3,228 research outputs found
Network synchronization: Optimal and Pessimal Scale-Free Topologies
By employing a recently introduced optimization algorithm we explicitely
design optimally synchronizable (unweighted) networks for any given scale-free
degree distribution. We explore how the optimization process affects
degree-degree correlations and observe a generic tendency towards
disassortativity. Still, we show that there is not a one-to-one correspondence
between synchronizability and disassortativity. On the other hand, we study the
nature of optimally un-synchronizable networks, that is, networks whose
topology minimizes the range of stability of the synchronous state. The
resulting ``pessimal networks'' turn out to have a highly assortative
string-like structure. We also derive a rigorous lower bound for the Laplacian
eigenvalue ratio controlling synchronizability, which helps understanding the
impact of degree correlations on network synchronizability.Comment: 11 pages, 4 figs, submitted to J. Phys. A (proceedings of Complex
Networks 2007
Tests of Basic Quantum Mechanics in Oscillation Experiments
According to standard quantum theory, the time evolution operator of a
quantum system is independent of the state of the system. One can, however,
consider systems in which this is not the case: the evolution operator may
depend on the density operator itself. The presence of such modifications of
quantum theory can be tested in long baseline oscillation experiments.Comment: 8 pages, LaTeX; no macros neede
The Chagos Islands cases: the empire strikes back
Good governance requires the accommodation of multiple interests in the cause of decision making. However, undue regard for particular sectional interests can take their toll upon public faith in government administration. Historically, broad conceptions of the good of the commonwealth were employed to outweigh the interests of groups that resisted colonisation. In the decision making of the British Empire, the standard approach for justifying the marginalisation of the interests of colonised groups was that they were uncivilised and that particular hardships were the price to be paid for bringing to them the imperial dividend of industrial society. It is widely assumed that with the dismantling of the British Empire, such impulses and their accompanying jurisprudence became a thing of the past. Even as decolonisation proceeded apace after the Second World War, however, the United Kingdom maintained control of strategically important islands with a view towards sustaining its global role. In an infamous example from this twilight period of empire, in the 1960s imperial interests were used to justify the expulsion of the Chagos islanders from the British Indian Ocean Territory (BIOT). Into the twenty-first century, this forced elision of the UK’s interests with the imperial “common good” continues to take centre stage in courtroom battles over the islanders’ rights, being cited before domestic and international tribunals in order to maintain the Chagossians’ exclusion from their homeland. This article considers the new jurisprudence of imperialism which has emerged in a string of decisions which have continued to marginalise the Chagossians’ interests
h analogue of Newton's binomial formula
In this letter, the --analogue of Newton's binomial formula is obtained in
the --deformed quantum plane which does not have any --analogue. For
, this is just the usual one as it should be. Furthermore, the binomial
coefficients reduce to for . \\ Some properties of the
--binomial coefficients are also given. \\ Finally, I hope that such results
will contribute to an introduction of the --analogue of the well--known
functions, --special functions and --deformed analysis.Comment: 6 pages, latex Jounal-ref: J. Phys. A: Math. Gen. 31 (1998) L75
Numerical study of a non-equilibrium interface model
We have carried out extensive computer simulations of one-dimensional models
related to the low noise (solid-on-solid) non-equilibrium interface of a two
dimensional anchored Toom model with unbiased and biased noise. For the
unbiased case the computed fluctuations of the interface in this limit provide
new numerical evidence for the logarithmic correction to the subnormal L^(1/2)
variance which was predicted by the dynamic renormalization group calculations
on the modified Edwards-Wilkinson equation. In the biased case the simulations
are in close quantitative agreement with the predictions of the Collective
Variable Approximation (CVA), which gives the same L^(2/3) behavior of the
variance as the KPZ equation.Comment: 15 pages revtex, 4 Postscript Figure
Microscopic Black Hole Pairs in Highly-Excited States
We consider the quantum mechanics of a system consisting of two identical,
Planck-size Schwarzschild black holes revolving around their common center of
mass. We find that even in a very highly-excited state such a system has very
sharp, discrete energy eigenstates, and the system performs very rapid
transitions from a one stationary state to another. For instance, when the
system is in the 100th excited state, the life times of the energy eigenstates
are of the order of s, and the energies of gravitons released in
transitions between nearby states are of the order of eV.Comment: 22 pages, 3 figures, uses RevTe
One-Loop Maximal Helicity Violating Amplitudes in N=4 Super Yang-Mills Theories
One-loop maximal helicity violating (MHV) amplitudes in N=4 super Yang-Mills
(SYM) theories are analyzed, using the prescription of Cachazo, Svrcek, and
Witten (CSW). The relations between leading N_c amplitudes A_{n;1} and
sub-leading amplitudes A_{n;c} obtained by the CSW prescription are found to be
identical to those obtained from conventional field theory calculations.
Combining with existing results, this establishes the validity of the CSW
prescription to one-loop in the calculation of MHV amplitudes in N=4 SYM
theories of finite N_c.Comment: Minor changes and typos fixed. Published version in JHE
A Supersymmetric Stueckelberg U(1) Extension of the MSSM
A Stueckelberg extension of the MSSM with only one abelian vector and one
chiral superfield as an alternative to an abelian extension with Higgs scalars
is presented. The bosonic sector contains a new gauge boson Z' which is a sharp
resonance, and a new CP-even scalar, which combines with the MSSM Higgs bosons
to produce three neutral CP-even massive states. The neutral fermionic sector
has two additional fermions which mix with the four MSSM neutralinos to produce
an extended 6x6 neutralino mass matrix. For the case when the LSP is composed
mostly of the Stueckelberg fermions, the LSP of the MSSM will be unstable,
which leads to exotic decays of sparticles with many leptons in final states.
Prospects for supersymmetry searches and for dark matter are discussed.Comment: 10 page
Meanfield treatment of Bragg scattering from a Bose-Einstein condensate
A unified semiclassical treatment of Bragg scattering from Bose-Einstein
condensates is presented. The formalism is based on the Gross-Pitaevskii
equation driven by classical light fields far detuned from atomic resonance. An
approximate analytic solution is obtained and provides quantitative
understanding of the atomic momentum state oscillations, as well as a simple
expression for the momentum linewidth of the scattering process. The validity
regime of the analytic solution is derived, and tested by three dimensional
cylindrically symmetric numerical simulations.Comment: 21 pages, 10 figures. Minor changes made to documen
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