Slashdot Mirror
Inflaton, Mother of the Universe
quantalm writes "Forget the god particle, we're talking about the universe's particle mother. The theory of supersymmetry has rolled out two new ideas about the particle that puffed spacetime up from smaller than a proton to bigger than a soccer ball: it could be the 'unified particle' of Grand Unified Theories or a smaller-scale version that could be tested at the Large Hadron Collider at CERN."
i don't know about unifying electromagnetism and gravity, but it seems like someone just unified economics and quantum mechanics
just tell us how to avoid the deflaton particle for the next few years
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
The "inflation" we're talking about here is the accelerated expansion of the early universe. So, first off why do we need it?
It turns out that parts of the observable cosmic microwave background are 'causally disconnected'. This means that you take two patches of sky as observed at the time the CMB formed (300k years after the big bang, we now think - approximately 15 billion years ago) and track their behavior back to the big bang. In the normal models where the universe is full of dust or radiation they never were in contact in the past: Light from one area could never reach another. Why is this a problem? Because they are remarkably similar. They appear to have come into thermal equilibrium (same temperature) yet this shouldn't be possible if they were never in contact. So we need to have a method by which the universe expanded faster before this period.
There are a few ways to do this - one is a cosmological constant. But the problem with a constant is that it's constant - we should still see it today, and we don't. The universe is not expanding that fast anymore - the bounds we can place on the cosmological constant today put it well below the effect we want from inflation. What we need is something that acts like a cosmological constant for a while and then drops away. This is what inflationary models are all about. The inflaton is a theoretical particle that starts off behaving like the comsmological constant, but eventually decays into the matter we see today. We model this by a particle moving in a potential - think of a ball rolling on the side of a hill. How the inflaton behaves is all about the ratio of its kinetic to potential energy - high potential energy looks like a cosmological constant, high kinetic energy looks more like normal matter. (I can explain this in more detail if anyone's interested). So the ball rolls down the hill, losing potential, gaining kinetic (there's also friction from the expansion of the universe so it loses 'energy' overall) and hence our inflaton does exactly what we need - slowly changing from looking like a cosmological constant to normal matter. In theory too, it decays once it reaches the bottom of the hill, but no-one provides much of a model for this.
This is old (20-30 years old is old in theory standards) stuff from Linde, Mukhanov etc. No-one would take it seriously, except that when you calculate things from it, it works incredibly well - it's the source of http://xkcd.com/54/ - it's still controversial. Some people love it, others think it's a fudge and doesn't do much for you. The new stuff here is that there is a method being proposed by which a multiplet of supersymmetric particles (again, I can say a bit more but it's not my field) is shown to be able to act like the inflaton. Ie a stable state of multiple particles bound together could act this way, and could be found at the LHC. Now, that's a lot of 'could' - the usual inflaton mass is set to around 10^12 GeV - way above what the LHC can reach, and this is the same across most inflationary models. But if the LHC can see evidence of supersymmetry (again, another discussion, but it is thought to be likely that if supersymmetry is real then the LHC will see it) it might be able to at least give some credibility to some of these models of inflation.