64,308 research outputs found
Percolation and lack of self-averaging in a frustrated evolutionary model
We present a stochastic evolutionary model obtained through a perturbation of
Kauffman's maximally rugged model, which is recovered as a special case. Our
main results are: (i) existence of a percolation-like phase transition in the
finite phase space case; (ii) existence of non self-averaging effects in the
thermodynamic limit. Lack of self-averaging emerges from a fragmentation of the
space of all possible evolutions, analogous to that of a geometrically broken
object. Thus the model turns out to be exactly solvable in the thermodynamic
limit.Comment: 22 pages, 1 figur
Statistics of optimal information flow in ensembles of regulatory motifs
Genetic regulatory circuits universally cope with different sources of noise
that limit their ability to coordinate input and output signals. In many cases,
optimal regulatory performance can be thought to correspond to configurations
of variables and parameters that maximize the mutual information between inputs
and outputs. Such optima have been well characterized in several biologically
relevant cases over the past decade. Here we use methods of statistical field
theory to calculate the statistics of the maximal mutual information (the
`capacity') achievable by tuning the input variable only in an ensemble of
regulatory motifs, such that a single controller regulates N targets. Assuming
(i) sufficiently large N, (ii) quenched random kinetic parameters, and (iii)
small noise affecting the input-output channels, we can accurately reproduce
numerical simulations both for the mean capacity and for the whole
distribution. Our results provide insight into the inherent variability in
effectiveness occurring in regulatory systems with heterogeneous kinetic
parameters.Comment: 14 pages, 6 figure
Dynamics of multi-frequency minority games
The dynamics of minority games with agents trading on different time scales
is studied via dynamical mean-field theory. We analyze the case where the
agents' decision-making process is deterministic and its stochastic
generalization with finite heterogeneous learning rates. In each case, we
characterize the macroscopic properties of the steady states resulting from
different frequency and learning rate distributions and calculate the
corresponding phase diagrams. Finally, the different roles played by regular
and occasional traders, as well as their impact on the system's global
efficiency, are discussed.Comment: 9 pages, 5 figure
Leptogenic Supersymmetry at the LHC
Leptogenic Supersymmetry is a scenario characterized by copious lepton
production in cascade decays. Due to the high lepton multiplicity and the lack
of significant missing energy, leptogenic supersymmetry provides very clean
channels which can be probed already with the early LHC data. Furthermore, the
Higgs may be discovered in the h->b bbar mode because the leptons accompanying
Higgs production efficiently suppress the background.Comment: 4 pages, 2 figures. Contribution to the proceedings of SUSY 09,
Northeastern University, Boston, M
Central Compact Objects in Supernova Remnants
Central Compact Objects (CCOs) are a handful of sources located close to the
geometrical center of young supernova remnants. They only show thermal-like,
soft X-ray emission and have no counterparts at any other wavelength. While the
first observed CCO turned out to be a very peculiar magnetar, discovery that
three members of the family are weakly magnetised Isolated Neutron Stars (INSs)
set the basis for an interpretation of the class. However, the phenomeology of
CCOs and their relationship with other classes of INSs, possibly ruled by
supernova fall-back accretion, are still far from being well understood.Comment: 7 pages, to appear in the proceedings of "Physics of Neutron Stars -
2017" Conference (July 10-14, Saint Petersburg), JPCS, eds. G.G. Pavlov, J.A.
Pons, P.S. Shternin & D.G. Yakovle
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