Bose-Einstein Condensation and Casimir Effect of Trapped Ideal Bose Gas in between two Slabs

We study the Bose-Einstein condensation for a 3-d system of ideal Bose gas which is harmonically trapped along two perpendicular directions and is confined in between two slabs along the other perpendicular direction. We calculate the Casimir force between the two slabs for this system of trapped Bose gas. At finite temperatures this force for thermalized photons in between two plates has a classical expression which is independent of $\hbar$. At finite temperatures the Casimir force for our system depends on $\hbar$. For the calculation of Casimir force we consider only the Dirichlet boundary condition. We show that below condensation temperature($T_c$) the Casimir force for this non-interacting system decreases with temperature($T$) and at $T\gtrsim T_c$, it is independent of temperature. We also discuss the Casimir effect on 3-d highly anisotropic harmonically trapped ideal Bose gas.Comment: 4 page

Stabilization of magnetic polarons in antiferromagnetic semiconductors by extended spin distortions

We study the problem of a magnetic polaron in an antiferromagnetic semiconductor (ferron). We obtain an analytical solution for the distortion produced in the magnetic structure of the d-spins due to the presence of a charge carrier bound to an impurity. The region in which the charge carrier is trapped is of the order of the lattice constant (small ferron) but the distortion of the magnetic structure extends over much larger distance. It is shown that the presence of this distortion makes the ferron more stable, and introduces a new length scale in the problem.Comment: 5 pages, 1 figure, RevTex 4, submitted to PRB; v2: one reference added, minor changes in the experiment discussion; v3: minor changes in tex

On tests of local realism by CP-violation parameters of K^0 mesons

Recently various papers have proposed to test local realism (LR) by considering electroweak CP-violation parameters values in neutral pseudoscalar meson systems. Considering the large interest for a conclusive test of LR and the experimental accessibility to these tests, in this paper we critically consider these results showing how they, albeit very interesting, require anyway additional assumptions and therefore cannot be considered conclusive tests of LR

Photoproduction of \eta mesons on protons in the resonance region:The background problem and the third S_11 resonance

We have constructed an isobar model for the $\eta$-photoproduction on the proton in the energy region up to the photon lab energy $K_0 = 3$ GeV. The data base involved into the fitting procedure includes precise results for the cross section and for the $T$-asymmetry of the process $\gamma p\to\eta p$ near threshold obtained at MAMI and ELSA as well as recent results for the $\Sigma$-asymmetry and for the angular distribution measured at higher energies in Grenoble and also more recent measurements performed at JLab for the photon energies up to 2 GeV. The model includes twelve nucleon resonances: $S_{11}(1535)$, $S_{11}(1650)$, $S_{11}(1825)$, $P_{11}(1440)$,$P_{13}(1720)$, $D_{13}(1520)$, $D_ {15}(1675)$, $F_{15}(1680)$, $F_{17}(1990)$,$G_{17}(2190)$, $G_{19} (2250)$, $H_{19}(2220)$, and the background consisting of the nucleon pole term and the vector meson exchange in the $t$-channel. To explain the observed energy dependence of the integrated cross section, two $s$ -wave resonances, $S_{11}(1650)$ and $S_{11}(1825)$, have to be taken into account along with the dominating $S_{11}(1535)$. The integrated cross section as well as the angular distribution and $\Sigma$ asymmetry predicted by the model are in good agreement with the data. Above the photon energy $K_0 = 2$ GeV, the calculated cross section exhibits an appreciable dependence on the $\rho$- and $\omega$-meson contribution, whose coupling with nucleons is not well defined. Several versions of extending the model to higher energies are considered.Comment: 7 pages, 8 figures, 2 tables, version to appear in Eur.Phys.J.A 22 (2004

Flavor changing neutral currents from lepton and B decays in the two Higgs doublet model

Constraints on the whole spectrum of lepton flavor violating vertices are shown in the context of the standard two Higgs doublet model. The vertex involving the $e-\tau$ mixing is much more constrained than the others, and the decays proportional to such vertex are usually very supressed. On the other hand, bounds on the quark sector are obtained from leptonic decays of the $B_{d,s}^{0}$ mesons and from $\Delta M_{B_{d}^{0}}$. We emphasize that although the $B_{d}^{0}-\bar{B}_{d}^{0}$ mixing restricts severely the $$ mixing vertex, the upper bound for this vertex could still give a sizeable contribution to the decay $B_{d}^{0}\to \mu \bar{\mu}$ respect to the standard model contribution, from which we see that such vertex could still play a role in the phenomenology.Comment: 9 pages, 2 figures, LaTeX2e. Minor typos corrected. References added and corrected. Introduction change

Las islas Galápagos, Un viaje a través del espacio y el tiempo

Para hacer este maravilloso viaje, me equipé con todo lo que nos recomendó la persona encargada de la logística, pero, además, hice algo relativamente parecido a lo que hizo Darwin cuando se embarcó en el Beagle: así como él llevó algunos libros de científicos que le ayudarían a comprender sus observaciones (en especial llevó consigo un texto de Lyell y otro de Humboldt), del mismo modo yo viajé acompañado por su libro “El viaje del Beagle”. En lo que sigue, voy a describir algunas de las fotos que tomé en el archipiélago por medio de lo que dijo Darwin en 1835, año en el que lo visitó. Creo que no puede haber mejores descripciones que las que él hizo . Antes de entrar en materia, permítanme citar un texto muy diciente de Eduardo Galeano, el cual nos remonta al año en cuestión. Ah, se me olvidaba: digo que este viaje fue a través del espacio y del tiempo porque, de hecho, las islas se encuentran a cerca de 1000 Km de la costa ecuatoriana, y porque viajar a ese sitio en compañía del libro que he citado, es una manera de devolverse en el tiempo

Message from the President of the United States, transmitting, in compliance with a Senate resolution of July 7, 1876, information in relation to the hostile demonstrations of the Sioux Indians, and the disaster to the forces under General Custer

44-1Message on a Hostile Demonstration by the Sioux Indians. [1664] First news of the disaster regarding Gen. Custer's forces; observance of the treaty of 1868 by nearly all Sioux, save Sitting Bull's band.1876-13

SANTRAUKOS

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Sisseton and Wahpeton Bands of Sioux Indians.

51-1Indian AffairsChicago, Milwaukee. and St. Paul Railway Co. [2807] Railway has been constructed through the Lake Traverse reservation of the Sisseton and Wahpeton Sioux. but agreement on this has not been ratified yet.1890-5