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# Questions tagged [notation]

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

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### Notations for open and closed sets

I am wondering why a standard notation for open sets is $G$ and that for closed sets is $F$. I mean, $F$ precedes $G$ in the alphabet, whereas open sets are usually introduced before closed ones.
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### How does one write the "gothic" letters ($\mathfrak{g}$) in handwriting?

Most mathematical notation is designed with handwriting in mind in the first place, and typography must then try to follow, not always very successfully. However there is a particular type of notation ...
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### What is the meaning of $\alpha^{+L}$ for $\alpha$ an infinite countable ordinal?

Condition (a) of lemma 3.4 in the paper “Countable ranks at the first and second projective levels” [M. Carl, P. Schlicht, P. Welch] is $\alpha^{+L} = \omega_1,$ where $\alpha$ denotes any infinite ...
1 vote
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### Notation for function that is constant with respect to a parameter

I am wondering if there is a common notation for a function that does not depend on a particular parameter. I am wondering about notation both for applying the function ($f(x, y)$) as well as defining ...
1 vote
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### "Variable and fixed" in categories

We often find in Grothendieck terminology the words variable and fixed (or absolute). For example in SGA 4 studies variable topological spaces, groups, and categories as examples of morphisms of topos....
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### First use of corner quotes for Gödel numbers

Who first used the corner quotes, $\ulcorner$ and $\urcorner$, for the notion of Gödel number? They can also be written as\Godelnum with Sam Buss's macro. They were ...
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### Degree of a morphism between affine varieties

(Context: rewriting a joint paper with a coauthor.) We are defining the degree of a morphism $f:A^m\to A^{n}$ to be $\max_{1\leq i\leq n} \deg(f_i)$, for $f_1,f_2,\dotsc,f_{n}$ the polynomials ...
1 vote
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### Notation for infinite cartesian products

This is a soft question, feel free to delete it if deemed inappropriate for the site. What is the best notation for the cartesian product of an infinite number of copies of the same set $E$? Maybe one ...
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### Common notation for function over infinitely many variables? [closed]

For a document about reinforcement learning, I want to write the joint probability density over the entire trajectory of states and actions like $p(s_0, a_0, s_1, a_1, s_2, \dotsc)$. However, this ...
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### Is it improper to define matrices as being $n \times m$ rather than $m \times n$? [closed]

For whatever reason, I have always defined matrices as being $n \times m$, and that is how I have been defining matrices throughout my dissertation. Recently however, I have noticed that nearly every ...
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### About the maximum number of leaves adjacent to a vertex in a tree

Let $T$ be a finite tree graph with the set of vertices $V(T)$. For an arbitrary vertex $v \in V(T)$, I define $l(v)$ to be the number of leaves connected to $v$. In my study, I need to define the ...
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### What does $\omega^*$ mean? [closed]

I've recently found in some short article (source below) the symbol $\omega^*$ (generally, starred ordinal number), but without explanation what that symbol means. From the context I understood that ...
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### Name for the theory of words with equal length, prefix, successors

I've worked with this theory for a while, but I've never been quite sure what to call it: $$(\Sigma^*, =_{el}, \preceq, (S_a)_{a \in \Sigma})$$ Where $\Sigma^*$ is the set of finite words on finite ...
1 vote
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### Pronunciation: the Erdős–Rado partition notation

The Erdős–Rado notation $a \rightarrow (b)^c_d$ is common in partition calculus / combinatorial set theory, as well as its negation $a \not\rightarrow (b)^c_d$. In that field, is there a standard way ...
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### Reference request: Different definitions of Big O notation

This question might sound strange, but I would like to settle this problem once and for all. For as long as I can remember, I was introduced to the Big O notation by this definition: Def. 1: Let $f, g$...
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### Terminology and notation for generated subgroups

I would like to think about formation of the smallest subgroup (or monoid, or whatever) $H$ of $G$ containing two given subgroups $A$ and $B$ as an operation on subgroups, and I wonder if there is a ...
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### Higher order Leibniz rule and ordered multiindex notation

Although I think this is probably known, I am making here a short exposition on the multiindex notations I am using to make this question self-contained. I note that there is at least two different ...
1 vote
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### What does square bracket superscript star mean in basic group theory typically?

I'm reading some paper where they haven't really defined their notation very well (or I've missed something). You can see the image below. What does the square bracket and star mean precisely? The ...
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### Notation for H is isomorphic to a subgraph of G

Is there a notation for the statement $H$ is isomorphic to a subgraph of $G$? I was thinking of using $H<G$, but I'd like to use standard notation if possible.
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### Proof of Theorem 9.2 of the book Cubic Forms by Yu. I. Manin (end of page 37)

I warn that I first posted this question in Mathematics Stack Exchange but it got no attention at all. I think that it fits better there by its explanatory nature but maybe the book being reference is ...
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### Finitely-generated conjugation action on a subgroup that is not normal... what is that?

If $H \lhd G$, then $G$ acts on $H$ by conjugation. I need to talk about this action but in a situation where $H$ is not (necessarily) normal. When $H \leq G$, there is a "partial action" of ...
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### How to denote a partial derivative?

This question is related to Was Jacobi the first to notice the ambiguity in the partial derivatives notation? And did anyone object to his fix? and Suggestions for good notation . When there are two ...
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### Good notation for finite partial functions from $\omega$ to 2

I'm working in computability theory and need to use partial functions with finite domain from $\omega$ to 2 as approximations in my current paper. Normally this is simply done using $2^{< \omega}$ ...
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### Temporal generalization of graphs: density vs $n$ and $m$?

In short: we generalize graphs to the temporal case, but fail to fully preserve the usual relation between density, number of vertices, and number of edges; how to make better? Context. We propose a ...
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### Confusing notation for sets of unordered vs ordered pairs

Given two finite sets $X$ and $Y$, one may consider the ordered pairs $(x,y)$ with $x\in X$ and $y \in Y$. Then, $(x,y) \not= (y,x)$, and $(x,x)$ exists if $x\in X$ and $x\in Y$. One may also consider ...
I recently isolated the following definition, which I believe it should have appeared somewhere. Let $\kappa$ be a cardinal, and let $X$ be a set with $\kappa^+\leq |X|$. Definition: An ideal $\... -1 votes 1 answer 182 views ### Typesetting of symbols and "operators" denoting sets [closed] Question: what are the conventions for typesetting sets of certain objects, especially the vertices and edges of a graph or those adjacent to an edge or vertex. For vectors and matrices there is the ... 0 votes 1 answer 210 views ### Explanation of a formula to calculate the zenith distance of sun and moon [closed] I am studying tidal accelerations and referring to a well known paper by I M Longman : Formulas for computing.." J Geophys Research 64 (12) Dec 1959. At Eq 12 he writes a term "1336.rev"... 9 votes 1 answer 2k views ### Origin of the symbol for the tensor product I have recently realised that the Paleo-Hebrew (and Phoenician) graph for the Hebrew letter ט (Teth) is$\otimes$. This made me wonder if there is any relation between the choice of the symbol and the ... 1 vote 0 answers 246 views ### Notation for the regular and the adjoint representation of a finite group, in particular the symmetric group The (left) regular representation of a finite group$G$is the action on itself by left multiplication,$g\cdot h = gh$. The adjoint representation of a finite group$G$is the action on itself by ... 7 votes 0 answers 290 views ### Why are fundamental weights denoted by omega? In my field (and many others, I believe) the absolutely standard notation for the fundamental weights of a root system is lowercase omega:$\omega$. Recently I was taken aback to receive a copyedited ... 4 votes 1 answer 119 views ### Question about the notation$N_{\chi}(\alpha, T)$, the number of zeroes of the$L(s, \chi)$in a rectangle I am confused with what seems to be a standard notation in analytic number theory and I'd appreciate any clarification. I am interested in the zero density estimates, for example link.springer.com/... 3 votes 1 answer 296 views ### Name and properties of$\mathrm{lcm}(\{1,\,\cdots,\,n\})$[closed] one of the most prominent functions of the first$n$natural numbers is the factorial$n!$that denotes their product. Today however I wondered whether the least common multiple$\mathrm{lcm}(n):=\...
What I know as the Plancherel measure for a group is a measure on the spectrum of $G$, aka the set of irreducible representations - at least for finite groups, this makes perfect sense. Now, this ...