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DefinitionDefinition: AI-adaptedProof: AI-generatedPipeline-generatedprecheck passverified 2026-10-22 (gpt-6.1-sol)
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Helicity eigenlines over the direction sphere

Physical scope

Conditional classical Maxwell-Lorentz vacuum model in the smooth source-free nonzero-Fourier-mode regime stated by the supplier. The construction is the direction-sphere geometry of those modes, with no additional approximation. Directions, unit polarization vectors, the helicity sigma, and angular coordinates are dimensionless; the Berry connection and holonomy are dimensionless. There is no quantization, photon position operator, material medium, measurement, or empirical claim.

Definition

For u,v∈C3, extend the real Euclidean dot and right-handed cross products complex-bilinearly, with coordinate formulas u⋅v:=∑j=13ujvj,u×v:=(u2v3−u3v2, u3v1−u1v3, u1v2−u2v1). The dot product in these formulas uses no complex conjugation; it differs from the Hermitian product ⟨u,v⟩H:=∑j=13uj‾vj. Write ∥z∥H:=⟨z,z⟩H for the associated nonnegative norm on C3.

Let S2:={n∈R3:n⋅n=1} with the smooth structure given by the six graph charts solving nj=±1−∑k≠jnk2 on the hemispheres ±nj>0. Orient it outward using the ordered spatial basis x1,x2,x3. Its tangent plane is TnS2={X∈R3:n⋅X=0}. Physically, n=k/∣k∣ for a nonzero spatial wavevector k in the SI Fourier description, where k has units m−1; hence n is dimensionless and the radial magnitude is discarded. For σ∈{+1,−1}, set Cnz:=i n×z, PT(n)z:=z−n(n⋅z), and Pσ(n):=12(PT(n)+σCn) on C3. Define the helicity fibre Lσ(n):=range⁡Pσ(n) and the total space Lσ:={(n,z):n∈S2, z∈Lσ(n)}, projected to S2 by (n,z)↦n.

For an open set U⊆S2, a unit frame of Lσ over U is a smooth map v:U→C3 such that v(n)∈Lσ(n) and ⟨v(n),v(n)⟩H=1 for every n∈U. Since each fibre is a complex line, this vector spans that fibre. A local unit frame is such a map on an open neighborhood in S2; a global unit frame is one defined on all of S2.

Fibrewise addition and scalar multiplication are inherited from C3. A unit frame v gives the local trivialization (n,a)↦(n,av(n)) from U×C to Lσ∣U, with inverse (n,z)↦(n,⟨v(n),z⟩H). The construction in the Proof supplies such a frame near every n, so Lσ is a smooth rank-one complex vector subbundle of the product bundle S2×C3→S2, whose projection is (n,z)↦n.

On a spherical chart with 0<θ<π and a smooth longitude branch ϕ, write n=(sin⁡θcos⁡ϕ,sin⁡θsin⁡ϕ,cos⁡θ), eθ=(cos⁡θcos⁡ϕ,cos⁡θsin⁡ϕ,−sin⁡θ), and eϕ=(−sin⁡ϕ,cos⁡ϕ,0). The local unit helicity frame is vσ:=(eθ+iσeϕ)/2. For any unit frame v over an open set U, write v†dv:=∑j=13vj‾ dvj, where dvj is the exterior derivative of its jth component. Define its Berry connection one-form by A:=iv†dv. A smooth phase change v′=eiχv, with real smooth χ, changes this local form to A′=A−dχ. The local Berry curvature is the real two-form F:=dA on U; no global gluing assertion is made here.

Facts & Assumptions

Given: The oriented unit direction sphere, its standard Hermitian space C3, and one fixed σ∈{+1,−1}.

[F1]

Exact helicity projectors in vacuum defines Cn=in×, PTz=z−n(n⋅z), and Pσ=12(PT+σCn) for unit directions; it proves that Pσ is smooth and is an orthogonal rank-one projection onto the σ helicity eigenspace.

[F2]

Classical transverse Fourier amplitudes defines k as a spatial wavevector with SI units m−1 and uses nonzero k for its transverse Fourier amplitudes; normalizing k gives the dimensionless direction n.

[F3]

Lorentzian Hodge star and periods fixes the ordered coframe dx0,dx1,dx2,dx3 and volume dx0∧dx1∧dx2∧dx3; restricting to the spatial subspace gives the ordered orientation used here.

[F4]

The cross product in R3 fixes the coordinate formula for the right-handed cross product; The Euclidean inner product ⟨x,y⟩=∑k<nxkyk on Rn fixes the real Euclidean dot product and norm.

[F5]

Oriented smooth manifolds and oriented charts defines an orientation as a smoothly chosen orientation ray; the outward normal and fixed spatial orientation specify that ray here.

[F6]

A smooth differential k-form defines smooth k-forms as smooth sections of ⋀kT∗S2; The wedge product of differential forms defines their wedge product pointwise, and The exterior derivative by the invariant vector-field formula defines d.

Proof

1.1F1F2F3F5givenconstruct

The six graph charts in the Definition are smooth coordinate charts on open hemispheres and cover S2; their square-root transition formulas are smooth on overlaps. The outward tangent orientation ray is smooth by the nonvanishing normal n, with ambient spatial orientation fixed in [F3] and orientation-ray convention [F5]. By [F1], each Pσ(n) is a smooth rank-one projection, so each fibre is a complex line. [F2] identifies the physical direction index with a nonzero SI wavevector normalized to unit length. At any n0, choose a fixed w∈C3 with Pσ(n0)w≠0, which exists because the projection has nonzero range. Continuity makes Pσ(n)w≠0 on a neighborhood of n0, and Pσ(n)w/∥Pσ(n)w∥ is a smooth unit local section there. This proves local triviality without choosing a frame family over the whole sphere.

1.2F1F4algebra

The coordinate vectors satisfy n⋅eθ=n⋅eϕ=eθ⋅eϕ=0, ∥eθ∥=∥eϕ∥=1, and n×eθ=eϕ, n×eϕ=−eθ, by the coordinate formulas in [F4]. Hence vσ†vσ=1, PTvσ=vσ, and Cnvσ=σvσ. Substitution gives Pσvσ=vσ, so this is a unit local frame of the stated fibre.

2.1F1F6step 1.1step 1.2algebra

For a smooth section s on a chart, define ∇s:=Pσds. Since Pσs=s, this is again Lσ-valued. For every smooth scalar f, the product rule gives ∇(fs)=Pσ(df s+f ds)=df s+f∇s, so ∇ is a connection on the line bundle. In a unit frame v, writing s=av gives ∇s=(da+av†dv)v=(da−iAa)v because A=iv†dv.

3.1givenF6step 2.1algebra∎

Differentiating ⟨v,v⟩H=1 gives 2Re⁡(∑jvj‾ dvj)=0, so A=i∑jvj‾ dvj is real-valued. Under v′=eiχv, direct differentiation gives v′†dv′=i dχ+v†dv, hence A′=iv′†dv′=A−dχ. This verifies the declared local gauge transformation and completes the definition of the local connection and curvature conventions.

Depends on

Dependency tree · 2 levels

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