Linked Questions

230 votes
89 answers
45k views

Your favorite surprising connections in mathematics

There are certain things in mathematics that have caused me a pleasant surprise -- when some part of mathematics is brought to bear in a fundamental way on another, where the connection between the ...
147 votes
66 answers
40k views

Important formulas in combinatorics

Motivation: The poster for the conference celebrating Noga Alon's 60th birthday, fifteen formulas describing some of Alon's work are presented. (See this post, for the poster, and cash prizes offered ...
26 votes
5 answers
3k views

Do complex iterates of functions have any meaning?

Using a method explained in this answer to How to solve $f(f(x)) = \cos(x)$?, it is possible to calculate not only integer and real iterates of functions but also complex ones, for example, the $i$-th ...
Anixx's user avatar
  • 10.1k
11 votes
3 answers
684 views

Series and sequences in physical systems & closed form expressions

I gave a colloquium a while ago about physics inspiring recent developments in mathematics and as is almost borderline cliche in such talks, I mentioned the Fibonacci sequence with closed form ...
19 votes
3 answers
2k views

Guises of the Stasheff polytopes, associahedra for the Coxeter $A_n$ root system?

Richard Stanley keeps a famous running compilation of different guises of the celebrated Catalan numbers. The number of vertices of the associahedron is one instantiation among the multitude, and the ...
Tom Copeland's user avatar
  • 10.5k
21 votes
2 answers
2k views

Applications of number theory in dynamical systems

I am looking for references (or ways to find references) on significant and/or recent applications of techniques in number theory to problems in the areas of dynamical systems and nonlinear dynamics. ...
J W's user avatar
  • 760
3 votes
3 answers
637 views

Expansions of iterated, or nested, derivatives, or vectors--conjectured matrix computation

The entry OEIS A139605 (also related OEIS A145271) has a matrix computation for the partition polynomials that represent the expansions of iterated derivatives, or vectors in differential geometry, $...
Tom Copeland's user avatar
  • 10.5k
6 votes
1 answer
409 views

Can there be an application of discrete mathematics in PDEs, mainly the ones used in hydrodynamics?

Can there be applications of graph theory, combinatorics etc. in PDEs mainly hydrodynamics? Tried my luck with Google's search engine, didn't show much info. I guess you can try to use these features ...
Alan's user avatar
  • 1,594
7 votes
0 answers
501 views

intuitive connection between The KdV equations and the Virasoro bott group

I posted this on stack exchange but had no joy, perhaps someone here can answer : The Euler Arnold equation expresses equations (usually from mathematical physics) as geodesic equations on a Lie group....
R Mary's user avatar
  • 979
5 votes
1 answer
289 views

Cataland: Facets and partition polynomials of cluster complexes

Figure 25 on pg. 101 of "Cataland: Why the Fuss?" by Christian Stump, Hugh Thomas, and Nathan Williams depicts cluster complexes (CCs) associated with generalized $(m)$-Narayana / ...
Tom Copeland's user avatar
  • 10.5k
6 votes
0 answers
234 views

Nascent formal group law

$\DeclareMathOperator\FGL{FGL}$The formal group law (cf. Wikipedia, Ex. 1.6 of nLab, Hazewinkel) derived from an analytic function or formal series $f(x) = x + a_2 x^2 + a_3 x^3 + ...$ and its formal ...
Tom Copeland's user avatar
  • 10.5k
3 votes
0 answers
264 views

Guises of the refined Eulerian numbers, generated by tangent vectors (OEIS A145271)

The Eulerian numbers (OEIS A008292, not to be confused with the Euler numbers) pop up in numerous scenarios in combinatorics and advanced analysis, one as the components of the h-vectors of the ...
Tom Copeland's user avatar
  • 10.5k
1 vote
0 answers
252 views

Alternative definition of the Lagrange Inversion formula

While reading this paper, the author provides an alternative definition of the Lagrange inversion formula. Call me crazy, but my intuition tells me that there's something wrong with his derivation. ...
user119264's user avatar
3 votes
0 answers
249 views

Grothendieck schemes and the Sheffer differential op calculus (Rota, Roman, et al. finite operator calculus)

In "Left differential operators on non-commutative algebras" on p. 4, Michiel Hazewinkel displays "precisely the right definition of differential operator" as $$D\; X^n = F(\tfrac{...
Tom Copeland's user avatar
  • 10.5k
1 vote
0 answers
187 views

First to note the relation between Stasheff polytopes (associahedra) and compositional inversion?

In my answer to MO-Q: Enumerative geometry and nonlinear waves, I outline the relation between the refined face polynomials of the Stasheff polytopes (associahedra) and the partition polynomials for ...
Tom Copeland's user avatar
  • 10.5k

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