3,666 research outputs found
Colour level set regularization for the electromagnetic imaging of highly discontinuous parameters in 3D*
A generalized bayesian inference method for constraining the interiors of super Earths and sub-Neptunes
We aim to present a generalized Bayesian inference method for constraining
interiors of super Earths and sub-Neptunes. Our methodology succeeds in
quantifying the degeneracy and correlation of structural parameters for high
dimensional parameter spaces. Specifically, we identify what constraints can be
placed on composition and thickness of core, mantle, ice, ocean, and
atmospheric layers given observations of mass, radius, and bulk refractory
abundance constraints (Fe, Mg, Si) from observations of the host star's
photospheric composition. We employed a full probabilistic Bayesian inference
analysis that formally accounts for observational and model uncertainties.
Using a Markov chain Monte Carlo technique, we computed joint and marginal
posterior probability distributions for all structural parameters of interest.
We included state-of-the-art structural models based on self-consistent
thermodynamics of core, mantle, high-pressure ice, and liquid water.
Furthermore, we tested and compared two different atmospheric models that are
tailored for modeling thick and thin atmospheres, respectively. First, we
validate our method against Neptune. Second, we apply it to synthetic
exoplanets of fixed mass and determine the effect on interior structure and
composition when (1) radius, (2) atmospheric model, (3) data uncertainties, (4)
semi-major axes, (5) atmospheric composition (i.e., a priori assumption of
enriched envelopes versus pure H/He envelopes), and (6) prior distributions are
varied. Our main conclusions are: [...]Comment: Astronomy & Astrophysics, 597, A37, 17 pages, 11 figure
Coordinate representation of particle dynamics in AdS and in generic static spacetimes
We discuss the quantum dynamics of a particle in static curved spacetimes in
a coordinate representation. The scheme is based on the analysis of the squared
energy operator E^2, which is quadratic in momenta and contains a scalar
curvature term. Our main emphasis is on AdS spaces, where this term is fixed by
the isometry group. As a byproduct the isometry generators are constructed and
the energy spectrum is reproduced. In the massless case the conformal symmetry
is realized as well. We show the equivalence between this quantization and the
covariant quantization, based on the Klein-Gordon type equation in AdS. We
further demonstrate that the two quantization methods in an arbitrary
(N+1)-dimensional static spacetime are equivalent to each other if the scalar
curvature terms both in the operator E^2 and in the Klein-Gordon type equation
have the same coefficient equal to (N-1)/(4N).Comment: 14 pages, no figures, typos correcte
Accumulation horizons and period-adding in optically injected semiconductor lasers
We study the hierarchical structuring of islands of stable periodic
oscillations inside chaotic regions in phase diagrams of single-mode
semiconductor lasers with optical injection. Phase diagrams display remarkable
{\it accumulation horizons}: boundaries formed by the accumulation of infinite
cascades of self-similar islands of periodic solutions of ever-increasing
period. Each cascade follows a specific period-adding route. The riddling of
chaotic laser phases by such networks of periodic solutions may compromise
applications operating with chaotic signals such as e.g. secure communications.Comment: 4 pages, 4 figures, laser phase diagrams, to appear in Phys. Rev. E,
vol. 7
Electron impact double ionization of helium from classical trajectory calculations
With a recently proposed quasiclassical ansatz [Geyer and Rost, J. Phys. B 35
(2002) 1479] it is possible to perform classical trajectory ionization
calculations on many electron targets. The autoionization of the target is
prevented by a M\o{}ller type backward--forward propagation scheme and allows
to consider all interactions between all particles without additional
stabilization. The application of the quasiclassical ansatz for helium targets
is explained and total and partially differential cross sections for electron
impact double ionization are calculated. In the high energy regime the
classical description fails to describe the dominant TS1 process, which leads
to big deviations, whereas for low energies the total cross section is
reproduced well. Differential cross sections calculated at 250 eV await their
experimental confirmation.Comment: LaTeX, 22 pages, 10 figures, submitted to J. Phys.
Loop Equation in Two-dimensional Noncommutative Yang-Mills Theory
The classical analysis of Kazakov and Kostov of the Makeenko-Migdal loop
equation in two-dimensional gauge theory leads to usual partial differential
equations with respect to the areas of windows formed by the loop. We extend
this treatment to the case of U(N) Yang-Mills defined on the noncommutative
plane. We deal with all the subtleties which arise in their two-dimensional
geometric procedure, using where needed results from the perturbative
computations of the noncommutative Wilson loop available in the literature. The
open Wilson line contribution present in the non-commutative version of the
loop equation drops out in the resulting usual differential equations. These
equations for all N have the same form as in the commutative case for N to
infinity. However, the additional supplementary input from factorization
properties allowing to solve the equations in the commutative case is no longer
valid.Comment: 20 pages, 3 figures, references added, small clarifications adde
Intrinsic quark transverse momentum in the nucleon from lattice QCD
A better understanding of transverse momentum (k_T-) dependent quark
distributions in a hadron is needed to interpret several experimentally
observed large angular asymmetries and to clarify the fundamental role of gauge
links in non-abelian gauge theories. Based on manifestly non-local gauge
invariant quark operators we introduce process-independent k_T-distributions
and study their properties in lattice QCD. We find that the longitudinal and
transverse momentum dependence approximately factorizes, in contrast to the
behavior of generalized parton distributions. The resulting quark
k_T-probability densities for the nucleon show characteristic dipole
deformations due to correlations between intrinsic k_T and the quark or nucleon
spin. Our lattice calculations are based on N_f=2+1 mixed action propagators of
the LHP collaboration.Comment: 4 pages, 3 figure
Owner perceptions of their cat's quality of life when treated with a modified University of Wisconsin-Madison protocol for lymphoma
The objectives of this study were to assess owner perceptions of their cat’s quality of life during treatment for lymphoma with a doxorubicin-containing multi-agent chemotherapy protocol, whether various health-related parameters correlated with quality of life scores, and to assess owner satisfaction with the protocol
A lecture on the Liouville vertex operators
We reconsider the construction of exponential fields in the quantized
Liouville theory. It is based on a free-field construction of a continuous
family or chiral vertex operators. We derive the fusion and braid relations of
the chiral vertex operators. This allows us to simplify the verification of
locality and crossing symmetry of the exponential fields considerably. The
calculation of the matrix elements of the exponential fields leads to a
constructive derivation of the formula proposed by Dorn/Otto and the brothers
Zamolodchikov.Comment: Contribution to the proceedings of the 6th International Conference
on CFTs and Integrable Models, Chernogolovka, Russia, 2002 v2: Remarks added,
typos correcte
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