2,176 research outputs found
Nuclear time-reversal violation and the Schiff moment of 225Ra
We present a comprehensive mean-field calculation of the Schiff moment of the
nucleus 225Ra, the quantity which determines the static electric dipole moment
of the corresponding atom if time-reversal (T) invariance is violated in the
nucleus. The calculation breaks all possible intrinsic symmetries of the
nuclear mean field and includes, in particular, both exchange and direct terms
from the full finite-range T-violating nucleon-nucleon interaction, and the
effects of short-range correlations. The resulting Schiff moment, which depends
on three unknown T-violating pion-nucleon coupling constants, is much larger
than in 199Hg, the isotope with the best current experimental limit on its
atomic electric-dipole moment.Comment: 4 pages, 2 figures; this version (references added) to be published
in PR
Exact cosmological solutions with nonminimal derivative coupling
We consider a gravitational theory of a scalar field with nonminimal
derivative coupling to curvature. The coupling terms have the form and where
and are coupling parameters with dimensions of
length-squared. In general, field equations of the theory contain third
derivatives of and . However, in the case
the derivative coupling term reads and the order of corresponding field equations
is reduced up to second one. Assuming , we study the
spatially-flat Friedman-Robertson-Walker model with a scale factor and
find new exact cosmological solutions. It is shown that properties of the model
at early stages crucially depends on the sign of . For negative
the model has an initial cosmological singularity, i.e. in the limit ; and for positive the universe
at early stages has the quasi-de Sitter behavior, i.e. in the
limit , where . The corresponding scalar
field is exponentially growing at , i.e. . At late stages the universe evolution does not depend on
at all; namely, for any one has at
. Summarizing, we conclude that a cosmological model with
nonminimal derivative coupling of the form is able to explain in a unique manner both a
quasi-de Sitter phase and an exit from it without any fine-tuned potential.Comment: 7 pages, 2 figures. Accepted to PR
Possible doublet mechanism for a regular component of parity violation in neutron scattering
A nucleus with octupole deformation of the mean field reveals rotational
doublets with the same angular momentum and opposite parity. Mediated by the
Coriolis-type interaction, the doublet structure leads to a strong regular
component in the parity violation caused by weak interaction. This can explain
sign correlations observed in polarized neutron scattering by Th.Comment: 10 pages, revtex, no figure
Screening and finite size corrections to the octupole and Schiff moments
Parity (P) and time reversal (T) violating nuclear forces create P, T -odd
moments in expansion of the nuclear electrostatic potential. We derive
expression for the nuclear electric octupole field which includes the electron
screening correction (similar to the screening term in the Schiff moment). Then
we calculate the Z alpha corrections to the Schiff moment which appear due to
the finite nuclear size. Such corrections are important in heavy atoms with
nuclear charge Z > 50. The Schiff and octupole moments induce atomic electric
dipole moments (EDM) and P, T -odd interactions in molecules which are measured
in numerous experiments to test CP-violation theories
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