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ulenrich
2009-Jun-09, 02:51 PM
If the universe is a flat universe, do we have some regions (in the voids) where there is a hyperbolic curvature of space?

If there is the tendency of spherical curvature in the galaxy clusters, what would be the overall curvature in a universe not having regions of hyperbolic curvature?

gzhpcu
2009-Jun-09, 03:16 PM
If the universe is a flat universe, do we have some regions (in the voids) where there is a hyperbolic curvature of space?

If there is the tendency of spherical curvature in the galaxy clusters, what would be the overall curvature in a universe not having regions of hyperbolic curvature?
As I stated in another thread, my understanding is that spacetime is flat in absence of matter. Any voids is space are flat.

Einsteins GR equation:
http://upload.wikimedia.org/math/8/5/3/85336276216c60d77ee34deff34931b1.pngequates distortion of spacetime with matter/energy. G is the gravitational constant, which determines the curvature of spacetime. Tμν is the energy-momentum stress tensor of matter. No matter, no curvature.

Argos
2009-Jun-09, 04:00 PM
A hyperbolic region would have negative G, no?

ulenrich
2009-Jun-09, 04:49 PM
A hyperbolic region would have negative G, no?
No, but could have some effects to pervasiveness/propagation of gravitation as distances change (... no exact euklidean geometry)

ulenrich
2009-Jun-09, 04:56 PM
G is the gravitational constant, which determines the curvature of spacetime. Tμν is the energy-momentum stress tensor of matter. No matter, no curvature.

And I guess a universe cannot be overall flat with just some regions curved spherical and no regions curved to the opposite.

Perhaps we found the main flaw of standard physics :hand:

Argos
2009-Jun-09, 05:18 PM
A hyperbolic region would have negative G, no?
No

Well, I think it would. :)

gzhpcu
2009-Jun-09, 05:49 PM
And I guess a universe cannot be overall flat with just some regions curved spherical and no regions curved to the opposite.

Perhaps we found the main flaw of standard physics :hand:
Why not? The universe could be flat overall and have local, curved clumps.

Argos
2009-Jun-09, 05:55 PM
Why not? The universe could be flat overall and have local, curved clumps.

In fact it does have.

ulenrich
2009-Jun-09, 11:19 PM
Why not? The universe could be flat overall and have local, curved clumps.
Think of the about 30 percent of (dark) matter where you must have curvature!

undidly
2009-Jun-10, 12:09 AM
Well, I think it would. :)

"Originally Posted by Argos
A hyperbolic region would have negative G, no?
Quote:
Originally Posted by ulenrich View Post
No
Well, I think it would."

So do I.
Are you suggesting that masses repel each other if they are at the place in space where there is negative curvature (part of the hyperbola)?.

There is such a place.
Place two SMALL masses along any line that is a radius from the center of the Earth.
SMALL so they do not cause a positive curve.

Release the masses.They move apart.
Some may say the lower mass accelerates faster because it is nearer to the Earth than the upper mass.
I am a nearby observer.
I say both masses are in a place with negative curve and that the masses are
repelling each other.

ulenrich
2009-Jun-10, 09:47 AM
Undidly and Argos,
if there was a little more annihilation of matter and antimatter at the time of bigbang, then the critical mass would not have been reached, our universe would have had hyperbolic curvature. And the string physicists say all possible universes out of 10^500 do exist in parallel. And the parallel universes theory explains gravitation the only force to reach out of our brane to parallel universes.

Are You telling me, that all universes with a hyperbolic curvature do have a repelling gravitation?
For me, I believe there is only a repelling gravitation if time is going backwards.

gzhpcu
2009-Jun-10, 10:58 AM
Shape of the universe:

http://en.wikipedia.org/wiki/Shape_of_the_Universe

Assuming that the universe is isotropic and homegenous: It can be spherical, flat or hyperbolic.

tusenfem
2009-Jun-10, 11:16 AM
Undidly and Argos,
if there was a little more annihilation of matter and antimatter at the time of bigbang, then the critical mass would not have been reached, our universe would have had hyperbolic curvature. And the string physicists say all possible universes out of 10^500 do exist in parallel. And the parallel universes theory explains gravitation the only force to reach out of our brane to parallel universes.

Are You telling me, that all universes with a hyperbolic curvature do have a repelling gravitation?
For me, I believe there is only a repelling gravitation if time is going backwards.

ulenrich, your question has been answered according to mainstream physics in the first few messages in this thread. If you insist that in regions where there is no mass space is curved hyperbolically, then you can discuss this idea in ATM, and will be asked to support it. Through the general relativity equation given above by gzhpcu it is clear, no mass in no curvature. If you have a beef with GR, then take it to ATM.