On Possible Measurement of Gravitational Interaction Parameters on Board a Satellite

The recently suggested SEE (Satellite Energy Exchange) method of measuring the gravitational constant $G$, possible equivalence principle violation (measured by the E\"{o}tv\"{o}s parameter $\eta$) and the hypothetic 5th force parameters $\alpha$ and $\lambda$ on board a drag-free Earth's satellite is discussed and further developed. Various particle trajectories near a heavy ball are numerically simulated. Some basic sources of error are analysed. The $G$ measurement procedure is modelled by noise insertion to a ``true'' trajectory. It is concluded that the present knowledge of $G, \alpha$ (for $\lambda \geq 1$ m) and $\eta$ can be improved by at least two orders of magnitude.Comment: (only two misprints on title page) 7 page

Anharmonic coherent dynamics of the soft phonon mode of a PbTe crystal

We investigate the ultrafast optical response of PbTe to an intense single-cycle terahertz pulse, resonant with the soft transverse optical (TO) phonon mode of the crystal. We detect multifrequency oscillations of the reflectance anisotropy, which we associate with nonlinear motion of the TO phonon oscillator excited directly by the terahertz pulse. Our observation of monotonically decaying optical anisotropy together with second harmonic oscillations of the TO mode is an evidence of a transient non-centrosymmetric state of the crystal lattice that can be accompanied by the ferroelectric order. We suppose that this state is induced in the PbTe crystal by the intense terahertz pulse via alignment of the local polar nanodomains. This hypothesis is partially supported by the observation of coherent phonons near the satellite phonon mode frequency that are impulsively generated by a femtosecond laser pulse and are considerably enhanced by a synchronous terahertz pulse.Comment: 7 pages, 5 figure