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

Nonlinear absorption of ultrashort laser pulses in thin metal films

Self-consistent simulations of the ultrafast electron dynamics in thin metal films are performed. A regime of nonlinear oscillations is observed, which corresponds to ballistic electrons bouncing back and forth against the film surfaces. When an oscillatory laser field is applied to the film, the field energy is partially absorbed by the electron gas. Maximum absorption occurs when the period of the external field matches the period of the nonlinear oscillations, which, for sodium films, lies in the infrared range. Possible experimental implementations are discussed.Comment: 3 pages, to appear in Optics Letters, vol.30, n.22 (2005

Adiabatic cooling of trapped nonneutral plasmas

Nonneutral plasmas can be trapped for long times by means of combined electric and magnetic fields. Adiabatic cooling is achieved by slowly decreasing the trapping frequency and letting the plasma occupy a larger volume. We develop a fully kinetic time-dependent theory of adiabatic cooling for plasmas trapped in a one-dimensional well. This approach is further extended to three dimensions and applied to the cooling of antiproton plasmas, showing excellent agreement with recent experiments [G. Gabrielse et al., Phys. Rev. Lett. 106, 073002 (2011)].Comment: To appear in Physical Review Letter

Organic & Hybrid Photonic Crystals for Controlling Light-Matter Interaction Processes

Organic & Hybrid Photonic Crystals for Controlling Light-Matter Interaction Processe

Preface to Special Topic: Plasmonics and solid state plasmas

International audienc

Non-relativistic limits of Maxwell's equations

In 1973, Le Bellac and Levy-Leblond (Nuovo Cimento B 14, 217-234) discovered that Maxwell's equations possess two non-relativistic Galilei-covariant limits, corresponding to E >> cB (electric limit) or E << cB (magnetic limit). Here, we provide a systematic, yet simple, derivation of these two limits based on a dimensionless form of Maxwell's equations and an expansion of the electric and magnetic fields in a power series of some small parameters. Using this procedure, all previously known results are recovered in a natural and unambiguous way. Some further extensions are also proposed