docu of fourth order unit tensor: typo in index notation

corrected minor typo in documentation of fourth order unit tensor (or "fourth order identity tensor") \mathcal{I}_{ijkl}, compare for instance Wriggers "Nonlinear Finite Element Methods" p.79 eq. (3.270) or [Notes on Continuum Mechanics - Tensors](http://mmc.rmee.upc.edu/documents/Tensor_Analysis/tensors.pdf) eq. (1.175); appears to be a copy-paste error from previous line 101

diff --git a/include/deal.II/base/symmetric_tensor.h b/include/deal.II/base/symmetric_tensor.h
index 5e539e737048d16c01e34ac633a2c86905d4e77e..ceb538ef89cd1cd30d1fc782b3c73bdb26bdb291 100644 (file)
--- a/include/deal.II/base/symmetric_tensor.h
+++ b/include/deal.II/base/symmetric_tensor.h
@@ -99,7 +99,7 @@ DEAL_II_CONSTEXPR inline DEAL_II_ALWAYS_INLINE SymmetricTensor<4, dim, Number>
  * In index notation, we can write the general form
  * \f[
  *   \mathcal{I}_{ijkl} = \frac 12 \left( \delta_{ik} \delta_{jl} +
- *                                        \delta_{il} \delta_{jl} \right).
+ *                                        \delta_{il} \delta_{jk} \right).
  * \f]
  * To see why this factor of $1 / 2$ is necessary, consider computing
  * $\mathbf A= \mathbb I : \mathbf B$.