I'm interested in representing elastic deformations (e.g. stretching) as using Lie groups. There are a few references to using GL(3,R) $GL(3,\mathbf{R})$ but I'm wondering if possible to use GL(3,R) subgroups . of $GL(3,\mathbf{R})$. For example, deformation gradient (F) $F$) can be decomposed into rotation R & $R$ and symmetric positive definite stretch U $U$ as in $F = RURU$. U $U$ then decomposable by SVD into $U = PEP^T PEP^T$ where $P =$ matrix of eigenvectors of U & $U$ and $E =$ diag. matrix of eigenvalues of U. $U$. Such diag. matrices are Lie subgroup of GL(3,R) & $GL(3,\mathbf{R})$ and represent pure stretches along orthogonal stretch axes. Similarly, 3x3 identity matrices with off-diag. positive entries represent shears.
So, my question is:
Can elastic deformations be represented by GL(3,R) subgroups of $GL(3,\mathbf{R})$ like those mentioned above?
