Kohei Fujikura, The University of Tokyo
Critical behavior of the Schwinger model via gauge-invariant VUMPS
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
In this talk, I discuss the Hamiltonian formulation of lattice gauge theory using the uniform matrix product state and its application to the single flavor Schwinger model. We perform simulations based on the variational uniform matrix product state (VUMPS) algorithm with a gauge-invariant matrix product ansatz that locally enforces the Gauss law constraint. Both the continuum and lattice versions of the Schwinger model with θ = π are known to exhibit first-order phase transitions for fermion masses above a critical value, at which a second-order phase transition occurs. Our algorithm enables a precise determination of the critical point in the continuum theory.
Niu Wan, South China University of Technology
Variational calculations on multineutron system and nuclear matter with realistic nuclear force
Hybrid On-site: Kenkyu-Honkan 1F, Meeting Room 1 Online: Zoom Recently, resonance-like signals for 4n system were reported in experiment. By confining finite 3n and 4n systems in external potential, we use tensor-optimized antisymmetrized molecular dynamics and inverse analytical continuation in the coupling constant method to study the possibility of the resonances. Consistent results are obtained, however, evident dependence on external attraction is observed. Besides, we also study the infinite nuclear matter with unitary correlation operator method and high-momentum pairs.
Recently, resonance-like signals for 4n system were reported in experiment. By confining finite 3n and 4n systems in external potential, we use tensor-optimized antisymmetrized molecular dynamics and inverse analytical continuation in the coupling constant method to study the possibility of the resonances. Consistent results are obtained, however, evident dependence on external attraction is observed. Besides, we also study the infinite nuclear matter with unitary correlation operator method and high-momentum pairs.
The former is employed to treat the short-range nucleon-nucleon correlation, while the latter is for the tensor correlation. The equations of state for both neutron matter and symmetric nuclear matter are obtained as well as the Hamiltonian components. Calculations by adding hyperons into these systems in the future are also discussed.
References:
[1] Niu Wan, Takayuki Myo, Hiroki Takemoto, Mengjiao Lyu, Qing Zhao, Hisashi Horiuchi, Masahiro Isaka, and Akinobu Dote, under review.
[2] Niu Wan, Takayuki Myo, Hiroki Takemoto, Hiroshi Toki, Chang Xu, Hisashi Horiuchi, Masahiro Isaka, Mengjiao Lyu, and Qing Zhao, Physical Review C 106, 034308 (2022).
[3] Niu Wan, Takayuki Myo, Chang Xu, Hiroshi Toki, Hisashi Horiuchi, and Mengjiao Lyu, Chinese Physics C 44, 124104 (2020).
[4] Takayuki Myo, Hiroki Takemoto, Mengjiao Lyu, Niu Wan, Chang Xu, Hiroshi Toki, Hisashi Horiuchi, Taiichi Yamada, and Kiyomi Ikeda, Physical Review C 99, 024312 (2019).
*Remark:
This seminar is included in KEK Theory Center one-day workshop “Nuclear Physics with Strangeness and Clusters”.
(https://kds.kek.jp/event/53383/)”
Mengjiao Lyu, Nanjing University of Aeronautics and Astronautics
Hypernuclear structure studied with Controlled Neural Network approach
Hybrid On-site: Kenkyu-Honkan 1F, Meeting Room 1 Online: Zoom We investigate the hypernuclear cluster states of Λ9−11Be and Λ12B using the Control Neural Networks (Ctrl.NN) method,which demonstrates rapid convergence in basis state selection compared to traditional GCM calculations. For Λ9−11Be,the numerical results reproduce ground state energies and rotational bands consistent with experiments, revealing a short-range repulsive correlation between the Λ particle and α clusters,leading to a broad Λ distribution termed an “”analog pi-orbit”” structure. For Λ12B, we extend the Ctrl.NN method to calculate the positive-parity spectrum, incorporating sd-shell excitations and parity-coupling effects. Structural changes, including clustering effects and new configurations such as isosceles-triangle and α-t-α linear-chain structures, are revealed. Experimental peaks #6 and #8 are identified as p-Λ dominant states, consistent with shell-model predictions, and candidates for unexplained peaks are proposed. Cluster-shell competition, driven by nuclear forces and Pauli blocking, is found to be critical in Λ12B, where low-lying states exhibit shell-like structures, while clustered states near the α+α+t threshold show broad distributions. The third 3/2− state is identified as an analog Hoyle state, providing a platform to study cluster-breaking effects through binding energy, radius, and γ-transition analyses. These results highlight the interplay between cluster formation, Λ-induced modifications, and unified descriptions of nuclear structure via advanced models like Ctrl.NN.
We investigate the hypernuclear cluster states of Λ9−11Be and Λ12B using the Control Neural Networks (Ctrl.NN) method,which demonstrates rapid convergence in basis state selection compared to traditional GCM calculations. For Λ9−11Be,the numerical results reproduce ground state energies and rotational bands consistent with experiments, revealing a short-range repulsive correlation between the Λ particle and α clusters,leading to a broad Λ distribution termed an “”analog pi-orbit”” structure. For Λ12B, we extend the Ctrl.NN method to calculate the positive-parity spectrum, incorporating sd-shell excitations and parity-coupling effects. Structural changes, including clustering effects and new configurations such as isosceles-triangle and α-t-α linear-chain structures, are revealed. Experimental peaks #6 and #8 are identified as p-Λ dominant states, consistent with shell-model predictions, and candidates for unexplained peaks are proposed. Cluster-shell competition, driven by nuclear forces and Pauli blocking, is found to be critical in Λ12B, where low-lying states exhibit shell-like structures, while clustered states near the α+α+t threshold show broad distributions. The third 3/2− state is identified as an analog Hoyle state, providing a platform to study cluster-breaking effects through binding energy, radius, and γ-transition analyses. These results highlight the interplay between cluster formation, Λ-induced modifications, and unified descriptions of nuclear structure via advanced models like Ctrl.NN.
References:
[1] J. Tian, Z. Cheng, C. Yu, M. Lyu, T. Myo et al., Phys. Lett. B 855,138816 (2024).
[2] Z. Cheng, M. Lyu, T. Myo et al., arXiv:2406.15060.
[3] M. Iodice, F. Cusanno, A. Acha, et al., Phys. Rev. Lett. 99, 052501 (2007).
*Remark:
This seminar is included in KEK Theory Center one-day workshop “Nuclear Physics with Strangeness and Clusters”.
(https://kds.kek.jp/event/53383/)
古城徹, KEK理論センター
[金茶会] From hadrons to quarks in neutron stars
4号館セミナーホール リモート会場：JRB 2階大会議室, 仁科記念棟210室 https://www-conf.kek.jp/kincha/
https://www-conf.kek.jp/kincha/
中性子星は量子色力学の超高密度物質を研究するための天然の実験室系である。中性子星の構造、たとえば質量や半径は、物質の物理的自由度に強く依存している。過去10年間で、中性子星の観測技術が大きく進展し、原子核からくる制約やクォーク物質への理解が深まる中で、中性子星中心部における「ハドロン物質からクォーク物質へのクロスオーバー転移」の可能性が示唆されている。本講演では、ハドロン物理とクォーク物理の包括的考察が中性子星の理解にいかに重要かを議論し、QCD相図への示唆についても触れる。
Zong-Gang Mou, Southampton University
Real-Time Path Integral and Sewed Thimble
Online (Zoom)
The general computation of Quantum Field Theory scales exponentially with the system size. Such exponential scaling has been successfully circumvented in many calculations via Monte Carlo methods. Although Monte Carlo methods will encounter the so-called numerical sign problem in some interesting physics scenarios, due to the presence of highly oscillatory functions. This can be systematically improved by Lefschetz thimble methods, which choose another less oscillatory integration contour in the complex space while keeping the same result according to Cauchy’s integral theorem. In the talk, we would like to show the real-time path integral is the perfect place for the thimble approaches, as after rearranged into an initial value problem, there exists one and only one solution/critical-point/thimble. Given the singleness of the critical point, we reexamine the Lefschetz thimble and this time in light of the Generalized Thimble/Cauchy’s integral theorem, we introduce another family of integration cycles, sewed thimbles. The integration over these surfaces exactly reproduces the required result and the Lefschetz thimble will be recovered in a particular limit.
吉村浩司, 岡山大学異分野基礎科学研究所
[金茶会] 超高精度「原子核時計」で探る基礎物理
4号館セミナーホール リモート会場：JRB 2階大会議室, 仁科記念棟210室 https://www-conf.kek.jp/kincha/
https://www-conf.kek.jp/kincha/
トリウムの同位体であるトリウム２２９は、原子核として極めて特異な約8 eVという非常に低いエネルギーの励起準位（アイソマー準位）を持ち、レーザー光による直接的な励起が可能な唯一の原子核として注目を集めている。原子核は外部場の影響をほとんど受けないため、極めて安定した量子状態を実現することが可能である。もしレーザーを用いた原子核の制御が可能となれば、従来の原子時計を凌駕する精度を持つ「原子核時計」の実現へと繋がり、その波及効果は基礎物理学の革新に留まらず、産業や社会に多大な恩恵をもたらすと期待されている。トリウム２２９の特異性は1970年代から科学者の注目を集め、研究が進められてきたが、その詳細な特性は長らく謎に包まれていた。しかし、２０１６年にドイツの研究グループがアイソマー準位からの電子放出遷移を初めて観測したことで、この分野の研究は飛躍的な進展を遂げて、２０２４年には大きなマイルストーンとして、レーザーによるトリウム２２９の励起がついに実現した。この成果を受け、今後、世界各国で原子核時計の開発競争が本格化すると予想される。本講演では、こうした最近の原子核時計研究の進展について概観し、基礎物理学への応用や、その発展がもたらす科学的・技術的な可能性について展望する。
Shota Komatsu, CERN
Einstein Gravity from a Matrix Integral
Online (Zoom)
We formulate and test holography between a supersymmetric mass deformation of the Ishibashi-Kawai-Kitazawa-Tsuchiya (IKKT) matrix model and type IIB supergravity backgrounds with exceptional F4 supersymmetry. This is arguably the simplest example of holography in which the dual description contains Einstein gravity. We conjecture a one-to-one correspondence between saddle points of matrix integral and supergravity backgrounds, and test it through the supersymmetric localization of the matrix integral.
Tejhas Kapoor, IJCLab Orsay
New physics searches via angular distributions of B -> D* l nu ( l = e, mu, tau) decays
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Angular distributions are powerful probes to search for new physics signals and constrain the Standard Model parameters. The Belle collaboration has analyzed the B -> D* l nu (l = e, nu) distribution to constrain Vcb and B -> D* form factors. Using the newly released lattice QCD data along with the experimental data, we constrain new physics parameters and obtain correlations between new physics parameters and form factors to understand the hadronic uncertainties better. In the next step, to study B -> D* tau nu decay, we build a measurable angular distribution by considering the additional tau -> mu nu nu decay, and perform a sensitivity study with pseudo experimental data, indicating 5-6% sensitivity on right-handed and tensor currents.
Xiaoyang Wang, RIKEN- iTHEMS
Imaginary Hamiltonian variational ansatz for the Schwinger model and combinatorial optimization problems
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Variational quantum algorithms hold promise for efficiently solving combinatorial optimization problems that are difficult to solve classically on near-term quantum devices. The commonly used quantum approximate optimization algorithm (QAOA) suffers from adiabatic bottlenecks, leading to deep quantum circuits or longer evolution time. In contrast, imaginary time evolution algorithm often requires a constant evolution time. In this work, we propose the imaginary Hamiltonian variational ansatz (iHVA) to the ground state preparation of the Schwinger model and solve the MaxCut problem. This variational ansatz is inspired by the quantum imaginary time evolution algorithm. We introduce a tree arrangement of the parametrized quantum gates, enabling the exact solution of the MaxCut problem for any tree graphs. For randomly generated regular graphs, we numerically demonstrate that the MaxCut problem can be exactly solved using iHVA with a constant number of rounds. In contrast, QAOA requires the number of rounds that increases with system size, and the classically near-optimal Goemans- Williamson algorithm often yields only approximate solutions. We validate our algorithm’s advantage over QAOA through hardware experiments on a graph with 67 nodes.
Shaoping Li, Osaka U
Resonant Forbidden Leptogenesis
Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
