From what I know, one cannot use a mathematical symbol for two different notations in a thesis. Is this right? The thing is that I am trying to cite a book in my thesis, but this book uses (tau) for both viscous stresses and reynolds stresses. Can I do the same in my thesis or do I have to choose another notation?
Bear in mind that I am new to academic writing, thanks!
So why not just define a tau with a subscript v and a tau with a subscript r - make it clear in your nomenclature and you're sorted.
See:
\mathrm or \text if you're a LeTeX user) and indexes in italics. But few readers actually pay enough attention for that to be reliable.
Commented
May 16, 2019 at 18:29
From what I know, one cannot use a mathematical symbol for two different notations in a thesis. Is this right?
That's certainly good advice, since it avoids unnecessary confusion.
The thing is that I am trying to cite a book in my thesis, but this book uses (tau) for both viscous stresses and reynolds stresses. Can I do the same in my thesis or do I have to choose another notation?
Presumably you don't intended to use τ to mean viscous stresses and reynolds stresses in the same context, because usage of τ would then be ambigious. So, I presume you'll be using τ to mean viscous stress in one context, perhaps an entire chapter, and to mean reynolds stress in another context, perhaps a different chapter. This seems reasonable. However, you needn't use the book's notation, especially if there is a risk of ambiguity.
"This seems reasonable." No, it's not, and academics, and indeed any one hoping to get an idea across, need to stick with a consistent method for describing different phenomena, constants and variables. It is not reasonable to basically require you to keep looking back a the beginning of a chapter in a book to determine the symbology, even given you understand what each symbol should represent normally. The book made a mistake in overloading symbols like that.
From what I know, one cannot use a mathematical symbol for two different notations in a thesis. Is this right?
Such things are not governed by hard-and-fast rules. Your institution might have specific style guidelines for a thesis, but notational choices are usually at the discretion of the author. Of course, it's ultimately your advisor and/or committee who decides whether your thesis is acceptable, though it's unlikely that notation alone would be the cause for rejection.
The thing is that I am trying to cite a book in my thesis, but this book uses (tau) for both viscous stresses and reynolds stresses. Can I do the same in my thesis or do I have to choose another notation?
It's up to you. Make your own decision as to which way will be the most clear. You can ask your advisor if you are unsure.
Perhaps for some perspective: the scope of a "name" can be limited, that is, "local", or it can be "global". Even fairly basic programming principles nowadays (with virtually unlimited namespace, as opposed to 1960's Fortran) recommend keeping namespaces as local as possible...
... and this advice applies to most mathematical notation, as well. That is, there are really very few symbols/notations that are understood globally and unambiguously. That's fine. I think one should be reconciled to (re-) setting the "names" in a given "scope", and not at all depend on document-dependent notation/names as though they'd be something the reader would have assimilated. (Excepting perhaps a very small number...)
Even then, if "tau" has two different and conflicting senses in the literature, there is no genuine intellectual/scientific purpose served in being mute on the point, and trying to find a way to dodge the operational ambiguity. That is, in each of your sections or subsections, tell what "tau" is. Done.
That is, do try to find a viewpoint from which this is a non-issue.
