Question about the Poincaré conjecture

In summary, although the Poincaré conjecture deals with closed simply connected 3-manifolds, it cannot be used to determine if the universe is the surface of a 3-sphere. This is because the conjecture does not take into account non-compact manifolds or manifolds with non-empty boundaries, and our observations of the universe being locally simply connected do not necessarily mean it is simply connected as a whole.
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donglepuss
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TL;DR Summary
Does Perelman’s proof of the Poincaré conjecture imply that the universe is the surface of a 3 sphere?
Does Perelman’s proof of the Poincaré conjecture imply that the universe is the surface of a 3 sphere?
 
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donglepuss said:
TL;DR Summary: Does Perelman’s proof of the Poincaré conjecture imply that the universe is the surface of a 3 sphere?

Does Perelman’s proof of the Poincaré conjecture imply that the universe is the surface of a 3 sphere?
No.
 
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How can a methematical proof tell us anything about the physical universe?
 
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You haven't provided your reasoning for why you would be curious about this, so I'm left to assume that it's because from our local observations the universe appears to be a simply connected 3-manifold. There are two main reasons this doesn't imply the universe is the 3-sphere:

1) The Poincare conjecture takes as its premise closed simply connected 3-manifolds. These are compact manifolds without boundary. There are an abundance of simply connected 3-manifolds that aren't homeomorphic to the 3-sphere, but they are also non-compact (3-dimensional Euclidean space) or have non-empty boundary (the 3-ball). It is possible that the universe is not a closed manifold.

2) Our observations imply the universe is locally simply connected (i.e. simply connected within some neighborhood of a point). Every manifold is locally simply connected because every manifold is locally Euclidean. However, not every manifold is simply connected.

Hope this helped.
 
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FAQ: Question about the Poincaré conjecture

What is the Poincaré Conjecture?

The Poincaré Conjecture is a fundamental problem in topology that asserts that every simply connected, closed 3-manifold is homeomorphic to the 3-sphere. In simpler terms, it states that if a three-dimensional shape has no holes and is compact, it can be continuously deformed into a sphere.

Who proved the Poincaré Conjecture?

The Poincaré Conjecture was famously proved by the Russian mathematician Grigori Perelman in the early 2000s. He used techniques from geometric topology and Ricci flow to demonstrate the conjecture's validity, building on the work of Richard S. Hamilton.

Why is the Poincaré Conjecture important?

The Poincaré Conjecture is important because it addresses fundamental questions in the field of topology, particularly in understanding the nature of three-dimensional spaces. Its resolution has implications for various areas of mathematics and theoretical physics, including the study of the universe's shape and the behavior of different geometrical structures.

What are the implications of the Poincaré Conjecture's proof?

The proof of the Poincaré Conjecture has led to advancements in the field of geometric topology and has influenced the study of 3-manifolds. It has also inspired further research into Ricci flow and other geometric analysis techniques, opening new avenues for exploration in mathematics.

What is the Clay Mathematics Institute's relation to the Poincaré Conjecture?

The Clay Mathematics Institute recognized the significance of the Poincaré Conjecture by including it in its list of seven "Millennium Prize Problems." A successful proof of the conjecture earned Perelman a prize of one million dollars, which he famously declined, stating that he was not interested in monetary rewards for his work.

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