Screwon spectral statistics and dispersion relation in the quantum Rajeev-Ranken model

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Main Authors: Krishnaswami, Govind S., Vishnu, T. R.
Format: Preprint
Published: 2023
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author Krishnaswami, Govind S.
Vishnu, T. R.
author_facet Krishnaswami, Govind S.
Vishnu, T. R.
contents The Rajeev-Ranken (RR) model is a Hamiltonian system describing screw-type nonlinear waves (screwons) of wavenumber $k$ in a scalar field theory pseudodual to the 1+1D SU(2) principal chiral model. Classically, the RR model based on a quadratic Hamiltonian on a nilpotent/Euclidean Poisson algebra is Liouville integrable. Upon adopting canonical variables in a slightly extended phase space, the model was interpreted as a novel 3D cylindrically symmetric quartic oscillator with a rotational energy. Here, we examine the spectral statistics and dispersion relation of quantized screwons via numerical diagonalization validated by variational and perturbative approximations. We also derive a semiclassical estimate for the cumulative level distribution which compares favorably with the one from numerical diagonalization. The spectrum shows level crossings typical of an integrable system. The $i^{\rm th}$ unfolded nearest neighbor spacings are found to follow Poisson statistics for small $i$. Nonoverlapping spacing ratios also indicate that successive spectral gaps are independently distributed. After displaying universal linear behavior over energy windows of short lengths, the spectral rigidity saturates at a length and value that scales with the square-root of energy. For strong coupling $λ$ and intermediate $k$, we argue that reduced screwon energies can depend only on the product $λk$. Numerically, we find power law dependences on $λ$ and $k$ with an approximately common exponent $2/3$ provided the angular momentum quantum number $l$ is small compared to the number of nodes $n$ in the radial wavefunction. On the other hand, for the ground state $n = l = 0$, the common exponent becomes 1.
format Preprint
id arxiv_https___arxiv_org_abs_2312_13122
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Screwon spectral statistics and dispersion relation in the quantum Rajeev-Ranken model
Krishnaswami, Govind S.
Vishnu, T. R.
Exactly Solvable and Integrable Systems
High Energy Physics - Theory
Mathematical Physics
The Rajeev-Ranken (RR) model is a Hamiltonian system describing screw-type nonlinear waves (screwons) of wavenumber $k$ in a scalar field theory pseudodual to the 1+1D SU(2) principal chiral model. Classically, the RR model based on a quadratic Hamiltonian on a nilpotent/Euclidean Poisson algebra is Liouville integrable. Upon adopting canonical variables in a slightly extended phase space, the model was interpreted as a novel 3D cylindrically symmetric quartic oscillator with a rotational energy. Here, we examine the spectral statistics and dispersion relation of quantized screwons via numerical diagonalization validated by variational and perturbative approximations. We also derive a semiclassical estimate for the cumulative level distribution which compares favorably with the one from numerical diagonalization. The spectrum shows level crossings typical of an integrable system. The $i^{\rm th}$ unfolded nearest neighbor spacings are found to follow Poisson statistics for small $i$. Nonoverlapping spacing ratios also indicate that successive spectral gaps are independently distributed. After displaying universal linear behavior over energy windows of short lengths, the spectral rigidity saturates at a length and value that scales with the square-root of energy. For strong coupling $λ$ and intermediate $k$, we argue that reduced screwon energies can depend only on the product $λk$. Numerically, we find power law dependences on $λ$ and $k$ with an approximately common exponent $2/3$ provided the angular momentum quantum number $l$ is small compared to the number of nodes $n$ in the radial wavefunction. On the other hand, for the ground state $n = l = 0$, the common exponent becomes 1.
title Screwon spectral statistics and dispersion relation in the quantum Rajeev-Ranken model
topic Exactly Solvable and Integrable Systems
High Energy Physics - Theory
Mathematical Physics
url https://arxiv.org/abs/2312.13122