45,518 research outputs found
The Redner - Ben-Avraham - Kahng cluster system
We consider a coagulation model first introduced by Redner, Ben-Avraham and
Krapivsky in [Redner, Ben-Avraham, Kahng: Kinetics of 'cluster eating', J.
Phys. A: Math. Gen., 20 (1987), 1231-1238], the main feature of which is that
the reaction between a j-cluster and a k-cluster results in the creation of a
|j-k|-cluster, and not, as in Smoluchowski's model, of a (j+k)-cluster. In this
paper we prove existence and uniqueness of solutions under reasonably general
conditions on the coagulation coefficients, and we also establish
differenciability properties and continuous dependence of solutions. Some
interesting invariance properties are also proved. Finally, we study the
long-time behaviour of solutions, and also present a preliminary analysis of
their scaling behaviour.Comment: 24 pages. 2 figures. Dedicated to Carlos Rocha and Luis Magalhaes on
the occasion of their sixtieth birthday
On the convergence to critical scaling profiles in submonolayer deposition models
In this work we study the rate of convergence to similarity profiles in a
mean field model for the deposition of a submonolayer of atoms in a crystal
facet, when there is a critical minimal size for the stability of the
formed clusters. The work complements recently published related results by the
same authors in which the rate of convergence was studied outside of a critical
direction in the cluster size vs. time plane. In this paper
we consider a different similarity variable, ,
corresponding to an inner expansion of that critical direction, and prove the
convergence of solutions to a similarity profile when with fixed, as well as the rate at which the limit is
approached.Comment: Dedicated to the memory of Jack Car
Rates of convergence to scaling profiles in a submonolayer deposition model and the preservation of memory of the initial condition
We establish rates of convergence of solutions to scaling (or similarity)
profiles in a coagulation type system modelling submonolayer deposition. We
prove that, although all memory of the initial condition is lost in the
similarity limit, information about the large cluster tail of the initial
condition is preserved in the rate of approach to the similarity profile. The
proof relies in a change of variables that allows for the decoupling of the
original infinite system of ordinary differential equations into a closed
two-dimensional nonlinear system for the monomer--bulk dynamics and a lower
triangular infinite dimensional linear one for the cluster dynamics. The
detailed knowledge of the long time monomer concentration, which was obtained
earlier by Costin et al. in (O. Costin, M. Grinfeld, K.P. O'Neill and H. Park,
Long-time behaviour of point islands under fixed rate deposition, Commun. Inf.
Syst. 13, (2), (2013), pp.183-200) using asymptotic methods and is rederived
here by center manifold arguments, is then used for the asymptotic evaluation
of an integral representation formula for the concentration of -clusters.
The use of higher order expressions, both for the Stirling expansion and for
the monomer evolution at large times allow us to obtain, not only the
similarity limit, but also the rate at which it is approached.Comment: Revised according to referee's suggestions; to be published in SIAM
J. Math. Ana
The Redner - Ben-Avraham - Kahng coagulation system with constant coefficients: the finite dimensional case
We study the behaviour as of solutions to the
Redner--Ben-Avraham--Kahng coagulation system with positive and compactly
supported initial data, rigorously proving and slightly extending results
originally established in [4] by means of formal arguments.Comment: 13 pages, 1 figur
Social-Aware Forwarding Improves Routing Performance in Pocket Switched Networks
Several social-aware forwarding strategies have been recently introduced in
opportunistic networks, and proved effective in considerably in- creasing
routing performance through extensive simulation studies based on real-world
data. However, this performance improvement comes at the expense of storing a
considerable amount of state information (e.g, history of past encounters) at
the nodes. Hence, whether the benefits on routing performance comes directly
from the social-aware forwarding mechanism, or indirectly by the fact state
information is exploited is not clear. Thus, the question of whether
social-aware forwarding by itself is effective in improving opportunistic
network routing performance remained unaddressed so far. In this paper, we give
a first, positive answer to the above question, by investigating the expected
message delivery time as the size of the net- work grows larger
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