Formal multilinear series #
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In this file we define formal_multilinear_series π E F
to be a family of n
-multilinear maps for
all n
, designed to model the sequence of derivatives of a function. In other files we use this
notion to define C^n
functions (called cont_diff
in mathlib
) and analytic functions.
Notations #
We use the notation E [Γn]βL[π] F
for the space of continuous multilinear maps on E^n
with
values in F
. This is the space in which the n
-th derivative of a function from E
to F
lives.
Tags #
multilinear, formal series
A formal multilinear series over a field π
, from E
to F
, is given by a family of
multilinear maps from E^n
to F
for all n
.
Equations
- formal_multilinear_series π E F = Ξ (n : β), continuous_multilinear_map π (Ξ» (i : fin n), E) F
Instances for formal_multilinear_series
Equations
Equations
- formal_multilinear_series.module = let _inst : Ξ (n : β), module π (continuous_multilinear_map π (Ξ» (i : fin n), E) F) := Ξ» (n : β), continuous_multilinear_map.module in pi.module β (Ξ» (n : β), continuous_multilinear_map π (Ξ» (i : fin n), E) F) π
Killing the zeroth coefficient in a formal multilinear series
Equations
- p.remove_zero (n + 1) = p (n + 1)
- p.remove_zero 0 = 0
Convenience congruence lemma stating in a dependent setting that, if the arguments to a formal multilinear series are equal, then the values are also equal.
Composing each term pβ
in a formal multilinear series with (u, ..., u)
where u
is a fixed
continuous linear map, gives a new formal multilinear series p.comp_continuous_linear_map u
.
Equations
- p.comp_continuous_linear_map u = Ξ» (n : β), (p n).comp_continuous_linear_map (Ξ» (i : fin n), u)
Reinterpret a formal π'
-multilinear series as a formal π
-multilinear series.
Equations
- formal_multilinear_series.restrict_scalars π p = Ξ» (n : β), continuous_multilinear_map.restrict_scalars π (p n)
Forgetting the zeroth term in a formal multilinear series, and interpreting the following terms
as multilinear maps into E βL[π] F
. If p
corresponds to the Taylor series of a function, then
p.shift
is the Taylor series of the derivative of the function.
Equations
- p.shift = Ξ» (n : β), (p n.succ).curry_right
Adding a zeroth term to a formal multilinear series taking values in E βL[π] F
. This
corresponds to starting from a Taylor series for the derivative of a function, and building a Taylor
series for the function itself.
Equations
- q.unshift z (n + 1) = β(continuous_multilinear_curry_right_equiv' π n E F) (q n)
- q.unshift z 0 = β((continuous_multilinear_curry_fin0 π E F).symm) z
Composing each term pβ
in a formal multilinear series with a continuous linear map f
on the
left gives a new formal multilinear series f.comp_formal_multilinear_series p
whose general term
is f β pβ
.
Equations
- f.comp_formal_multilinear_series p = Ξ» (n : β), f.comp_continuous_multilinear_map (p n)
The index of the first non-zero coefficient in p
(or 0
if all coefficients are zero). This
is the order of the isolated zero of an analytic function f
at a point if p
is the Taylor
series of f
at that point.
Equations
- p.order = has_Inf.Inf {n : β | p n β 0}
The n
th coefficient of p
when seen as a power series.
The formal counterpart of dslope
, corresponding to the expansion of (f z - f 0) / z
. If f
has p
as a power series, then dslope f
has fslope p
as a power series.
The formal multilinear series where all terms of positive degree are equal to zero, and the term
of degree zero is c
. It is the power series expansion of the constant function equal to c
everywhere.
Equations
- const_formal_multilinear_series π E c n.succ = 0
- const_formal_multilinear_series π E c 0 = continuous_multilinear_map.curry0 π E c