I hope this is the correct forum. If not, please let me know.
I am writing a master thesis in maths and I am not sure, when I do use upright letters for a variable.
Let's have a look at the following sentence: Let $a,m$ be naturals and let $\operatorname{g} := \operatorname{lcm}(a,m)$.
My guess is that I write $a$ and $m$ in cursive, because I can choose them arbitrarily. But I would write $\operatorname{g}$ upright, because it is dependent on $a$ and $b$. In addition, $\operatorname{lcm}$ is an operator, so I write that upright anyways. That's why I would write the $\operatorname{g}$ upright, too.
Is that correct? Is there a style convention?
In any style convention I ever was aware of you would write $g$ in your example cursive.
The letters $\operatorname{lcm}$ are upright as a multi-letter operator name.
In fact, in your source code you have written
$\operatorname{g} := \operatorname{lcm}(a,m)$You would normally just write
$g := \operatorname{lcm}(a,m)$So, if you are using LaTeX for your thesis, the question is more or less handled automatically, if you put all your math into
$...$and use\operatornamewhen needed.