On the number of isohedral polyominoes

A polyomino is a connected figure on a plane composed from a finite number of unit squares adjacent to each other on the sides. A tiling of a plane into polyominoes is called isohedral if the symmetry group acts transitively on it, that is, if for any two polyominoes of the tiling there is a global symmetry of the tiling that moves one polyomino into the second. The paper considers the problem of counting the number of polyominoes of area ???? that generate isohedral tilings of the plane. It is shown that the number of such polyominoes does not exceed ????(????)????^4(???? + ????)^????, where ???? is the connective constant of the square lattice Z^2. It is known that ???? < 2.7. Similar estimates were also obtained in the case where the perimeter rather than the area of the polyomino is fixed. In addition, a similar estimate is valid for the number of isohedral tilings of the plane themselves under the additional condition of regularity of the tilings Previously, similar results were obtained in the case of lattice tilings of the plane intopolyominoes, for the so-called ????2-splits, as well as for lattice tilings into centrally symmetric polyominoes.The proof is based on the criteria for the existence of an isohedral tiling of the plane into polyominoes obtained by Langerman and Winslow, as well as on counting the number of selfavoidingrandom walks on the lattice Z2, both standard and with a given symmetry group.In conclusion, possible directions for further research and some open problems are briefly discussed.