Possibility of \Lambda\Lambda pairing and its dependence on background   density in relativistic Hartree-Bogoliubov model
  We calculate a \Lambda\Lambda pairing gap in binary mixed matter of nucleons and \Lambda hyperons within the relativistic Hartree-Bogoliubov model. Lambda hyperons to be paired up are immersed in background nucleons in a normal state. The gap is calculated with a one-boson-exchange interaction obtained from a relativistic Lagrangian. It is found that at background density \rho_{N}=2.5\rho_{0} the \Lambda\Lambda pairing gap is very small, and that denser background makes it rapidly suppressed. This result suggests a mechanism, specific to mixed matter dealt with relativistic models, of its dependence on the nucleon density. An effect of weaker \Lambda\Lambda attraction on the gap is also examined in connection with revised information of the \Lambda\Lambda interaction. 
Tomonori Tanigawa (JSPS, JAERI), Masayuki Matsuzaki (Fukuoka   University of Education), Satoshi Chiba (JAERI)