1,522 research outputs found

### Gravity tests in the solar system and the Pioneer anomaly

We build up a new phenomenological framework associated with a minimal
generalization of Einsteinian gravitation theory. When linearity, stationarity
and isotropy are assumed, tests in the solar system are characterized by two
potentials which generalize respectively the Newton potential and the parameter
$\gamma$ of parametrized post-Newtonian formalism. The new framework seems to
have the capability to account for the Pioneer anomaly besides other gravity
tests.Comment: 5 pages. Accepted version, to appear in Modern Physics Letters

### Quantum Limits in Space-Time Measurements

Quantum fluctuations impose fundamental limits on measurement and space-time
probing. Although using optimised probe fields can allow to push sensitivity in
a position measurement beyond the "standard quantum limit", quantum
fluctuations of the probe field still result in limitations which are
determined by irreducible dissipation mechanisms. Fluctuation-dissipation
relations in vacuum characterise the mechanical effects of radiation pressure
vacuum fluctuations, which lead to an ultimate quantum noise for positions. For
macroscopic reflectors, the quantum noise on positions is dominated by
gravitational vacuum fluctuations, and takes a universal form deduced from
quantum fluctuations of space-time curvatures in vacuum. These can be
considered as ultimate space-time fluctuations, fixing ultimate quantum limits
in space-time measurements.Comment: 11 pages, to appear in Quantum and Semiclassical Optic

### Frequency up-converted radiation from a cavity moving in vacuum

We calculate the photon emission of a high finesse cavity moving in vacuum.
The cavity is treated as an open system. The field initially in the vacuum
state accumulates a dephasing depending on the mirrors motion when bouncing
back and forth inside the cavity. The dephasing is not linearized in our
calculation, so that qualitatively new effects like pulse shaping in the time
domain and frequency up-conversion in the spectrum are found. Furthermore we
predict the existence of a threshold above which the system should show
self-sustained oscillations.Comment: 10 pages, 3 figures, LaTeX, to appear in European Physical Journal
D3, replaced version with few minor grammatical change

### Generating photon pulses with an oscillating cavity

We study the generation of photon pulses from thermal field fluctuations
through opto-mechanical coupling to a cavity with an oscillatory motion. Pulses
are regularly spaced and become sharp for a high finesse cavity.Comment: 6 pages, 3 figures, LaTeX, needs EuroPhysics Letters Stylefile, to
appear in Europhysics Letter

### Constraints on $f(R_{ijkl}R^{ijkl})$ gravity: An evidence against the covariant resolution of the Pioneer anomaly

We consider corrections in the form of $\Delta L(R_{ijkl}R^{ijkl})$ to the
Einstein-Hilbert Lagrangian. Then we compute the corrections to the
Schwarszchild geometry due to the inclusion of this general term to the
Lagrangian. We show that $\Delta L_3=\alpha_{{1/3}}(R_{ijkl}R^{ijkl})^{{1/3}}$
gives rise to a constant anomalous acceleration for objects orbiting the Sun
onward the Sun. This leads to the conclusion that $\alpha_{{1/3}}=(13.91\pm
2.11) \times 10^{-26}(\frac{1}{\text{meters}})^{{2/3}}$ would have covariantly
resolved the Pioneer anomaly if this value of $\alpha_{{1/3}}$ had not
contradicted other observations.
We notice that the experimental bounds on $\Delta L_3$ grows stronger in case
we examine the deformation of the space-time geometry around objects lighter
than the Sun. We therefore use the high precision measurements around the Earth
(LAGEOS and LLR) and obtain a very strong constraint on the corrections in the
form of $\Delta L(R_{ijkl}R^{ijkl})$ and in particular $\Delta
L=\alpha_n(R_{ijkl}R^{ijkl})^n$. This bound requires
$\alpha_{{1/3}}\leq6.12\times 10^{-29}(\frac{1}{\text{meters}})^{{2/3}}$.
Therefore it refutes the covariant resolution of the Pioneer anomaly.Comment: ...v5: references added, new discussions adde

### Testing gravity law in the solar system

The predictions of General relativity (GR) are in good agreement with
observations in the solar system. Nevertheless, unexpected anomalies appeared
during the last decades, along with the increasing precision of measurements.
Those anomalies are present in spacecraft tracking data (Pioneer and flyby
anomalies) as well as ephemerides. In addition, the whole theory is challenged
at galactic and cosmic scales with the dark matter and dark energy issues.
Finally, the unification in the framework of quantum field theories remains an
open question, whose solution will certainly lead to modifications of the
theory, even at large distances. As long as those "dark sides" of the universe
have no universally accepted interpretation nor are they observed through other
means than the gravitational anomalies they have been designed to cure, these
anomalies may as well be interpreted as deviations from GR. In this context,
there is a strong motivation for improved and more systematic tests of GR
inside the solar system, with the aim to bridge the gap between gravity
experiments in the solar system and observations at much larger scales. We
review a family of metric extensions of GR which preserve the equivalence
principle but modify the coupling between energy and curvature and provide a
phenomenological framework which generalizes the PPN framework and "fifth
force" extensions of GR. We briefly discuss some possible observational
consequences in connection with highly accurate ephemerides.Comment: Proceedings of Journ\'ees 2010 "Syst\`emes de r\'ef\'erence
spatio-temporels", New challenges for reference systems and numerical
standards in astronom

### Test of Guttmann and Enting's conjecture in the eight-vertex model

We investigate the analyticity property of the partially resummed series
expansion(PRSE) of the partition function for the eight-vertex model.
Developing a graphical technique, we have obtained a first few terms of the
PRSE and found that these terms have a pole only at one point in the complex
plane of the coupling constant. This result supports the conjecture proposed by
Guttmann and Enting concerning the ``solvability'' in statistical mechanical
lattice models.Comment: 15 pages, 3 figures, RevTe

### Motion Induced Radiation from a Vibrating Cavity

We study the radiation emitted by a cavity moving in vacuum. We give a
quantitative estimate of the photon production inside the cavity as well as of
the photon flux radiated from the cavity. A resonance enhancement occurs not
only when the cavity length is modulated but also for a global oscillation of
the cavity. For a high finesse cavity the emitted radiation surpasses radiation
from a single mirror by orders of magnitude.Comment: 4 pages, to appear in Physical Review Letter

### Vacuum fluctuations, accelerated motion and conformal frames

Radiation from a mirror moving in vacuum electromagnetic fields is shown to
vanish in the case of a uniformly accelerated motion. Such motions are related
to conformal coordinate transformations, which preserve correlation functions
characteristic of vacuum fluctuations. As a result, vacuum fluctuations remain
invariant under reflection upon a uniformly accelerated mirror, which therefore
does not radiate and experiences no radiation reaction force. Mechanical
effects of vacuum fluctuations thus exhibit an invariance with respect to
uniformly accelerated motions.Comment: 7 page

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