1,483 research outputs found
A characterization of non-archimedeanly quasimetrizable spaces
In this paper we introduce a new structure on topological spaces which allows us to give a characterization of non-archimedeanly quasipseudometrizable spaces
Transfinite order dimension
We give two different transfinite extensions of the covering dimension based on the Borst's order of certain families of boundaries of basic open sets. We compare them and we study their main properties
Dimension, inverse limits and GF-spaces
In this paper we characterize (covering) dimension in
metrizable spaces in terms of fractal structures. We will also
study dimension for compact metric spaces, giving a theorem relating dimension and a certain class of inverse limits, similar to
that of Freudenthal
Magnetization dynamics: path-integral formalism for the stochastic Landau-Lifshitz-Gilbert equation
We construct a path-integral representation of the generating functional for
the dissipative dynamics of a classical magnetic moment as described by the
stochastic generalization of the Landau-Lifshitz-Gilbert equation proposed by
Brown, with the possible addition of spin-torque terms. In the process of
constructing this functional in the Cartesian coordinate system, we critically
revisit this stochastic equation. We present it in a form that accommodates for
any discretization scheme thanks to the inclusion of a drift term. The
generalized equation ensures the conservation of the magnetization modulus and
the approach to the Gibbs-Boltzmann equilibrium in the absence of non-potential
and time-dependent forces. The drift term vanishes only if the mid-point
Stratonovich prescription is used. We next reset the problem in the more
natural spherical coordinate system. We show that the noise transforms
non-trivially to spherical coordinates acquiring a non-vanishing mean value in
this coordinate system, a fact that has been often overlooked in the
literature. We next construct the generating functional formalism in this
system of coordinates for any discretization prescription. The functional
formalism in Cartesian or spherical coordinates should serve as a starting
point to study different aspects of the out-of-equilibrium dynamics of magnets.
Extensions to colored noise, micro-magnetism and disordered problems are
straightforward.Comment: 47 pages + appendix, published versio
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Special Economic Zones, Global Value Chains, and the Degree of Economic Linkages in the Dominican Republic
The Dominican Republic is often considered an example of the successful implementation of Special Economic Zones (henceforth SEZs) in the Western hemisphere. The zones fueled economic growth during the 1980s and 1990s and, while they experienced a sharp decline in employment due in part to the expiry of the end of the Multi-Fiber Agreement and stronger international competition in the textile and apparel industry in 2005, signs of recovery have been observed since 2009. Surgical equipment, chemicals and plastics, and footwear have recently emerged as the new drivers of export dynamism in the zones (World Bank, 2015). The objective of this report is to inform the policy discussion around the developmental impact of SEZs in the Dominican Republic by empirically assessing i) the implications of regulatory reforms aimed at complying with WTO disciplines regarding the elimination of incentives conditioned on export performance for SEZs firms, ii) the extent to which SEZs participate in Global Value Chains, and iii) their linkages with domestic suppliers. The report is organized as follows: The second section presents the historical importance of SEZ as an engine of economic growth in the country. The third section depicts the structural shift in terms of production in SEZs and evaluates the degree of value addition taking place in the Dominican Republic. The fourth section evaluates the degree and evolution of linkages between SEZs and local firms. The fifth section shows the impact of the regulatory changes in the SEZ regimen undertaken to comply with WTO disciplines. Finally, some conclusions and policy recommendations are presented in section six
The backbone of the climate network
We propose a method to reconstruct and analyze a complex network from data
generated by a spatio-temporal dynamical system, relying on the nonlinear
mutual information of time series analysis and betweenness centrality of
complex network theory. We show, that this approach reveals a rich internal
structure in complex climate networks constructed from reanalysis and model
surface air temperature data. Our novel method uncovers peculiar wave-like
structures of high energy flow, that we relate to global surface ocean
currents. This points to a major role of the oceanic surface circulation in
coupling and stabilizing the global temperature field in the long term mean
(140 years for the model run and 60 years for reanalysis data). We find that
these results cannot be obtained using classical linear methods of multivariate
data analysis, and have ensured their robustness by intensive significance
testing.Comment: 6 pages, 5 figure
Tufa sedimentation in changing hydrological conditions: the River Mesa (Spain)
The processes controlling tufa deposition along the River Mesa (NE Spain) were studied from April 2003 to September 2009, based on six-monthly monitoring of physical and chemical parameters of the river water and sedimentological characteristics, including deposition rates on tablets. With a mean annual discharge around 1.5m3 /s, the sedimentation rate (mean 2mm/yr) recorded important spatial, seasonal and interannual variations. The river waters are of the calcium bicarbonate type. In this study, three distinct river stretches were distinguished based on the steady groundwater inputs, some of low-thermal nature. Groundwater discharges controlled the water chemical composition, and some sedimentation features too. At each stretch, an increase in pCO2 and conductivity was measured around the spring sites. Decreasing trends in conductivity or alkalinity with high enough saturation values with respect to calcite were only clearly observed in the intermediate stretch, which had higher tufa deposition rates than the other two. Tufa deposition rates were higher in cool (autumn+winter) than in warm (spring+summer) periods. In some low-rainfall warm periods, tufa deposition was inhibited or limited due to the low flow –mainly from groundwater inputs– and to the dryness of some river sites, which indeed favoured erosion during flooding. A decrease in yearly deposition rates from April 2006 onwards paralleled an important reduction in the river discharge. Groundwater inputs, drought periods and flood events should therefore be considered to understand fluvial tufa sedimentation in semi-arid conditions
Spectral Fizeau Interferometer applied to dental polymeric resins early shrinkage determination
In this work a variant of the well know Fiber Optic Fizeau Interferometer is presented. It is analyzed in the spectral domain and applied to the study of the shrinkage experienced by photocured polymeric resins. This approach, which maintains its main characteristics of being noninvasive and intrinsically self-calibrated, is sensitive to changes in the direction of evolution of the interferometric cavity length which is being measured. The Spectral Domain Fiber Optic Fizeau Interferometer generates typical response curves that must be processed in order to obtain the measurement related to the cavity length for every moment in time. The cavity is formed between the surface of the sample under test and the fiber optic tip itself. Besides, this sensor is used to determine whether or not exothermal effects from photocuring reactions affect the net shrinkage measured in the samples.Centro de Investigaciones ÓpticasFacultad de IngenierÃaConsejo Nacional de Investigaciones CientÃficas y Técnica
Spectral Fizeau Interferometer applied to dental polymeric resins early shrinkage determination
In this work a variant of the well know Fiber Optic Fizeau Interferometer is presented. It is analyzed in the spectral domain and applied to the study of the shrinkage experienced by photocured polymeric resins. This approach, which maintains its main characteristics of being noninvasive and intrinsically self-calibrated, is sensitive to changes in the direction of evolution of the interferometric cavity length which is being measured. The Spectral Domain Fiber Optic Fizeau Interferometer generates typical response curves that must be processed in order to obtain the measurement related to the cavity length for every moment in time. The cavity is formed between the surface of the sample under test and the fiber optic tip itself. Besides, this sensor is used to determine whether or not exothermal effects from photocuring reactions affect the net shrinkage measured in the samples.Centro de Investigaciones ÓpticasFacultad de IngenierÃaConsejo Nacional de Investigaciones CientÃficas y Técnica
Dynamical symmetries of Markov processes with multiplicative white noise
We analyse various properties of stochastic Markov processes with
multiplicative white noise. We take a single-variable problem as a simple
example, and we later extend the analysis to the Landau-Lifshitz-Gilbert
equation for the stochastic dynamics of a magnetic moment. In particular, we
focus on the non-equilibrium transfer of angular momentum to the magnetization
from a spin-polarised current of electrons, a technique which is widely used in
the context of spintronics to manipulate magnetic moments. We unveil two hidden
dynamical symmetries of the generating functionals of these Markovian
multiplicative white-noise processes. One symmetry only holds in equilibrium
and we use it to prove generic relations such as the fluctuation-dissipation
theorems. Out of equilibrium, we take profit of the symmetry-breaking terms to
prove fluctuation theorems. The other symmetry yields strong dynamical
relations between correlation and response functions which can notably simplify
the numerical analysis of these problems. Our construction allows us to clarify
some misconceptions on multiplicative white-noise stochastic processes that can
be found in the literature. In particular, we show that a first-order
differential equation with multiplicative white noise can be transformed into
an additive-noise equation, but that the latter keeps a non-trivial memory of
the discretisation prescription used to define the former.Comment: 44 page
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