arXiv subjects

Shih-Yen Tseng

Publications and source records attributed to Shih-Yen Tseng.

8 recordsLinked to original sources

arXiv2026

Fixing Divergence in Carleman Linearization via Analytical Continuation

Nonlinear differential equations play a crucial role in modeling a wide range of phenomena, yet their solutions remain notoriously difficult to obtain. With the rapid development of quantum computing, quantum algorithms for efficiently solving such equations are actively being explored. One promising approach is based on Carleman linearization, which transforms nonlinear differential equations into linear systems. However, this method suffers from exponential divergence beyond a certain time scale. By reformulating the solutions in terms of eigenvalues and eigenvectors, we identify that this divergence originates from the Laurent expansion outside its neighborhood of convergence. To address this issue, we insert a regularized function to the divergent solution hinted by analytical continuation. We validate this divergence-correction method on both the logistic equation and some other partial differential equations like KPP-Fisher equations and Phase-Field models under periodic conditions. We implement our method for the logistic equation using the Linear Combination of Unitaries (LCU) quantum algorithm, providing a detailed complexity and error analysis.

quant-ph↗

arXiv2025

Enhancing Accuracy of Quantum-Selected Configuration Interaction Calculations using Multireference Perturbation Theory: Application to Aromatic Molecules

Quantum-selected configuration interaction (QSCI) is a novel quantum-classical hybrid algorithm for quantum chemistry calculations. This method identifies electron configurations having large weights for the target state using quantum devices and allows CI calculations to be performed with the selected configurations on classical computers. In principle, the QSCI algorithm can take advantage of the ability to handle large configuration spaces while reducing the negative effects of noise on the calculated values. At present, QSCI calculations are limited by qubit noise during the input state preparation and measurement process, restricting them to small active spaces. These limitations make it difficult to perform calculations with quantitative accuracy. The present study demonstrates a computational scheme based on multireference perturbation theory calculations on a classical computer, using the QSCI wavefunction as a reference. This method was applied to ground and excited state calculations for two typical aromatic molecules, naphthalene and tetracene. The incorporation of the perturbation treatment was found to provide improved accuracy. Extension of the reference space based on the QSCI-selected configurations as a means of further improvement was also investigated.

physics.chem-ph↗

arXiv2023

Probing New Physics in the Vector-like Lepton Model by Lepton Electric Dipole Moments

We examine the lepton dipole moments in an extension of the Standard Model (SM), which contains vector-like leptons that couple only to the second-generation SM leptons. The model naturally leads to sizable contributions to the muon $g-2$ and the muon electric dipole moment (EDM). One feature of this model is that a sizable electron EDM is also induced at the two-loop level due to the existence of new vector-like leptons in the loops. We find parameter regions that can explain the muon $g-2$ anomaly and are also consistent with the experimental constraints coming from the electron EDM and the Higgs decay $h\rightarrow μ^{+}μ^{-}$. The generated EDMs can be as large as $O(10^{-22})~e \cdot \mathrm{cm}$ for the muon and $O(10^{-30})~e \cdot \mathrm{cm}$ for the electron, respectively, which can be probed in future experiments for the EDM measurements.

hep-ph↗

arXiv2022

Probing the $L_μ$-$L_τ$ Gauge Boson at the MUonE Experiment

We discuss the prospects of probing the $L_μ- L_τ$ gauge boson at the MUonE experiment. The $L_μ- L_τ$ gauge boson $Z^\prime$ with a mass of $\lesssim 200$ MeV, which can explain the discrepancy between the measured value of the muon $g-2$ and the value calculated in the Standard Model, can be produced at the MUonE experiment through the process $μe \to μe Z^\prime$. The $Z^\prime$ in the final state decays into a pair of neutrinos, and therefore we cannot observe the decay of $Z^\prime$ directly. It is, however, still possible to probe this signature by searching for events with a large scattering angle of muon and a less energetic final-state electron. The background events coming from the elastic scattering $μe \to μe$ as well as radiative process $μe \to μe γ$ can be removed by the kinematical cuts on the muon scattering angle and the electron energy, in addition to a photon veto. The background events from the electroweak process $μe \to μe ν\barν$ are negligible. With our selection criteria, the number of signal events $μe \to μe Z^\prime$ is found to be as large as $\sim 10^3$ in the parameter region motivated by the muon $g-2$ discrepancy. It is, therefore, quite feasible to probe the $L_μ- L_τ$ gauge boson at the MUonE experiment -- without introducing additional devices -- and we strongly recommend recording the events relevant to this $Z^\prime$ production process.

hep-ph↗

arXiv2021

Explaining the MiniBooNE Anomalous Excess via Leptophilic ALP-Sterile Neutrino Coupling

Recently, the MiniBooNE experiment at Fermilab has updated the results with increased data and reported an excess of $560.6 \pm 119.6$ electronlike events ($4.7σ$) in the neutrino operation mode. In this paper, we propose a scenario to account for the excess where a Dirac-type sterile neutrino, produced by a charged kaon decay through the neutrino mixing, decays into a leptophilic axionlike particle ($\ell$ALP) and a muon neutrino. The electron-positron pairs produced from the $\ell$ALP decays can be interpreted as electronlike events provided that their opening angle is sufficiently small. In our framework, we consider the $\ell$ALP with a mass $m^{}_a = 20\,\text{MeV}$ and an inverse decay constant $c^{}_e/f^{}_a = 10^{-2}\,\text{GeV}^{-1}$, allowed by the astrophysical and experimental constraints. Then, after integrating the predicted angular or visible energy spectra of the $\ell$ALP to obtain the total excess event number, we find that our scenario with sterile neutrino masses within $150\,\text{MeV}\lesssim m^{}_N \lesssim 380 \,\text{MeV}$ ($150\,\text{MeV}\lesssim m^{}_N \lesssim 180 \,\text{MeV}$) and neutrino mixing parameters between $10^{-10} \lesssim |U_{μ4}|^2 \lesssim 10^{-8}$ ($3\times 10^{-7} \lesssim |U_{μ4}|^2 \lesssim 8 \times10^{-7}$) can explain the MiniBooNE data.

hep-ph↗

arXiv2021

Alternative Minimal U(1)$_{\rm B-L}$

We provide a minimal alternative gauged U(1)$_{\rm B-L}$ model in which three right-handed neutrinos with charges of (5,-4,-4) and only one B-L Higgs field with charge 1 are introduced. Consistent active neutrino masses and mixings can be obtained if the $Z_2$ symmetry on two of the right-handed neutrinos is introduced. It predicts two heavy degenerate right-handed neutrinos, which may realize resonant leptogenesis scenario, and one relatively light sterile neutrino, which is a good dark matter candidate.

hep-ph↗

arXiv2020

Leptogenesis in the minimal gauged U(1)$_{L_μ-L_τ}$ model and the sign of the cosmological baryon asymmetry

The minimal gauged U(1)$_{L_μ-L_τ}$ model is a simple extension of the Standard Model and has a strong predictive power for the neutrino sector. In particular, the mass spectrum and couplings of heavy right-handed neutrinos are determined as functions of three neutrino Dirac Yukawa couplings, with which we can evaluate the baryon asymmetry of the Universe generated through their decay, i.e., leptogenesis. In this letter, we study leptogenesis in the minimal gauged U(1)$_{L_μ-L_τ}$ model. It turns out that the sign of the resultant baryon asymmetry for the case with the Dirac CP phase, $δ$, larger than $π$ is predicted to be opposite to that for $δ< π$. In addition, if lepton asymmetry is dominantly produced by the decay of the lightest right-handed neutrino, then the correct sign of baryon asymmetry is obtained for $δ> π$, which is favored by the current neutrino-oscillation experiments, whilst the wrong sign is obtained for $δ< π$. We further investigate a non-thermal leptogenesis scenario where the U(1)$_{L_μ-L_τ}$ breaking field plays the role of inflaton and decays into right-handed neutrinos, as a concrete example. It is found that this simple framework offers a successful inflation that is consistent with the CMB observation. We then show that the observed amount of baryon asymmetry can be reproduced in this scenario, with its sign predicted to be positive in most of the parameter space.

hep-ph↗

arXiv2019

Minimal Gauged U(1)$_{L_α- L_β}$ Models Driven into a Corner

It is well known that the differences between the lepton numbers can be gauged with the Standard Model matter content. Such extended gauge theories, dubbed as the gauged U(1)$_{L_α- L_β}$ models, have been widely discussed so far as potential candidates for physics beyond the Standard Model. In this work, we study the minimal versions of these gauge theories, where three right-handed neutrinos as well as a single U(1)$_{L_α- L_β}$ symmetry breaking Higgs field---an SU(2)$_L$ singlet or doublet---are introduced. In these minimal models, the neutrino mass terms are constrained by the gauge symmetry, which result in the two-zero texture or two-zero minor structure of neutrino mass matrices. Such restrictive forms of neutrino mass matrices lead to non-trivial predictions for the neutrino oscillation parameters as well as the size of the mass eigenvalues. We find that due to this restriction the minimal gauged U(1)$_{L_α- L_β}$ models are either incompatible with the observed values of the neutrino parameters or in strong tension with the Planck 2018 limit on the sum of the neutrino masses. Only the U(1)$_{L_μ-L_τ}$ model with an SU(2)$_L$ singlet U(1)$_{L_μ-L_τ}$-breaking field barely evades the limit, which can be tested in the future neutrino experiments.

hep-ph↗