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Article

A Geometry of Hamiltonian Mechanics

by
Gil Elgressy
1,* and
Lawrence Horwitz
1,2,3,*
1
Department of Physics, Bar Ilan University, Ramat Gan 52900, Israel
2
School of Physics, Tel Aviv University, Ramat Aviv 69978, Israel
3
Department of Physics, Ariel University, Ariel 44837, Israel
*
Authors to whom correspondence should be addressed.
Entropy 2026, 28(4), 379; https://doi.org/10.3390/e28040379
Submission received: 26 December 2025 / Revised: 20 March 2026 / Accepted: 22 March 2026 / Published: 27 March 2026
(This article belongs to the Special Issue Hamiltonian Dynamics in Fundamental Physics)

Abstract

We develop a local, patchwise geometric framework that embeds a broad class of potential Hamiltonian dynamical systems into a family of Riemannian Hamilton patches built over an underlying Gutzwiller manifold. We adopt a conformal (Jacobi) ansatz and a frame-adapted reconstruction procedure, through which we construct, on each patch, a pulled-back metric, along with a reduced (truncated) connection (not a metric-compatible connection) and a corresponding dynamical curvature tensor governing geodesic deviation in the Hamilton coordinates. Then, using the Poisson–Hodge reconstruction, we reconstruct coordinate potentials, enforcing harmonic obstructions, and along with exactness and Jacobian nondegeneracy conditions, we obtain explicit elliptic bounds that control the connection and curvature residuals. On the basis of this construction, we formalize the notion of a Hamilton manifold such that reparametrized geodesics approximate Newton trajectories with controlled acceleration and tolerances. As a generalized structural framework, to promote the local Jacobi reconstructions to a coherent dynamical evolution and provide a dynamical closure, we introduce a patchwise hyperbolic geometric flow for the pullback metric coupled to a kinetic (Vlasov) closure that controls reconstruction and curvature residuals. Under natural regularity, ellipticity, and overlap-tolerance assumptions, together with precise estimates that control the reconstruction and curvature errors, we establish short-time well-posedness of the coupled Vlasov–hyperbolic geometric flow that defines the patchwise Hamilton manifold. Motivated by this construction of the Hamilton manifold with atlas-dependent time, we propose convergence and stability conjectures for dissipative and conservative (non-dissipative) hyperbolic geometric flows. On a single patch, these conjectures characterize local orbital stability (in the sense of coercivity modulo symmetry) and identify local linear instability when unstable linear modes are present. On a finite atlas (the Hamilton manifold with atlas-dependent time), we state conjectures under which local stability propagates to global stability, provided that overlap residuals remain uniformly sufficiently small. The framework identifies the geometric origin of local instability diagnostics used in Hamiltonian mechanics and outlines a practical strategy for verifying stability or instability, numerically or analytically, on finite coverings of configuration space (the Hamilton manifold).
Keywords: Jacobi metric; Hamilton manifold; Gutzwiller manifold; hyperbolic geometric flow; geodesic deviation; dynamical curvature; anholonomic frames; Vlasov closure; Hamiltonian stability; geometric mechanics Jacobi metric; Hamilton manifold; Gutzwiller manifold; hyperbolic geometric flow; geodesic deviation; dynamical curvature; anholonomic frames; Vlasov closure; Hamiltonian stability; geometric mechanics

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MDPI and ACS Style

Elgressy, G.; Horwitz, L. A Geometry of Hamiltonian Mechanics. Entropy 2026, 28, 379. https://doi.org/10.3390/e28040379

AMA Style

Elgressy G, Horwitz L. A Geometry of Hamiltonian Mechanics. Entropy. 2026; 28(4):379. https://doi.org/10.3390/e28040379

Chicago/Turabian Style

Elgressy, Gil, and Lawrence Horwitz. 2026. "A Geometry of Hamiltonian Mechanics" Entropy 28, no. 4: 379. https://doi.org/10.3390/e28040379

APA Style

Elgressy, G., & Horwitz, L. (2026). A Geometry of Hamiltonian Mechanics. Entropy, 28(4), 379. https://doi.org/10.3390/e28040379

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