and its derivative. This is different from standard algebraic geometry, where only two‐dimensional cubic equations are parametrized with elliptic functions and not multivariable ones. Physical applications of the approach have been considered in reference to theories with extra dimensions. The s.c. “length function” l(x) has been introduced and found as a solution of quasilinear differential equations in partial derivatives for two different cases of “compactification + rescaling” and “rescaling + compactification”. New physically important relations (inequalities) between the parameters in the action are established, which cannot be derived in the case l = 1 of the standard gravitational theory, but should be fulfilled also for that case.
Flavour mixing in an expanding universe
Authors: Tarantino F.
Published: June 2022

Motivated by a microscopic model of string‐inspired foam, in which foamy structures are provided by brany point‐like defects (D‐particles) in space‐time, we discuss flavour mixing in curved space‐time for spin‐0 and spin‐1/2 particles. This can be view as the low energy limit of flavour non‐preserving interactions of stringy matter excitations with the defects, and non‐trivial space‐time background induced by quantum fluctuations of the D‐particles. We show, at late epochs of the Universe, that both the fermionic and the bosonic vacuum condensate behaves as a fluid with negative pressure and positive energy; however the equation of state has wfermion > ‐1/3 and therefore the contribution of fermion‐fluid flavour vacuum alone could not yield accelerating Universes. On the other hand, for the boson fluid the equation of state is, for late eras, close to wboson → ‐1, and hence overall the D‐foam universe appears accelerating at late eras.
Stable periodic regime in a scalar field cosmology
Authors: Toporensky A.
Published: June 2022

We describe three different regimes in the cosmological dynamics of a Universe filled with a scalar field. In particular, we claim the existence of a stable periodic solution, which has been found numerically for the case of a shallow scalar field potential.