Properties of Accretion Shocks in Viscous Flows with Cooling Effects

Low angular momentum accretion flows can have standing and oscillating shock waves. We study the region of the parameter space in which multiple sonic points occur in viscous flows in presence of various cooling effects such as bremsstrahlung and Comptonization. We also quantify the parameter space in which shocks are steady or oscillating. We find that cooling induces effects opposite to heating by viscosity even in modifying the topology of the solutions, though one can never be exactly balanced by the other due to their dissimilar dependence on dynamic and thermodynamic parameters. We show that beyond a critical value of cooling, the flow ceases to contain a shock wave.Comment: 18 pages, 12 figures, Accepted for Publication in Int. J. Mod. Phys.

Ac Susceptibility and Static Magnetization Measurements of CeRu2_2Si2_2 at Small Magnetic Fields and Ultra Low Temperatures

The magnetic properties of CeRu$_2$Si$_2$ at microkelvin temperatures (down to 170 $\mu$K) and ultra small magnetic fields ($0.02\sim6.21$ mT) are investigated experimentally for the first time. The simultaneously measured ac susceptibility and static magnetization show neither evidence of the magnetic ordering, superconductivity down to the lowest temperatures nor conventional Landau Fermi-Liquid behavior. The results imply the magnetic transition temperature in undoped CeRu$_2$Si$_2$ is very close to absolute 0 K. The possibility for proximity of CeRu$_2$Si$_2$ to the quantum critical point without any doping is discussed.Comment: 4 pages, 3 figures; accepted for publication in Phys. Rev. B (Rapid Communication) and scheduled issue on 1st of May 200

On Witten multiple zeta-functions associated with semisimple Lie algebras IV

In our previous work, we established the theory of multi-variable Witten zeta-functions, which are called the zeta-functions of root systems. We have already considered the cases of types $A_2$, $A_3$, $B_2$, $B_3$ and $C_3$. In this paper, we consider the case of $G_2$-type. We define certain analogues of Bernoulli polynomials of $G_2$-type and study the generating functions of them to determine the coefficients of Witten's volume formulas of $G_2$-type. Next we consider the meromorphic continuation of the zeta-function of $G_2$-type and determine its possible singularities. Finally, by using our previous method, we give explicit functional relations for them which include Witten's volume formulas.Comment: 22 pag

Vortex Charging Effect in a Chiral px±ipyp_x\pm i p_y-Wave Superconductor

Quasiparticle states around a single vortex in a $p_x\pm i p_y$-wave superconductor are studied on the basis of the Bogoliubov-de Gennes (BdG) theory, where both charge and current screenings are taken into account. Due to the violation of time reversal symmetry, there are two types of vortices which are distinguished by their winding orientations relative to the angular momentum of the chiral Cooper pair. The BdG solution shows that the charges of the two types of vortices are quite different, reflecting the rotating Cooper pair of the $p_x\pm i p_y$-wave paring state.Comment: 10 pages, 5 figures, revtex, to be published in Phys. Rev.

Single-electron transistors with wide operating temperature range

Abstract : Single-electron transistors are fabricated with a planar self-aligned process using chemical mechanical polishing. The method is demonstrated with Ti∕TiOxTi∕TiOx junctions and resistless lithography. The device characterization showed Coulomb blockade up to 433K433K. High temperature data allowed one to calculate the impact of the process variations on the charging energy and thus on a realistic operating temperature. It is found that single electron devices can have an operating temperature range similar to conventional silicon transistors, opening the door to hybrid designs. These approaches are promising because advanced functionality is created by an optimal combination of both technology strengths