In math mode, the spaces between subscripts and letters are not always the same, but depending on the preceding letters!
See e.g. (different colours indicate different spaces)
Is it the feature of packages {amssymb}
{amsmath}
or ….
Equations using {newtxmath}
math font:
\begin{equation}
\left.
\begin{array} {c}
\displaystyle \frac{\partial\epsilon_f}{\partial t} + \nabla \cdot (\epsilon_f \boldsymbol{u}_f) = 0 \\
\displaystyle \frac{\partial (\rho_f \epsilon_f \boldsymbol{u}_f)}{\partial t} + \nabla \cdot (\rho_f \epsilon_f \boldsymbol{u}_f \boldsymbol{u}_f) = -\epsilon_f \nabla p + \mu \nabla^2(\epsilon_f \boldsymbol{u}_f) + \boldsymbol{f}_b
\end{array}
\right\}
\end{equation}
Is there any global setting/solution for this issue, i.e. to adjust the spacing automatically depending on the letters and subscripts?
EDIT: put {bm}
package after amsmath
and font
packages will significantly improve the spacing.
Best Answer
After some testing I found that loading
\usepackage{bm}
significantly improves the spacing. As David points out in the comment, the kerning is possible, but grouping plays a role here. Obviously his packagebm
does better job on\boldsymbol
thanamsmath
. Just remember to loadbm
afteramsmath
and after your font packages!