Showing papers in "Annalen der Physik in 2007"
TL;DR: In this paper, the authors showed that the coupling of an artificial Josephson atom coupled to a transmission line resonator can reach values greater than 1, where α is the fine structure constant.
Abstract: After reviewing the limitation by the fine structure constant α of the dimensionless coupling constant of an hydrogenic atom with a mode of the electromagnetic field in a cavity, we show that the situation presents itself differently for an artificial Josephson atom coupled to a transmission line resonator. Whereas the coupling constant for the case where such an atom is placed inside the dielectric of the resonator is proportional to α1/2, the coupling of the Josephson atom when it is placed in series with the conducting elements of the resonator is proportional to α-1/2 and can reach values greater than 1.
255 citations
TL;DR: In this paper, a constitutive relation for linear viscoelasticity of composite materials is formulated using the novel concept of Variable Order (VO) differintegrals, where the order of the derivative is allowed to be a function of the independent variable (time), rather than a constant of arbitrary order.
Abstract: A constitutive relation for linear viscoelasticity of composite materials is formulated using the novel concept of Variable Order (VO) differintegrals. In the model proposed in this work, the order of the derivative is allowed to be a function of the independent variable (time), rather than a constant of arbitrary order. We generalize previous works that used fractional derivatives for the stress and strain relationship by allowing a continuous spectrum of non-integer dynamics to describe the physical problem. Starting with the assumption that the order of the derivative is a measure of the rate of change of disorder within the material, we develop a statistical mechanical model that is in agreement with experimental results for strain rates varying more than eight orders of magnitude in value. We use experimental data for an epoxy resin and a carbon/epoxy composite undergoing constant compression rates in order to derive a VO constitutive equation that accurately models the linear viscoelastic deformation in time. The resulting dimensionless constitutive equation agrees well with all the normalized data while using a much smaller number of empirical coefficients when compared to available models in the literature.
134 citations
TL;DR: In this paper, the authors analyzed the Einstein-Cartan theory of gravitation with Elko spinors as sources of curvature and torsion and derived the spin angular momentum tensor.
Abstract: The present paper analyses the Einstein-Cartan theory of gravitation with Elko spinors as sources of curvature and torsion. After minimally coupling the Elko spinors to torsion, the spin angular momentum tensor is derived and its structure is discussed. It shows a much richer structure than the Dirac analogue and hence it is demonstrated that spin one half particles do not necessarily yield only an axial vector torsion component. Moreover, it is argued that the presence of Elko spinors partially solves the problem of minimally coupling Maxwell fields to Einstein-Cartan theory.
116 citations
TL;DR: In this article, a cosmological Elko spin one half-matter field with mass dimension one was discovered and the spacetime was assumed to be homogeneous and isotropic in order to simplify the resulting field equations.
Abstract: Recently, a spin one half matter field with mass dimension one was discovered, called Elko spinors. The present work shows how to introduce these fields into a curved spacetime by the standard covariantisation scheme. After formulating the coupled Einstein-Elko field equations, the spacetime is assumed to be homogeneous and isotropic in order to simplify the resulting field equations. Analytical ghost Elko solutions are constructed which have vanishing energy-momentum tensor without and with cosmological constant. The cosmological Elko theory is finally related to the standard scalar field theory with self interaction that gives rise to inflation and it is pointed out that the Elko spinors are not only prime dark matter candidates but also prime candidates for inflation.
104 citations
92 citations
TL;DR: In this article, the authors investigated pitfalls in the evaluation and the influence of self-citations in the Hirsch index and investigated quantitatively some pitfalls in their evaluation and showed that self citations can influence the accuracy of the evaluation.
Abstract: The h index was introduced by Hirsch to quantify an individual's scientific research output. It has been widely used in different fields to show the relevance of the research work of prominent scientists. I have worked out 26 practical cases of physicists which are not so prominent. Therefore this case study should be more relevant to discuss various features of the Hirsch index which are interesting or disturbing or both for the more average situation. In particular, I investigate quantitatively some pitfalls in the evaluation and the influence of self-citations.
77 citations
TL;DR: In this paper, the NikiforovUvarov (NU) method is used to obtain exact energy eigenvalues and corresponding eigenfunctions for PT -symmetric generalized Woods-Saxon (WS) potential.
Abstract: The one-dimensional Klein-Gordon (KG) equation has been solved for the PT -symmetric generalized Woods-Saxon (WS) potential. The NikiforovUvarov (NU) method which is based on solving the second-order linear differential equations by reduction to a generalized equation of hypergeometric type is used to obtain exact energy eigenvalues and corresponding eigenfunctions. We have also investigated the positive and negative exact bound states of the s-states for different types of complex generalized WS potentials.
73 citations
TL;DR: In this paper, the emergence in the deforming material of local strain patterns (self excited waves), which are ordered in space and evolve with time, was investigated for a wide range of metals and alloys.
Abstract: The emergence in the deforming material of local strain patterns (self excited waves), which are ordered in space and evolve with time, has been investigated for a wide range of metals and alloys. The main parameters of these waves, i.e. propagation rate against work hardening coefficient, dispersion law and wavelength against specimen length and grain size, have been defined. The possibility of treating plastic flow localization as a process of plastic flow occurring in a deforming medium is considered. A set of equations has been developed, which is appropriate for the description of the evolution of local strain domains. The changes in the type of local strain pattern observed in the various stages of flow are examined. A model is proposed to account for the large-scale periodicities exhibited by the distribution of localized deformation.
65 citations
TL;DR: In this article, it was shown that the SYPOR project, using fully relativistic concepts, is an alternative to a mere copy of the GPS system, and that the Galileo system would be exact and there would be no need for relatvistic corrections.
Abstract: Today, the Global Navigation Satellite Systems, used as global positioning systems, are the GPS and the GLONASS. They are based on a Newtonian model and hence they are only operative when several relativistic effects are taken into account. The most important relativistic effects (to order 1/c2) are: the Einstein gravitational blue shift effect of the satellite clock frequency (Equivalence Principle of General Relativity) and the Doppler red shift of second order, due to the motion of the satellite (Special Relativity). On the other hand, in a few years the Galileo system will be built, copying the GPS system unless an alternative project is designed. In this work, it will be also shown that the SYPOR project, using fully relativistic concepts, is an alternative to a mere copy of the GPS system. According to this project, the Galileo system would be exact and there would be no need for relativistic corrections.
36 citations
TL;DR: In this paper, it was shown that in the conformal Brans-Dicke theory there are no isotropic Friedmann solutions of non-zero spatial curvature except for k=-1 case.
Abstract: Following recent fit of supernovae data to Brans-Dicke theory which favours the model with o = - 3/2 [1] we discuss the status of this special case of Brans-Dicke cosmology in both isotropic and anisotropic framework. It emerges that the limit o = -3/2 is consistent only with the vacuum field equations and it makes such a Brans-Dicke theory conformally invariant. Then it is an example of the conformal relativity theory which allows the invariance with respect to conformal transformations of the metric. Besides, Brans-Dicke theory with o = -3/2 gives a border between a standard scalar field model and a ghost/phantom model. In this paper we show that in o = -3/2 Brans-Dicke theory, i.e., in the conformal relativity there are no isotropic Friedmann solutions of non-zero spatial curvature except for k=-1 case. Further we show that this k=-1 case, after the conformal transformation into the Einstein frame, is just the Milne universe and, as such, it is equivalent to Minkowski spacetime. It generally means that only flat models are fully consistent with the field equations. On the other hand, it is shown explicitly that the anisotropic non-zero spatial curvature models of Kantowski-Sachs type are admissible in o = -3/2 Brans-Dicke theory. It then seems that an additional scale factor which appears in anisotropic models gives an extra deegre of freedom and makes it less restrictive than in an isotropic Friedmann case.
35 citations
TL;DR: In this paper, the authors present preliminary measurements with an NIS junction as a noise source, and a Josephson junction in the thermal escape regime as a detector, and compare the results with the theoretical description of thermal escape in the presence of noise with a non-zero third cumulant.
Abstract: Non-Gaussian fluctuations of the electrical current can be detected with a Josephson junction placed on-chip with the noise source. We present preliminary measurements with an NIS junction as a noise source, and a Josephson junction in the thermal escape regime as a noise detector. It is shown that the Josephson junction detects not only the average noise, which manifests itself as an increased effective temperature, but also the noise asymmetry. A theoretical description of the thermal escape of a Josephson junction in presence of noise with a non-zero third cumulant is presented, together with numerical simulations when the noise source is a tunnel junction with Poisson noise. Comparison between experiment and theory is discussed. Copyright line will be provided by the publisher
TL;DR: In this article, a more refined approach to the quantum theory of the (φ,I)-model of the harmonic oscillator (HO) is presented, which is not in contradiction to the usual approach in terms of the operators Q and P which are now expressed as functions of the Kj.
Abstract: In classical mechanics the harmonic oscillator (HO) provides the generic example for the use of angle and action variables and I > 0 which played a prominent role in the “old” Bohr-Sommerfeld quantum theory. However, already classically there is a problem which has essential implications for the quantum mechanics of the (φ,I)-model for the HO: the transformation is only locally symplectic and singular for (q,p) = (0,0). Globally the phase space {(q,p)} has the topological structure of the plane ℝ2, whereas the phase space {(φ,I)} corresponds globally to the punctured plane ℝ2 -(0,0) or to a simple cone with the tip deleted. From the properties of the symplectic transformations on that phase space one can derive the functions h0 = I, h1 = Icos φ and h2 = -Isin φ as the basic coordinates on {(φ,I)}, where their Poisson brackets obey the Lie algebra of the symplectic group of the plane. This implies a qualitative difference as to the quantum theory of the phase space {(φ,I)} compared to the usual one for {(q,p)}: In the quantum mechanics for the (φ,I)-model of the HO the three hj correspond to the self-adjoint generators Kj, j = 0,1,2, of certain irreducible unitary representations of the symplectic group or one of its infinitely many covering groups, the representations being parametrized by a (Bargmann) index k > 0. This index k determines the ground state energy of the (φ,I)-Hamiltonian . For an m-fold covering the lowest possible value for k is k = 1/m, which can be made arbitrarily small by choosing m accordingly! This is not in contradiction to the usual approach in terms of the operators Q and P which are now expressed as functions of the Kj, but keep their usual properties. The richer structure of the Kj quantum model of the HO is “erased” when passing to the simpler (Q,P)-model! This more refined approach to the quantum theory of the HO implies many experimental tests: Mulliken-type experiments for isotopic diatomic molecules, experiments with harmonic traps for atoms, ions and BE-condensates, with charged HOs in external electric fields and the (Landau) levels of charged particles in external magnetic fields, with the propagation of light in vacuum, passing through strong external electric or magnetic fields. Finally it may lead to a new theoretical estimate for the quantum vacuum energy of fields and its relation to the cosmological constant.
TL;DR: In this paper, the nonlocal theory of accelerated systems is extended to linear gravitational waves as measured by accelerated observers in Minkowski spacetime, and the results of this study, via Einstein's heuristic principle of equivalence, provide the incentive for a nonlocal classical theory of the gravitational field.
Abstract: The nonlocal theory of accelerated systems is extended to linear gravitational waves as measured by accelerated observers in Minkowski spacetime. The implications of this approach are discussed. In particular, the nonlocal modifications of helicity-rotation coupling are pointed out and a nonlocal wave equation is presented for a special class of uniformly rotating observers. The results of this study, via Einstein's heuristic principle of equivalence, provide the incentive for a nonlocal classical theory of the gravitational field.
TL;DR: In this paper, the relation between counting statistics and the field theory of electric circuits is discussed and the Coulomb effects in this limit are presented as quantum corrections that can strongly renormalize the action at low energies.
Abstract: We review the relations between the full counting statistics and the field theory of electric circuits. We demonstrate that for large conductances the counting statistics is determined by non-trivial saddle-point of the field. Coulomb effects in this limit are presented as quantum corrections that can strongly renormalize the action at low energies.
TL;DR: In this article, a class of continuous renormalization group flows with a dynamical adjustment of the propagator is introduced and studied theoretically for fermionic and bosonic quantum field theories.
Abstract: A class of continuous renormalization group flows with a dynamical adjustment of the propagator is introduced and studied theoretically for fermionic and bosonic quantum field theories. The adjustment allows to include self–energy effects nontrivially in the denominator of the propagator and to adapt the scale decomposition to a moving singularity, and hence to define flows of Fermi surfaces in a natural way. These flows require no counterterms, but the counterterms used in earlier treatments can be constructed using them. The influence of propagator adjustment on the strong–coupling behaviour of flows is examined for a simple example, and some conclusions about the strong coupling behaviour of renormalization group flows are drawn.
TL;DR: In this article, the authors investigate the noise properties of pump currents through molecular wires and coupled quantum dots and derive a master equation formalism for the computation of the current and the zero-frequency noise.
Abstract: We investigate the noise properties of pump currents through molecular wires and coupled quantum dots. As a model we employ a two-level system that is connected to electron reservoirs and is non-adiabatically driven. Concerning the electron-electron interaction, we focus on two limits: non-interacting electrons and strong Coulomb repulsion. While the former case is treated within a Floquet scattering formalism, we derive for the latter case a master equation formalism for the computation of the current and the zero-frequency noise. For a pump operated close to internal resonances, the differences between the non-interacting and the strongly interacting limit turn out to be surprisingly small.
TL;DR: In this article, the pseudorapidity distribution of charged hadrons in heavy-ion collisions in Relativistic Diffusion Model (RDM) was investigated. And the energy and centrality dependence of rapidity distributions of net protons, and pseudoreapidity distributions of produced charged particles were obtained and discussed in a three-sources model at LHC energies.
Abstract: We investigate stopping and particle production in heavy-ion collisions in a Relativistic Diffusion Model (RDM). Using three sources for particle production, the energy- and centrality dependence of rapidity distributions of net protons, and pseudorapidity distributions of charged hadrons in heavy systems at RHIC energies are precisely reproduced in the analytical model. The transport coefficients are then extrapolated from Au + Au at RHIC energies ( p sNN =19.6 - 200 GeV) to Pb + Pb at LHC energies of p sNN = 5.52 TeV. Rapidity distributions for net protons, and pseudorapidity spectra for produced charged particles are obtained and discussed in a three-sources model at LHC energies.
TL;DR: In this paper, the authors considered the two-spin equation that describes four-level quantum systems and showed that the problem for certain external backgrounds can be identified with the problem of one spin in an appropriate background.
Abstract: In the present article, we consider the so-called two-spin equation that describes four-level quantum systems. Recently, these systems attract attention due to their relation to the problem of quantum computation. We study general properties of the two-spin equation and show that the problem for certain external backgrounds can be identified with the problem of one spin in an appropriate background. This allows one to generate a number of exact solutions for two-spin equations on the basis of already known exact solutions of the one-spin equation. Besides, we present some exact solutions for the two-spin equation with an external background different for each spin but having the same direction. We study the eigenvalue problem for a time-independent spin interaction and a time-independent external background. A possible analogue of the Rabi problem for the two-spin equation is defined. We present its exact solution and demonstrate the existence of magnetic resonances in two specific frequencies, one of them coinciding with the Rabi frequency, and the other depending on the rotating field magnitude. The resonance that corresponds to the second frequency is suppressed with respect to the first one.
TL;DR: Onsager, Mittag, and Stephen [Ann. Physik (Leipzig 18, 71 (1966)] have obtained their famous analytical expression e2x = (in atomic units) for the correlation energy in second order of exchange as mentioned in this paper.
Abstract: The on-shell self-energy of the homogeneous electron gas in second order of exchange, Σ2x = Re Σ2x (kF, k2F/2), is given by a certain integral. This integral is treated here in a similar way as Onsager, Mittag, and Stephen [Ann. Physik (Leipzig) 18, 71 (1966)] have obtained their famous analytical expression e2x = (in atomic units) for the correlation energy in second order of exchange. Here it is shown that the result for the corresponding on-shell self-energy is Σ2x = e2x. The off-shell self-energy Σ2x (k, o) correctly yields 2e2x (the potential component of e2x) through the Galitskii-Migdal formula. The quantities e2x and Σ2x appear in the high-density limit of the Hugenholtz-van Hove (Luttinger-Ward) theorem.
TL;DR: In this article, the counting statistics of charge transport in the Anderson impurity model (AIM) employing both Keldysh perturbation theory in a Fermi liquid picture and the Bethe ansatz was studied.
Abstract: We study the counting statistics of charge transport in the Anderson impurity model (AIM) employing both Keldysh perturbation theory in a Fermi liquid picture and the Bethe ansatz. In the Fermi liquid approach, the object of our principal interest is the generating function for the cumulants of the charge current distribution. We derive an exact analytic formula relating the full counting statistic (FCS) generating function to the self-energy of the system in the presence of a measuring field. We first check that our approach reproduces correctly known results in simple limits, like the FCS of the resonant level system (AIM without Coulomb interaction). We then proceed to study the FCS for the AIM perturbatively in the Coulomb interaction. By comparing this perturbative analysis with a strong coupling expansion, we arrive at a conjecture for an expression for the FCS generating function at (V3) (V is the voltage across the impurity) valid at all orders in the interaction. In the second part of the article, we examine a Bethe ansatz analysis of the current noise for the AIM. Unlike the Fermi liquid approach, here the goal is to obtain qualitative, not quantitative, results for a wider range of voltages both in and out of a magnetic field. Particularly notable are finite field results showing a double peaked structure in the current noise for voltages satisfying eV ∼ μBH. This double peaked structure is the “smoking gun” of Kondo physics in the current noise and is directly analogous to the single peak structure predicted in the differential conductance of the AIM.
TL;DR: In this paper, the acceleration-induced nonlocality and the corresponding Lorentz-invariant nonlocal field equations of accelerated systems in Minkowski spacetime are discussed.
Abstract: Acceleration-induced nonlocality and the corresponding Lorentz-invariant nonlocal field equations of accelerated systems in Minkowski spacetime are discussed. Under physically reasonable conditions, the nonlocal equation of motion of the field can be derived from a variational principle of stationary action involving a nonlocal Lagrangian that is simply obtained by composing the local inertial Lagrangian with the nonlocal transformation of the field to the accelerated system. The implications of this approach for the electromagnetic and Dirac fields are briefly discussed.
TL;DR: In this article, the Lanczosspintensor was used to obtain a Lanczos superpotential for G¨odel spacetime, which is very useful in the analysis of the Li´enard-Wiechert equation.
Abstract: in general relativity is given in [3]. Besides, the idea of the “Lanczosspintensor” is very useful in the analysis [4] of the Li´enard-Wiechert field [5].Given the Weyl tensor, it may be very difficult to obtain a Lanczos superpotential by integrating directly(2), but here we shall show one solution of (2) for G¨odel spacetime [6], with the interesting structure:
TL;DR: In this paper, it was shown that not all linear electromagnetic constitutive laws will define almost-complex structures on the bundle of 2-forms on the spacetime manifold when composed with the Poincare duality isomorphism.
Abstract: It is shown that not all linear electromagnetic constitutive laws will define almost-complex structures on the bundle of 2-forms on the spacetime manifold when composed with the Poincare duality isomorphism, but only a restricted class of them that includes linear spatially isotropic and some bi-isotropic constitutive laws. Although this result does not trivialize the formulation of the basic equations of pre-metric electromagnetism, it does affect their reduction to metric electromagnetism by its effect on the types of media that are reducible, and possibly its effect on the way that such media support the propagation of electromagnetic waves.
TL;DR: In this paper, an account is given of an interesting but unknown theory by Majorana regarding scalar quantum electrodynamics, elaborated several years before the known Pauli-Weisskopf theory.
Abstract: An account is given of an interesting but unknown theory by Majorana regarding scalar quantum electrodynamics, elaborated several years before the known Pauli-Weisskopf theory. Theoretical calculations and their interpretation are given in detail, together with a general historical discussion of the main steps towards the building of a quantum field theory for electrodynamics. A possible peculiar application to nuclear constitution, as conceived around 1930, considered by Majorana is as well discussed.
TL;DR: In this paper, a semiclassical expansion of quantum characteristics for many-body scattering problem is presented and tools for calculation of average values of time-dependent physical observables and cross sections.
Abstract: In quantum mechanics, systems can be described in phase space in terms of the Wigner function and the star-product operation. Quantum characteristics, which appear in the Heisenberg picture as the Weyl's symbols of operators of canonical coordinates and momenta, can be used to solve the evolution equations for symbols of other operators acting in the Hilbert space. To any fixed order in the Planck's constant, many-body potential scattering problem simplifies to a statistical-mechanical problem of computing an ensemble of quantum characteristics and their derivatives with respect to the initial canonical coordinates and momenta. The reduction to a system of ordinary differential equations pertains rigorously at any fixed order in ħ. We present semiclassical expansion of quantum characteristics for many-body scattering problem and provide tools for calculation of average values of time-dependent physical observables and cross sections. The method of quantum characteristics admits the consistent incorporation of specific quantum effects, such as non-locality and coherence in propagation of particles, into the semiclassical transport models. We formulate the principle of stationary action for quantum Hamilton's equations and give quantum-mechanical extensions of the Liouville theorem on conservation of the phase-space volume and the Poincare theorem on conservation of 2p-forms. The lowest order quantum corrections to the Kepler periodic orbits are constructed. These corrections show the resonance behavior.
TL;DR: In this paper, the authors review recent advances in the field of full counting statistics (FCS) of charge transfer through impurities imbedded into strongly correlated one-dimensional metallic systems, modelled by Tomonaga-Luttinger liquids.
Abstract: We review recent advances in the field of full counting statistics (FCS) of charge transfer through impurities imbedded into strongly correlated one-dimensional metallic systems, modelled by Tomonaga-Luttinger liquids (TLLs). We concentrate on the exact analytic solutions for the cumulant generating function, which became available recently and apply these methods in order to obtain the FCS of a non-trivial contact between two crossed TLL.
TL;DR: In this article, the authors show that two-particle processes are not related to a particular geometry but are a general feature of multiparticle observables like shot noise correlations and discuss in addition structures in which twoparticle interference effects are generated dynamically by varying electrostatic potentials with the help of gates or by generating electron-hole pairs by irradiating contacts of a mesoscopic conductor.
Abstract: Theory predicts that electrons emitted from independent electron sources (metallic contacts) can nevertheless interfere. This interference is manifest in an exchange contribution to the shot noise correlation of currents at different contacts of a mesoscopic conductor. A geometry has been proposed in which second order (single particle) interference due to superposition of amplitudes is absent but fourth order (two-particle) interference exhibits Aharonov-Bohm oscillations. Recently such a geometry has been realized in an experiment and the theoretically predicted two-particle Aharonov-Bohm effect has been detected. We discuss Bell measurements and quantum state tomography using shot noise correlations. We discuss in addition structures in which two-particle interference effects are generated dynamically by varying electrostatic potentials with the help of gates or by generating electron-hole pairs by irradiating contacts of a mesoscopic conductor. These examples emphasize that two-particle processes are not related to a particular geometry but are a general feature of multiparticle observables like shot noise correlations.
TL;DR: In this paper, the authors studied the Berry phase of two atoms exposed to the same quantized light field and found that the interaction between each atom and the light field obeys the Jaynes-Cummings model.
Abstract: The Berry phase of two atoms exposed to the same quantized light field has been studied. The interaction between each atom and the light field obeys the Jaynes-Cummings model. Due to the quantization of the light field, the interaction Hamiltonians for the two atoms interacting with the field do not commute with each other, which induces new parts in the Berry phase. Meanwhile, there appears a phase which doesn't exist in the classical regime and is purely induced by the field quantization.
TL;DR: In this article, the local field contribution to some three-and four-level coherent atomic vapors is considered, and a significant modification to optical properties due to dipole-dipole interaction between neig...
Abstract: The local field contribution to some three- and four-level coherent atomic vapors is considered, and a significant modification to optical properties due to dipole-dipole interaction between neig ...
TL;DR: In this paper, an explicit demonstration of a harmonic oscillator in equilibrium approaching the equilibrium of a corresponding interacting system by coupling it to a thermal bath consisting of a continuum of harmonic oscillators is given.
Abstract: An explicit demonstration is given of a harmonic oscillator in equilibrium approaching the equilibrium of a corresponding interacting system by coupling it to a thermal bath consisting of a continuum of harmonic oscillators.