5,470 research outputs found
A perturbative approach to J mixing in f-electron systems: Application to actinide dioxides
We present a perturbative model for crystal-field calculations, which keeps
into account the possible mixing of states labelled by different quantum number
J. Analytical J-mixing results are obtained for a Hamiltonian of cubic symmetry
and used to interpret published experimental data for actinide dioxides. A
unified picture for all the considered compounds is proposed by taking into
account the scaling properties of the crystal-field potential.Comment: 16 pages + 4 figures; will appear http://prb.aps.or
Low mass dimuons within a hybrid approach
We analyse dilepton emission from hot and dense hadronic matter using a
hybrid approach based on the Ultrarelativistic Quantum Molecular Dynamics
(UrQMD) transport model with an intermediate hydrodynamic stage for the
description of heavy-ion collisions at relativistic energies. Focusing on the
enhancement with respect to the contribution from long-lived hadron decays
after freeze-out observed at the SPS in the low mass region of the dilepton
spectra (often referred to as "the excess"), the relative importance of the
emission from the equilibrium and the non-equilibrium stages is discussed.Comment: Proceedings of Hot Quarks 2010, 21-26 June 2010 Las Londe Les Maures;
v2: Corrected typos and added a commen
Resonant x-ray scattering spectra from multipole orderings: Np M_{4,5} edges in NpO2
We study resonant x-ray scattering (RXS) at Np M_{4,5} edges in the
triple-\textbf{k} multipole ordering phase in NpO_{2}, on the basis of a
localized electron model. We derive an expression for RXS amplitudes to
characterize the spectra under the assumption that a rotational invariance is
preserved in the intermediate state of scattering process. This assumption is
justified by the fact that energies of the crystal electric field and the
intersite interaction is smaller than the energy of multiplet structures. This
expression is found useful to calculate energy profiles with taking account of
the intra-Coulomb and spin-orbit interactions. Assuming the \Gamma_{8}-quartet
ground state, we construct the triple-\textbf{k} ground state, and analyze the
RXS spectra. The energy profiles are calculated in good agreement with the
experiment, providing a sound basis to previous phenomenological analyses.Comment: 10 pages, 7 figure
Integrable lattices and their sublattices II. From the B-quadrilateral lattice to the self-adjoint schemes on the triangular and the honeycomb lattices
An integrable self-adjoint 7-point scheme on the triangular lattice and an
integrable self-adjoint scheme on the honeycomb lattice are studied using the
sublattice approach. The star-triangle relation between these systems is
introduced, and the Darboux transformations for both linear problems from the
Moutard transformation of the B-(Moutard) quadrilateral lattice are obtained. A
geometric interpretation of the Laplace transformations of the self-adjoint
7-point scheme is given and the corresponding novel integrable discrete 3D
system is constructed.Comment: 15 pages, 6 figures; references added, some typos correcte
Might EPR particles communicate through a wormhole?
We consider the two-particle wave function of an Einstein-Podolsky-Rosen
system, given by a two dimensional relativistic scalar field model. The Bohm-de
Broglie interpretation is applied and the quantum potential is viewed as
modifying the Minkowski geometry. In this way an effective metric, which is
analogous to a black hole metric in some limited region, is obtained in one
case and a particular metric with singularities appears in the other case,
opening the possibility, following Holland, of interpreting the EPR
correlations as being originated by an effective wormhole geometry, through
which the physical signals can propagate.Comment: Corrected version, to appears in EP
Invariant Form of Hyperfine Interaction with Multipolar Moments - Observation of Octupolar Moments in NpO and CeB by NMR -
The invariant form of the hyperfine interaction between multipolar moments
and the nuclear spin is derived, and applied to discuss possibilities to
identify the antiferro-octupolar (AFO) moments by NMR experiments. The ordered
phase of NpO and the phase IV of CeLaB are studied in
detail. Recent O NMR for polycrystalline samples of NpO are
discussed theoretically from our formulation. The observed feature of the
splitting of O NMR spectrum into a sharp line and a broad line, their
intensity ratio, and the magnetic field dependence of the shift and of the
width can be consistently explained on the basis of the triple \bq AFO
ordering model proposed by Paix\~{a}o {\it et. al.} Thus, the present theory
shows that the O NMR spectrum gives a strong support to the model. The 4
O sites in the fcc NpO become inequivalent due to the secondary triple
\bq ordering of AF-quadrupoles: one cubic and three non-cubic sites. It turns
out that the hyperfine field due to the antiferro-dipole and AFO moments
induced by the magnetic field, and the quadrupolar field at non-cubic sites are
key ingredients to understand the observed spectrum. The controversial problem
of the nature of phase IV in CeLaB is also studied. It is
pointed out that there is a unique feature in the NMR spectra, if the
() AFO ordering is
realized in CeLaB. Namely, the hyperfine splitting of a B
atom pair on the sites crosses zero on the
plane when the magnetic field is rotated around the axis.Comment: 22 pages, 2 figure
Partially integrable systems in multidimensions by a variant of the dressing method. 1
In this paper we construct nonlinear partial differential equations in more
than 3 independent variables, possessing a manifold of analytic solutions with
high, but not full, dimensionality. For this reason we call them ``partially
integrable''. Such a construction is achieved using a suitable modification of
the classical dressing scheme, consisting in assuming that the kernel of the
basic integral operator of the dressing formalism be nontrivial. This new
hypothesis leads to the construction of: 1) a linear system of compatible
spectral problems for the solution of the integral equation in 3
independent variables each (while the usual dressing method generates spectral
problems in 1 or 2 dimensions); 2) a system of nonlinear partial differential
equations in dimensions (), possessing a manifold of analytic
solutions of dimension (), which includes one largely arbitrary relation
among the fields. These nonlinear equations can also contain an arbitrary
forcing.Comment: 21 page
The Number of Convex Permutominoes
Permutominoes are polyominoes defined by suitable pairs of permutations. In this paper we provide a formula to count the number of convex permutominoes of given perimeter. To this aim we define the transform of a generic pair of permutations, we characterize the transform of any pair defining a convex permutomino, and we solve the counting problem in the transformed space
Non-Linear Evolution Equations with Non-Analytic Dispersion Relations in 2+1 Dimensions. Bilocal Approach
A method is proposed of obtaining (2+1)-dimensional non- linear equations
with non-analytic dispersion relations. Bilocal formalism is shown to make it
possible to represent these equations in a form close to that for their
counterparts in 1+1 dimensions.Comment: 13 pages, to be published in J. Phys.
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