List of topologies

The following is a list of named topologies or topological spaces, many of which are counterexamples in topology and related branches of mathematics. This is not a list of properties that a topology or topological space might possess; for that, see List of general topology topics and Topological property.

Widely known topologies

* The Baire space − $\N^$ with the product topology, where $\N$ denotes the natural numbers endowed with the discrete topology. It is the space of all sequences of natural numbers.
* Cantor set − A subset of the closed interval , 1/math> with remarkable properties.
** Cantor dust
* Discrete topology − All subsets are open.
* Euclidean topology − The natural topology on Euclidean space $\Reals^n$ induced by the Euclidean metric, which is itself induced by the Euclidean norm.
** Real line − $\Reals$
** Space-filling curve
** Unit interval − , 1/math>
* Extended real number line
* Hilbert cube − , 1/1\times , 1/2\times , 1/3\times \cdots with the product topology.
* Indiscrete topology, chaotic topology, or Trivial topology − Only the empty set and its complement are open.
* Klein bottle
* Real projective line
* Sierpiński space, also called the connected two-point set − A 2-point set $\$ with the particular point topology $\.$
* Torus
** 3-torus
** Solid torus

Counter-example topologies

The following topologies are a known source of counterexamples for point-set topology.

* Alexandroff plank
* Appert topology − A Hausdorff, perfectly normal (T₆), zero-dimensional space that is countable, but neither first countable, locally compact, nor countably compact.
* Arens square
* Arens–Fort space − A Hausdorff, regular, normal space that is not first-countable or compact. It has an element (i.e. $p := (0, 0)$) for which there is no sequence in $X \setminus \$ that converges to $p$ but there is a sequence $x_\bull = \left(x_i\right)_^\infty$ in $X \setminus \$ such that $(0, 0)$ is a cluster point of $x_\bull.$
* Branching line − A non-Hausdorff manifold.
* Bullet-riddled square - The space , 12 \setminus \Q^2, where , 12 \cap \Q^2 is the set of bullets. Neither of these sets is Jordan measurable although both are Lebesgue measurable.
* Comb space
* Dieudonné plank
* Dogbone space
* Double origin topology
* Dunce hat (topology)
* E₈ manifold − A topological manifold that does not admit a smooth structure.
* Either–or topology
* Excluded point topology − A topological space where the open sets are defined in terms of the exclusion of a particular point.
* Fort space
* Half-disk topology
* House with two rooms − A contractible, 2-dimensional Simplicial complex that is not collapsible.
* Infinite broom
* Integer broom topology
* Irrational winding of a torus/ Irrational cable on a torus
* K-topology
* Lens space
* Lexicographic order topology on the unit square
* Line with two origins, also called the ' − It is a non-Hausdorff manifold. It is locally homeomorphic to Euclidean space and thus locally metrizable (but not metrizable) and locally Hausdorff (but not Hausdorff). It is also a T₁ locally regular space but not a semiregular space.
* Long line (topology)
* Moore plane, also called the ' − A first countable, separable, completely regular, Hausdorff, Moore space that is not normal, Lindelöf, metrizable, second countable, nor locally compact. It also an uncountable closed subspace with the discrete topology.
* Nested interval topology
* Overlapping interval topology − Second countable space that is T₀ but not T₁.
* Particular point topology − Assuming the set is infinite, then contains a non-closed compact subset whose closure is not compact and moreover, it is neither metacompact nor paracompact.
* Prüfer manifold − A Hausdorff 2-dimensional real analytic manifold that is not paracompact.
* Rational sequence topology
* Smith–Volterra–Cantor set − A closed nowhere dense (and thus meagre) subset of the unit interval , 1/math> that has positive Lebesgue measure.
* Sorgenfrey line, which is $\Reals$ endowed with lower limit topology − It is Hausdorff, perfectly normal, first-countable, separable, paracompact, Lindelöf, Baire, and a Moore space but not metrizable, second-countable, σ-compact, nor locally compact.
* Sorgenfrey plane, which is the product of two copies of the Sorgenfrey line − A Moore space that is neither normal, paracompact, nor second countable.
* Topologist's sine curve
* Tychonoff plank
* Vague topology
* Warsaw circle
* Whitehead manifold − An open 3-manifold that is contractible, but not homeomorphic to $\Reals^3.$

Hyperbolic geometry

* Gieseking manifold − A cusped hyperbolic 3-manifold of finite volume.
* Horosphere
** Horocycle
* Picard horn
* Seifert–Weber space

Paradoxical spaces

* Gabriel's horn − It has infinite surface area but finite volume.
* Lakes of Wada

Pathological embeddings of spaces

* Alexander horned sphere − A particular embedding of a sphere into 3-dimensional Euclidean space.
* Antoine's necklace − A topological embedding of the Cantor set in 3-dimensional Euclidean space, whose complement is not simply connected.

Unique

* Hantzsche–Wendt manifold − A compact, orientable, flat 3-manifold. It is the only closed flat 3-manifold with first Betti number zero.

Topologies defined in terms of other topologies

Natural topologies

List of natural topologies.

* Corona set
* Disjoint union (topology)
* Extension topology
* Initial topology
* Final topology
* Product topology
* Quotient topology
* Subspace topology
* Weak topology

Compactifications

Compactifications include:

* Alexandroff extension
** Projectively extended real line
* Bohr compactification
* Eells–Kuiper manifold
* Stone–Čech compactification
** Stone topology
* Wallman compactification

Topologies of uniform convergence

This lists named topologies of uniform convergence.

* Compact-open topology
** Loop space
* Interlocking interval topology
* Modes of convergence ( annotated index)
* Operator topologies
* Pointwise convergence
** Weak convergence (Hilbert space)
** Weak* topology
* Polar topology
* Strong dual topology
* Topologies on spaces of linear maps

Functional analysis

* Auxiliary normed spaces
* Finest locally convex topology
* Finest vector topology
* Helly space
* Mackey topology
* Polar topology

Operator topologies

* Dual topology
* Norm topology
* Operator topologies
* Pointwise convergence
** Weak convergence (Hilbert space)
** Weak* topology
* Strong dual space
* Strong operator topology
* Topologies on spaces of linear maps
* Ultrastrong topology
* Ultraweak topology/ weak-* operator topology
* Weak operator topology

Tensor products

* Inductive tensor product
* Injective tensor product
* Projective tensor product
* Tensor product of Hilbert spaces
* Topological tensor product

Other induced topologies

* Box topology
* Compact complement topology
* Duplication of a point: Let $x \in X$ be a non- isolated point of $X,$ let $d \not\in X$ be arbitrary, and let $Y = X \cup \.$ Then $\tau = \$ is a topology on $Y$ and $x$ and $d$ have the same neighborhood filters in $Y.$ In this way, $x$ has been duplicated.
* Extension topology

Fractal spaces

* Apollonian gasket
* Cantor set
* Koch snowflake
* Menger sponge
* Mosely snowflake
* Sierpiński carpet
* Sierpiński triangle

Topologies related to orders

* Alexandrov topology
* Order topology
** Lawson topology
** Poset topology
** Upper topology
** Scott topology
*** Scott continuity
* Roy's lattice space
* Specialization (pre)order

Topologies related to cardinality or ordinals

* Cocountable topology
** Given a topological space $(X, \tau),$ the '' '' on $X$ is the topology having as a subbasis the union of and the family of all subsets of $X$ whose complements in $X$ are countable.
* Cofinite topology
* Discrete two-point space − The simplest example of a totally disconnected discrete space.
* Double-pointed cofinite topology
* Finite topological space
* Ordinal number topology
* Pseudo-arc
* Split interval, also called the ' and the ' − All compact separable ordered spaces are order-isomorphic to a subset of the split interval. It is compact Hausdorff, hereditarily Lindelöf, and hereditarily separable but not metrizable. Its metrizable subspaces are all countable.

Other topologies

* Arithmetic progression topologies
* Cantor space
* Divisor topology
* Erdős space − A Hausdorff, totally disconnected, one-dimensional topological space $X$ that is homeomorphic to $X \times X.$
* Fake 4-ball − A compact contractible topological 4-manifold.
* Half-disk topology
* Hawaiian earring
* Hedgehog space
* Long line (topology)
* Partition topology
** Deleted integer topology
** Odd–even topology
* Pseudocircle − A finite topological space on 4 elements that fails to satisfy any separation axiom besides T₀. However, from the viewpoint of algebraic topology, it has the remarkable property that it is indistinguishable from the circle $S^1.$
* Rose (topology)
* Torus knot
* Zariski topology

See also

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Citations

References

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External links

π-Base: An Interactive Encyclopedia of Topological Spaces

{{Topology

General topology
Mathematics-related lists
Topological spaces