339 research outputs found
A model for cascading failures in complex networks
Large but rare cascades triggered by small initial shocks are present in most
of the infrastructure networks. Here we present a simple model for cascading
failures based on the dynamical redistribution of the flow on the network. We
show that the breakdown of a single node is sufficient to collapse the
efficiency of the entire system if the node is among the ones with largest
load. This is particularly important for real-world networks with an highly
hetereogeneous distribution of loads as the Internet and electrical power
grids.Comment: 4 pages, 4 figure
Minimum Energy Configurations in the -Body Problem and the Celestial Mechanics of Granular Systems
Minimum energy configurations in celestial mechanics are investigated. It is
shown that this is not a well defined problem for point-mass celestial
mechanics but well-posed for finite density distributions. This naturally leads
to a granular mechanics extension of usual celestial mechanics questions such
as relative equilibria and stability. This paper specifically studies and finds
all relative equilibria and minimum energy configurations for and
develops hypotheses on the relative equilibria and minimum energy
configurations for bodies.Comment: Accepted for publication in Celestial Mechanics and Dynamical
Astronom
Book Reviews
Review of Prehistory, by Derek Roe; Aspects of Prehistory, by Grahame Clark; World Prehistory, by Grahame Clark; Introductory Readings in Archaeology, by Brian M. Fagan, ed.; The Origins of Civilization, by Carroll L. Riley; The Archaeology of Early Man, by J. M. Coles and E. S. Higgs; Shipwrecks and Archaeology, by Peter Throckmorton; A History of Dyed Textiles, by Stuart Robinson; Food in Antiquity, by Don and Patricia Brothwell; World Archaeology, Vol. 1, nos. 1, 2, 3, by Roy Hodson and Colin Platt, eds.; The Structure and Growth of Australia's Aboriginal Population, by F. Lancaster Jones; Attitudes and Social Conditions, by Ronald Taft, John L. M. Dawson, and Pamela Beasley; Aboriginal Settlements, by J. P. M. Long; The Destruction of Aboriginal Society, by C. D. Rowley; Aboriginal Advancement to Integration, by H. P. Schapper
Generalized Uncertainty Principle, Modified Dispersion Relations and Early Universe Thermodynamics
In this paper, we study the effects of Generalized Uncertainty Principle(GUP)
and Modified Dispersion Relations(MDRs) on the thermodynamics of
ultra-relativistic particles in early universe. We show that limitations
imposed by GUP and particle horizon on the measurement processes, lead to
certain modifications of early universe thermodynamics.Comment: 21 Pages, 3 eps Figure, Revised Versio
Cascade-based attacks on complex networks
We live in a modern world supported by large, complex networks. Examples
range from financial markets to communication and transportation systems. In
many realistic situations the flow of physical quantities in the network, as
characterized by the loads on nodes, is important. We show that for such
networks where loads can redistribute among the nodes, intentional attacks can
lead to a cascade of overload failures, which can in turn cause the entire or a
substantial part of the network to collapse. This is relevant for real-world
networks that possess a highly heterogeneous distribution of loads, such as the
Internet and power grids. We demonstrate that the heterogeneity of these
networks makes them particularly vulnerable to attacks in that a large-scale
cascade may be triggered by disabling a single key node. This brings obvious
concerns on the security of such systems.Comment: 4 pages, 4 figures, Revte
Restriction fragment length polymorphisms, races and vegetative compatibility groups within a worldwide collection of Fusarium oxysporum f.sp. gladioli
Lorentz invariance violation in top-down scenarios of ultrahigh energy cosmic ray creation
The violation of Lorentz invariance (LI) has been invoked in a number of ways
to explain issues dealing with ultrahigh energy cosmic ray (UHECR) production
and propagation. These treatments, however, have mostly been limited to
examples in the proton-neutron system and photon-electron system. In this paper
we show how a broader violation of Lorentz invariance would allow for a series
of previously forbidden decays to occur, and how that could lead to UHECR
primaries being heavy baryonic states or Higgs bosons.Comment: Replaced with heavily revised (see new Abstract) version accepted by
Phys. Rev. D. 6 page
Near-Horizon Conformal Symmetry and Black Hole Entropy in Any Dimension
Recently, Carlip proposed a derivation of the entropy of the two-dimensional
dilatonic black hole by investigating the Virasoro algebra associated with a
newly introduced near-horizon conformal symmetry. We point out not only that
the algebra of these conformal transformations is not well defined on the
horizon, but also that the correct use of the eigenvalue of the operator
yields vanishing entropy. It has been shown that these problems can be resolved
by choosing a different basis of the conformal transformations which is regular
even at the horizon. We also show the generalization of Carlip's derivation to
any higher dimensional case in pure Einstein gravity. The entropy obtained is
proportional to the area of the event horizon, but it also depends linearly on
the product of the surface gravity and the parameter length of a horizon
segment in consideration. We finally point out that this derivation of black
hole entropy is quite different from the ones proposed so far, and several
features of this method and some open issues are also discussed.Comment: 14 pages, no figur
A Study of Phase Transition in Black Hole Thermodynamics
This paper deals with five-dimensional black hole solutions in (a)
Einstein-Maxwell-Gauss-Bonnet theory with a cosmological constant and
(b)Einstein-Yang-Mills-Gauss-Bonnet theory for spherically symmetric space
time. In both the cases the possibility of phase transition is examined and it
is analyzed whether the phase transition is a Hawking-Page type phase
transition or not.Comment: 16 figure
TeV Astrophysics Constraints on Planck Scale Lorentz Violation
We analyze observational constraints from TeV astrophysics on Lorentz
violating nonlinear dispersion for photons and electrons without assuming any a
priori equality between the photon and electron parameters. The constraints
arise from thresholds for vacuum Cerenkov radiation, photon decay and
photo-production of electron-positron pairs. We show that the parameter plane
for cubic momentum terms in the dispersion relations is constrained to an order
unity region in Planck units. We find that the threshold configuration can
occur with an asymmetric distribution of momentum for pair creation, and with a
hard photon for vacuum Cerenkov radiation.Comment: 4 pages, RevTeX4, 1 figure. Some references and a footnote added,
improved discussion on the photon annihilation and GZK cutoff. Minor changes
of wording. Main results unchanged. Version to appear as a Rapid
Communication in PR
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