22,588 research outputs found
The Notion of Person: a Reappraisal from the Side of Human Rights
My aim here is to defend the plausibility of
identifying the subject of human rights through the concept
of "moral person", by reflecting on the inherent connection
between the concept of person and that of human rights in
their moral dimension, that is in the light of an "ethics" of
human rights, an ethics in which human rights represent
the fundamental moral values
Spatiotemporal correlations of earthquakes in the continuum limit of the one-dimensional Burridge-Knopoff model
Spatiotemporal correlations of the one-dimensional spring-block
(Burridge-Knopoff) model of earthquakes, either with or without the viscosity
term, are studied by means of numerical computer simulations. The continuum
limit of the model is examined by systematically investigating the model
properties with varying the block-size parameter a toward a\to 0. The Kelvin
viscosity term is introduced so that the model dynamics possesses a sensible
continuum limit. In the presence of the viscosity term, many of the properties
of the original discrete BK model are kept qualitatively unchanged even in the
continuum limit, although the size of minimum earthquake gets smaller as a gets
smaller. One notable exception is the existence/non-existence of the
doughnut-like quiescence prior to the mainshock. Although large events of the
original discrete BK model accompany seismic acceleration together with a
doughnut-like quiescence just before the mainshock, the spatial range of the
doughnut-like quiescence becomes narrower as a gets smaller, and in the
continuum limit, the doughnut-like quiescence might vanish altogether. The
doughnut-like quiescence observed in the discrete BK model is then a phenomenon
closely related to the short-length cut-off scale of the model
AdS/dCFT one-point functions of the SU(3) sector
We propose a closed formula for the tree-level one-point functions of
non-protected operators belonging to an SU(3) sub-sector of the defect CFT dual
to the D3-D5 probe brane system with background gauge field flux, k, valid for
k=2. The formula passes a number of non-trivial analytical and numerical tests.
Our proposal is based on expressing the one-point functions as an overlap
between a Bethe eigenstate of the SU(3) spin chain and a certain matrix product
state, deriving various factorization properties of the Gaudin norm and
performing explicit computations for shorter spin chains. As its SU(2)
counterpart, the one-point function formula for the SU(3) sub-sector is of
determinant type. We discuss the the differences with the SU(2) case and the
challenges in extending the present formula beyond k=2.Comment: 6 page
The planar spectrum in U(N)-invariant quantum mechanics by Fock space methods: I. The bosonic case
Prompted by recent results on Susy-U(N)-invariant quantum mechanics in the
large N limit by Veneziano and Wosiek, we have examined the planar spectrum in
the full Hilbert space of U(N)-invariant states built on the Fock vacuum by
applying any U(N)-invariant combinations of creation-operators. We present
results about 1) the supersymmetric model in the bosonic sector, 2) the
standard quartic Hamiltonian. This latter is useful to check our techniques
against the exact result of Brezin et al. The SuSy case is where Fock space
methods prove to be the most efficient: it turns out that the problem is
separable and the exact planar spectrum can be expressed in terms of the
single-trace spectrum. In the case of the anharmonic oscillator, on the other
hand, the Fock space analysis is quite cumbersome due to the presence of large
off-diagonal O(N) terms coupling subspaces with different number of traces;
these terms should be absorbed before taking the planar limit and recovering
the known planar spectrum. We give analytical and numerical evidence that good
qualitative information on the spectrum can be obtained this way.Comment: 17 pages, 4 figures, uses youngtab.sty. Final versio
Uniform sampling of steady states in metabolic networks: heterogeneous scales and rounding
The uniform sampling of convex polytopes is an interesting computational
problem with many applications in inference from linear constraints, but the
performances of sampling algorithms can be affected by ill-conditioning. This
is the case of inferring the feasible steady states in models of metabolic
networks, since they can show heterogeneous time scales . In this work we focus
on rounding procedures based on building an ellipsoid that closely matches the
sampling space, that can be used to define an efficient hit-and-run (HR) Markov
Chain Monte Carlo. In this way the uniformity of the sampling of the convex
space of interest is rigorously guaranteed, at odds with non markovian methods.
We analyze and compare three rounding methods in order to sample the feasible
steady states of metabolic networks of three models of growing size up to
genomic scale. The first is based on principal component analysis (PCA), the
second on linear programming (LP) and finally we employ the lovasz ellipsoid
method (LEM). Our results show that a rounding procedure is mandatory for the
application of the HR in these inference problem and suggest that a combination
of LEM or LP with a subsequent PCA perform the best. We finally compare the
distributions of the HR with that of two heuristics based on the Artificially
Centered hit-and-run (ACHR), gpSampler and optGpSampler. They show a good
agreement with the results of the HR for the small network, while on genome
scale models present inconsistencies.Comment: Replacement with major revision
Custo de produção de trigo e de aveia: estimativa para a safra 2004.
bitstream/CNPT-2010/40482/1/p-co117.pd
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