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We reconsider the all-optical homodyne-measurement based experimental schemes that aim to reveal Bell nonclassicality of a single photon, often termed `nonlocality'. We focus on the schemes put forward by Tan, Walls and Collett (TWC, 1991) and Hardy (1994). In the light of our previous work the Tan, Walls and Collett setup can be described by a precise local hidden variable model, hence the claimed nonclassicality of this proposal is apparent, whereas the nonclassicality proof proposed by Hardy is impeccable. In this work we resolve the following problem: which feature of the Hardy's approach is crucial for its successful confirmation of nonclassicality. The scheme of Hardy differs from the Tan, Walls and Collett setup in two aspects. (i) It introduces a superposition of a single photon excitation with vacuum as the initial state of one of the input modes of a 50-50 beamsplitter, which creates the superposition state of two separable (exit) modes under investigation. (ii) In the final measurements Hardy's proposal utilises a varying strengths of the local oscillator fields, whereas in the TWC case they are constant. In fact the local oscillators in Hardy's scheme are either on or off (the local setting is specified by the presence or absence of the local auxiliary field). We show that it is the varying strength of the local oscillators, from setting to setting, which is the crucial feature enabling violation of local realism in the Hardy setup, whereas it is not necessary to use initial superposition of a single photon excitation with vacuum as the initial state of the input mode. Neither one needs to operate in the fully on/off detection scheme. Despite the failure of the Tan, Walls and Collett scheme in proving Bell nonclassicality, we show that their scheme can serve as an entanglement indicator., 15 pages, 6 figures. Comments are welcome

We consider the interaction between the Earth's gravitational field and a superconductor in the fluctuation regime. Exploiting the weak field expansion formalism and using time dependent Ginzburg-Landau formulation, we show a possible short-time alteration of the gravitational field in the vicinity of the superconductor., Comment: 5 pages, 4 figures

The electronic structures of nicotine, nicotinic acid and nicotinamide have been studied by valence photoemission spectroscopy (PES), core X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorp- tion fine structure (NEXAFS) and interpreted with the aid of quantum chemical calculations. Nicotinamide and nicotinic acid are closely related and show correspondingly similar spectral features, while nicotine is both struc- turally and spectroscopically diverse

The article substantiates the necessity of developing a theoretical model to study the influence of non-stationary processes on the shape of the recorded NMR signal in a weak magnetic field. Therefore, comparison of different ways of solving Bloch’s equations to describe the shape of the recorded NMR signals using a modulation technique is carried out. Moreover, mathematical models have been developed to describe the shape of the NMR signal, considering the peculiarities of its registration using modulation techniques in a weak field. Finally, the results of calculations, obtained by proposed methods, are compared with experimental data.

It is shown that polynomial gravity theories with more than four derivatives in each scalar and tensor sectors have a regular weak-field limit, without curvature singularities. This is achieved by proving that in these models the effect of the higher derivatives can be regarded as a complete regularization of the delta-source. We also show how this result implies that a wide class of non-local ghost-free gravities have a regular Newtonian limit too, and discuss the applicability of this approach to the case of weakly non-local models., 18 pages. Matches the version published in JCAP

The paper discusses the need to develop a new approximation of the nuclear magnetic resonance signals. This approximation allows enhancing functional capabilities of express control devices. The universal mathematical model is developed to describe the shape of the NMR signals taking into account the peculiarities of their registration using a modulation technique in a weak field. The modeling results obtained are compared with experimental data.

We performed three-dimensional detection of magnetic nanoparticle (MNP) samples using the combination of a field-free line (FFL) and multiple pickup coils. In this method, two-dimensional maps of the signal fields generated by the MNP samples were used to reconstruct a three-dimensional image of the MNP concentration. In the experiment, a weak field gradient of the FFL (0.06–0.13 T m−1) was used. The degradation of the imaging quality owing to the weak field gradient was compensated using ten field maps. We successfully demonstrated the three-dimensional detection of two MNP samples. The Fe content of each sample was 10 and 20 μg and the spacing for both samples was 16 mm. The results confirm the effectiveness of the present method for MNP detection using a weak field gradient. We also quantitatively discuss how the imaging quality degrades when the field gradient is decreased.

Electron-positron pair production rate created from vacuum in the presence of an elliptically polarized laser field is investigated. By applying the technique of two level transition amplitude, a routine for obtaining pair production rate is presented, and approximate analytical expressions are given both for the low frequency strong field regime and the high frequency weak field regime. We found that for an elliptically polarized field, the electron-positron pair production rate decrease when the elliptic eccentricity increase in the high frequency weak field regime, however, in the low frequency strong field regime, there is almost the same electron-positron pair production rate as in the constant electric field case.

We study the tunneling of virtual matter-antimatter pairs from the quantum vacuum in the presence of a spatially uniform, time-dependent electric background composed of a strong, slow field superimposed with a weak, rapid field. After analytic continuation to Euclidean spacetime, we obtain from the instanton equations two critical points. While one of them is the closing point of the instanton path, the other serves as an Euclidean mirror which reflects and squeezes the instanton. It is this reflection and shrinking which is responsible for an enormous enhancement of the vacuum pair production rate. We discuss how important features of two different mechanisms can be analysed and understood via such a rotation in the complex plane. a) Consistent with previous studies, we first discuss the standard assisted mechanism with a static strong field and certain weak fields with a distinct pole structure in order to show that the reflection takes place exactly at the poles. We also discuss the effect of possible sub-cycle structures. We extend this reflection picture then to weak fields which have no poles present and illustrate the effective reflections with explicit examples. An additional field strength dependence for the rate occurs in such cases. We analytically compute the characteristic threshold for the assisted mechanism given by the critical combined Keldysh parameter. We discuss significant differences between these two types of fields. For various backgrounds, we present the contributing instantons and perform analytical computations for the corresponding rates treating both fields nonperturbatively. b) In addition, we also study the case with a nonstatic strong field which gives rise to the assisted dynamical mechanism. For different strong field profiles we investigate the impact on the critical combined Keldysh parameter. [...], Comment: 54 pages, 23 figures, revised, restructured to improve readability, matches journal version

The free electron gas in a uniform magnetic field at low temperature is restudied. The grand partition function previously obtained by Landau's quantitative calculation contains three parts, which are all approximate. An improved calculation is presented, in which two of the three parts are obtained in exact forms. A simple remedy for Landau and Lifshitz's qualitative calculation in the textbook is also given, which turns the qualitative result into the same one as obtained by the improved quantitative calculation. The chemical potential is solved approximately and the thermodynamic quantities are calculated explicitly in both a weak field and a strong field. The thermodynamic quantities in a strong field obtained here contain both non-oscillating and oscillating corrections to the corresponding results derived from Landau's grand partition function. In particular, Landau's grand partition function is not sufficiently accurate to yield our nonzero results for the specific heat and the entropy. An error in the Laplace-transform method for the problem is corrected. The results previously obtained by this method are also improved.

Absorption and refraction of the inner transition F2↔F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1↔F3 and F2↔F4 are resonantly interacted with drive field with frequency ωc and Rabi frequency Ωc, and saturation field with ωs and Ωs, respectively. For the suitable Rabi frequencies Ωc and Ωs, we obtain the Mollow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F3 and simultaneously the saturation field takes the atom out of the lower level F2, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of Ωs. Finally, the refractive index enhancement is predicted for a wide spectral region.

The influence of magnetic field and microwave irradiation on dynamical phase separation in submicron Bi2Sr2CaCu2O8+x bridges has been studied. Strong effect on the shape and metastable character of the step-like I-V characteristics are found. Under a weak field H < 2 Oe and low level microwave irradiation the step-like structure of the I-V characteristics smears out and disappears completely. The average frequency of switching between metastable states grows by 5 orders under increase of magnetic field by only 1 Oe. This behavior is explained in terms of the model of dynamical vortex lines.

We try to carry over, as closely as possible, the well-known results for rotational dragging (Thirring, Brill and Cohen) to dragging due to linearly accelerated masses. To this end, a spherical, charged mass shell is linearly accelerated by a (weak) external, axisymmetric and dipolar charge distribution. It is shown that the interior of this (Reissner–Nordstrom-like) shell stays flat. The dragging of neutral test particles inside the shell, defined by their acceleration, scaled by the overall acceleration of the (rigid) shell, is calculated for the weak field case for a highly massive but weakly charged shell and for the general strong field case. The results compare favourably with the corresponding results for rotational dragging.

In the framework of parallelism general relativity, the torsion axial-vector in the rotating gravitational field is studied in terms of the alternative Kerr tetrad. In the case of the weak field and slow rotation approximation, we obtain that the torsion axial-vector possesses the dipole-like structure. Furthermore, the effect of massive neutrino spin precession in this field is mentioned.

We propose a novel electrostatic guiding scheme for cold polar molecules in weak-field-seeking states using a single charged wire half embanked in a ceramic substrate (i.e., a chip) and a homogeneous bias electric field, which is produced by a capacitor composed of two large parallel metal plates. We calculate the spatial distribution of the electrostatic fields generated by the combination of the charged wire and the plate capacitor and the corresponding trapping potentials for CO molecules, and analyse the relationships between the electric field and the parameters of the charged-wire layout. Our study shows that the proposed scheme with a single charged-wire can be used to guide cold polar molecules in the weak-field-seeking states, and has some potential applications in construction of various molecule-optical elements.

Relativistic astrometry has recently become an active field of research owing to new observational technologies which allow for accuracies of a microarcsecond. To assure this accuracy in data analysis, one has to perform ray tracing in a general relativistic framework including terms of the order of (v/c)3 in the weak field treatment of Einstein equations applied to the solar system. Basic to the solution of a ray tracing problem are the boundary conditions that one has to fix from the observational data. In this paper we solve this problem to (v/c)3 in a fully analytical way.

The c-number atomic Bloch equations modelling the coupling of a 2-photon 2-level single atom with a non-resonant ( ) squeezed vacuum (SV) radiation reservoir show that: (i) The quantum interference (QI) process, of parameter , between the 2-photon transition channels causes coupling of the atomic variables (inversion and polarisation), and, (ii) The SV reservoir parameters ( N, M ) induce periodic coefficients and hence inhibited oscillatory behaviour in the atomic variables. Perturbative analytical solutions of these non-autonomous Bloch equations are derived and used to calculate the absorption spectrum of a weak field probing the system. Of particular, the zero-absorption isolines in the relevant ( N, f )- and ( )-planes of the system parameters are identified computationally. It is found that, the largest set of points, where absorption is zero, in the -plane depends on the choice of the degree of squeezing parameter (M) of the SV reservoir.

In the context of the teleparallel equivalent of general relativity, we obtain the tetrad and the torsion fields of the stationary axisymmetric Kerr spacetime. It is shown that, in the slow rotation and weak field approximations, the axial-vector torsion plays the role of the gravitomagnetic component of the gravitational field, and is thus the responsible for the Lense-Thirring effect., 9 pages, no figures, to appear in Class. Quant. Grav

We develop a quantum-mechanical approach to the photoassociation phenomenon in a sample of cold atoms initially at thermal equilibrium with temperature T. We calculate the rate of formation of molecules in the weak field regime using a perturbative approach. Analytical expressions are obtained for the overlap between the initial and final molecular wavefunctions, and are shown to agree with numerical calculations. The photoassociation rate is found to decrease with increasing atomic mass m, from Li to Cs. Also considered is the heating of the atomic sample through spontaneous photodissociation.

The many-electron weak-field asymptotic theory of tunneling ionization including the first-order correction terms in the asymptotic expansion of the ionization rate in field strength was highlighted in our recent fast track communication (Trinh et al 2015 J. Phys. B: At. Mol. Opt. Phys. 48 061003) by demonstrating its performance for two-electron atoms. Here we present a thorough derivation of the first-order terms omitted in the previous publication and provide additional numerical illustrations of the theory.

Bi1.7Pb0.3Sr2Ca2Cu3O10-y samples prepared by the glass precursor route were examined. A.c. susceptibility properties were studied and compared to those of samples obtained by the solid-state route. The interconnected lattice of 2223 needle-like grains in a matrix of strontium, calcium, and copper small and globular precipitates of irregular shape leads to an interesting behaviour of the critical current density as a function of d.c. field: there is high intergrain Jc and weak field dependence (Jc > 105 A/cm2 at 77 K and 0 T), in contrast to Jc values and field dependence of classical solid-state route samples. It can thus be claimed (unambiguously now) that the intricate superconducting grain boundary structure acts as the ingredient for improved pinning at low d.c. field at least in such systems.

It has been shown that coherence effects have a marked influence in the spontaneous emission spectrum of a three-level -type atom driven by weak coherent and incoherent fields. Phase dependent evolution of interference effects leading to spectral narrowing, generation of spectral hole and dark line are exhibited in the present scheme when the atom does not interact with the incoherent fields. The basic mechanism underlying this scheme seems to be appropriate for a phaseonium. Apart from phase-coherence introduced in the system the phenomenon of line narrowing, in the presence of weak incoherent pumping, can be achieved in a different way as a consequence of two competitive resonant effects: sharp non-Lorentzian and symmetric Fano-like-resonance contributions to the line shape. In both the situations, the evolution of narrow structures in the line shape can be achieved even when the emission is influenced by the dephasing of Raman coherence.

We develop an analytical approach on electromagnetically induced transparency (EIT) in a Doppler broadened medium consisting of five-level cascade systems excited by a strong coupling and weak probe laser fields. In a weak field limit of the probe light, EIT spectrum is interpreted as functions of controllable parameters of the coupling light and temperature of the medium. The theoretical interpretation of EIT spectrum is applied to the case of 85Rb atoms and compared with available experimental observation. Such an analytical interpretation provides quantitative parameters to control properties of the Doppler broadened EIT medium, and it is useful to find related applications.

The electrical field dependence of the emission properties of DX-related centres in silicon-doped AlxGa1-xAs was studied by applying the measurement technique of reverse-bias pulsed deep-level transient spectroscopy (RDLTS) previously suggested by Li and Wang. Using this technique two well resolved RDLTS peaks were obtained which could be studied separately. Almost perfect exponential capacitance transients revealed a rather weak field dependence of both the emission rates and emission barriers. The zero-field thermal activation energies of the two DX-related states were found to be 311 meV and 368 meV respectively by extrapolating the experimental data to vanishing electric field.

Wires and tapes of Bi-based superconductors have been produced by the standard powder in tube technique, using silver sheaths. Different geometries of samples have been processed, including single core wires, multi-filamentary wires and tapes. For each configuration both straight samples as well as coils have been prepared and electrically characterized at 77 K at zero field and at 4.2 K in magnetic fields up to 15 T. At 77 K straight samples exhibit critical current densities up to 8000 A/cm2 at zero magnetic field and up 75000 A/cm2 at 4.2 K. Due to a very weak field dependence, Jc at 4.2 K at 15 T is still higher than 20000 A/cm2.

Parametrized post-Newtonian formalism is one of the standard methods of experimental check of gravity theories and limiting the model parameters. In this work we consider the PPN-paramertization of Randall-Sundrum II black hole solutions and show that these solutions are in good agreement with the GR predictions and the observation results.

We examine the continuum limit of the piecewise flat locally finite gravity model introduced by 't Hooft. In the linear weak field limit we find the energy--momentum tensor and metric perturbation of an arbitrary configuration of defects. The energy--momentum turns out to be restricted to satisfy certain conditions. The metric perturbation is mostly fixed by the energy--momentum except for its lightlike modes which reproduce linear gravitational waves, despite no such waves being present at the microscopic level., Comment: Accepted for publication in Classical and Quantum gravity

We propose a scheme to generate triple electromagnetically induced transparency (TEIT) where EIT is induced simultaneously for three weak slow light pulses. We calculate the complex polarizibilities and group velocities of the three slow light pulses in the weak field limit by means of the full Hamiltonian approach. It is shown that strong cross-phase modulation can be realized and large cross-phase shifts on the order of π radians can be generated for three slow weak pulses even if light pulses of ultrasmall energies, i.e. single photons, are involved. It is indicated that under certain conditions the three slow weak pulses can reach matching of group velocities in a single species of 87Rb atoms.

Measurements of nonresonance microwave absorption have been used to determine the position of the irreversibility line and to estimate the critical current density for the three SmO1?xFxFeAs samples with fluorine concentrations x = 0.06, 0.08, and 0.1. The irreversibility lines of all samples are characterized with a sharp slope, indicating a strong pinning up to Tc. A weak field dependence of the critical current density and an estimate of parameters characterizing the vortex matter allow us to suggest the presence of additional pinning centers in underdoped samples. It is likely that these pinning centers are nanoscale inclusions of a possibly magnetic phase occurring in the fluorine concentration range of 0.06?0.08.

We report the fabrication of Ta-sheathed superconducting SmFeAsO1−xFx wires by the powder-in-tube method for the first time. The transition temperature of the SmFeAsO0.65F0.35 wires was confirmed to be as high as 52 K. High critical fields Hc2(0)≥120 T as well as current density Jc of 3900 A cm−2 at 5 K were also demonstrated. It should be noted that the Jc exhibits a very weak field dependence behavior, indicating a very encouraging prospect for application of the new superconductors.

An asymptotic method is presented for solving the problem of a hydrogen atom perturbed by a uniform electric field F considered as a weak field. An asymptotic expansion for the level width Gamma is obtained. A comparison is given of the values of Gamma obtained using the asymptotic formulae with exact numerical results.

Discusses the theory of Doppler-free two-photon transitions. The theory is worked out for the case of one arbitrarily strong field and one weak field. The Doppler limit is assumed. These simplifications allow the authors to discuss the experimental manifestations of various parameters. They consider power shifts and broadening the number of resonant peaks and their positions. The general case of an off-resonant intermediate state and the single-frequency case with a resonant intermediate state are discussed. The former is found to lead to a power shift, whereas the latter is unshifted in a certain region. In addition the resonant case gives an enhancement without an appreciable increase in width.

A description is provided of the preparation of amorphous thin films by radio-frequency sputtering from a glass target of Si12Te48As30Ge10. The weak-field characteristics are investigated for a variety of electrode materials. Ohmic behaviour can be observed with chromium as an electrode material, provided atmospheric contamination is minimized. The use of aluminium as an electrode material gives rise to non-ohmic behaviour, even at the weakest fields.

The thermodynamic potential for independent electrons in a magnetic field is calculated by a method that arises from a more general Green function approach. Results are obtained in the weak field and the quantum limits.

This problem has a long history of confusion and error. One crucial question is whether the leading correction δμ/μ is of order α/mL or α/(mL)2, where L is the distance from or between the mirrors. For a particle of infinite mass but finite μ, δμ/μ is of order α/(μL)2 in the weak field limit B → 0. The same is true in quantum mechanics and remains true for a (non-second-quantized) Dirac electron.

The principle of Project MACETIE and the preliminary experiment are described. The basis of our plan is the thought that the goal of controlled thermonuclear fusion may be accessible by the multistage alternating processes of adiabatic compression and irreversible expansion of plasma. In the latter process, the plasma compressed by a strong magnetic field is expanded into a region of weaker magnetic field. A static consideration of this expansion suggests that plasma temperature will not change appreciably in this process, and a second adiabatic compression of plasma in the weak field may further increase its temperature. Preliminary experiments are being carried out to examine the foregoing principle of irreversible expansion.

An analysis is made of the interaction of three spatially separate standing Gaussian waves with an atomic beam. The case of a Doppler-broadened transition is considered. An expression is obtained for the correction to the resonance in the number of excited particles, the width of the correction being inversely proportional to the transit time between the waves. The analysis is carried out for a weak field. Numerical calculations of the amplitude and profile of the resonance are reported. The optimal (in respect of the field intensity) conditions for the observation of this resonance are determined.