Physlib

Physlib.SpaceAndTime.Space.Origin

The origin of `Space` and the Euclidean chart

The choice of origin for `Space d` is its vector-space zero `(0 : Space d)`. This file provides that `Zero` instance and the standard chart, isolated so they can be shared by the full module structure (`Space/Module.lean`) and the Euclidean action (`Space/EuclideanGroup/Action.lean`) without those depending on each other.

* `(0 : Space d)` — the coordinate origin, the point all of whose coordinates vanish. * `Space.chartEuclidean` — the standard affine isometry `Space d ≃ᵃⁱ[ℝ] EuclideanSpace ℝ (Fin d)`, `p ↦ p -ᵥ 0`, identifying a point with its coordinate vector relative to the origin.

5 declarations

definition

Map from Rd\mathbb{R}^d to Space d\text{Space } d via the origin

For a given dimension dNd \in \mathbb{N}, this function maps a vector vv from the dd-dimensional Euclidean vector space Rd\mathbb{R}^d (specifically `EuclideanSpace ℝ (Fin d)`) to a point in the affine space Space d\text{Space } d. The resulting point is obtained by translating the origin 0Space d0 \in \text{Space } d by the vector vv, denoted mathematically as v+v0v +_{\text{v}} 0.

theorem

The ii-th coordinate of vectorToSpace(v)\text{vectorToSpace}(v) equals viv_i

For any dimension dNd \in \mathbb{N}, vector vRdv \in \mathbb{R}^d, and index i{0,,d1}i \in \{0, \dots, d-1\}, the ii-th coordinate of the point vectorToSpace(v)\text{vectorToSpace}(v) in Space d\text{Space } d is equal to the ii-th component of the vector vv.

theorem

vectorToSpace(v)v0=v\text{vectorToSpace}(v) -_v 0 = v

For any dimension dNd \in \mathbb{N} and any vector vRdv \in \mathbb{R}^d (represented by `EuclideanSpace ℝ (Fin d)`), the displacement vector from the origin 0Space d0 \in \text{Space } d to the point vectorToSpace(v)\text{vectorToSpace}(v) is equal to vv. That is, vectorToSpace(v)v0=v\text{vectorToSpace}(v) -_v 0 = v.

definition

Standard Euclidean chart Space dRd\text{Space } d \cong \mathbb{R}^d via pp0p \mapsto p - 0

For any dimension dd, the standard Euclidean chart is an affine isometry equivalence between the dd-dimensional flat Euclidean space Space d\text{Space } d and the Euclidean vector space Rd\mathbb{R}^d. It identifies each point pSpace dp \in \text{Space } d with its coordinate vector relative to the origin 00 via the displacement map: pp0 p \mapsto p - 0

theorem

chartEuclidean(p)=p0\text{chartEuclidean}(p) = p - 0

For any dimension dNd \in \mathbb{N} and any point pp in the dd-dimensional flat Euclidean space Space d\text{Space } d, the value of the standard Euclidean chart at pp is equal to the displacement vector from the origin 00 to pp: chartEuclidean(p)=p0\text{chartEuclidean}(p) = p - 0 where 00 denotes the origin in Space d\text{Space } d and - denotes the displacement vector operation (subtraction in the affine space).