Spin foam models are the path integral counterparts to loop quantized canonical theories. In the last few years several spin foam models of gravity have been proposed, most of which live on finite simplicial lattice spacetime. The lattice truncates the presumably infinite set of gravitational degrees of freedom down to a finite set. Models that can accomodate an infinite set of degrees of freed...

We compare the Bakamjian-Thomas (BT) formulation of relativistic few-body systems with light front field theories that maintain closer contact with Feynman diagrams. We find that Feynman diagrams distinguish Melosh rotations and other kinematical quantities belonging to various composite subsystem frames that correspond to different loop integrals. The BT formalism knows only the rest frame of ...

A bstract We complete the proof of “Feynman rules” for constructing M -point conformal blocks with external and internal scalars in any topology arbitrary spacetime dimension by combining rules (based on their Witten diagram interpretation) construction cross ratios OPE “flow diagrams”). The full set Feynman leads to as power series hypergeometric type ratios. then provide a recursion which rel...

Symmetrization of bosonic wave functions produces bunching and low temperature phenomena like Bose-Einstein condensation, superfludity, superconductivity, as well as laser. Since probability is conserved, one might expect such bunchings at one place would lead to a depletion or a destructive interference at another place. This indeed takes place in high-energy scatterings, leading to cancellati...

A 3-dimensional model dual to the Rozansky-Witten topological sigma-model with a hyper-Kähler target space is considered. It is demonstrated that a Feynman diagram calculation of the classical part of its partition function yields the Milnor linking number.

xloops is a program package that calculates Feynman diagrams by using computer algebra systems. In this paper it is shown which problems to be solved by computer algebra arise during such calculations, and how this problems are handled in the framework of xloops.

Large Rapidity Gap Events in Deep Inelastic Scattering are discussed in terms of lightcone wave functions for quarks and gluons inside the photon. It is shown that this approach is consistent with earlier, conventional Feynman diagram calculations. An updated parametrization for the cross section is given and a numerical analysis presented.