1,633 research outputs found
Silent MST approximation for tiny memory
In network distributed computing, minimum spanning tree (MST) is one of the
key problems, and silent self-stabilization one of the most demanding
fault-tolerance properties. For this problem and this model, a polynomial-time
algorithm with memory is known for the state model. This is
memory optimal for weights in the classic range (where
is the size of the network). In this paper, we go below this
memory, using approximation and parametrized complexity.
More specifically, our contributions are two-fold. We introduce a second
parameter~, which is the space needed to encode a weight, and we design a
silent polynomial-time self-stabilizing algorithm, with space . In turn, this allows us to get an approximation algorithm for the problem,
with a trade-off between the approximation ratio of the solution and the space
used. For polynomial weights, this trade-off goes smoothly from memory for an -approximation, to memory for exact solutions,
with for example memory for a 2-approximation
Structure of Pion Photoproduction Amplitudes
We derive and apply the finite energy sum rules to pion photoproduction. We
evaluate the low energy part of the sum rules using several state-of-the-art
models. We show how the differences in the low energy side of the sum rules
might originate from different quantum number assignments of baryon resonances.
We interpret the observed features in the low energy side of the sum rules with
the expectation from Regge theory. Finally, we present a model, in terms of a
Regge-pole expansion, that matches the sum rules and the high-energy
observables.Comment: 19 pages, 15 figures and 4 table
Short words for the terminology of common animals A linguistic study
Ce travail est une Ă©tude prĂ©liminaire dans 34 langues, portant sur les mots dĂ©signant les animaux familiers. Ces mots sont trĂšs courts (moins de six lettres en moyenne). La linguistique peut permettre de mieux connaĂźtre l'histoire des animaux domestiques, quâil sâagisse de lâextension de lâĂ©levage ou de la domestication.This paper constitutes a preliminary study concerning the terminology of the domestic and pet animals in 34 languages. The words which designate these animals are short (less than six letters on the average). Linguistics allows a better knowledge of the history of domestic animals (extension of breeding, domestication)
Two neutrino double beta decay within the -approximation
We examine the contributions of odd-parity nuclear operators to the
two-neutrino double beta decay amplitude, which come from
the -wave Coulomb corrections to the electron wave functions and the recoil
corrections to the nuclear currents. Although they are formally of higher order
in or of the nucleon than the usual Fermi and Gamow-Teller
matrix elements, explicit calculations performed within the QRPA show that they
are significant when confronted with the experimental data.Comment: 9 pages, latex, no figure
Finite-Energy Sum Rules in Eta Photoproduction off the Nucleon
The reaction is studied in the high-energy regime
(with photon lab energies GeV) using
information from the resonance region through the use of finite-energy sum
rules (FESR). We illustrate how analyticity allows one to map the t-dependence
of the unknown Regge residue functions. We provide predictions for the energy
dependence of the beam asymmetry at high energies.Comment: Joint Physics Analysis Cente
Nucleon resonance contributions to unpolarised inclusive electron scattering
The first CLAS12 experiments will provide high-precision data on inclusive
electron scattering observables at a photon virtuality ranging from 0.05
GeV to 12 GeV and center-of-mass energies up to 4 GeV. In view of
this endeavour, we present the modeling of the resonant contributions to the
inclusive electron scattering observables. As input, we use the existing CLAS
electrocoupling results obtained from exclusive meson electroproduction data
off protons, and evaluate for the first time the resonant contributions based
on the experimental results on the nucleon resonance electroexcitation. The
uncertainties are given by the data and duly propagated through a Monte Carlo
approach. In this way, we obtain estimates for the resonant contributions,
important for insight into the nucleon parton distributions in the resonance
region and for the studies of quark-hadron duality
Counting, generating and sampling tree alignments
Pairwise ordered tree alignment are combinatorial objects that appear in RNA
secondary structure comparison. However, the usual representation of tree
alignments as supertrees is ambiguous, i.e. two distinct supertrees may induce
identical sets of matches between identical pairs of trees. This ambiguity is
uninformative, and detrimental to any probabilistic analysis.In this work, we
consider tree alignments up to equivalence. Our first result is a precise
asymptotic enumeration of tree alignments, obtained from a context-free grammar
by mean of basic analytic combinatorics. Our second result focuses on
alignments between two given ordered trees and . By refining our grammar
to align specific trees, we obtain a decomposition scheme for the space of
alignments, and use it to design an efficient dynamic programming algorithm for
sampling alignments under the Gibbs-Boltzmann probability distribution. This
generalizes existing tree alignment algorithms, and opens the door for a
probabilistic analysis of the space of suboptimal RNA secondary structures
alignments.Comment: ALCOB - 3rd International Conference on Algorithms for Computational
Biology - 2016, Jun 2016, Trujillo, Spain. 201
Off-shell pion electromagnetic form factor from a gauge-invariant Nambu-Jona-Lasinio model
The off--shell electromagnetic vertex function of pions and kaons is studied
in a bosonized Nambu--Jona-Lasinio model with a gauge--invariant proper--time
cutoff. The slope of the pion form factor with respect to the pion 4--momentum
is found to be equal to the on--shell pion charge radius in the chiral limit.
The off--shell slope of the form factor is zero, that of the
about 15\% smaller than that of the pion. We compare our results with those of
a recent calculation in chiral perturbation theory.Comment: (9 p., standard LaTeX, 1 PostScript figure appended) UNITUE-THEP-7/9
Cryogenic R&D at the CERN Central Cryogenic Laboratory
The Central Cryogenic Laboratory operates since many years at CERN in the framework of cryogenic R&D for accelerators and experiments. The laboratory hosts several experimental posts for small cryogen ic tests, all implemented with pumping facility for GHe and vacuum, and is equipped with a He liquefier producing 6.105 l/year, which is distributed in dewars. Tests include thermomechanical qualifica tion of structural materials, cryogenic and vacuum qualification of prototypes, evaluation of thermal losses of components. Some of the most relevant results obtained at the laboratory in the last yea rs are outlined in this paper
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