7,518 research outputs found
Generating functional analysis of complex formation and dissociation in large protein interaction networks
We analyze large systems of interacting proteins, using techniques from the
non-equilibrium statistical mechanics of disordered many-particle systems.
Apart from protein production and removal, the most relevant microscopic
processes in the proteome are complex formation and dissociation, and the
microscopic degrees of freedom are the evolving concentrations of unbound
proteins (in multiple post-translational states) and of protein complexes. Here
we only include dimer-complexes, for mathematical simplicity, and we draw the
network that describes which proteins are reaction partners from an ensemble of
random graphs with an arbitrary degree distribution. We show how generating
functional analysis methods can be used successfully to derive closed equations
for dynamical order parameters, representing an exact macroscopic description
of the complex formation and dissociation dynamics in the infinite system
limit. We end this paper with a discussion of the possible routes towards
solving the nontrivial order parameter equations, either exactly (in specific
limits) or approximately.Comment: 14 pages, to be published in Proc of IW-SMI-2009 in Kyoto (Journal of
Phys Conference Series
The lowest-lying baryon masses in covariant SU(3)-flavor chiral perturbation theory
We present an analysis of the baryon-octet and -decuplet masses using
covariant SU(3)-flavor chiral perturbation theory up to next-to-leading order.
Besides the description of the physical masses we address the problem of the
lattice QCD extrapolation. Using the PACS-CS collaboration data we show that a
good description of the lattice points can be achieved at next-to-leading order
with the covariant loop amplitudes and phenomenologically determined values for
the meson-baryon couplings. Moreover, the extrapolation to the physical point
up to this order is found to be better than the linear one given at
leading-order by the Gell-Mann-Okubo approach. The importance that a reliable
combination of lattice QCD and chiral perturbation theory may have for hadron
phenomenology is emphasized with the prediction of the pion-baryon and
strange-baryon sigma terms.Comment: Typos in formulas correcte
Production of Two Pions Induced by Neutrinos
We study the threshold production of two pions induced by neutrinos in
nucleon targets. The contribution of nucleon pole, pion and contact terms is
calculated using a chiral Lagrangian. The contribution of the Roper resonance,
neglected in earlier studies, has also been taken into account.Comment: Contribution to the proceedings of Chiral07, RCNP, Osaka, Japan.
Corrected version because of problems on some pdf viewer
Weak Quasi-elastic Production of Hyperons
The quasielastic weak production of and hyperons from
nucleons and nuclei induced by antineutrinos is studied in the energy region of
some ongoing neutrino oscillation experiments in the intermediate energy
region. The hyperon nucleon transition form factors determined from neutrino
nucleon scattering and an analysis of high precision data on semileptonic
decays of neutron and hyperons using SU(3) symmetry have been used. The nuclear
effects due to Fermi motion and final state interaction effects due to hyperon
nucleon scattering have also been studied. The numerical results for
differential and total cross sections have been presented.Comment: 26 pages, 10 figure
Covariance matrices and the separability problem
We propose a unifying approach to the separability problem using covariance
matrices of locally measurable observables. From a practical point of view, our
approach leads to strong entanglement criteria that allow to detect the
entanglement of many bound entangled states in higher dimensions and which are
at the same time necessary and sufficient for two qubits. From a fundamental
perspective, our approach leads to insights into the relations between several
known entanglement criteria -- such as the computable cross norm and local
uncertainty criteria -- as well as their limitations.Comment: 4 pages, no figures; v3: final version to appear in PR
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