Self-Interacting Electromagnetic Fields and a Classical Discussion on the Stability of the Electric Charge

The present work proposes a discussion on the self-energy of charged particles in the framework of nonlinear electrodynamics. We seek magnet- ically stable solutions generated by purely electric charges whose electric and magnetic fields are computed as solutions to the Born-Infeld equa- tions. The approach yields rich internal structures that can be described in terms of the physical fields with explicit analytic solutions. This suggests that the anomalous field probably originates from a magnetic excitation in the vacuum due to the presence of the very intense electric field. In addition, the magnetic contribution has been found to exert a negative pressure on the charge. This, in turn, balances the electric repulsion, in such a way that the self-interaction of the field appears as a simple and natural classical mechanism that is able to account for the stability of the electron charge.Comment: 8 pages, 1 figur

Spontaneous Generation of Photons in Transmission of Quantum Fields in PT Symmetric Optical Systems

We develop a rigorous mathematically consistent description of PT symmetric optical systems by using second quantization. We demonstrate the possibility of significant spontaneous generation of photons in PT symmetric systems. Further we show the emergence of Hanbury-Brown Twiss (HBT) correlations in spontaneous generation. We show that the spontaneous generation determines decisively the nonclassical nature of fields in PT symmetric systems. Our work can be applied to other systems like plasmonic structure where losses are compensated by gain mechanisms.Comment: 4 pages, 5 figure

Nefazodone in psychotic unipolar and bipolar depression: A retrospective chart analysis and open prospective study on its efficacy and safety versus combined treatment with amitriptyline and haloperidol

Although atypical antipsychotics are on the rise, traditional treatment of psychotic (or delusional) depression mostly includes the addition of classical antipsychotics to antidepressants. As there are only few data supporting this approach compared with antidepressant monotherapy, and almost no data comparing it with antidepressants of the latest generation, we conducted a retrospective chart analysis and a prospective, randomized open study on the efficacy and tolerability of nefazodone monotherapy versus combined treatment with amitriptyline and haloperidol in psychotic depression. The results suggest that the addition of classical antipsychotics should be reserved for those with very severe psychotic symptoms, but may not be needed in milder forms. Copyright (c) 2003 S. Karger AG, Basel

Transient behavior of surface plasmon polaritons scattered at a subwavelength groove

We present a numerical study and analytical model of the optical near-field diffracted in the vicinity of subwavelength grooves milled in silver surfaces. The Green's tensor approach permits computation of the phase and amplitude dependence of the diffracted wave as a function of the groove geometry. It is shown that the field diffracted along the interface by the groove is equivalent to replacing the groove by an oscillating dipolar line source. An analytic expression is derived from the Green's function formalism, that reproduces well the asymptotic surface plasmon polariton (SPP) wave as well as the transient surface wave in the near-zone close to the groove. The agreement between this model and the full simulation is very good, showing that the transient "near-zone" regime does not depend on the precise shape of the groove. Finally, it is shown that a composite diffractive evanescent wave model that includes the asymptotic SPP can describe the wavelength evolution in this transient near-zone. Such a semi-analytical model may be useful for the design and optimization of more elaborate photonic circuits whose behavior in large part will be controlled by surface waves.Comment: 12 pages, 10 figure

Superconductivity in Boron under pressure - why are the measured Tc_c's so low?

Using the full potential linear muffin-tin orbitals (FP-LMTO) method we examine the pressure-dependence of superconductivity in the two metallic phases of Boron: bct and fcc. Linear response calculations are carried out to examine the phonon frequencies and electron-phonon coupling for various lattice parameters, and superconducting transition temperatures are obtained from the Eliashberg equation. In both bct and fcc phases the superconducting transition temperature T$_c$ is found to decrease with increasing pressure, due to stiffening of phonons with an accompanying decrease in electron-phonon coupling. This is in contrast to a recent report, where T$_c$ is found to increase with pressure. Even more drastic is the difference between the measured T$_c$, in the range 4-11 K, and the calculated values for both bct and fcc phases, in the range 60-100 K. The calculation reveals that the transition from the fcc to bct phase, as a result of increasing volume or decreasing pressure, is caused by the softening of the X-point transverse phonons. This phonon softening also causes large electron-phonon coupling for high volumes in the fcc phase, resulting in coupling constants in excess of 2.5 and T$_c$ nearing 100 K. We discuss possible causes as to why the experiment might have revealed T$_c$'s much lower than what is suggested by the present study. The main assertion of this paper is that the possibility of high T$_c$, in excess of 50 K, in high pressure pure metallic phases of boron cannot be ruled out, thus substantiating the need for further experimental investigations of the superconducting properties of high pressure pure phases of boron.Comment: 16 pages, 8 figures, 1 Tabl

Interaction-Free All-Optical Switching via Quantum-Zeno Effect

We propose a novel interaction-free scheme for all-optical switching which does not rely on the physical coupling between signal and control waves. The interaction-free nature of the scheme allows it to overcome the fundamental photon-loss limit imposed by the signal-pump coupling. The same phenomenon protects photonic-signal states from decoherence, making devices based on this scheme suitable for quantum applications. Focusing on $\chi^{(2)}$ waveguides, we provide device designs for traveling-wave and Fabry-Perot switches. In both designs, the performance is optimal when the signal switching is induced by coherent dynamical evolution. In contrast, when the switching is induced by a rapid dissipation channel, it is less efficient.Comment: 14 pages, 14 figures, submitted to Physical Review

Lattice dynamics of anharmonic solids from first principles

An accurate and easily extendable method to deal with lattice dynamics of solids is offered. It is based on first-principles molecular dynamics simulations and provides a consistent way to extract the best possible harmonic - or higher order - potential energy surface at finite temperatures. It is designed to work even for strongly anharmonic systems where the traditional quasiharmonic approximation fails. The accuracy and convergence of the method are controlled in a straightforward way. Excellent agreement of the calculated phonon dispersion relations at finite temperature with experimental results for bcc Li and bcc Zr is demonstrated

Rotating charged Black Holes in Einstein-Born-Infeld theories and their ADM mass

In this work, the solution of the Einstein equations for a slowly rotating black hole with Born-Infeld charge is obtained. Geometrical properties and horizons of this solution are analyzed. The conditions when the ADM mass (as in the nonlinear static cases) and the ADM angular momentum of the system have been modified by the non linear electromagnetic field of the black hole, are considered.Comment: Final version and figures in journal. References and comments adde

Phase modulation induced by cooperative effects in electromagnetically induced transparency

We analyze the influence of dipole-dipole interactions in an electromagnetically induced transparency setup at high density. We show both analytically and numerically that the polarization contribution to the local field strongly modulates the phase of a weak pulse. We give an intuitive explanation for this local field induced phase modulation and show that it distinctively differs from the nonlinear self-phase modulation a strong pulse experiences in a Kerr medium

Strain and order-parameter coupling in Ni-Mn-Ga Heusler alloys from resonant ultrasound spectroscopy

Resonant ultrasound spectroscopy and magnetic susceptibility experiments have been used to characterize strain coupling phenomena associated with structural and magnetic properties of the shape-memory Heusler alloy series Ni$_{50+x}$Mn$_{25-x}$Ga$_{25}$ ($x=0$, 2.5, 5.0, and 7.5). All samples exhibit a martensitic transformation at temperature $T_M$ and ferromagnetic ordering at temperature $T_C$, while the pure end member ($x=0$) also has a premartensitic transition at $T_{PM}$, giving four different scenarios: $T_C>T_{PM}>T_M$, $T_C>T_M$ without premartensitic transition, $T_C\approx T_M$, and $T_C<T_M$. Fundamental differences in elastic properties i.e., stiffening versus softening, are explained in terms of coupling of shear strains with three discrete order parameters relating to magnetic ordering, a soft mode and the electronic instability responsible for the large strains typical of martensitic transitions. Linear-quadratic or biquadratic coupling between these order parameters, either directly or indirectly via the common strains, is then used to explain the stabilities of the different structures. Acoustic losses are attributed to critical slowing down at the premartensite transition, to the mobility of interphases between coexisting phases at the martensitic transition and to mobility of some aspect of the twin walls under applied stress down to the lowest temperatures at which measurements were made.Comment: 9 pages, 5 figure