Gravity is a limitless supply of energy to inflaton field

[AlephClo]

In the Fabric of the cosmos, B Greene indicates that 'as the universe expands, matter and radiation lose energy to gravity while inflaton field gains energy from gravity' (page 312). I can accept that statement, but in his note no. 2 (page 524), he indicates that 'the special feature about gravitational field, is that it can become arbitrarily negative, and is essentially a limitless supply of energy'. How can gravity be limitless supply of energy is my question?

Any explanations or references would make me happy. Thank you :-)

 

[Dale]

I would start here:
http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

Essentially, one of the bad (IMO) features of GR is that energy is not globally conserved in some spacetimes.

 

[AlephClo]

Thank you

 

[PeterDonis]

one of the bad (IMO) features of GR is that energy is not globally conserved in some spacetimes.

"Bad" in the sense of "inconvenient", yes; but it's an inconvenient feature of reality, not GR. Don't shoot the messenger.

 

[Dale]

"Bad" in the sense of "inconvenient", yes; but it's an inconvenient feature of reality, not GR. Don't shoot the messenger.

Yes, thanks for the clarification.

 

[AlephClo]

Your comments are much appreciated, thank you both