Topology induced by a family of seminorms #
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Main definitions #
seminorm_family.basis_sets
: The set of open seminorm balls for a family of seminorms.seminorm_family.module_filter_basis
: A module filter basis formed by the open balls.seminorm.is_bounded
: A linear mapf : E →ₗ[𝕜] F
is bounded iff every seminorm inF
can be bounded by a finite number of seminorms inE
.
Main statements #
with_seminorms.to_locally_convex_space
: A space equipped with a family of seminorms is locally convex.with_seminorms.first_countable
: A space is first countable if it's topology is induced by a countable family of seminorms.
Continuity of semilinear maps #
If E
and F
are topological vector space with the topology induced by a family of seminorms, then
we have a direct method to prove that a linear map is continuous:
seminorm.continuous_from_bounded
: A bounded linear mapf : E →ₗ[𝕜] F
is continuous.
If the topology of a space E
is induced by a family of seminorms, then we can characterize von
Neumann boundedness in terms of that seminorm family. Together with
linear_map.continuous_of_locally_bounded
this gives general criterion for continuity.
with_seminorms.is_vonN_bounded_iff_finset_seminorm_bounded
with_seminorms.is_vonN_bounded_iff_seminorm_bounded
with_seminorms.image_is_vonN_bounded_iff_finset_seminorm_bounded
with_seminorms.image_is_vonN_bounded_iff_seminorm_bounded
Tags #
seminorm, locally convex
An abbreviation for indexed families of seminorms. This is mainly to allow for dot-notation.
The sets of a filter basis for the neighborhood filter of 0.
The add_group_filter_basis
induced by the filter basis seminorm_basis_zero
.
Equations
- p.add_group_filter_basis = add_group_filter_basis_of_comm p.basis_sets _ _ _ _ _
The module_filter_basis
induced by the filter basis seminorm_basis_zero
.
Equations
- p.module_filter_basis = {to_add_group_filter_basis := p.add_group_filter_basis _inst_4, smul' := _, smul_left' := _, smul_right' := _}
The proposition that a linear map is bounded between spaces with families of seminorms.
- topology_eq_with_seminorms : t = p.module_filter_basis.topology
The proposition that the topology of E
is induced by a family of seminorms p
.
The x
-neighbourhoods of a space whose topology is induced by a family of seminorms
are exactly the sets which contain seminorm balls around x
.
The open sets of a space whose topology is induced by a family of seminorms are exactly the sets which contain seminorm balls around all of their points.
A separating family of seminorms induces a T₁ topology.
A family of seminorms inducing a T₁ topology is separating.
A family of seminorms is separating iff it induces a T₁ topology.
Convergence along filters for with_seminorms
.
Variant with finset.sup
.
Convergence along filters for with_seminorms
.
Limit → ∞
for with_seminorms
.
The topology induced by a family of seminorms is exactly the infimum of the ones induced by
each seminorm individually. We express this as a characterization of with_seminorms p
.
The uniform structure induced by a family of seminorms is exactly the infimum of the ones
induced by each seminorm individually. We express this as a characterization of
with_seminorms p
.
The topology of a normed_space 𝕜 E
is induced by the seminorm norm_seminorm 𝕜 E
.
Not an instance since 𝕜
can't be inferred. See normed_space.to_locally_convex_space
for a
slightly weaker instance version.
See normed_space.to_locally_convex_space'
for a slightly stronger version which is not an
instance.
The family of seminorms obtained by composing each seminorm by a linear map.
If the topology of a space is induced by a countable family of seminorms, then the topology is first countable.