In this work, we present a constructive proof of this measure, and propose an algorithm to compute the weights of the decomposition when the contact points are finite.

Based in a joint work with F. Baêta.

We obtain a (partial) theoretical justification of this phenomenon by showing that, given the random $n\times n$ standard Gaussian coefficient matrix $A$, the growth factor of the Gaussian Elimination with Partial Pivoting is at most polynomially large in $n$ with probability close to one. This implies that with probability close to one the number of bits of precision sufficient to solve $Ax = b$ to $m$ bits of accuracy using GEPP is $m+O(\log n)$, which improves an earlier estimate $m+O(\log^2 n)$ of Sankar, and which we conjecture to be optimal by the order of magnitude. We further provide tail estimates of the growth factor which can be used to support the empirical observation that GEPP is more stable than the Gaussian Elimination with no pivoting.

This talk is based on a joint work with Konstantin Tikhomirov.

The $L_p$-sine centroid body $\Lambda_p K$ for a star body $K\subset\mathbb{R}^n$ is a convex body based on the $L_p$-sine transform, and its associated Blaschke-Santal\'{o} inequality provides an upper bound for the volume of $\Lambda_p^{\circ}K$, the polar body of $\Lambda_p K$, in terms of the volume of $K$. Thus, this inequality can be viewed as the ``sine cousin" of the $L_p$ Blaschke-Santal\'{o} inequality established by Lutwak and Zhang. As $p\rightarrow \infty$, the limit of $\Lambda_p^{\circ} K$ becomes the sine polar body $K^{\diamond}$ and hence the $L_p$-sine Blaschke-Santal\'{o} inequality reduces to the sine Blaschke-Santal\'{o} inequality for the sine polar body. The sine polarity naturally leads to a new class of convex bodies $\mathcal{C}_{e}^n$, which consists of all origin-symmetric convex bodies generated by the intersection of origin-symmetric closed solid cylinders. Many notions in $\mathcal{C}_{e}^n$ are developed, including the cylindrical support function, the supporting cylinder, the cylindrical Gauss image, and the cylindrical hull. Based on these newly introduced notions, the equality conditions of the sine Blaschke-Santal\'{o} inequality are settled.

Generalizing the case of circular and semi-circular elements, we also consider $g$, a family of elliptic deformations of $c$, that is $*$-free from $x_0$. Possible degeneracy then prevents a direct calculation of the Brown measure of $x_0+g$. We instead show that the whole family of Brown measures of operators $x_0+g$ are the push-forward measures of the Brown measure of $x_0+c$ under a family of self-maps of the complex plane, which could possibly be singular. We calculate density formulas for various interesting examples.

This work generalizes previous results of Bordenave-Caputo-Chafa\"{i}, Hall-Ho, and a joint work with Ho. The main results offer potential applications to various deformed random matrix models. Our method is based on a Hermitian reduction and subordination functions in free probability.