Pivot probabilities and norm effects in Gaussian elimination for $β$-ensembles

Abstract: We analyze pivot probabilities in Gaussian elimination with partial pivoting (GEPP) for $2 \times 2$ random matrix ensembles. For GUE matrices, we resolve a previously reported discrepancy between theoretical predictions and empirical observations by deriving the exact pivot probability under standard LAPACK-style implementations. We further show that Dumitriu-Edelman tridiagonal $\beta$-ensembles agree with the earlier theoretical expectations.