The great experimental progress in realising and studying polariton condensates has made it possible to now study experimentally a number of fundamental questions about the relation between lasing, condensation, coherence and superfluidity.  In my talk, I will discuss the consequences of finite particle lifetime on several of these questions.  I will discuss the relation between lasing as described by the Maxwell-Bloch equations and polariton condensation, and discuss the consequences of this for both polariton and photon condensation [1].  I will also address aspects of superfluidity [2], pattern formation [3] and coherence[3], and discuss how these are  affected by the finite lifetime of polaritons.

[1] J. Keeling, M. H. Szymanska, and P. B. Littlewood p. 293 of Optical generation and control of quantum coherence in semiconductor
       nanostructures (2010) Eds. G. Slavcheva and P. Roussignol
[2] J. Keeling, Phys. Rev. Lett. 107 080402 (2011) 
[3] J. Keeling and N. G. Berloff Phys. Rev. Lett. 100 250401 (2008)
[4] G. Roumpos et al, Proc. Natl. Acad. Sci, 109 6467(2012)