The exploration of the universe has recently entered a new era thanks to the multi-
messenger paradigm, characterized by a continuous increase in the quantity and quality of …

We review open questions and prospects for progress in ultrahigh-energy cosmic ray
(UHECR) research, based on a series of discussions that took place during the “The High …

The present white paper is submitted as part of the “Snowmass” process to help inform the
long-term plans of the United States Department of Energy and the National Science …

I show that it is possible to formulate the Relativity postulates in a way that does not lead to
inconsistencies in the case of spacetimes whose short-distance structure is governed by an …

We propose a modification of special relativity in which a physical energy, which may be the
Planck energy, joins the speed of light as an invariant, in spite of a complete relativity of …

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 …

I propose a general class of spacetimes whose structure is governed by observer-
independent scales of both velocity (c) and length (Planck length), and I observe that these …

The hypothesis that the Lorentz transformations may be modified at Planck scale energies is
further explored. We present a general formalism for theories which preserve the relativity of …

Nonlinear special relativity (or doubly special relativity) is a simple framework for encoding
properties of flat quantum spacetime. In this paper, we show how this formalism may be …