Improved Lower Bounds on Capacities of Symmetric 2D Constraints Using Rayleigh Quotients

A method for computing lower bounds on capacities of two-dimensional (2D) constraints having a symmetric presentation in either the horizontal or the vertical direction is presented. The method is a generalization of the method of Calkin and Wilf (SIAM J. Discrete Math., 1998). Previous best lower bounds on capacities of certain constraints are improved using the method. It is also shown how this method, as well as their method for computing upper bounds on the capacity, can be applied to constraints which are not of finite-type. Additionally, capacities of two families of multidimensional constraints are given exactly.