- #1
- 335
- 8
The expansion of the inflationary universe is said to be roughly exponential. Why is it called "roughly" exponential?
The expansion of the inflationary universe is said to be roughly exponential.
It's mentioned in most cosmology texts, e.g. Cosmology by Steven Weinberg, in Inflation chapter.
It's more that only in a universe with nothing in it but vacuum energy will the expansion be exactly exponential. It's not quite exponential because there's other matter around.I would say the "more or less exponentially" is a consequence of the "slowly varying vacuum energy". As I understand it, only a vacuum energy that is exactly constant will lead to an expansion that is exactly exponential.
It's not quite exponential because there's other matter around.
Argh, sorry, you're right. I was thinking of the current near-exponential expansion. Never mind.Is there, though? As I understand the basic inflation model, the Standard Model fields are all in their vacuum states during inflation, and all of these fields have zero vacuum expectation value for energy; they only get reheated to highly non-vacuum, high temperature states at the end of inflation.