Substitute to Dark Matter?

[Bo]

The problem with the ekpyrotic scenario is that, because it doesn't have an era of inflation (in the classical sense i've posted before on that subject) it requires an enourmous amount of 'fine tuning' (that means, you make your theory fit with experiments; instead of having the results follow automaticly from your theory). Fundamentally there is nothing wrong with fine tuning, but it is unwanted at least.

Linde has made a version of the ekpyrotic scenario with inflation; but encounters many problems there (i have a ref. somewhere; but not at home; it will come later).

 

Bo

[Freethinker]

Bo and Blame are at the same post count

 

Bo

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Posts: 112

Joined: 05/26/2004

 

BlameTheEx

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Posts: 112

Joined: 04/26/2004

 

Sorry, just thought it was curious and should be documented for some reason?

[BlameTheEx]

Bo.

 

The BB doesn't quite follow automatically ether. Hence the need for "dark energy". Still, perhaps the ekpyrotic needs more tuning than that. I await your references with considerable interest. I must say I find the ekpyrotic model attractive for the reasons given in my last post*. I do wonder if it is compatable with the non-expanding universe model I have been playing with.

 

* Oops, make that last post but one.

[Bo]

The BB doesn't quite follow automatically ether.

sorry, but i dont understand what you are referring to here...

 

As for some links:

The ekpyrotic scenario was more or less introduced here:

http://xxx.lanl.gov/pdf/hep-th/0103239

since this paper is quite technical, mr Steinhardt has made a simpler version of this in more general words:

http://wwwphy.princeton.edu/~steinh/npr/

 

The reply to this scenario was given here:

http://xxx.lanl.gov/pdf/hep-th/0104073

or here:

http://arxiv.org/PS_cache/hep-th/pdf/0205/0205259.pdf

 

since this is a bit technical again...

the 2 main points are this:

1) "is potential must take a very unusual form [script V](phi) = –10–22Mp4exp(–5000 phi/Mp). We describe the problems which appear when one attempts to obtain this potential in string theory."

 

The point that is made here is basicly very simple: For the Ekpyrotic scenario to work at all; we need a certain potential. This potential has an outragous exponential factor of -5000. whereas in string theory these kind of potentials have a typical exponential factor of ~1. (of course the exact proof is more detailed than this )

 

2) "Unlike inflation, this mechanism exponentially amplifies not only quantum fluctuations, but also initial inhomogeneities. As a result, to solve the homogeneity problem in this scenario, one would need the branes to be parallel to each other with an accuracy better than 10^–60 on a scale 10^30 times greater than the distance between the branes."

 

To understand this, one first needs to realise what the homogeneity problem is. This problem vasicly says: 'Why does, on the veeeery large scale, the universe looks everywhere the same?' Related to this problem is: "why, if the universe is homogenic, can we even exist?' (there clearly isn't an earth everywhere...) So on the small scale we have perturbations, but on the large scale everything is the same. Linde et al. point ou that the ekpyrotic scenario would basicly amplify any initial perturbations, so we would have large scale perturbations. The ekpyrotic scenario would only solve the homogenety problem if the initial conditions are tuned "...with an accuracy better than 10^–60 on a scale 10^30 times greater than the distance between the branes...". Nobody can of course claim that this is impossible, but -taking into acount that inflation-type scenario's automaticly solve the homogenity problem, I personally dont think the ekpyrotic scenarion is the right direction.

 

Of course it has to be said that there are many problems in inflation cosmology left unsolved....

 

Bo

[BlameTheEx]

Bo.

 

Damn. You have good arguments there.

 

The universes would have to have the same size. Unless.... can a universe be measure in meters? We had a similar problem before. Assuming the BB is correct the universe was much smaller once, and yet we can see that universe covering the entire sky of this, now, much larger universe. It would seem possible that co-ordinates must be measured in degrees, with the smaller universe "stretched" over the larger.

 

It also clear that the universes would have to hit exactly head on, but if they were travelling towards each other in another dimension, and there was ONLY one other dimension, that would be inevitable. I do realise that string theory calls for rather more than one extra dimension, but who really knows? Maybe there is only one more. Maybe there are others but universes are restricted to one by some force or principe.

 

Still, I have to agree that the ekpyrotic scenario has big problems.

 

Would you consider the possibility that matter was injected into the universe by some other method, at a time when it was large enough to contain the matter as normal matter? I have been thinking about it. If the matter WAS injected into our universe without a BB, there is no particular reason to think it was for the first time. Perhaps the dark matter is just burnt out stars from a previous injection. It would also explain how galaxies formed so soon. The galaxies were already there, but burned out. The newly injected matter, assumable mostly hydrogen gas, gravitated towards the burned out galaxies, and formed the stars we see today.

[Tormod]

Originally posted by: BlameTheEx

The newly injected matter, assumable mostly hydrogen gas, gravitated towards the burned out galaxies, and formed the stars we see today.

 

Some very interesting ideas, Blame. By injection, I *assume* you do not mean "by someone" but as a result of brane collision. Is that right?

 

How then would the gas come from one brane to another? And why would it be mostly hydrogen? Hydrogen is the simplest element but it still consists of quarks, proton, neutron, electron - it took time after the Big Bang for this to come together to create the hydrogen/helium ratio we observe today. If we skip the Big Bang and say the hydrogen was injected then it had to happen at a lower temperature than what we observe from the Big Bang, or else the gas would only be constituent particles.

[BlameTheEx]

Tormod

Tormod

 

Er. Well, certainly not by us 14 billion years ago, but I leave the question open. After all, we have no real idea where the mass/energy came from if the BB theory is correct. In that case the mass/energy just seems to have appeared in a universe that was no more than a point.

 

Frankly the whole matter is uncertain. things such as mass, time, and velocity exist within a universe. As best as we know these are purely internal properties. Who can say what the properties are between universes?

 

Still we could make a few assumptions. For the model I am proposing the injected matter arrived as matter. Much of it must have been in the form of light elements, probably mostly hydrogen. The lighter elements are not stable in this universe. They tends to be converted by stars into heavier elements. Eventually there should be nothing left but middle order elements like iron and silicon. Too heavy for fusion, too light for fission. If this injected matter came from a similar universe it should have not been stable there ether. I would guess that it must have been actually created at some time that was not very much greater than 14 billion years. All told, it must have been created somehow, and the most likely process would be one linked to its arrival.

 

I do rather like the idea that another universe was involved in some manner. The problem is the lack of antimatter in our universe. Antimatter seems to be identical but opposite to ordinary matter so how could any process that created matter not create an equal quantity of antimatter? Every time we have created matter with high energy particle experiments that is exactly what happens. Perhaps both were created, but separated by some unknown process into separate universes.

[Tormod]

Originally posted by: BlameTheEx

The problem is the lack of antimatter in our universe. Antimatter seems to be identical but opposite to ordinary matter so how could any process that created matter not create an equal quantity of antimatter?

 

Actually, isn't this one of the fundamental issues in the Big Bang theory? It states that *almost* equal amounts were created but the was a *miniscule* amount of matter over antimatter - which is the matter we see today. So the total amount of matter and antimatter that annihilated was enormous.

 

I also like the idea that our universe was somehow the outcome of a process. I think the Big Bang was just an event, not the ultimate beginning.

 

One book which discusses this is one which I reviewed a while back, "The Five Ages of the Universe".

 

http://www.hypography.com/article.cfm?id=29590

 

It has some very interesting views on the "evolution" of universes, in which black holes are actually gateways to new universes (so when a black hole forms a new universe begins).

 

Also, there was an interesting theory set forth by Ernest Sternglass in hos book "Before the Beginning" in which he claims that the Big Bang was a result of the friction of a relativistic electron-positron pair which orbited each other for 17 billion years.

 

http://www.hypography.com/article.cfm?id=28091

[Tormod]

Sorry, the title of Ernest Sternglass' book is "Before the Big Bang".

[BlameTheEx]

Tormod

 

I haven't heard that one, but why any imbalance at all? Matter and antimatter should have been produced in exactly equal quantities. It doesn't make a difference if their was just a slight imbalance or there was no antimatter produced at all. Ether way physics isn't working out as expected.

 

If there was just a slight imbalance, what happened to the energy from matter/antimatter annihilation?

[Aki]

I watched a video about that, and it says that because our universe is not exactly symmetrical, it causes the imbalance of matter and anti-matter. But I don't remember much from it....

[BlameTheEx]

Further musings.

 

I was wondering about the idea of matter and antimatter being separated into separate universes. While there are probably forces and effects that we don't know about, there is one that we do. Matter and antimatter are, as far as we can tell, effected by gravity in the same way, but they do have opposite charges. It is just plausible that the separation was due to some electrical or electromagnetic effect. Presumably there would be about as many protons as electrons, so the total charge should have been about zero, but electrons are lighter, and so travel faster. The same for positrons and antiprotons.

 

We could imagine some transitory electrical/electromagnetic force separating the electrons and positrons, with protons/antiprotons too slow to follow. The original electrical/electromagnetic force disappears and the protons move towards the electrons in an effort to cancel the imbalance. The same for positrons and antiprotons. Of course the electrons/positrons move back somewhat towards the centre, but there is still some effective separation. Once there was any separation at all, energy released by matter / antimatter reactions could force the separation wider.

 

This scenario begs an interesting question. If there is an imbalance between matter and antimatter in this universe, is there an imbalance of charge too? Suppose there were, say, too many electrons. The surplus would spread itself as evenly as possible throughout the universe, but there would still be repulsion. Could this be the "dark energy"?

 

Another idea.

 

Suppose there is equal quantities of matter/antimatter in the universe but electrical/electromagnetic forces separated them. The universe could now be composed of equal quantities of matter and antimatter galaxies. If so there might be some clues in pictures of the most distant galaxies. Also there should be at least occasional interactions between galaxies and anti-galaxies.

[Tormod]

Blame, I recommend this site:

 

Antimatter: Mirror of the universe

http://livefromcern.web.cern.ch/livefromcern/antimatter/

 

It goes through what antimatter is, how it is being studied and produced.

 

Especially this section is of interest to this discussion:

 

Antimatter in cosmology:

http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history03.html

[Freethinker]

Originally posted by: BlameTheEx

we have no real idea where the mass/energy came from if the BB theory is correct. In that case the mass/energy just seems to have appeared in a universe that was no more than a point.

There is no reason to pretend that mass had to exist as an immediate outcome of the BB. IT is well established that mass IS energy. E=MC^2 in case you are not aware of it. All we need do is explain energy and mass is explained.

Frankly the whole matter is uncertain. things such as mass, time, and velocity exist within a universe. As best as we know these are purely internal properties. Who can say what the properties are between universes?

Who says there IS a "between universes?" Just another personal opinion stated as an assertion, lacking any valid support for the assertion.

Still we could make a few assumptions.

Assumptions for WHAT? A "between universes" universe?

For the model I am proposing the injected matter arrived as matter.

So something that did not exist (matter) arrived from the thing that did not exist (matter).

 

To claim that matter came into existence by transferring matter from elsewhere does not answer where matter came from. It is just another turtle.

Much of it must have been in the form of light elements, probably mostly hydrogen.

So this nonexistant matter was made of "mostly hydrogen".

 

And the quarks came from Acme Quark Injectors?

The lighter elements are not stable in this universe.

They are completely stable.

They tends to be converted by stars into heavier elements.

This requires extreme conditions because the lighter elements are so extremely stable.

Eventually there should be nothing left but middle order elements like iron and silicon.

Ya screw the 2nd Law! Never did like it very much!

Too heavy for fusion, too light for fission.

And gravity no longer applies?

If this injected matter came from a similar universe

which came from this Universe? Oh, circular logic should be ignored? Or from another universe, which came from another universe, which came from... Turtles all the way down.

All told, it must have been created somehow,

Ah the catch eh? Which means every explanation you have given to this point is meaningless.

and the most likely process would be one linked to its arrival.

And we refer to that as the BB.

 

Square one!

I do rather like the idea that another universe was involved in some manner.

Good for you! Glad it makes you happy!

 

But it is a non-answer. Just more turtles

The problem is the lack of antimatter in our universe.

Not if we start looking at mirror matter, which was brought up elsewhere and is very interesting.

Antimatter seems to be identical but opposite to ordinary matter

Feynman shows that anti-matter is the same as matter travelling backwards in time. Thus we do not need to find an equal amount of anti-matter as being particles created in equal qty to matter in order to balance. And Hawkings (I think it was?) said that we can borrow energy (thus also matter) from other "time" as long as it all balances to zero ultimately

 

E*t >= h/(4 )

 

Which means that the uncertainty in energy times the uncertainty in time is greater than som

[BlameTheEx]

Tormod

 

My thanks for those links.

 

Its looking like none of my musings on antimatter are new. Ah well. I haven't spotted a separation into 2 universes theory yet, but I rather suspect it is only a matter of time.

[BlameTheEx]

Freethinker.

 

You are wasting your time, but I am not going to allow you to waste any more of mine. You have made it very clear what you think of me in the Gravity thread. You had best ignore me. I am certainly going to ignore you, and I can't imagine anybody reading your post in that Gravity thread expecting me to do otherwise.

[lindagarrette]

Originally posted by: Freethinker

 

Feynman shows that anti-matter is the same as matter travelling backwards in time. Thus we do not need to find an equal amount of anti-matter as being particles created in equal qty to matter in order to balance. And Hawkings (I think it was?) said that we can borrow energy (thus also matter) from other "time" as long as it all balances to zero ultimately

 

E*t >= h/(4 )

 

Which means that the uncertainty in energy times the uncertainty in time is greater than some very small number. Interpreted correctly, this means that it is possible to violate conservation of energy. In other words, it is possible to "borrow" energy E from "nowhere", given you return it in a time period t.

so how could any process that created matter not create an equal quantity of antimatter? Every time we have created matter with high energy particle experiments that is exactly what happens. Perhaps both were created, but separated by some unknown process into separate universes.

 

Which is it?

 

FT, This is most confusing. I did not get the impression from Feynmann that time was a factor in conservation of energy. Where did you get this equation? Could you explain more, or post references? I understand time is part of the e=mc**2 but only as it relates to the speed of light. Linda

 

Also, are you saying that mater (somthing) came form nothing? That would seem to be the reality, given all that's known so far.