Sachs Equations and Plane Waves, V: Ward, Fourier, and Heisenberg Symmetry on Plane Waves

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Hauptverfasser: Holland, Jonathan, Sparling, George
Format: Preprint
Veröffentlicht: 2026
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author Holland, Jonathan
Sparling, George
author_facet Holland, Jonathan
Sparling, George
contents This article studies wave equations and their solutions on plane wave spacetimes of arbitrary dimension, developing the interplay among three structural layers: the Ward progressing-wave representation of solutions to the scalar wave equation, the Fourier analysis of the Heisenberg group naturally associated to the plane wave, and the Schrödinger propagator governing the evolution of initial data. The central geometric object is a positive curve in the Lagrangian Grassmannian determined by the plane wave metric, previously studied in the authors' series. The conformal tensor $H(u)$ that parametrises this curve plays a dual role: it encodes the null-cone geometry of the spacetime and simultaneously appears as the time-dependent parameter in the Schrödinger representation of the Heisenberg group acting by isometries on the plane wave. Parallel to the classical Fourier inversion theorem, convolution by Lagrangian delta distributions on the Heisenberg group furnishes an intrinsic description of the Schrödinger propagator, and the intertwining of different polarisations by this propagator is captured by a diagram that commutes up to a Maslov phase. The theta functions and Bargmann transforms that arise from imaginary polarisations complete the analytic picture, connecting the present work to the theory of the Weil representation as developed by Lion--Vergne and to Mumford's systematic treatment of theta functions.
format Preprint
id arxiv_https___arxiv_org_abs_2603_28206
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Sachs Equations and Plane Waves, V: Ward, Fourier, and Heisenberg Symmetry on Plane Waves
Holland, Jonathan
Sparling, George
General Relativity and Quantum Cosmology
Mathematical Physics
83C35
This article studies wave equations and their solutions on plane wave spacetimes of arbitrary dimension, developing the interplay among three structural layers: the Ward progressing-wave representation of solutions to the scalar wave equation, the Fourier analysis of the Heisenberg group naturally associated to the plane wave, and the Schrödinger propagator governing the evolution of initial data. The central geometric object is a positive curve in the Lagrangian Grassmannian determined by the plane wave metric, previously studied in the authors' series. The conformal tensor $H(u)$ that parametrises this curve plays a dual role: it encodes the null-cone geometry of the spacetime and simultaneously appears as the time-dependent parameter in the Schrödinger representation of the Heisenberg group acting by isometries on the plane wave. Parallel to the classical Fourier inversion theorem, convolution by Lagrangian delta distributions on the Heisenberg group furnishes an intrinsic description of the Schrödinger propagator, and the intertwining of different polarisations by this propagator is captured by a diagram that commutes up to a Maslov phase. The theta functions and Bargmann transforms that arise from imaginary polarisations complete the analytic picture, connecting the present work to the theory of the Weil representation as developed by Lion--Vergne and to Mumford's systematic treatment of theta functions.
title Sachs Equations and Plane Waves, V: Ward, Fourier, and Heisenberg Symmetry on Plane Waves
topic General Relativity and Quantum Cosmology
Mathematical Physics
83C35
url https://arxiv.org/abs/2603.28206