Before the Big Bang: A Twin Universe?

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Until very recently, asking what happened at or before the Big Bang was considered by physicists to be a religious question. General relativity theory just doesn’t go there – at T=0, it spews out zeros, infinities, and errors – and so the question didn’t make sense from a scientific view.
But in the past few years, a new theory called Loop Quantum Gravity (LQG) has emerged. The theory suggests the possibility of a “quantum bounce,” where our universe stems from the collapse of a previous universe. Yet what that previous universe looked like was still beyond answering.

Now, physicists Alejandro Corichi from Universidad Nacional Autónoma de México and Parampreet Singh from the Perimeter Institute for Theoretical Physics in Ontario have developed a simplified LQG model that gives an intriguing answer: a pre-Big Bang universe might have looked a lot like ours. Their study will appear in an upcoming issue of Physical Review Letters.

“The significance of this concept is that it answers what happened to the universe before the Big Bang,” Singh told PhysOrg.com. “It has remained a mystery, for models that could resolve the Big Bang singularity, whether it is a quantum foam or a classical space-time on the other side. For instance, if it were a quantum foam, we could not speak about a space-time, a notion of time, etc. Our study shows that the universe on the other side is very classical as ours.”

The finding builds on previous research, with some important differences. Last year, Penn State physicist Martin Bojowald used a simplified version of LQG to show that a universe “on the other side” of the bounce could have existed. However, although that model produced valid math, no observations of our current universe could have lead to any understanding of the state of the pre-bounce universe, as nothing was preserved across the bounce. Bojowald described this as a sort of “cosmic amnesia.”

But Corichi and Singh have modified the simplified LQG theory further by approximating a key equation called the quantum constraint. Using their version, called sLQG, the researchers show that the relative fluctuations of volume and momentum in the pre-bounce universe are conserved across the bounce.

“This means that the twin universe will have the same laws of physics and, in particular, the same notion of time as in ours,” Singh said. “The laws of physics will not change because the evolution is always unitary, which is the nicest way a quantum system can evolve. In our analogy, it will look identical to its twin when seen from afar; one could not distinguish them.”

That means that our universe today, roughly 13.7 billion years after the bounce, would share many of the same properties of the pre-bounce universe at 13.7 billion years before the bounce. In a sense, our universe has a mirror image of itself, with the Big Bang (or bounce) as the line of symmetry.

“In the universe before the bounce, all the general features will be the same,” said Singh. “It will follow the same dynamical equations, the Einstein’s equations when the universe is large. Our model predicts that this happens when the universe becomes of the order 100 times larger than the Planck size. Further, the matter content will be the same, and it will have the same evolution. Since the pre-bounce universe is contracting, it will look as if we were looking at ours backward in time.”

Specifically, Corichi and Singh calculate that the change in relative fluctuations across the bounce is less than 10-56, a number which becomes even smaller for universes that grow larger than 1 megaparsec (our universe is somewhere between 3,000 and 6,000 megaparsecs).

As the researchers explain, having an identical twin universe would not necessarily mean that every single feature of both universes would be identical. For instance, it doesn’t imply that there was another you that existed at some point, a person who has already lived your life.

“If one were able to look at certain microscopic properties with a very strong microscope – a very high-energy experiment probing the Planck scale – one might see differences in some quantities, just as one might see that twins have different fingerprints or one has a mole and the other does not, or a different DNA,” Singh said.

As Singh explained, there are still many questions regarding the details of the possible pre-bounce universe.

“The biggest question is whether these features survive when we consider more complex situations,” he said. “For example, one would like to know whether some structures present in the previous universe – like galaxies – will leave some imprint in the new expanding one that will give rise to identical structure or just 'similar.' For instance, it could happen that, in the previous universe, galaxies formed in a different way, so one might have a different distribution of galaxies on the other side. We will be able to answer this question when we understand these models.”

Ultimately, Corichi and Singh’s model might even tell us what a future universe would look like. Depending on how fast our present universe is accelerating – which will ultimately determine its fate – there’s a possibility that a generalization of the model would predict a re-collapse of our own universe.

“Such a universe will have many bounces from one branch to another,” Singh said. “It is also possible that universes in different branches will be identical.”

More information: Corichi, Alejandro, and Singh, Parampreet. “Quantum bounce and cosmic recall.” Arxiv:0710.4543v2. Accepted for publication in Physical Review Letters.

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I'm hungry.

i wouldn't call pre-bounce "twin", would you

That.. I don't believe. Because then our universe should collapse and the Big Crunch theory can't happen according to the most recent evidence.
But of course this could be another difference... after all no mirror is perfect, and the Big Bang wasn't perfect in the first place

I'm not talking about research but evidence. Creationists constantly do new research to prove evolution wrong, but new research still can't beat the old evidence Darwin gathered.
If this is true, new evidence is needed.

Before the Big Bang there was a show called The Class in that time slot. It wasn't very good.

They are wrong, possibly right if there was only just one universe/big bang,
but just like people once believes the world was flat or we was at the center of the universe,
there are an infinite amount of possibilities of other big bangs, these would share some matter now and then,
perhaps even triggering an green bang or slow one down from happening letting the soup sort of cook.

I believe in the existence of infinite parallel universes, also known as multiverse.

In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
-- Mark Twain, Life on the Mississippi

Modern cosmology has so many unanswered questions and inconsistencies that I'm still more than a little skeptical about the Big Bang.

Working backwards doesn't always yield the correct answers...

It seems very plausible to me. It really brings new light to the riddle of what happened before this . In essence your saying this universe is in a constant state of rebirth . Am i correct?

I don't think that's what it means. The "Oscillatory universe" model would require this universe to end in a "big crunch." Observations so far seem to indicate that universal expansion is accelerating, if anything.

On the other hand, the "big bang" model requires a period of rapid "inflation" to match with observation, so according to cosmologists the rate of expansion of the universe can suddenly change for apparently no reason (which leaves me wondering if cosmologist know what they're talking about, like I said, I'm skeptical). Maybe cosmic expansion could suddenly reverse for no reason as well? Then we could have our big crunch after all.

Ah, but we're so far beyond big crunch cyclic models. I haven't read much about theoretical physics in a few years, but there was once talk about a brane-world based model in which the universe could be created through the collision of two brane universes suspended in a higher dimensional meta-universe. Or something like that. I assume the OP has some relation to this.

Alas, my attention span lessens with age and increased normality, so reading the OP is quite beyond my capabilities...