Gravitational waves, dark energy and inflation
  In this paper we first present a complete classification of gravitational
waves according to their frequencies: (i) Ultra high frequency band (above 1
THz); (ii) Very high frequency band (100 kHz - 1 THz); (iii) High frequency
band (10 Hz - 100 kHz); (iv) Middle frequency band (0.1 Hz - 10 Hz); (v) Low
frequency band (100 nHz - 0.1 Hz); (vi) Very low frequency band (300 pHz - 100
nHz); (vii) Ultra low frequency band (10 fHz - 300 pHz); (viii) Hubble
(extremely low) frequency band (1 aHz - 10 fHz); (ix) Infra-Hubble frequency
band (below 1 aHz). After briefly discussing the method of detection for
different frequency bands, we review the concept and status of space
gravitational-wave missions --- LISA, ASTROD, ASTROD-GW, Super-ASTROD, DECIGO
and Big Bang Observer. We then address to the determination of dark energy
equation, and probing the inflationary physics using space gravitational wave
detectors.
