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Hamiltonian Flow Equations in Daubechies Wavelet Basis (2501.13618v1)

Published 23 Jan 2025 in hep-th and hep-lat

Abstract: We study the low energy dynamics of a system of two coupled real scalar fields in 1+1 dimensions using the flow equation approach of Similarity Renormalization Group (SRG) in a wavelet basis. This paper presents an extension of the work by Michlin and Polyzou \cite{PhysRevD.95.094501} at one resolution higher. We also present the analysis of a model of two scalar fields coupled through a generally quadratic interaction in $1+1$ dimensions using wavelet-based flow equations. We demonstrate that the specifically chosen generator flows the Hamiltonian into a block diagonal form with each diagonal block being associated with a fixed resolution. The wavelet basis is known to transform the scalar field theory into a model of coupled localized oscillators, each of which is labelled by location and resolution indices. The chosen interaction represents the coupling between two types of oscillators at the same location and resolution index. There is no coupling between oscillators across locations and resolutions. We show that wavelet-based flow equations carry out scale separation while maintaining the interactions between the two scalar fields at each resolution. The effective Hamiltonian associated with the coarsest resolution is shown to correctly reproduce the normal mode frequencies of the model.

Summary

  • The paper introduces a novel application of Hamiltonian flow equations in the Daubechies wavelet basis to systematically decouple multi-resolution scalar field interactions.
  • The methodology transforms continuous fields into discrete, localized oscillators, enabling a non-perturbative block diagonalization of the Hamiltonian.
  • Numerical results reveal an error reduction from 2% to 0.0016% with increased resolution, confirming high-fidelity reproduction of exact field theory outcomes.

An Analytical Overview of "Hamiltonian Flow Equations in Daubechies Wavelet Basis"

The field of quantum field theories (QFTs) presents a myriad of complex challenges, especially when it comes to analyzing interactions at various scales using non-perturbative methods. The paper entitled "Hamiltonian Flow Equations in Daubechies Wavelet Basis" extends the utility of the wavelet basis, particularly the Daubechies wavelet family, to dissect the dynamics of coupled scalar fields through the prism of the Similarity Renormalization Group (SRG). This work builds upon precedents set by Michlin and Polyzou in wavelet-based QFTs, adding specificity through higher resolutions and considering scalar interactions beyond free theories.

Theoretical Framework and Methodology

The authors develop a framework that applies flow equation approaches to the Hamiltonian of a system represented in the Daubechies wavelet basis. Using this basis, fields originally defined in a continuous space are represented as localized oscillators, facilitating a scale-by-scale analysis. The principal advantage of Daubechies wavelets lies in their compact support and orthonormality, allowing for a precise scale separation. Here, the fields are transformed into discrete variables associated with specific scales and locations. The authors implement a Hamiltonian flow equation approach, which allows continual evolution of the system, subsequently guiding the Hamiltonian to a block diagonal form where each diagonal component corresponds to a fixed resolution.

A significant methodological step is the choice of the Hamiltonian flow generator. The selected generator ensures interactions between scalar fields at each resolution while segregating degrees of freedom at different resolutions. This approach facilitates non-perturbative analysis, aligning with objectives from historically pivotal work by Wilson in QCD, but with renewed scrutiny through wavelets.

Key Numerical Findings and Claims

The authors present evidence that the effective Hamiltonian at the most granular resolution reproduces normal mode frequencies accurately, as demonstrated by scaling fields representation truncated to resolution levels k=0, k=1, and up to k=10. Notably, the truncated Hamiltonian aligns increasingly with exact field theory results as the resolution increases, with an error reduction from approximately 2% to 0.0016% for the lowest eigenvalues when considering higher resolutions. This confirmation of fidelity validates the technique's effectiveness in reconciling multi-resolution data in QFTs without ignoring significant fine-resolution effects.

Further, the analysis extends to coupled-field theories addressed with a unique perspective on Hamiltonian decoupling in the context of field-field interactions. Here, the paper demonstrates that the intra-scale couplings dominate as inter-scale couplings diminish with the flow, effectively capturing the contributions of all scales at the coarsest level.

Implications and Future Directions

The implications of adopting Daubechies wavelet basis in QFT are manifold, offering a robust groundwork for both computational advancements and theoretical innovations in the examination of strong coupling regimes. Given the accurate portrayal of multi-scale dynamics captured in this approach, there is potential for profound impacts in the paper of quantum chromodynamics (QCD) and similar fields. The disentanglement of scales facilitated through wavelets aligns with natural truncation strategies and renders computational handling feasible for challenging regimes.

Future investigations can capitalize on these insights by extending Daubechies wavelet applications to incorporate system-specific demands such as external field interactions or non-linear coupling effects. Moreover, additional explorations involving path integral formulations and potential re-imagination of light-front QFT consistently with wavelet analysis can expand this pivotal groundwork's potential.

In conclusion, this paper affirms the efficacy of deploying a novel blend of wavelet analysis and flow equation methods to refine our understanding and manipulation of quantum fields. Through comprehensive multi-resolution decoupling and effective Hamiltonian realization, the authors set a new standard for tackling the composite nature of field interactions beyond perturbative confines.

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