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 935

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.

142 votes

Examples of theorems misapplied to non-mathematical contexts

A tragic example of this is the case People v. Collins, in which a prosecutor asked a mathematician (as an expert witness) a question of the form, "assuming these events are independent, what is the p …
59 votes

Fundamental problems whose solution seems completely out of reach

A proof of this conjecture of Erdos would certainly turn heads, raise eyebrows, and garner the attention of the Fields Medal committee. If $\sum_{a \in A} \frac 1a$ diverges and $A\subseteq {\mathbb …
59 votes

Examples of eventual counterexamples

Freeman Dyson observed in my presence that the sequence with initial condition $a_0=3,a_1=0,a_2=2$, and recurrence $a_{n+3}=a_{n+1}+a_{n}$ almost has the property that $n\mid a_n$ if and only if $n$ i …
55 votes

Interesting Calculus Questions/Exercises

The theorems of calculus that you mention are all obviously true, and so a proper bed must be made for their discussion to not seem pedantic. Counterexamples are crucial, of course. Three of my favori …
53 votes

Why linear algebra is fun!(or ?)

An example that my last class loved was lossy image compression using the singular value decomposition. The SVD says that the transformation corresponding to any real matrix (not necessarily square) …
43 votes

Fundamental problems whose solution seems completely out of reach

This comes up in Waring's Problem, but it is so freakishly simple that it has taken on a life of its own. Let $\{ x \} = x \mod 1 = x-\lfloor x \rfloor$ be the fractional part of $x$. Say anything ab …
37 votes
Accepted

What are some results in mathematics that have snappy proofs using model theory?

Hilbert's Nullstellensatz is a consequence of the model completeness of algebraically closed fields. Edit: I don't have a reference, but I can sketch the proof. Suppose you have some polynomial equati …
Kevin O'Bryant's user avatar
22 votes

Fundamental problems whose solution seems completely out of reach

Artin's Conjecture: There are infinitely many primes $p$ for which 2 is a primitive root, i.e., 2 generates the multiplicative group of ${\mathbb Z}/p{\mathbb Z}$. The conjecture is actually a bit mo …
18 votes

How helpful is non-standard analysis?

Freiman conjectured a classification of finite sets $A$ of integers that have $$\lvert A+A\rvert = 3\lvert A\rvert-3+b$$ for some $0\leq b \leq \lvert A\rvert/3-2$. Renling Jin recently resolved this …
Kevin O'Bryant's user avatar
13 votes

Computer algebra errors

In Mathematica 7, the command Table[DirichletCharacter[4, 2, n], {n, 0, 8}] should return a list of values of the character with modulus 4 and index 2, evaluated at 0, 1, 2, ..., 8. Instead, it retu …
11 votes

Papers that debunk common myths in the history of mathematics

There have been recent articles in The Mathematical Intelligencer about the well-known rivalry/animosity between Erdős and Selberg. Didier adds this link, pointing to an article of Graham and Spencer …
8 votes

Compilation of strategies to show that some constant is irrational

Don't forget the obvious: If the digits of $\alpha$ in any base are not eventually periodic, then $\alpha$ is irrational. Mel Nathanson and I (Integers 14 (2014), A40, pp. 1--11) used this to prove th …
Kevin O'Bryant's user avatar
8 votes

Which journals publish expository work?

The front page of the Notices (Jan 2011) is an advertisement for the "Bulletin of Mathematical Sciences". The "Aims and Scope" are: The Bulletin of Mathematical Sciences, a peer-reviewed free acce …
7 votes

nonstandard analysis book recommendation

I loved Goldblatt's book, "Lectures on the Hyperreals". For a more sophisticated treatment, don't overlook "Nonstandard Analysis: Theory and Applications", edited by Henson (first chapter available t …
7 votes

Computer algebra errors

Just found this in Mathematica 7.0 for Mac OS X x86 (64-bit) (November 11, 2008): x=Exp[Pi Sqrt[163] ]; N[x-Round[x] ] N[x-Floor[x] ] N[x-Ceiling[x] ] N[x - Round[x], 2] N[x - Floor[x], 2] N[x - Ceil …

15 30 50 per page