# Questions tagged [terminology]

Questions of the kind "What's the name for a X that satisfies property Y?"

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### Extremely disconnected or extremally disconnected?

In the context of Banach space theory, what is the correct terminology: extremally disconnected or extremely disconnected. Looking through the internet I have met using both extremely and extremally ...
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### Terminology: group action with normal stabilizers

This is just a terminology question. Is there a name for a group action which is transitive and for which the stabilizers are normal subgroups? In this situation, the stabilizers are all equal. If the ...
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### Is there a more descriptive term for Characteristic Classes? [closed]

Recently I went along to a conference on Communication in Mathematics where a number of people, me amongst them, complained about talks where one only understood 5% of what was going on. A part of ...
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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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### Name for class of functions satisfying $E[f(X)] = f(E[X])$

If $X$ is a continuous random variable and $E[\cdot]$ denotes the expected value, then does the class of functions $f$ for which $$E[f(X)] = f(E[X])$$ have a name? Obviously if $f$ is linear then ...
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### Planar graphs - more or less

A graph is planar if it can be drawn on the plane in such a way that its edges do not cross each other. A graph is $k$-planar if it can be drawn on the plane in such a way that each of its edges is ...
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### Name of a space with both a topology and a metric that are not compatible?

Let $(X,\tau,d)$ be a space where $\tau$ is a topology and $d$ is a metric, where the topology $\tau$ is not necessarily compatible with $d$. Is there a canonical name for such a structure (maybe ...
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### $n$-connected spaces (terminology)

A graph is called $n$-connected if it remains connected after removal $\le n$ vertices. Question. What is the name of an analogous property of topological spaces: a space that remains connected after ...
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### What is the name for the construction of this poset related to coherence of degeneracies of the simplex category?

I present you a family of posets here. I don't say the posets themselves have a conventional name. However I'm sure the general construction of this kind has received some terminology, related to ...
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### Does this hexagon theorem have a name - Can I call is Viet Nam hexagon theorem?

Question : Do you know this property of a hexagon - Can I call is Viet Nam hexagon theorem? Consider the configuration: Six points $A_1$, $A_2$, $A_3$, $A_4$, $A_5$, $A_6$ in a plane and let six ...
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### What do you call a scaled orthogonal map?

What do you call a linear map of the form $\alpha X$, where $\alpha\in\Bbb R$ and $X\in\mathrm O(V)$ is an orthogonal map ($V$ being some linear space with inner product)? Are there established names, ...
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To be specific: if $G$ is a finite group and $\operatorname{Irr}(G)$ the set of its irreducible characters (over the complex field) then we know that 1 = \sum_{\phi \in {\rm Irr}(G)} \frac{(d_\phi)^... • 24.1k 1 vote 0 answers 144 views ### Writing the plane as {(x,y,z): x+y+z=0} [closed] One can coordinatize the plane by choosing three axes at 120 degree angles and representing points by triples (x,y,z) with x+y+z=0. Is there an accepted name for this kind of coordinate system? (... • 17.6k 5 votes 0 answers 254 views ### What should you call a Mori Dream Space (or surface) in Spanish? (My apologies if this turns out to be judged to be not appropriate for MathOverflow - I thought about it twice, but then I am nearly certain that I would be much less likely to get an answer there!) &... • 17.2k 10 votes 2 answers 1k views ### Great polyhedra: What does "great" signify? Great Cubicuboctahedron Great Icosacronic Hexecontahedron Great Rhombic Triacontahedron Great Snub Icosidodecahedron Great Stellated Dodecahedron Great Triakis Octahedron ... There are many polyhedra ... • 145k 1 vote 1 answer 99 views ### Functions with periodic sequence of derivative-values Question: is there an established name for the set \Big\lbrace\ f {\Large\ \boldsymbol{|}}\ f\in C^\infty\quad {\Large\boldsymbol{\land}}\quad \exists\,{k\in\mathbb{N}^+}:\frac{d^{i+k}}{dx^{i+k}}f(x)=... • 11.3k 0 votes 0 answers 32 views ### PCA terminology eigenspace / latent space For PCA, it is quite confusing that the terms 'Eigenspace' and 'latent space' are often used interwoven or mixed and multiple researchers define them differently. From my understanding, there are two ... 2 votes 0 answers 172 views ### 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, ... • 823 3 votes 0 answers 75 views ### Terminology question Let K be a commutative ring with unit and suppose that R is a ring that is a left K-module satisfying c(rs)=(cr)s for all c\in K and r,s\in R. We do not require that r(cs)=c(rs) and so ... • 34.7k 7 votes 1 answer 310 views ### Smallest relation in complement of partial order that prohibits its extension Let P be a partial order on a finite set S (assume that every element is related to at least one other element besides itself…this raises a few quick questions: is this implied by the definition ... 1 vote 1 answer 138 views ### Nomenclature for largest odd factor Is there a standard phrase for the largest odd factor of a positive integer n, or more generally for n divided by the largest power of p that divides it (with p some fixed prime)? Five minutes ... • 17.6k 2 votes 0 answers 88 views ### Restricted sumsets - the origins? The sumset of the subsets A and B of an additively written group is defined by A+B:=\{a+b\colon a\in A,\ b\in B\}. The basic idea to add sets has been around since Cauchy at least. Erdős and ... • 21.8k 2 votes 0 answers 91 views ### Has this "optimal constrained transport" notion of convergence of measures been named and/or studied? Let (X,d) be a compact metric space, and let \{\mu_n\}_{n \in \mathbb{N} \cup \{\infty\}} be a family of Borel probability measures on X. Fix L \geq 1. I will say that \mu_n converges in ... 0 votes 0 answers 96 views ### Is there a proper term for a "continuum-convex" set? Let X be a Banach space, and for any compactly supported Borel probability measure \mathbb{P} on X, define the mean \mu_\mathbb{P} by \mu_\mathbb{P}=\int_X x \, \mathbb{P}(dx). I want to say ... 0 votes 1 answer 92 views ### Terminology "upper" Ahlfors regular measure Let (X,d) be a metric space and m be a Borel measure on (X,d). The measure m is called Ahlors regular if m(B(x,r))\asymp r^q for some q>0 and each x\in X. Is there a name for ... • 5,034 0 votes 0 answers 59 views ### Almost exactness - terminology Consider a sequence of (torsion-free) abelian groups \begin{equation*} \dots\stackrel{p}{\longrightarrow} G\stackrel{q}{\longrightarrow}\dots \end{equation*} with the property \begin{equation*} \text{... 2 votes 1 answer 116 views ### Name of the "s" parameter in Ungar's theory of hyperbolic geometry I have done a R package which implements Ungar's approach to hyperbolic geometry, for the hyperboloid model. In this theory, there is a parameter s>0 which controls the curvature of the ... • 2,093 0 votes 0 answers 27 views ### Name for function projecting a 3D point to the surface of aligned sphere Let there be a 3D point \mathbf{P} = \begin{bmatrix} X & Y & Z\end{bmatrix}^{\top} and a sphere \mathcal{S} with radius r and centroid at the origin, everything expressed w.r.t the same ... 2 votes 1 answer 176 views ### Expectation value of inverse covariance matrix when sampling from unit sphere Let X \sim \operatorname{Unif}S_{d-1}, so X\in\mathbb{R}^d and is distributed uniformly on the unit sphere. Then let X_1, \dots, X_n \sim X iid and define the matrix \mathbf{X}\in\mathbb{R}^{n\... • 235 4 votes 0 answers 123 views ### Terminology for the parts of composition? In function composition, binary relation composition, or more generally category theory, are there distinct names for the two things being composed? If we have f:X \rightarrow Y and g:Y \rightarrow ... 21 votes 1 answer 1k views ### What is the name of this relative semidirect product of groups? We have two well known definitions of the semidirect product N \rtimes H of groups: (Internal semidirect product) We write G = N \rtimes H if N is a normal subgroup of G, H is another ... • 92.8k 7 votes 1 answer 204 views ### Direct and inverse image terminology Let f\colon X\to Y be a continuous map. Then f induces a geometric morphism f^\ast\dashv f_\ast\colon \mathrm{Sh}(X)\leftrightarrows\mathrm{Sh}(Y), whose left adjoint is called inverse image and ... • 663 0 votes 1 answer 105 views ### Dart of a graph I want to understand the Dart of a graph. Many authors and also in the book Graphs on surfaces and their applications by Sergei K. Lando, Alexander K. Zvonkin used this term Dart of a Graph/edges. I ... 3 votes 1 answer 108 views ### What is the term for two figures being congruent and of same orientation? In the plane, two figures are called congruent exactly if one can be transformed into the other by translation, rotation, and reflection. What if reflection is excluded, that is, preservation of ... 0 votes 0 answers 39 views ### Selectively countable Boolean algebras of sets (terminology) I am interested in the name for the following property of a Boolean algebra \mathcal A of subsets of a set X: (\star) for any sequence (A_n)_{n\in\omega} of pairwise disjoint nonempty sets in ... • 34.8k 5 votes 3 answers 303 views ### Partitions that are "mutually nested" Let \mathcal{P}_1,\dots,\mathcal{P}_m be a collection of ordered n-partitions of a set \mathcal S, which is to say that that\mathcal{P}_i = \{P^i_1\cup\dots\cup P^i_n\} for all $i$. ...
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In playing with some math finance stuff I ran into the following distribution and I was curious if someone had a name for it or has studied it or worked with it already. To start, let $\Delta^n$ be ...