What Does the Expansion and Inflation of the Universe Mean for Quantum Physics?

[Cajun]

I doing research on the state of the universe before and after Inflation for a science fiction book I am writing.

In the Plank Epoch (0 to 10-43 seconds), Gravity separates. At the end of the Grand Unification Epoch (10-36 seconds), the universe is expanding enough for the universe to cool down and the Strong Force separates. This triggers inflation which lasts from 10-36 to 10-32 seconds.

After Inflation, does the universe go back to its original speed of expansion? What is the cause of the universe expanding to the point of separating the Strong Force? If its not "Expanding" in the begining, what do they mean by "As the universe expands and cools from the Planck epoch, gravitation begins to separate from the fundamental gauge interactions"?

After Inflation and everything has settled down (relatively speaking compared to the Big Bang) what was the speed of expansion throughout the age of the universe? Was it a constant speed? How much and when did it change? At what point did Dark Energy start to take over?

Im writing a book with paradoxes that ends with our actions (and actions from an outside source...) causing the expansion and inflation to happen exactly in reverse. So the more details about the state, size, speed of the universe the better. Great reading material on this website, but don't even try to make sense out of wikipedia, even though i keep going back. Thank you.

 

[bapowell]

In the Plank Epoch (0 to 10-43 seconds), Gravity separates. At the end of the Grand Unification Epoch (10-36 seconds), the universe is expanding enough for the universe to cool down and the Strong Force separates. This triggers inflation which lasts from 10-36 to 10-32 seconds.

This could be true, but it is currently speculative. First, it is an open question as to whether gravity should be included in a fully unified theory. Second, inflation may have had nothing to do with the breaking of the Grand Unification symmetry, although early efforts certainly looked towards this mechanism as providing an eligible candidate for the inflaton. These efforts soon met with difficulty and it appears particularly unlikely that inflation is related to these phase transitions.

After Inflation, does the universe go back to its original speed of expansion?

The expansion rate of the universe (not a speed) depends on the kind of energy/matter in it. After inflation ends, the universe "reheats" into a radiation-dominated phase. The scale factor, a(t), (the quantity that tracks how length scales grow with the expansion) has the following time dependence during radiation-domination: $a(t) \sim t^{1/2}$. For comparison, during the early stages of inflation a(t) is close to $a(t) \sim e^t$.

What is the cause of the universe expanding to the point of separating the Strong Force? If its not "Expanding" in the begining, what do they mean by "As the universe expands and cools from the Planck epoch, gravitation begins to separate from the fundamental gauge interactions"?

The breaking of symmetries (the separation of forces) depends on the temperature, T, of the universe, which in turn depends on the amount of expansion: T ~ 1/a. If gravity was indeed unified with the other gauge forces, then it would have separated off early once the universe dropped approximately below the Planck temperature. Nothing causes the universe to expand -- this is actually an initial condition set by the big bang. It's important to realize that the standard big bang model does not address the initial bang itself -- the initial singularity. It is instead a model for describing how the early universe evolved from an early, hot, dense phase into an older, cooler, less dense phase.

After Inflation and everything has settled down (relatively speaking compared to the Big Bang) what was the speed of expansion throughout the age of the universe? Was it a constant speed? How much and when did it change? At what point did Dark Energy start to take over?

After inflation the universe passed through a radiation dominated phase, then cooled and passed through a matter-dominated phase, during which its rate of deceleration increased. About 5 billion years ago, dark energy began to dominate the expansion. Under dark energy domination, the expansion rate is very nearly constant.

 

[Tanelorn]

bapowell said "After inflation the universe passed through a radiation dominated phase, then cooled and passed through a matter-dominated phase, during which its rate of deceleration increased. About 5 billion years ago, dark energy began to dominate the expansion. Under dark energy domination, the expansion rate is very nearly constant."

When put in these terms this further suggests to me an intended plan or design for the overall structure of the universe. It just doesn't feel as random as things could be anymore..
And if so, is the structure of the universe that we see today the end game and relatively stable, or is it yet to come, in another 10B or 100B years or so?

 

[edgepflow]

And if so, is the structure of the universe that we see today the end game and relatively stable, or is it yet to come, in another 10B or 100B years or so?

This is an interesting question. If the cosmological constant stays constant, I think the scale factor [ a(100B) / a(now) ] will increase by about a factor of about 200 in the next 100B years. The acceleration will reach a constant value and I believe the decelereration value qo will approach -1.

This assumes the cosmological constant is at a local minimum. If it is not, these values will change.

 

[Tanelorn]

Thanks edgepflow. could you please define scale factor, a and qo.


Assuming that a is the acceleration then you saying that the rate of expansion increases by 200 in 100B years? but why do you then say that the acceleration value reaches a constant value?

When viewed on these timescales any semblence to stablity or a stable structure above the size of our local group of galaxies is merely an illusion! However, perhaps this is what is required to maintain the relatively stable structure of these galaxies? Perhaps that is the end game lots of small universes the size of our local group of galaxies..

 

[edgepflow]

Thanks edgepflow. could you please define scale factor, a and qo.


Assuming that a is the acceleration then you saying that the rate of expansion increases by 200 in 100B years? but why do you then say that the acceleration value reaches a constant value?

When viewed on these timescales any semblence to stablity or a stable structure above the size of our local group of galaxies is merely an illusion! However, perhaps this is what is required to maintain the relatively stable structure of these galaxies? Perhaps that is the end game lots of small universes the size of our local group of galaxies..

Sure, let's try some back-of-envelope numbers to illustrate.

First, the definition of scale factor a(t). Think of this as stretching (x,y) coordinates on a piece of grid paper. The scale factor shows how the universe is growing (or shrinking) with time. For example, if between any two times t1 and t2, the scale factor doubles (a2/a1 =2), then the universe has grown in size by a factor of two. Two galaxies (out of each others gravitational influence) will now be twice as far apart. For convenience, take the scale factor for the present to be one:
a(t) = ao = a(now) = 1.

In a cosmology dominated by dark energy, the growth of the scale factor is exponential. This can be expressed as:

a(t) = ao exp [ (t-to) sqrt (gamma/3) ]

where,

ao = 1
t = time of interest = 100B years
to = current age of universe ~ 13.2 X 10^9 years
gamma = cosmological constant ~ 10^-35 1/sec^2

So if we plug in we find: a(100B years) / ao = 149.

Close to the value of 200 I mentioned earlier (the vlaue of 200 accounted for the fact that the universe in not quite yet dominated by dark energy but this complexity was ommited to make a point).

So in 100B years from now, the universe has swelled to 149 times its current size.

The deceleration parameter qo is a little more subtle. But an accelerating (growing) universe has q(t) < 0. In fact:

q(t) = Omega Matter (t) / 2 - Omega Dark Energy (t)

And Omega Matter (t) + Omega Dark Energy (t) = 1 for a flat universe. After 100B years,


Omega Matter (100B) = 0 and Omega Dark Energy (100B) = 1

so q(100B) = -1

 

[bapowell]

When put in these terms this further suggests to me an intended plan or design for the overall structure of the universe. It just doesn't feel as random as things could be anymore..

Not sure why you are proposing this dichotomy. Something can be undesigned and non-random.

 

[Tanelorn]

Thanks edgepflow, I will study this in the morning.

bapowell, I agree, but to me its starting to look like a coin was tossed and instead of landing either heads or tails, it landed on its edge.
Sure its theoretically possible, but if we just happen to find the coin stood on its edge we wouldn't try to explain it by saying that it got there through tossing.
And in this case, with the universe that we have observed, maybe we have found several coins that seems to have aligned themselves just right on their edges.
I am not suggesting intelligent control but perhaps there are one or more negative feedback processes at work in the universe?

 

[Cajun]

This could be true, but it is currently speculative. First, it is an open question as to whether gravity should be included in a fully unified theory. Second, inflation may have had nothing to do with the breaking of the Grand Unification symmetry, although early efforts certainly looked towards this mechanism as providing an eligible candidate for the inflaton. These efforts soon met with difficulty and it appears particularly unlikely that inflation is related to these phase transitions.

So depending on whether gravity is a force carrier or the bending of spacetime determines if it can be part of the Grand Unification symmetry? I believe gravity is an emergent force of the fundamental laws of our universe, to me Entropic Gravity makes most sense. Spacetime bending and following a geodesic sounds very interesting but overly complex. So current understanding is that gravity and inflation was separate from symmetry breaking?

The expansion rate of the universe (not a speed) depends on the kind of energy/matter in it. After inflation ends, the universe "reheats" into a radiation-dominated phase. The scale factor, a(t), (the quantity that tracks how length scales grow with the expansion) has the following time dependence during radiation-domination: $a(t) \sim t^{1/2}$. For comparison, during the early stages of inflation a(t) is close to $a(t) \sim e^t$.

The breaking of symmetries (the separation of forces) depends on the temperature, T, of the universe, which in turn depends on the amount of expansion: T ~ 1/a. If gravity was indeed unified with the other gauge forces, then it would have separated off early once the universe dropped approximately below the Planck temperature. Nothing causes the universe to expand -- this is actually an initial condition set by the big bang. It's important to realize that the standard big bang model does not address the initial bang itself -- the initial singularity. It is instead a model for describing how the early universe evolved from an early, hot, dense phase into an older, cooler, less dense phase.

Yes i meant the expansion "rate" not speed. Do we know what caused these initial conditions that caused the initial expansion? Did symmetry breaking "start" the whole process? Is it possible to know?

After inflation the universe passed through a radiation dominated phase, then cooled and passed through a matter-dominated phase, during which its rate of deceleration increased. About 5 billion years ago, dark energy began to dominate the expansion. Under dark energy domination, the expansion rate is very nearly constant.

So the universe is "created" and it starts to expand and cool down which leads to the separation of the forces. Somewhere down the line Inflation is triggered which almost immediately expands the universe. After Inflation ends, the expansion returns to its previous rate (if not, slower or faster than before Inflation?). After radiation dominated phase, the Quark Epoch begins at 10-12 seconds, at this point the universes rate of expansion gets decreased (proportionate to the amount of matter getting created?). So the deceleration continues (continues?) til the dark energy begins to dominate, at which point the expansions starts accelerating, and will continue.

I want to try to keep my book as close to science fact as possible, while leaving room to fill in what we don't know with philosophical logic. So far so good, but my book begins with the big bang (and i know it wasnt a "Bang" that's why I am researching all the misconceptions and areas that are speculative ). Thank you for your help.

 

[Cajun]

When put in these terms this further suggests to me an intended plan or design for the overall structure of the universe. It just doesn't feel as random as things could be anymore..

This is one Major question i want to address with my book. Is there a creator? Why? Why life? Why this universe? Whats the meaning of it ALL? The answer i came to was everything is a paradox based on fractal logic. Deeper than that but that's why I am writing a book. Its about time religion and philosophy meet science .

 

[twofish-quant]

bapowell, I agree, but to me its starting to look like a coin was tossed and instead of landing either heads or tails, it landed on its edge.
Sure its theoretically possible, but if we just happen to find the coin stood on its edge we wouldn't try to explain it by saying that it got there through tossing.

You can go anthropic. There are a bizzillion universes in which the coin ended up heads or tails. It just so happens is that if you had the coin end up that way no one would see it, so for everything to work, you have to have some weird cosmic coincidence.

One other way of thinking about it is that when I walked out this morning, I miraculously encountered an atmosphere which I could breathe. It so happens that there are a huge number of planets with atmospheres that I can't breathe, but I'd be dead if I was on one of them.

I am not suggesting intelligent control but perhaps there are one or more negative feedback processes at work in the universe?

See above. It's not surprising to see the universe just work out so that life can exist, because if it were otherwise, we wouldn't be having this conversation.

 

[bapowell]

bapowell, I agree, but to me its starting to look like a coin was tossed and instead of landing either heads or tails, it landed on its edge.
Sure its theoretically possible, but if we just happen to find the coin stood on its edge we wouldn't try to explain it by saying that it got there through tossing.
And in this case, with the universe that we have observed, maybe we have found several coins that seems to have aligned themselves just right on their edges.
I am not suggesting intelligent control but perhaps there are one or more negative feedback processes at work in the universe?

To add to twofish-quant's reply, I think it's important to point out that this all presumes that we understand life sufficiently to identify the necessary conditions for its flourishing, and that we've then identified that the conditions of the universe have been sufficiently tuned to accommodate them. I would argue that we do not know the answer to either of these important questions -- we are just now beginning to understand the intricate workings of life and its origins here on earth. It's very likely that our view of the prerequisites for life's biochemistry is severely narrow.

 

[bapowell]

So depending on whether gravity is a force carrier or the bending of spacetime determines if it can be part of the Grand Unification symmetry? I believe gravity is an emergent force of the fundamental laws of our universe, to me Entropic Gravity makes most sense. Spacetime bending and following a geodesic sounds very interesting but overly complex. So current understanding is that gravity and inflation was separate from symmetry breaking?

That's essentially the reason. But what about particles following geodesics in a curved spacetime seems complex to you? It is a necessary consequence of the Equivalence Principle, which is beautifully simple. And don't forget that geodesics are the straightest possible paths on these surfaces.

Yes i meant the expansion "rate" not speed. Do we know what caused these initial conditions that caused the initial expansion? Did symmetry breaking "start" the whole process? Is it possible to know?

We don't currently understand the nature of the big bang itself. We have a much better chance of understanding what got inflation started, and symmetry breaking may have had something to do with this (I'd really like to think so, at least), but as I said in a previous post, this has been difficult to implement.

So the universe is "created" and it starts to expand and cool down which leads to the separation of the forces. Somewhere down the line Inflation is triggered which almost immediately expands the universe. After Inflation ends, the expansion returns to its previous rate (if not, slower or faster than before Inflation?).

We currently have no observational data on the evolution of the universe prior to inflation -- inflation is incredibly good at providing a clean slate for post-inflationary evolution. So, we can only speculate. If inflation is 'eternal', then our observable universe simply 'percolated' out of a larger inflating region, with no big bang to speak of. However, if you wish to consider inflation as arising from some field configuration in a post big bang universe (like from symmetry breaking, e.g.), then you would probably have radiation dominated-expansion before inflation kicked off, since this is consistent with a hot big bang. There is nothing physically wrong with this conjecture.

After radiation dominated phase, the Quark Epoch begins at 10-12 seconds, at this point the universes rate of expansion gets decreased (proportionate to the amount of matter getting created?).

The expansion rate of the universe depends on the type of matter/energy in the universe and its density. Matter isn't being created as the universe evolves -- everything we see around us was generated in the beginning.

I want to try to keep my book as close to science fact as possible, while leaving room to fill in what we don't know with philosophical logic. So far so good, but my book begins with the big bang (and i know it wasnt a "Bang" that's why I am researching all the misconceptions and areas that are speculative ). Thank you for your help.

No problem. Sounds exciting.

 

[Tanelorn]

Thanks Edgepflow, I am now awake and able to study this.

"So in 100B years from now, the universe has swelled to 149 times its current size."

I followed the argument well up until this point. I understand that gravitationally bound structures up to a certain size will hold themselves together. Would it be correct to say that without dark energy expansion so many galaxies would merge becoming destructively active and putting today's relatively ordered structure of galaxies at risk.


I don't know how to interpret the deceleration factor. To me q(100B) = -1 just appears to mean that the universe is expanding at a constant rate of acceleration forever?
Since it is space that is expanding is it distance that expands at a constant rate or volume? If distance doubles then the volume increases 8 fold, which seems quite alot!

 

[twofish-quant]

I would argue that we do not know the answer to either of these important questions -- we are just now beginning to understand the intricate workings of life and its origins here on earth. It's very likely that our view of the prerequisites for life's biochemistry is severely narrow.

Yup. One problem with going anthropic is that it's not clear how you'd go about showing that life can't exist in an alternative universe.

 

[twofish-quant]

So current understanding is that gravity and inflation was separate from symmetry breaking?

The current understanding is that you solve a lot of riddles if you assume inflation. So instead of having a dozen things that you can't explain, you wave the magic wand, and you have one thing that you can't explain.

That's scientific progress.

Do we know what caused these initial conditions that caused the initial expansion? Did symmetry breaking "start" the whole process?

No real clue. People tried a whole bunch of models that assumed that inflation came from SSB, and all of them had problems.

Is it possible to know?

You assume that it is. If you start out with the assumption that knowledge is impossible, then you won't spend the effort tackling the problem.

Also, you can get a lot of progress by figuring out what doesn't work.

After Inflation ends, the expansion returns to its previous rate (if not, slower or faster than before Inflation?). After radiation dominated phase, the Quark Epoch begins at 10-12 seconds, at this point the universes rate of expansion gets decreased (proportionate to the amount of matter getting created?). So the deceleration continues (continues?) til the dark energy begins to dominate, at which point the expansions starts accelerating, and will continue.

My wild somewhat crackpot idea is that the thing that caused inflation is what is causing dark energy. If we can figure out what dark energy is, this could give some ideas on what inflation was. Or not.

I want to try to keep my book as close to science fact as possible, while leaving room to fill in what we don't know with philosophical logic.

One problem that you'll run into is that facts change. There is most likely something that is accepted conventional wisdom that will turn out to be wildly wrong.

 

[bapowell]

My wild somewhat crackpot idea is that the thing that caused inflation is what is causing dark energy. If we can figure out what dark energy is, this could give some ideas on what inflation was. Or not.

Not too wild -- Jim Peebles and Alex Vilenkin considered this as well:

http://arxiv.org/abs/astro-ph/9810509

 

[Tanelorn]

And mine!

 

[Cajun]

That's essentially the reason. But what about particles following geodesics in a curved spacetime seems complex to you? It is a necessary consequence of the Equivalence Principle, which is beautifully simple. And don't forget that geodesics are the straightest possible paths on these surfaces.

I understand the analogy with the Earth sitting on a rubber sheet, even though i don't like it. Sounds like using a explosion to explain the big bang, which is wrong but a good start. But i can't find anything deeper than it just "sits" and "curves" space. The way i think they are saying it is the rubber sheet is correct, but that the sheets is all around the Earth (a bump in the rubber sheet only on all axis) and this sheet is space time. As we move forward in time we go around the worldlines of the curvature of space. When we let go of a ball and let it fall, to us it falls "down" but in the spacetime view, it just goes in a straight line through spacetime. Seen this in an PDF a while back (wish someone would make a video, easier to imagine). Hope that made sense.

We don't currently understand the nature of the big bang itself. We have a much better chance of understanding what got inflation started, and symmetry breaking may have had something to do with this (I'd really like to think so, at least), but as I said in a previous post, this has been difficult to implement.

Still trying to fully grasp symmetry breaking, finding a way to understand it without the need for complex words. "small fluctuations acting on a system which is crossing a critical point decide the system's fate, by determining which branch of a bifurcation is taken." What fluctuations? Could it be that there was just so much energy at the beginning that the only thing the universe could do is expand immensely to accommodate this energy?

 

[Chronos]

I think 'dark energy' was a player all along.

 

[bapowell]

The way i think they are saying it is the rubber sheet is correct, but that the sheets is all around the Earth (a bump in the rubber sheet only on all axis) and this sheet is space time.

Right. The rubber sheet analogy is unfortunately a 2D example of what's really a 3D rubber sheet. But you shouldn't need to use analogies to get at the physics -- we have the Einstein Equations. These tell us that geometric structures on a 4D semi-Riemannian manifold, namely the metric and connection, are the gravitational degrees of freedom.

Still trying to fully grasp symmetry breaking, finding a way to understand it without the need for complex words. "small fluctuations acting on a system which is crossing a critical point decide the system's fate, by determining which branch of a bifurcation is taken." What fluctuations?

Good question, but the answer depends on the system. In a condensed matter system approaching a phase transition (like water freezing to ice), these fluctuations are thermal. In particle physics, they are quantum fluctuations. In both cases there is a potential energy function determining the transition, and a move to lower energy completes the transition. The energy is a function of some system parameter (for example, magnetization for a magnetic system; in particle physics, the order parameter is a scalar field like the Higgs). The potential energy function has either a stable or metastable equilibrium at the local maximum as the system approaches the transition. Fluctuations in the order parameter will cause the system to complete the transaction, but there are different ways for the system to "roll down" the potential energy function. In a 2D potential, there are 2 choices. In a 3D potential, there are an infinite number. Look up "Mexican Hat potential" for more information.

Could it be that there was just so much energy at the beginning that the only thing the universe could do is expand immensely to accommodate this energy?

Not really. The expansion of the universe is a boundary condition imposed on the equations of motion at t=0. For a given energy density, one can accommodate a contracting universe as naturally as an expanding one.

 

[IsometricPion]

It is important not to ignore the warping in time.

Yes, without that you cannot really visualize how gravity works in GR. Here some links on space-time curvature visualizations:

http://www.relativitet.se/spacetime1.html

http://www.physics.ucla.edu/demoweb/...spacetime.html

http://www.adamtoons.de/physics/gravitation.swf

What they said. The rubber sheet analogy isn't very well suited to depicting the curvature of time (Correct me if I'm wrong, but I believe it is only meant to address the curvature of space.). I found the first link to be especially helpful in visualizing how the curvature of space-time produces trajectories. The second is useful if you like the hands-on approach. The third one is dynamic (it is an applet) and I found it very interesting, though as always "your mileage may vary".

 

[twofish-quant]

]Still trying to fully grasp symmetry breaking, finding a way to understand it without the need for complex words. "small fluctuations acting on a system which is crossing a critical point decide the system's fate, by determining which branch of a bifurcation is taken."

The first thing to do is to separate symmetry breaking from inflation. Inflation *might* have something to do with symmetry breaking, but it's better to think of it as something separate.

Here is an example of symmetry breaking.

Imaging a U shaped well with a ball in the middle. Now start pushing the center of the U with a stick so that it becomes a W. The ball in the middle will fall to one side or the other. That's broken symmetry. The W is symmetry just like a U, but if you have a ball in the middle it will move to one side or another.

Symmetry breaking happens in a *lot* of situations. Water. If you increase the pressure, then then energy equation for water starts looking like a U. If you decrease the pressure, it looks like a W only with one side lower than the other. If you lower the temperature, then one side of the W will be deeper and you get ice. If you increase the temperature then the other side will be deeper and you get water.

What fluctuations? Could it be that there was just so much energy at the beginning that the only thing the universe could do is expand immensely to accommodate this energy?

Imagine a ball that's balanced at the exact middle of the W. At that point *anything* will cause it to fall to one side or another. If nothing else the jiggling of the atoms in the ball will make it fall to one side or the other.

 

[Cajun]

What they said. The rubber sheet analogy isn't very well suited to depicting the curvature of time (Correct me if I'm wrong, but I believe it is only meant to address the curvature of space.). I found the first link to be especially helpful in visualizing how the curvature of space-time produces trajectories. The second is useful if you like the hands-on approach. The third one is dynamic (it is an applet) and I found it very interesting, though as always "your mileage may vary".

The third link is exactly what i was looking for, but i can't make sense out of it. Is it like the moon orbiting around the earth, and this let's you choose the size and speed of the objects? One thing i don't get and is probably the wrong question to ask, what is the space expanding into when there is more curvature? It seems to me to have something curve, that would imply a higher dimension that it is curving into? And would it be correct to treat time as a directional distance? For example, if i don't move through space, I am moving 100 percent through time? And when i move through space, it borrows from my movement through time?

 

[Cajun]

Symmetry breaking happens in a *lot* of situations. Water. If you increase the pressure, then then energy equation for water starts looking like a U. If you decrease the pressure, it looks like a W only with one side lower than the other. If you lower the temperature, then one side of the W will be deeper and you get ice. If you increase the temperature then the other side will be deeper and you get water.

Imagine a ball that's balanced at the exact middle of the W. At that point *anything* will cause it to fall to one side or another. If nothing else the jiggling of the atoms in the ball will make it fall to one side or the other.

So water in liquid form under normal pressure would be a W, with the middle of the hill as liquid, to the right steam, to the left ice. So when we talk about symmetry breaking in quantum physics, something was symmetrical in the begining, then something "bumped" the "ball" to one side, and symmetry breaking happens? What was that something that was symmetrical and what "bumped" the "ball"? Thats what i can't understand, they talk about symmetry, but under what context? The symmetry of matter and anti-matter? "In particle physics, supersymmetry breaking is the process to obtain a seemingly non-supersymmetric physics from a supersymmetric theory"
Are they talking about the Grand Unified Theory.

 

[bapowell]

So water in liquid form under normal pressure would be a W, with the middle of the hill as liquid, to the right steam, to the left ice.

No, it's ice on both sides. The W is an energy diagram -- both the left and right sides are "vacua" of lowest energy. Whether the order parameter goes right or left results in ice's domain structure: crystals align into domains with large groups pointing in the same direction.

So when we talk about symmetry breaking in quantum physics, something was symmetrical in the begining, then something "bumped" the "ball" to one side, and symmetry breaking happens?

Yup!

What was that something that was symmetrical and what "bumped" the "ball"?

The something that was symmetrical was a quantum field. In most models of symmetry breaking, the quantum field is a scalar (spin 0) field that couples to the other fields in the theory. The field has a potential energy, given by the W shaped function. The field can 'sit' at a place on this diagram, and it can evolve within it. It initially sits at the symmetrical position (center of W) but can roll down to either side. Since it's a quantum field, it undergoes fluctuations. So, if it starts out in a state of metastable equilibrium (center of W), a small fluctuation in either direction will send it rolling down.

Thats what i can't understand, they talk about symmetry, but under what context? The symmetry of matter and anti-matter?

No, they are talking about so-called gauge symmetries of the particle physics equations of motion. The scalar field sitting at the center of the W shares this symmetry. Think of the W -- a field sitting at the center has reflection symmetry (x -> -x). Once it rolls down to either vacuum, it no longer possesses this symmetry: it is broken. In the Standard Model of particle physics, the symmetries are more complicated but the idea is the same.

"In particle physics, supersymmetry breaking is the process to obtain a seemingly non-supersymmetric physics from a supersymmetric theory"
Are they talking about the Grand Unified Theory.

Some grand unified theories make use of supersymmetry. But the grand unified theory (whatever it is) is based on an additional symmetry, the so-called grand unification symmetry. The GUT symmetry must break to resemble our low energy universe. As the GUT symmetry breaks, the GUT force becomes separate forces. Supersymmetry, while it might be a good symmetry at high energy, is certainly broken in our low energy universe. So supersymmetry breaking (however it occurs) is another example of symmetry breaking.