Induced Kramer-Pesch-Effect in a Two Gap Superconductor: Application to MgB2

The size of the vortex core in a clean superconductor is strongly temperature dependent and shrinks with decreasing temperature, decreasing to zero for T -> 0. We study this so-called Kramer-Pesch effect both for a single gap superconductor and for the case of a two gap superconductor using parameters appropriate for Magnesium Diboride. Usually, the Kramer-Pesch effect is absent in the dirty limit. Here, we show that the Kramer-Pesch effect exists in both bands of a two gap superconductor even if only one of the two bands is in the clean limit and the other band in the dirty limit, a case appropriate for MgB2. In this case an induced Kramer-Pesch effect appears in the dirty band. Besides numerical results we also present an analytical model for the spatial variation of the pairing potential in the vicinity of the vortex center that allows a simple calculation of the vortex core radius even in the limit T -> 0.Comment: 12 pages, 12 figure

A List of the Species of Polyamia (Homoptera: Cicadellidae) Known to Occur in Mexico, with Descriptions of New Species

Author Institution: Department of Entomology, The Ohio State UniversitySeventeen species of Polyamia are treated, 16 of which are known to occur in Mexico. Seven previously described species, P. arachnion Kramer, P. gangamon Kramer, P. tolteca Kramer, P. delongi (Kramer), P. reticulata (Linnavuori), P. satur (Ball), and P. incerta Bcamer and Tuthill are listed and illustrated. Ten species, P. duella n. sp., P. acura n. sp., P. dualis n. sp., P. bradshawi n. sp., P. scina n. sp., P. randa n. sp., P. frustrara n. sp., P. triplehorni n. sp., P. nidula n. sp. and P. tulara n. sp. are described as new

Impurity Effect on Kramer-Pesch Core Shrinkage in s-Wave Vortex and Chiral p-Wave Vortex

The low-temperature shrinking of the vortex core (Kramer-Pesch effect) is studied for an isolated single vortex for chiral p-wave and s-wave superconducting phases. The effect of nonmagnetic impurities on the vortex core radius is numerically investigated in the Born limit by means of a quasiclassical approach. It is shown that in the chiral p-wave phase the Kramer-Pesch effect displays a certain robustness against impurities owing to a specific quantum effect, while the s-wave phase reacts more sensitively to impurity scattering. This suggests chiral p-wave superconductors as promising candidates for the experimental observation of the Kramer-Pesch effect.Comment: 18 pages, 4 figures; to be published in J. Low Temp. Phys.; Proc. of NATO ARW: VORTEX 2004, Yalta (Uknaine

Matrix Ernst potentials for EMDA with multiple vector fields

We show that the Einstein-Maxwell-Dilaton-Axion system with multiple vector fields (bosonic sector of the D=4, N=4 supergravity) restricted to spacetimes possessing a non-null Killing vector field admits a concise representation in terms of the Ernst-type matrix valued potentials. A constructive derivation of the SWIP solutions is given and a colliding waves counterpart of the DARN-NUT solution is obtained. SU(m,m) chiral representation of the two-dimensionally reduced system is derived and the corresponding Kramer-Neugebauer-type map is presented.Comment: Latex file, no figure

Geodetic Precession and the Binary Pulsar B1913+16

A change of the component separation in the profiles of the binary pulsar PSR B1913+16 has been observed for the first time (Kramer 1998) as expected by geodetic precession. In this work we extend the previous work by accounting for recent data from the Effelsberg 100-m telescope and Arecibo Observatory and testing model predictions. We demonstrate how the new information will provide additional information on the solutions of the system geometry.Comment: 2 pages, 1 figure, IAU 177 Colloquium: Pulsar Astronomy - 2000 and Beyon

Stationary Axisymmetric Black Holes, N=2N=2 Superstring, and Self-Dual Gauge or Gravity Fields

We present interesting relationship between what are called stationary axisymmetric black hole solutions for the vacuum Einstein equations in the ordinary four-dimensions and exact solutions for self-dual Yang-Mills fields in flat $2+2$ dimensions which are nothing but the consistent backgrounds for $~N=2$~ open superstring. We show that any stationary axisymmetric black hole solution for the former automatically provides an exact solution for the latter. We also give a nice relation between the physical parameters of black holes and an invariant integral analogous to instanton charges for such a self-dual Yang-Mills solution. This result indicates that any general black hole solution in the usual four-dimensions can be the background of $~N=2$~ superstring at the same time. We also give an interesting embedding of stationary axisymmetric solutions into the background of $~N=2$~ closed superstring. Finally we show some indication that the Kerr solution with naked singularity (for $a > m$) is nothing else than the gravitational field generated by a closed string.Comment: 15 page