show/hide this revision's text 2 added what is k; edited body

Lets have two Hermitian $n\times n$ matrices $X$ and $Y$.

Are there any known properties of the singular values of $$Z = X + i Y$$ which are not generic?Y.$$

I am the most interested in bounding from above a few first singular values of $Z$ by the eigenvalues of $X$ and $Y$. And sth that is stronger than:

$$\sum_{i=1}^k \sigma_i^2(Z)\leq \sum_{i=1}^k \left( \lambda_i^2(X)+\lambda_i^2(Y)+\lambda_i(i[X,Y]) \right)$$ for $1\leq k \leq n$ and (singular/eigen)values sorted in the decreasing order.

show/hide this revision's text 1

Singular values of $X+iY$ where $X$ and $Y$ are Hermitian

Lets have two Hermitian $n\times n$ matrices $X$ and $Y$.

Are there any known properties of the singular values of $$Z = X + i Y$$ which are not generic?

I am the most interested in bounding from above a few first singular values of $Z$ by the eigenvalues of $X$ and $Y$.