The Double Dyson Index β Effect in Non-Hermitian Tridiagonal Matrices

The Dyson index, [Formula: see text] , plays an essential role in random matrix theory, as it labels the so-called “three-fold way” that refers to the symmetries satisfied by ensembles under unitary transformations. As is known, its [Formula: see text] 2, and 4 values denote the orthogonal, unitary, and symplectic classes, whose matrix elements are real, complex, and quaternion numbers, respectively. It functions, therefore, as a measure of the number of independent non-diagonal variables. On the other hand, in the case of [Formula: see text] ensembles, which represent the tridiagonal form of the theory, it can assume any real positive value, thus losing that function. Our purpose, however, is to show that, when the Hermitian condition of the real matrices generated with a given value of [Formula: see text] is removed, and, as a consequence, the number of non-diagonal independent variables doubles, non-Hermitian matrices exist that asymptotically behave as if they had been generated with a value [Formula: see text] Therefore, it is as if the [Formula: see text] index were, in this way, again operative. It is shown that this effect happens for the three tridiagonal ensembles, namely, the [Formula: see text] –Hermite, the [Formula: see text] –Laguerre, and the [Formula: see text] –Jacobi ensembles.