59,440 research outputs found
Massless and massive one-loop three-point functions in negative dimensional approach
In this article we present the complete massless and massive one-loop
triangle diagram results using the negative dimensional integration method
(NDIM). We consider the following cases: massless internal fields; one massive,
two massive with the same mass m and three equal masses for the virtual
particles. Our results are given in terms of hypergeometric and
hypergeometric-type functions of external momenta (and masses for the massive
cases) where the propagators in the Feynman integrals are raised to arbitrary
exponents and the dimension of the space-time D. Our approach reproduces the
known results as well as other solutions as yet unknown in the literature.
These new solutions occur naturally in the context of NDIM revealing a
promising technique to solve Feynman integrals in quantum field theories
Divide and conquer: resonance induced by competitive interactions
We study an Ising model in a network with disorder induced by the presence of
both attractive and repulsive links. This system is subjected to a subthreshold
signal, and the goal is to see how the response is enhanced for a given
fraction of repulsive links. This can model a network of spin-like neurons with
excitatory and inhibitory couplings. By means of numerical simulations and
analytical calculations we find that there is an optimal probability, such that
the coherent response is maximal
Spin-3 Chromium Bose-Einstein Condensates
We analyze the physics of spin-3 Bose-Einstein condensates, and in particular
the new physics expected in on-going experiments with condensates of Chromium
atoms. We first discuss the ground-state properties, which, depending on still
unknown Chromium parameters, and for low magnetic fields can present various
types of phases. We also discuss the spinor-dynamics in Chromium spinor
condensates, which present significant qualitative differences when compared to
other spinor condensates. In particular, dipole-induced spin relaxation may
lead for low magnetic fields to transfer of spin into angular momentum similar
to the well-known Einstein-de Haas effect. Additionally, a rapid large
transference of population between distant magnetic states becomes also
possible.Comment: 4 pages, 3 eps figures. Error in the previous version correcte
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