Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 6794

Questions designed to generate a "big list" of certain results, examples, conjectures, etc. via many individual answers, each contributing one or a few instances. Such a question should typically be in Community Wiki mode (CW); after asking, please, flag for moderators attention requesting the question to be made CW.

6 votes

Mathematicians with both “very abstract” and “very applied” achievements

Dana Scott's achievements include work in pure set theory and also work in computer science. He proved that there are no measurable cardinals in Gödel's constructible universe and (with Solovay) devel …
Martin Sleziak's user avatar
1 vote

Equivalence relations not associated with a group

Since this question has been bumped to the front page, let me add Turing equivalence of subsets of $\mathbb N$. (Two such subsets are Turing equivalent iff each is computable by a Turing machine equip …
Andreas Blass's user avatar
20 votes

Noteworthy, but not so famous conjectures resolved recent years

Maryanthe Malliaris and Saharon Shelah proved that the cardinal characteristics $\mathfrak p$ and $\mathfrak t$ are equal, answering a question that goes back at least to the 1970's and probably (with …
Andreas Blass's user avatar
4 votes

Math talk for all ages

I like to show how the same mathematics shows up in very different contexts. A topic that I've used with quite varied audiences (though never with as much variation in a single audience as you have) i …
Andreas Blass's user avatar
21 votes

Nonequivalent definitions in Mathematics

An extension of a group $A$ by a group $B$ can be either a group $G$ with a normal subgroup isomorphic to $B$ with $G/B$ isomorphic to $A$ or a group $G$ with a normal subgroup isomorphic to $A$ with …
Andreas Blass's user avatar
10 votes

Important results with one or more than one proof

The first example that occurs to me is Hindman's theorem: If the set of positive integers is partitioned into finitely many pieces, then there is an infinite set $H$ such that all sums of finitely man …
Andreas Blass's user avatar
8 votes

Are there any good nonconstructive "existential metatheorems"?

Gödel's second incompleteness theorem leads to a curious example as follows. The diagonalization method (as in the proof of the first incompleteness theorem) produces, for any reasonable theory T tha …
cody's user avatar
  • 1,452
252 votes

What are some examples of colorful language in serious mathematics papers?

Does merely transposing two words count? "It is also hard not to show that ..." [Arnold W. Miller, "Some Properties of measure and category," Trans. A.M.S. 266, 1981, p. 106]
Danu's user avatar
  • 119
31 votes

Mathematicians who made important contributions outside their own field?

Paul Cohen was an analyst but got a Fields Medal for his work in set theory, proving the independence of the continuum hypothesis from ZFC and the independence of the axiom of choice from ZF.
Andreas Blass's user avatar
21 votes

Structures that turn out to exhibit a symmetry even though their definition doesn't

Consider the Desargues configuration. It consists of (1) two triangles, say $ABC$ and $A'B'C'$ such that the lines $AA'$, $BB'$, and $CC'$ all meet at a point $P$, and (2) the three points of intersec …
Andreas Blass's user avatar
6 votes

Classic applications of Baire category theorem

I got some mileage out of the Baire category theorem in abelian group theory, in particular in the study of the group $\mathbb Z^{\aleph_0}$, the additive group of sequences of integers (which, contra …
Andreas Blass's user avatar
3 votes

How should the Math Subject Classification (MSC) be revised or improved?

My experience has been that the editors of Math Reviews pay attention to suggestions about revisions of the classification system. I'm not saying that they implement all the suggestions (especially b …
Andreas Blass's user avatar
22 votes

Examples of theorems with proofs that have dramatically improved over time

I described an example, Hindman's theorem, at https://mathoverflow.net/questions/94546 . The short version is that Hindman's original proof was unpleasantly complicated, whereas a later proof by Galv …
Community's user avatar
  • 1
5 votes

Fundamental Examples

Motivated by Amit Kumar Gupta's answer about the continuum hypothesis, let me add an example that is less natural but has inspired an amazing amount of set theory, namely Suslin's Hypothesis. This co …
Andreas Blass's user avatar
1 vote

Mathematical ideas named after places

The Conway-Paterson-Moscow theorem
Ben Webster's user avatar
  • 44.7k

15 30 50 per page