Monday, July 2, 2007

The Loop Quantum Big Bounce

Theoretical physicist Martin Bojowald of Pennsylvania State University in University Park has a cosmology model, based on Loop Quantum Gravity, that claims to to be able to peer back before the big bang. What does his analysis find? It finds that our universe formed from another universe that collapsed down to a point then bounced back. This previous universe may have been physically different then ours in various ways, but after the bounce it became the universe we know and love. Also, he predicts the relics of the previous universe are probably too faint to be detected.

Not everyone is satisfied with the result. I for one a skeptical of loop quantum gravity since I don't understand it (yet) and the vast majority of theorists think other methods are better. Personally I really like the String Landscape model, which is being covered extensively at TASI 2007. (The theme is "The String Universe") Plus, the blog is named after the idea that the universe is formed from some sort of eternal inflation process so the bias has to come out.

Others like Caltech Cosmologist Sean Carroll have already blogged against it. A quote from him: "Someday we’ll understand how the Big Bang singularity is resolved in quantum gravity. But the real world is going to be more complicated (and more interesting) than these simple models."

Or as the Scientific American states:
Physicist Donald Marolf of the University of California, Santa Barbara, says the finding would be strengthened if it turned up in other models of quantum gravity, such as string theory. "No one has good control over this physics in any approach to quantum gravity," he says, "and it is important to explore a broad range of models and ideas."
Here is an article by New Scientist.

Hopefully in the future we will be able to test such theories.

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