12,691 research outputs found
On the gravitational stability of D1-D5-P black holes
We examine the stability of the nonextremal D1-D5-P black hole solutions. In
particular, we look for the appearance of a superradiant instability for the
spinning black holes but we find no evidence of such an instability. We compare
this situation with that for the smooth soliton geometries, which were recently
observed to suffer from an ergoregion instability, and consider the
implications for the fuzzball proposal.Comment: 18 pages, 3 figures. Minor comments added to match published versio
Stabilization of the Electroweak Scale in 3-3-1 Models
One way of avoiding the destabilization of the electroweak scale through a
strong coupled regime naturally occurs in models with a Landau-like pole at the
TeV scale. Hence, the quadratic divergence contributions to the scalar masses
are not considered as a problem anymore since a new nonperturbative dynamic
emerges at the TeV scale. This scale should be an intrinsic feature of the
models and there is no need to invoke any other sort of protection for the
electroweak scale. In some models based on the gauge symmetry, a nonperturbative dynamics arise and it stabilizes
the electroweak scale.Comment: 10 pages. Version with some improvements and corrections in the tex
A procedure for testing the quality of LANDSAT atmospheric correction algorithms
There are two basic methods for testing the quality of an algorithm to minimize atmospheric effects on LANDSAT imagery: (1) test the results a posteriori, using ground truth or control points; (2) use a method based on image data plus estimation of additional ground and/or atmospheric parameters. A procedure based on the second method is described. In order to select the parameters, initially the image contrast is examined for a series of parameter combinations. The contrast improves for better corrections. In addition the correlation coefficient between two subimages, taken at different times, of the same scene is used for parameter's selection. The regions to be correlated should not have changed considerably in time. A few examples using this proposed procedure are presented
Closing the Symmetry at Electroweak Scale
We show that some models with gauge
symmetry can be realized at the electroweak scale and that this is a
consequence of an approximate global symmetry. This symmetry
implies a condition among the vacuum expectation value of one of the neutral
Higgs scalars, the 's coupling constant, , the sine of the weak
mixing angle , and the mass of the boson, . In the limit
in which this symmetry is valid it avoids the tree level mixing of the
boson of the Standard Model with the extra boson. We have verified
that the oblique parameter is within the allowed range indicating that the
radiative corrections that induce such a mixing at the 1-loop level are small.
We also show that a custodial symmetry implies that in some of
the models we have to include sterile (singlets of the 3-3-1 symmetry)
right-handed neutrinos with Majorana masses, being the see-saw mechanism
mandatory to obtain light active neutrinos. Moreover, the approximate
symmetry implies that the extra non-standard
particles of these 3-3-1 models can be considerably lighter than it had been
thought before so that new physics can be really just around the corner.Comment: 32 pages, no figure, RevTeX. Some typos correcte
Phase diagram of the antiferromagnetic XY model in two dimensions in a magnetic field
The phase diagram of the quasi-two-dimensional easy-plane antiferromagnetic
model, with a magnetic field applied in the easy plane, is studied using the
self-consistent harmonic approximation. We found a linear dependence of the
transition temperature as a function of the field for large values of the
field. Our results are in agreement with experimental data for the spin-1
honeycomb compound BaNi_2V_2O_3Comment: 3 page
(In)Consistencies in responses to sodium bicarbonate supplementation: a randomised, repeated measures, counterbalanced and double-blind study
Objectives:
Intervention studies do not account for high within-individual variation potentially compromising the magnitude of an effect. Repeat administration of a treatment allows quantification of individual responses and determination of the consistency of responses. We determined the consistency of metabolic and exercise responses following repeated administration of sodium bicarbonate (SB).
Design and Methods:
15 physically active males (age 25 ± 4 y; body mass 76.0 ± 7.3 kg; height 1.77 ± 0.05 m) completed six cycling capacity tests at 110% of maximum power output (CCT 110% ) following ingestion of either 0.3 g.kg -1 BM of SB (4 trials) or placebo (PL, 2 trials). Blood pH, bicarbonate, base excess and lactate were determined at baseline, pre-exercise, post-exercise and 5-min post-exercise. Total work done (TWD) was recorded as the exercise outcome.
Results:
SB supplementation increased blood pH, bicarbonate and base excess prior to every trial (all p ≤0.001); absolute changes in pH, bicarbonate and base excess from baseline to pre-exercise were similar in all SB trials (all p > 0.05). Blood lactate was elevated following exercise in all trials (p ≤ 0.001), and was higher in some, but not all, SB trials compared to PL. TWD was not significantly improved with SB vs. PL in any trial (SB1: +3.6%; SB2 +0.3%; SB3: +2.1%; SB4: +6.7%; all p > 0.05), although magnitude-based inferences suggested a 93% likely improvement in SB4. Individual analysis showed ten participants improved in at least one SB trial above the normal variation of the test although five improved in none.
Conclusions:
The mechanism for improved exercise with SB was consistently in place prior to exercise, although this only resulted in a likely improvement in one trial. SB does not consistently improve high intensity cycling capacity, with results suggesting that caution should be taken when interpreting the results from single trials as to the efficacy of SB supplementation.
Trial Registration:
ClinicalTrials.gov NCT0247462
Electronic Phase Separation Transition as the Origin of the Superconductivity and the Pseudogap Phase of Cuprates
We propose a new phase of matter, an electronic phase separation transition
that starts near the upper pseudogap and segregates the holes into high and low
density domains. The Cahn-Hilliard approach is used to follow quantitatively
this second order transition. The resulting grain boundary potential confines
the charge in domains and favors the development of intragrain superconducting
amplitudes. The zero resistivity transition arises only when the intergrain
Josephson coupling is of the order of the thermal energy and phase
locking among the superconducting grains takes place. We show that this
approach explains the pseudogap and superconducting phases in a natural way and
reproduces some recent scanning tunneling microscopy dataComment: 4 pages and 5 eps fig
Análise do comportamento da farinha do fruto da pupunheira em produtos alimentícios.
Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos
Ecologia da polinização de Raphiodon echinus (Nees & Mart.) Schau (Lamiaceae) no município de Petrolina-PE.
No presente trabalho foram observados a fenologia, biologia floral e o sistema reprodutivo desta espécie com o objetivo de contribuir com informações sobre sua ecologia da polinização
Mértola in Late Antiquity: new archeological and epigraphic data
En Mértola se ha encontrado recientemente un considerable grupo de inscripciones paleocristianas que se asocian a dos monumentos de la Antigüedad Tardía. Uno de ellos parcialmente conocido, otro totalmente inédito. Los dos han sido objeto de excavaciones entre 2008 y 2009. Los nuevos textos epigráficos vienen a aumentar la ya numerosa colección epigráfica conocida y a reforzar la idea del uso de las lenguas griega y latina en el seno de una misma comunidad, la del puerto fluvial de Mértola, en el siglo VI d.C.Recently a new group of paleochristian inscriptions and two new monuments were found in Mértola. One of them was already known, but the other was ignored till now. Both were excavated between 2008 and 2009. The new epigraphic texts increase the large epigraphical collection already known, reinforcing the idea that both latin and greek were used within the same community, in the fluvial harbour of Mértola, in VI century a.C
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