D-Foam Phenomenology: Dark Energy, the Velocity of Light and a Possible D-Void

TL;DR

This paper explores a D-brane space-time foam model linking dark energy, photon velocity retardation, and a possible D-void, proposing a phenomenological connection with astrophysical observations and addressing potential cosmological implications.

Contribution

It introduces a D-foam phenomenology framework that connects dark energy density, photon speed retardation, and D-particle density variations over cosmic time.

Findings

Dark energy contributions depend on D-brane velocities and D-particle density.

Photon speeds may be linearly reduced by D-particles, affecting astrophysical measurements.

A D-void could reconcile different observational data on photon retardation.

Abstract

In a D-brane model of space-time foam, there are contributions to the dark energy that depend on the D-brane velocities and on the density of D-particle defects. The latter may also reduce the speeds of photons linearly with their energies, establishing a phenomenological connection with astrophysical probes of the universality of the velocity of light. Specifically, the cosmological dark energy density measured at the present epoch may be linked to the apparent retardation of energetic photons propagating from nearby AGNs. However, this nascent field of `D-foam phenomenology' may be complicated by a dependence of the D-particle density on the cosmological epoch. A reduced density of D-particles at redshifts z ~ 1 - a `D-void' - would increase the dark energy while suppressing the vacuum refractive index, and thereby might reconcile the AGN measurements with the relatively small retardation seen for the energetic photons propagating from GRB 090510, as measured by the Fermi satellite.