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Symbology of Feynman integrals from twistor geometries

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Science China(physics,Mechanics & Astronomy) 2024年第3期67卷 44-59页

作者： Song He Jiahao Liu Yichao Tang Qinglin Yang School of Fundamental physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUCASHangzhou 310024China CAS Key Laboratory of theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China International Centre for theoretical physics Asia-Pacific Beijing 100049 Peng Huanwu Center for Fundamental Theory Hefei 230026China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

We study the symbology of planar Feynman integrals in dimensional regularization by considering geometric configurations in momentum twistor space corresponding to their leading singularities(LS). Cutting propagators in momentum twistor space amounts to intersecting lines associated with loop and external dual momenta, including the special line associated with the point at infinity, which breaks dual conformal symmetry. We show that cross-ratios of intersection points on these lines, especially those on the infinity line, naturally produce symbol letters for Feynman integrals in D = 4-2∈, which include and generalize their LS. At one loop, we obtain all symbol letters using intersection points from quadruple cuts for integrals up to pentagon kinematics with two massive corners, which agree perfectly with canonical differential equation(CDE) results. We then obtain all two-loop letters, for up to four-mass box and one-mass pentagon kinematics, by considering more intersections arising from two-loop cuts. Finally we comment on how cluster algebras appear from this construction, and importantly how we may extend the method to non-planar integrals.

关键词： Feynman integrals symbol letters twistor geometry

Analytical solutions of equatorial geodesic motion in Kerr spacetime

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Chinese physics C 2024年第4期48卷 222-239页

作者：刘岩孙兵 Department of physics Yantai UniversityYantai 264005China Department of Basic Courses Beijing University of AgricultureBeijing 102206China CAS Key Laboratory of theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China

The study of Kerr geodesics has a long history,particularly for those occurring within the equatorial plane,which are generally ***,when compared with the classification introduced by one of the authors[***.D 105,024075(2022)],it becomes apparent that certain classes of geodesics,such as trapped orbits,still lack analytical ***,in this study,we provide explicit analytical solutions for equatorial timelike geodesics in Kerr spacetime,including solutions of trapped orbits,which capture the characteristics of special geodesics,such as the positions and conserved quantities of circular,bound,and deflecting ***,we determine the precise location at which retrograde orbits undergo a transition from counter-rotating to prograde motion due to the strong gravitational effects near a rotating black ***,the trajectory remains prograde for orbits with negative energy despite the negative angular ***,we investigate the intriguing phenomenon of deflecting orbits exhibiting an increased number of revolutions around the black hole as the turning point approaches the turning point of the trapped ***,we find that only prograde marginal deflecting geodesics are capable of traversing through the *** summary,our findings present explicit solutions for equatorial timelike geodesics and offer insights into the dynamics of particle motion in the vicinity of a rotating black hole.

关键词： geodesic motion analytical solutions equatorial plane Kerr spacetime

K-core attack, equilibrium K-core,and kinetically constrained spin system

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Chinese physics B 2024年第6期33卷 14-26页

作者：周海军 Institute of theoretical physics Chinese Academy of SciencesBeijing 100190China MinJiang Collaborative Center for theoretical physics MinJiang UniversityFuzhou 350108China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

Kinetically constrained spin systems are toy models of supercooled liquids and amorphous solids. In this perspective,we revisit the prototypical Fredrickson–Andersen(FA) kinetically constrained model from the viewpoint of K-core combinatorial optimization. Each kinetic cluster of the FA system, containing all the mutually visitable microscopic occupation configurations, is exactly the solution space of a specific instance of the K-core attack problem. The whole set of different jammed occupation patterns of the FA system is the configuration space of an equilibrium K-core problem. Based on recent theoretical results achieved on the K-core attack and equilibrium K-core problems, we discuss the thermodynamic spin glass phase transitions and the maximum occupation density of the fully unfrozen FA kinetic cluster, and the minimum occupation density and extreme vulnerability of the partially frozen(jammed) kinetic clusters. The equivalence between K-core attack and the fully unfrozen FA kinetic cluster also implies a new way of sampling K-core attack solutions.

关键词： Fredrickson–Andersen model K-core attack spin glass jamming

Landau quantization effects on damping Kawahara solitons in electron–positron–ion plasma in rotating ionized medium

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Communications in theoretical physics 2024年第10期76卷 143-152页

作者： E I El-Awady S Hussain N Akhtar Department of physics Faculty of Science Port Said University theoretical physics Division (TPD) PINSTECH

For the dynamics of three-dimensional electron–positron–ion plasmas, a fluid quantum hydrodynamic model is proposed by considering Landau quantization effects in dense ***–neutral collisions in the presence of the Coriolis force are also considered. The application of the reductive perturbation technique produces a wave evolution equation represented by a damped Korteweg–de Vries equation. This equation, however, is insufficient for describing waves in our system at very low dispersion coefficients. As a result, we considered the highest-order perturbation, which resulted in the damped Kawahara equation. The effects of the magnetic field, Landau quantization, the ratio of positron density to electron density, the ratio of positron density to ion density, and the direction cosine on linear dispersion laws as well as soliton and conoidal solutions of the damped Kawahara equation are explored. The understanding from this research can contribute to the broader field of astrophysics and aid in the interpretation of observational data from white dwarfs.

关键词： Coriolis force Kawahara equation Landau quantization magnetoplasmas quantum plasma solitary and cnoidal waves

Classification of high-ordered topological nodes towards Moiré flat bands in twisted bilayers

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Science China(physics,Mechanics & Astronomy) 2024年第9期67卷 133-147页

作者： Fan Cui Congcong Le Qiang Zhang Xianxin Wu Jiangping Hu Ching-Kai Chiu Beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China RIKEN Interdisciplinary theoretical and Mathematical Sciences(iTHEMS) Wako 351-0198Japan CAS Key Laboratory of theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China Kavli Institute of theoretical Sciences University of Chinese Academy of SciencesBeijing 100190China New Cornerstone Science Laboratory Beijing 100190China

At magic twisted angles,Dirac cones in twisted bilayer graphene(TBG)can evolve into flat bands,serving as a critical playground for the study of strongly correlated *** chiral symmetry is introduced,rigorous mathematical proof confirms that the flat bands are locked at zero energy in the entire Moiré Brillouin zone(BZ).Yet,TBG is not the sole platform that exhibits this absolute band *** to this flatness phenomenon are topological nodes and their specific locations in the *** this study,considering twisted bilayer systems that preserve chiral symmetry,we classify various ordered topological nodes in base layers and all possible node locations across different ***,we constrain the node locations to rotational centers,such as Γ and M points,to ensure the interlayer coupling retains equal strength in all *** this classification as a foundation,we systematically identify the conditions under which Moiré flat bands ***,through the extension of holomorphic functions,we provide proof that flat bands are locked at zero energy,shedding light on the origin of the band ***,beyond Dirac cones,numerous twisted bilayer nodal platforms can host flat bands with a degeneracy number of more than two,such as four-fold,six-fold,and *** multiplicity of degeneracy in flat bands might unveil more complex and enriched correlation physics.

关键词： twisted bilayer systems high-ordered topological nodes Moriéflat bands high degeneracy

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Gravitational waves and primordial black hole productions from gluodynamics by holography

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Science China(physics,Mechanics & Astronomy) 2024年第4期67卷 31-42页

作者： Song He Li Li Zhibin Li Shao-Jiang Wang Center for theoretical physics and College of physics Jilin UniversityChangchun 130012China Max Planck Institute for Gravitational physics(Albert Einstein Institute) Golm 14476Germany CAS Key Laboratory of theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Fundamental physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China Peng Huanwu Collaborative Center for Research and Education Beihang UniversityBeijing 100191China School of physics and Microelectronics Zhengzhou UniversityZhengzhou 450001China

Understanding the nature of quantum chromodynamics(QCD)matter is important but challenging due to the presence of nonperturbative dynamics under extreme *** construct a holographic model describing the gluon sector of QCD at finite temperatures in the non-perturbative *** equation of state as a function of temperature is in good accordance with the lattice QCD ***,the Polyakov loop and the gluon condensation,which are proper order parameters to capture the deconfinement phase transition,also agree quantitatively well with the lattice QCD *** obtain a strong first-order confinement/deconfinement phase transition at Tc=276.5 Me V that is consistent with the lattice QCD *** on our model for a pure gluon hidden sector,we compute the stochastic gravitational waves and primordial black hole(PBH)productions from this confinement/deconfinement phase transition in the early *** resulting stochastic gravitational-wave backgrounds are found to be within detectability in the International Pulsar Timing Array and Square Kilometre Array in the near future when the associated productions of PBHs saturate the current observational bounds on the PBH abundances from the LIGO-Virgo-Collaboration O3 data.

关键词： AdS/QCD confinement/deconfinement phase transition gravitational wave primordial black hole

Masses and decays of triply-heavy pentaquarks

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Chinese physics C 2024年第10期48卷 137-149页

作者： Chang-Le Liu Wen-Xuan Zhang Duo-Jie Jia Institute of theoretical physics College of Physics and Electronic EngineeringNorthwest Normal UniversityLanzhou 730070China General Education Center Qinghai Institute of TechnologyXining 810000China Lanzhou Center for theoretical physics Lanzhou UniversityLanzhou 730000China

In this study,we analyzed masses and decays of triply-heavy pentaquarks QQQnn(Q=b,c)in the unified MIT bag *** construct the color-spin wave functions of the triply-heavy pentaquarks and use the numerical variational method to compute all the ground-state masses of these *** excluding the scattering states in configuration spsce,we computed the decay width ratios of each decay channel relative to the maximum width for the compact pentaquark states,obtaining the main decay modes of the triply-heavy pentaquark systems.

关键词： pentaquark mass decay channels

Observations on spontaneous chiral symmetry breaking and the mass gap of QCD in finite volume

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Communications in theoretical physics 2024年第9期76卷 42-47页

作者： Xiaolan Meng Bolun Hu Yi-Bo Yang University of Chinese Academy of Sciences School of Physical SciencesBeijing 100049China CAS Key Laboratory of theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Fundamental physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUCASHangzhou 310024China International Centre for theoretical physics Asia-Pacific Beijing/HangzhouChina

We present a lattice quantum chromodynamics(QCD)simulation with 2+1+1 flavor full QCD ensembles using near-physical quark masses and different spatial sizes L,at a~0.055 *** results show that the scalar and pesudoscalar 2-point correlator with a valence pion mass of approximately 230 MeV become degenerated at L≤1.0 fm,and such an observation suggests that the spontaneous chiral symmetry breaking disappears effectively at this *** the same time,the mass gap between the nucleon and pion masses remains larger thanΛQCDin the entire L∈[0.2,0.7]fm range.

关键词： lattice QCD chiral symmetry breaking confinement

Asymmetric nucleation processes in spontaneous mode switch of active matter

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Communications in theoretical physics 2024年第5期76卷 154-158页

作者：杨冰王延颋 CAS Key Laboratory of theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

Flocking and vortical are two typical motion modes in active *** it is known that the two modes can spontaneously switch between each other in a finite-size system,the switching dynamics remain *** this work,by computer simulation of a two-dimensional Vicsek-like system with 1000 particles,we find from the perspective of the classical nucleation theory that the forward and backward switching dynamics are asymmetric:going from flocking to vortical is a one-step nucleation process,while the opposite is a two-step nucleation process,with the system staying in a metastable state before reaching the final flocking state.

关键词： active matter dynamics classical nucleation theory