Ultracold Neutrons in the Low Curvature Limit: Remarks on the post-Newtonian effects

Fuente: arXiv
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Hauptverfasser: Koch, Benjamin, Muñoz, Enrique, Santoni, Alessandro
Format: Preprint
Veröffentlicht: 2023
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author Koch, Benjamin
Muñoz, Enrique
Santoni, Alessandro
author_facet Koch, Benjamin
Muñoz, Enrique
Santoni, Alessandro
contents Ultracold neutrons are great experimental tools to explore the gravitational interaction in the regime of quantized states. From a theoretical perspective, starting from a Dirac equation in curved spacetime, we applied a perturbative scheme to systematically derive the non-relativistic Schrödinger equation that governs the evolution of the neutron's wave function in the Earth's gravitational field. At the lowest order, this procedure reproduces a Schrödinger system affected by a linear Newtonian potential, but corrections due to both curvature and relativistic effects are present. Here, we argue that one should be very careful when going one step further in the perturbative expansion. Proceeding methodically with the help of the Foldy-Wouthuysen transformation and a formal post-Newtonian $c^{-2}-$expansion, we derive the non-relativistic Hamiltonian for a generic static spacetime. By employing Fermi coordinates within this framework, we calculate the next-to-leading order corrections to the neutron's energy spectrum. Finally, we evaluate them for typical experimental configurations, such as that of qBOUNCE, and note that, while the current precision for observations of ultracold neutrons may not yet enable to probe them, they could still be relevant in the future or in alternative circumstances.
format Preprint
id arxiv_https___arxiv_org_abs_2401_00277
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Ultracold Neutrons in the Low Curvature Limit: Remarks on the post-Newtonian effects
Koch, Benjamin
Muñoz, Enrique
Santoni, Alessandro
General Relativity and Quantum Cosmology
Quantum Physics
Ultracold neutrons are great experimental tools to explore the gravitational interaction in the regime of quantized states. From a theoretical perspective, starting from a Dirac equation in curved spacetime, we applied a perturbative scheme to systematically derive the non-relativistic Schrödinger equation that governs the evolution of the neutron's wave function in the Earth's gravitational field. At the lowest order, this procedure reproduces a Schrödinger system affected by a linear Newtonian potential, but corrections due to both curvature and relativistic effects are present. Here, we argue that one should be very careful when going one step further in the perturbative expansion. Proceeding methodically with the help of the Foldy-Wouthuysen transformation and a formal post-Newtonian $c^{-2}-$expansion, we derive the non-relativistic Hamiltonian for a generic static spacetime. By employing Fermi coordinates within this framework, we calculate the next-to-leading order corrections to the neutron's energy spectrum. Finally, we evaluate them for typical experimental configurations, such as that of qBOUNCE, and note that, while the current precision for observations of ultracold neutrons may not yet enable to probe them, they could still be relevant in the future or in alternative circumstances.
title Ultracold Neutrons in the Low Curvature Limit: Remarks on the post-Newtonian effects
topic General Relativity and Quantum Cosmology
Quantum Physics
url https://arxiv.org/abs/2401.00277