Formal multilinear series #
In this file we define FormalMultilinearSeries 𝕜 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 contDiff
in mathlib
) and analytic functions.
Notations #
We use the notation E [×n]→L[𝕜] 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 𝕜
, from E
to F
, is given by a family of
multilinear maps from E^n
to F
for all n
.
Equations
- FormalMultilinearSeries 𝕜 E F = ((n : ℕ) → ContinuousMultilinearMap 𝕜 (fun (i : Fin n) => E) F)
Instances For
Equations
- instAddCommGroupFormalMultilinearSeries = inferInstanceAs (AddCommGroup ((n : ℕ) → ContinuousMultilinearMap 𝕜 (fun (i : Fin n) => E) F))
Equations
- instInhabitedFormalMultilinearSeries = { default := 0 }
Equations
- instModuleFormalMultilinearSeriesToAddCommMonoidInstAddCommGroupFormalMultilinearSeries 𝕜' = inferInstanceAs (Module 𝕜' ((n : ℕ) → ContinuousMultilinearMap 𝕜 (fun (i : Fin n) => E) F))
Cartesian product of two formal multilinear series (with the same field 𝕜
and the same source
space, but possibly different target spaces).
Equations
- FormalMultilinearSeries.prod p q x = let n := x; ContinuousMultilinearMap.prod (p n) (q n)
Instances For
Killing the zeroth coefficient in a formal multilinear series
Equations
- FormalMultilinearSeries.removeZero p x = match x with | 0 => 0 | Nat.succ n => p (n + 1)
Instances For
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 pₙ
in a formal multilinear series with (u, ..., u)
where u
is a fixed
continuous linear map, gives a new formal multilinear series p.compContinuousLinearMap u
.
Equations
- FormalMultilinearSeries.compContinuousLinearMap p u n = ContinuousMultilinearMap.compContinuousLinearMap (p n) fun (x : Fin n) => u
Instances For
Reinterpret a formal 𝕜'
-multilinear series as a formal 𝕜
-multilinear series.
Equations
Instances For
Forgetting the zeroth term in a formal multilinear series, and interpreting the following terms
as multilinear maps into E →L[𝕜] F
. If p
is the Taylor series (HasFTaylorSeriesUpTo
) of a
function, then p.shift
is the Taylor series of the derivative of the function. Note that the
p.sum
of a Taylor series p
does not give the original function; for a formal multilinear
series that sums to the derivative of p.sum
, see HasFPowerSeriesOnBall.fderiv
.
Equations
Instances For
Adding a zeroth term to a formal multilinear series taking values in E →L[𝕜] F
. This
corresponds to starting from a Taylor series (HasFTaylorSeriesUpTo
) for the derivative of a
function, and building a Taylor series for the function itself.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Composing each term pₙ
in a formal multilinear series with a continuous linear map f
on the
left gives a new formal multilinear series f.compFormalMultilinearSeries p
whose general term
is f ∘ pₙ
.
Equations
Instances For
Realize a ContinuousMultilinearMap on ∀ i : ι, E i
as the evaluation of a
FormalMultilinearSeries by choosing an arbitrary identification ι ≃ Fin (Fintype.card ι)
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
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
- FormalMultilinearSeries.order p = sInf {n : ℕ | p n ≠ 0}
Instances For
The n
th coefficient of p
when seen as a power series.
Equations
- FormalMultilinearSeries.coeff p n = (p n) 1
Instances For
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.
Equations
- FormalMultilinearSeries.fslope p n = (ContinuousMultilinearMap.curryLeft (p (n + 1))) 1
Instances For
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
- constFormalMultilinearSeries 𝕜 E c x = match x with | 0 => ContinuousMultilinearMap.curry0 𝕜 E c | x => 0
Instances For
Formal power series of a continuous linear map f : E →L[𝕜] F
at x : E
:
f y = f x + f (y - x)
.
Equations
- One or more equations did not get rendered due to their size.