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For questions about mathematical notation, i.e. the symbols used to represent mathematical objects and operations.

8 votes

Is there a reference containing standard mathematical notations?

My experience with subjects that have a long history suggests that notation in mathematics evolves over time in less than logical ways. … In some areas there simply isn't any "standard" notation, while in many others some influential sources have tended to establish a de facto standard. …
10 votes
Accepted

What does the t in t-category stand for?

Though I don't have inside information, it's clear that the notes in Asterisque 100 (1982) by BBD gave the first formal definition of t-category and t-structure on a triangulated category (section 1.3 …
Jim Humphreys's user avatar
7 votes

Is there a name for the involution on Laurent polynomials?

My first encounter with it was in the 1979 Kazhdan-Lusztig paper on Hecke algebras, where they use a bar notation and combine this involution on Laurent polynomials with the inversion in a given Coxeter … The bar notation makes it unnecessary to invent a name for the involution on Laurent polynomials, but "bar involution" will certainly do. …
48 votes

Fraktur symbols for Lie algebras

It naturally crept into mathematical usage and notation. … But for Hilbert and others this was quite natural notation, as was lower case $\mathfrak{f}$ for the German word 'Fuhrer' (printed with Umlaut over 'u'), now usually called the "conductor". …
Jim Humphreys's user avatar
6 votes

Why are the Dynkin diagrams E6, E7 and E8 always drawn the way they are drawn?

Here the vertices correspond to simple roots, not just simple reflections, so the notation has to incorporate some length information. …
Jim Humphreys's user avatar
18 votes
4 answers
2k views

Origin of symbol *l* for a prime different from a fixed prime?

I've never seen an authoritative explanation for the choice of the lower case letter $\ell$ or $l$ to denote an arbitrary prime different from a given prime $p$. This now has its own LaTeX command \e …
Jim Humphreys's user avatar
6 votes
1 answer
745 views

Origin of symbols used for half-sum of positive roots in Lie theory?

2) A number of people used the notation g, including Freudenthal ((nag. Math., 1954-56), then Kostant (Trans. Amer. Math. … (In 1969 I did buy a copy of Bourbaki but was already used to writing $\delta$ and using other root system notation.) ADDED: Notation is essential in mathematics but often problematic. …
Jim Humphreys's user avatar