4,852 research outputs found
Matrix-Valued Little q-Jacobi Polynomials
Matrix-valued analogues of the little q-Jacobi polynomials are introduced and
studied. For the 2x2-matrix-valued little q-Jacobi polynomials explicit
expressions for the orthogonality relations, Rodrigues formula, three-term
recurrence relation and their relation to matrix-valued q-hypergeometric series
and the scalar-valued little q-Jacobi polynomials are presented. The study is
based on a matrix-valued q-difference operator, which is a q-analogue of
Tirao's matrix-valued hypergeometric differential operator.Comment: 16 pages, various corrections and minor additions, incorporating
referee's comment
Factorization and Criticality in Finite XXZ Systems of Arbitrary Spin
We analyze ground state (GS) factorization in general arrays of spins si with XXZ couplings immersed in nonuniform fields. It is shown that an exceptionally degenerate set of completely separable symmetry-breaking GSs can arise for a wide range of field configurations, at a quantum critical point where all GS magnetization plateaus merge. Such configurations include alternating fields as well as zero-bulk field solutions with edge fields only and intermediate solutions with zero field at specific sites, valid for d-dimensional arrays. The definite magnetization-projected GSs at factorization can be analytically determined and depend only on the exchange anisotropies, exhibiting critical entanglement properties. We also show that some factorization-compatible field configurations may result in field-induced frustration and nontrivial behavior at strong fields.Fil: Cerezo, M. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Rossignoli, Raúl Dante. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Canosa, Norma Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Ríos, E.. Universidad Tecnológica Nacional; Argentin
Continuum variational and diffusion quantum Monte Carlo calculations
This topical review describes the methodology of continuum variational and
diffusion quantum Monte Carlo calculations. These stochastic methods are based
on many-body wave functions and are capable of achieving very high accuracy.
The algorithms are intrinsically parallel and well-suited to petascale
computers, and the computational cost scales as a polynomial of the number of
particles. A guide to the systems and topics which have been investigated using
these methods is given. The bulk of the article is devoted to an overview of
the basic quantum Monte Carlo methods, the forms and optimisation of wave
functions, performing calculations within periodic boundary conditions, using
pseudopotentials, excited-state calculations, sources of calculational
inaccuracy, and calculating energy differences and forces
Epidemiology of sports injuries in european union countries
La práctica deportiva es una actividad que se recomienda para mantener y promocionar la salud y los buenos hábitos. Sin embargo puede acarrear un riesgo importante de lesiones. Este estudio presenta, mediante técnicas de análisis multivariante, la relación que existe entre la tipo de lesiones, lugares del cuerpo donde se producen, los deportes más populares; fútbol, baloncesto, voleibol, y gimnasia, edad y países donde se practica, tomando datos de cinco países de la Unión Europea. Si relacionamos estas características entre sí, podemos elaborar estrategias específicas al tipo de deporte y país donde se practica, con el objeto de mejorar la prevención y poder disminuir la cantidad de lesiones que se producen.Participation in sports is a health promotion activity and maintains good habits that entail an important injury risk. The present article is a study using Multivariatye Analysis, the relationship between type of injury, location of injury, the most popular sports; soccer, basketball, volleyball, gymnastics, county where it has been practiced and age, in five European Union countries. With these relationships, we can develop specific strategies to improve prevention and to reduce the injuries that occur
Energetics of intrinsic point defects in ZrSiO
Using first principles calculations we have studied the formation energies,
electron and hole affinities, and electronic levels of intrinsic point defects
in zircon. The atomic structures of charged interstitials, vacancies, Frenkel
pairs and anti-site defects are obtained. The limit of high concentration of
point defects, relevant for the use of this material in nuclear waste
immobilization, was studied with a variable lattice relaxation that can
simulate the swelling induced by radiation damage. The limit of low
concentration of defects is simulated with larger cells and fixed lattice
parameters. Using known band offset values at the interface of zircon with
silicon, we analyze the foreseeable effect of the defects on the electronic
properties of zircon used as gate in metal-oxide-semiconductor devices.Comment: preprint 16 pages, 4 figures, and 5 table
Trajectory-dependent energy loss for swift He atoms axially scattered off a silver surface
Angle- and energy-loss- resolved distributions of helium atoms grazingly
scattered from a Ag(110) surface along low indexed crystallographic directions
are investigated considering impact energies in the few keV range. Final
projectile distributions are evaluated within a semi-classical formalism that
includes dissipative effects due to electron-hole excitations through a
friction force. For mono-energetic beams impinging along the ,
and directions, the model predicts the presence of
multiple peak structures in energy-loss spectra. Such structures provide
detailed information about the trajectory-dependent energy loss. However, when
the experimental dispersion of the incident beam is taken into account, these
energy-loss peaks are completely washed out, giving rise to a smooth
energy-loss distribution, in fairly good agreement with available experimental
data
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