42,063 research outputs found
QFT results for neutrino oscillations and New Physics
The CP asymmetry in neutrino oscillations, assuming new physics at production
and/or detection processes, is analyzed. We compute this CP asymmetry using the
standard quantum field theory within a general new physics scenario that may
generate new sources of CP and flavor violation. Well known results for the CP
asymmetry are reproduced in the case of V -A operators, and additional
contributions from new physics operators are derived. We apply this formalism
to SUSY extensions of the Standard Model where the contributions from new
operators could produce a CP asymmetry observable in the next generation of
neutrino experiments.Comment: 6 pages, 3 figures, version to be published in Phys.Rev.
Charge transfer in heterostructures of strongly correlated materials
In this manuscript, recent theoretical investigations by the authors in the
area of oxide multilayers are briefly reviewed. The calculations were carried
out using model Hamiltonians and a variety of non-perturbative techniques.
Moreover, new results are also included here. They correspond to the generation
of a metallic state by mixing insulators in a multilayer geometry, using the
Hubbard and Double Exchange models. For the latter, the resulting metallic
state is also ferromagnetic. This illustrates how electron or hole doping via
transfer of charge in multilayers can lead to the study of phase diagrams of
transition metal oxides in the clean limit. Currently, these phase diagrams are
much affected by the disordering standard chemical doping procedure, which
introduces quenched disorder in the material.Comment: 14 pages, 9 figures. Invited article for a special issue of JPCM on
Metal Oxide Thin Films; minor changes in the tex
XMM-Newton and Deep Optical Observations of the OTELO fields: the Groth-Westphal Strip
OTELO (OSIRIS Tunable Emission Line Object Survey) will be carried out with
the OSIRIS instrument at the 10 m GTC telescope at La Palma, and is aimed to be
the deepest and richest survey of emission line objects to date. The deep
narrow-band optical data from OSIRIS will be complemented by means of
additional observations that include: (i) an exploratory broad-band survey that
is already being carried out in the optical domain, (ii) FIR and sub-mm
observations to be carried with the Herschel space telescope and the GTM, and
(iii) deep X-Ray observations from XMM-Newton and Chandra.Here we present a
preliminary analysis of public EPIC data of one of the OTELO targets,the
Groth-Westphal strip, gathered from the XMM-Newton Science Archive (XSA). EPIC
images are combined with optical BVRI data from our broadband survey carried
out with the 4.2m WHT at La Palma. Distance-independent diagnostics (involving
X/O ratio, hardness ratios, B/T ratio) are tested.Comment: 2 pages, 2 figures, uses graphicx package. To appear in proceedings
of "The X-Ray Universe 2005", San Lorenzo del Escorial, Spain, September
26-30, 200
Effective temperatures and radii of planet-hosting stars from IR photometry
In this paper we present and analyse determinations of effective temperatures
of planet-hosting stars using infrared (IR) photometry. One of our goals is the
comparison with spectroscopic temperatures to evaluate the presence of
systematic effects that could alter the determination of metal abundances. To
estimate the stellar temperatures we have followed a new approach based on
fitting the observed 2MASS IR photometry with accurately calibrated synthetic
photometry. Special care has been put in evaluating all sources of possible
errors and incorporating them in the analysis. A comparison of our temperature
determinations with spectroscopic temperatures published by different groups
reveals the presence of no systematic trends and a scatter compatible with the
quoted uncertainties of 0.5-1.3%. This mutual agreement strengthens the results
of both the spectroscopic and IR photometry analyses. Comparisons with other
photometric temperature calibrations, generally with poorer performances, are
also presented. In addition, the method employed of fitting IR photometry
naturally yields determinations of the stellar semi-angular diameters, which,
when combined with the distances, results in estimations of the stellar radii
with remarkable accuracies of ~2-4%. A comparison with the only star in the
sample with an empirically determined radius (HD 209458 -- from transit
photometry) indicates excellent agreement.Comment: 4 pages, 1 figure, accepted for publication as a letter in A&
Tin-selenium compounds at ambient and high pressures
SnxSey crystalline compounds consisting of Sn and Se atoms of varying
composition are systematically investigated at pressures from 0 to 100 GPa
using the first-principles evolutionary crystal structure search method based
on density functional theory (DFT). All known experimental phases of SnSe and
SnSe2 are found without any prior input. A second order polymorphic phase
transition from SnSe-Pnma phase to SnSe-Cmcm phase is predicted at 2.5 GPa.
Initially being semiconducting, this phase becomes metallic at 7.3 GPa. Upon
further increase of pressure up to 36.6 GPa, SnSe-Cmcm phase is transformed to
CsCl-type SnSe-Pm3m phase, which remains stable at even higher pressures. A
metallic compound with different stoichiometry, Sn3Se4-I43d, is found to be
thermodynamically stable from 18 GPa to 70 GPa. Known semiconductor tin
diselenide SnSe2-P3m1 phase is found to be thermodynamically stable from
ambient pressure up to 18 GPa. Initially being semiconducting, it experiences
metalization at pressures above 8 GPa
The Virtual Monte Carlo
The concept of Virtual Monte Carlo (VMC) has been developed by the ALICE
Software Project to allow different Monte Carlo simulation programs to run
without changing the user code, such as the geometry definition, the detector
response simulation or input and output formats. Recently, the VMC classes have
been integrated into the ROOT framework, and the other relevant packages have
been separated from the AliRoot framework and can be used individually by any
other HEP project. The general concept of the VMC and its set of base classes
provided in ROOT will be presented. Existing implementations for Geant3, Geant4
and FLUKA and simple examples of usage will be described.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 8 pages, LaTeX, 6 eps figures. PSN
THJT006. See http://root.cern.ch/root/vmc/VirtualMC.htm
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