Interaction of electromagnetic radiation (Mössbauer, X-ray, optical, ultrahigh frequency) and of elementary particles (neutrons, electrons, positrons) with solids in the presence of external excitations (acoustic waves, temperature gradients, electric, magnetic and electromagnetic fields); monitoring of low-temperature plasma parameters by means of acoustic fields; development of the catastrophe theory for description of phase transitions in physical systems in the presence of external excitations (acoustic waves, temperature and electromagnetic fields); influence of external factors (pressure, acoustic waves, electric and magnetic fields) on physical, electrophysical and contact properties of the matter (semiconductors, semiconductor heterogeneous junctions, high-temperature superconductors, liquid crystals); inverse problems in the spectroscopy of solids; acoustics; material sciences; information exchange between biological objects.