Coefficient maps and coefficient scalars of differential forms #
A continuous real-linear map L : F →L[ℝ] G of coefficient spaces sends an F-valued
differential form to the G-valued form RoughForm.mapCoeff L φ, obtained by applying L to
each value. This preserves regularity, commutes with pullback, and commutes with the exterior
derivative of differentiable forms. On smooth forms it is the real-linear map
SmoothForm.mapCoeff L.
Scalars acting on the coefficients act on smooth forms through the coefficient map given by
multiplication by the scalar. When F is a complex vector space, this makes
SmoothForm I M F k a complex vector space whose complex scalars restrict to its existing real
scalars, as needed for complex-valued forms on complex manifolds, and the exterior derivative
and pullback are complex-linear. The scalar action is defined on underlying forms pointwise,
so for real scalars it agrees with the submodule action on SmoothForm I M F k up to reducible
unfolding of instances. Coefficient conjugation of complex-valued forms is conjugate-linear.
The paired wedge is natural for coefficient maps intertwining two pairings. A pairing that turns multiplication by one scalar into multiplication by another makes the wedge of smooth forms semilinear in the same way; in particular, the wedge for a complex-bilinear pairing of complex coefficient spaces is complex-linear in each form. Coefficient conjugation is multiplicative for the wedge of complex-valued forms given by complex multiplication.
Main declarations #
TauCeti.RoughForm.mapCoeff,TauCeti.SmoothForm.mapCoeff: coefficient maps of forms.TauCeti.IsSmoothForm.mapCoeff: coefficient maps preserve regularity.TauCeti.mextDerivWithin_mapCoeff,TauCeti.mextDeriv_mapCoeff: naturality of the exterior derivative in the coefficient space.TauCeti.mpullbackWithin_mapCoeff,TauCeti.mpullback_mapCoeff: coefficient maps commute with pullback.TauCeti.SmoothForm.instModule: the action of scalars on the coefficients, for instance complex scalars on complex-valued forms, withTauCeti.SmoothForm.smul_toRoughFormandTauCeti.SmoothForm.smul_eq_mapCoeff.TauCeti.SmoothForm.mextDerivₗ_smul,TauCeti.SmoothForm.mpullback_smul: the exterior derivative and pullback are linear for these scalars.TauCeti.SmoothForm.mapCoeff_conj_smul: coefficient conjugation is conjugate-linear.TauCeti.RoughForm.mapCoeff_wedgeWith,TauCeti.SmoothForm.mapCoeff_wedgeWith: naturality of the paired wedge in the coefficients.TauCeti.SmoothForm.wedgeWith_smul_left_of_map_smul,TauCeti.SmoothForm.wedgeWith_smul_right_of_map_smul: the paired wedge is linear, or semilinear, for scalars acting on the coefficients compatibly with the pairing.TauCeti.SmoothForm.mapCoeff_conj_wedgeWith_mul: coefficient conjugation of the wedge of complex-valued forms.
References #
- John M. Lee, Introduction to Smooth Manifolds, 2nd ed., Graduate Texts in Mathematics 218, Springer, 2013, Chapter 14.
Coefficient maps of rough forms #
The form obtained by applying a fixed continuous linear map of coefficient spaces to the values of a form.
Instances For
Scalar multiplication of the coefficients is the coefficient map given by multiplication by the scalar.
A coefficient map that is semilinear for scalars c ↦ d turns multiplication by c into
multiplication by d.
In every chart, the coordinate expression of a coefficient map of a form is the coefficient map of its coordinate expression.
A coefficient map preserves the regularity of a form.
The exterior derivative is natural in the coefficient space, at a point where the coordinate expression of the form is differentiable within the set.
The exterior derivative of a C¹ form is natural in the coefficient space.
Coefficient maps commute with within-set pullback.
Coefficient maps commute with pullback.
Coefficient maps of smooth forms #
A continuous linear map of coefficient spaces, as a linear map on smooth forms.
Instances For
The underlying rough form of a coefficient map of a smooth form.
Coefficient maps of smooth forms commute with transport of the degree.
The exterior derivative of smooth forms is natural in the coefficient space.
Coefficient maps commute with pullback of smooth forms.
Scalars acting on the coefficients #
Scalars acting on the coefficients act on smooth forms pointwise.
The rough form underlying a scalar multiple of a smooth form is the scalar multiple of its rough form.
Evaluating a scalar multiple of a degree-two smooth form scales the evaluation.
Scalar multiplication of a smooth form is the coefficient map given by multiplication by the scalar.
Scalars acting on the coefficients act on smooth forms, making them a module. For complex coefficients this is the complex vector space of complex-valued smooth forms.
When the coefficient scalars restrict to real scalars, so do their actions on smooth forms;
for complex coefficients, RCLike.real_smul_eq_coe_smul then identifies the real action on
smooth forms with the action of real numbers viewed as complex numbers.
A coefficient map that is semilinear for scalars c ↦ d turns multiplication of smooth
forms by c into multiplication by d.
The exterior derivative of smooth forms is linear for scalars acting on the coefficients, such as complex scalars on complex-valued forms.
Pullback of smooth forms is linear for scalars acting on the coefficients.
Complex conjugation of the coefficients of complex-valued smooth forms is conjugate-linear.
Coefficient maps and scalars of wedge products #
The paired rough-form wedge is natural in the coefficients: if coefficient maps L₁, L₂,
L intertwine the pairings μ and μ', then the coefficient map L of the wedge of φ and ψ
is the wedge of their coefficient maps.
The paired wedge of smooth forms is natural in the coefficients: if coefficient maps L₁,
L₂, L intertwine the pairings μ and μ', then the coefficient map L of the wedge of φ
and ψ is the wedge of their coefficient maps.
If the pairing turns multiplication by c in its first argument into multiplication by d,
then so does the paired wedge of smooth forms in its first form. For a complex-bilinear pairing
of complex coefficient spaces this is complex-linearity in the first form; it also covers
pairings that are conjugate-linear in the first argument.
If the pairing turns multiplication by c in its second argument into multiplication by
d, then so does the paired wedge of smooth forms in its second form. For a complex-bilinear
pairing of complex coefficient spaces this is complex-linearity in the second form.
Complex conjugation of the coefficients of complex-valued smooth forms is multiplicative for the wedge product given by complex multiplication.