Per Alexandersson

less info
773 reputation
313
bio website www2.math.su.se/~per
location Zurich, Switzerland
age 27
visits member for 2 years, 7 months
seen 1 hour ago

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.


Aug
8
comment How can I use the Klingon alphabet symbols?
@Mr.Wizard: Well, I play around a lot with Schur polynomials, which are characters of GLn, and also irreducible characters of Sn. In general, I would like access to structure constants, such as Littlewood-Richardson coefficients, Kostka coefficients and Kronecker coefficients. My question about generating Gelfand-Tsetlin patterns on this site can be used to compute Kostka numbers, for example. LR-coefficients can be computed by counting lattice points in polytopes, another thing I really think Mathematica could be better at.
Aug
8
comment How can I use the Klingon alphabet symbols?
Ok, so you are telling me, that the MATHEMATICAL software supports Klingon characters, but not irreducible characters...
Aug
7
comment $SU(4)$ Structure constants in mathematica
Mathematica is perhaps not the best software for the task; i think there are better suited programs out there tat has these built-in.
Jun
16
comment Smooth Peter de Jong attractor
@Kuba: The implementation I have is written in Java, and is open-sourced here: sourceforge.net/projects/flamethyst Some images created can be found here: people.su.se/~peal0658/index.php?page=fractals
Jun
16
comment Smooth Peter de Jong attractor
Google "Flame fractals". I create this type of fractals a lot; 10⁵ is not nearly enough iterations. You would like about 2000 iterations PER PIXEL in the final image to get a decent result.
Jun
14
comment Extract memoized results in the form of a rule
Ah, yes, of course! I feel silly now.
Jun
10
comment State “i” goes to state “j”
I would guess it means states accessible from either 1 or 4.
May
8
comment Mathematica sporadically crashes on open
Because, that makes sense... sometimes, one wonders...
Mar
28
comment Creating sculptural forms using graphics primitives
Thanks! Absolutely not, I was just a bit lazy to add it myself :)
Mar
16
comment Finding lags of time series with `Do`
Oh, L[t_]:=t-k; should most definitely work. But dont use capital letters as variable names, these might already be used by Mathematica, in any case, it is bad practice.
Mar
16
comment Finding lags of time series with `Do`
Oh, you want ListPlot[L/@Range[5,100]]
Mar
16
comment Finding lags of time series with `Do`
Hm, ok, well, I am not entirely sure what info you got, and what is unknown...
Mar
5
comment Generating Gelfand-Tsetlin patterns
@belisarius cf = Flatten[stuff,1] can be optimized to cf = Join@@(stuff).
Mar
5
comment Generating Gelfand-Tsetlin patterns
@IstvánZachar Are there any performance issues with Return? I read that it is a bit quirky, and is more "procedural" than "functional", so is it something to avoid in general?
Mar
5
comment Generating Gelfand-Tsetlin patterns
@IstvánZachar Oh, ok, is there a particular reason why one wish to avoid return? I am probalby just used to Java, so it feels easier to read in this manner.
Mar
5
comment Generating Gelfand-Tsetlin patterns
Wow, this is very efficient! How does the algorithm work? I took the liberty of adding an extra check in findPaths; looks like some corner cases mess up your code otherwise.
Mar
1
comment Dot shading a.k.a. Stippling effect
Ah, cool! I had some feeling I might have seen it somewhere, so yes, it is perhaps best to close this. Thanks!
Feb
25
comment Generating Gelfand-Tsetlin patterns
I have some other functionality that I have coded that does not exist in Sage. Besides, I am not sure, but I don't think Sage supports skew patterns, only "regular" ones.
Feb
21
comment Finding connected components in an array
Oh, I am looking forward to that post!
Feb
20
comment Finding connected components in an array
Looks interesting, I will try it out tomorrow :). Good performance there!