309 research outputs found
Constraining axion-nucleon coupling constants from measurements of effective Casimir pressure by means of micromachined oscillator
Stronger constraints on the pseudoscalar coupling constants of an axion to a
proton and a neutron are obtained from an indirect measurement of the effective
Casimir pressure between two Au-coated plates by means of micromechanical
torsional oscillator. For this purpose, the additional effective pressure due
to two-axion exchange is calculated. The role of boundary effects and the
validity region of the proximity force approximation in application to forces
of axion origin are determined. The obtained constraints are up to factors of
380 and 3.15 stronger than those found recently from other laboratory
experiments and are relevant to axion masses from eV to 15eV.Comment: 8 pages, 2 figures, 2 tables; several additions have been made in
accordance with version accepted for publication in Eur. Phys. J.
Remarks on some vacuum solutions of scalar-tensor cosmological models
We present a class of exact vacuum solutions corresponding to de Sitter and
warm inflation models in the framework of scalar-tensor cosmologies. We show
that in both cases the field equations reduce to planar dynamical systems with
constraints. Then, we carry out a qualitative analysis of the models by
examining the phase diagrams of the solutions near the equilibrium points.Comment: 12 pages, 4 figures. To be published in the Brazilian Journal of
Physic
Global aspects of gravitomagnetism
We consider global properties of gravitomagnetism by investigating the
gravitomagnetic field of a rotating cosmic string. We show that although the
gravitomagnetic field produced by such a configuration of matter vanishes
locally, it can be detected globally. In this context we discuss the
gravitational analogue of the Aharonov-Bohm effect.Comment: 10 pages - Typeset using REVTE
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