The sheaf of C^n functions on a manifold: sections and evaluation #
For a manifold M modelled on (EM, HM) over a nontrivially normed field 𝕜, a manifold N
modelled on (E, H) and any smoothness n : ℕ∞ω, the sections of the sheaf of C^n functions
contMDiffSheaf IM I n M N over U are, definitionally, the bundled maps C^n⟮IM, U; I, N⟯
(contMDiffSheaf.obj_eq), and likewise for the sheaf of commutative rings
contMDiffSheafCommRing IM I n M R of C^n functions valued in a C^n commutative ring R, on
which restriction is restriction of functions (contMDiffSheafCommRing.map_apply).
The evaluation at a point, contMDiffSheafCommRing.eval IM I n M R x : stalk x →+* R, takes the
germ of a section to its value at x (eval_germ) and is surjective, every value being taken by a
constant section (eval_surjective); in particular the stalks are nontrivial when R is.
This is the sheaf of regular functions of Bierstone–Milman's regular coordinate charts
[BM97, (0.3)]: the coordinates of a chart are sections and the stalks are the local rings of germs
(contMDiffSheafCommRing.instLocalRing_stalk).
The sections of contMDiffSheaf IM I n M N over U are, definitionally, the C^n functions
C^n⟮IM, U; I, N⟯.
The sections of contMDiffSheafCommRing IM I n M R over U are, definitionally, the C^n
functions C^n⟮IM, U; I, R⟯.
Restriction is restriction of functions.
Evaluation at x on the sections over an open neighbourhood U of x, valued in the lift of
R to the universe of M (so that it is a morphism of CommRingCat.{u}).
Equations
- Manifold.contMDiffSheafCommRing.evalAt IM I n M R x U = CommRingCat.ofHom (ULift.ringEquiv.symm.toRingHom.comp (ContMDiffMap.evalRingHom ⟨x, ⋯⟩))
Instances For
The evaluation at x, as a morphism from the stalk of C^n functions at x to the lift of
R in the category of commutative rings.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The evaluation ev_x : 𝒪_x →+* R at x on the stalk of C^n functions.
Equations
- Manifold.contMDiffSheafCommRing.eval IM I n M R x = ULift.ringEquiv.toRingHom.comp (CommRingCat.Hom.hom (Manifold.contMDiffSheafCommRing.evalHom IM I n M R x))
Instances For
The evaluation at x of the germ of a section is the value of the section at x.
The evaluation at x is surjective: every value is taken by a constant section.