Manifold Atlas:Definition of “manifold”
(Difference between revisions)
Line 4: | Line 4: | ||
== Definition == | == Definition == | ||
<wikitex>; | <wikitex>; | ||
− | We assume that all manifolds are of a fixed dimension n. An '''n-dimensional manifold''' $M$ is a [[Wikipedia:Second_countable|second countable]] [[Wikipedia:Hausdorff_space|Hausdorff space]] for which every point $m \in M$ has a neighbourhood $U_m$ homeomorphic to an open subset of $\Rr^n$ or an open subset of $\Rr^n_+ = \{ x \in \Rr^n | x_1 \geq 0 \}$. The former points are the interior points of $M$. | + | We assume that all manifolds are of a fixed dimension n. An '''n-dimensional manifold''' $M$ is a [[Wikipedia:Second_countable|second countable]] [[Wikipedia:Hausdorff_space|Hausdorff space]] for which every point $m \in M$ has a neighbourhood $U_m$ homeomorphic to an open subset of $\Rr^n$ or to an open subset of $\Rr^n_+ = \{ x \in \Rr^n | x_1 \geq 0 \}$. The former points are the interior points of $M$. |
− | * The '''interior''' of $M$, denoted $\ | + | * The '''interior''' of $M$, denoted $\mathrm{int}(M)$, is the subset of points for which $U_m \subset \Rr^n$. |
− | * The '''boundary''' of $M$, written $\partial M$, is the compliemnt of the interior of $M$ | + | * The '''boundary''' of $M$, written $\partial M$, is the compliemnt of the interior of $M$. |
* $M$ is called '''closed''' if $M$ is compact and $\partial M$ is empty. | * $M$ is called '''closed''' if $M$ is compact and $\partial M$ is empty. | ||
Revision as of 10:29, 16 September 2009
This page defines the term “manifold” as used in the Manifold Atlas.
1 Definition
We assume that all manifolds are of a fixed dimension n. An n-dimensional manifold is a second countable Hausdorff space for which every point has a neighbourhood homeomorphic to an open subset of or to an open subset of . The former points are the interior points of .
- The interior of , denoted , is the subset of points for which .
- The boundary of , written , is the compliemnt of the interior of .
- is called closed if is compact and is empty.
Extra structures
Typically, but not necessarly, the word ``manifold`` will mean as above with extra structure. The extra structure may or may not be emphasised in notation and vocabulary.
- A smooth manifold is a manifold with an equivalence class of
2 References
This page has not been refereed. The information given here might be incomplete or provisional. |