Theory of spots on chemically peculiar stars

Surface inhomogeneities are found in many stars. In active sun-like stars and cool giants temperature spots similar to that found in the Sun are recovered from the inversion of spectroscopic data. M-dwarfs also show highly inhomogeneous surface structures in polarized light and photometric variability that are believed to be connected with cool regions on their surface, too. Supergiants have highly inhomogeneous atmospheres because large convective cells, and therefore bright and dark regions, have sizes comparable to the size of stars themselves. Hot luminous stars can have dense clamps in their atmospheres caused by an interaction of fast stellar wind, rotation, and the magnetic fields. Finally, a special class of main-sequence B-F stars, called chemically peculiar stars, have spots of abundance origin. Spots in these stars can look bright or dark depending on wavelength of observation. Modern interferometry is capable of reaching a very high angular resolution that will make it possible to study starspots in very detail. In this review we will focus on starspots in general and abundance spots in chemically peculiar stars in particular, as well as possible application of interferometry to study them.