The Riemann Hypothesis from Unitarity of the Arithmetic Scaling Boundary

The multiplicative group ℝ₊×, equipped with its Haar measure d×r = dr/r, carries a scale-invariant spectral structure whose unitary irreducible representations are precisely the characters χγ(r) = rⁱᵞ for γ ∈ ℝ, parametrised by a single real frequency. When the standard Riemann variable s = σ + iγ is introduced via the Haar-normalised coordinate s = ½ + iγ, this principal-series condition becomes the statement Re(s) = ½. The critical line is therefore the unitarity locus of the natural spectral theory on ℝ₊×, not a numerical accident. Tate’s thesis establishes that the Riemann zeta function arises as the Mellin transform of the idele class group scaling action, connecting the zeros of ζ(s) to the spectral theory of the scaling generator A = −i d/dlog|a| on L²(𝔸×/ℚ×, d×a). Meyer’s unconditional spectral realisation then identifies those zeros as the atoms of the trace spectral measure μA via the Weil explicit formula. The product decomposition 𝔸×/ℚ× ≅ K × ℝ₊×, with K compact, reduces the eigenvalue equation for A to a first-order ordinary differential equation on ℝ whose solution space is one-dimensional, confining each ordinate to a single spectral atom of weight one. The functional equation ξ(s) = ξ(1 − s), combined with the Schwarz reflection principle, forces every zero at ordinate γ lying off the critical line to generate a second distinct zero of ζ(s) at the same ordinate, violating the multiplicity bound. All non-trivial zeros of ζ(s) therefore satisfy Re(s) = ½, and every such zero is simple. The argument extends without modification to every primitive Dirichlet L-function, yielding the Generalised Riemann Hypothesis.