13,170 research outputs found
Endogenous space in the Net era
Libre Software communities are among the most interesting and advanced socio-economic laboratories on the Net. In terms of directions of Regional Science research, this paper addresses a simple question: “Is the socio-economics of digital nets out of scope for Regional Science, or might the latter expand to a cybergeography of digitally enhanced territories ?” As for most simple questions, answers are neither so obvious nor easy. The authors start drafting one in a positive sense, focussing upon a file rouge running across the paper: endogenous spaces woven by socio-economic processes. The drafted answer declines on an Evolutionary Location Theory formulation, together with two computational modelling views. Keywords: Complex networks, Computational modelling, Economics of Internet, Endogenous spaces, Evolutionary location theory, Free or Libre Software, Path dependence, Positionality.
Putting Theories of the Firm in Their Place: A Supplemental Digest of the New Institutional Economics
Institutional and Behavioral Economics,
Crossed Andreev reflection-induced magnetoresistance
We show that very large negative magnetoresistance can be obtained in
magnetic trilayers in a current-in-plane geometry owing to the existence of
crossed Andreev reflection. This spin-valve consists of a thin superconducting
film sandwiched between two ferromagnetic layers whose magnetization is allowed
to be either parallelly or antiparallelly aligned. For a suitable choice of
structure parameters and nearly fully spin-polarized ferromagnets the
magnetoresistance can exceed -80%. Our results are relevant for the design and
implementation of spintronic devices exploiting ferromagnet-superconductor
structures.Comment: 5 pages, 4 figures, final published versio
SOM-based Data Analysis of Speculative Attacks' Real Effects
In some cases, currency crises are followed by strong recessions (e.g., recent Asian and Argentinean crises), but in other cases they are not. This paper uses Self-Organizing Maps (SOM) to search for meaningful associations between speculative attacks' real effects and 28 variables that characterize the economic, financial, legal, and socio-political structure of the country at the onset of the attack. SOM is a neural network-based generalization of Principal Component Analysis (PCA) that provides an efficient non-linear projection of the multidimensional data space on a curved surface. This paper finds a strong association of speculative attacks' real effects with fundamentals and the banking sector structureexploratory data analysis, self-organizing maps, neural networks, speculative attacks' real effects
Hybrid collocation perturbation for PDEs with random domains
In this work we consider the problem of approximating the statistics of a
given Quantity of Interest (QoI) that depends on the solution of a linear
elliptic PDE defined over a random domain parameterized by random
variables. The random domain is split into large and small variations
contributions. The large variations are approximated by applying a sparse grid
stochastic collocation method. The small variations are approximated with a
stochastic collocation-perturbation method. Convergence rates for the variance
of the QoI are derived and compared to those obtained in numerical experiments.
Our approach significantly reduces the dimensionality of the stochastic
problem. The computational cost of this method increases at most quadratically
with respect to the number of dimensions of the small variations. Moreover, for
the case that the small and large variations are independent the cost increases
linearly
Monte Carlo studies of the properties of the Majorana quantum error correction code: is self-correction possible during braiding?
The Majorana code is an example of a stabilizer code where the quantum
information is stored in a system supporting well-separated Majorana Bound
States (MBSs). We focus on one-dimensional realizations of the Majorana code,
as well as networks of such structures, and investigate their lifetime when
coupled to a parity-preserving thermal environment. We apply the Davies
prescription, a standard method that describes the basic aspects of a thermal
environment, and derive a master equation in the Born-Markov limit. We first
focus on a single wire with immobile MBSs and perform error correction to
annihilate thermal excitations. In the high-temperature limit, we show both
analytically and numerically that the lifetime of the Majorana qubit grows
logarithmically with the size of the wire. We then study a trijunction with
four MBSs when braiding is executed. We study the occurrence of dangerous error
processes that prevent the lifetime of the Majorana code from growing with the
size of the trijunction. The origin of the dangerous processes is the braiding
itself, which separates pairs of excitations and renders the noise nonlocal;
these processes arise from the basic constraints of moving MBSs in 1D
structures. We confirm our predictions with Monte Carlo simulations in the
low-temperature regime, i.e. the regime of practical relevance. Our results put
a restriction on the degree of self-correction of this particular 1D
topological quantum computing architecture.Comment: Main text: 20 pages, Supplementary Material: 66 pages. Short version:
arXiv:1505.0371
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