Clarify docs.

git-svn-id: https://svn.dealii.org/trunk@10382 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/base/include/base/symmetric_tensor.h b/deal.II/base/include/base/symmetric_tensor.h
index 9e2ff62c30320f39aa40c9837b14233c054bbcad..5fe4c4cd2735d2f9311e655c8e8cd7fb5c7df17a 100644 (file)
--- a/deal.II/base/include/base/symmetric_tensor.h
+++ b/deal.II/base/include/base/symmetric_tensor.h
@@ -695,7 +695,8 @@ class SymmetricTensor
                                      * of rank 2. For example, if the
                                      * present object is also a
                                      * rank-2 tensor, then this is
-                                     * the scalar-product contraction
+                                     * the scalar-product double
+                                     * contraction
                                      * <tt>a<sub>ij</sub>b<sub>ij</sub></tt>
                                      * over all indices
                                      * <tt>i,j</tt>. In this case,
@@ -715,6 +716,20 @@ class SymmetricTensor
                                      * present object and the indices
                                      * of the argument, and the
                                      * result is a tensor of rank 2.
+                                     *
+                                     * Note that the multiplication
+                                     * operator for symmetrict
+                                     * tensors is defined to be a
+                                     * double contraction over two
+                                     * indices, while it is defined
+                                     * as a single contraction over
+                                     * only one index for regular
+                                     * <tt>Tensor</tt> objects. For
+                                     * symmetric tensors it therefore
+                                     * acts in a way that is commonly
+                                     * denoted by a "colon
+                                     * multiplication" in the
+                                     * mathematica literature.
                                       */
     typename internal::SymmetricTensorAccessors::double_contraction_result<rank,2,dim>::type
     operator * (const SymmetricTensor<2,dim> &s) const;