86,556 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
Properties of noncommutative axionic electrodynamics
Using the gauge-invariant but path-dependent variables formalism, we compute
the static quantum potential for noncommutative axionic electrodynamics, and
find a radically different result than the corresponding commutative case. We
explicitly show that the static potential profile is analogous to that
encountered in both non-Abelian axionic electrodynamics and in Yang-Mills
theory with spontaneous symmetry breaking of scale symmetry.Comment: 4 pages. To appear in PR
Analytical mode normalization and resonant state expansion for optical fibers - an efficient tool to model transverse disorder
We adapt the resonant state expansion to optical fibers such as capillary and
photonic crystal fibers. As a key requirement of the resonant state expansion
and any related perturbative approach, we derive the correct analytical
normalization for all modes of these fiber structures, including leaky modes
that radiate energy perpendicular to the direction of propagation and have
fields that grow with distance from the fiber core. Based on the normalized
fiber modes, an eigenvalue equation is derived that allows for calculating the
influence of small and large perturbations such as structural disorder on the
guiding properties. This is demonstrated for two test systems: a capillary
fiber and an endlessly single mode fiber.Comment: 10 pages, 4 figure
Group-cluster merging and the formation of starburst galaxies
A significant fraction of clusters of galaxies are observed to have
substructure, which implies that merging between clusters and subclusters is a
rather common physical process of cluster formation.
It still remains unclear how cluster merging affects the evolution of cluster
member galaxies.
We report the results of numerical simulations, which show the dynamical
evolution of a gas-rich late-type spiral in a merger between a small group of
galaxies and a cluster. The simulations demonstrate that time-dependent tidal
gravitational field of the merging excites non-axisymmetric structure of the
galaxy, subsequently drives efficient transfer of gas to the central region,
and finally triggers a secondary starburst.
This result provides not only a new mechanism of starbursts but also a close
physical relationship between the emergence of starburst galaxies and the
formation of substructure in clusters. We accordingly interpret post-starburst
galaxies located near substructure of the Coma cluster as one observational
example indicating the global tidal effects of group-cluster merging.
Our numerical results furthermore suggest a causal link between the observed
excess of blue galaxies in distant clusters and cluster virialization process
through hierarchical merging of subclusters.Comment: 5 pages 3 color figures, ApJL in pres
Efficient simulation of one-dimensional quantum many-body systems
We present a numerical method to simulate the time evolution, according to a
Hamiltonian made of local interactions, of quantum spin chains and systems
alike. The efficiency of the scheme depends on the amount of the entanglement
involved in the simulated evolution. Numerical analysis indicate that this
method can be used, for instance, to efficiently compute time-dependent
properties of low-energy dynamics of sufficiently regular but otherwise
arbitrary one-dimensional quantum many-body systems.Comment: 4 pages, 1 figur
A model for orientation effects in electron‐transfer reactions
A method for solving the single‐particle Schrödinger equation with an oblate spheroidal potential of finite depth is presented. The wave functions are then used to calculate the matrix element T_BA which appears in theories of nonadiabatic electron transfer. The results illustrate the effects of mutual orientation and separation of the two centers on TBA. Trends in these results are discussed in terms of geometrical and nodal structure effects. Analytical expressions related to T_BA for states of spherical wells are presented and used to analyze the nodal structure effects for T_BA for the spheroidal wells
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