Manifolds and cell complexes Topological manifolds: basic notions Example
Torus
Builds on Quotient topologyProduct topologyCircle as a quotient of the real line
Example
Let be the equivalence relation on the square generated by and for all . The quotient space , with the quotient topology, is the torus .
Remarks
The torus is homeomorphic to the product of two circles, with the product topology, and to . It is also homeomorphic to a surface in : turn a circle about an axis in its plane that does not meet the circle. The torus is a compact, connected surface. It is not homeomorphic to the sphere.
Reading path
To understand this page from the ground up, read these 63 pages in order. The foundations come first.
- Element definition
- Proposition concept
- Real numbers object
- Set definition
- Conjunction definition
- Disjunction definition
- Implication definition
- Predicate definition
- Empty set object
- Family of sets definition
- Ordered pair definition
- Intersection definition
- Union definition
- Set-builder notation concept
- Existential quantifier definition
- Universal quantifier definition
- Cartesian product definition
- Subset definition
- Union of a family of sets definition
- Uniqueness quantifier definition
- Binary relation definition
- Universal set definition
- Topological space definition
- Reflexive relation definition
- Symmetric relation definition
- Transitive relation definition
- Complement definition
- Function definition
- Basis of a topology definition
- Subspace topology definition
- Equivalence relation definition
- Metric space definition
- Product topology definition
- Preimage of a set definition
- Codomain definition
- Function composition definition
- Injective function definition
- Open ball definition
- Equivalence class definition
- Surjective function definition
- Metric topology definition
- Quotient set definition
- Bijective function definition
- Open set definition
- Quotient topology definition
- Inverse function definition
- Hausdorff space definition
- Open cover definition
- Closed set definition
- Continuous map of topological spaces definition
- Compact space definition
- Complement of an open set is closed statement
- Homeomorphism definition
- Universal property of the quotient topology statement
- Continuity via closed sets statement
- Compact set definition
- Compactness via open covers statement
- Compact subsets of a Hausdorff space are closed statement
- Closed subsets of compact sets are compact statement
- Continuous image of a compact set is compact statement
- Continuous bijection from a compact space to a Hausdorff space is a homeomorphism statement
- Circle as a quotient of the real line example
- Torus example
Where this leads
14 pages build on this one.
Further reading
- Web https://en.wikipedia.org/wiki/Torus, Topology
About this page
| Tag | 03NM7DZXXC |
|---|---|
| URI | m2://03NM7DZXXC |
| Kind | example |
| Writing | W2 usable |
| MSC | 57K20 |
| Instance of | Topological space |
| Uses | Quotient topology, Product topology, Circle as a quotient of the real line |
| Same as |
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