FETI with redundant Lagrange multipliers

Theorem 1 The condition number of the FETI method, with the new precon­

ditioner M, satisfies

n(PM~1P tF) < C (1 + log [H/h)f.

Here, n(PM~1P tF) is the spectral condition number of PM~1P tF, and C is independent ofh,H , 7, and the values of the pi.