Random matrix theory and spectral sum rules for the Dirac operator in QCD

We construct a random matrix model that, in the large $N$ limit, reduces to the low energy limit of the QCD partition function put forward by Leutwyler and Smilga. This equivalence holds for an arbitrary number of flavors and any value of the QCD vacuum angle. In this model, moments of the inverse squares of the eigenvalues of the Dirac operator obey sum rules, which we conjecture to be universal. In other words, the validity of the sum rules depends only on the symmetries of the theory but not on its details. To illustrate this point we show that the sum rules hold for an interacting liquid of instantons. The physical interpretation is that the way the thermodynamic limit of the spectral density near zero is approached is universal. However, its value, $i.e.$ the chiral condensate, is not.Comment: 18 pages, SUNY-NTG-92/4

Spectrum of the Dirac operator in a QCD instanton liquid: two versus three colors

Approximating the sum over all gauge field configurations in the QCD partition function by a liquid of instantons, we calculate the spectrum of the Dirac operator for two and three colors and for 0, 1 and 2 flavors. We find a remarkable difference in the spectrum near zero virtuality between 2 and 3 colors, which can be explained in terms of chiral random matrix theory. For two colors the Dirac operator is real, and the appropriate random matrix ensemble has real matrix elements. For three colors the Dirac operator is complex, and the spectrum can be described by a random matrix ensemble with complex matrix elements. These results provide further evidence that the spectrum near zero virtuality is universal and is completely determined by symmetries.Comment: 12 pages and 2 figures (available on request), SUNY-NTG-94/

Which investors fear expropriation? Evidence from investors' stock picking

Includes bibliographical references. Title from cover. Also available via the InternetAvailable from British Library Document Supply Centre- DSC:3597. 9512(no 3843) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo