Does Hawking's imaginary time idea have any impact on Guth's repulsive gravity theory for Inflationary cosmology?

Not that I know of. These are two different phenomena predicted theoretically. Hawking's process occurs near the Planck Era and involves the metric of spacetime changing its character ( specifically its signature) due to quantum fluctuations. The current metric looks like:


  2         2   2            2
ds     = - c  dt   + R(t)( dS  )
                    ------------
                              2
                       1 - k r
which has a signature of (-1, +1, +1, +1) if you look at the sign of each term defining time and 3-d space. Hawking says that it is possible that a quantum fluctuation near the Planck Era could change the -1 in front of the time-like factor to +1 so that you get a signature for the metric of (+1, +1, +1, +1). In other words, time (-1) becomes another space-like variable (+1). You can also think of this as time becoming imaginary.

Guth's repulsive gravity produced an inflationary expansion state about 10^-34 seconds after the Big Bang which is long after the 10^-43 seconds when the Hawking event may have happened. They have nothing to do with each other physically.


Copyright 1997 Dr. Sten Odenwald
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