Arnaud Dupays

Proton Zemach radius from measurements of the hyperfine splitting of hydrogen and muonic hydrogen

While measurements of the hyperfine structure of hydrogen-like atoms are traditionally regarded as test of bound-state QED, we assume that theoretical QED predictions are accurate and discuss the information about the electromagnetic structure of protons that could be extracted from the experimental values of the ground state hyperfine splitting in hydrogen and muonic hydrogen.Using recent theoretical results on the proton polarizability effects and the experimentalhydrogen hyperfine splitting we obtain for the Zemach radius of the proton the value 1.040(16) fm. We compare it to the various theoretical estimatesthe uncertainty of which is shown to be larger that 0.016 fm.This point of view gives quite convincing arguments in support of projects to measure the hyperfine splitting of muonic hydrogen.

Looking for Light Pseudoscalar Bosons in the Binary Pulsar System J0737-3039

We present numerical calculations of the photon-light-pseudoscalar-boson (LPB) production in the recently discovered binary pulsar system J0737-3039. Light pseudoscalar bosons oscillate into photons in the presence of strong magnetic fields. In the context of this binary pulsar system, this phenomenon attenuates the light beam emitted by one of the pulsars, when the light ray goes through the magnetosphere of the companion pulsar. We show that such an effect is observable in the gamma-ray band since the binary pulsar is seen almost edge-on, depending on the values of the LPB mass and on the strength of its two-photon coupling. Our results are surprising in that they show a very sharp and significant (up to 50%) transition probability in the gamma-ray (> tens of MeV) domain. The observations can be performed by the upcoming NASA GLAST mission.

Light scalars coupled to photons and non-newtonian forces.

A particle phi coupling to two photons couples also radiatively to charged particles, like protons. If the particle is a light scalar, this induced coupling leads to spin-independent non-Newtonian forces. We show that the experimental constraints on exotic, fifth-type forces lead to stringent constraints on the phigammagamma coupling. We discuss the impact on the recent PVLAS results and the role of paraphoton models introduced to solve the PVLAS-CAST puzzle.

Quantum Vacuum Friction in highly magnetized neutron stars

In this letter we calculate the energy loss of a highly magnetized neutron star due to Quantum Vacuum Friction (QVF). Taking into account one-loop corrections in the effective Heisenberg-Euler Lagrangian of the light-light interaction, we derive an analytic expression for QVF allowing us to take into account a magnetic field at the surface of the star as high as 1011 T. In the case of magnetars, with magnetic fields above the QED critical field, we show that the QVF is the dominating energy loss process. This has important consequences, in particular for the inferred value of the magnetic field. This also indicates the need for independent measurements of magnetic field, energy loss rate, and the braking index in order to fully characterize magnetars.

Is cosmic acceleration proven by local cosmological probes

Context: The cosmological concordance model (

Birefringence of interferential mirrors at normal incidence: Experimental and computational study

\Lambda

Quantum vacuum influence on pulsars spindown evolution

CDM) matches the cosmological observations exceedingly well. This model has become the standard cosmological model with the evidence for an accelerated expansion provided by the type Ia supernovae (SNIa) Hubble diagram. However, the robustness of this evidence has been addressed recently with somewhat diverging conclusions. Aims: The purpose of this paper is to assess the robustness of the conclusion that the Universe is indeed accelerating if we rely only on low-redshift (z

Observing Quantum Vacuum Lensing in a Neutron Star Binary System

\lesssim

Power law cosmology model comparison with CMB scale information

2) observations, that is to say with SNIa, baryonic acoustic oscillations, measurements of the Hubble parameter at different redshifts, and measurements of the growth of matter perturbations. Methods: We used the standard statistical procedure of minimizing the

Inverse Cotton-Mouton effect of the Vacuum and of atomic systems

\chi^2