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From: F/32 Eurydice on 9 Jul 2010 06:42 What's the name of an integer matrix whose inverse is also an integer matrix?
From: Tim Little on 9 Jul 2010 08:49 On 2010-07-09, F/32 Eurydice <f32eurydice(a)sbcglobal.net> wrote: > What's the name of an integer matrix whose inverse is also an integer > matrix? "Element of GL(n,Z)"? - Tim
From: Henry on 9 Jul 2010 10:13 On 9 July, 13:49, Tim Little <t...(a)little-possums.net> wrote: > On 2010-07-09, F/32 Eurydice <f32euryd...(a)sbcglobal.net> wrote: > > > What's the name of an integer matrix whose inverse is also an integer > > matrix? > > "Element of GL(n,Z)"? I think they must have determinant +/- 1. If so, could one name be "scale preserving integer matrix"?
From: achille on 9 Jul 2010 10:26 On Jul 9, 10:13 pm, Henry <s...(a)btinternet.com> wrote: > On 9 July, 13:49, Tim Little <t...(a)little-possums.net> wrote: > > > On 2010-07-09, F/32 Eurydice <f32euryd...(a)sbcglobal.net> wrote: > > > > What's the name of an integer matrix whose inverse is also an integer > > > matrix? > > > "Element of GL(n,Z)"? > > I think they must have determinant +/- 1. > If so, could one name be "scale preserving integer matrix"? unimodular matrix. REF: http://en.wikipedia.org/wiki/Unimodular_matrix
From: Han de Bruijn on 9 Jul 2010 11:06
On 9 jul, 12:42, "F/32 Eurydice" <f32euryd...(a)sbcglobal.net> wrote: > What's the name of an integer matrix whose inverse is also an integer > matrix? The inverse of an integer matrix is an integer matrix, apart from a constant, which is the determinant of the original matrix: multiply the inverse with the determinant of the original. An application of this is the automatic balancing of chemical equations: http://hdebruijn.soo.dto.tudelft.nl/www/programs/delphi.htm#chemie Han de Bruijn |