I What Would the Universe Look Like as a Manifold with Boundary?

  • I
  • Thread starter Thread starter DDTG
  • Start date Start date
  • Tags Tags
    Manifold Universe
DDTG
Messages
3
Reaction score
1
what would the universe look like if its a manifold with boundary? what would it look like at the boundary? and what happens if u try to touch the boundary? is it just a black wall that's unbreakable?
 
Physics news on Phys.org
This would depend on what kind of boundary conditions you impose. As far as we can tell though, there is no evidence whatsoever to imply a boundary.
 
DDTG Global said:
what would the universe look like if its a manifold with boundary? what would it look like at the boundary? and what happens if u try to touch the boundary? is it just a black wall that's unbreakable?
There's no working model of the universe with a boundary.
 

Thread 'Euclidean geometry and gravity'

I asked a question here, probably over 15 years ago on entanglement and I appreciated the thoughtful answers I received back then. The intervening years haven't made me any more knowledgeable in physics, so forgive my naïveté ! If a have a piece of paper in an area of high gravity, lets say near a black hole, and I draw a triangle on this paper and 'measure' the angles of the triangle, will they add to 180 degrees? How about if I'm looking at this paper outside of the (reasonable)...
View full post »

Thread 'Is the variation of the metric ##\delta g_{\mu\nu}## a tensor?'

From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...
View full post »

Similar threads

I Ignoring boundary term in the action
Replies
32
Views
4K
I Black hole and coordinate time from the perspective of Alice outside
Replies
26
Views
2K
I Definition of manifolds with boundary
Replies
3
Views
2K
I Do any real macroscopic black holes have a singularity?
Replies
11
Views
2K
I Compact manifold cannot be represented by (single) parametric equation
Replies
5
Views
651
I Identifying Manifolds with Different Co-ordinates: Easy Solutions
Replies
16
Views
2K
B What Would You See at the Edge of the Expanding Universe?
Replies
17
Views
1K
B Question about the Entropy of a Black Hole Singularity
Replies
17
Views
3K
A Why are General relativity texts so much more formal?
Replies
28
Views
3K
B Universe Becoming a Black Hole: What Would It Look Like?
Replies
15
Views
2K

Hot Threads

Recent Insights

Back
Top