# Extra dimensions and Lorentz invariance violation

## TL;DR

This paper explores how interactions between photons and scalar fields from extra dimensions can modify photon dispersion relations, leading to energy-dependent velocities, and proposes using gamma-ray burst observations to constrain these effects.

## Contribution

It introduces a model where photon interactions with internal space scalar fields cause Lorentz invariance violation and derives observational constraints from GRB time delays.

## Key findings

- Photon dispersion relations are modified by scalar field interactions.
- Photon group velocity depends on energy, causing time delays.
- Experimental bounds from GRB observations constrain the model parameters.

## Abstract

We consider effective model where photons interact with scalar field corresponding to conformal excitations of the internal space (geometrical moduli/gravexcitons). We demonstrate that this interaction results in a modified dispersion relation for photons, and consequently, the photon group velocity depends on the energy implying the propagation time delay effect. We suggest to use the experimental bounds of the time delay of gamma ray bursts (GRBs) photons propagation as an additional constrain for the gravexciton parameters.