This paper shows how to use the approximate Hamiltonian approach for the non-conservative system not capable of possessing Hamiltonian. Using the approximate Hamiltonian method for a non-conservative system is not possible in general. We propose a way to obtain the closed-form solutions for such systems. We use the approximate dual Hamiltonian method to construct the first integrals and closed-form solutions of the Van der Pol equation. First the solutions of the initial value VdP equation is obtained using approximate dual Hamiltonian method. Then a good agreement is observed in the comparison between the numerical results and the results through approximate dual Hamiltonian method. Finally, we use the approximate dual Hamiltonian method to find the dual Hamiltonian and first integrals of the forced Van der Pol oscillator and Liénard system. These significant results can be applied to any Van der Pol equation.
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http://dx.doi.org/10.1038/s41598-022-08418-3 | DOI Listing |
Rep Prog Phys
January 2025
SISSA, via Bonomea 265, 34136 Trieste, Trieste, 34136, ITALY.
We review recent progress regarding the double scaled Sachdev-Ye-Kitaev model and other p-local quantum mechanical random Hamiltonians. These models exhibit an expansion using chord diagrams, which can be solved by combinatorial methods. We describe exact results in these models, including their spectrum, correlation functions, and Lyapunov exponent.
View Article and Find Full Text PDFChaos
January 2025
School of Electronic Information, Central South University, Changsha 410083, China.
Memristors are commonly used to introduce various chaotic systems and can be used to enhance their chaotic characteristics. However, due to the strict construction conditions of Hamiltonian systems, there has been limited research on the development of memristive Hamiltonian conservative chaotic systems (MHCCSs). In this work, a method for constructing three-terminal memristors is proposed, and the three-terminal memristors are incorporated into the Hamiltonian system, resulting in the development of a class of n-D MHCCS.
View Article and Find Full Text PDFJ Chem Phys
December 2024
Department of Chemistry, University of the Pacific, Stockton, California 95204, USA.
Utilizing the sparsity of the electronic structure problem, fragmentation methods have been researched for decades with great success, pushing the limits of ab initio quantum chemistry ever further. Recently, this set of methods has been expanded to include a fundamentally different approach called excitonic renormalization, providing promising initial results. It builds a supersystem Hamiltonian in a second-quantized-like representation from transition-density tensors of isolated fragments, contracted with biorthogonalized molecular integrals.
View Article and Find Full Text PDFAlzheimers Dement
December 2024
Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
Background: Plasma tau phosphorylated at threonine 231 (p-tau231) is a promising novel biomarker of emerging Alzheimer's disease (AD) pathology. We aimed to characterize cross-sectional and longitudinal plasma p-tau231 measurements and estimated ages of biomarker onset in an exceptionally large number of presenilin (PSEN1) E280A (Glu280Ala) mutation carriers and age-matched non-carriers from the Colombian autosomal dominant Alzheimer's disease kindred.
Method: We included a cohort of 722 PSEN1 E280A mutation carriers (mean age 36.
J Phys Chem A
January 2025
Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States.
Least-squares tensor hypercontraction (LS-THC) has received some attention in recent years as an approach to reduce the significant computational costs of wave function-based methods in quantum chemistry. However, previous work has demonstrated that LS-THC factorization performs disproportionately worse in the description of wave function components (e.g.
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