Lower Bound of Concurrence Based on Positive Maps
  We study the concurrence of arbitrary dimensional bipartite quantum systems. An explicit analytical lower bound of concurrence is obtained, which detects entanglement for some quantum states better than some well-known separability criteria, and improves the lower bounds such as from the PPT, realignment criteria and the Breuer's entanglement witness. 
Xiao-Sheng Li, Xiu-Hong Gao, Shao-Ming Fei
quant-ph