Paul Steinhardt's cyclic model

In summary, Paul Steinhardt's cyclic model of the universe suggests that two branes, or 4-dimensional objects, periodically collide in a higher dimensional spacetime. This collision creates effects similar to a big bang and raises questions about the relationship between time dimensions in different branes. It is unclear whether particles and "black matter" can be exchanged between branes, as it would depend on the specific model being considered.
  • #1
lolofromfrance
Hello. I think I don't understand very well the Paul Steinhardt's cyclic model of Universe(s). According to Paul Steinhardt, 2 universes get closer. Then, there's the big bounce, which products effects like a big bang. If 2 universes get closer, they have a (relative) speed (
speed is the derivative of the position with respect to time). So, for having a speed (for example in meters per second), we need a time dimension. However, we have a time dimension, but INSIDE our universe (a space-time universe). So, have we got ANOTHER time dimension OUTSIDE our universe ? Or have we a time dimension which is shared by several universes ?
 
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  • #2
lolofromfrance said:
According to Paul Steinhardt, 2 universes get closer.

They aren't "universes", they're branes--4-d objects in a higher dimensional spacetime.

lolofromfrance said:
If 2 universes get closer, they have a (relative) speed

Note that this is way oversimplified for a brane model. However, since the brane model assumes, as I said above, a higher dimensional spacetime in which our universe is embedded (as well as the other brane with which it periodically collides), there is a common time dimension, the time dimension of that higher dimensional spacetime. But there might not be a simple relationship between that time dimension and what we, inside our particular brane, perceive as time.
 
  • #3
Thank you very much Peter. So, if there are two 4-branes in the same universe, can we send or receive particles from the other 4-branes, gravitons for example ? More, that we call "black matter", could be it classical matter from the other 4-branes, which would have gravitationnal effects on OUR-4 branes (so this "black matter" would be not in our 4-branes but in the other 4-branes) ?
 
  • #4
lolofromfrance said:
if there are two 4-branes in the same universe, can we send or receive particles from the other 4-branes, gravitons for example ? More, that we call "black matter", could be it classical matter from the other 4-branes, which would have gravitationnal effects on OUR-4 branes (so this "black matter" would be not in our 4-branes but in the other 4-branes) ?

All of this would depend on the model. I'm not familiar enough with Steinhardt's model to know what it says about this.
 
  • #5
Ok thank you for your answer Peter [emoji6]
 

1. What is Paul Steinhardt's cyclic model?

The cyclic model is a cosmological theory proposed by Paul Steinhardt that suggests the universe undergoes a never-ending cycle of expansion and contraction, with no beginning or end.

2. How does the cyclic model differ from the Big Bang theory?

The Big Bang theory suggests that the universe began with a single, rapid expansion from a singularity. In contrast, the cyclic model proposes that the universe goes through cycles of expansion and contraction, with no definitive beginning or end.

3. What evidence supports the cyclic model?

Some evidence that supports the cyclic model includes the observations of cosmic microwave background radiation, which show a uniform distribution of matter and energy across the universe. This is consistent with a universe that has undergone cycles of expansion and contraction.

4. What are some criticisms of the cyclic model?

One criticism of the cyclic model is that it relies on the existence of a "bounce" mechanism that allows the universe to transition from contraction to expansion. This mechanism has not yet been fully explained or observed. Additionally, some scientists argue that the cyclic model does not adequately explain the observed acceleration of the universe's expansion.

5. How does the cyclic model explain the concept of time?

In the cyclic model, time is considered to be cyclical rather than linear. This means that the universe goes through repeated cycles of expansion and contraction, with no definitive beginning or end. Therefore, the concept of time as a linear progression may not apply in this model.

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