16,667 research outputs found
Gravitational wave recoils in non-axisymmetric Robinson-Trautman spacetimes
We examine the gravitational wave recoil waves and the associated net kick
velocities in non-axisymmetric Robinson-Trautman spacetimes. We use
characteristic initial data for the dynamics corresponding to non-head-on
collisions of black holes. We make a parameter study of the kick distributions,
corresponding to an extended range of the incidence angle in the
initial data. For the range of examined () the kick distributions as a function of the symmetric mass
parameter satisfy a law obtained from an empirical modification of the
Fitchett law, with a parameter that accounts for the non-zero net
gravitational momentum wave fluxes for the equal mass case. The law fits
accurately the kick distributions for the range of examined, with a
rms normalized error of the order of . For the equal mass case the
nonzero net gravitational wave momentum flux increases as increases,
up to beyond which it decreases. The maximum net
kick velocity is about for for the boost parameter considered.
For the distribution is a monotonous function of
. The angular patterns of the gravitational waves emitted are examined.
Our analysis includes the two polarization modes present in wave zone
curvature.Comment: 10 pages, 5 figures. arXiv admin note: substantial text overlap with
arXiv:1403.4581, arXiv:1202.1271, arXiv:1111.122
Anisotropy and percolation threshold in a multifractal support
Recently a multifractal object, , was proposed to study percolation
properties in a multifractal support. The area and the number of neighbors of
the blocks of show a non-trivial behavior. The value of the
probability of occupation at the percolation threshold, , is a function
of , a parameter of which is related to its anisotropy. We
investigate the relation between and the average number of neighbors of
the blocks as well as the anisotropy of
Nonclassical correlation in NMR quadrupolar systems
The existence of quantum correlation (as revealed by quantum discord), other
than entanglement and its role in quantum-information processing (QIP), is a
current subject for discussion. In particular, it has been suggested that this
nonclassical correlation may provide computational speedup for some quantum
algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been
successfully used as a test bench for many QIP implementations, although it has
also been continuously criticized for not presenting entanglement in most of
the systems used so far. In this paper, we report a theoretical and
experimental study on the dynamics of quantum and classical correlations in an
NMR quadrupolar system. We present a method for computing the correlations from
experimental NMR deviation-density matrices and show that, given the action of
the nuclear-spin environment, the relaxation produces a monotonic time decay in
the correlations. Although the experimental realizations were performed in a
specific quadrupolar system, the main results presented here can be applied to
whichever system uses a deviation-density matrix formalism.Comment: Published versio
Strong evidences for a nonextensive behavior of the rotation period in Open Clusters
Time-dependent nonextensivity in a stellar astrophysical scenario combines
nonextensive entropic indices derived from the modified Kawaler's
parametrization, and , obtained from rotational velocity distribution. These
's are related through a heuristic single relation given by , where is the cluster age. In a nonextensive
scenario, these indices are quantities that measure the degree of
nonextensivity present in the system. Recent studies reveal that the index
is correlated to the formation rate of high-energy tails present in the
distribution of rotation velocity. On the other hand, the index is
determined by the stellar rotation-age relationship. This depends on the
magnetic field configuration through the expression , where
and denote the saturation level of the star magnetic field and its
topology, respectively. In the present study, we show that the connection
is also consistent with 548 rotation period data for single
main-sequence stars in 11 Open Clusters aged less than 1 Gyr. The value of
2.5 from our unsaturated model shows that the mean magnetic field
topology of these stars is slightly more complex than a purely radial field.
Our results also suggest that stellar rotational braking behavior affects the
degree of anti-correlation between and cluster age . Finally, we suggest
that stellar magnetic braking can be scaled by the entropic index .Comment: 6 pages and 2 figures, accepted to EPL on October 17, 201
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