  The quantum gravity vacuum must contain virtual fluctuations of black hole
microstates. These extended-size fluctuations get `crushed' when a closed
trapped surface forms, and turn into on-shell `fuzzball' states that resolve
the information puzzle. We argue that these same fluctuations can get
`stretched' by the anti-trapped surfaces in an expanding cosmology, and that
this stretching generates vacuum energy. The stretching happen when the Hubble
deceleration reduces quickly, which happens whenever the pressure drops
quickly. We thus get an inflation-scale vacuum energy when the heavy GUTS
particles become nonrelativistic, and again a small vacuum energy when the
radiation phase turns to dust. The expansion law in the radiation phase does
not allow stretching, in agreement with the observed irrelevance of vacuum
energy in that phase. The extra energy induced when the radiation phase changes
to dust may explain the tension in the Hubble constant between low and high
redshift data.
