What is ad hoc inflation?
Posted 30 June 2004 - 08:11 AM
Posted 01 July 2004 - 12:21 PM
Posted 01 July 2004 - 01:55 PM
Posted 01 July 2004 - 04:44 PM
In modern cosmology there are many problems, but one very fundamental is the inflation problem. This basicly says that the universe these days is accelerating and most probably also was accelarating (very fast!) just after the big bang. One of the ideas (and most promising) to solve this problem is to introduce a scalar field which is in general called the inflaton field (Note that a field in Quantum field theory is basicly a distribution of (virtual) particles). This field couples to the metric (the structure of space-time) and is subject to some potential V (the potential basicly says how the field behaves). The problem now is to think of a good potential that discribes the observations well. These potentials are sometimes called 'ad hoc' because They're just made up with the thought 'well maybe this works!'
Some remarks: - A similar scalar structure is The higgs field that gives particles their mass. -The mass of the inflaton is approxamitly 10^12 GeV (for comparison: the higgs particle has a mass of about 200 GeV, a factor tenbillion less. -In string theory scalar fields like this arise quite naturally. As you might know string theory needs 10 space-time dimensions to work, but we 'see' only 4. But we can roll up these extra dimensions,so that they are negligeble. However this roling up gives rise to scalar fields that quite naturally couple to the metric.
Some references: http://www.biols.sus...ibbin/cosmo.htm (haven't read it, but it's called inflation for beginners and it does mention the scalar fields) http://nedwww.ipac.c...le/Liddle5.html]http://nedwww.ipac.caltech.edu/level5/Liddle/Liddle5.html]http://nedwww.ipac.caltech.edu/level5/Liddle/Liddle5.html[/L][/L] gives a nice overview. More advanced, but the first pages are also understandable by undergraduate readers is: http://arxiv.org/abs/hep-th/0402051 Bo
Posted 02 July 2004 - 03:43 AM
Posted 02 July 2004 - 04:19 AM
Posted 02 July 2004 - 09:20 AM
Posted 02 July 2004 - 09:43 AM
Thanks Bo. That was what I was (very unsuccessfully) trying to say.
Originally posted by: Bo
These potentials are sometimes called 'ad hoc' because They're just made up with the thought 'well maybe this works!'
That rather than an "ad hoc Inflation" being a SPECIFIC KIND of "inflation", it is meant to suggest acceptance of concepts "for this" (the literal meaning of "ad hoc") particular theory of inflation as being currently discussed. Just like saying, "as a matter of convenience for this discussion we will accept...".