Mainz 2004 – scientific programme

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T: Teilchenphysik

T 605: Vermischtes

T 605.1: Talk

Thursday, April 1, 2004, 10:30–10:45, HS VI

Spacetime foam, CPT anomaly, and photon propagation — •Christian Rupp and Frans R. Klinkhamer — Institut für Theoretische Physik, Universität Karlsruhe

The CPT anomaly of chiral gauge theories has been established previously for multiply connected spacetime manifolds M of the type R³ × S¹, where the noncontractible loops have a minimal length. We show that the CPT anomaly also occurs for manifolds where the noncontractible loops can be arbitrarily small. Our basic calculation is performed for a flat noncompact manifold with a single “puncture,” namely M=R² × (R² ∖ {0}). A hypothetical spacetime foam might have many such punctures. Assuming the multiply connected structure of the foam to be time independent, we present a simple model for photon propagation, which generalizes the single-puncture result. This model leads to a modified dispersion law of the photon. Observations of high-energy photons (gamma-rays) from explosive extragalactic events can then be used to place an upper bound on the typical length scale of these punctures.