Multiplicity and Pt Correlations in AA-interactions at High Energies
  The theoretical description of the correlations between observables in two separated rapidity intervals in relativistic nuclear collisions is presented. It is shown, that the event-by-event pt-pt correlation defined as the correlation between event mean values of transverse momenta of all particles emitted in two different rapidity intervals does not decrease to zero with the increase of the number of strings in contrast with two particle pt-pt correlation - the correlation between the transverse momenta of single particles produced in these two rapidity windows.   In the idealized case with the homogeneous string distribution in the transverse plane in the framework of the cellular analog of string fusion model (SFM) the asymptotic of pt-pt correlation coefficient is analytically calculated and compared with the results of the Monte-Carlo (MC) calculations fulfilled both in the framework of the original SFM and in the framework of its cellular analog, which enables to control the MC algorithms.   In the case with the realistic nucleon distribution density of colliding nuclei the results of the MC calculations of the pt-pt correlation function for minimum bias nuclear collisions at SPS, RHIC and LHC energies are presented and analysed. 
R. S. Kolevatov, V. V. Vechernin (St.Petersburg State University)