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What was there before Big Bang?

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marcus
#19
Oct13-12, 02:37 PM
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Marty that is the point I just made in post #17, immediately preceding yours. Before you can reason as you are doing you must define the geometric entropy. You have to say what the entropy of the geometry MEANS, and the temperature of the gravitational field (which is the geometry). It appears (the people writing about the thermodynamics of gravity seem to agree) that to make meaningful definitions in this case you need an OBSERVER.
And the quantities measured will be observer-dependent. there may be discontinuities in what you can or cannot define. Interesting bunch of problems.

Check out some of the Quantum Cosmology articles I brought up in the preceding search (see around post #14) Have to go, back later.
marcus
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Oct14-12, 01:15 PM
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Quote Quote by marcus View Post
Or you could jump in and have a look at the listing that you get with a "quantum cosmology" keyword search at a professional research library. Here are 379 papers in QC that appeared in 2009 or later, ordered by number of times the paper has been cited in other research. (citecount is a rough indicator of importance, so you tend to get the most significant papers listed first).

http://www-library.desy.de/cgi-bin/s...tecount%28d%29

This search simply uses the keyword "quantum cosmology" so you get all kinds of quantum cosmology. However the first 30 or 40 papers are mostly all "loop" qc (LQC). That's a particular type of model that a lot of people are currently working on. LQC goes back before the big bang in a fairly straightforward way---quantize the normal cosmology equation to include quantum effects working at extremely high density, so then the model does not fail mathematically and you can crank on back in time thru a kind of "bounce" and get to a familiar type of universe like what we see except contracting.

If you look further on the list, past the first 30 or so you will find OTHER kinds of quantum cosmology models, not only LQC...
Quote Quote by jackmell View Post
So basically just a bounce? Is that all? And how would a Universe like ours but contracting behave?...
That's right, the simplicity of the model is one of the most appealing things about it. The contracting phase behaves as an ordinary classical universe (same physical laws) until quantum corrections to GR take over very close to bounce.

The key person in this context is Abhay Ashtekar, who discovered an equivalent formulation of General Relativity (around 1980) which has become the basis for the canonical quantization of GR that was adapted for Quantum Cosmology.

Here's a New York Times piece on Ashtekar.
http://www.nytimes.com/1999/04/20/sc...d=print&src=pm

An essential point is that when GR is formulated using "Ashtekar variables" and quantized, there are quantum corrections to gravity. In the quantum cosmology developed by Ashtekar and others (see the literature list in post #15) at extreme density quantum effects dominate and gravity becomes repellent. There is a non-equilibrium regime where the universe continues to contract (as if by a kind of momentum) even though gravity is repelling and trying to force everything apart---black holes are coming unbound and smoothing out, the geometry is trying to be as uniform and even as possible.
This repellent effect of quantum gravity at extremely high density eventually stops the collapse and causes a rebound. By that time the metric and matter are smooth, evened out, by the non-equilibrium process I described.
Since 2006 there has been a lot of numerical simulations of the bounce by Ashtekar's group. You may be able to find more if you google Ashtekar or search for his papers in the preprint archive: http://arxiv.org
Here is my post #15 which has QC papers from 2009 to present.
firelyte
#21
Nov16-12, 03:12 AM
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Hi I'm new here to this forum and I'm afraid this might seem kind of dumb,
But I was thinking about lhc and how they say they recreate the conditions of the big bang with two particles slamming into each other and this also sometimes creates a small amount of anti-matter from what I've heard. And they say right before the big bang all the matter in the universe was packed into a very small point now what if it was caused by two extremely super massive black holes colliding with each other? This would create anti-matter and create a huge amount of energy right? It wouldn't seem impossible to me that there was more than just one singularity before the big bang. Would this explain why there ended up being less anti-matter than matter and explain why the universe spread out in a flat pattern? I have no idea but it was just a thought I had. I'm just a curious fan of physics and these are just the random things I think about while I'm at work and must just be ridiculous.

Maybe when I go to college I'll get a better understanding of the math and mechanics behind all of this. But for right now It's just something I find interest reading about.
phinds
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Nov20-12, 03:43 PM
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Quote Quote by firelyte View Post
Hi I'm new here to this forum and I'm afraid this might seem kind of dumb,
As they say, there are no dumb questions.

But I was thinking about lhc and how they say they recreate the conditions of the big bang with two particles slamming into each other and this also sometimes creates a small amount of anti-matter from what I've heard.
On a VERY tiny, localized scale, yes they create conditions similar to just after the singularity, including anti-matter

And they say right before the big bang all the matter in the universe was packed into a very small point
No, unless "they" are on TV, which presents sensationalism and not actual physics, they most emphatically do NOT say that. What they do say (assuming "they" are knowledgeable physicists) is that it was unbelievably hot and dense, but of completely unknown dimensions and topology.

now what if it was caused by two extremely super massive black holes colliding with each other? This would create anti-matter and create a huge amount of energy right? It wouldn't seem impossible to me that there was more than just one singularity before the big bang. Would this explain why there ended up being less anti-matter than matter and explain why the universe spread out in a flat pattern? I have no idea but it was just a thought I had. I'm just a curious fan of physics and these are just the random things I think about while I'm at work and must just be ridiculous.
Yeah, this last part has no basis in physics as it is currently understood. you would do well to read the FAQ in the cosmology section.

Maybe when I go to college I'll get a better understanding of the math and mechanics behind all of this. But for right now It's just something I find interest reading about.
Good ... keep reading !
Chronos
#23
Nov20-12, 11:12 PM
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I agree with marcus, science is a convergence of mathematics and observational evidence. We can no more ignore one than the other.


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