20,184 research outputs found
Two-dimensional Conformal Field Theories on AdS_{2d+1} Backgrounds
Various exact two-dimensional conformal field theories with AdS_{2d+1} target
space are constructed. These models can be solved using bosonization
techniques. Some examples are presented that can be used in building
perturbative superstring theories with AdS backgrounds, including AdS_5.Comment: 36 pages, harvma
Spontaneous electro-weak symmetry breaking and cold dark matter
In the standard model, the weak gauge bosons and fermions obtain mass after
spontaneous electro-weak symmetry breaking, which is realized through one
fundamental scalar field, namely Higgs field. In this paper we study the
simplest scalar cold dark matter model in which the scalar cold dark matter
also obtains mass through interaction with the weak-doublet Higgs field, the
same way as those of weak gauge bosons and fermions. Our study shows that the
correct cold dark matter relic abundance within uncertainty () and experimentally allowed Higgs boson mass
( GeV) constrain the scalar dark matter mass within GeV. This result is in excellent agreement with that of W. de
Boer et.al. ( GeV). Such kind of dark matter annihilation can
account for the observed gamma rays excess () at EGRET for energies
above 1 GeV in comparison with the expectations from conventional Galactic
models. We also investigate other phenomenological consequences of this model.
For example, the Higgs boson decays dominantly into scalar cold dark matter if
its mass lies within GeV.Comment: 4 Revtex4 pages, refs adde
Critical behavior at Mott-Anderson transition: a TMT-DMFT perspective
We present a detailed analysis of the critical behavior close to the
Mott-Anderson transition. Our findings are based on a combination of numerical
and analytical results obtained within the framework of Typical-Medium Theory
(TMT-DMFT) - the simplest extension of dynamical mean field theory (DMFT)
capable of incorporating Anderson localization effects. By making use of
previous scaling studies of Anderson impurity models close to the
metal-insulator transition, we solve this problem analytically and reveal the
dependence of the critical behavior on the particle-hole symmetry. Our main
result is that, for sufficiently strong disorder, the Mott-Anderson transition
is characterized by a precisely defined two-fluid behavior, in which only a
fraction of the electrons undergo a "site selective" Mott localization; the
rest become Anderson-localized quasiparticles.Comment: 4+ pages, 4 figures, v2: minor changes, accepted for publication in
Phys. Rev. Let
Cancellation of quantum mechanical higher loop contributions to the gravitational chiral anomaly
We give an explicit demonstration, using the rigorous Feynman rules developed
in~\0^{1}, that the regularized trace \tr \gamma_5 e^{-\beta \Dslash^2} for
the gravitational chiral anomaly expressed as an appropriate quantum mechanical
path integral is -independent up to two-loop level. Identities and
diagrammatic notations are developed to facilitate rapid evaluation of graphs
given by these rules.Comment: 10 pages, LaTeX and psfig (many figures
Dark matter cores in the Fornax and Sculptor dwarf galaxies: joining halo assembly and detailed star formation histories
We combine the detailed Star Formation Histories of the Fornax and Sculptor
dwarf Spheroidals with the Mass Assembly History of their dark matter (DM) halo
progenitors to estimate if the energy deposited by Supernova type II (SNeII) is
sufficient to create a substantial DM core. Assuming the efficiency of energy
injection of the SNeII into DM particles is , we find
that a single early episode, , that combines the
energy of all SNeII due to explode over 0.5 Gyr, is sufficient to create a core
of several hundred parsecs in both Sculptor and Fornax. Therefore, our results
suggest that it is energetically plausible to form cores in Cold Dark Matter
(CDM) halos via early episodic gas outflows triggered by SNeII. Furthermore,
based on CDM merger rates and phase-space density considerations, we argue that
the probability of a subsequent complete regeneration of the cusp is small for
a substantial fraction of dwarf-size haloes.Comment: ApJL accepted versio
Demonstration project on epilepsy in Brazil - WHO/ILAE/IBE Global Campaign Against Epilepsy - A foreword
In 2002, ASPE (Assistência à Saúde de Pacientes com Epilepsia)* initiated an Epilepsy Demonstration Project (DP) in Brazil as part of the Global Campaign Against Epilepsy "Epilepsy out of the Shadows", led by the World Health Organization (WHO), the International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy (IBE)1-4. Demonstration Projects have been carried out in several countries and their main aim is to develop treatment models for people with epilepsy in primary health care settings, improving the quality of life of people with epilepsy and their families5-9.
The project in Brazil has targeted areas in Campinas and São José do Rio Preto municipalities, both in São Paulo State, in Southeastern region8. A task force has been established to assess strategies to expand this nationwide. The DP was carried out in six phases as shown in Figure 1.
The Brazilian DP was officially closed during the IV Workshop of the WHO/ILAE/IBE Global Campaign Against Epilepsy "Epilepsy out of the Shadows", held on May 4-5th 2006, in Campinas. The workshop reviewed the results of the project and discussed the establishment of a National Epilepsy Policy. This supplement presents some results from all phases of the Brazilian DP which were discussed during the Workshop. In brief, we believe that the DP had an impact in our society and brought a new perspective on epilepsy. Awareness campaigns are now carried out on September 9th (Epilepsy Awareness Day) annually in many sites around the country. Regulations and Bills related to epilepsy have been proposed in several regions. Epilepsy has been officially adopted as a theme to be considered in elementary education by the Ministry of Education. Currently, a National Epilepsy Programme, endorsed by the main Brazilian non-governmental organizations in the field of epilepsy, is under review at the Ministry of Health. We hope that this will benefit some of the many people with epilepsy in the country and will eventually bring epilepsy out of the shadows in Brazil
High-pressure study of the non-Fermi liquid material U_2Pt_2In
The effect of hydrostatic pressure (p<= 1.8 GPa) on the non-Fermi liquid
state of U_2Pt_2In is investigated by electrical resistivity measurements in
the temperature interval 0.3-300 K. The experiments were carried out on
single-crystals with the current along (I||c) and perpendicular (I||a) to the
tetragonal axis. The pressure effect is strongly current-direction dependent.
For I||a we observe a rapid recovery of the Fermi-liquid T^2-term with
pressure. The low-temperature resistivity can be analysed satisfactorily within
the magnetotransport theory of Rosch, which provides strong evidence for the
location of U_2Pt_2In at an antiferromagnetic quantum critical point. For I||c
the resistivity increases under pressure, indicating the enhancement of an
additional scattering mechanism. In addition, we have measured the pressure
dependence of the antiferromagnetic ordering temperature (T_N= 37.6 K) of the
related compound U_2Pd_2In. A simple Doniach-type diagram for U_2Pt_2In and
U_2Pd_2In under pressure is presented.Comment: 21 pages (including 5 figures); pdf forma
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