# Questions tagged [notation]

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

282
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### Does $\mathsf{SVC}^\ast$ exist?

$\mathsf{SVC}(S)$ is the assertion that for all sets $X$ there is an ordinal $\eta$ and a surjection $f\colon\eta\times S\to X$. I would like to denote by $\mathsf{SVC}^\ast(S)$ the same assertion but ...

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### How to talk about the “shape” of the kernel of an integral transform

So I'm learning about integral transforms, and although it isn't a complete specification, the fact that the Fourier transform decomposes functions into sinusoids, the Laplace into damped sinusoids, ...

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1
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### Notation for weak derivatives

I remember that, as a student, I felt a bit uncomfortable because I had to use the same notation (say $f'$, $D^\alpha f$, $\frac{\partial f}{\partial x^j}$, $\nabla \cdot f$ etc...) for classical and ...

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### Adjunction symbol

What are the reasons for the adjunction symbol $F\dashv G$ for a pair of functors $F:C\to D$ and $G:D\to C$? There is no explanation or motivation in the article of Kan where adjunctions are ...

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### Notation $\le_{a,b,n,\ldots}$ in Analysis

In modern Analysis, especially Functional Analysis, one proves, or one uses inequalities of the form
$$F(X)\le_{a,\ldots,n}G(X).$$
The meaning of the subscripts in the inequality sign means that there ...

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1
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### Is this single-variable function being called with two variables (and if so, how do I handle that), or am I misreading the notation? [closed]

While working on a project, I came across a paper that includes this sum on page 15 as the definition of a support function $r$ for a surface with tetrahedral symmetry:
$$
r(ξ, \bar{ξ}) = \frac{1}{\#𝒢...

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1
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### Unpacking the plethystic substitution $h_n[n\mathbf{z}]$ in a paper by Aval, Bergeron and Garsia

I'm not familiar with the formalism of plethysm, so I need some help in unpacking the plethystic substitution $h_n[n\mathbf{z}]$ found in eqns. 5.6 and 5.9 of "Combinatorics of labelled ...

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### Cartesian product of $[(k-2)\text{-times Interval}_1] \times [\text{Interval}_2] \times [\text{Interval}_2]$

This is a soft question, hoping that it is still appropriate for this forum.
I need to describe twice the following region of $\mathbb{R}^k$ (i.e., we are in a $k$-dimensional Euclidean space, where $...

0
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0
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### Definition of term functions, in universal algebra

According to the definitions in Sankappanavar's universal algebra :
Assume $p$ is a term, then $p(x_1,x_2,...,x_n)$ indicates that the variables occurring in $p$ are among $x_1,...,x_n$. But there is ...

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### Notation for spectral sequences [closed]

Every single spectral sequence I have seen in my life was denoted by $E$. Even when there is more than one spectral sequence, people tend to use the same letter with some workaround (e.g. a fourth ...

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### Merging two composable walks in a graph

Let $G$ be a graph (i.e., an undirected graph in which we allow for loops and parallel edges). Denote by $V$ the vertex set, by $E$ the edge set, and by $\psi$ the incidence function of $G$, and let $\...

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### Examples of bad notation and its consequences [closed]

An example of bad mathematical notation that comes in my mind and has caused complications throughout history is the notation for imaginary numbers. The original notation used to represent imaginary ...

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### Minus sign inside derivative operator, notation problem

Hello fellow mathematicians. Can anybody help me understand what the minus (-) sign in this derivative means? Its the usual d/dy but with a minus added d-/dy. I can't find references, the book cited ...

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### What do you call $x$ such that $\textrm{dim} f^{-1}(f(x))>0$?

Let $f:V\to W$ be a morphism between varieties, with $\dim \overline{f(V)} = \dim V$. What do you call the closed proper subvariety $S$ of $V$ consisting of points $x$ such that $\textrm{dim} f^{-1}(f(...

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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 big-O of a random variable?

I encountered this problem in a book "Pattern Recognition and Machine Learning" by Christopher M. Bishop. I excerpt it below:
screenshot of the book
In the excerpt, the big-O notation $O(\xi^...

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### Name for extension of the symplectic group

Let $S_g$ denote an ortientable surface of genus $g$. Let $\operatorname{Diff}(S_g)$ denote the group of diffeomorphism (that need not fix the orientation). Is there a name for the image of $\...

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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 ...

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0
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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 ...

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1
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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 ...

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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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### Notation for dominating (or uniformly bounded) function

While I developing a new statistical estimator, I wondered is there any good notation for dominating (or uniformly bounded) function.
A situation like this. For some true function $f:\mathbb{R} \to \...

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0
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### Are there standard short notations for ascending and descending cyclic permutations?

In a paper I am currently writing I use cyclic permutations of the form
$$
(k,k+1,\dots,\ell)
$$
and
$$
(\ell,\ell-1,\dots,k)
$$
of consecutive elements quite a lot (I added the commas to avoid ...

2
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0
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### Why is $H$ the standard notation for mean curvature?

I am curious about the origin of the notation $H$ to denote the mean curvature of a surface in $\mathbb{R}^{3}$.
I suppose that the symbol $K$, which is commonly used to denote the Gaussian curvature, ...

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### What is the basis for the quantifier notation? [closed]

The symbols $\forall, \exists$ are the ones officially used to denote universal and existential quantifiers respectively. I understand that the choice of $\exists$ was made by Peano, while of $\forall$...

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### Who introduced the notation for $\beth$ numbers and when?

Georg Cantor, when developing the basics of set theory, noted that there are two ways to increase cardinality: power sets and successors (or, in modern terms, the Hartogs operation).1
Eventually the ...

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### What does the subscript 'x' of a matrix mean? [closed]

The 3x6 matrix G is as follows,
$\text{G} = [\text{V}_\times| I_{3\times3}]$
$\text{V}$ is a skew matrix of a vector with 3 elements about a 3D point. The dimension of $\text{V}$ is 3x3.
$I$ is the ...

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1
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### The meaning of $L_p^l(\Omega)$ in a paper of Bogovskii on Sobolev spaces

On the first page of the old paper Solution of the first boundary value problem for an equation of continuity of an incompressible medium of Bogovskii, the notations $W_p^l(\Omega)$ and $L_p^l(\Omega)$...

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### Why aren‘t op and co switched?

When reading through Loregian and Riehl - Categorical notions of fibration, on p. 3 there is a remark that confuses me about notation. Given a $2$-category $\mathcal C$ one usually defines $\mathcal C^...

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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 ...

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1
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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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0
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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 ...

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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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### Can NBG be interpreted in this system that use new notation for class-abstractions?

We introduce a new symbol $\lambda$ to denote class-abstractions, and we add the following rule:
if $\phi$ is a formula that use $``\mu"$, and in which the symbol $\sf y$ doesn't occur; then: $\lambda ...

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### What is meant by this notation of the real forms of $E_6$?

There are five real forms of the exceptional Lie group, $E_6$. Four of them are notated as in the following:
The split form as EI or $E_{6(6)}$
The quasi-split form as EII or $E_{6(2)}$
EIII or $E_{...

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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 $2^{< \omega}$ ...

3
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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 ...