# What is brane inflation, and can it be eternal?

What is Brane Inflation and how does it describe inflation process? Can it be eternal?

Here is a a nice overview on the basics of brane inflation https://arxiv.org/abs/hep-th/0610221 (see also https://arxiv.org/abs/hep-th/0105203).

Brane inflation is, roughly speaking, a paradigm that propose an identification of brane/anti-brane annihilation processes with some types of cosmological inflation (typically hybrid ones).

Your question about the possibility of producing an eternal inflation scenario in the "brane inflation" paradigm cannot be answered unless you ask for a particular scenario within this paradigm.Despite of the later, I think is safe to say that in basic scenarios eternal inflation is not possible. The minimum of the potential for a tachyon field in a $$D3$$/ anti-$$D3$$-brane annihilation (in flat space) is reached at finite distances in moduli space, in other words, a stable vacuum for the pair is reached in finite time (see the review I attach).

• But in KKLT scenarios, eternal inflation occurs. Nov 5 '20 at 17:57
• That's not an established fact. In fact, many swampland criteria rule out the possibility of eternal inflation in the string theory landscape. See arxiv.org/abs/2008.07555 , arxiv.org/pdf/1905.05198.pdf, arxiv.org/abs/1909.11106. Although some loopholes on the latter arguments can be found, see arxiv.org/abs/1907.08943 and arxiv.org/abs/1807.11938. As I've said, it depends on what specific scenario you're asking for; in exactly the same way that happens in quantum field approaches to cosmological inflation. Nov 5 '20 at 23:21
• It is far from the fact that the swampland criteria is correct Nov 6 '20 at 6:15
• The point is that swampland criteria are much more well established than the KKLT and LV scenarios as full solutions of quantum gravity, see arxiv.org/pdf/1804.01120.pdf. Also recall that there is no single example of fully reliable eternal inflation within string theory, in contrast, all known (tens of billions) string theory compactifications obey most swampland criteria. Nov 6 '20 at 15:02
• To be fair, there is some pretty strong criticism of Swampland Criteria. The main argument is that the search for parameters is based on the "street lamp" principle. In addition, the cosmological constant is incompatible with the swamp and the quintessence models are poorly compatible. Nov 6 '20 at 16:34

In String Cosmology, Brane inflation is a mathematical realisation of the Cosmic Inflation in the very early universe within the brane world framework. It usually depends on how the brane inflationary universe originated, eternal inflation of the false vacuum type is too possible. Eternal inflation of the false vacuum type inevitably happens in this case due to the tunneling process.

• @Arman Armenpress, you can read the books on String Cosmology.
– user275163
Nov 5 '20 at 11:23
• What is Brane World? 5-dimensional spacetime with 4-dimensional branes embedded in it? Nov 5 '20 at 12:28
• No.............
– user275163
Nov 5 '20 at 13:01
• What then? Can you tell me in general terms? Nov 5 '20 at 14:27
• @SpinFoam Brane inflation is not restricted to brane-world scenarios, see arxiv.org/abs/hep-th/0601099 for an example within a KKLT-like scenario. Nov 5 '20 at 17:32