View Full Version : Test Tube universes


BenTheMan
12-27-07, 12:26 PM
The Telegraph reports (http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2007/12/23/scicosmos123.xml) about experiments using Helium 3 to model the early universe.

The equations used to describe this superfluid turn up in many other branches of physics. "For instance, the internal structure of the superfluid mirrors very closely the structure of space-time itself, the 'background' of the universe in which we live," says Haley.

There's not a lot of content in the article, which is true of most scientific writing. You also have to be careful, because these articles are always full of grandiose claims. But this stuff is incredibly interesting, nonetheless. The Nature article costs something like $20, so when I get back to Columbus I'll try to access it from my office and sumarize it. Also, if you find any other references, post them here.

Basically, the early universe is modeled as a perfect fluid, which gives some restrictions on the form of the stress energy tensor (i.e. the right hand side of Einstein's equations). The same set of assumptions apply to Helium 3 when it is very close to absolute 0. The wikipedia entry (http://en.wikipedia.org/wiki/Equation_of_state_(cosmology)) looks to be pretty good.

Peter Woit (http://www.math.columbia.edu/~woit/wordpress/?p=634) has a typically acerbic response to claims of string theory's testability.

p-brane
12-28-07, 04:49 PM
Peter Woit has a typically acerbic response to claims of string theory's testability.


I think willfully dishonest is more accurate than acerbic.

BenTheMan
12-28-07, 09:42 PM
I think willfully dishonest is more accurate than acerbic.

I do my best to remain neutral here :) By the way, do I know you?

invert_nexus
12-28-07, 10:28 PM
Wasn't the superfluidic nature of helium-3 disproven? It was actually imperfections within the crystals which mimicked superfluid flow?

p-brane
12-28-07, 10:33 PM
...do I know you?


Yes.

BenTheMan
12-29-07, 11:54 AM
Wasn't the superfluidic nature of helium-3 disproven? It was actually imperfections within the crystals which mimicked superfluid flow?

I don't know. I have been searching for a few minutes online and can't find any references to this. Do you remember where you read it?

zephir
12-29-07, 06:15 PM
.. ..this stuff is incredibly interesting, nonetheless...

This stuff is well known for long time (http://physicsworld.com/cws/article/print/1528) already. What has changed?

BenTheMan
12-29-07, 06:42 PM
This stuff is well known for long time (http://physicsworld.com/cws/article/print/1528) already. What has changed?

Well, the novel idea is that it can be used to simulate the very early universe, I think.

superluminal
12-29-07, 07:18 PM
Wasn't the superfluidic nature of helium-3 disproven? It was actually imperfections within the crystals which mimicked superfluid flow?
Really? I find all sorts of current research available on the web. Are you thinking of "boojums" that can cause the superfluid flow to collapse?

Just Curious
01-04-08, 10:28 AM
Thanks for all the replies guys, even if we did go a bit off topic, read the original post and then see where we ended up very quickly. I got the answer I wanted so I am happy.