Radiative corrections to the lightest KK states in the T^2/(Z_2\times Z_2') orbifold

We study radiative corrections localized in the fixed points of the orbifold for the field theory in six dimensions with two dimensions compactified on the $T_2/(Z_2\times Z_2')$ orbifold in a specific realistic model for low energy physics that solves the proton decay and neutrino mass problem. We calculate corrections to the masses of the lightest stable KK modes, which could be the candidates for the dark matter.Comment: 14 pages, 2 figure

Selenium interactions with algae: Chemical processes at biological uptake sites, bioaccumulation, and intracellular metabolism

Selenium (Se) uptake by primary producers is the most variable and important step in determining Se concentrations at higher trophic levels in aquatic food webs. We gathered data available about the Se bioaccumulation at the base of aquatic food webs and analyzed its relationship with Se concentrations in water. This important dataset was separated into lotic and lentic systems to provide a reliable model to estimate Se in primary producers from aqueous exposure. We observed that lentic systems had higher organic selenium and selenite concentrations than in lotic systems and selenate concentrations were higher in lotic environments. Selenium uptake by algae is mostly driven by Se concentrations, speciation and competition with other anions, and is as well influenced by pH. Based on Se species uptake by algae in the laboratory, we proposed an accurate mechanistic model of competition between sulfate and inorganic Se species at algal uptake sites. Intracellular Se transformations and incorporation into selenoproteins as well as the mechanisms through which Se can induce toxicity in algae has also been reviewed. We provided a new tool for risk assessment strategies to better predict accumulation in primary consumers and consequently to higher trophic levels, and we identified some research needs that could fill knowledge gaps

Material-independent crack arrest statistics: Application to indentation experiments

An extensive experimental study of indentation and crack arrest statistics is presented for four different brittle materials (alumina, silicon carbide, silicon nitride, glass). Evidence is given that the crack length statistics can be described by a universal (i.e. material independent) distribution. The latter directly derives from results obtained when modeling crack propagation as a depinning phenomenon. Crack arrest (or effective toughness) statistics appears to be fully characterized by two parameters, namely, an asymptotic crack length (or macroscopic toughness) value and a power law size dependent width. The experimental knowledge of the crack arrest statistics at one given scale thus gives access to its knowledge at all scales

Completely localized gravity with higher curvature terms

In the intersecting braneworld models, higher curvature corrections to the Einstein action are necessary to provide a non-trivial geometry (brane tension) at the brane junctions. By introducing such terms in a Gauss-Bonnet form, we give an effective description of localized gravity on the singular delta-function branes. There exists a non-vanishing brane tension at the four-dimensional brane intersection of two 4-branes. Importantly, we give explicit expressions of the graviton propagator and show that the Randall-Sundrum single-brane model with a Gauss-Bonnet term in the bulk correctly gives a massless graviton on the brane as for the RS model. We explore some crucial features of completely localized gravity in the solitonic braneworld solutions obtained with a choice (\xi=1) of solutions. The no-go theorem known for Einstein's theory may not apply to the \xi=1 solution. As complementary discussions, we provide an effective description of the power-law corrections to Newtonian gravity on the branes or at the common intersection thereof.Comment: 19 pages, LaTeX, Revised/Published Versio

Scalar Hair of Global Defect and Black Brane World

We consider a complex scalar field in (p+3)-dimensional bulk with a negative cosmological constant and study global vortices in two extra-dimensions. We reexamine carefully the coupled scalar and Einstein equations, and show that the boundary value of scalar amplitude at infinity of the extra-dimensions should be smaller than vacuum expectation value. The brane world has a cigar-like geometry with an exponentially decaying warp factor and a flat thick p-brane is embedded. Since a coordinate transformation identifies the obtained brane world as a black p-brane world bounded by a horizon, this strange boundary condition of the scalar amplitude is understood as existence of a short scalar hair.Comment: 26 pages, 2 figure

ACQUIRING SEISMIC DATA IN THE NORTH-EAST OF ITALY: THE OGS-CRS EXPERIENCE IN USING THE ANTELOPE SOFTWARE SUITE

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FW propagation and absorption in reactor plasmas in the ICR frequency range at the quasiperpendicular propagation

On the base of the numerical model, taking into account the strong transverse and longitudinal dispersion of plasma, the absorption and dispersion of the Fast Mode of fast magnetosonic wave (FW) near ICR harmonics ω=nωci at the quasiperpendicular propagation regime were investigated. It was shown that in the region of small longitudinal refractive index values NII there appears the additional absorption that provides the value of optical thickness τ being constant in the entire region of additional absorption. At first and second harmonics the additional absorption can be interesting for FW plasma heating in the reactor-size devices. For higher harmonics it can be important for HF diagnostic purposes and for investigation of astrophysical plasmas.Дисперсия и поглощение быстрой моды быстрой магнитозвуковой волны (БВ) в области ионных циклотронных гармоник ω=nωci исследованы на основе численной модели, учитывающей сильную продольную и поперечную дисперсии плазмы. Показано, что в области малых продольных замедлений появляется дополнительное поглощение, которое обеспечивает постоянное значение оптической толщи во всей области проявления дополнительного поглощения. На первой и второй гармониках такое поглощение может быть интересно для нагрева реакторной плазмы. Для более высоких гармоник оно может быть важным для ВЧ-диагностики, а также для исследования астрофизической плазмы.Дисперсія і поглинання швидкої моди швидкої магнітозвукової хвилі (ШХ) в області іонних циклотронних гармонік ω=nωci досліджені на основі чисельної моделі, що враховує сильну поздовжню і поперечну дисперсії плазми. Показано, що в області малих поздовжніх уповільнень з'являється додаткове поглинання, яке забезпечує постійне значення оптичної товщі у всій області прояви додаткового поглинання. На першій і другій гармоніках таке поглинання може бути цікавим для нагріву реакторної плазми. Для більш високих гармонік воно може бути важливим для ВЧ-діагностики, а також для дослідження астрофізичної плазми

A Brief Review on Dark Matter Annihilation Explanation for e±e^\pm Excesses in Cosmic Ray

Recently data from PAMELA, ATIC, FERMI-LAT and HESS show that there are $e^{\pm}$ excesses in the cosmic ray energy spectrum. PAMELA observed excesses only in $e^+$, but not in anti-proton spectrum. ATIC, FERMI-LAT and HESS observed excesses in $e^++e^-$ spectrum, but the detailed shapes are different which requires future experimental observations to pin down the correct data set. Nevertheless a lot of efforts have been made to explain the observed $e^\pm$ excesses, and also why PAMELA only observed excesses in $e^+$ but not in anti-proton. In this brief review we discuss one of the most popular mechanisms to explain the data, the dark matter annihilation. It has long been known that about 23% of our universe is made of relic dark matter. If the relic dark matter was thermally produced, the annihilation rate is constrained resulting in the need of a large boost factor to explain the data. We will discuss in detail how a large boost factor can be obtained by the Sommerfeld and Briet-Wigner enhancement mechanisms. Some implications for particle physics model buildings will also be discussed.Comment: 22 pages, 6 figures. Several typoes corrected and some references added. Published in Mod. Phys. Lett. A, Vol. 24, No. 27 (2009) pp. 2139-216

Modulus stabilization of generalized Randall Sundrum model with bulk scalar field

We study the stabilization of inter-brane spacing modulus of generalized warped brane models with a nonzero brane cosmological constant. Employing Goldberger-Wise stabilization prescription of brane world models with a bulk scalar field, we show that the stabilized value of the modulus generally depends on the value of the brane cosmological constant. Our result further reveals that the stabilized modulus value corresponding to a vanishingly small cosmological constant can only resolve the gauge hierarchy problem simultaneously. This in turn vindicates the original Randall-Sundrum model where the 3-brane cosmological constant was chosen to be zero.Comment: 12 Pages, 1 figure, Revtex, Version to appear in Euro. Phys. Let

Supergravity, Non-Conformal Field Theories and Brane-Worlds

We consider the supergravity dual descriptions of non-conformal super Yang-Mills theories realized on the world-volume of Dp-branes. We use the dual description to compute stress-energy tensor and current correlators. We apply the results to the study of dilatonic brane-worlds described by non-conformal field theories coupled to gravity. We find that brane-worlds based on D4 and D5 branes exhibit a localization of gauge and gravitational fields. We calculate the corrections to the Newton and Coulomb laws in these theories.Comment: 24 pages, Latex, 2 figure