2,424 research outputs found
Numerical study of the hard-core Bose-Hubbard Model on an Infinite Square Lattice
We present a study of the hard-core Bose-Hubbard model at zero temperature on
an infinite square lattice using the infinite Projected Entangled Pair State
algorithm [Jordan et al., Phys. Rev. Lett. 101, 250602 (2008)]. Throughout the
whole phase diagram our values for the ground state energy, particle density
and condensate fraction accurately reproduce those previously obtained by other
methods. We also explore ground state entanglement, compute two-point
correlators and conduct a fidelity-based analysis of the phase diagram.
Furthermore, for illustrative purposes we simulate the response of the system
when a perturbation is suddenly added to the Hamiltonian.Comment: 8 pages, 6 figure
Multi-GPU maximum entropy image synthesis for radio astronomy
The maximum entropy method (MEM) is a well known deconvolution technique in
radio-interferometry. This method solves a non-linear optimization problem with
an entropy regularization term. Other heuristics such as CLEAN are faster but
highly user dependent. Nevertheless, MEM has the following advantages: it is
unsupervised, it has a statistical basis, it has a better resolution and better
image quality under certain conditions. This work presents a high performance
GPU version of non-gridding MEM, which is tested using real and simulated data.
We propose a single-GPU and a multi-GPU implementation for single and
multi-spectral data, respectively. We also make use of the Peer-to-Peer and
Unified Virtual Addressing features of newer GPUs which allows to exploit
transparently and efficiently multiple GPUs. Several ALMA data sets are used to
demonstrate the effectiveness in imaging and to evaluate GPU performance. The
results show that a speedup from 1000 to 5000 times faster than a sequential
version can be achieved, depending on data and image size. This allows to
reconstruct the HD142527 CO(6-5) short baseline data set in 2.1 minutes,
instead of 2.5 days that takes a sequential version on CPU.Comment: 11 pages, 13 figure
Energetics and dynamics of H adsorbed in a nanoporous material at low temperature
Molecular hydrogen adsorption in a nanoporous metal organic framework
structure (MOF-74) was studied via van der Waals density-functional
calculations. The primary and secondary binding sites for H were confirmed.
The low-lying rotational and translational energy levels were calculated, based
on the orientation and position dependent potential energy surface at the two
binding sites. A consistent picture is obtained between the calculated
rotational-translational transitions for different H loadings and those
measured by inelastic neutron scattering exciting the singlet to triplet (para
to ortho) transition in H. The H binding energy after zero point energy
correction due to the rotational and translational motions is predicted to be
100 meV in good agreement with the experimental value of 90 meV.Comment: 5 pagers, 4 figures. added reference
Precompilation: an alternative approach to provide native generic programming support in C++
In C++, Generative Programming (GP) techniques are being used to generate highly customized and optimized products automatically manufactured at compile-time; to provide these functionalities increasing compiling power is required.
This work presents an improved compilation model for C++ by adding the ‘precompilation’ phase, leading beyond the Template Meta Programming technique to produce constants and conditional code.
Procedural, object-oriented and all the remaining language features become available to produce constants, instances, and compiletime checks, opening, at the same time, a new way for metadata types treatment. In addition to that, when compiling for embedded platforms, some calculi may be moved from resource-critical run time to compile time, taking advantage of the processing power of the host platform. A tool named PRECOMP C++ is also presented in this work as a precompilationenabled C++ extension that supports GP in standard C++ execution during compile time, providing the ability to run metaprograms that operate with more complex data types and features than those supported in Template Meta Programming, such as floating point, pointers arithmetic, inclusion polymorphism, and dynamic memoryII Workshop de Ingeniería de Software y Bases de Datos (WISBD)Red de Universidades con Carreras en Informática (RedUNCI
¿Existe alguna relación entre la capacidad de movimiento funcional y el estado ponderal? Un estudio en escolares españoles
Indexación: Scopus.Background: to examine relations between functional movement patterns and weight status in Spanish primary school children and to determine the differences between sexes. Methods: three hundred and thirty-three, 6-13 years old children (164 boys and 169 girls), participated in this study. The main outcome measures were the body mass index (BMI) and the Functional Movement Screen™ (FMS). Children were classified as normal weight (NW), overweight (OV) or obese (OB) according to international cut-offs. Results: total FMS score was negatively correlated with BMI (p < 0.001). FMS score was different between children from NW, OV and OB groups (p = 0.001), lower with the increased BMI (p < 0.001 between all groups). Significant differences (p < 0.05) between NW, OV and OB were found in deep squat, hurdle step, in-line lunge, shoulder mobility, straight leg-raise and push-up tests. As for the sex differences, girls obtained higher scores (p < 0.05) in in-line lunge, shoulder mobility and straight leg-raise, whereas boys did it in push-up (p = 0.044) test. Conclusions: these results confirm that total FMS score significantly and inversely correlates with BMI in a group of 333 school-age children. As for the sex differences, girls outperform boys in movements requiring flexibility and balance, whilst boys outperform girls in tests where muscular strength is required. © 2018 SENPE and Arán Ediciones S.L.Introducción: examinar la relación entre los patrones de movimiento funcional y el estado ponderal en escolares españoles, determinando
también la infl uencia de la variable sexo.
Métodos: trescientos treinta y tres niños de 6-13 años de edad (164 niños y 169 niñas), participaron voluntariamente en este estudio. Las
variables objeto de estudio fueron el índice de masa corporal (IMC) y la batería de test Functional Movement ScreenTM (FMS). Los niños fueron
clasifi cados como normopeso (NW), sobrepeso (OV) y obesos (OB) de acuerdo con los puntos de corte internacionales.
Resultados: la puntuación total en el FMS correlacionó de forma negativa y signifi cativa con el IMC (p < 0,001). La puntuación en FMS fue
diferente entre las categorías de peso (p = 0,001), hallando un peor rendimiento en FMS conforme aumenta el IMC (p < 0,001 entre todos los
grupos). Se hallaron diferencias signifi cativas (p < 0,05) entre NW, OV y OB en los test de deep squat, hurdle step, in-line lunge, shoulder mobility,
straight leg-raise and push-up. En cuanto a las diferencias por sexo, las chicas obtuvieron puntuaciones más altas en FMS (p < 0,05) en los test
in-line lunge, shoulder mobility and straight leg-raise; mientras los chicos obtuvieron puntuaciones superiores en el test de push-up (p = 0,044).
Conclusiones: los resultados confi rman que la puntuación total en el FMS correlaciona signifi cativa y negativamente con el IMC en este grupo
de 333 escolares. En cuanto a la infl uencia del sexo, las chicas obtuvieron mayor puntuación que los chicos en los test que requerían fl exibilidad
y equilibrio, mientras los chicos fueron superiores en los test en los que predominaba la fuerza muscular.https://www.nutricionhospitalaria.org/index.php/articles/01670/show#
Multivector Fields and Connections. Setting Lagrangian Equations in Field Theories
The integrability of multivector fields in a differentiable manifold is
studied. Then, given a jet bundle , it is shown that integrable
multivector fields in are equivalent to integrable connections in the
bundle (that is, integrable jet fields in ). This result is
applied to the particular case of multivector fields in the manifold and
connections in the bundle (that is, jet fields in the repeated jet
bundle ), in order to characterize integrable multivector fields and
connections whose integral manifolds are canonical lifting of sections. These
results allow us to set the Lagrangian evolution equations for first-order
classical field theories in three equivalent geometrical ways (in a form
similar to that in which the Lagrangian dynamical equations of non-autonomous
mechanical systems are usually given). Then, using multivector fields; we
discuss several aspects of these evolution equations (both for the regular and
singular cases); namely: the existence and non-uniqueness of solutions, the
integrability problem and Noether's theorem; giving insights into the
differences between mechanics and field theories.Comment: New sections on integrability of Multivector Fields and applications
to Field Theory (including some examples) are added. The title has been
slightly modified. To be published in J. Math. Phy
Structural aspects of Hamilton-Jacobi theory
In our previous papers [11,13] we showed that the Hamilton-Jacobi problem can
be regarded as a way to describe a given dynamics on a phase space manifold in
terms of a family of dynamics on a lower-dimensional manifold. We also showed
how constants of the motion help to solve the Hamilton-Jacobi equation. Here we
want to delve into this interpretation by considering the most general case: a
dynamical system on a manifold that is described in terms of a family of
dynamics (`slicing vector fields') on lower-dimensional manifolds. We identify
the relevant geometric structures that lead from this decomposition of the
dynamics to the classical Hamilton-Jacobi theory, by considering special cases
like fibred manifolds and Hamiltonian dynamics, in the symplectic framework and
the Poisson one. We also show how a set of functions on a tangent bundle can
determine a second-order dynamics for which they are constants of the motion.Comment: 26 pages. Minor changes (some minor mistakes are corrected
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