Motivated by ideas about quantum gravity, a tremendous amount of effort over the past
decade has gone into testing Lorentz invariance in various regimes. This review …

I review the current status of phenomenological programs inspired by quantum-spacetime
research. I stress in particular the significance of results establishing that certain data …

Stability and causality are investigated for quantum field theories incorporating Lorentz and
CPT violation. Explicit calculations in the quadratic sector of a general renormalizable …

We review recent work on the possibility of a varying speed of light (VSL). We start by
discussing the physical meaning of a varying-c, dispelling the myth that the constancy of c is …

We consider the gravitational effects of a single, fixed-norm, Lorentz-violating timelike vector
field. In a cosmological background, such a vector field acts to rescale the effective value of …

One of the most puzzling current experimental physics paradoxes is the arrival on Earth of
ultrahigh energy cosmic rays (UHECRs) with energies above the Greisen-Zatsepin-Kuzmin …

Recent work has shown that dispersion relations with Planck scale Lorentz violation can
produce observable effects at energies many orders of magnitude below the Planck energy …

In the first part of this review we discuss the basic observational features at the end of the
cosmic ray (CR) energy spectrum. We also present there the main characteristics of each of …

In this review we discuss the important progress made in recent years towards
understanding the experimental data on cosmic rays with energies≳ 1019 eV. We begin …

In the context of threshold investigations of Lorentz violation, we discuss the fundamental
principle of coordinate independence, the role of an effective dynamical framework, and the …