π- forward dispersion relations with electromagnetic correctionsforward dispersion relations with electromagnetic corrections

Electromagnetic corrections to γπ ± → π 0 π ±

The amplitude for the anomalous transitions γπ → ππ is analyzed within Chiral Perturbation Theory including electromagnetic interactions. The presence of a t-channel one-photon exchange contribution induces sizeable O(e2) corrections which enhance the cross-section in the threshold region and bring the theoretical prediction into agreement with available data. In the case of the crossed reactio...

Near Scale Invariance with Modified Dispersion Relations

Uniaxial dielectric mediums with hyperbolic dispersion relations

The dispersion relations for conventional uniaxial dielectric mediums may be characterized as elliptical or elliptical–like, according to whether the medium is nondissipative or dissipative, respectively. However, under certain constitutive parameter regimes, the dispersion relations may be hyperbolic or hyperbolic–like. We investigate planewave propagation in a hyperbolic/hyperbolic–like uniax...

Forward dispersion relations and Roy equations in ππ scattering

We review results of an analysis of ππ interactions in S, P and D waves for two-pion effective mass from threshold to about 1.4 GeV. In particular we show a recent improvement of this analysis above the KK̄ threshold using more data for phase shifts and including the S0 wave inelasticity from ππ → KK̄. In addition, we have improved the fit to the f2(1270) resonance and used a more flexible P wave...

Parapositronium Decay and Dispersion Relations

Positronium decay rates are computed at the one-loop level, using convolutiontype factorized amplitudes. The dynamics of this factorization is probed with dispersion relations, showing that unallowed approximations are usually made, and some O ( α ) corrections missed. Further, we discuss the relevance of the Schrödinger wavefunction as the basis for perturbative calculations. Finally, we apply...