79 research outputs found
Tidal gravitational effects in a satellite
Atomic wave interferometers are tied to a telescope pointing towards a
faraway star in a nearly free falling satellite. Such a device is sensitive to
the acceleration and the rotation relatively to the local inertial frame and to
the tidal gravitational effects too. We calculate the rotation of the telescope
due to the aberration and the deflection of the light in the gravitational
field of a central mass (the Earth and Jupiter). Within the framework of a
general parametrized description of the problem, we discuss the contributions
which must be taken into account in order to observe the Lense-Thirring effect.
Using a geometrical model, we consider some perturbations to the idealized
device and we calculate the corresponding effect on the periodic components of
the signal. Some improvements in the knowledge of the gravitational field are
still necessary as well as an increase of the experimental capabilities;
however our conclusions support a reasonable optimism for the future. Finally
we put forward the necessity of a more complete, realistic and powerful model
in order to obtain a definitive conclusion on the feasibility of the experiment
as far as the observation of the Lense-Thirring effect is involved.Comment: accepted to General Relativity and Gravitatio
Lifetimes of atoms trapped in an optical lattice in proximity of a surface
We study the lifetime of an atom trapped in an optical vertical lattice in
proximity of a massive surface using a complex scaling approach. We analyze how
the presence of the surface modifies the known lifetimes of Wannier-Stark
states associated to Landau-Zener tunnelling. We also investigate how the
existence of a hypothetical short-distance deviation from Newton's
gravitational law could affect these lifetimes. Our study is relevant in order
to discuss the feasibility of any atomic- interferometry experiment performed
near a surface. Finally, the difficulties encountered in applying the
complex-scaling approach to the atom-surface Casimir-Polder interaction are
addressed.Comment: 10 pages, 8 figure
THE ''FORGOTTEN'' PROCESS : the emission stimulated by matter waves.
submitted in European Journal of PhysicsIn a famous paper where he introduces the A and B coefficients, Einstein considered that atomic decays of excited atoms can be stimulated by light waves. Here we consider that atomic decays can also be stimulated by atomic waves. It is however necessary to change the Maxwell-Boltzmann statistics of thermal equilibrium into Bose-Einstein statistics and to introduce a coefficient C which complements the list of the coefficients introduced by Einstein. Stimulated emission of light can be considered as the first step towards the laser. Similarly, stimulated production of matter waves can be considered as the basic phenomenon for an atom-laser. Most of the results that we obtain here are not new. However, the method that we use remains very close to elementary classical physics and emphasizes the symmetry between electromagnetic and matter waves from various points of view
Time Transfer functions as a way to validate light propagation solutions for space astrometry
Given the extreme accuracy of modern space astrometry, a precise relativistic
modeling of observations is required. Concerning light propagation, the
standard procedure is the solution of the null-geodesic equations. However,
another approach based on the Time Transfer Functions (TTF) has demonstrated
its capability to give access to key quantities such as the time of flight of a
light signal between two point-events and the tangent vector to its
null-geodesic in a weak gravitational field using an integral-based method. The
availability of several models, formulated in different and independent ways,
must not be considered like an oversized relativistic toolbox. Quite the
contrary, they are needed as validation to put future experimental results on
solid ground. The objective of this work is then twofold. First, we build the
time of flight and tangent vectors in a closed form within the TTF formalism
giving the case of a time dependent metric. Second, we show how to use this new
approach to obtain a comparison of the TTF with two existing modelings, namely
GREM and RAMOD. In this way, we evidentiate the mutual consistency of the three
models, opening the basis for further links between all the approaches, which
is mandatory for the interpretation of future space missions data. This will be
illustrated through two recognized cases: a static gravitational field and a
system of monopoles in uniform motion.Comment: 16 pages, submitted to CQ
Dynamical aspects of atom interferometry in an optical lattice in proximity of a surface
The efficiency of an atomic interferometer in proximity of a surface is
discussed. We first study which is the best choice of frequency for a pulse
acting on internal atomic transitions in the same well. Then considering the
modification of atomic energy levels in vicinity of the surface, we propose the
application of two simultaneous Raman lasers and numerically study the
associated interference fringes. We show that the efficiency of the
interferometric scheme is limited by the existence of a residual phase
depending on the atomic path. We propose a symmetric scheme in order to avoid
these contributions. We finally show that the suggested modifications make the
contrast of the interference fringes close to 1 in any configuration, both
close and far from the surface and with one or more initially populated wells.Comment: 8 pages, 9 figure
Atomic states in optical traps near a planar surface
In this work we discuss the atomic states in a vertical optical lattice in
proximity of a surface. We study the modifications to the ordinary
Wannier-Stark states in presence of a surface and we characterize the energy
shifts produced by the Casimir-Polder interaction between atom and mirror. In
this context, we introduce an effective model describing the finite size of the
atom in order to regularize the energy corrections. In addition, the
modifications to the energy levels due to a hypothetical non-Newtonian
gravitational potential as well as their experimental observability are
investigated.Comment: 12 pages, 8 figure
Extended Fermi coordinates
We extend the notion of Fermi coordinates to a generalized definition in
which the highest orders are described by arbitrary functions. From this
definition rises a formalism that naturally gives coordinate transformation
formulae. Some examples are developped in which the extended Fermi coordinates
simplify the metric components.Comment: 16 pages, 1 figur
iSense: a technology platform for cold atom based quantum technologies
A breakthrough in cold atom quantum technology is hindered by a bottleneck in the supporting technologies. We discuss a cold atom technology platform developed within the European iSense project, aiming at a gravimeter as demonstrator
Quelques études de gravitation observationnelle et expérimentale
Some studies of observational and experimental gravitationCette habilitation présente mes travaux de gravitation observationnelle et expérimentale
- …