Enhancement of Compton scattering by an effective coupling constant

Abstract

A robust thermodynamic argument shows that a small reduction of the effective coupling constant α of QED greatly enhances the low-energy Compton-scattering cross section and that the Thomson scattering length is connected to a fundamental scale λ. A discussion provides a possible quantum interpretation of this enormous sensitivity to changes in the effective coupling constant α.

Inelastic x-ray scattering from valence electrons near absorption edges of FeTe andTiSe2

“…When the scattering process is completed, it leaves behind low-lying valence excited states conserving energy and crystal momentum, and the Thomson cross section σ T h of this resonant scattering is increased by the factor η compared to the nonresonant cross section. The solution of the renormalizationgroup equation gives [18] …”

“…In order to explore the scattering of nearly free electrons by a photon tuned near the binding energy of a core level, we have introduced a scheme based on the renormalization-group (RG) theory [18] able to cast the complicated RIXS problem to a much simpler IXS problem in an effective medium described by an effective dielectric function , which integrates out the effect of the core electrons. In the RG approach, a differential equation describing the evolution of the coupling constant with screening yields the renormalization factor η for the effective Thomson cross section in the polarizable medium.…”

High-temperature cuprate superconductors studied by x-ray Compton scattering and positron annihilation spectroscopies

“…Compton scattering refers to inelastic x-ray scattering [13][14][15] in the deeply inelastic limit in which the nonresonant scattering cross-section is well-known to become proportional to the ground state momentum density [16]. Compton scattering thus provides a uniquely powerful probe of the many body ground state wave function.…”

Enhancement of Raman scattering from molecules placed near metal nanoparticles

“…is a renormalization group function [26] determining the scale  for a given coupling g. By solving Eq. (4), one finds that the inelastic scattering cross section σ is renormalized by…”

“…The present paper explores the possibility to use a renormalization-group approach [26] to derive the fundamental origin of the enhancement mechanism of SERS. This method is beyond perturbation theory and can take in account collision processes between light quanta and the elementary excitations of molecules at metallic surfaces.…”