Big Bang Theory (Horizon Problem): Why is it assumed the universe began anisoptropic?

[Sorcerer]

I was just reading over the horizon problem wiki. And the whole issue lies around the assumption the universe began anisotropic. I would have assumed the universe began isotropic and the problem would be reversed, why isn't it still exactly isotropic?

There a numerous semantic and logic failures in the article too. Oxymorons such as "almost precisely". And "extremely isotropic". Why alter an absolute? Things are either precise or isotropic or they are not. The absolutes are required for the argument to be effective.

I can look around myself and see the universe is anisotropic.

http://en.wikipedia.org/wiki/Horizon_problem#Basic_concept

"This presents a serious problem; if the universe had started with even slightly different temperatures in different areas, then there would simply be no way it could have evened itself out to a common temperature by this point in time"

Why do they make the assumption it did, the whole problem is created by the conditional IF, wouldn't the more simple answer be to say then it didn't?

If we go to the point of the Big Bang singularity, then the universe is definately isotropic, a point is uniform in all directions. All directions are 0, 0=0.

Edited June 7, 2015 by Sorcerer

[Mordred]

Actually prior to inflation it could be anistrophic or isotropic. Inflation essentially washed out any aninstophies. There is afaik no observable data supporting one over the other as there is still 70+ viable inflation models.

[Strange]

I was just reading over the horizon problem wiki. And the whole issue lies around the assumption the universe began anisotropic. I would have assumed the universe began isotropic and the problem would be reversed, why isn't it still exactly isotropic?

 

It is not so much that is is assumed to have been anisotropic to start with, it is more the question "why should it be isotropic at all". Made worse by the fact that the CMBR is an almost perfect black body spectrum and is almost perfectly isotropic. You may see maps showing temperature variations and a large "cold spot", etc. But these variations are minute; thousnads, maybe millionths, of a degree.

 

I can look around myself and see the universe is anisotropic.

 

And it is still isotropic (and homogeneous) - especially at large enough scales. Obviously, at the scale of our solar system, galaxy and even local supercluster it is neither homogeneous nor isotropic. But on a large scale it is.

 

There a numerous semantic and logic failures in the article too. Oxymorons such as "almost precisely". And "extremely isotropic". Why alter an absolute? Things are either precise or isotropic or they are not. The absolutes are required for the argument to be effective.

 

Remember, Wikipedia is written by volunteers, many of whom are amateurs. And it is not edited (in the professional sense). So while the science pages (in particular) may be technically accurate, the quality of the writing is very variable. Don't confuse this with the quality of the science!

Edited June 7, 2015 by Strange

[Sorcerer]

@ Mordred : So you're saying that the horizon problem isn't a necessarily even a problem? But if it were, inflation solves it?

But the inflation model was made to solve this problem among 2 others, if there wasn't necessarily a problem, then what is the need for a solution to it, why not just assume it was already isotropic?

And further to that, if it was exactly isotropic, what model would allow for that to be changed, since we observe an (however slightly) anisotropic universe?

Why assume either is necessary, why shouldn't it just have been the right ammount of uniformity to begin with?

 

 

 

And it is still isotropic (and homegeneous) - especially at large enough scales. Obviously, at the scale of our solar system, galaxy and even local supercluster it is neither homogeneous nor isotropic. But on a large scale it is.

If it's anisotropic at small scales it is anisotropic at any scale.

"The cosmic microwave background radiation (CMB), which fills the universe, is almost precisely the same temperature everywhere in the sky, about 2.728 +/- 0.004 K. The differences in temperature are so slight that it has only recently become possible to develop instruments capable of making the required measurements."

 

Isotropic is defined as being uniform in all orientations. "almost precisely" isn't precisely = not uniform = anisotropic. Differences, no matter how slight, are differences. To be uniform and thus isotropic, there cannot be any differences.

It's like saying a pool ball is perfectly smooth, then looking at it under a microscope, seeing how rough it is and then demanding that it is still perfectly smooth.

______________________________________________________________________________

Inflation doesn't sit well with Occams razor, it is making up a mechanism to account for variables that could have just been that way to begin with. What mechanism created the variables which made inflation be that way to begin with and..... that line of reasoning can go to infinity.

Edited June 8, 2015 by Sorcerer

[Strange]

If it's anisotropic at small scales it is anisotropic at any scale.

 

I think you are missing the point.

 

There would have been quantum fluctuations in the early universe. It is generally agreed that it is these (following expansion) that led to the the small scale inhomogeneities that allowed the large scale structures and galaxies, stars, etc to form.

 

It's like saying a pool ball is perfectly smooth, then looking at it under a microscope, seeing how rough it is and then demanding that it is still perfectly smooth.

 

A pool ball is perfectly smooth at some scales but not at others. To claim otherwise, suggests you don't live in the real world.

 

https://what-if.xkcd.com/46/

BTW, Note that inflation is just an idea. And at least one of the people who developed the inflation hypothesis (Steinhardt) no longer thinks it is a good (or necessary) solution to the problem. But I am not really familiar with his latest ideas.

[Sorcerer]

"

Effects of asymmetries

Eventually, it was shown that new inflation does not produce a perfectly symmetric universe, but that tiny quantum fluctuations in the inflaton are created. These tiny fluctuations form the primordial seeds for all structure created in the later universe.^[53] These fluctuations were first calculated by Viatcheslav Mukhanov and G. V. Chibisov in the Soviet Union in analyzing Starobinsky's similar model.^[54][55][56] In the context of inflation, they were worked out independently of the work of Mukhanov and Chibisov at the three-week 1982 Nuffield Workshop on the Very Early Universe at Cambridge University.^[57] The fluctuations were calculated by four groups working separately over the course of the workshop: Stephen Hawking;^[58] Starobinsky;^[59] Guth and So-Young Pi;^[60] and James M. Bardeen, Paul Steinhardt and Michael Turner.^[61]"

So they want something that makes the universe isotropic, because it might have started anisotropic. But then go ahead and show that it makes the universe anisotropic?

[Mordred]

Take a small volume, suddenly increase that small volume 60+ efolds in less than one second. This causes supercoolng, then have a slow roll phase which causes a reheating phase. ( CMB is caused by this reheating)

Thermal equilibrium and the start of nucleosythesis.

 

Any small anisotropies will be washed out. Particularly due to the sudden volume increase, temperature cooling then reheating.

 

Encyclopaedia Inflationaris

 

http://arxiv.org/abs/1303.3787

 

I studied Muckanovs textbook, his inflation model is specifically a multi scalar inflation models.

 

Instead of one mechanism for inflation, his involves two permutations, one due to bosons the other fermions.

 

Some models are single scalar, ie chaotic eternal inflation. Scott Dodelson has similar ideas to Muckanov.

 

Both are equally viable, but so is Higgs inflation.

 

Remember there is well over 70+ viable inflation models. They are listed and studied in the above link.

 

There is some conjecture that some anisotropy will show up in the BAO baryon accoustic oscillations of the CMB. That is what your last post is specifically referring to once you study the math itself. Not the pop media explanations.

 

The last 4 years a huge amount of research is supportive of Higgs inflation.

 

Higg's inflation possible dark energy

 

http://arxiv.org/abs/1402.3738

http://arxiv.org/abs/0710.3755

http://arxiv.org/abs/1006.2801

 

a colleque of mine is currently studying inflation.

 

His research is extremely recent. You will easily see the involvement in the Baryon accoustic oscillations, as a possible determinant of what inflation models best suits the evidence. Without directly supporting a particular model....

 

http://arxiv.org/find/all/1/all:+AND+Brian+Powell/0/1/0/all/0/1

( In previous conversions with Brian he's taught me far more about inflation than the majority of the textbooks and articles I've studied,)

 

A couple of guides though older models on nucleosynthesis and inflation.

http://arxiv.org/pdf/hep-ph/0004188v1.pdf :"ASTROPHYSICS AND COSMOLOGY"- A compilation of cosmology by Juan Garcıa-Bellido

http://arxiv.org/abs/astro-ph/0409426 An overview of Cosmology Julien Lesgourgues

http://arxiv.org/pdf/hep-th/0503203.pdf "Particle Physics and Inflationary Cosmology" by Andrei Linde

http://www.wiese.itp.unibe.ch/lectures/universe.pdf:" Particle Physics of the Early universe" by Uwe-Jens Wiese Thermodynamics, Big bang Nucleosynthesis

 

The first two are overviews. The third is a full textbook, the last is based on Muchanov and Dodelson. Ie the metrics are the same as their textbooks.

Edited June 8, 2015 by Mordred

[Sorcerer]

 

I think you are missing the point.

 

There would have been quantum fluctuations in the early universe. It is generally agreed that it is these (following expansion) that led to the the small scale inhomogeneities that allowed the large scale structures and galaxies, stars, etc to form.

 

A pool ball is perfectly smooth at some scales but not at others. To claim otherwise, suggests you don't live in the real world.

 

https://what-if.xkcd.com/46/

BTW, Note that inflation is just an idea. And at least one of the people who developed the inflation hypothesis (Steinhardt) no longer thinks it is a good (or necessary) solution to the problem. But I am not really familiar with his latest ideas.

Why do the quantum fluctuations need to come after the initial inflation? What model suggests they occur at such large scales that it is necessary for inflation to even them out? This however isn't mentioned in the wiki article on the Horizon problem.

 

Wiki says variously unexplained things like this.

 

 

Given the example above, the two galaxies in question cannot have shared any sort of information; they are not in "causal contact". One would expect, then, that their physical properties would be different, and more generally, that the universe as a whole would have varying properties in different areas.

With no reason why that would be expected, the two galaxys came from the same initial universe, their properties should be similar.

 

In regards to the pool ball, I disagree, the ball isn't PERFECTLY smooth. It's a sloppy aproximation of language, to use something which defines an object as pefectly something to describe something which isn't. Pseudoisotropic, I could've accepted.

 

Don't get me wrong I like the inflation hypothesis, but for other things it explains, it's just that I thought it odd that one of the problems it was attempting to solve seemed to be made up from an unecessary assumption for the express purpose.

 

 

 

[Mordred]

You can't fully trust wiki. As mentioned its not written by professional scientists.

 

Use the material I provided. (Key note I'm not asking you to favor any particular model, as 70+ models are equally viable) however Planck data strongly supports the single scalar models, if shown as most favourable with further research, narrows the models to less than 10 out of the first link.

Edited June 8, 2015 by Mordred

[Sorcerer]

About as close as wiki gets to a mention is:

 

One consequence of cosmic inflation is that the anisotropies in the Big Bang are reduced but not entirely eliminated.

This wording is saying that the universe BEGAN anisotropic. It should deal with the time frame between the moment of the Big Bang and the beggining of inflation, in which quantum fluctuations could cause the universe to become anisotropic.

However, since quantum fluctuations are a probabalistic thing, there isn't any reason to assume certainty in their occurance at any specific time. Did they HAVE to occur?

Edited June 8, 2015 by Sorcerer

[Mordred]

About as close as wiki gets to a mention is:

This wording is saying that the universe BEGAN anisotropic. It should deal with the time frame between the moment of the Big Bang and the beggining of inflation, in which quantum fluctuations could cause the universe to become anisotropic.

 

However, since quantum fluctuations are a probabalistic thing, there isn't any reason to assume certainty in their occurance at any specific time. Did they HAVE to occur?

No its not needed in all models, one example Higgs inflation. Which is simply put due to the Higgs metastability. Ie it changes potential of influence at high temperature (extremely roughly speaking)

Now to explain the reasoning behind wiki's article. Let's look at Allen Guths "false vacuum" the original inflation model.

 

In this model you have two vacuum states. False vacuum and true vacuum. False vacuum being the higher energy state. True vacuum being the Lower energy state. A high vacuum state (false vacuum will quantum vacuum to the Lower energy state(true vacuum). The amount of energy transferred determines the rate of inflation.

 

The vast majority of inflation models use this technique, (but not all of them)

 

There is a problem though, once this mechanism starts its extremely difficult to stop. Google "runaway inflation".

 

Guth, Steinhardt etc tried solving runaway inflation by introducing slow roll mechanism. This leads to eternal inflation, chaotic eternal inflation, slow roll approximation, natural inflation, hill inflation etc etc etc . All these models were developed to solve runaway inflation.

 

The inflaton is involved in these models. Some models use the curvaton, others have different virtual particles.

 

This is just personal opinion but my vote goes to Higgs. The beauty here is the Higgs already has a natural Mexican hat potential (metastability). Does not require exotic particles either real or virtual. Not does it require anisotropy regions and quantum tunnelling.

(If you think about false vacuum higher to lower energy density regions the anisotropy regions will end up balanced)

Edited June 8, 2015 by Mordred

[Sorcerer]

The horizon problem explanation in the wiki article on inflation is a little more clear, however I am still not understanding its reasoning. http://en.wikipedia.org/wiki/Cosmic_inflation#Horizon_problem

It says that in the traditional big bang model areas of the universe do not have enough time to equilibrate because a particle horizon seperates them. I don't understand, they started at equilibrium, why do they need time to do nothing?

Also I found a way to word the large scale uniformity of the universe which doesn't conflict with my semantics. "Statisically Isotropic".

[Mordred]

To answer this you have to understand how fast information can travel.

 

The horizon problem amounts to. " How can our universe have the same thermodynamic conditions everywhere, when the maximum speed any information can travel is the speed of light. Yet the universe is in the same thermodynamic state everywhere we look at a given distance and point in time.". This is in more technical terms called "shared causality". Thermodynamic processes on one side of our observable universe do not have time to interact with the other side of our observable universe. The speed of information prevents this from being able to occur.

 

So why are these disconnected regions so evenly matched?

 

The answer is they can only match thermodynamically is if they were once causally connected in the past. Now here is the technical part, in order to stay equally uniform and cover our entire observable universe the universe must have at one time time been small enough in volume that thermodynamic processes could balance out in a uniform homogeneous and isotropic state. However in order to explain that same state throughout the entire volume of the observable universe today without developing anisotropy regions. The universe must rapidly inflate an incredible volume in a very finite period of time. This sets the minimum number of e-folds of inflation. Which is roughly 60 e-folds.

 

"In science, e-folding is the time interval in which an exponentially growing quantity increases by a factor of e; it is the base-e analog of doubling time."

 

http://en.m.wikipedia.org/wiki/E-folding

 

http://en.m.wikipedia.org/wiki/E_(mathematical_constant)

 

Here is a good detailed article on shared causality.

 

http://arxiv.org/abs/1305.3943

 

Here is a brief article covering the horizon problem (without math detail FAQ style.)

 

http://www.astronomynotes.com/cosmolgy/s12.htm

The articles I already posted covers this in greater detail.

By the way +1 for your dedication for understanding the current model rather than inventing your own

Your the type of poster we like to see more often. Those that ask questions rather than assuming they have the answers that science doesnt or that they do not understand so invent their own explanation.

Edited June 8, 2015 by Mordred

[Sorcerer]

The answer is they can only match thermodynamically is if they were once causally connected in the past. Now here is the technical part, in order to stay equally uniform and cover our entire observable universe the universe must have at one time time been small enough in volume that thermodynamic processes could balance out in a uniform homogeneous and isotropic state. However in order to explain that same state throughout the entire volume of the observable universe today without developing anisotropy regions.

 

Why? What causes it to develop anisotropy regions under non-inflation expansion models of the Big Bang?

 

Classical models of the Big Bang have a very obvious point where everything is causally connected in the past and was small enough in volume that thermodynamic processes could balance out in a uniform homogeneous and isotropic state. It is the moment directly after the Big Bang, or the singularity itself, if you allow it to exist.

 

 

From wiki:

 

However, in order to work, and as pointed out by Roger Penrose from 1986 on, inflation requires extremely specific initial conditions of its own, so that the problem (or pseudo-problem) of initial conditions is not solved: "There is something fundamentally misconceived about trying to explain the uniformity of the early universe as resulting from a thermalization process. [...] For, if the thermalization is actually doing anything [...] then it represents a definite increasing of the entropy. Thus, the universe would have been even more special before the thermalization than after."^[3]

 

 

Is Roger Penrose's objection a relevant one?

[Strange]

Wiki says variously unexplained things like this.

 

Remember, Wikipedia is written by volunteers, many of whom are amateurs. And it is not edited (in the professional sense). So while the science pages (in particular) may be technically accurate, the quality of the writing is very variable. Don't confuse this with the quality of the science!

[Sorcerer]

Yes, thanks Strange, it was a good point the first time I read it too.

Is it quantum fluctuations are responsible for creating anisotrophy which must be quickly evened out by inflation?

If so, aren't quantum fluctuations a probalistic effect that occur equally over all points in space? Aren't they them isotropic and homogenous. Why is it necessary that quantum fluctuations in the early universe create anisotropic effects?