On meteor stream spatial structure theory

The classical spatial representation of meteor streams is an elliptical torus with variable cross section. The position of this torus in space is determined by the mean orbit elements that may be obtained directly from observations of individual meteor stream particles when crossed by the Earth. Since the orbits of individual particles of a stream differ from each other, the distance between them on a plane normal to the mean orbit of elliptical torus forms some area, i.e., a cross section. The size and form of these cross sections change with the change of the direction among the mean orbit and are completely defined by the dispersion values of the orbit elements in a stream. An attempt was made to create an analytical method that would permit description of the spatial and time parameters of meteor streams, i.e., the form and size of their cross section, density of incident flux and their variations along the mean orbit and in time. In this case, the stream is considered as a continuous flux rather than a set of individual particles

Full counting statistics of a charge pump in the Coulomb blockade regime

We study the full charge counting statistics of a charge pump based on a nearly open single electron transistor. The problem is mapped onto an exactly soluble problem of a g=1/2 non-equilibrium Luttinger liquid with an impurity. We obtain an analytic expression for the generating function of the transmitted charge for an arbitrary pumping strength. Even though this model contains fractionally charged excitations only integer transmitted charges can be observed during finite observation times.Comment: 4 pages, 1 figur

Andreev tunneling through a double quantum-dot system coupled to a ferromagnet and a superconductor: effects of mean field electronic correlations

We study the transport properties of a hybrid nanostructure composed of a ferromagnet, two quantum dots, and a superconductor connected in series. By using the non-equilibrium Green's function approach, we have calculated the electric current, the differential conductance and the transmittance for energies within the superconductor gap. In this regime, the mechanism of charge transmission is the Andreev reflection, which allows for a control of the current through the ferromagnet polarization. We have also included interdot and intradot interactions, and have analyzed their influence through a mean field approximation. In the presence of interactions, Coulomb blockade tend to localized the electrons at the double-dot system, leading to an asymmetric pattern for the density of states at the dots, and thus reducing the transmission probability through the device. In particular, for non-zero polarization, the intradot interaction splits the spin degeneracy, reducing the maximum value of the current due to different spin-up and spin-down densities of states. Negative differential conductance (NDC) appears for some regions of the voltage bias, as a result of the interplay of the Andreev scattering with electronic correlations. By applying a gate voltage at the dots, one can tune the effect, changing the voltage region where this novel phenomenon appears. This mechanism to control the current may be of importance in technological applications.Comment: 12 pages, 11 figure

Estimation of the particle-antiparticle correlation effect for pion production in heavy ion collisions

Estimation of the back-to-back pi-pi correlations arising due to evolution of the pionic field in the course of pion production process is given for central heavy nucleus collisions at moderate energies.Comment: 6 LaTeX pages + 5 ps figure

Two-photon correlations as a sign of sharp transition in quark-gluon plasma

The photon production arising due to time variation of the medium has been considered. The Hamilton formalism for photons in time-variable medium (plasma) has been developed with application to inclusive photon production. The results have been used for calculation of the photon production in the course of transition from quark-gluon phase to hadronic phase in relativistic heavy ion collisions. The relative strength of the effect as well as specific two- photon correlations have been evaluated. It has been demonstrated that the opposite side two-photon correlations are indicative of the sharp transition from the quark-gluon phase to hadrons.Comment: 23 pages, 2 figure

Nonlinear Hysteretic Torsional Waves

We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities, and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other type of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short term memory as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters

Triple-gap superconductivity of MgB2 - (La,Sr)MnO3 composite. Which of the gaps is proximity induced?

Interplay of superconductivity and magnetism in a composite prepared of the ferromagnetic half-metallic La_0.67Sr_0.33MnO (LSMO) nanoparticles and the conventional s-wave superconductor MgB_2 has been studied. A few principal effects have been found in bulk samples. With an onset of the MgB_2 superconductivity, a spectacular drop of the sample resistance has been detected and superconductivity has been observed at temperature up to 20K. Point-contact (PC) spectroscopy has been used to measure directly the superconducting energy coupling. For small voltage, an excess current and doubling of the PC's normal state conductance have been found. Conductance peaks corresponding to three energy gaps are clearly observed. Two of these gaps we identified as enhanced \Delta_{\pi} and \Delta_{\sigma} gaps originating from the MgB_2; the third gap \Delta_{tr} is more than three times larger than the largest MgB_2 gap. The experimental results provide unambiguous evidences for a new type of proximity effect which follows the phase coherency scenario of proximity induced superconductivity. Specifically, at low temperature, the p-wave spin-triplet condensate with pairing energy \Delta_{tr} is essentially sustained in LSMO but is incapable to display long-range supercurrent response because of a phase-disordering state. The proximity coupling to MgB_2 restores the long-range phase coherency of the triplet superconducting state, which, in turn, enhances superconducting state of the MgB_2.Comment: 10 pages, 6 figure