Group seminorms #
This file defines norms and seminorms in a group. A group seminorm is a function to the reals which is positive-semidefinite and subadditive. A norm further only maps zero to zero.
Main declarations #
AddGroupSeminorm: A functionffrom an additive groupGto the reals that preserves zero, takes nonnegative values, is subadditive and such thatf (-x) = f xfor allx.NonarchAddGroupSeminorm: A functionffrom an additive groupGto the reals that preserves zero, takes nonnegative values, is nonarchimedean and such thatf (-x) = f xfor allx.GroupSeminorm: A functionffrom a groupGto the reals that sends one to zero, takes nonnegative values, is submultiplicative and such thatf x⁻¹ = f xfor allx.AddGroupNorm: A seminormfsuch thatf x = 0 → x = 0for allx.NonarchAddGroupNorm: A nonarchimedean seminormfsuch thatf x = 0 → x = 0for allx.GroupNorm: A seminormfsuch thatf x = 0 → x = 1for allx.
Notes #
The corresponding hom classes are defined in Analysis.Order.Hom.Basic to be used by absolute
values.
We do not define NonarchAddGroupSeminorm as an extension of AddGroupSeminorm to avoid
having a superfluous add_le' field in the resulting structure. The same applies to
NonarchAddGroupNorm.
References #
- [H. H. Schaefer, Topological Vector Spaces][schaefer1966]
Tags #
norm, seminorm
A seminorm on an additive group G is a function f : G → ℝ that preserves zero, is
subadditive and such that f (-x) = f x for all x.
- toFun : G → ℝ
The bare function of an
AddGroupSeminorm. - map_zero' : self.toFun 0 = 0
The image of zero is zero.
The seminorm is subadditive.
The seminorm is invariant under negation.
Instances For
A seminorm on a group G is a function f : G → ℝ that sends one to zero, is submultiplicative
and such that f x⁻¹ = f x for all x.
- toFun : G → ℝ
The bare function of a
GroupSeminorm. - map_one' : self.toFun 1 = 0
The image of one is zero.
The seminorm applied to a product is dominated by the sum of the seminorm applied to the factors.
The seminorm is invariant under inversion.
Instances For
A nonarchimedean seminorm on an additive group G is a function f : G → ℝ that preserves
zero, is nonarchimedean and such that f (-x) = f x for all x.
The seminorm applied to a sum is dominated by the maximum of the function applied to the addends.
The seminorm is invariant under negation.
Instances For
NOTE: We do not define NonarchAddGroupSeminorm as an extension of AddGroupSeminorm
to avoid having a superfluous add_le' field in the resulting structure. The same applies to
NonarchAddGroupNorm below.
A norm on an additive group G is a function f : G → ℝ that preserves zero, is subadditive
and such that f (-x) = f x and f x = 0 → x = 0 for all x.
- eq_zero_of_map_eq_zero' (x : G) : self.toFun x = 0 → x = 0
If the image under the seminorm is zero, then the argument is zero.
Instances For
A seminorm on a group G is a function f : G → ℝ that sends one to zero, is submultiplicative
and such that f x⁻¹ = f x and f x = 0 → x = 1 for all x.
- eq_one_of_map_eq_zero' (x : G) : self.toFun x = 0 → x = 1
If the image under the norm is zero, then the argument is one.
Instances For
A nonarchimedean norm on an additive group G is a function f : G → ℝ that preserves zero, is
nonarchimedean and such that f (-x) = f x and f x = 0 → x = 0 for all x.
- eq_zero_of_map_eq_zero' (x : G) : self.toFun x = 0 → x = 0
If the image under the norm is zero, then the argument is zero.
Instances For
NonarchAddGroupSeminormClass F α states that F is a type of nonarchimedean seminorms on
the additive group α.
You should extend this class when you extend NonarchAddGroupSeminorm.
- map_zero (f : F) : f 0 = 0
The image of zero is zero.
The seminorm is invariant under negation.
Instances
NonarchAddGroupNormClass F α states that F is a type of nonarchimedean norms on the
additive group α.
You should extend this class when you extend NonarchAddGroupNorm.
- eq_zero_of_map_eq_zero (f : F) {a : α} : f a = 0 → a = 0
If the image under the norm is zero, then the argument is zero.
Instances
Seminorms #
Composition of a group seminorm with a monoid homomorphism as a group seminorm.
Instances For
Composition of an additive group seminorm with an additive monoid homomorphism as an additive group seminorm.
Instances For
Any action on ℝ which factors through ℝ≥0 applies to an AddGroupSeminorm.
Any action on ℝ which factors through ℝ≥0 applies to an AddGroupSeminorm.
Any action on ℝ which factors through ℝ≥0 applies to a NonarchAddGroupSeminorm.