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[Merged by Bors] - feat(set_theory/surreal/dyadic): define add_monoid_hom structure on dyadic map #11052

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The proof is mechanical and mostly requires unraveling definitions.

The above map cannot be extended to ring morphism as so far there's not multiplication structure on surreal numbers.


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@apurvnakade apurvnakade added the awaiting-review The author would like community review of the PR label Dec 25, 2021
@apurvnakade apurvnakade changed the title feat(set_theory/surreal/dyadic): define add_monoid_hom structure on dyadic map from rational numbers to surreal numbers feat(set_theory/surreal/dyadic): define add_monoid_hom structure on dyadic map Dec 25, 2021
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otherwise lgtm!

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@apurvnakade apurvnakade added WIP Work in progress and removed awaiting-review The author would like community review of the PR labels Jan 4, 2022
@apurvnakade apurvnakade added awaiting-review The author would like community review of the PR and removed WIP Work in progress labels Jan 10, 2022
... = a • pow_half b' + c • pow_half d' : add_comm _ _,
end }

lemma dyadic_map_apply (m : ℤ) (p : submonoid.powers (2 : ℤ)) :
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Should this be a simp lemma?

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Thanks, I added it.

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It needed converting into simp normal form.

@[simp] lemma dyadic_map_apply (m : ℤ) (p : submonoid.powers (2 : ℤ)) :
  dyadic_map (is_localization.mk' (localization (submonoid.powers 2)) m p) =
  m • pow_half (submonoid.log p) 

@@ -234,8 +236,8 @@ lemma pow_right_injective_iff_pow_injective {n : M} :
function.injective (λ m : ℕ, n ^ m) ↔ function.injective (pow n) :=
subtype.coe_injective.of_comp_iff (pow n)

theorem log_pow_eq_self [decidable_eq M] {n : M} (h : function.injective (λ m : ℕ, n ^ m)) (m : ℕ) :
log (pow n m) = m :=
@[simp] theorem log_pow_eq_self [decidable_eq M] {n : M} (h : function.injective (λ m : ℕ, n ^ m))
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Do we have simp lemmas that prove h?

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Otherwise LGTM
bors d+

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h isn't always true though. The closest we have are int.pow_right_injective and nat.pow_right_injective.

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bors bot commented Jan 23, 2022

✌️ apurvnakade can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

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bors r+

bors bot pushed a commit that referenced this pull request Jan 24, 2022
…yadic map (#11052)

The proof is mechanical and mostly requires unraveling definitions.

The above map cannot be extended to ring morphism as so far there's not multiplication structure on surreal numbers.
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bors bot commented Jan 24, 2022

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(set_theory/surreal/dyadic): define add_monoid_hom structure on dyadic map [Merged by Bors] - feat(set_theory/surreal/dyadic): define add_monoid_hom structure on dyadic map Jan 24, 2022
@bors bors bot closed this Jan 24, 2022
@bors bors bot deleted the apurva/surreal-morphism branch January 24, 2022 07:16
@YaelDillies YaelDillies removed the awaiting-review The author would like community review of the PR label Apr 5, 2022
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6 participants