Current fluctuations in composite conductors: Beyond the second cumulant

Employing the non-linear $\sigma$-model we analyze current fluctuations in coherent composite conductors which contain a diffusive element in-between two tunnel barriers. For such systems we explicitly evaluate the frequency-dependent third current cumulant which also determines the leading Coulomb interaction correction to shot noise. Our predictions can be directly tested in future experiments.Comment: 6 pages, 1 figur

Andreev interferometer with three superconducting electrodes

We develop a quasiclassical theory of Andreev interferometers with three superconducting electrodes. Provided tunneling interface resistance between one superconducting electrode and the normal metal strongly exceeds two others, significant current sensitivity to the external magnetic flux is observed only at subgap voltages. If all barrier conductances are comparable, multiple Andreev reflection comes into play and substantial current modulation can be achieved in both subgap and overgap voltage regimes. Our analysis reveals a large variety of interesting features which can be used for performance optimization of Andreev interferometers.Comment: 9 pages, 13 figure

Five types of blow-up in a semilinear fourth-order reaction-diffusion equation: an analytic-numerical approach

Five types of blow-up patterns that can occur for the 4th-order semilinear parabolic equation of reaction-diffusion type u_t= -\Delta^2 u + |u|^{p-1} u \quad {in} \quad \ren \times (0,T), p>1, \quad \lim_{t \to T^-}\sup_{x \in \ren} |u(x,t)|= +\iy, are discussed. For the semilinear heat equation $u_t= \Delta u+ u^p$, various blow-up patterns were under scrutiny since 1980s, while the case of higher-order diffusion was studied much less, regardless a wide range of its application.Comment: 41 pages, 27 figure

Diffusion and ballistic contributions of the interaction correction to the conductivity of a two-dimensional electron gas

The results of an experimental study of interaction quantum correction to the conductivity of two-dimensional electron gas in A$_3$B$_5$ semiconductor quantum well heterostructures are presented for a wide range of $T\tau$-parameter ($T\tau\simeq 0.03-0.8$), where $\tau$ is the transport relaxation time. A comprehensive analysis of the magnetic field and temperature dependences of the resistivity and the conductivity tensor components allows us to separate the ballistic and diffusion parts of the correction. It is shown that the ballistic part renormalizes in the main the electron mobility, whereas the diffusion part contributes to the diagonal and does not to the off-diagonal component of the conductivity tensor. We have experimentally found the values of the Fermi-liquid parameters describing the electron-electron contribution to the transport coefficients, which are found in a good agreement with the theoretical results.Comment: 11 pages, 11 figure

Overscreening Diamagnetism in Cylindrical Superconductor-Normal Metal-Heterostructures

We study the linear diamagnetic response of a superconducting cylinder coated by a normal-metal layer due to the proximity effect using the clean limit quasiclassical Eilenberger equations. We compare the results for the susceptibility with those for a planar geometry. Interestingly, for $R\sim d$ the cylinder exhibits a stronger overscreening of the magnetic field, i.e., at the interface to the superconductor it can be less than (-1/2) of the applied field. Even for $R\gg d$, the diamagnetism can be increased as compared to the planar case, viz. the magnetic susceptibility $4\pi\chi$ becomes smaller than -3/4. This behaviour can be explained by an intriguing spatial oscillation of the magnetic field in the normal layer

Сравнительная оценка двух способов определения нестационарных аэродинамических характеристик цилиндрических моделей отделяемых частей ракет-носителей космического назначени

Ecology and security clearance of cargo into Earth orbit space considered in unsteadyaerodynamics of the separated parts of of launch vehicles for space applications, which directly involves the definition of the shape and size of fields separated by falling parts, fragmentation issues and software problems aeroballistic reusable space systems (such as "Baikal" (Russian Federation), Falcon - Task 1 (USA) and others.).To resolve the methodological issues determining the value of the aerodynamic damping (and / or anti-damping) separable parts as the object of study was chosen cylindrical model as a bluff body for which there are no systematic dependence of unsteady aerodynamic coefficients pitch moment of defining the parameters of the problem (the Mach number, angle of attack, Reynolds number, etc.).The value of the derivative of pitching moment coefficient of the angular velocitydetermined numerically for the most intense stress of supersonic flight mode as the method of curved bodies, and direct numerical simulation of unsteady motion of the body in the air flow within the full Navier-Stokes equations.Comparison of these two approaches implemented as a tool for scientific research in theform of a software package FineOpen (products of the Company Numeca) and programs for solving the Navier-Stokes equations (the author's version) helped establish the limits of applicability of the curved bodies in the implementation of the marked change in the form of slots defining parameters of the problem.В интересах успешного разрешения проблемы сокращения полей падения отработавших ступеней ракет-носителей космического (РКН) назначения рассмотрены вопросы определения их нестационарных аэродинамических характеристик, с использованием возможностей вычислительной аэрогазодинамики (ВАГД - CFD). Отработавшие ступени РКН схематизированы в виде цилиндрических моделей сравнительно большого удлинения, что позволило рассмотреть возможность использования методов прямого численного моделирования нестационарного обтекания в рамках полных уравнений Навье-Стокса и метода искривленных тел для определения аэродинамических коэффициентов демпфирования отмеченного объекта исследования преимущественно для сверхзвуковых режимов. В качестве научного инструмента исследования были выбраны два способа использования математических моделей высокого уровня для аэродинамического расчета (программ для аэродинамического расчета, разработанных авторами и пакета программ FineOpen (фирма Numeca)). Достоверность подтверждена сравнением с известными теоретическими и экспериментальными зависимостями

Accelerator Testing of the General Antiparticle Spectrometer, a Novel Approach to Indirect Dark Matter Detection

We report on recent accelerator testing of a prototype general antiparticle spectrometer (GAPS). GAPS is a novel approach for indirect dark matter searches that exploits the antideuterons produced in neutralino-neutralino annihilations. GAPS captures these antideuterons into a target with the subsequent formation of exotic atoms. These exotic atoms decay with the emission of X-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. This signature uniquely characterizes the antideuterons. Preliminary analysis of data from a prototype GAPS in an antiproton beam at the KEK accelerator in Japan has confirmed the multi-X-ray/pion star topology and indicated X-ray yields consistent with prior expectations. Moreover our success in utilizing solid rather than gas targets represents a significant simplification over our original approach and offers potential gains in sensitivity through reduced dead mass in the target area.Comment: 18 pages, 9 figures, submitted to JCA

Microscopic nonequilibrium theory of double-barrier Josephson junctions

We study nonequilibrium charge transport in a double-barrier Josephson junction, including nonstationary phenomena, using the time-dependent quasiclassical Keldysh Green's function formalism. We supplement the kinetic equations by appropriate time-dependent boundary conditions and solve the time-dependent problem in a number of regimes. From the solutions, current-voltage characteristics are derived. It is understood why the quasiparticle current can show excess current as well as deficit current and how the subgap conductance behaves as function of junction parameters. A time-dependent nonequilibrium contribution to the distribution function is found to cause a non-zero averaged supercurrent even in the presence of an applied voltage. Energy relaxation due to inelastic scattering in the interlayer has a prominent role in determining the transport properties of double-barrier junctions. Actual inelastic scattering parameters are derived from experiments. It is shown as an application of the microscopic model, how the nature of the intrinsic shunt in double-barrier junctions can be explained in terms of energy relaxation and the opening of Andreev channels.Comment: Accepted for Phys. Rev.