Stationary configurations of two extreme black holes obtainable from the Kinnersley-Chitre solution

Stationary axisymmetric systems of two extreme Kerr sources separated by a massless strut, which arise as subfamilies of the well-known Kinnersley-Chitre solution, are studied. We present explicit analytical formulas for the individual masses and angular momenta of the constituents and establish the range of the parameters for which such systems can be regarded as describing black holes. The mass-angular momentum relations and the interaction force in the black-hole configurations are also analyzed. Furthermore, we construct a charging generalization of the Kinnersley-Chitre metric and, as applications of the general formulas obtained, discuss two special cases describing a pair of identical co- and counterrotating extreme Kerr-Newman black holes kept apart by a conical singularity. From our analysis it follows in particular that the equality $m^2-a^2-e^2=0$ relating the mass, angular momentum per unit mass and electric charge of a single Kerr-Newman extreme black hole is no longer verified by the analogous extreme black-hole constituents in binary configurations.Comment: final version revised according to referee's suggestion

Self-consistent treatment of the quark condensate and hadrons in nuclear matter

We calculate the contribution of pions to the $\bar qq$-expectation value $\kappa(\rho)=$ in symmetric nuclear matter. We employ exact pion propagator renormalized by nucleon-hole and isobar-hole excitations. Conventional straightforward calculation leads to the "pion condensation" at unrealistically small values of densities, causing even earlier restoration of chiral symmetry. This requires a self-consistent approach, consisting in using the models, which include direct dependence of in-medium mass values on $\kappa(\rho)$, e.g. the Nambu-Jona-Lasinio-model. We show, that in the self-consistent approach the $\rho$-dependence of the condensate is described by a smooth curve. The "pion condensate " point is removed to much higher values of density. The chiral restoration does not take place at least while $\rho<2.8\rho_0$ with $\rho_0$ being the saturation value. Validity of our approach is limited by possible accumulation of heavier baryons (delta isobars) in the ground state of nuclear matter. For the value of effective nucleon mass at the saturation density we found $m^*(\rho_0)=0.6m$, consistent with nowadays results of other authors.Comment: 26 pages, LaTeX, 9 PostScript figures, epsfig.sty; sent to the European Physical Journal

Nucleon QCD sum rules in nuclear matter including radiative corrections

We calculate the nucleon parameters in nuclear matter using the QCD sum rules method. The radiative corrections to the leading operator product expansion terms are included, with the corrections of the order \alpha_s beyond the logarithmic approximation taken into account. The density dependence of the influence of radiative corrections on the nucleon parameters is obtained. At saturation density the radiative corrections increase the values of vector and scalar self-energies by about 40 MeV, and 30 MeV correspondingly. The results appear to be stable with respect to possible variations of the value of \Lambda_{QCD}.Comment: 16 pages, 2 figure

Role of unphysical solution in nucleon QCD sum rules

We show that at certain values of QCD condensates the nucleon QCD sum rules with "pole+continuum" model for the hadron spectrum obtain an unphysical solution. This provides constrains for the values of condensates to be consistent with existence of a physical solutions. The constrains become much weaker if the radiative corrections are included perturbatively. We demonstrate that the most important dependence of nucleon mass on the quark scalar condensate becomes much weaker under factorization assumption for the four-quark and six-quark condensates.Comment: 13 pages, 6 figure