# The Block recursion library: accurate calculation of resolvent submatrices using the block recursion method

## Description

Abstract The Block Recursion Library, a collection of FORTRAN subroutines, calculates submatrices of the resolvent of a linear operator. The resolvent, in matrix theory, is a powerful tool for extracting information about solutions of linear systems. The routines use the block recursion method and achieve high accuracy for very large systems of coupled equations. This technique is a generalization of the scalar recursion method, an accurate technique for finding the local density of states. A sample p... Title of program: BLOCK RECURSION LIBRARY Catalogue Id: ABZB_v1_0 Nature of problem Consider a physical system, modelled by a set of coupled linear equations which are represented by a matrix M acting on a set of basis vectors. The resolvent R of M is a matrix which describes the response of the system to an applied generalized force. Often, important imformation about the solutions to the set of equations can be found from the elements of a small submatrix of R. For very large systems of equations, it is thus desirable to calculate such submatrices accurately, and without nece ... Versions of this program held in the CPC repository in Mendeley Data ABZB_v1_0; BLOCK RECURSION LIBRARY; 10.1016/0010-4655(91)90055-P This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2018)