31,685 research outputs found
Impact factors for Reggeon-gluon transition in N = 4 SYM with large number of colours
We calculate impact factors for Reggeon-gluon transition in supersymmetric
Yang-Mills theory with four supercharges at large number of colours Nc. In the
next-to-leading order impact factors are not uniquely defined and must accord
with BFKL kernels and energy scales. We obtain the impact factor corresponding
to the kernel and the energy evolution parameter, which is invariant under
Moebius transformation in momentum space, and show that it is also Moebius
invariant up to terms taken into account in the BDS ansatz.Comment: 13 page
Suppressing Proton Decay in Theories with Localised Fermions
We calculate the contribution to the proton decay amplitude from Kaluza-Klein
lepto-quarks in theories with extra dimensions, localised fermions and gauge
fields which propagate in the bulk. Such models naturally occur within the
context of M-theory. In SU(5) models we show that carefully including all such
modes gives a distinctive pattern of decays through various channels including
a strong suppression of decays into neutrinos or right handed positrons. By
contrast there is no such suppression for SO(10).Comment: 19 page
The Rise of the Second Generation: Changing Patterns in Hispanic Population Growth
Provides a detailed look at demographic trends, based on projections of Hispanic population growth from 2000 to 2050
Multi-integral representations for associated Legendre and Ferrers functions
For the associated Legendre and Ferrers functions of the first and second
kind, we obtain new multi-derivative and multi-integral representation
formulas. The multi-integral representation formulas that we derive for these
functions generalize some classical multi-integration formulas. As a result of
the determination of these formulae, we compute some interesting special values
and integral representations for certain particular combinations of the degree
and order including the case where there is symmetry and antisymmetry for the
degree and order parameters. As a consequence of our analysis, we obtain some
new results for the associated Legendre function of the second kind including
parameter values for which this function is identically zero.Comment: 22 page
Aspects of stochastic resonance in reaction-diffusion systems: The nonequilibrium-potential approach
We analyze several aspects of the phenomenon of stochastic resonance in
reaction-diffusion systems, exploiting the nonequilibrium potential's
framework. The generalization of this formalism (sketched in the appendix) to
extended systems is first carried out in the context of a simplified scalar
model, for which stationary patterns can be found analytically. We first show
how system-size stochastic resonance arises naturally in this framework, and
then how the phenomenon of array-enhanced stochastic resonance can be further
enhanced by letting the diffusion coefficient depend on the field. A yet less
trivial generalization is exemplified by a stylized version of the
FitzHugh-Nagumo system, a paradigm of the activator-inhibitor class. After
discussing for this system the second aspect enumerated above, we derive from
it -through an adiabatic-like elimination of the inhibitor field- an effective
scalar model that includes a nonlocal contribution. Studying the role played by
the range of the nonlocal kernel and its effect on stochastic resonance, we
find an optimal range that maximizes the system's response.Comment: 16 pages, 15 figures, uses svjour.cls and svepj-spec.clo. Minireview
to appear in The European Physical Journal Special Topics (issue in memory of
Carlos P\'erez-Garc\'{\i}a, edited by H. Mancini
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