RBRC Seminar

Abstract: A new approach is presented to explore the singularity structure of lattice QCD in the complex chemical potential and fugacity plane. Our method can be seen as a combination of the Taylor expansion and analytic continuation approaches. Its novelty lies in using multi-point Padé approximants for studying Lee Yang edge singularities, which provide valuable insights to the occurrence of critical phenomena in the thermodynamic limit. Several numerical experiments have been performed to test and demonstrate its accuracy and stability. The new method, as well as the standard Padé method is applied to lattice data, obtained with highly improved staggered quarks (HISQ) at temporal lattice extent of Nτ = 4,6,8. We discuss the universal scaling behaviour of the Lee-Yang edge singularity and its role as a brunch-cut singularity in the order parameter. We inspect scaling of the singularities in the vicinity of the Roberge-Weiss and chiral phase transitions. We find a temperature scaling that is in accordance with the expected power law behavior and determine some previously unknown non-universal constants. Finally we discuss the possibility to detect also the QCD critical end-point, if it exists, by this new method.