6,626 research outputs found
New light on electromagnetic corrections to the scattering parameters obtained from experiments on pionium
We calculate the electromagnetic corrections needed to obtain isospin
invariant hadronic pion-pion s-wave scattering lengths a^0, a^2 from the
elements a_cc, a_0c of the s-wave scattering matrix for the (\pi^+ \pi^-, \pi^0
\pi^0) system at the \pi^+ \pi^- threshold. These elements can be extracted
from experiments on pionium. Our calculation uses energy independent hadronic
pion-pion potentials that satisfactorily reproduce the low-energy phase shifts
given by two-loop chiral pertur- bation theory. We also take into account an
important relativistic effect whose inclusion influences the corrections
considerably.Comment: 14 pages including 3 figures. Uses elsart.cls. Some numbers have been
updated and a few typos have been correcte
Effective Chiral Lagrangians with an SU(3)-Broken Vector-Meson Sector
The accuracy of effective chiral lagrangians including vector-mesons as
(hidden symmetry) gauge fields is shown to be improved by taking into account
SU(3)-breaking in the vector-meson sector. The masses, , and couplings to
the photon field and pseudoscalar pairs, and , are all
consistently described in terms of two parameters, which also fit the values
for the pseudoscalar decay-constants, , and charge radii, . The
description of the latter is further improved when working in the context of
chiral perturbation theory.Comment: 10 pages, LaTeX file, A postscript version can be obtained from
anonymous ftp at ftp://ftp.ifae.es/preprint.ft/
Organic Cation Transporter 3: A Cellular Mechanism Underlying Rapid, Non-Genomic Glucocorticoid Regulation of Monoaminergic Neurotransmission, Physiology, and Behavior
Corticosteroid hormones act at intracellular glucocorticoid receptors (GR) and mineralocorticoid receptors (MR) to alter gene expression, leading to diverse physiological and behavioral responses. In addition to these classical genomic effects, corticosteroid hormones also exert rapid actions on physiology and behavior through a variety of non-genomic mechanisms, some of which involve GR or MR, and others of which are independent of these receptors. One such GR-independent mechanism involves corticosteroid-induced inhibition of monoamine transport mediated by “uptake2” transporters, including organic cation transporter 3 (OCT3), a low-affinity, high-capacity transporter for norepinephrine, epinephrine, dopamine, serotonin and histamine. Corticosterone directly and acutely inhibits OCT3-mediated transport. This review describes the studies that initially characterized uptake2 processes in peripheral tissues, and outlines studies that demonstrated OCT3 expression and corticosterone-sensitive monoamine transport in the brain. Evidence is presented supporting the hypothesis that corticosterone can exert rapid, GR-independent actions on neuronal physiology and behavior by inhibiting OCT3-mediated monoamine clearance. Implications of this mechanism for glucocorticoid-monoamine interactions in the context-dependent regulation of behavior are discussed
Effective Lagrangians in bound state calculations
In order to investigate specific aspects of bound state calculations in a
non-relativistic framework, we consider the energy-levels of a massive scalar
particle, which moves in an external field and interacts in addition with a
massless scalar particle. The discussion includes the following topics:
dimensionally regularized bound-state calculations, ultraviolet finiteness of
bound-state observables and their independence of the off-mass-shell behavior
of Green functions, non-renormalizable interactions, structure of the
non-relativistic two-point function, power counting and matching.Comment: 45 pages, 8 postscript figures, RevTeX styl
Derivation of the Effective Pion-Nucleon Lagrangian within Heavy Baryon Chiral Perturbation Theory
We develop a method for constructing the Heavy Baryon Chiral Perturbation
Theory Lagrangian (L_{HBChPT}), to a given chiral order, within HBChPT. We work
within SU(2) theory, with only the pion field interacting with the nucleon. The
main difficulties, which are solved, are to develop techniques for implementing
charge conjugation invariance, and for taking the nucleon on shell, both within
the nonrelativistic formalism. We obtain complete lists of independent terms in
L_{HBChPT} through O(q^3) for off- shell nucleons. Then, eliminating
equation-of-motion (eom) terms at the relativistic and nonrelativistic level
(both within HBChPT), we obtain L_{HBCHPT} for on-shell nucleons, through
O(q^3). The extension of the method (to obtain on-shell L_{HBChPT} within
HBChPT) to higher orders is also discussed.Comment: 31 pages, LaTex; original version shortened; 2 new tables and new
material on extending on-shell reduction method within HBChPT to arbitrary
chiral orders, include
Integrating out the heaviest quark in N--flavour ChPT
We extend a known method to integrate out the strange quark in three flavour
chiral perturbation theory to the context of an arbitrary number of flavours.
As an application, we present the explicit formulae to one--loop accuracy for
the heavy quark mass dependency of the low energy constants after decreasing
the number of flavours by one while integrating out the heaviest quark in
N--flavour chiral perturbation theory.Comment: 18 pages, 1 figure. Text and references added. To appear in EPJ
- …