Gerhard F. Ecker

The Role of Resonances in Chiral Perturbation Theory

Abstract The strong interactions of low-lying meson resonances (spin ⩽ 1) with the octet of pseudoscalar mesons ( π , K , η ) are considered to lowest order in the derivative expansion of chiral SU(3). The resonance contributions to the coupling constants of the O( p 4 ) effective chiral lagrangian involving pseudoscalar fields only are determined. These low-energy coupling constants are found to be dominated by the resonance contributions. Although we do not treat the vector and axial-vector mesons as gauge bosons of local chiral symmetry, vector meson dominance emerges as a prominent result of our analysis. As a further application of chiral resonance couplings, we calculate the electromagnetic pion mass difference to lowest order in chiral perturbation theory with explicit resonance fields.

Chiral Lagrangians for Massive Spin 1 Fields

Abstract There are different ways to include massive spin-1 particles in the effective low-energy lagrangian. We analyse these ambiguities in the context of chiral perturbation theory to order p 4 . We show that, provided consistency with QCD asymptotic behaviour is incorporated, the structure of the effective couplings induced by vector and axial-vector exchange is model independent.

Chiral perturbation theory

Abstract The main elements and methods of chiral perturbation theory, the effective field theory of the Standard Model below the scale of spontaneous chiral symmetry breaking, are summarized. Applications to the interactions of mesons and baryons at low energies are reviewed, with special emphasis on developments of the last three years. Among the topics covered are the strong, electromagnetic and semileptonic weak interactions of mesons at and beyond next-to-leading order in the chiral expansion, nonleptonic weak interactions of mesons, virtual photon corrections and the meson-baryon system. The discussion is limited to processes at zero temperature, for infinite volume and with at most one baryon.

Coexistence of passive and carrier-mediated processes in drug transport.

The permeability of biological membranes is one of the most important determinants of the pharmacokinetic processes of a drug. Although it is often accepted that many drug substances are transported across biological membranes by passive transcellular diffusion, a recent hypothesis speculated that carrier-mediated mechanisms might account for the majority of membrane drug transport processes in biological systems. Based on evidence of the physicochemical characteristics and of in vitro and in vivo findings for marketed drugs, as well as results from real-life discovery and development projects, we present the view that both passive transcellular processes and carrier-mediated processes coexist and contribute to drug transport activities across biological membranes.

The mesonic chiral lagrangean of order p6

We construct the effective chiral lagrangean for chiral perturbation theory in the mesonic even-intrinsic-parity sector at order p6. The lagrangean contains 112 in principle measurable + 3 contact terms for the general case of n light flavours, 90+4 for three and 53+4 for two flavours. The equivalence between equations of motion and field redefinitions to remove spurious terms in the lagrangeans is shown to all orders in the chiral expansion. We also discuss and implement other methods for reducing the number of terms to a minimal set.

Elastic ππ scattering to two loops

We evaluate analytically the elastic

Radiative Kaon Decays and CP Violation in Chiral Perturbation Theory

\pi\pi

Renormalization of Chiral Perturbation Theory to Order p 6

scattering amplitude to two loops in chiral perturbation theory and give numerical values for the two

Towards a consistent estimate of the chiral low-energy constants☆

S

K → πℓ+ℓ− decays in the effective chiral lagrangian of the standard model

--wave scattering lengths and for the phase shift difference