3,847 research outputs found
New classical properties of quantum coherent states
A noncommutative version of the Cramer theorem is used to show that if two quantum systems are prepared independently, and if their center of mass is found to be in a coherent state, then each of the component systems is also in a coherent state, centered around the position in phase space predicted by the classical theory. Thermal coherent states are also shown to possess properties similar to classical ones
Flat wormholes from straight cosmic strings
Special multi-cosmic string metrics are analytically extended to describe
configurations of Wheeler-Misner wormholes and ordinary cosmic strings. I
investigate in detail the case of flat, asymptotically Minkowskian,
Wheeler-Misner wormhole spacetimes generated by two cosmic strings, each with
tension .Comment: 5 pages, latex, no figure
Nonabelian special K-flows
AbstractThe Kolmogorov-Sinai theory of special K-flows is enlarged to a class of nonabelian dynamical systems whose stochastic behavior is analyzed. The main result of this paper is that these dynamical systems retain the fundamental property of having homogeneous Lebesgue spectrum with countably infinite multiplicity
The randomization by Wishart laws and the Fisher information
Consider the centered Gaussian vector in with covariance matrix Randomize such that has a Wishart distribution
with shape parameter and mean We compute the density
of as well as the Fisher information of the
model when is the parameter. For using the
Cram\'er-Rao inequality, we also compute the inverse of . The
important point of this note is the fact that this inverse is a linear
combination of two simple operators on the space of symmetric matrices, namely
and . The Fisher information itself is a linear
combination and Finally, by
randomizing itself, we make explicit the minoration of the second
moments of an estimator of by the Van Trees inequality: here again,
linear combinations of and appear in the results.Comment: 11 page
An approach to anomalous diffusion in the n-dimensional space generated by a self-similar Laplacian
We analyze a quasi-continuous linear chain with self-similar distribution of
harmonic interparticle springs as recently introduced for one dimension
(Michelitsch et al., Phys. Rev. E 80, 011135 (2009)). We define a continuum
limit for one dimension and generalize it to dimensions of the
physical space. Application of Hamilton's (variational) principle defines then
a self-similar and as consequence non-local Laplacian operator for the
-dimensional space where we proof its ellipticity and its accordance (up to
a strictly positive prefactor) with the fractional Laplacian
. By employing this Laplacian we establish a
Fokker Planck diffusion equation: We show that this Laplacian generates
spatially isotropic L\'evi stable distributions which correspond to L\'evi
flights in -dimensions. In the limit of large scaled times the obtained distributions exhibit an algebraic decay independent from the initial distribution
and spacepoint. This universal scaling depends only on the ratio of
the dimension of the physical space and the L\'evi parameter .Comment: Submitted manuscrip
X-rays from Saturn: A study with XMM-Newton and Chandra over the years 2002-05
We present the results of the two most recent (2005) XMM-Newton observations
of Saturn together with the re-analysis of an earlier (2002) observation from
the XMM-Newton archive and of three Chandra observations in 2003 and 2004.
While the XMM-Newton telescope resolution does not enable us to resolve
spatially the contributions of the planet's disk and rings to the X-ray flux,
we can estimate their strengths and their evolution over the years from
spectral analysis, and compare them with those observed with Chandra. The
spectrum of the X-ray emission is well fitted by an optically thin coronal
model with an average temperature of 0.5 keV. The addition of a fluorescent
oxygen emission line at ~0.53 keV improves the fits significantly. In
accordance with earlier reports, we interpret the coronal component as emission
from the planetary disk, produced by the scattering of solar X-rays in Saturn's
upper atmosphere, and the line as originating from the Saturnian rings. The
strength of the disk X-ray emission is seen to decrease over the period 2002 -
2005, following the decay of solar activity towards the current minimum in the
solar cycle. By comparing the relative fluxes of the disk X-ray emission and
the oxygen line, we suggest that the line strength does not vary over the years
in the same fashion as the disk flux. We consider possible alternatives for the
origin of the line. The connection between solar activity and the strength of
Saturn's disk X-ray emission is investigated and compared with that of Jupiter.
We also discuss the apparent lack of X-ray aurorae on Saturn and conclude that
they are likely to lie below the sensitivity threshold of current Earth-bound
observatories. A similar comparison for Uranus and Neptune leads to the same
disappointing conclusion.Comment: 10 pages, 5 figures; to be published in 'Astronomy and Astrophysics
Prospects for Direct CP Violaton in Exclusive and Inclusive Charmless B decays
Within the Standard Model, CP rate asymmetries for could
reach 10%. With strong final state phases, they could go up to 20--30%, even
for mode which would have opposite sign. We can account for
, and rate data with new physics enhanced
color dipole coupling and destructive interference. Asymmetries could reach
40--60% for and modes and are all of the same sign. We are
unable to account for rate. Our inclusive study supports our
exclusive results.Comment: Minor changes, correct a small bug in Fig. 1(b). Version to appear in
Phys. Rev. Let
Phase Space Models for Stochastic Nonlinear Parabolic Waves: Wave Spread and Singularity
We derive several kinetic equations to model the large scale, low Fresnel
number behavior of the nonlinear Schrodinger (NLS) equation with a rapidly
fluctuating random potential. There are three types of kinetic equations the
longitudinal, the transverse and the longitudinal with friction. For these
nonlinear kinetic equations we address two problems: the rate of dispersion and
the singularity formation.
For the problem of dispersion, we show that the kinetic equations of the
longitudinal type produce the cubic-in-time law, that the transverse type
produce the quadratic-in-time law and that the one with friction produces the
linear-in-time law for the variance prior to any singularity.
For the problem of singularity, we show that the singularity and blow-up
conditions in the transverse case remain the same as those for the homogeneous
NLS equation with critical or supercritical self-focusing nonlinearity, but
they have changed in the longitudinal case and in the frictional case due to
the evolution of the Hamiltonian
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