9,365 research outputs found
On Integrable Quantum Group Invariant Antiferromagnets
A new open spin chain hamiltonian is introduced. It is both integrable
(Sklyanin`s type matrices are used to achieve this) and invariant under
transformations in nilpotent irreps for
. Some considerations on the centralizer of nilpotent
representations and its representation theory are also presented.Comment: IFF-5/92, 13 pages, LaTex file, 8 figures available from author
Effects of electron inertia in collisionless magnetic reconnection
We present a study of collisionless magnetic reconnection within the
framework of full two-fluid MHD for a completely ionized hydrogen plasma,
retaining the effects of the Hall current, electron pressure and electron
inertia. We performed 2.5D simulations using a pseudo-spectral code with no
dissipative effects. We check that the ideal invariants of the problem are
conserved down to round-off errors. Our results show that the change in the
topology of the magnetic field lines is exclusively due to the presence of
electron inertia. The computed reconnection rates remain a fair fraction of the
Alfv\'en velocity, which therefore qualifies as fast reconnection
DeltaImpactFinder: Assessing Semantic Merge Conflicts with Dependency Analysis
In software development, version control systems (VCS) provide branching and
merging support tools. Such tools are popular among developers to concurrently
change a code-base in separate lines and reconcile their changes automatically
afterwards. However, two changes that are correct independently can introduce
bugs when merged together. We call semantic merge conflicts this kind of bugs.
Change impact analysis (CIA) aims at estimating the effects of a change in a
codebase. In this paper, we propose to detect semantic merge conflicts using
CIA. On a merge, DELTAIMPACTFINDER analyzes and compares the impact of a change
in its origin and destination branches. We call the difference between these
two impacts the delta-impact. If the delta-impact is empty, then there is no
indicator of a semantic merge conflict and the merge can continue
automatically. Otherwise, the delta-impact contains what are the sources of
possible conflicts.Comment: International Workshop on Smalltalk Technologies 2015, Jul 2015,
Brescia, Ital
Chirality in charge-transfer salts of BEDT-TTF of tris(oxalato)chromate(III)
Crystallisation from chiral electrolyte (R)-(−)-carvone has produced three new chiral semiconducting salts of BEDT-TTF from racemic anion tri(oxalato)chromate(III)
Shocks near Jamming
Non-linear sound is an extreme phenomenon typically observed in solids after
violent explosions. But granular media are different. Right when they jam,
these fragile and disordered solids exhibit a vanishing rigidity and sound
speed, so that even tiny mechanical perturbations form supersonic shocks. Here,
we perform simulations in which two-dimensional jammed granular packings are
dynamically compressed, and demonstrate that the elementary excitations are
strongly non-linear shocks, rather than ordinary phonons. We capture the full
dependence of the shock speed on pressure and impact intensity by a
surprisingly simple analytical model.Comment: Revised version. Accepted for publication in Phys. Rev. Let
On the Abundance of Circumbinary Planets
We present here the first observationally based determination of the rate of
occurrence of circumbinary planets. This is derived from the publicly available
Kepler data, using an automated search algorithm and debiasing process to
produce occurrence rates implied by the seven systems already known. These
rates depend critically on the planetary inclination distribution: if
circumbinary planets are preferentially coplanar with their host binaries, as
has been suggested, then the rate of occurrence of planets with
orbiting with \ d is \% (95\% confidence limits),
higher than but consistent with single star rates. If on the other hand the
underlying planetary inclination distribution is isotropic, then this
occurrence rate rises dramatically, to give a lower limit of 47\%. This implies
that formation and subsequent dynamical evolution in circumbinary disks must
either lead to largely coplanar planets, or proceed with significantly greater
ease than in circumstellar disks. As a result of this investigation we also
show that giant planets () are significantly less common in
circumbinary orbits than their smaller siblings, and confirm that the proposed
shortfall of circumbinary planets orbiting the shorter period binaries in the
Kepler sample is a real effect.Comment: Accepted for publication in MNRAS (1st August 2014). 12 pages. Update
to match final version, including clarifications and new figures. Results are
unchange
Valoración económica del ecosistema del Arroyo Alamar en la ciudad de Tijuana
El mundo emprende proyectos para rescatar escurrimientos pluviales, algunos se han convertido en espacios icónicos y de atracción, sin embargo, en México se sigue considerando la "urbanización" sin límites como señal de progreso e impulsando proyectos de ingeniería hidráulica tradicional para abordar problemas de inundaciones, contaminación y demanda de espacio. Es el caso del proyecto del arroyo Alamar en Tijuana B.C. En ese sentido el objetivo del trabajo es la valoración económica de la perdida ambiental que supone la construcción del referido proyecto, ésta se efectúa en parte con base a la propuesta de De la Lanza y colaboradores (2013); la cual sesustenta teórica y metodológicamente en el concepto y clasificación de los Servicios Ecológicos (SE) propuestos por el grupo de evaluación de ecosistemas del milenio (Millennium Ecosystem Assessment) en 2005. Los resultados señalan una pérdida monetaria anual de 2 335 124.96 dólares americanos, a al que habría que sumar no solo la ambiental si no también la "social" o urbana.World undertakes projects to rescue rain runoff, some have become iconic spaces and attraction, however, Mexico is follows considering the "urbanization" without limits as a sign of progress and promoting traditional hydraulic engineering projects to address problems of flooding, pollution and demand for space. It is the case of the project of the Alamar brook in Tijuana B.C. In this sense the objective of the work is the economic valuation of environmental loss posed by the construction of the concerned project, this is done in part based on the proposal of the De la Lanza and collaborators (2013); which is sustained theoretically and methodologically on the concept and classification of ecological services (SE) proposed by the Group of the Millennium Ecosystem Assessment (MEA) in 2005. Theresults indicate an annual monetary loss of 2 335 124.96 dollars, to which should be added not only the environmental if not also a social or urban
Coherent carrier dynamics in semiconductor superlattices
We investigate the coherent dynamics of carriers in semiconductor
superlattices driven by ac-dc electric fields. We solve numerically the
time-dependent effective-mass equation for the envelope function. We find that
carriers undergo Rabi oscillations when the driving frequency is close to the
separation between minibands.Comment: REVTEX (6 pages) and 3 figures (PostScript). Accepted in Physics
Letters
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