Title: Energy from the QCD vacuum 
Speaker: Prof.Vahtang Gogokhia (WIGNER RCP) 
Time: 10:00AM, Apr.27th 2017 (Thursday) 
Place: Theoretical Physics Division，319 
Abstract: Using the effective potential approach for composite operators, we have formulated a general method of calculation of the truly non-perturbative Yang-Mills vacuum energy density (VED), which is, by de nition, the bag constant apart from the sign. It is the main dynamical characteristic of the QCD ground state.Our method allows one to make it free of all the types of the perturbative contributions (contaminations), by construction. We also perform an actual numerical calculation of the bag constant as a function of the mass gap. It is this which is responsible for the large-scale dynamical structure of the QCD ground state. The existence of the stable (being in the stationary state with minimum energy) purely transversal virtual gluon eld con gurations has been explicitly shown. Using further the trace anomaly relation, we develop a general formalism which makes it possible to relate the bag constant to the gluon condensate de ned at the same function (or, equivalently, effective charge) which has been chosen for the calculation of the bag constant itself. Our numerical result for it shows a good agreement with other phenomenological estimates of the gluon condensate. We have argued that the calculated bag constant may contribute to the dark energy density. Its contribution is by 10 orders of magnitude better than the estimate from the Higgs eld's contribution. We also propose to consider the bag energy as a possible amount of energy which can be released from the QCD ground state by a single cycle. The QCD ground state is shown to be an in nite and hence a permanent reservoir of energy.