364 research outputs found
DCC: Attractive Idea Seeks Serious Confirmation
The theoretical ideas relevant for the physics of the disoriented chiral
condensate (DCC) are reviewed.Comment: 18 pages LaTex, based on invited lecture given by A.Krzywicki at the
workshop "Quark, plasma and beyond", Zif, Bielefeld, May 1996 ; a reference
is correcte
Edge usage, motifs and regulatory logic for cell cycling genetic networks
The cell cycle is a tightly controlled process, yet its underlying genetic
network shows marked differences across species. Which of the associated
structural features follow solely from the ability to impose the appropriate
gene expression patterns? We tackle this question in silico by examining the
ensemble of all regulatory networks which satisfy the constraint of producing a
given sequence of gene expressions. We focus on three cell cycle profiles
coming from baker's yeast, fission yeast and mammals. First, we show that the
networks in each of the ensembles use just a few interactions that are
repeatedly reused as building blocks. Second, we find an enrichment in network
motifs that is similar in the two yeast cell cycle systems investigated. These
motifs do not have autonomous functions, but nevertheless they reveal a
regulatory logic for cell cycling based on a feed-forward cascade of activating
interactions.Comment: 9 pages, 9 figures, to be published in Phys. Rev.
Perturbing General Uncorrelated Networks
This paper is a direct continuation of an earlier work, where we studied
Erd\"os-R\'enyi random graphs perturbed by an interaction Hamiltonian favouring
the formation of short cycles. Here, we generalize these results. We keep the
same interaction Hamiltonian but let it act on general graphs with uncorrelated
nodes and an arbitrary given degree distribution. It is shown that the results
obtained for Erd\"os-R\'enyi graphs are generic, at the qualitative level.
However, scale-free graphs are an exception to this general rule and exhibit a
singular behaviour, studied thoroughly in this paper, both analytically and
numerically.Comment: 7 pages, 7 eps figures, 2-column revtex format, references adde
Adaptive networks of trading agents
Multi-agent models have been used in many contexts to study generic
collective behavior. Similarly, complex networks have become very popular
because of the diversity of growth rules giving rise to scale-free behavior.
Here we study adaptive networks where the agents trade ``wealth'' when they are
linked together while links can appear and disappear according to the wealth of
the corresponding agents; thus the agents influence the network dynamics and
vice-versa. Our framework generalizes a multi-agent model of Bouchand and
Mezard, and leads to a steady state with fluctuating connectivities. The system
spontaneously self-organizes into a critical state where the wealth
distribution has a fat tail and the network is scale-free; in addition, network
heterogeneities lead to enhanced wealth condensation.Comment: 7 figure
Phase transition and topology in 4d simplicial gravity
We present data indicating that the recent evidence for the phase transition
being of first order does not result from a breakdown of the ergodicity of the
algorithm. We also present data showing that the thermodynamical limit of the
model is independent of topology.Comment: 3 latex pages + 4 ps fig. + espcrc2.sty. Talk presented at
LATTICE(gravity
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