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We show that in the weak field limit the light deflection alone cannot distinguish between different R + F [ g ( □ ) R ] models of gravity, where F and g are arbitrary functions. This does not imply, however, that in all these theories an observer will see the same deflection angle. Owed to the need to calibrate the Newton constant, the deflection angle may be model-dependent after all necessary types of measurements are taken into account.

Recently, He and Ma introduced a generic method to generate static, circular symmetric regular black holes in 2+1-dimensional gravity minimally coupled to nonlinear electrodynamics (NED). In their formalism, they considered spacetimes filled with pure radial electric field and as examples four different cases were studied. In accordance with their method, in the weak field limit, the regular black holes are supposed to reduce to the charged BTZ black hole and the NED Lagrangian admits the Maxwell linear theory. Inspired from their paper, in this Letter we address a common feature of the NED Lagrangian which has not been noticed by the author. It will be shown that the NED Lagrangians are actually hybrid functions whose behaviors at weak and strong field regimes are different. This is in analogy with its 3+1-dimensional counterpart which has been pointed out long ago by Bronnikov.

We report on an all-optical switching in a double ∧ four-level atom-cavity system both theoretically and experimentally. In this system, an extra coherence between two ground states is induced by two coupling lasers, thus the loss of the cavity field decreases. Then, we can use one weak field to control another weak field at low light levels. Compared to the three-level atom-cavity system, the power of the switching laser can be much weaker in the four-level atom-cavity system.

Electromagnetically induced transparency (EIT) in the five-level cascade scheme of 85Rb atoms is investigated by analytical method. In the weak field limit of the probe light, the linear susceptibility, absorption, and dispersion coefficients have been derived in analytical forms. Unusual EIT signatures of the system are studied in details.

We investigate the absorptive–dispersive properties of a weak field in a coupled semiconductor double-quantum-dot nanostructure. It is found that the enhanced index of refraction without absorption can be easily controlled via adjusting properly the corresponding parameters of the system. Our scheme opens the possibility to control index of refraction without absorption in a coupled semiconductor double-quantum-dot nanostructure.

We investigated the absorptive–dispersive property of a weak field in a four-level inverted-Y quantum well system. We find that the cycling field and relative phase of the applied fields can affect the absorptive–dispersive property of a weak field dramatically, which can be used to manipulate efficiently the ultrahigh index of refraction without absorption. Our study is much more practical than its atomic counterpart due to its flexible design and controllable quantum-interference effect. Thus, it may provide some new possibilities for technological applications in optoelectronics and solid-state optical communication

The formulation of gradient inelasticity models has generally been focused on the effects of additional size-dependent hardening on the material behavior. Recently, the formulation of such models has taken a step in the direction of phase-field-like modeling by considering non-convex contributions to energy storage in the material (e.g., [1] ). In the current work, two such models with non-convexity are compared with each other, depending in particular on how the inelastic deformation and (excess) dislocation density are modeled. For simplicity, these comparisons are carried out for infinitesimal deformation in a one-dimensional setting. In the first model, the corresponding displacement u and inelastic local deformation γ are modeled as global via weak field relations, and the dislocation density ρ is modeled as local via a strong field relation. In the second model, u and ρ are modeled as global, and γ as local, in this sense. As it turns out, both models generally predict the same inhomogeneous deformation and material behavior in the bulk. Near the boundaries, however, differences arise which are due to the model-dependent representation of the boundary conditions.

We propose and analyze a novel scheme to realize the large Kerr nonlinearity via electromagnetically induced transparency (EIT) in molecular magnets. This scheme uses two magnetic fields to induce spin coherence. We obtain the analytical expressions of linear susceptibility, self-Kerr, cross-Kerr susceptibility, phase shift and absorption coefficients. Last, we investigate the nonlinear dynamics of the weak field, and show that the dark and bright microwave soliton can form in the magnetic medium.

On 5 April 2008, a filament at the periphery of an active region was observed by the Extreme Ultraviolet Imager telescope aboard the STEREO-A spacecraft, which showed up as a prominence eruption in the field-of-view from STEREO-B. The filament at STEREO-A 304 A was first lengthened toward a region with weak overlying magnetic field so evolved as a large-scale one consisting of bright and dark threads twisting with each other, and then the portion below the weak field underwent an eruption. Meanwhile, the corresponding STEREO-B 304 A prominence threads exhibited a kinking structure and tilting motion, with its center deflecting from the radial direction. By using three-dimension (3D) reconstruction technology, we obtain the 3D topology for the kinked prominence when its apex arrived at 1.4 radii, from which a clockwise rotation of about 90 is found in the course of the eruption. By comparing the 3D structure with the magnetic-field configuration computed by using the Potential-Field Source-Surface (PFSS) model, it is suggested that the filament erupted against the rather weaker than stronger overlying magnetic field, which make it appear to tilt toward one side. (C) 2010 Elsevier B.V. All rights reserved.

article i nfo Article history: Received 24 September 2010 Accepted 29 October 2010 We theoretically examine the storage and retrieval of a light pulse in a medium comprised of four-level atoms of the V − Λ-type. The two intermediate levels are probed by a weak field and vacuum-induced coherence effects lead the system to transparency. The temporal variation of the intermediate levels' splitting is used as an external parameter which allows the transfer of the impinging field to a combination of spin coherences. An auxiliary and far-detuned control field in a standing-wave configuration is used to induce a variable photonic bandgap by cross-phase modulation. It is shown that dynamic control of such a bandgap can be used to coherently manipulate the previously stored probe pulse. We use a general scheme to take into account multiwave mixing effects and solve the combined Maxwell-Bloch equations for the relevant coherences. It is shown that the system acts as an all-optical router.

By recourse to information-theory tools, we study aspects of the dynamics of the interaction between a single trapped ion with a laser field. Despite its simplicity the model we use exhibits a broad range of intricate physical effects that are clearly detected by information quantifiers like Wherl’s entropy and Fisher’s measure. In particular, a sensible dynamical difference between single vs. multi-photon processes is detected.

Two models, derived in very different ways but both incorporating the symmetry constraints outlined in the previous paper, are developed for use in simulating Thellier-type palaeointensity experiments. These are then tested against experimental data which endorse them both as powerful tools. They predict that non-ideal behaviour due to MD grain content is sensitive not only to the protocol employed and the vector difference between the partial thermoremanent magnetisations (pTRMs) imparted in the laboratory and the natural remanent magnetisation (NRM), but also to the spacing of the temperature steps and the type of pTRM imparted during the remagnetisation stages. Consistent with experimental studies, the models predict that pTRM checks may fail despite no alteration occurring and that any double-stage experimental protocol will produce non-ideal results to some degree provided that MD grains are present. A single-heating (perpendicular or high-angle single heating) protocol is predicted to remove non-ideal effects provided that the grains obey the symmetry constraints perfectly. However, this remains to be experimentally tested and does not allow for the use of pTRM checks. Five straightforward recommendations for future palaeointensity studies to follow are outlined. These are designed to minimise non-ideal behaviour due to MD grains as far as possible while retaining the capacity to detect and reject those samples which will nonetheless produce significant errors.

Thermally induced coarsening of the chemically ordered domains in Pb(Mg1/3Ta2/3)O-3 (PMT) ceramics promotes the studying of dielectric behavior of the 1: 1 B-cations ordered PMN-style complex perovskites. In this work, PMT ceramics with different degrees of chemical order were prepared, and their dielectric, and ferroelectric properties of disordered and ordered ceramics were studied as a function of temperature, frequency, and electrical field. It was found that the weak field relaxor nature is insensitive to the chemical order, whereas some non-linear behaviors showed ordering-degree dependence at the low temperature range. (c) 2005 Elsevier Ltd. All rights reserved.

The aim of present work was to investigate the influence of magnetic fields exposure on neurite outgrowth in PC12 cells. The neurite number per cell, length of neurites and directions of neurite growth with respect to the direction of the magnetic field were analyzed after exposure to 50 Hz electromagnetic field for 96 h. A promotion was observed under a weak field (0.23 mT), as the average number of neurites per cell increased to 2.38±0.06 compared to 1.91±0.07 neurites/cell of the control dishes, while inhibition and directional outgrowth was evident under a relatively stronger field (1.32 mT). Our work shows that biological systems can be very sensitive to the strength of electromagnetic field.

The effect of currents of mass on bending of light rays is considered in the weak field regime. Following Fermat's principle and the standard theory of gravitational lensing, we derive the gravitomagnetic correction to time delay function and deflection angle caused by a geometrically-thin lens. The cases of both rotating and shifting deflectors are discussed.

The instability of plane surface of a liquid metal in an electric field is shown to arise in arbitrarily weak field, as distinct from the well-known Tonks–Frenkel instability which takes place only in sufficiently high field. Only an account for the atomic structure of the metal leads to finite strength of the critical field which provokes the instability; however, even in this case the critical field occurs essentially less than the Tonks–Frenkel field.

We present here a sketch of some numerical results offered by a micromagnetism code based on the resolution of the Landau–Lifchitz equation. We have computed equilibrium configurations and dynamic susceptibilities to a weak field for magnetic materials with non-uniform magnetization and finite size and shape: cubic particles, finite-sized films with stripe domains and platelets with in-plane magnetocrystalline anisotropy. The obtained results have been compared with analytical models and experimental results. Some non-trivial effects have been pointed out (like surface modes) and fine details can be disclosed by susceptibility maps.

A saturation dip has been observed recently by A. Kumar et al. [Chem. Phys. Lett. 297 (1998) 300] in degenerate four-wave mixing (DFWM) and two-color resonant four-wave mixing (TC-RFWM) spectra of jet-cooled CH. This observation suggests that expressions of the signal intensity established for double-resonance molecular spectroscopy in the weak field limit are no longer valid. While the line splitting has been explained, this is not the case for the asymmetry observed on this spectrum. Here, we clearly establish the origin of this asymmetry as resulting from the transverse molecular velocity which acts even for a small velocity component. The model conveniently reproduces line splitting and asymmetry.

We report on a two-photon resonant three-photon ionisation experiment performed on atomic barium with a sequence of two identical not transform-limited laser pulses in the weak field regime. We show that our results, obtained by a multimode nanosecond laser source, can be reproduced theoretically by using much shorter transform-limited pulses with the same spectral bandwidth.

Steady-state dynamics of a Lambda atom driven by two coherent fields is studied for arbitrary detunings, arbitrary incoherent pumping and coherent driving intensities. Effects of a strong probe on EIT are worked out. Features of EIT and LWI are presented in a new physical picture on the basis of the concepts of quantum interference and coherence. In the weak field regime, an absorption-gain profile is the subtraction of two Lorentzians with the same central frequency but different widths and heights. This case is mostly the result of quantum interference and coherence rather than the result of Autler–Townes level splitting. In a strong field regime, however, the profile is the addition of two Lorentzian-like components with different central frequencies but the same width, where Autler–Townes splitting and quantum interference are equally important.

A large number of epidemiological and experimental studies suggest that prolonged (>100 s) weak 50-60-Hz electric and magnetic field (EMF) exposures may cause biological effects(NIEHS Working Group, NIH, 1998; Bersani, 1999). We show, however, that for typical temperature sensitivities of biochemical processes, realistic temperature variations during long exposures raise the threshold exposure by two to three orders of magnitude over a fundamental value, independent of the biophysical coupling mechanism. Temperature variations have been omitted in previous theoretical analyses of possible weak field effects, particularly stochastic resonance (Bezrukov and Vodyanoy 1997a. Nature. 385:319-321; Astumian et al., 1997 Nature. 338:632-633; Bezrukov and Vodyanoy, 1997b. Nature. 338:663; Dykman and McClintock, 1998. Nature. 391:344; McClintock, 1998;. Gammaitoni et al., 1998. Rev. Mod. Phys. 70:223-287). Although sensory systems usually respond to much shorter (approximately 1 s) exposures and can approach fundamental limits (Bialek, 1987 Annu. Rev. Biophys. Biophys. Chem. 16:455-468; Adair et al, 1998. Chaos. 8:576-587), our results significantly decrease the plausibility of effects for nonsensory biological systems due to prolonged, weak-field exposures.

A weak field DNP study of 4-hydroxy-2,2,6, 6-tetramethyl-1-piperidinyloxy (4-hydroxy-TEMPO), 4-amino-2,2,6, 6-tetramethyl-1-piperidinyloxy (4-amino-TEMPO), and 2, 2-Di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) free radicals invarious solvents was performed at 1.53 mT using a doubleresonance spectrometer. pi transitions, in which the RF fieldhas a component perpendicular to the static magnetic fieldB0, and final sigma transitions, in which the RF field has a component parallel to B0, were recorded. In order to observe thefinal sigma transitions a new probe head was designed. The final sigma transitions were obtained at the frequencies expected from theoretical calculations. However, the results obtained for the observed enhancements deviated from the values expectedtheoretically.

The weak field dielectric aging behaviours of lead magnesium niobate (Pb[Mg1/3Nb2/3]O3) ceramics have been extensively investigated. In this paper, however, we focused on the dielectric aging of a Mg and Mn doped PMN ceramic under various alternating current (ac) fields. It is found that the strong ac fields generally suppress the aging rate, particularly at low measurement frequencies.

It is shown that in the weak field approximation solutions of Brans-Dicke equations are simply related to the solutions of General Relativity equations for the same matter distribution. A simple method is developed which permits to obtain Brans-Dicke solutions from Einstein solutions when both theories are considered in their linearized forms. To illustrate the method some examples found in the literature are discussed., Comment: 12 pages, latex, no figures

The mean displacement moments for the strong field trapping model are calculated. Their asymptotic behaviour is 〈Xn(t)〉 ∼ (Vefft)n, where Veff is an effective drift velocity. This is in sharp contrast with the weak field case, for which 〈X n (t)〉 ∼ t n 3 . The mean survival (first passage) time and the upstream and downstream trapping probabilities are also obtained.

We discuss the Wilson renormalization group approach to the effective action for low $x$ physics. It is shown that in the linearized, weak field regime the RG equation reduces to the BFKL equation for the evolution of the unintegrated gluon density. We discuss the relation of this approach with that of Lipatov., Comment: 23 pages, latex, requires axodraw.sty

The order dependent mapping method, its convergence has recently been proven for the energy eigenvalue of the anharmonic oscillator, is applied to re-sum the standard perturbation series for Stark effect of the hydrogen atom. We perform a numerical experiment up to the fiftieth order of the perturbation expansion. A simple mapping suggested by the analytic structure and the strong field behavior gives an excellent agreement with the exact value for an intermediate range of the electric field, $0.03\leq E\leq0.25$. The imaginary part of the energy (the decay width) as well as the real part of the energy is reproduced from the standard perturbation series., Comment: 14 pages, 8 figures

The preparation of thick films of the NdBa 2 Cu 3 O y (Nd-123) phase by using partial-melting techniques (PMT) of powders deposited on MgO substrates by drying alcoholic suspensions is reported. The effects of the starting composition and processing conditions (temperature and annealing time) on the superconducting properties of the Nd 1+ x Ba 2 Cu 3 O y (0.0≤ x ≤0.50) system were investigated. An improvement of the quality of the films in the NdBaCuO system, as far as the microstructure and magnetic properties are concerned, was observed in the samples with nonstoichiometric starting compositions; the growth of the Nd-123 phase with tetragonal symmetry was detected for x = 0.5. The magnetization measurements, performed on samples annealed in O 2 , showed a T c as high as 91.5 K and a weak field dependence due to the effectiveness of the pinning centers.

Malonamide forms neutral 12 complexes MX2(LH2)2 with first row transition metals (M  Mn, Fe, Co, Ni, Cu, Zn; X  Cl, Br, I, NCS, ONO2; LH2  H2NCOCH2CONH2). 11 CuX2(LH2)1 (X  Cl, Br) could also be isolated. In alkaline medium, malonamide forms anionic complexes (ML2)2−.xH2O (M  Ni, Cu). A complete vibrational analysis (infrared and Raman spectroscopy) has been worked out and the metal—ligand vibrations clearly prove the weak field in the octahedral MX2(LH2)2 complexes. Spectroscopic evidence for the Jahn—Teller effect in the Cu complex is given by the metal—ligand vibrations, the hydrogen bonding and the Raman intensities of the ν(CO) and ν(CN).

It is demonstrated, with specific application to pump—dump control, that optimal control problems are substantially simplified by focusing on the regime of weak laser fields. Under such circumstances complex nonlinear problems of strong field optimal control are replaced by far simpler numerical tasks.

A revised form of the magnetic current-density equation which includes the temperature gradient as a driving force is presented for the weak field limit. The equation, which is based on a perturbation solution of the Boltzmann transport equation, has been reduced to a form that can be readily incorporated into existing magnetic-sensor simulation code. Various assumptions have been introduced in the simplification process and a qualitative discussion of the errors associated with these assumptions is presented.

The D(d, p) reaction was used to measure the vector polarization of the deuteron beam from the atomic beam polarized ion source at King Fahd University of Petroleum and Minerals. The vector polarized deuteron beam was produced using a weak field transition. The polarization pz of the deuteron beam was determined from the measured asymmetry and known analyzing power Ay(θ) of the D(d, p) reaction with 200 keV deuterons. The experimentally determined value of pz was found to be −0.462±0.029 which is 69±6% of the maximum theoretical value. Within the statistical uncertainties, the measured beam polarization agrees with the value given by the manufacturer.

The effects of coherence and interference in light-matter systems are treated using a novel causality preserving density matrix formulation that operates in a mixed time-frequency domain and applies to quantum as well as classical systems. Within the limits of the classical weak field and the rotating wave approximations, this formulation can be applied to arbitrary light fields, including incoherent light, transform limited ultrashort light pulses, chirped pulses, and phase-locked pulses. The light field function and the response function of the material system can be separately evaluated, and then convoluted in time and frequency to give the optical signal.

Recent experimental studies on quantum wires subjected to a doubly-corrugated gate displayed periodic oscillations in the weak field magneto-resistance [1]. The presence of peaks in the magneto-resistance were associated with specific ballistic backscattered trajectories that were highly sample (and thus geometry) dependent. In this paper we describe simulations of such structures.

A general form of the gain formula for the Compton-type free-electron laser with electromagnetic fields of any polarization and field strength is presented. In the case of circularly polarized fields, the result is reduced to the Chan-Tsui formula and can also be further reduced to the Colson formula by means of the first order “weak field” approximation.

The recently constructed magnetochemical series for weak field anionic ligands, based on a sensitive ranking of the degree of admixture in S = 3 2 , 5 2 spin state complexes of the type FeX(porphyrin) and FeX(phthalocyanin), can be extended to stronger field ligands X− by considering zero field splitting and spin crossover information available in the iron porphyrin literature. This leads to the ligand field strength ordering

The effects of magnetic field on terahertz radiation emitted from the rectangular mesa of intrinsic Josephson junctions (IJJ’s) made of Bi2212 single crystals were studied up to 150 Oe. Strong suppression of the radiation power was observed when magnetic field was applied to the c -axis of the sample, while in the case of H // ab -plane, the radiation power showed a weak and broad peak in the weak field region (∼50 Oe), then it decreased and diminished around 150 Oe. These magnetic field effects are interpreted by the strong influence of magnetic field on the I – V curve, which set up the condition for the THz radiation.

A stability of the bond spin-density-wave ( SDW ) phase observed in the one-dimensional half-filled anisotropic extended Hubbard model is discussed in the staggered magnetic field. A renormalization group (RG) analysis using the effective Hamiltonian implies that, due to the charge distribution in the SDW , the staggered magnetic field is irrelevant to its spin-liquid part, so it may survive in the weak field region. To determine its stable region, we employ a numerical procedure based upon the level-spectroscopy method and confirm our RG argument.

The superconductor strip weak-field geometrical barrier is calculated employing the pertaining exact response and vortex structure. The barrier shape entails two near-strip-edge minima. The commonly-employed single-minimum barrier (E. Zeldov, Ref. (1)) is qualitatively recovered for a stronger applied field.

We have measured magnetization and its relaxation of Bi-Sr-Ca-Cu-0 oriented films for wide ranges of temperature and field. The magnetization curves measured in the field along c-axis exhibit that the field of irreversibility limit, H 0 (T), deviates from a (1-T/T c ) 3/2 dependence below 40 K. The magnetization decays logarithmically with time in relatively weak field, whereas the simple logarithmic decay doesn’t hold in fields near H 0 .

The results of direct measurements of the diamagnetic shift of axciton levels in narrow quantum wells of a thickness varying between 25 and 150 A are reported. A perturbation type approach is used to calculate the diamagnetic shift of 1 s exciton levels in quantum well structures of Ga 1− x Al x As - GaAs - Ga 1− x Al x As . The calculations are applicable in the weak field range for which the Coulomb energy dominates over the magnetic one. The experimental results are in satisfactory agreement with the theory throughout the entire well thicknesses range.

We present a theory for the Raman lineshape of a three level system (a, b and c) being driven by a strong radiation field and perturbed by dephasing collisions. The present theory is not limited to the impact limit of fast collisions and incorporates properly the dynamics of the collisions. The final expression is given in terms of the three ordinary weak field line-shapes corresponding to the ab, bc and ac transitions. Numerical calculations are presented and the qualitative and quantitative differences between the impact and non-impact regions are discussed.

Virtual pair creation in a strong, virtual, bremsstrahlung field is considered in QED as a model for parton saturation. In a weak field the virtual pair density increases quadratically in the external field; however, at large values of the field the number density becomes independent of the strength of that field. A similar effect is found in scalar electrodynamics.

The gain formula for the free-electron laser obtained from the simple pendulum equation by means of the weak field approximation is shown to be incompatible with the experimental condition of the Stanford first free-electron laser amplifier.

The temperature dependence of the slope exponential absorption edge of glasses Ge20SbxS80−x (for x = 5, 10, 20, 25) has been determined and the results described using Mahr's formula. Adopting the idea of phonons-generated microfields given by Yacobi et al., the temperature shift of exponential edge is described in the weak field approximation of Franz.

We have examined the temperature dependence of the magnetic field penetration depth λ of YBa 2 Cu 3 O 7−δ and La 1.85 Sr 0.15 CuO 4 through variations of the ac susceptibility. We found that the T dependence of λ ( T ) − λ (0) reasonably explains the ac susceptibility profile of YBa 2 Cu 3 O 7−δ at lower temperatures. This implicates that it is possible to have a line of nodes in the pairing function. Contrarily, the T 2 dependence is plausible for the La 1.85 Sr 0.15 CuO 4 system, giving evidence of point nodes. We argue that a high- T c superconductivity requires a new explanation instead of the BCS theory.

Using exact formulae we prove that the weak field expansions of the thermodynamic properties of an electron gas in a uniform magnetic field at T = 0 K do not exist. This holds in both Schrodinger and Dirac theories and further for both non-interacting and interacting electron gases. We also derive a formula for the mean value of the total susceptibility 〈ξ t 〉 in the interval betweem two consecutive Landau levels.

Considering a nine-parameter lagrangian quadratic in torsion and curvature, we derive the general condition which must be satisfied by the parameters in order to obtain, in the weak field limit, a Yukawa-type correction to the static Newton potential. This condition is shown to be in general not incompatible with a different set of restrictions needed to avoid the presence of ghosts and tachyons.

The magnetic susceptibility of (SN)x was measured by the a.c. method. The Meissner effect occurs at 250 ± 3 mK. The real part of the susceptibility nearly saturates at 100 mK and reaches 93 ± 7% of − 1 4 π at 30 mK for weak field perpendicular to the polymer axis, while for the parallel direction it remains at 65 ± 10% of − 1 4 π . The susceptibility depends strongly on the a.c. magnetic field. There is a peak in the imaginary part of the susceptibility at the transition region to the superconducting state.

Within the framework of the angular overlap model the matrix elements of the linear Jahn-Teller operator may easily be calculated in the weak-field basis in terms of simple operator equivalents. The method is applied to the calculation of the 〈 M J |∂ V /∂ Q | M j 〉 matrix elements for the | LSJMj 〉 ground states of t x species ( x = 1) − 13) in ) * symmetry.