Inflationary Energy: Origins & Conversion

[windy miller]

As I understand it when inflation ends, it gives up the energy of the inflation field and converts into a "hot soup" of particles.
But where does the energy of the inflation field come from? Can it borrow it from the gravitational field ?

 

[Chalnoth]

Energy isn't conserved in an expanding universe. Here's one blog post that goes into some detail on this: http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/

 

[Chronos]

You get pair production at a furious pace at the end of inflation from the energy of the inflaton field. Where the inflaton energy originates is an unsolved mystery. A common hypothesis is it arises due to quantum fluctuations in the vacuum energy density of the infant universe - IOW it arises from nothing. A lot of people find that unsatifying because you need space and time as a backround for vacuum energy to exist. If spacetime itself was created by the BB, no space or time existed prior to the BB - turning the whole vacuum fluctuation thing into a chicken and egg paradox. Bear in mind there is no gravitational field without matter or energy. Welcome to the conflicting world where quantum physics meets theoretical cosmology.

 

[windy miller]

Isn't pressure a contributor to the gravitational field ?

 

[PeterDonis]

Isn't pressure a contributor to the gravitational field ?

Pressure appears in the stress-energy tensor, so it is part of the source of the gravitational field. But you can't have pressure without having matter or energy.

 

[Chalnoth]

Where the inflaton energy originates is an unsolved mystery.

I don't think this is an accurate statement. Where the inflaton energy originates isn't a mystery at all: it doesn't originate from anywhere as energy isn't conserved in an expanding universe. In particular, the properties of inflation make it so that a small amount of initial energy gives rise to a huge amount of energy at a similar density spread across a much larger region of space. There's no real mystery as to how this occurs: inflation has a nearly-constant energy density, which leads to a nearly-exponential expansion rate, which leads to a nearly-exponential increase in energy.

The mystery is where the inflaton itself came from: what is the inflaton particle, and how did it come to have a nearly-uniform density over a small region of space?

Also note that there are other alternative explanations for the early universe besides inflation, and those give rise to somewhat different questions about how our universe got its start. The answer to the energy issue remains the same in all of these models, however: energy isn't conserved in an expanding universe.

 

[Chronos]

I'm guessing the origins of energy in the universe is more a mystery than its subsequent conservation, or lack thereof.