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1 change: 1 addition & 0 deletions Physlib.lean
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Expand Up @@ -164,6 +164,7 @@ public import Physlib.Particles.SuperSymmetry.MSSMNu.AnomalyCancellation.OrthogY
public import Physlib.Particles.SuperSymmetry.MSSMNu.AnomalyCancellation.OrthogY3B3.ToSols
public import Physlib.Particles.SuperSymmetry.MSSMNu.AnomalyCancellation.Permutations
public import Physlib.Particles.SuperSymmetry.MSSMNu.AnomalyCancellation.Y3
public import Physlib.Particles.SuperSymmetry.N1.Basic
public import Physlib.Particles.SuperSymmetry.SU5.ChargeSpectrum.AllowsTerm
public import Physlib.Particles.SuperSymmetry.SU5.ChargeSpectrum.Basic
public import Physlib.Particles.SuperSymmetry.SU5.ChargeSpectrum.Completions
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88 changes: 88 additions & 0 deletions Physlib/Particles/SuperSymmetry/N1/Basic.lean
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/-
Copyright (c) 2026 Andrea Pari. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Andrea Pari
-/
module

public import Mathlib.Data.Fintype.Defs
public import Mathlib.Analysis.Complex.Basic
public import Mathlib.Logic.Equiv.Basic

/-!

# SUSY N=1 chiral sector — basic indexing data

## i. Overview

The minimal label and configuration data for the N=1 chiral sector.

A `Model` packages two finite index types — `ChiralIndexingType` (written `C`
below) indexing the chiral scalars and `AntiChiralIndexingType` (written `A`)
the anti-chiral (barred) slots — with an equivalence `equiv : C ≃ A`, kept
distinct so the two slots of a contraction `g_{IJ̄}` cannot be confused. The
physical configuration is `ChiralScalarConfiguration C = C → ℂ`, carrying
`2 · Fintype.card C` real degrees of freedom — the only field data; the
anti-chiral scalars are its complex conjugates, never an independent
configuration.

Doubling — adding an independent `A → ℂ` configuration — is the wrong choice:
the physical identities would then hold only where anti-chiral is the conjugate
of chiral, so every theorem carries that subspace as a hypothesis (e.g. the
Kähler potential is real only there, making hermiticity of `g_{IJ̄}`
conditional). Building the conjugate in keeps them unconditional — `K` is real
by construction — and leaves `A` an index type only.

This file carries only the index/configuration data; the chiral and anti-chiral
derivatives `∂_I` / `∂_J̄` (the `Model` methods `M.dChiralScalar` /
`M.dAntiChiralScalar`) are built on top of it in `Derivative.lean`.

The files of this `Particles/SuperSymmetry/N1/` folder:

* `Basic.lean` (this file) — the `Model` indexing data and the chiral
configuration type.
* `Derivative.lean` — the chiral / anti-chiral derivative wrappers
`M.dChiralScalar` / `M.dAntiChiralScalar` over the Wirtinger calculus.
* `SuperPotential.lean` — the abstract holomorphic superpotential `W` and its
conjugate `W̄`.
* `KahlerPotential.lean` — the abstract Kähler potential `K`.
* `KahlerMetric.lean` — the Kähler metric `g_{IJ̄} = ∂_I ∂_J̄ K` and its
hermiticity.
* `LogKahlerHn.lean` — worked example: the `Hⁿ` log Kähler potential (the
reusable upper-half-plane calculus lives in
`Mathematics/Calculus/Wirtinger/UpperHalfPlane.lean`).

## ii. Key results

- `SUSY.N1.Model` : the indexing data of an N=1 sector — a chiral index type,
an anti-chiral (barred) index type, and an equivalence `equiv` between them.
- `SUSY.N1.ChiralScalarConfiguration` : the physical scalar configuration space
`C → ℂ`, where `C` is the finite type indexing the chiral scalars — the only
field data in the sector.

-/

@[expose] public section

noncomputable section

namespace SUSY.N1

/-- The indexing data of an N=1 sector: a chiral index type `ChiralIndexingType`,
an anti-chiral (barred) index type `AntiChiralIndexingType`, and a bijection
`equiv` between them. -/
structure Model (ChiralIndexingType : Type*) [Fintype ChiralIndexingType]
(AntiChiralIndexingType : Type*) [Fintype AntiChiralIndexingType] where
/-- The correspondence between chiral and anti-chiral (barred) labels. -/
equiv : ChiralIndexingType ≃ AntiChiralIndexingType

/-- The chiral scalar configuration: an assignment of complex values to each
chiral label. An `abbrev` so unification applies Mathlib's `α → ℂ` calculus
lemmas directly. -/
abbrev ChiralScalarConfiguration (ChiralIndexingType : Type*) := ChiralIndexingType → ℂ

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I would change this to the following. It means you end up carrying around 'unused' variables, but I think it will help with the overall consistency.


namespace Model 

set_option linter.unusedVariables false in
/-- The chiral scalar configuration: an assignment of complex values to each
chiral label. An `abbrev` so unification applies Mathlib's `α → ℂ` calculus
lemmas directly. -/
@[nolint unusedArguments]
abbrev ChiralScalarConfiguration {ChiralIndexingType} (M : Model ChiralIndexingType) := ChiralIndexingType → ℂ

end Model

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Thanks for the suggestion. I tried but it did not turn out easy to do.

ChiralScalarConfiguration is really just C → ℂ, so it only depends on the index type, not on a whole Model. Making it a Model method means the KahlerPotential/SuperPotential structures have to carry a model term they never use, and for concrete examples Lean then can't infer the index type on its own.

The concrete example is in the larger PR:

def K : KahlerPotential C -- current
def K : KahlerPotential model -- C hidden in model → Lean can't find it

I think this would be resolved by manual type annotations all over the place to compensate.
It is entirely possible that I am implementing the change naively and there is a cleaner way.

So I'd keep it as it is currently, and use the M. dot-notation for the operations that genuinely use the model (dChiralScalar, dAntiChiralScalar, metric). I am open to suggestions and happy to revisit this.


end SUSY.N1

end

end
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