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."

Comments

inflaton?

[circletimessquare]

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

Re:inflaton?

[Monkeedude1212]

If those two particles meet, they don't cancel out - they actually cause a rift in the space-time continuum that is so catastrophic that it convinces people to take out sub-prime home equity loans.

Re:inflaton?

[istartedi]

So that's where the money went: Into subprime space.

Re:inflaton?

[SydShamino]

There might or might not be a $20 bill in my wallet; I won't know for certain until I look for it?

Re:inflaton?

[metamechanical]

Anyway just .02 cents.

OR PERHAPS $20! You won't know until you look.

Re:inflaton?

[Bigjeff5]

Yeah, but property in subprime space is cheeeeeep!

Re:inflaton?

[jimmydigital]

There might or might not be a $20 bill in my wallet; I won't know for certain until I look for it?

The likelihood of there NOT being a $20 bill in your wallet approaches infinity for the cube of the number of women in your life.

Or something

Re:inflaton?

[jd]

In subprime space, nobody can hear you default.

Re:inflaton?

[meringuoid]

There might or might not be a $20 bill in my wallet; I won't know for certain until I look for it?

No, cash behaves fairly classically. It's the rest of the economy that's quantum. For example, your house might or might not be worth $200,000. You won't know for certain until you try to sell it.

Re:inflaton?

[DreadPiratePizz]

"Anyway just .02 cents." Do you happen to work for Verizon?

Re:inflaton?

[Mr2001]

Deflation is bad for anyone who has any debt, which is an awful lot of people. The amount you owe is specified in nominal dollars, so deflation means you have to pay back a greater real value than you would otherwise.

It's also bad for anyone who runs a business, or works for a business, which again is an awful lot of people. Deflation -- or rather, the expectation of more deflation to come -- makes people less willing to spend money. I don't want to buy ten widgets for $10 today if I think I can get eleven for the same price tomorrow. So the widgets don't sell, the widget vendor gets desperate and drops his prices, and now he has to cut wages or lay off employees, and the cycle continues.

Re:inflaton?

[Tetsujin]

There might or might not be a $20 bill in my wallet; I won't know for certain until I look for it?

No $20 bill... But my cat just died.

Thanks, a lot, jerk.

Re:I love scientists.

[boowax]

I'm Sparticles!

unfortunately i do

[circletimessquare]

it was those quant assholes who got us into this mess

they used formulas extrapolating from cherry picked models to suggest that the economic universe could just go on inflating forever. big bang indeed

http://online.wsj.com/article/NA_WSJ_PUB:SB10001424052748704509704575019032416477138.html

This just in from LHC....

[MaggieL]

"Oops. Sorry about those extra universes that just leaked out."

Re:Prior to the expansion

[alexborges]

What is this time you speak of at those moments?

Oh wait...

Freudian slip

[Xacid]

My initial reading of the subject:

Inflation of Mother, like a Universe.

Re:Freudian slip

[ruiner13]

Your mom is so inflated, your dad had to roll her in flour and find the wet spot.

Re:Freudian slip

[Quiet_Desperation]

Your mom is so inflated, your dad had to roll her in flour and find the wet spot.

Nah, you need to go full on physics here.

"You mom is so inflated, your dad had to roll her up like a Calabi-Yau manifold and look for the Casimir effect!"

Thank you! Am I right? Huh? Huh? Am I? Huh?

Oh, shut up.

Re:Freudian slip

[Xacid]

"Only a topologist could find her parts attractive".

Re:Freudian slip

[Bigjeff5]

Yeah, accept...

Oh shit!

*runs from the grammar nazis*

you've just described the quantum mechanics behind

[circletimessquare]

the creation of the moron particle

Inflationary theory

[Kepesk]

I'm not saying that the inflationary phase of the universe is a false concept, but I've always thought that the way the theory came about is a bit sketchy.

Please correct me if I'm mistaken with any of this, but this is my understanding of its history. Earlier versions of the Big Bang theory did not include this rapid inflation in the earlier universe; the universe was said to expand at a more constant rate. However, when the Cosmic Microwave Background Radiation was first observed, there was no way to explain its irregularity based on that model. So physicists decided to plunk down a mysterious inflationary phase into their models of the early universe, a concept with no known cause or explanation, but which made the CMBR fit with the Big Bang theory. However, it's a concept that to this day they're still trying to reconcile with the rest of observed physics, as this article shows.

Could the theory be true? Sure. But if it is, it's because those physicists got lucky with their educated guess on the matter. Other theories with much more solid backing have in the past been roundly disproven.

Re:Inflationary theory

[Remus Shepherd]

I hear what you're saying. But the problem is, if the inflationary theory is false then we need some other mechanism to explain the cosmic background. Inflation solves the problem without breaking the speed of light or special relativity -- both of which are kind of important to keep around.

Inflation *could*, ultimately, be proven false. But if that happens it will topple a lot of important theories along with it. So you can understand why most physicists are assuming it's the correct model, and trying to figure out exactly how it happened.

Re:Inflationary theory

[Bigjeff5]

However, when the Cosmic Microwave Background Radiation was first observed, there was no way to explain its irregularity based on that model.

Actually you have that backwards, without inflation, the CMBR should be extremely irregular. There should be huge blotches of stuff all over. Think of a balloon filled with paint splattering on the floor - it doesn't create a fine coating all over the floor, it creates huge splatters here and there with huge gaps of nothing in between.

The CMBR, however, is extremely uniform. When you look at a picture of the CMBR, the variations in color are artificial (similar to the way the color nebulae from infra-red data) and represent extremely minute changes in radiation (you'll note there are no areas with no radiation, but there should be). The CMBR effectively shows a nice, even "coating" of radiation that covers the universe from one end to the other. This is disturbing, and cannot be explained by any physics we know of.

The only way to explain this is if the big bang wasn't an explosion (huge release, starts fast but decelerates quickly), but actually a controlled inflation - it had to start slow, accelerate, and then decelerate in order to produce the nice, even radiation we see. They had to accelerate the time-line of the Big Bang for a microsecond and then decelerate it immediately after in order to reproduce the uniformity seen in the CMBR. It's completely arbitrary, and has absolutely no grounding in physics, yet it's the only way to fit the physics we do know with the observations we see.

If you think you are disturbed by this, talk to a cosmologist or a physicist sometime. They absolutely hate having to change a model to fit observations without having any idea what is missing in their model to cause that change. It's like Dark Energy and Dark Matter, or the singularity of a Black Hole - cosmologists hate all of them. They use them, because it works, but they hate them all the same. They screw with their nice, neat physics.

Same thing with inflation - there is no known physical property that should cause inflation, yet inflation is the only way to explain the universe as it is now. It means there is something fundamental to the universe that we don't know or understand.

PS: Fun fact: if you tune an analog TV to an unused channel, something like 10% of the fuzz you see is caused by the CMBR.

Re:Inflationary theory

[bjorniac]

There are certainly alternatives to inflation that people do find attractive - ekpyrotic, cyclic or simply oscillatory universes for example can easily bring points into causal contact by extending the past of these points beyond where there would be a classical big bang. Various string models, and Loop Quantum Cosmology have methods for this (LQC has a really neat well understood bounce) and the idea goes back to Lemaitre's 'Phoenix Universe' ideas. However, inflation does more than just explain existing phenomena - it predicted a spectral index between 0.98 and 0.92, and COBE/WMAP bring it in at around 0.96. It also does a really good job of explaining structure formation. Now, that isn't to say that it's necessarily right, and that other theories couldn't do a similar thing, but inflation really does a good job. It's certainly far from perfect, numerous people have objections to it, but so far it fits the data we have.

Re:Inflationary theory

[PvtVoid]

However, inflation does more than just explain existing phenomena - it predicted a spectral index between 0.98 and 0.92, and COBE/WMAP bring it in at around 0.96.

Where on Earth did you ever get that idea? Inflation makes no such prediction. For example, Linde's "Hybrid" inflation model predicts a spectral index greater than 1.0, and is pretty much ruled out by WMAP. Similarly, so-called "Natural" inflation models can easily accomodate a spectral index as low as 0.7 or so. See for example this paper for a nice general review, and this paper specifically for the Natural Inflation case. Inflation does robustly predict adiabatic, superhorizon perturbations, and this is borne out by the data. This is powerful enough evidence without having to overstate the predictivity of the theory.

Re:Inflationary theory

[jd]

Not quite. The Inflationary phase was anything but controlled. The current model predicts that between the initial Big Bang and the start of the inflationary phase (roughly one planck time), the universe expanded at some unknown rate. We can't observe the pre-inflationary phase, so there is no useful model for it. When the conditions for inflation were met, the Universe suddenly expanded at a truly fantastic rate (effectively faster than light). This inflationary phase not only generated an enormous amount of space very quickly, but also generated an enormous amount of matter very quickly. This is a consequence of quantum foam having a zero sum over a non-zero amount of space and non-zero amount of time but a non-zero sum at any given instant in space and time. (Hawking Radiation, likewise, results in something from an average of nothing for the same reason.)

The inflationary phase is extremely hard to model because, as Professor Hawking has noted, not only does space vary non-linearly in the universe, so does time. At whatever point the density of the universe was greatest, the rate of time was slowest. In some models of the very early universe, time follows a parabolic path. As you approach T=0, the rate of change of time also approaches zero. If this is correct, then there was no moment of Big Bang (and therefore no singularity) because there wasn't any point in time for it to occur. (Since Black Hole theory stems from Big Bang theory, and since the argument over time revolves around the density of matter bending time as well as space, this raises questions about whether models of Black Holes can be correct. A singularity cannot accumulate mass if delta-T is zero, for there is no point in time for the accumulation to occur in. However, that is another debate.)

Because mass bends time as well as space, we cannot accurately model the effects of inflation on the universe without knowing how mass changed due to the properties of quantum foam, because we cannot know the effect on time otherwise. All we know is that mass/energy was not a constant during this phase and that at no point in this phase did it equal the mass/energy of the universe today. We think the latter part of inflation will have tended to this value, but frankly there is no evidence for that. The universe dropped out of the inflationary phase, and it is assumed that the transition was relatively non-turbulent - or can at least be modeled as such - but most transitions we do know of are extremely turbulent and disruptive.

Some of this can be solved experimentally. You need an extremely high energy density - about the same as the output of a hydrogen bomb packed into a cubic centimeter is how I've heard it described - but it's not an unachievable amount of energy (obviously) even if we're not sure quite how to get the density that high. It's perfectly safe, too. Well, so long as theory is correct, at least. It would form a universe attached to this one through a mini black hole. Essentially you'd form a blister on this universe, where the blister contained another universe. The black hole is a good thing - prevents this universe getting fried from the inflationary phase of the new one - but since the black hole exists in some form in both universes, its state must reveal something about that other universe.

Re:Inflationary theory

[bjorniac]

I should be clear: My experience is with scalar field inflation with a quadratic potential - the simplest models that are most common. Hybrid inflation can do almost anything, it's true.

My references for that statement:

Tegmark: http://arxiv.org/abs/astro-ph/0410281
Steinhardt: http://arxiv.org/abs/astro-ph/0507455

I believe Mukhanov and Turok both talk about it too, though I can't find the references easily at the moment.

Re:Inflationary theory

[budgenator]

The universe was always as big as the whole universe, so how can it expand? How do we know we're not shrinking inside a fixed size universe?

Re:Inflationary theory

[Anonymous Coward]

Inflation didn't begin one planck time after the big bang. So far as we can tell, it was more like 10^6 planck times. (See Mukhanov http://arxiv.org/abs/hep-th/0503203 or Rindler's book on cosmology). There certainly are useful models for this phase too - various string theories, ekpyrosis, loop gravity are amongst the candidates. Also your statement about 'quantum foam' is gobbledygook - a 'non-zero sum' of what? Energy? Mass? Perhaps you're trying to say that there is matter associated with empty space, a la cosmological constants etc?

I'm afraid I'm also going to have to jump on statements like "As you approach T=0, the rate of change of time also approaches zero."

Rate of change of time with respect to what exactly? dt/dt =1 by definition, so what is time changing with respect to? Hawking most certainly does NOT support the idea that there was no big bang or no time for it to take place - in fact the Hawking-Penrose singularity theorems rather prove that GR predicts that not only was there a big bang, but it happened a finite amount of proper time ago. "Likewise time follows a parabolic path" - parabolic with respect to what other parameter? The whole point of GR is that we can change coordinates and reparametrize as necessary (see rindler coordinates for black holes, for example, or proper-time descriptions of cosmology). Therefore the singularity can certainly be placed at a finite point on (the boundary of a) space-time manifold.

Hydrogen bomb per cubic centimeter doesn't even come close to the energy scale you're looking at - it's more akin to all the matter in our galaxy being packed within the size of an atom. I'm afraid your post is mostly wrong - where are you getting your material from?

Re:Inflationary theory

[bjorniac]

That's an interesting question to which an answer can take a few forms. One is that below describing the balloon. This would be a closed universe model (finite size, wraps around itself) such as a torus or sphere. However, suppose the universe is truly infinite - what does it mean to be expanding?

Well, suppose one can put a mark on two points in space, and watch them over time. To be expanding these two points will move apart, as will any two points in space. To do it a little more mathematically: Suppose I have a line - the real numbers - that goes on forever. And I pick two points on the line (arbitrarily again suppose we get -0.45 and 3.09 for purpose of example). Then I double the coordinate of each point (now at -0.9 and 6.18). This way the line is still infinite - it's as long as the real line - but it has 'expanded' as every point before is now further away than previous points.

In cosmology we do this in a very similar way - using what we call a 'fiducial cell'; a blob of space. We assume the universe is (to first order) homogeneous (same everywhere) and isotropic (same in every direction). Thus if we see the blob expand we're seeing the whole universe expand. Mathematically, we form a 'metric' a way of measuring space and time, the simplest homogeneous and isotropic version of which is:

ds^2 = -dt^2 +a(t)^2(dx^2+dy^2+dz^2)

You might recognize the last bit as being like pythagoras' theorem in 3D. (There are two other homogeneous isotropic examples, but I'm choosing the simplest one to make life easy). a(t) can only be a function of time, as if it were a function of space, this would break homogeneity. Likewise it must multiply all directions equally to retain isotropy. (Again for the pros I'm being fast and loose here to make life easier). Thus our universe can be infinite (x,y,z go on forever) but distances can change over time as a(t) changes. That way we truly can see expansion or contraction in the universe. This was what Friedmann first put forward as a solution to Einstein's equations, and Robertson+Walker later showed that it's true in general cases for homogeneity and isotropy. Finally Lemaitre worked out what this really meant physically.

Now a(t) has no meaning by itself - I could just have chosen a smaller piece of space on which to start measuring. But the rate of change 1/a * da/dt is very meaningful - the relative change rate known as the Hubble parameter. It is from measurements of the doppler effect on light (called redshift/blueshift for stars moving away from/towards us) that we can get a handle on this and see that a(t) is indeed increasing - the universe is expanding. The point of inflation is to understand a model in which a(t) was not only increasing, but accelerating, but that's a much longer discussion.

Hope that helps!

Re:Inflationary theory

[h4rm0ny]

I should be clear: My experience is with scalar field inflation with a quadratic potential

The world needs a lot more people who say things like this. :D

Re:Has anything to come out of string theory ...

[sgt101]

I think that there are some really interesting predictions of how gravity should behave on a submicron scale which could rule out (or in) large number of potential string theories.

Of course, while I can imagine that gravity could be tested on a submicron scale when I start to try and imagine what kind of experiment could be constructed that actually did that I start to flail about and gape and make little clucking noises. I expect there are a fair number of physics fellas doing the same.

Brief(!) Explanation of Inflation

[bjorniac]

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.

Re:Brief(!) Explanation of Inflation

[Ambitwistor]

No-one would take [inflation] seriously, except that when you calculate things from it, it works incredibly well - it's the source of http://xkcd.com/54/

Not quite. You don't need inflation to get the blackbody spectrum of the cosmic microwave background radiation (CMBR) observed by the COBE satellite, which is what the xkcd comic depcits. That's a prediction of plain vanilla Big Bang cosmology, with or without an early inflationary phase.

However, inflation does predict details in the CMBR angular power spectrum, the "acoustic peaks", which were observed by the later WMAP satellite. And it solves other "paradoxes", like the horizon problem you mention.

Re:Brief(!) Explanation of Inflation

[bjorniac]

"black hole hits critical mass"

What mass is this? How do you fix the scale?

"black hole explodes"

By what mechanism? How does a trapped surface become untrapped? Where does the mass go if the region is still dense enough to cause a trapped horizon, how can it 'explode'? ...

"stars coalesce along with planets from gas and matter in the expanding galaxy"

Actually planets come from exploded stars.

"Gravity, though seemingly weak, eventually slows the galaxy down enough to where it begins contracting again."

It's more than that - it's the entire universe. Except, that's only if the universe is above a critical density, i.e. we're in a closed universe. Which we don't know. In fact, for some reason the rate of expansion appears to be accelerating.

Anyone can have a crazy guess about how the universe works. The science part is formulating this in a rigorous manner, fitting it with existing knowledge and making testable predictions.

Re:Brief(!) Explanation of Inflation

[bjorniac]

Ah, now you're into the fun stuff: Just about every physicist believes that general relativity will have to be modified by quantum mechanics at some stage and at least once you get to energy densities around the planck density (this value comes mostly from dimensional analysis - it's more of an order of magnitude thing). Since the standard big bang that results from GR has infinite density, we believe that corrections will happen before you get there - that quantum mechanical effects take place and that we can't trust GR when we get above the planck density. Therefore, since we don't have a proven quantum theory of gravity (there are some interesting, even heroic attempts but nothing anywhere near tested) we simply have to say that somewhere in the past, probably around the planck density, we don't have any good prediction for what's going on. So we can't just say that everything started in the same place (which was everywhere too - the joys of relativity :) ), as GR predicts.

Another outlook on this is that we know quantum mechanics will be seriously affecting matter at this stage too - the temporal heisenberg principle is between energy and time and hence there should be a large difference in energies (and hence temperatures) between nearby points, yet somehow they come out of this highly quantum mechanical phase into a classical phase in which they should be out of causal contact and yet somehow thermalize.

Re:Has anything to come out of string theory ...

[maxwell demon]

... actually been proven?

Yes: We have conclusive proof that string theory leads to publications. :-)