6,219 reputation
22242
bio website fph.altervista.org
location Pisa, Italy
age 31
visits member for 5 years
seen 6 hours ago

Numerical linear algebra. Mainly matrix equations and their applications (control theory, applied probability).


Nov
18
awarded  Yearling
Nov
16
comment Open source mathematical software.
Is the list of capabilities missing, or is it the empty set? :)
Nov
16
comment Open source mathematical software.
@kundor Actually the Geogebra page on licensing now seems clearer than when I wrote my previous comment. The program itself is GPL, and the additional restrictions are on additional components such as the web plugin, the installer and the translations of the interface in other languages. I still disagree with the claim "GeoGebra is open source software", but at least everything is consistent.
Nov
16
comment Open source mathematical software.
@kundor Sure, but you cannot forbid those who already have the software from redistributing it (even to commercial users), which usually makes selling it quite pointless. The commercial use clause falls under the "further restrictions" cause and is invalid in my view. And the contradiction (1)-(2) stands clear in the OSI definition, if one assumes that as the definition of open source.
Nov
15
comment Obscure Names in Mathematics
Similar to the Killing-Hopf theorem, the Italian name for the Gaussian elimination method sounds like someone is debating on the best way to kill poor C.F. Gauss.
Nov
14
comment Modified Orthonormal Procrustes Problem
You're right, sorry, my bad. :/
Nov
14
comment Modified Orthonormal Procrustes Problem
If $C$ is square and orthogonal, $||Y-XC||_F=||(Y-XC)C^T||_F=||YC^T-X||_F$, since the Frobenius norm is invariant by orthogonal transformation. Am I missing something?
Nov
11
comment iterative solution better than analytic solution?
There are exact formulas that are less accurate than an iterative algorithm. There should be examples for problems as simple as solving a quadratic, if you take a case when the "textbook" exact formula uses dangerous subtractions.
Nov
10
revised About Sylvester's determinant
two versions of Schur cpl
Nov
10
revised About Sylvester's determinant
added reference to Schur complements.
Nov
10
answered About Sylvester's determinant
Nov
4
comment minimal polynomial for a graph
Your statement on Krylov subspaces seems false; counterexample: take $v$ equal to an eigenvector of $Q$. The claim holds if you reverse the order of quantifiers (the least $m$ such that for each $v$ $K_m(A,v)$ is $Q$-invariant is $d$).
Nov
3
comment Partial inverse of a matrix - or does it have its own name?
@PiotrMigdal Another one of its many names is exchange operator. Maybe you find that more enlightening?
Nov
3
comment Partial inverse of a matrix - or does it have its own name?
@PiotrMigdal Yes, it's one of those operations that pop up unexpectedly in lots of different fields. It is interesting to find out that it has an application in optics, too!
Nov
2
reviewed Approve suggested edit on moduli-spaces tag wiki excerpt
Nov
2
answered Partial inverse of a matrix - or does it have its own name?
Nov
2
comment When exactly and why matrix multiplication became a part of undergraduate curriculum?
The formula reported in your picture is not $C=AB$ but $C=A^TB$, and the Italian text translates to "The product of two determinants of the same order can be expressed as a single determinant as follows.". So someone with more free time than I have could argue that this is not a matrix product, but simply a composition rule for determinants that happens to be related to it.
Nov
2
revised math-education-history wiki excerpt
added 33 characters in body
Nov
2
wiki created math-education-history excerpt
Nov
2
suggested suggested edit on math-education-history tag wiki excerpt