Regularity and permutability via transferability of tolerances
Ivan Chajda · Czech digital mathematics library · 1996
An algebra A has n-transferable tolerances if for any a } b,c £ A there exist di,..., d n £ A such that T(a, b) = T(c, di) V... VT(c, d n ) in the tolerance lattice Tol A. We prove that a variety V is regular and permutable if and only if each A £ V has n-transferable tolerances.Analogously we characterize varieties with 0-regular and permutable congruences.