Name: Masahiro Morikawa
 Institution: Department of Physics, Ochanomizu University
 Title: Accelerations and dissipative reduction of vacuum energy in BEC cosmology
 Key Words: dark-matter/energy, condensation, acceleration, inflation, stagflation
 Abstract: Dark energy (DE) and dark matter (DM) exist in the same amount at present. This fact motivates us to believe DE and DM are essentially the same object. We construct a model in which DE and DM are identified, respectively, with the Bose-Einstein condensate and the excited gas of some boson field. The condensation dynamics is quite different from the ordinary scalar field and yields both strong instability and the asymptotic stability depending on the condensate density. 
In the late universe, the strong instability yields the collapse of BEC to form local structures including huge black holes at around z=10. The asymptotic stability yields the accelerated cosmic expansion at present which predicts w parameter -1 after z= 3. 
In the early universe, BE condensation starts the inflationary acceleration of the universe and yields the reasonable spectrum of density fluctuations. Then the inflation is suddenly terminated by the very strong instability of BEC. The uniform mode of BEC rapidly collapses toward fragments to yield radiation dominated stage, reducing the vacuum energy initially present. This dissipative decay of condensates repeats many times and the effective cosmological constant successively reduces autonomously toward zero. 
Thus we would like to emphasize the paradigm of condensate astrophysics, which goes beyond the popular particle astrophysics.