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### Why are they called 'pernicious' numbers?

The definition of a pernicious number: In number theory, a pernicious number is a positive integer where the Hamming weight (or digit sum) of its binary representation is prime. The meaning of ...
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### Name of a difference of continuants

I am getting ready to publish the manuscript http://arxiv.org/pdf/1408.4631v2.pdf and I am trying to do due diligence on a quantity I study before it gets published. (This is cross-posted from ...
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### Proving identity involving delta-functions

Lately I came across the following identity: ...
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### The ten martini problem - reason for name

Why is the problem called the ten martini problem? Sounds like an interesting name for people who drink.
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### Morphisms every pushout of which is a weak equivalence

Let $M$ be a category equipped with a class of weak equivalences $W$. Is there a name for a morphism $f$ such that every pushout of $f$ (including, of course, $f$ itself) is a weak equivalence? For ...
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### Naming ambiguity in constructive pointwise natural transformations and whiskering

In the HoTT Book, the choice is made to talk about whiskering, rather than horizontal composition, because horizontal composition is ambiguous and only defined up to paths. Naturally, there is left ...
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### How is Munkres pronounced? [closed]

How is the algebraic topologist James R. Munkres' last name "Munkres" pronounced? Is it "Munkrees" or "Munkers" or something else entirely? There is some disagreement among my acquaintances. ...
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### “Bell” or “Jabotinsky”-matrix - What's the canonical name (if any)?

I'm just reading J. Cigler's script for his talks "Konkrete Analysis" where I find the term "Jabotinsky-matrix" for that matrix, which I've (informally) been taught to call "Bell-matrix" (see at least ...
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### Generalising right-angled Artin groups

An Artin group $G$ is determined by its Coxeter matrix $M$. This is a symmetric $n \times n$ matrix with entries from $\lbrace 2, 3, \ldots, \infty \rbrace$ that determine the relations between the ...
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### Pronunciation: Vaughan Jones [closed]

Is it like "Vonn" as given here: http://www.merriam-webster.com/dictionary/vaughan
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### What is the quantity 2(handles)+crosscaps called?

It is well-known that up to homeomorphism, the complete set of orientable surfaces is $\lbrace S_g : g=0,1,\dots \rbrace$, where $S_g$ is the sphere with $g$ handles. The complete set of ...
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### fgf = f, gfg = g, fg not necessarily identity, what was that called?

A very simple question, I just totally forgot how it was called, and google is not helping. There's a pair of functions $f:X\to Y$, $g:Y\to X$. $fgf = f$, $gfg = g$, but $fg$ and $gf$ don't need to ...
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### Why are they called Spherical Varieties?

My understanding is if you have a homogeneous space $X = G/H$ for a reductive group $G$ and $X$ is normal and has an open $B$-orbit, for a Borel subgroup $B$ then you call $X$ spherical. Someone ...
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### Names of finite groups

Question: If you have a finite group, how do you name it? If, for whatever reason, you have to list all subgroups of $GL_2({\mathbb F}_5)$ up to isomorphism in a paper, you are likely to write ...
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### What do named “tricks” share?

There are a number of theorems or lemmas or mathematical ideas that come to be known as eponymous tricks, a term which in this context is in no sense derogatory. Here is a list of 10 such tricks (the ...
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### What's coherent about coherent sheaves?

In a recent answer to a recent question, BCnrd wrote [...] beyond the coherent case one cannot expect information about a fiber (e.g., vanishing, 6 generators, etc.) to "propogate" to information ...
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