Gravity, antimatter and the Dirac-Milne universe

TL;DR

This paper explores the possibility of antimatter experiencing gravity differently, proposes the Dirac-Milne universe as an alternative cosmology, and discusses experimental tests at CERN to validate these ideas.

Contribution

It introduces the Dirac-Milne cosmology as a symmetric matter-antimatter model and examines its implications for structure formation and fundamental physics.

Findings

Violations of the Equivalence Principle with negative mass particles

Dirac-Milne universe shows similarities with our universe in key cosmological parameters

Upcoming CERN experiments could test antimatter gravity properties

Abstract

We review the main arguments against antigravity, a different acceleration of antimatter relative to matter in a gravitational field, discussing and challenging Morrison's, Good's and Schiff's arguments. Following Price, we show that, very surprisingly, the usual expression of the Equivalence Principle is violated by General Relativity when particles of negative mass are supposed to exist, which may provide a fundamental explanation of MOND phenomenology, obviating the need for Dark Matter. Motivated by the observation of repulsive gravity under the form of Dark Energy, and by the fact that our universe looks very similar to a coasting (neither decelerating nor accelerating) universe, we study the Dirac-Milne cosmology, a symmetric matter-antimatter cosmology where antiparticles have the same gravitational properties as holes in a semiconductor. Noting the similarities with our universe (age, SN1a luminosity distance, nucleosynthesis, CMB angular scale), we focus our attention on structure formation mechanisms, finding strong similarities with our universe. Additional tests of the Dirac-Milne cosmology are briefly reviewed, and we finally note that a crucial test of the Dirac-Milne cosmology will be soon realized at CERN next to the ELENA antiproton decelerator, possibly as early as fall 2018, with the AEgIS, ALPHA-g and Gbar antihydrogen gravity experiments.