The formal similarity of the spectral distribution curve of temperature radiation to Maxwell’s velocity distribution curve is too striking to have remained hidden very long.

Zur Quantentheorie der Strahlung

Huygens' principle may reveal interaction between light and atoms

Thoughts on the Futurology in Research and Development of Innovative Materials

We describe formal work that relates the nite-volume spectrum in a quantum eld theory to scattering and decay amplitudes. This is of particular relevance to numerical calculations performed using Lattice Quantum Chromodynamics (LQCD). Correlators calculated using LQCD can only be determined on the Euclidean time axis. For this reason the standard method of determining scattering amplitudes via the Lehmann-Symanzik-Zimmermann reduction formula cannot be employed. By contrast, the nite-volume spectrum is directly accessible in LQCD calculations. Formalism for relating the spectrum to physical scattering observables is thus highly desirable. In this thesis we develop tools for extracting physical information from LQCD for four types of observables. First we analyze systems with multiple, strongly-coupled two-scalar channels. Here we accommodate both identical and nonidentical scalars, and in the latter case allow for degenerate as well as nondegenerate particle masses. Using relativistic eld theory, and summing to all orders in perturbation theory, we derive a result relating the nite-volume spectrum to the two-to-two scattering amplitudes of the coupled-channel theory. This generalizes the formalism of Martin L uscher for the case of single-channel scattering. Second we consider the weak decay of a single particle into multiple, coupled two-scalar channels. We show how the nite-volume matrixmore » element extracted in LQCD is related to matrix elements of asymptotic two-particle states, and thus to decay amplitudes. This generalizes work by Laurent Lellouch and Martin L uscher. Third we extend the method for extracting matrix elements by considering currents which insert energy, momentum and angular momentum. This allows one to extract transition matrix elements and form factors from LQCD. Finally we look beyond two-particle systems to those with three-particles in asymptotic states. Working again to all orders in relativistic eld theory, we derive a relation between the spectrum and an in nite-volume three-to-three scattering quantity. This nal analysis is the most complicated of the four, because the all-orders summation is more di cult for this system, and also because a number of new technical issues arise in analyzing the contributing diagrams.« less

/pdf/multi-hadron-observables-from-lattice-quantum-chromodynamics-2n0uyfch40.pdf

Multi-Hadron Observables from Lattice Quantum Chromodynamics

In 1917, Einstein published his paper [1] renowned for the discovery of stimulated emission. However, it also contained the principles which allowed the calculation of the universal photonic cross-section = λ2/2π. Any heavy electronic system will have this cross-section for photonic excitation and stimulated emission in its rest frame. The modifications of this cross-section due to the recoil of the emitter have not yet been calculated, but are in general expected to be second order in recoil velocity.

/pdf/the-universal-cross-section-of-photonic-interaction-48m5a4rcyg.pdf

Zur Quantentheorie der Strahlung

Citations

Huygens' principle may reveal interaction between light and atoms

Thoughts on the Futurology in Research and Development of Innovative Materials

Multi-Hadron Observables from Lattice Quantum Chromodynamics

The Universal Cross-Section of Photonic Interaction

5 – Quadrupolar and Other Types of Relaxation

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The collected papers of Albert Einstein

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