1,165 research outputs found
Observables in theories with a varying fine structure constant
We show how two seemingly different theories with a scalar multiplicative
coupling to electrodynamics are actually two equivalent parametrisations of the
same theory: despite some differences in the interpretation of some
phenemenological aspects of the parametrisations, they lead to the same
physical observables. This is illustrated on the interpretation of observations
of the Cosmic Microwave Background.Comment: 14 pages, matched published versio
Breaking of the equivalence principle in the electromagnetic sector and its cosmological signatures
This paper proposes a systematic study of cosmological signatures of
modifications of gravity via the presence of a scalar field with a
multiplicative coupling to the electromagnetic Lagrangian. We show that, in
this framework, variations of the fine structure constant, violations of the
distance duality relation, evolution of the cosmic microwave background (CMB)
temperature and CMB distortions are intimately and unequivocally linked. This
enables one to put very stringent constraints on possible violations of the
distance duality relation, on the evolution of the CMB temperature and on
admissible CMB distortions using current constraints on the fine structure
constant. Alternatively, this offers interesting possibilities to test a wide
range of theories of gravity by analysing several datasets concurrently. We
discuss results obtained using current data as well as some forecasts for
future data sets such as those coming from EUCLID or the SKA.Comment: 14 pages, 4 figures, matched published version. Note: title changed
upon suggestion of PRD editor
Frequency shift up to the 2-PM approximation
A lot of fundamental tests of gravitational theories rely on highly precise
measurements of the travel time and/or the frequency shift of electromagnetic
signals propagating through the gravitational field of the Solar System. In
practically all of the previous studies, the explicit expressions of such
travel times and frequency shifts as predicted by various metric theories of
gravity are derived from an integration of the null geodesic differential
equations. However, the solution of the geodesic equations requires heavy
calculations when one has to take into account the presence of mass multipoles
in the gravitational field or the tidal effects due to the planetary motions,
and the calculations become quite complicated in the post-post-Minkowskian
approximation. This difficult task can be avoided using the time transfer
function's formalism. We present here our last advances in the formulation of
the one-way frequency shift using this formalism up to the
post-post-Minkowskian approximation.Comment: 4 pages, submitted to proceedings of SF2
Light propagation in the field of a moving axisymmetric body: theory and application to JUNO
Given the extreme accuracy of modern space science, a precise relativistic
modeling of observations is required. We use the Time Transfer Functions
formalism to study light propagation in the field of uniformly moving
axisymmetric bodies, which extends the field of application of previous works.
We first present a space-time metric adapted to describe the geometry of an
ensemble of uniformly moving bodies. Then, we show that the expression of the
Time Transfer Functions in the field of a uniformly moving body can be easily
derived from its well-known expression in a stationary field by using a change
of variables. We also give a general expression of the Time Transfer Function
in the case of an ensemble of arbitrarily moving point masses. This result is
given in the form of an integral easily computable numerically. We also provide
the derivatives of the Time Transfer Function in this case, which are mandatory
to compute Doppler and astrometric observables. We particularize our results in
the case of moving axisymmetric bodies. Finally, we apply our results to study
the different relativistic contributions to the range and Doppler tracking for
the JUNO mission in the Jovian system.Comment: 17 pages, 4 figures, submitted to Phys. Rev. D, some corrections
after revie
Kinetics of the chiral phase transition in a linear model
We study the dynamics of the chiral phase transition in a linear quark-meson
model using a novel approach based on semiclassical wave-particle
duality. The quarks are treated as test particles in a Monte-Carlo simulation
of elastic collisions and the coupling to the meson, which is treated
as a classical field. The exchange of energy and momentum between particles and
fields is described in terms of appropriate Gaussian wave packets. It has been
demonstrated that energy-momentum conservation and the principle of detailed
balance are fulfilled, and that the dynamics leads to the correct equilibrium
limit. First schematic studies of the dynamics of matter produced in heavy-ion
collisions are presented.Comment: 15 pages, 12 figures, accepted by EPJA, dedicated to memory of Walter
Greiner; v2: corrected typos, added references and an acknowledgmen
- …