arXiv subjects

H. Ruegg

Publications and source records attributed to H. Ruegg.

3 recordsLinked to original sources

arXiv1999

The Road to Stueckelberg's Covariant Perturbation Theory as Illustrated by Successive Treatments of Compton Scattering

We review the history of the road to a manifestly covariant perturbative calculus within quantum electrodynamics from the early semi-classical results of the mid-twenties to the complete formalism of Stueckelberg in 1934. We chose as our case study the calculation of the cross-section of the Compton effect. We analyse Stueckelberg's paper extensively. This is our first contribution to a study of his fundamental contributions to the theoretical physics of twentieth century.

physics.hist-ph↗

arXiv1993

Classical and Quantum Mechanics of Free \k Relativistic Systems

We consider the Hamiltonian and Lagrangian formalism describing free \k-relativistic particles with their four-momenta constrained to the \k-deformed mass shell. We study the modifications of the formalism which follow from the introduction of space coordinates with nonvanishing Poisson brackets and from the redefinitions of the energy operator. The quantum mechanics of free \k-relativistic particles and of the free \k-relativistic oscillator is also presented. It is shown that the \k-relativistic oscillator describes a quantum statistical ensemble with finite Hagedorn temperature. The relation to a \k-deformed Schrödinger quantum mechanics in which the time derivative is replaced by a finite difference derivative is also discussed.

hep-th↗

arXiv1991

Real Forms of Complex Quantum Anti de Sitter Algebra $U_q (Sp(4,C))$ and their Contraction Schemes

We describe four types of inner involutions of the Cartan-Weyl basis providing (for $ |q|=1$ and $q$ real) three types of real quantum Lie algebras: $U_{q}(O(3,2))$ (quantum D=4 anti-de-Sitter), $U_{q}(O(4,1))$ (quantum D=4 de-Sitter) and $U_{q}(O(5))$. We give also two types of inner involutions of the Cartan-Chevalley basis of $U_{q}(Sp(4;C))$ which can not be extended to inner involutions of the Cartan-Weyl basis. We outline twelve contraction schemes for quantum D=4 anti-de-Sitter algebra. All these contractions provide four commuting translation generators, but only two (one for $ |q|=1$, second for $q$ real) lead to the quantum \po algebra with an undeformed space rotations O(3) subalgebra.

hep-th↗