I'm looking for the lowercase script r shown below (used here to denote the rank of a matrix). Does anyone know how to reproduce it?
1 Answer
\mathscr{r}
would be a quick way. To find a script r, which matches your sample best, have a look at these sources regarding script fonts:
The section Calligraphical and Handwritten Fonts in the LaTeX Font Catalogue. You could choose a font for your script r by looking at the font samples.
Script fonts for mathematical use available to LaTeX users is a short font sampler giving an overview.
Better script fonts for maths in the TeX FAQ
The Comprehensive LaTeX Symbol List which contains script symbols, for example look at Table 213: Math Alphabets and try the commands and packages there if you like.
\sigma_{r+1}
in line 5 is an ordinary italic r, and doesn't match the script r earlier in the equation? as outlandish as it may seem, this sample appears to have been created by tex -- the shapes of the sigmas and deltas are a giveaway. that leaves open the possibility of asking the author where the script r came from.