Studying Diquark Structure of Heavy Baryons in Relativistic Heavy Ion Collisions

We propose the enhancement of $\Lambda_c$ yield in heavy ion collisions at RHIC and LHC as a novel signal for the existence of diquarks in the strongly coupled quark-gluon plasma produced in these collisions as well as in the $\Lambda_c$. Assuming that stable bound diquarks can exist in the quark-gluon plasma, we argue that the yield of $\Lambda_c$ would be increased by two-body collisions between $ud$ diquarks and $c$ quarks, in addition to normal three-body collisions among $u$, $d$ and $c$ quarks. A quantitative study of this effect based on the coalescence model shows that including the contribution of diquarks to $\Lambda_c$ production indeed leads to a substantial enhancement of the $\Lambda_c/D$ ratio in heavy ion collisions.Comment: Prepared for Chiral Symmetry in Hadron and Nuclear Physics (Chiral07), Nov. 13-16, 2007, Osaka, Japa

Laser frequency combs and ultracold neutrons to probe braneworlds through induced matter swapping between branes

This paper investigates a new experimental framework to test the braneworld hypothesis. Recent theoretical results have shown the possibility of matter exchange between branes under the influence of suitable magnetic vector potentials. It is shown that the required conditions might be achieved with present-day technology. The experiment uses a source of pulsed and coherent electromagnetic radiation and relies on the Hansch frequency comb technique well-known in ultrahigh-precision spectroscopy. A good matter candidate for testing the hypothesis is a polarized ultracold neutron gas for which the number of swapped neutrons is measured.Comment: 14 pages, 4 figures. Published version. Published in Phys. Rev.

Local metrics admitting a principal Killing-Yano tensor with torsion

In this paper we initiate a classification of local metrics admitting the principal Killing--Yano tensor with a skew-symmetric torsion. It is demonstrated that in such spacetimes rank-2 Killing tensors occur naturally and mutually commute. We reduce the classification problem to that of solving a set of partial differential equations, and we present some solutions to these PDEs. In even dimensions, three types of local metrics are obtained: one of them naturally generalizes the torsionless case while the others occur only when the torsion is present. In odd dimensions, we obtain more varieties of local metrics. The explicit metrics constructed in this paper are not the most general possible admitting the required symmetry, nevertheless, it is demonstrated that they cover a wide variety of solutions of various supergravities, such as the Kerr-Sen black holes of (un-)gauged abelian heterotic supergravity, the Chong-Cvetic-L\"u-Pope black hole solution of five-dimensional minimal supergravity, or the K\"ahler with torsion manifolds. The relation between generalized Killing--Yano tensors and various torsion Killing spinors is also discussed.Comment: 36pages, no figure

Thermoelastic analysis of solar cell arrays and their material properties

Announced report discusses experimental test program in which five different solar cell array designs were evaluated by subjecting them to 60 thermal cycles from minus 190 deg to 0.0 deg. Results indicate that solder-coated cells combined with Kovar n-interconnectors and p-interconnectors are more durable under thermal loading than other configurations

Non-Abelian statistics of vortices with non-Abelian Dirac fermions

We extend our previous analysis on the exchange statistics of vortices having a single Dirac fermion trapped in each core, to the case where vortices trap two Dirac fermions with U(2) symmetry. Such a system of vortices with non-Abelian Dirac fermions appears in color superconductors at extremely high densities, and in supersymmetric QCD. We show that the exchange of two vortices having doublet Dirac fermions in each core is expressed by non-Abelian representations of a braid group, which is explicitly verified in the matrix representation of the exchange operators when the number of vortices is up to four. We find that the result contains the matrices previously obtained for the vortices with a single Dirac fermion in each core as a special case. The whole braid group does not immediately imply non-Abelian statistics of identical particles because it also contains exchanges between vortices with different numbers of Dirac fermions. However, we find that it does contain, as its subgroup, a genuine non-Abelian statistics for the exchange of the identical particles, that is, vortices with the same number of Dirac fermions. This result is surprising compared with conventional understanding because all Dirac fermions are defined locally at each vortex, unlike the case of Majorana fermions for which Dirac fermions are defined non-locally by Majorana fermions located at two spatially separated vortices.Comment: 32 pages, no figures, v3: published versio

Development of Atmospheric Monitoring System at Akeno Observatory for the Telescope Array Project

We have developed an atmospheric monitoring system for the Telescope Array experiment at Akeno Observatory. It consists of a Nd:YAG laser with an alt-azimuth shooting system and a small light receiver. This system is installed inside an air conditioned weather-proof dome. All parts, including the dome, laser, shooter, receiver, and optical devices are fully controlled by a personal computer utilizing the Linux operating system. It is now operated as a back-scattering LIDAR System. For the Telescope Array experiment, to estimate energy reliably and to obtain the correct shower development profile, the light transmittance in the atmosphere needs to be calibrated with high accuracy. Based on observational results using this monitoring system, we consider this LIDAR to be a very powerful technique for Telescope Array experiments. The details of this system and its atmospheric monitoring technique will be discussed.Comment: 24 pages, 13 figures(plus 3 gif files), Published in NIM-A Vol.488, August 200

Vacuum solutions of five dimensional Einstein equations generated by inverse scattering method

We study stationary and axially symmetric two solitonic solutions of five dimensional vacuum Einstein equations by using the inverse scattering method developed by Belinski and Zakharov. In this generation of the solutions, we use five dimensional Minkowski spacetime as a seed. It is shown that if we restrict ourselves to the case of one angular momentum component, the generated solution coincides with a black ring solution with a rotating two sphere which was found by Mishima and Iguchi recently.Comment: 10 pages, accepted for publication in Physical Review

Studies of the Anomalous Hall Effect and Magnetic Structure of Nd2Mo2O7 -Test of the Chirality Mechanism-

Neutron scattering studies have been carried out under the magnetic fields H//[0_11] and H//[001] on a single crystal of Nd2Mo2O7, whose Hall resistivity(rhoH) exhibits quite unusual H- and temperature(T)-dependences. Material parameters such as the single ion anisotropies of the Mo- and Nd- moments and exchange coupling constants among the Mo-Mo, Mo-Nd and Nd-Nd moments, have been determined to reproduce various kinds of experimental data taken as a function of H and T. For example, the neutron Bragg intensities, magnetization curves and the magnetic specific heats have been reproduced by the common parameters. By using the magnetic structure reproduced by these parameters, the spin chirality (chi) of Mo spins or the fictitious magnetic flux Phi proportional to chi has been calculated as a function of H and T by using equation chi=, where the bracket means the statistical average. (Note that we do not use the equation chi=x, because the local nature of the chirality should be correctly considered.) Comparing the calculated results with the observed rhoH, we can conclude that the unusual behavior of rH cannot be understood consistently only by the chirality mechanism.Comment: 16 pages, 12 fiures, submitted to J. Phys. Soc. Jp