3,521 research outputs found
Pair Formation within Multi-Agent Populations
We present a simple model for the formation of pairs in multi-agent
populations of type A and B which move freely on a spatial network. Each agent
of population A (and B) is labeled as Ai (and Bj) with i=1,.. NA (and j=1,..NB)
and carries its own individual list of characteristics or 'phenotype'. When
agents from opposite populations encounter one another on the network, they can
form a relationship if not already engaged in one. The length of time for which
any given pair stays together depends on the compatibility of the two
constituent agents. Possible applications include the human dating scenario,
and the commercial domain where two types of businesses A and B have members of
each type looking for a business partner, i.e. Ai+Bj-->Rij. The pair Rij then
survives for some finite time before dissociating Rij-->Ai+Bj. There are many
possible generalizations of this basic setup. Here we content ourselves with
some initial numerical results for the simplest of network topologies, together
with some accompanying analytic analysis.Comment: Special Issue on Complex Networks, edited by Dirk Helbin
Fractal Growth from Local Instabilities
We study, both with numerical simulations and theoretical methods, a cellular
automata model for continuum equations describing growth processes in the
presence of an external flux of particles. As a result of local instabilities
we find a fractal regime of growth for small external fluxes. The growing tip
is selected with probability proportional to the curvature in the point. A
parameter gives the probability of lateral growth on the tip. The value of
determines the fractal dimension of the aggregate. Furthermore, for each
value of a cross-over between two different fractal dimensions is observed.
Instead, the roughness exponent of the aggregates does not depend on
(). Fixed scale transformation approach is applied to compute
theoretically the fractal dimension for one of the branches of the structure.Comment: 7 pages, 5 figures, submitted to EP
Chronology Protection in AdS/CFT
We review the issue of chronology protection and show how string theory can
solve it in the half BPS sector of AdS/CFT. According to the LLM prescription,
half BPS excitations of AdS_5 x S^5 geometries in type IIB string theory can be
mapped into free fermion configurations. We show that unitarity of the theory
describing these fermions is intimately related to the protection of the
chronology in the dual geometries.Comment: 7 pages, 7 figures, contribution to the proceedings of the RTN
workshop "Constituents, Fundamental Forces and Symmetries of the Universe",
Corfu, Greece, 20-26 September 200
A note on simple applications of the Killing Spinor Identities
We show how the Killing Spinor Identities (KSI) can be used to reduce the
number of independent equations of motion that need to be checked explicitly to
make sure that a supersymmetric configuration is a classical supergravity
solution. We also show how the KSI can be used to compute BPS relations between
masses and charges.Comment: 10 pages, latex2e. Comments and references added. Version to be
published in Physics Letters
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