Zulip Chat Archive

Stream: Is there code for X?

Topic: Integration by parts for `fderiv`


Tomas Skrivan (Jun 25 2025 at 10:21):

I want a generalization of integration by parts docs#MeasureTheory.integral_bilinear_hasDerivAt_right_eq_neg_left_of_integrable but for fderiv instead.

Something like this (not sure about the exact assumptions on X):

import Mathlib

open MeasureTheory

variable
  {X E F G : Type*}
  [NormedAddCommGroup X] [NormedSpace  X] [FiniteDimensional  X] [MeasurableSpace X]
  [NormedAddCommGroup E] [NormedSpace  E]
  [NormedAddCommGroup F] [NormedSpace  F] [NormedAddCommGroup G] [NormedSpace  G]
  {μ : Measure X} [μ.IsAddHaarMeasure]
  {L : E L[] F L[] G} {u : X  E} {v : X  F} {u' : X  X L[] E} {v' : X  X L[] F}
  {m n : G}

theorem integral_bilinear_hasDerivAt_right_eq_neg_left_of_integrable (dx : X)
    (hu :  x, HasFDerivAt u (u' x) x) (hv :  x, HasFDerivAt v (v' x) x)
    (huv' : Integrable (fun x  L (u x) (v' x dx)) μ) (hu'v : Integrable (fun x  L (u' x dx) (v x)) μ)
    (huv : Integrable (fun x  L (u x) (v x)) μ) :
     (x : X), L (u x) (v' x dx) μ = -  (x : X), L (u' x dx) (v x) μ := sorry

I'm not sure what is the best approach here and I want the result be general enough such that I can have things like X = ℝ × EuclideanSpace (Fin 10) ℝ.

Tomas Skrivan (Jun 25 2025 at 10:29):

Ohh never mind, there is docs#integral_mul_fderiv_eq_neg_fderiv_mul_of_integrable


Last updated: Dec 20 2025 at 21:32 UTC