Gravity, antimatter and the Dirac-Milne universe

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.Comment: Proceedings of the Low Energy Antiproton Physics Conference (LEAP), Sorbonne University, Paris, March 12th to 16th, 201

Experimental and observational tests of antigravity

Whereas repulsive gravity was considered as a fringe concept until the mid-1990's, the growingexperimental evidence since this epoch for repulsive gravity, in what is now called Dark Energy,for lack of a better understanding of its nature, has led to a vast literature in order to attemptto characterize this repulsive component, and notably its equation of state. In the following, Iwill show that we can use cosmology to test the hypothesis that antimatter is at the origin ofrepulsive gravity, may play the role of a Dark Energy component and, more surprisingly, maymimic the presence of Dark Matter, and justify the MOND phenomenology. More directly,three experiments, AEgIS, ALPHA-g and Gbar, are attempting to measure the action ofgravitation on cold atoms of antihydrogen at CERN in a near future. Finally, I note thatCP violation might be explained by antigravity and I briefly recall the motivations for thisassertion.Comment: 33rd Rencontres de Blois: Exploring the Dark Universe, May 2022, Blois, Franc

Dark Matter Direct Detection

Solving the Dark Matter enigma represents one of the key objectives of contemporary physics. Recent astrophysical and cosmological measurements have unambiguously demonstrated that ordinary matter contributes to less than 5 % of the energy budget of our Universe, and that the nature of the remaining 95 % is unknown. Weakly Interacting Massive Particles (WIMPs) represent the best motivated candidate to fill the Dark Matter gap, and direct detection Dark Matter experiments have recently reached sensitivities allowing them to sample a first part of supersymmetric models compatible with accelerator constraints. Three cryogenic experiments currently provide the best sensitivity, by nearly one order of magnitude, to WIMP interactions. With systematic uncertainties far less severe than other present techniques, the next generation of cryogenic experiments promises two orders of magnitude increase in sensitivity over the next few years. The present results, perspectives and experimental strategies of the main direct detection experiments are presented. Challenges met by future ton-scale cryogenic experiments in deep underground sites, aiming at testing most of the SUSY parameter space, are critically discussed.Comment: 46 pages, 17 figures, to appear in "Cryogenic Particle Detection", edited by Christian Enss, (Springer, Heidelberg, 2005) ; one figure and two references modified ; typographical correction

Status and Perspectives of Direct Dark Matter Searches

Supersymmetric particles represent the best motivated candidates to fill the Dark Matter gap, and are actively hunted by a number of competing experiments. Discriminating experiments are testing for the first time SUSY models compatible with accelerator constraints. These experiments contradict the 60 GeV WIMP candidate reported by the DAMA experiment. The sensitivities of direct and indirect detection techniques for both present experiments and future projects are compared

Experimental and observational tests of antigravity

International audienceWhereas repulsive gravity was considered as a fringe concept until the mid-1990's, the growingexperimental evidence since this epoch for repulsive gravity, in what is now called Dark Energy,for lack of a better understanding of its nature, has led to a vast literature in order to attemptto characterize this repulsive component, and notably its equation of state. In the following, Iwill show that we can use cosmology to test the hypothesis that antimatter is at the origin ofrepulsive gravity, may play the role of a Dark Energy component and, more surprisingly, maymimic the presence of Dark Matter, and justify the MOND phenomenology. More directly,three experiments, AEgIS, ALPHA-g and Gbar, are attempting to measure the action ofgravitation on cold atoms of antihydrogen at CERN in a near future. Finally, I note thatCP violation might be explained by antigravity and I briefly recall the motivations for thisassertion

Experimental and observational tests of antigravity

International audienceWhereas repulsive gravity was considered as a fringe concept until the mid-1990's, the growingexperimental evidence since this epoch for repulsive gravity, in what is now called Dark Energy,for lack of a better understanding of its nature, has led to a vast literature in order to attemptto characterize this repulsive component, and notably its equation of state. In the following, Iwill show that we can use cosmology to test the hypothesis that antimatter is at the origin ofrepulsive gravity, may play the role of a Dark Energy component and, more surprisingly, maymimic the presence of Dark Matter, and justify the MOND phenomenology. More directly,three experiments, AEgIS, ALPHA-g and Gbar, are attempting to measure the action ofgravitation on cold atoms of antihydrogen at CERN in a near future. Finally, I note thatCP violation might be explained by antigravity and I briefly recall the motivations for thisassertion

Experimental and observational tests of antigravity

International audienceWhereas repulsive gravity was considered as a fringe concept until the mid-1990's, the growingexperimental evidence since this epoch for repulsive gravity, in what is now called Dark Energy,for lack of a better understanding of its nature, has led to a vast literature in order to attemptto characterize this repulsive component, and notably its equation of state. In the following, Iwill show that we can use cosmology to test the hypothesis that antimatter is at the origin ofrepulsive gravity, may play the role of a Dark Energy component and, more surprisingly, maymimic the presence of Dark Matter, and justify the MOND phenomenology. More directly,three experiments, AEgIS, ALPHA-g and Gbar, are attempting to measure the action ofgravitation on cold atoms of antihydrogen at CERN in a near future. Finally, I note thatCP violation might be explained by antigravity and I briefly recall the motivations for thisassertion