Johan Wästlund

Gothenburg

http://www.math.chalmers.se/~wastlund/

I'm a researcher at Chalmers University, Gothenburg, with some bias towards discrete probability.
Apr
12
awarded Yearling
Apr
12
awarded Yearling
Apr
4
comment Guessing each other's coins
Has the 81/224-result been written down somewhere?
Apr
1
awarded Curious
Mar
31
asked What is the Bruss-Yor concept of no information?
2017
Dec
6
awarded Famous Question
Feb
28
awarded Popular Question
2016
Jun
22
reviewed Approve suggested edit on Relaxed path decomposition of a graph
Jun
21
revised For which $n$ is there a permutation such that the sum of any two adjacent elements is a prime?
slight mathematical improvement
Jun
18
reviewed Approve suggested edit on The best text to study both incompleteness theorems
Jun
17
comment For which $n$ is there a permutation such that the sum of any two adjacent elements is a prime?
Now checked up to $N=10^{13}$.
Jun
17
answered For which $n$ is there a permutation such that the sum of any two adjacent elements is a prime?
Jun
15
reviewed Approve suggested edit on Path connected set of matrices?
Jun
12
revised For which $n$ is there a permutation such that the sum of any two adjacent elements is a prime?
added 15 characters in body
Jun
12
answered For which $n$ is there a permutation such that the sum of any two adjacent elements is a prime?
Jun
11
comment For which $n$ is there a permutation such that the sum of any two adjacent elements is a prime?
Never mind, by induction (and Chebyshev's theorem on primes), the graph is connected. Moreover, by the same argument it has a perfect matching, and actually two disjoint perfect matchings, which seems relevant to the question.
Jun
8
comment For which $n$ is there a permutation such that the sum of any two adjacent elements is a prime?
Does anyone have a proof that the graph (with vertices $1,\dots,N$ and edges where pairs of numbers sum to a prime) is connected? Equivalently, if we color the numbers $1,\dots, N$ red and blue in such a way that the sum of two (distinct) numbers of the same color is never prime, did we necessarily color according to parity? It seems we have to use number theory of at least the level of Chebyshev in order to show that there aren't any isolated vertices, so it can't be entirely trivial.
2015
Dec
7
reviewed Approve suggested edit on In a random graph which one is more probable, $k$-clique or $k$-core?
Dec
3
awarded Nice Answer
Oct
30
awarded Favorite Question
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