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1 vote
0 answers
134 views

Number of ways to place 4 kings on nxn chessboard

I have a $n\times n$ chessboard and 4 kings inside it. My goal is to count the number of arrangements where some of them are non-attacking or mutually attacking, for example: In the case where the $4$...
3 votes
0 answers
420 views

(Expected) Size of smallest singular value of a Vandermonde matrix associated to roots of polynomial

Let $n,H$ two fixed positive integers. Let $P\in\mathbb{Z}[X]$ a monic integral polynomial of height $H$ and degree $n$ taken uniformly at random (i.e. each of the $n$ free coefficients of $P$ is ...
29 votes
3 answers
3k views

Perron-Frobenius "inverse eigenvalue problem"

The Perron-Frobenius theorem says that the largest eigenvalue of a positive real matrix (all entries positive) is real. Moreover, that eigenvalue has a positive eigenvector, and it is the only ...