From: Johannes Friedlein <johannes.friedlein@fau.de>
Date: Tue, 28 Dec 2021 18:28:49 +0000 (+0100)
Subject: docu of fourth order unit tensor: typo in index notation
X-Git-Tag: v9.4.0-rc1~689^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F13145%2Fhead;p=dealii.git

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 5e539e7370..ceb538ef89 100644
--- 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
  * $\mathbf A= \mathbb I : \mathbf B$.