Hendrik van Dam

Implications of spacetime quantization for the Bahcall–Waxman neutrino bound

There is growing interest in quantum-spacetime models in which small departures from Lorentz symmetry are governed by the Planck scale. In particular, several studies have considered the possibility that these small violations of Lorentz symmetry may affect various astrophysical observations, such as the evaluation of the GZK limit for cosmic rays, the interaction of TeV photons with the far infrared background and the arrival time of photons with different energies from cosmological sources. We show that the same Planck-scale departures from Lorentz symmetry that led to a modification of the GZK limit also have significant implications for the evaluation of the Bahcall–Waxman bound on the flux of high-energy neutrinos produced by photo–meson interactions.

Anomalies and fermion masses in D dimensions

Abstract We show that anomalies in D spacetime dimensions are generated by only massless fermions, and note that the manner in which the anomalies of massive fermions cancel is qualitatively different in the two cases D ≡ 2 and D ≡ 0 (mod 4).

A GENERALIZATION OF QUANTUM STATISTICS

We examine a new fractional statistics for arbitrary dimensions, based on an extension of Pauli’s exclusion principle, to allow for finite multi-occupancies of a single quantum state. By explicitly constructing the many-body Hilbert space, we obtain a new algebra of operators and a new thermodynamics. The new statistics is different from fractional exclusion statistics. For a single species of particles it is equivalent to parafermi statistics; but their algebras are very different for the case of multiple species.

Possible solution of strong CP problem in generalized unimodular gravity

It was recently pointed out how constrained gravitational dynamics offers a possible solution of the cosmological constant problem at the quantum level. Here we point out that the same theory may be used to solve the strong CP problem without recourse to wormholes or to the introduction of any new particle.