Uniform structure on topological groups #
This file defines uniform groups and its additive counterpart. These typeclasses should be
preferred over using [TopologicalSpace α] [TopologicalGroup α]
since every topological
group naturally induces a uniform structure.
Main declarations #
UniformGroup
andUniformAddGroup
: Multiplicative and additive uniform groups, i.e., groups with uniformly continuous(*)
and(⁻¹)
/(+)
and(-)
.
Main results #
TopologicalAddGroup.toUniformSpace
andcomm_topologicalAddGroup_is_uniform
can be used to construct a canonical uniformity for a topological add group.
See Mathlib.Topology.Algebra.UniformGroup.Basic
for further results.
A uniform group is a group in which multiplication and inversion are uniformly continuous.
- uniformContinuous_div : UniformContinuous fun (p : α × α) => p.1 / p.2
Instances
A uniform additive group is an additive group in which addition and negation are uniformly continuous.
- uniformContinuous_sub : UniformContinuous fun (p : α × α) => p.1 - p.2
Instances
A group homomorphism (a bundled morphism of a type that implements MonoidHomClass
) between
two uniform groups is uniformly continuous provided that it is continuous at one. See also
continuous_of_continuousAt_one
.
An additive group homomorphism (a bundled morphism of a type that implements
AddMonoidHomClass
) between two uniform additive groups is uniformly continuous provided that it
is continuous at zero. See also continuous_of_continuousAt_zero
.
A homomorphism from a uniform group to a discrete uniform group is continuous if and only if its kernel is open.
A homomorphism from a uniform additive group to a discrete uniform additive group is continuous if and only if its kernel is open.
Alias of UniformGroup.uniformContinuous_iff_isOpen_ker
.
A homomorphism from a uniform group to a discrete uniform group is continuous if and only if its kernel is open.
Alias of UniformAddGroup.uniformContinuous_iff_isOpen_ker
.
A homomorphism from a uniform additive group to a discrete uniform additive group is continuous if and only if its kernel is open.
The right uniformity on a topological group (as opposed to the left uniformity).
Warning: in general the right and left uniformities do not coincide and so one does not obtain a
UniformGroup
structure. Two important special cases where they do coincide are for
commutative groups (see comm_topologicalGroup_is_uniform
) and for compact groups (see
topologicalGroup_is_uniform_of_compactSpace
).
Equations
- TopologicalGroup.toUniformSpace G = UniformSpace.mk (Filter.comap (fun (p : G × G) => p.2 / p.1) (nhds 1)) ⋯ ⋯ ⋯
Instances For
The right uniformity on a topological additive group (as opposed to the left uniformity).
Warning: in general the right and left uniformities do not coincide and so one does not obtain a
UniformAddGroup
structure. Two important special cases where they do coincide are for
commutative additive groups (see comm_topologicalAddGroup_is_uniform
) and for compact
additive groups (see topologicalAddGroup_is_uniform_of_compactSpace
).
Equations
- TopologicalAddGroup.toUniformSpace G = UniformSpace.mk (Filter.comap (fun (p : G × G) => p.2 - p.1) (nhds 0)) ⋯ ⋯ ⋯