Generating Black Strings in Higher Dimensions

Starting with a Zipoy-Voorhees line element we construct and study the three parameter family of solutions describing a deformed black string with arbitrary tension.Comment: 11 pages, 2 figures, accepted for publication in J. Mod. Phys. Lett.

Eviction of a 125 GeV "heavy"-Higgs from the MSSM

We prove that the present experimental constraints are already enough to rule out the possibility of the ~125 GeV Higgs found at LHC being the second lightest Higgs in a general MSSM context, even with explicit CP violation in the Higgs potential. Contrary to previous studies, we are able to eliminate this possibility analytically, using simple expressions for a relatively small number of observables. We show that the present LHC constraints on the diphoton signal strength, tau-tau production through Higgs and BR(B -> X_s gamma) are enough to preclude the possibility of H_2 being the observed Higgs with m_H~125 GeV within an MSSM context, without leaving room for finely tuned cancellations. As a by-product, we also comment on the difficulties of an MSSM interpretation of the excess in the gamma-gamma production cross section recently found at CMS that could correspond to a second Higgs resonance at m_H~136 GeV.Comment: 38 pages, 9 figures. Final version accepted at JHEP. Sections 2, 3 and appendices simplified. Experimental results updated, several references added. Small typos corrected and a new comparison of approximate formulas with full expressions include

Entanglement of formation for a class of (2⊗d)(2\otimes d)-dimensional systems

Currently the entanglement of formation can be calculated analytically for mixed states in a $(2\otimes2)$-dimensional Hilbert space. For states in higher dimensional Hilbert space a closed formula for quantifying entanglement does not exist. In this regard only entanglement bounds has been found for estimating it. In this work, we find an analytical expression for evaluating the entanglement of formation for bipartite ($2\otimes d$)-dimensional mixed states.Comment: 5 pages, 4 figures. Submitted for publicatio

Toward Supergravity Spectral Action

A spectral action of Euclidean supergravity is proposed. We calculate up to $a_4$, the Seeley-Dewitt coefficients in the expansion of the spectral action associated to the supergravity Dirac operator. This is possible because in simple supergravity, as in pure gravity, a well defined and mathematically consistent Dirac operator can be constructed.Comment: 10pages, no figures, matches published versio

The VIMOS VLT Deep Survey. The different assembly history of passive and star-forming L_B >= L*_B galaxies in the group environment at z < 1

We use the VIMOS VLT Deep Survey to study the close environment of galaxies in groups at 0.2 = L*_B galaxies (Me_B = M_B + 1.1z <= -20) are identified with Me_B <= -18.25 and within a relative distance 5h^-1 kpc <= rp <= 100h^-1 kpc and relative velocity Delta v <= 500 km/s . The richness N of a group is defined as the number of Me_B <= -18.25 galaxies belonging to that group. We split our principal sample into red, passive galaxies with NUV - r >= 4.25 and blue, star-forming galaxies with NUV - r < 4.25. We find that blue galaxies with a close companion are primarily located in poor groups, while the red ones are in rich groups. The number of close neighbours per red galaxy increases with N, with n_red being proportional to 0.11N, while that of blue galaxies does not depend on N and is roughly constant. In addition, these trends are found to be independent of redshift, and only the average n_blue evolves, decreasing with cosmic time. Our results support the following assembly history of L_B >= L*_B galaxies in the group environment: red, massive galaxies were formed in or accreted by the dark matter halo of the group at early times (z >= 1), therefore their number of neighbours provides a fossil record of the stellar mass assembly of groups, traced by their richness N. On the other hand, blue, less massive galaxies have recently been accreted by the group potential and are still in their parent dark matter halo, having the same number of neighbours irrespective of N. As time goes by, these blue galaxies settle in the group potential and turn red and/or fainter, thus becoming satellite galaxies in the group. With a toy quenching model, we estimate an infall rate of field galaxies into the group environment of R_infall = 0.9 - 1.5 x 10^-4 Mpc^-3 Gyr^-1 at z ~ 0.7.Comment: Astronomy and Astrophysics, in press. 11 pages, 11 figures, 4 tables. Minor changes with respect to the first versio

Josephson current in strongly correlated double quantum dots

We study the transport properties of a serial double quantum dot (DQD) coupled to two superconducting leads, focusing on the Josephson current through the DQD and the associated 0-$\pi$ transitions which result from the subtle interplay between the superconductivity, the Kondo physics, and the inter-dot superexchange interaction. We examine the competition between the superconductivity and the Kondo physics by tuning the relative strength $\Delta/T_K$ of the superconducting gap $\Delta$ and the Kondo temperature $T_K$, for different strengths of the superexchange coupling determined by the interdot tunneling $t$ relative to the dot level broadening $\Gamma$. We find strong renormalization of $t$, a significant role of the superexchange coupling $J$, and a rich phase diagram of the 0 and $\pi$-junction regimes. In particular, when both the superconductivity and the exchange interaction are in close competion with the Kondo physics ($\Delta\sim J\sim T_K$), there appears an island of $\pi'$-phase at large values of the superconducting phase difference.Comment: 4 pages, 4 figure

Magnetic Surfaces in Stationary Axisymmetric General Relativity

In this paper a new method is derived for constructing electromagnetic surface sources for stationary axisymmetric electrovac spacetimes endowed with non-smooth or even discontinuous Ernst potentials. This can be viewed as a generalization of some classical potential theory results, since lack of continuity of the potential is related to dipole density and lack of smoothness, to monopole density. In particular this approach is useful for constructing the dipole source for the magnetic field. This formalism involves solving a linear elliptic differential equation with boundary conditions at infinity. As an example, two different models of surface densities for the Kerr-Newman electrovac spacetime are derived.Comment: 15 page