QCD in a moving frame: an exploratory study

Mattia Dalla Brida, Leonardo Giusti, Michele Pepe, M. Della Morte, P. Fritzsch, E. Gámiz Sánchez, C. Pena Ruano
2018 EPJ Web of Conferences  
The framework of shifted boundary conditions has proven to be a very powerful tool for the non-perturbative investigation of thermal quantum field theories. For instance, it has been successfully considered for the determination of the equation of state of SU(3) Yang-Mills theory with high accuracy. The set-up can be generalized to QCD and it is expected to lead to a similar breakthrough. We present first results for QCD with three flavours of non-perturbatively O(a)-improved Wilson fermions
more » ... shifted boundary conditions. Introduction The understanding of a large variety of phenomena involving the strong interactions, ranging from the dynamics inside a nucleon star to the evolution of the early Universe, crucially depends on the accurate knowledge of the equation of state (EoS) of QCD. In particular, those extreme conditions are now being reproduced and investigated at heavy-ion colliders, where the EoS is an essential input for the analysis of the data [1]. First principles determinations of the EoS of QCD are on the other hand very challenging, as one needs non-perturbative control of QCD over a wide range of temperatures. Even at relatively high temperatures, indeed, standard perturbative methods are characterized by very poor convergence and elaborated techniques are necessary to improve convergence (see e.g. [2] [3] [4] ). Most importantly, due to the asymptotic nature of the perturbative expansion, it is difficult (if not impossible) to access the accuracy of the results within perturbation theory itself (even if apparent convergence is seen), unless one can compare with non-perturbative data over a wide range of temperatures. Therefore, lattice QCD is at present the only known framework that allows us to tackle this problem from first principles, in a fully systematic and predictive way. Results for the EoS of QCD with N f = 2 + 1 quark flavours at zero chemical potential have been recently obtained using well-established lattice techniques [5] [6] [7] : the so-called integral method [8] and its variants. However, although many interesting results have been obtained with these methods, they become computationally very demanding as the temperature is increased, thus limiting in practice the accessible range of temperatures. Most calculations are in fact confined to T 500 MeV. Only very recently results at higher temperatures, i.e. up to 2 GeV, began to appear [9], but reliable continuum extrapolations are still difficult at the highest temperatures. Speaker,
doi:10.1051/epjconf/201817514012 fatcat:xhjykkjwrncnzhcvn7axeesdam