poly: Bekenstein bound and expanding universe

From: Mitchell Porter <mitch@thehub.com.au>
Date: Mon Jan 19 1998 - 02:03:52 PST

The Bekenstein bound on the number of distinct states possible
for a quantum system is an increasing function of energy and radius,
as I recall. If energy or radius of the system increases, it
should go up. I don't have a reference to hand, but John Baez
says at http://www.math.ucr.edu/home/baez/week77.html that
"This bound says that the maximal entropy of a physical system is
proportional to its surface area", so I think I'm right.

Suppose you're a technological civilization in an open universe.
You expand into space, but eventually run into others doing the
same thing. You have control over a finite volume of space,
but can't go beyond its boundaries, and can't obtain new energy
from beyond them.

Nonetheless, since space is expanding (on a supragalactic scale,
at least), shouldn't the Bekenstein bound on your territory
also be increasing? Without limit?

In that case, perhaps one can build reversible computers with
boundlessly increasing state spaces in such a scenario.

Received on Mon Jan 19 10:21:23 1998

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