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Spccific light deflection phenomena are observed in ferroelastic crystals. Above a critical angle of incidence r , , four deflected beams. which are linearly polarized, are observed with a laser beam incidence. The polarizing directions of the deflected beams are directly related to the directions of axes of the optical indicatrix in the ferroelastic domains. The relation between the angle of incidence I and the angles of deflection l , and the polarizing directions of the deflected beams are explained by the Huygens constructions to the ray-velocity cross sections at the crystal surfaces and the domain walls in the incident plane. This optical phenomenon is confirmed as a specific property of ferroelastic crystals with multidomains. The properties of the deflected beams are described in detail.

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Considering epicyclic oscillations of pressure-supported perfect fluid tori orbiting Kerr black holes we examine non-geodesic (pressure) effects on the epicyclic modes properties. Using a perturbation method we derive fully general relativistic formulae for eigenfunctions and eigenfrequencies of the radial and vertical epicyclic modes of a slightly non-slender, constant specific angular momentum torus up to second-order accuracy with respect to the torus thickness. The behaviour of the axisymmetric and lowest-order (m = ±1) non-axisymmetric epicyclic modes is investigated. For an arbitrary black hole spin we find that, in comparison with the (axisymmetric) epicyclic frequencies of free test particles, non-slender tori receive negative pressure corrections and thus exhibit lower frequencies. Our findings are in qualitative agreement with the results of a recent pseudo-Newtonian study of the analogous problem defined within the Paczyński-Wiita potential. Implications of our results on the high-frequency quasi-periodic oscillation (QPO) models dealing with epicyclic oscillations are addressed.PACS numbers: 95.30.Lz, 95.30.Sf, 95.85.Nv, 97.60.Lf