6,399 research outputs found
Spacetime torsion and parity violation: a gauge invariant formulation
The possibility of parity violation through spacetime torsion has been
explored in a scenario containing fields with different spins. Taking the
Kalb-Ramond field as the source of torsion, an explicitly parity violating
gauge invariant theory has been constructed by extending the KR
field with a Chern-Simons term.Comment: 4 pages, RevTe
Spectacular Role of Electron Correlation in the Hyperfine Interactions in States in Alkaline Earth Ions
The low-lying n(=3,4,5)d states alkaline earth ions are of vital
importance in a number of different physical applications. The hyperfine
structure constants of these states are characterized by unusually strong
electron correlation effects. Relativistic coupled-cluster theory has been
employed to carry out {\it ab initio} calculations of these constants. The role
of the all order core-polarization effects was found to be decisive in
obtaining good agreement of the results of our calculations with accurate
measurements. The present work is an apt demonstration of the power of the
coupled-cluster method to cope with strongly interacting configurations.Comment: Submitted to Physical Review Letters, 3 figures and 5 table
The formation of supermassive black holes in the first galaxies
We discuss the formation of supermassive black holes in the early universe,
and how to probe their subsequent evolution with the upcoming mm/sub-mm
telescope ALMA. We first focus on the chemical and radiative conditions for
black hole formation, in particular considering radiation trapping and
molecular dissociation effects. We then turn our attention towards the magnetic
properties in the halos where the first black holes form, and show that the
presence of turbulence may lead to a magnetic dynamo, which could support the
black hole formation process by providing an efficient means of transporting
the angular momentum. We finally focus on observable properties of
high-redshift black holes with respect to ALMA, and discuss how to distinguish
between chemistry driven by the starburst and chemistry driven by X-rays from
the black hole.Comment: Contribution to AIP conference proceedings "First Stars and Galaxies:
Challenges in the Next Decade". 4 pages, 3 figure
Spectroscopic Characteristics and Biological Activity against Ehrlich Ascites Carcinoma Cells of some Phenanthrenic Alkaloids
Where are the black hole entropy degrees of freedom ?
Understanding the area-proportionality of black hole entropy (the `Area Law')
from an underlying fundamental theory has been one of the goals of all models
of quantum gravity. A key question that one asks is: where are the degrees of
freedom giving rise to black hole entropy located? Taking the point of view
that entanglement between field degrees of freedom inside and outside the
horizon can be a source of this entropy, we show that when the field is in its
ground state, the degrees of freedom near the horizon contribute most to the
entropy, and the area law is obeyed. However, when it is in an excited state,
degrees of freedom far from the horizon contribute more significantly, and
deviations from the area law are observed. In other words, we demonstrate that
horizon degrees of freedom are responsible for the area law.Comment: 5 pages, 3 eps figures, uses Revtex4, References added, Minor changes
to match published versio
The universe dynamics in the tachyon cosmology with non-minimal coupling to matter
Recently, the tachyon cosmology has been represented as dark energy model to
support the current acceleration of the universe without phantom crossing. In
this paper, we study the dynamics of the tachyon cosmology in which the field
plays the role of tachyon field and also non--minimally coupled to the matter
lagrangian. The model shows current universe acceleration and also phantom
crossing in the future. Two cosmological tests are also performed to validate
the model; the difference in the distance modulus and the model independent
Cosmological Redshift Drift (CRD) test.Comment: 14 pages, 11 figure
Magnetic field amplification during gravitational collapse - influence of turbulence, rotation and gravitational compression
- …