Finite determinacy of matrices over local rings.II. Tangent modules to the miniversal deformations for group-actions involving the ring automorphisms
arXiv:1604.06247
Abstract
We consider matrices with entries in a local ring, Mat(m,n;R). Fix an action of group G on Mat(m,n;R), and a subset of allowed deformations, Σin Mat(m,n;R). The standard question (along the lines of Singularity Theory) is the finite-(Σ,G)-determinacy of matrices. In our previous work this determinacy question was reduced to the study of the tangent spaces to Σand to the orbit, T_{(Σ,A)}, T_{(GA,A)}, and their quotient: the tangent module to the miniversal deformation. In particular, the order of determinacy is controlled by the annihilator of this tangent module. Then we have studied this tangent module for the group action GL(m,R)\times GL(n,R) on Mat(m,n;R) and for various natural subgroups of it. These are R-linear group actions. In the current work we study this tangent module for group actions that involve the automorphisms of the ring, or, geometrically, group-actions that involve the local coordinate changes. (These actions are not R-linear.) We obtain various bounds on the support of this module. This gives ready-to-use criteria of determinacy for matrices, (embedded) modules and (skew-)symmetric forms.
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