10,397 research outputs found
Unification of SU(2)xU(1) Using a Generalized Covariant Derivative and U(3)
A generalization of the Yang-Mills covariant derivative, that uses both
vector and scalar fields and transforms as a 4-vector contracted with Dirac
matrices, is used to simplify and unify the Glashow-Weinberg-Salam model. Since
SU(3) assigns the wrong hypercharge to the Higgs boson, it is necessary to use
a special representation of U(3) to obtain all the correct quantum numbers. A
surplus gauge scalar boson emerges in the process, but it uncouples from all
other particles.Comment: 12 pages, no figures. To be published in Int. J. Mod. Phys.
Effect of hybridization on the magnetic properties of correlated two-band metals
The magnetic properties of transition-like metals are discussed within the
single site approximation, which is a picture to take into account electron
correlations. The metal is described by two hybridized bands one of which
includes Coulomb correlation. The presented results indicate that
ferromagnetism arises for adequate values of hybridization (V), correlation (U)
and occupation number(). Some similarities with Dynamical
Mean-Field Theory (DMFT) are indicated.Comment: 3 pages, 3 figures, presented at the 53rd MMM08 conference in Austin,
200
Pseudogap and the specific heat of high superconductors
The specific heat of a two dimensional repulsive Hubbard model with local
interaction is investigated. We use the two-pole approximation which exhibits
explicitly important correlations that are sources of the pseudogap anomaly.
The interplay between the specific heat and the pseudogap is the main focus of
the present work. Our self consistent numerical results show that above the
occupation , the specific heat starts to decrease due to the
presence of a pseudogap in the density of states. We have also observed a two
peak structure in the specific heat. Such structure is robust with respect to
the Coulomb interaction but it is significantly affected by the occupation
. A detailed study of the two peak structure is carried out in terms of
the renormalized quasi-particle bands. The role of the second nearest neighbor
hopping on the specific heat behavior and on the pseudogap, is extensively
discussed.Comment: 6 pages, 6 figures, accepted for publication in Solid State
Communication
Diferenças entre os sexos na esquizofrenia
UNIFESP-EPM Departamento de PsiquiatriaUNIFESP, EPM, Depto. de PsiquiatriaSciEL
Charting the TeV Milky Way: H.E.S.S. Galactic plane survey maps, catalog and source populations
Very-high-energy (VHE, E>100 GeV) gamma-rays provide a unique view of the
non-thermal universe, tracing the most violent and energetic phenomena at work
inside our Galaxy and beyond. The latest results of the H.E.S.S. Galactic Plane
Survey (HGPS) undertaken by the High Energy Stereoscopic System (H.E.S.S.), an
array of four imaging atmospheric Cherenkov telescopes located in Namibia, are
described here. The HGPS aims at the detection of cosmic accelerators with
environments suitable for the production of photons at the highest energies and
has led to the discovery of an unexpectedly large and diverse population of
over 60 sources of TeV gamma rays within its current range of l = 250 to 65
degrees in longitude and |b|<3.5 degrees in latitude. The data set of the HGPS
comprises 2800 hours of high-quality data, taken in the years 2004 to 2013. The
sensitivity for the detection of point-like sources, assuming a power-law
spectrum with a spectral index of 2.3 at a statistical significance of 5 sigma,
is now at the level of 2% Crab or better in the core HGPS region. The latest
maps of the inner Galaxy at TeV energies are shown alongside an introduction to
the first H.E.S.S. Galactic Plane Survey catalog. Finally, in addition to an
overview of the H.E.S.S. Galactic source population a few remarkable, recently
discovered sources will be highlighted.Comment: 8 pages, 6 figures, in Proceedings of the 48th Rencontres de Moriond
(2013), La Thuile (Italy
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