7,070 research outputs found
Dynamic properties in a family of competitive growing models
The properties of a wide variety of growing models, generically called
, are studied by means of numerical simulations and analytic
developments. The study comprises the following models: Ballistic
Deposition, Random Deposition with Surface Relaxation, Das Sarma-Tamboronea,
Kim-Kosterlitz, Lai-Das Sarma, Wolf-Villain, Large Curvature, and three
additional models that are variants of the Ballistic Deposition model.
It is shown that after a growing regime, the interface width becomes
saturated at a crossover time () that, by fixing the sample size,
scales with according to , where
is an exponent. Also, the interface width at saturation () scales
as , where is another
exponent.
It is proved that, in any dimension, the exponents and obey the
following relationship: , where is
the growing exponent for . Furthermore, both exponents exhibit universality
in the limit.
By mapping the behaviour of the average height difference of two neighbouring
sites in discrete models of type and two kinds of random walks, we have
determined the exact value of the exponent .
Finally, by linking four well-established universality classes (namely
Edwards-Wilkinson, Kardar-Parisi-Zhang, Linear-MBE and Non-linear-MBE) with the
properties of both random walks, eight different stochastic equations for all
the competitive models studied are derived.Comment: 23 pages, 6 figures, Submitted to Phys. Rev.
Fold-Saddle Bifurcation in Non-Smooth Vector Fields on the Plane
This paper presents results concerning bifurcations of 2D piecewise-smooth
dynamical systems governed by vector fields. Generic three parameter families
of a class of Non-Smooth Vector Fields are studied and its bifurcation diagrams
are exhibited. Our main result describes the unfolding of the so called
Fold-Saddle singularity
Commuting multiparty quantum observables and local compatibility
A formula for the commutator of tensor product matrices is used to shows
that, for qubits, compatibility of quantum multiparty observables almost never
implies local compatibility at each site and to predict when this happens/does
not happen in a concise manner. In particular, it is shown that two ``fully
nontrivial'' -qubit observables are compatible locally and globally if and
only if they are equal up to sign. In addition, the formula gives insight into
the construction of new paradoxes of the type of the Kochen-Specker Theorem,
which can then be easily rephrased into proposals for new no hidden variable
experiments of the type of the ``Bell Theorem without inequalities''.Comment: 6 page
Spanning trees for the geometry and dynamics of compact polymers
Using a mapping of compact polymers on the Manhattan lattice to spanning
trees, we calculate exactly the average number of bends at infinite
temperature. We then find, in a high temperature approximation, the energy of
the system as a function of bending rigidity and polymer elasticity. We
identify the universal mechanism for the relaxation of compact polymers and
then endow the model with physically motivated dynamics in the convenient
framework of the trees. We find aging and domain coarsening after quenches in
temperature. We explain the slow dynamics in terms of the geometrical
interconnections between the energy and the dynamics.Comment: 10 pages, 8 figure
Brans-Dicke cylindrical wormholes
Static axisymmetric thin-shell wormholes are constructed within the framework
of the Brans-Dicke scalar-tensor theory of gravity. Examples of wormholes
associated with vacuum and electromagnetic fields are studied. All
constructions must be threaded by exotic matter, except in the case of
geometries with a singularity of finite radius, associated with an electric
field, which can have a throat supported by ordinary matter. These results are
achieved with any of the two definitions of the flare-out condition considered.Comment: 11 pages, 3 figures; v3: corrected version, conclusions unchange
Matter X waves
We predict that an ultra-cold Bose gas in an optical lattice can give rise to
a new form of condensation, namely matter X waves. These are non-spreading 3D
wave-packets which reflect the symmetry of the Laplacian with a negative
effective mass along the lattice direction, and are allowed to exist in the
absence of any trapping potential even in the limit of non-interacting atoms.
This result has also strong implications for optical propagation in periodic
structuresComment: 5 pages, 2 figure
Duality in linearized gravity
We show that duality transformations of linearized gravity in four
dimensions, i.e., rotations of the linearized Riemann tensor and its dual into
each other, can be extended to the dynamical fields of the theory so as to be
symmetries of the action and not just symmetries of the equations of motion.
Our approach relies on the introduction of two "superpotentials", one for the
spatial components of the spin-2 field and the other for their canonically
conjugate momenta. These superpotentials are two-index, symmetric tensors. They
can be taken to be the basic dynamical fields and appear locally in the action.
They are simply rotated into each other under duality. In terms of the
superpotentials, the canonical generator of duality rotations is found to have
a Chern-Simons like structure, as in the Maxwell case.Comment: 10 pages; introduction rewritten and references adde
Recent variations of Ghiacciaio del Calderone, Abruzzi, Italy
AbstractResults of a detailed topographic survey of Ghiacciaio del Calderone, Italy, the southernmost in Europe, are described and compared with those of surveys made in earlier years. Recession and thinning, much affected by micro-climate, have been the predominant state of health during the 20th century. Between 1916 and 1990, volume is estimated to have been reduced by about 90% and area by about 68%
Petrology and geochemistry of mafic and ultramafic cumulate rocks from the eastern part of the Sabzevar ophiolite (NE Iran): Implications for their petrogenesis and tectonic setting
The Late Cretaceous Sabzevar ophiolite represents one of the largest and most complete fragments of Tethyan oceanic lithosphere in the NE Iran. It is mainly composed of serpentinized mantle peridotites slices; nonetheless, minor tectonic slices of all crustal sequence constituents are observed in this ophiolite. The crustal sequence contains a well-developed ultramafic and mafic cumulates section, comprising plagioclase-bearing wehrlite, olivine clinopyroxenite, olivine gabbronorite, gabbronorite, amphibole gabbronorite and quartz gabbronorite with adcumulate, mesocumulate, heteradcumulate and orthocumulate textures. The crystallization order for these rocks is olivine ± chromian spinel → clinopyroxene → plagioclase → orthopyroxene → amphibole. The presence of primary magmatic amphiboles in the cumulate rocks shows that the parent magma evolved under hydrous conditions. Geochemically, the studied rock units are characterized by low TiO (0.18–0.57 wt.%), PO (<0.05 wt.%), KO (0.01–0.51 wt.%) and total alkali contents (0.12–3.04 wt.%). They indicate fractionated trends in the chondrite-normalized rare earth element (REE) plots and multi-element diagrams (spider diagrams). The general trend of the spider diagrams exhibit slight enrichment in large ion lithophile elements (LILEs) relative to high field strength elements (HFSEs) and positive anomalies in Sr, Pb and Eu and negative anomalies in Zr and Nb relative to the adjacent elements. The REE plots of these rocks display increasing trend from La to Sm, positive Eu anomaly (Eu/Eu∗ = 1.06–1.54) and an almost flat pattern from medium REE (MREE) to heavy REE (HREE) region [(Gd/Yb) = 1–1.17]. Moreover, clinopyroxenes from the cumulate rocks have low REE contents and show marked depletion in light REE (LREE) compared to MREE and HREE [(La/Sm) = 0.10–0.27 and (La/Yb) = 0.08–0.22]. The composition of calculated melts in equilibrium with the clinopyroxenes from less evolved cumulate samples are closely similar to island arc tholeiitic (IAT) magmas. Modal mineralogy, geochemical features and REE modeling indicate that Sabzevar cumulate rocks were formed by crystal accumulation from a hydrous depleted basaltic melt with IAT affinity. This melt has been produced by moderate to high degree (~15%) of partial melting a depleted mantle source, which partially underwent metasomatic enrichment from subducted slab components in an intra-oceanic arc setting.The authors thank the University of Isfahan (Isfahan, Iran) and the Instituto Andaluz de Ciencias de la Tierra (IACT, Granada, Spain) for their support in field work and sample preparation and for providing geochemical analyses facilities. We are grateful to Prof. Kristoffer Szilas, Prof. Tomo Morishita and two anonymous reviewers for their useful and constructive comments that improved the manuscript
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