Federico Poloni
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 1d comment Is there an image for you that epitomizes mathematics? This one comes close: quantamagazine.org/wp-content/uploads/2015/10/ErdosTao_Main.jpg Apr 15 comment Determinant of a certain Vandermonde matrix Aren't $n$ complex numbers always the roots of a polynomial of degree $n$? Apr 15 awarded Popular Question Apr 10 reviewed Approve fourier-analysis tag wiki excerpt Apr 10 reviewed Approve algebraic-groups tag wiki excerpt Apr 10 reviewed Approve duality tag wiki excerpt Apr 10 comment SVD when only off-diagonal terms are known If you can easily estimate off-diagonals, can you change basis and use this to estimate the diagonal? The opposite (polarization identities) is a well-known trick. Apr 1 comment Looking for tighter bounds A colleague of mine, Leonardo Robol, defended a thesis on the numerical solution of this kind of equations as a method to compute eigenvalues and polynomial zeros. Mar 29 answered Finding eigenvalues of an 'almost-tridiagonal' circulant matrix Mar 23 reviewed Approve fractional-iteration tag wiki Mar 20 comment Is Gaussian the unique 2-stable distribution? I browsed through the wikipedia page you linked, and I have read the answer stated in at least three different places. And there are references. Do you ask this because you believe that the result stated there is false and they are missing a technical hypothesis? Mar 17 answered Where can square roots come from when they are not distances? Mar 17 comment Where can square roots come from when they are not distances? As a matrix guy, I would say that the square root here arises as an eigenvalue of the transformation $\begin{bmatrix}1 & 1 \\ 1 & 0\end{bmatrix}$, so a more general answer in this theme would be as eigenvalues. This may just be my skew view on things, though. Mar 15 comment For a ring R, does $GL_n(R)$ embed into $GL_m(F)$ for some field F? So $F$ is not commutative either? It seems difficult to embed a non-abelian group into a commutative field... Mar 15 comment For a ring R, does $GL_n(R)$ embed into $GL_m(F)$ for some field F? The ring must be commutative, at least, I presume? Mar 13 reviewed Approve Generalizations of the Tietze extension theorem (and Lusin's theorem) Mar 10 revised Polynomial bijection from ZxZ to Z? grammar Mar 8 comment Are the coefficients of a linear combination of random vectors as random? @Rob Same comment: so, essentially, you want to find the distribution of the entries of $X^{-1}Y$? That is what the coefficients of that linear combinations are. Mar 7 comment Are the coefficients of a linear combination of random vectors as random? So, essentially, find the distribution of $X^{-1}y$, where $X$ is obtained by stacking the $x_i$'s horizontally? Mar 4 comment Need help with computational and numerical methods for solve equations Start from en.wikipedia.org/wiki/Root-finding_algorithm, or (even better) from any undergraduate numerical analysis book.