447 research outputs found
A KK-monopole giant graviton in AdS_5 x Y_5
We construct a new giant graviton solution in AdS_5 x Y_5, with Y_5 a
quasi-regular Sasaki-Einstein manifold, consisting on a Kaluza-Klein monopole
wrapped around the Y_5 and with its Taub-NUT direction in AdS_5. We find that
this configuration has minimal energy when put in the centre of AdS_5, where it
behaves as a massless particle. When we take Y_5 to be S^5, we provide a
microscopical description in terms of multiple gravitational waves expanding
into the fuzzy S^5 defined as an S^1 bundle over the fuzzy CP^2. Finally we
provide a possible field theory dual interpretation of the construction.Comment: 11 pages, published versio
Type II pp-wave Matrix Models from Point-like Gravitons
The BMN Matrix model can be regarded as a theory of coincident M-theory
gravitons, which expand by Myers dielectric effect into the 2-sphere and
5-sphere giant graviton vacua of the theory. In this note we show that, in the
same fashion, Matrix String theory in Type IIA pp-wave backgrounds arises from
the action for coincident Type IIA gravitons. In Type IIB, we show that the
action for coincident gravitons in the maximally supersymmetric pp-wave
background gives rise to a Matrix model which supports fuzzy 3-sphere giant
graviton vacua with the right behavior in the classical limit. We discuss the
relation between our Matrix model and the Tiny Graviton Matrix theory of
hep-th/0406214.Comment: 18 page
Branes wrapping black holes as a purely gravitational dielectric effect
In this paper we give a microscopical description of certain configurations
of branes wrapping black hole horizons in terms of dielectric gravitational
waves. Interestingly, the configurations are stable only due to the
gravitational background. Therefore, this constitutes a nice example of purely
gravitational dielectric effect.Comment: 17 pages, no figures. JHEP published versio
The baryon vertex with magnetic flux
In this letter we generalise the baryon vertex configuration of AdS/CFT by
adding a suitable instantonic magnetic field on its worldvolume, dissolving
D-string charge. A careful analysis of the configuration shows that there is an
upper bound on the number of dissolved strings. This should be a manifestation
of the stringy exclusion principle. We provide a microscopical description of
this configuration in terms of a dielectric effect for the dissolved strings.Comment: 17 pages, 2 figures. V2: reference added. V3: version to appear in
JHE
Efeito hipoglicemiante da farinha do fruto de maracujá-do-mato (Passiflora nitida Kunth) em ratos normais e diabéticos
The Amazon region has a vast biodiversity of fruits but is little explored as to its nutritional and economic potential. Among these fruits is "maracuja-do-mato" (Passiflora nitida Kunth), a wild species of edible fruit with exotic flavor and good acceptability for consumption. The aim of the present study was to analyze the nutritional characteristics of P. nitida fruit mesocarp and to evaluate its hypoglycemic potential in normal and diabetic rats. Flour from the fruit mesocarp was prepared and analyzed as to its centesimal composition. Hypoglycemic activity was assessed by means of two experimental models in Wistar rats. The mesocarp showed low concentration of macronutrients and high humidity, ash and fiber content. In the acute experiment, after 15 minutes of sucrose administration, glucose levels were 146 ± 12 mg dL -1 in the control group and 112 ± 2.5 mg dL -1 in the group receiving 1 g kg -1 flour weight. In the chronic experiment, after 21 days, glucose levels reduced from 493 mg dL -1 to 302 mg dL -1 (38.7%) and 195 mg dL -1 (60.4%) in the groups treated with 20 and 40% animal food enriched with the flour, respectively, in relation to the diabetic untreated group. In both experimental models, the mesocarp flour was effective in reducing blood glucose. P. nitida fruit seems to be a potential natural product in the glycemic control of diabetes
Exact fuzzy sphere thermodynamics in matrix quantum mechanics
We study thermodynamical properties of a fuzzy sphere in matrix quantum
mechanics of the BFSS type including the Chern-Simons term. Various quantities
are calculated to all orders in perturbation theory exploiting the one-loop
saturation of the effective action in the large-N limit. The fuzzy sphere
becomes unstable at sufficiently strong coupling, and the critical point is
obtained explicitly as a function of the temperature. The whole phase diagram
is investigated by Monte Carlo simulation. Above the critical point, we obtain
perfect agreement with the all order results. In the region below the critical
point, which is not accessible by perturbation theory, we observe the Hagedorn
transition. In the high temperature limit our model is equivalent to a totally
reduced model, and the relationship to previously known results is clarified.Comment: 22 pages, 14 figures, (v2) some typos correcte
Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach
The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD
approach. It is found that form factors and branching ratios are sensitive to
the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of
the charmonium wave functions for Coulomb potential and harmonic oscillator
potential, respectively, f_J/psi and f_etac are the decay constants of the
J/psi and etac mesons, respectively. The large branching ratios and the clear
signals of the final states make the Bc --> J/psi pi, etac pi decays to be the
prospective channels for measurements at the hadron collidersComment: 21 pages, revtex
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
The exposure of the hybrid detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays.
It consists of a surface array to measure secondary particles at ground level
and a fluorescence detector to measure the development of air showers in the
atmosphere above the array. The "hybrid" detection mode combines the
information from the two subsystems. We describe the determination of the
hybrid exposure for events observed by the fluorescence telescopes in
coincidence with at least one water-Cherenkov detector of the surface array. A
detailed knowledge of the time dependence of the detection operations is
crucial for an accurate evaluation of the exposure. We discuss the relevance of
monitoring data collected during operations, such as the status of the
fluorescence detector, background light and atmospheric conditions, that are
used in both simulation and reconstruction.Comment: Paper accepted by Astroparticle Physic
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