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marcus

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http://arxiv.org/abs/1110.3837

A smooth classical spacetime manifold can no more exist than can a smooth classical trajectory of a moving particle. Spacetime as a classical 4D manifold is a myth, sometimes a very useful one. Many PF people must already realize this so clearly that one hardly needs to say it.

Henrique Gomes and Tim Koslowski just posted a very interesting paper that among other things carries this idea further. They manage to make do with a 3D manifold, so there is no 4D "general covariance", and still get something that is equivalent to 1915 GRavity. The idea has been brewing a long time, it's not new with them.

And they put matter there---what looks to me like standard matter fields. See what you think.

Their time is not fundamental but instead is something that emerges----emerges like temperature emerges from a dungheap (Misthaufen). In the heap there are only molecules, nothing at a fundamental level called "temperature" Yet one can stick a thermometer into the compost pile and see the temperature rising: Time for them is a socalled emergent phenomenon.

They start the paper--it's a really good one, I think--with a quote from an article on spectral geometry by Tom Kopf and Mario Paschke:

That is beginning to look like the THEME of some new theories contending for the honor of replacing 1915 classical GR. Simply put, the theme is:

"Spacetime is a fairy tale."

A smooth classical spacetime manifold can no more exist than can a smooth classical trajectory of a moving particle. Spacetime as a classical 4D manifold is a myth, sometimes a very useful one. Many PF people must already realize this so clearly that one hardly needs to say it.

Henrique Gomes and Tim Koslowski just posted a very interesting paper that among other things carries this idea further. They manage to make do with a 3D manifold, so there is no 4D "general covariance", and still get something that is equivalent to 1915 GRavity. The idea has been brewing a long time, it's not new with them.

And they put matter there---what looks to me like standard matter fields. See what you think.

Their time is not fundamental but instead is something that emerges----emerges like temperature emerges from a dungheap (Misthaufen). In the heap there are only molecules, nothing at a fundamental level called "temperature" Yet one can stick a thermometer into the compost pile and see the temperature rising: Time for them is a socalled emergent phenomenon.

They start the paper--it's a really good one, I think--with a quote from an article on spectral geometry by Tom Kopf and Mario Paschke:

“Spacetime is the fairy tale of a classical manifold. It is irreconcilable with quantum effects in gravity and most likely, in a strict sense, it does not exist. But to dismiss a mythical being that has inspired generations just because it does not really exist is foolish. Rather it should be understood together with the story-tellers through whom and in whom the being exist. ”

That is beginning to look like the THEME of some new theories contending for the honor of replacing 1915 classical GR. Simply put, the theme is:

"Spacetime is a fairy tale."

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