[Tex/LaTex] Double-bar notation for second-order tensors4

bartensorunderline

I found it interesting to represent a tensor with the notation normally used by my professor. Looking for respect to the mathematical symbol I found this code from this post, very interesting.

I would like to insert this command below,I modified the code but the result with '\underline' is not pleasant

\newcommand*{\rttensor}[1]{\underline{\underline{#1}}}
\overline{u'_{i}u'_{j}u'_{i,j}} = \rttensor{T}

but the result is not satisfactory. The command with \bar is aesthetically superior, but I can not find a way to put it underneath

\newcommand*{\rttensortwo}[1]{\bar{\bar{#1}}}

\overline{(\rho'u'_{i})} = \rttensortwo{T}

I think another possible solution could be this, but I have some doubts about it and I have to look more carefully.

others have had experience with this?

MWE

\documentclass{article}
\usepackage{amsmath}
\newcommand*{\rttensor}[1]{\underline{\underline{#1}}}
\newcommand*{\rttensortwo}[1]{\bar{\bar{#1}}}

\begin{document}

$\overline{u'_{i}u'_{j}u'_{i,j}} = \rttensor{T}$
\par\bigskip
$\overline{(\rho'u'_{i})} = \rttensortwo{T}$
\end{document}

I found a problem with the position of the double bar in a certain type of tensor

\documentclass{article}
 \usepackage{amsmath}
 \usepackage{stackengine}

\newcommand*{\barbI}[1]{\stackunder[1.0pt]{$#1$}{\rule{1.0ex}{0.095ex}}} %% One bar
\newcommand*{\barbII}[1]{\barbI{\barbI{#1}}}%% double bar
\newcommand{\TRII}{\ensuremath{ \barbII{T_{R}}}} %% Tensore di Reynols 

  \begin{document}

$\TRII$ \quad\text{Tensore di Reynolds}\\

$\barbI{T}$\\

\end{document}

——————-UPDATE—————–

\documentclass{article}
 \usepackage{amsmath}
 \usepackage{stackengine}

\newcommand*{\barbI}[1]{\stackunder[1.0pt]{$#1$}{\rule{0.9ex}{0.095ex}}} 
\newcommand*{\barbII}[1]{\barbI{\barbI{#1}}}
\newcommand{\TRII}{\ensuremath{\barbII{\emph{T}}_{\!R}}}

  \begin{document}

\begin{enumerate}
   \item $\barbII{T}_{R}$ 
    \item   $ \TRII $ < ----- Optimal Solution
\end{enumerate}

\end{document}

Best Answer

Do you mean something like \barbelow in this MWE, which can be recursively used? Taken from my answer at \bar below symbol

\documentclass{article}
\usepackage{stackengine}
\begin{document}
\newcommand\barbelow[1]{\stackunder[1.2pt]{$#1$}{\rule{.8ex}{.075ex}}}
\( \overline{A} \bar{A} \barbelow{A} \barbelow{\barbelow{A}} \)
\end{document}

Related Solutions

[Tex/LaTex] double tilde symbol under letter

Here I use stacks to recursively place \sim under the argument, based on the value of the optional argument. In the definition, the [1pt] is the under-gap from the argument and the [0pt] is the vertical separation between \sim characters in a multi-stack. These values can be altered to suit (including being made negative).

I have not used any bold font for the tensor itself, though it could be added, if desired, to the definition, or at time of invocation.

The specification of \def\useanchorwidth{T} says to ignore the width of the \sim underset in setting the horizontal spacing. The only time that could be an issue is if you, for example, used adjacent invocations on narrow arguments, e.g., \tenq[2]{i}\tenq[3]{j}. While the \useanchorwidth line could be removed, in which case \tenq with narrow arguments would always take up at least the width of a \scriptscriptstyle\sim, my first step would instead be to manually add \, space on those very rare occasions when needed.

\documentclass{article}
\usepackage{stackengine}
\stackMath
\newcommand\tenq[2][1]{%
 \def\useanchorwidth{T}%
  \ifnum#1>1%
    \stackunder[0pt]{\tenq[\numexpr#1-1\relax]{#2}}{\scriptscriptstyle\sim}%
  \else%
    \stackunder[1pt]{#2}{\scriptscriptstyle\sim}%
  \fi%
}
\begin{document}
\[
\tenq{\sigma}\neq\tenq[2]{\Lambda}\neq\tenq[3]{\Delta}\neq\tenq[4]{\psi}
\]

\end{document}

enter image description here

[Tex/LaTex] How to place a wide bar over a wide expression

You can use Hendrik Vogt's macro widebar or use the \widebar command from mathabx (here renamed \varwidebar for testing purposes).

In the following code, where I defined what I believe to a be an inner product, with \DeclarePaired Delimiter from mathtools (needless to load amsmath), you'll see there's not much difference between the three solutions. There's a significant difference when one has to take into account the italic angle of the maths font:

\documentclass[12pt, a4paper]{article}
\usepackage{mathtools}%
\usepackage{xparse, etoolbox}

\DeclarePairedDelimiterX{\innerp}[1]{\langle}{\rangle}{\innpargs{#1}}
\NewDocumentCommand{\innpargs}{>{\SplitArgument{1}{,}}m}
{\innpargsaux#1}
\NewDocumentCommand{\innpargsaux}{mm}
{\ifblank{#1}%
{\ifblank{#2}{~{,}~}{{\, · \,}{,}{\mkern2mu#2}}}%
{{#1\,}{,}\ifblank{#2}{\, · \,}{\mkern2mu#2}}%
}%
\usepackage{widebar}

\DeclareFontFamily{U}{mathx}{\hyphenchar\font45}
\DeclareFontShape{U}{mathx}{m}{n}{
      <5> <6> <7> <8> <9> <10>
      <10.95> <12> <14.4> <17.28> <20.74> <24.88>
      mathx10
      }{}
\DeclareSymbolFont{mathx}{U}{mathx}{m}{n}
\DeclareFontSubstitution{U}{mathx}{m}{n}
\DeclareMathAccent{\varwidebar}{0}{mathx}{"73}

\begin{document}

  \[ \begin{array}{c@{\qquad}c@{\qquad}c}
  \texttt{\textbackslash overline} & \texttt{\textbackslash widebar} & \texttt{\textbackslash varwidebar}\\[2ex]
  \overline{\innerp{x, y}} & \widebar{\innerp{x, y}} & \varwidebar{\innerp{x, y}} \\[1.5ex]
  \overline{A\cdot\mkern-2mu B} & \widebar{A\cdot\mkern-2mu B} & \varwidebar{A\cdot\mkern-2.5mu B}
  \end{array} \]%

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] double tilde symbol under letter

[Tex/LaTex] How to place a wide bar over a wide expression

Related Question