6,305 research outputs found
Comparative studies of the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of ^{25}Mg^{+}
We have employed the relativistic coupled cluster theory to calculate the
magnetic dipole and electric quadrupole hyperfine constants for the ground and
low lying excited states of singly ionized magnesium. Comparison with
experimental and the other theoretical results are done and predictions are
also made for a few low lying excited states which could be of interest. We
have made comparative studies of the important many body effects contributing
to the hyperfine constants for the different states of the ion.Comment: 3 figures, Late
What can we say about seed fields for galactic dynamos?
We demonstrate that a quasi-uniform cosmological seed field is a much less
suitable seed for a galactic dynamo than has often been believed. The age of
the Universe is insufficient for a conventional galactic dynamo to generate a
contemporary galactic magnetic field starting from such a seed, accepting
conventional estimates for physical quantities. We discuss modifications to the
scenario for the evolution of galactic magnetic fields implied by this result.
We also consider briefly the implications of a dynamo number that is
significantly larger than that given by conventional estimates
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
Problems with kinematic mean field electrodynamics at high magnetic Reynolds numbers
We discuss the applicability of the kinematic -effect formalism at
high magnetic Reynolds numbers. In this regime the underlying flow is likely to
be a small-scale dynamo, leading to the exponential growth of fluctuations.
Difficulties arise with both the actual calculation of the
coefficients and with its interpretation. We argue that although the former may
be circumvented -- and we outline several procedures by which the the
coefficients can be computed in principle -- the interpretation of these
quantities in terms of the evolution of the large-scale field may be
fundamentally flawed.Comment: 5 pages, LaTeX, no figure
Relativistic and correlation effects in atoms
This review article deals with some case studies of relativistic and
correlation effects in atomic systems. After a brief introduction to
relativistic many-electron theory, a number of applications ranging from
correlation energy to parity non-conservation in atoms are considered. There is
a special emphasis on relativistic coupled-cluster theory as most of the
results presented here are based on it.Comment: Review article, 4 eps figures, latex 2
On Stability of the Three 3-brane Model
We show that the Goldberger-Wise mechanism for the three 3-brane scenario proposed by Kogan et al. stabilizes the radion. We find that the system of 3-branes stabilizes in such a way that the loss in the scale factor is insignificant. That is, the negative tension brane chooses to stay close to the visible brane
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