Per Alexandersson

Zurich, Switzerland

www2.math.su.se/~per

Age: 28

Currently interested in Schur functions and semistandard Young tableaux and misc. related representation theory and combinatorics.

Phd thesis defended 2013, titled Combinatorial Methods in Complex Analysis.

I keep an eye out for interesting results related to complex dynamics, computability, and computer-assisted research. I use Mathematica extensively in my research. My other main programming languages are Java, LaTeX, PHP, C, etc.

21h
comment When is the Locus of Equi-modular points of two monic polynomials with integer coefficients contained in the unit disk?
Interesting question!
2d
asked Automatically highlight words from a predefined list
2d
comment Young tableau with no i in row i, name that derangement
It is not really a Young tableau, since the columns are not in increasing order, (right)? So maybe use diagram filling instead?
Apr
12
comment Segments on a family of parallel lines
This seems very closely related to Helly's theorem. cut-the-knot.org/pythagoras/ConvexSets/HellysTheorem.shtml
Apr
12
answered Higher Moments, what are they good for?
Apr
8
comment Pattern avoidance in Young diagrams
I rather think of it as matrices with boxes or non-boxes. If you can delete rows and columns of $D$, such that every position with a box in $D'$ has a box in $D$, then $D$ contains $D'$. Note that avoiding $D_1 \cup D_2$ and avoiding $D_2 \cup D_1$ is two different types of avoidance, where $\cup$ means "put $D_1$ up right, and $D_2$ down bottom".
Apr
8
asked Pattern avoidance in Young diagrams
Apr
8
comment Does this sequence always give an integer?
Ah, S. B. Ekhad, that's one of my favourite math authors, although I hear he does all calculations in binary and not decimal...
Apr
7
answered Interesting mathematical documentaries
Apr
5
comment Three-halves-free words (analogous to square-free)
Is there some obvious pattern among the lex-largest elements in these sets?
Apr
5
awarded Notable Question
Apr
1
comment Should one post a paper on the arXiv if it is not intended to be published?
I have seen people put stuff not intended to be published, such as English translations of articles written in another language.
Mar
31
comment Is there any good survey on the hook length formula and related topics?
I believe C. Krattenthaler has some nice proofs of the classical formulas. There is also the notion of hook-formulas for counting linear extensions of certain posets, (Forests, D-complete posets). See the work of Proctor for the latter, unc.edu/math/Faculty/rap
Mar
26
comment For which sidelengths are there polyominos composed of three squares that tile the plane?
There is a notion of a generalized hexagon, all your examples above are such "hexagons", and these tile the plane.
Mar
25
answered The maximal eigenvalue of a symmetric Toeplitz matrix
Mar
22
comment Determinant of a Vandermonde matrix of roots of monic polynomial with integer coefficients
Ah, right, that's true... was too quick there, haha.
Mar
22
answered Determinant of a Vandermonde matrix of roots of monic polynomial with integer coefficients
Mar
20
accepted Positivity of Ehrhart polynomial coefficients
Mar
20
comment Positivity of Ehrhart polynomial coefficients
@RichardStanley Ah, I suspected that was something about that. I wonder what smallest counter-example there is: There is no $5$-dimensional such order polytope, (checked by computer). I got the conjecture about 01-polytopes from an earlier version of a paper I found online, and the final version does not include this conjecture. If you would make your comment into an answer, I would accept that, since this was really the information I was looking for (but not the answer I was hoping for).
Mar
20
reviewed Approve suggested edit on quadratic matrix equation
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