Pub Date : 2024-11-28DOI: 10.1038/s42005-024-01886-1
A. M. Marques, D. Viedma, V. Ahufinger, R. G. Dias
Flat band (FB) systems, featuring dispersionless energy bands, have garnered significant interest due to their compact localized states (CLSs). However, a detailed account on how local impurities affect the physical properties of overlapping CLSs is still missing. Here we study a diamond chain with a finite magnetic flux per plaquette that exhibits a gapped midspectrum FB with non-orthogonal CLSs, and develop a framework for projecting operators onto such non-orthogonal bases. This framework is applied to the case of an open diamond chain with small local impurities in the midchain plaquette, and analytical expressions are derived for FB states influenced by these impurities. For equal impurities in top and bottom sites under diagonal disorder, we show how the impurity states experience an averaged disorder dependent on their spatial extension, leading to enhanced robustness against disorder. For a single impurity, an exotic topological phase with a half-integer winding number is discovered, which is linked to a single in-gap edge state under open boundary conditions. Numerical simulations validate the analytical predictions. Flat bands states can be written, in general, as localized states that can couple by placing impurities at the overlapping regions, when present. The authors develop an analytic framework to derive impurity states in a diamond chain with magnetic flux and find an exotic behavior of these states characterized by a half-integer winding number.
{"title":"Impurity flat band states in the diamond chain","authors":"A. M. Marques, D. Viedma, V. Ahufinger, R. G. Dias","doi":"10.1038/s42005-024-01886-1","DOIUrl":"10.1038/s42005-024-01886-1","url":null,"abstract":"Flat band (FB) systems, featuring dispersionless energy bands, have garnered significant interest due to their compact localized states (CLSs). However, a detailed account on how local impurities affect the physical properties of overlapping CLSs is still missing. Here we study a diamond chain with a finite magnetic flux per plaquette that exhibits a gapped midspectrum FB with non-orthogonal CLSs, and develop a framework for projecting operators onto such non-orthogonal bases. This framework is applied to the case of an open diamond chain with small local impurities in the midchain plaquette, and analytical expressions are derived for FB states influenced by these impurities. For equal impurities in top and bottom sites under diagonal disorder, we show how the impurity states experience an averaged disorder dependent on their spatial extension, leading to enhanced robustness against disorder. For a single impurity, an exotic topological phase with a half-integer winding number is discovered, which is linked to a single in-gap edge state under open boundary conditions. Numerical simulations validate the analytical predictions. Flat bands states can be written, in general, as localized states that can couple by placing impurities at the overlapping regions, when present. The authors develop an analytic framework to derive impurity states in a diamond chain with magnetic flux and find an exotic behavior of these states characterized by a half-integer winding number.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-12"},"PeriodicalIF":5.4,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01886-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1038/s42005-024-01871-8
Aaveg Aggarwal, Shih-Yuan Chen, Eleftherios Kirkinis, Mohammed Imran Khan, Bei Fan, Michelle M. Driscoll, Monica Olvera de la Cruz
Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. Magnetic fields, in particular, carry the added advantage of biocompatibility as well as being able to actuate materials remotely. Although ferrofluid droplet migration induced by a high-frequency rotating magnetic field is a well-established effect, droplet migration at low frequencies is still elusive. Millimeter-sized ferrofluid droplets placed on a solid substrate, surrounded by an ambient gas phase, are shown here to migrate under a rotating magnetic field due to inertia-induced symmetry-breaking of the periodic deformation (wobbling) of the liquid-gas interface. This interface wobbling leads to droplet migration with speeds that increase as the amplitude and frequency of the magnetic field increase. In addition to migrating in a controlled manner, we demonstrate the ability of magnetic droplets to clean surface impurities and transport cargo. Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. In this study, the authors show that a rotating magnetic field leads a ferrofluid droplet to wobble, migrate, clean surface impurities and transport cargo.
{"title":"Wobbling and migrating ferrofluid droplets","authors":"Aaveg Aggarwal, Shih-Yuan Chen, Eleftherios Kirkinis, Mohammed Imran Khan, Bei Fan, Michelle M. Driscoll, Monica Olvera de la Cruz","doi":"10.1038/s42005-024-01871-8","DOIUrl":"10.1038/s42005-024-01871-8","url":null,"abstract":"Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. Magnetic fields, in particular, carry the added advantage of biocompatibility as well as being able to actuate materials remotely. Although ferrofluid droplet migration induced by a high-frequency rotating magnetic field is a well-established effect, droplet migration at low frequencies is still elusive. Millimeter-sized ferrofluid droplets placed on a solid substrate, surrounded by an ambient gas phase, are shown here to migrate under a rotating magnetic field due to inertia-induced symmetry-breaking of the periodic deformation (wobbling) of the liquid-gas interface. This interface wobbling leads to droplet migration with speeds that increase as the amplitude and frequency of the magnetic field increase. In addition to migrating in a controlled manner, we demonstrate the ability of magnetic droplets to clean surface impurities and transport cargo. Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. In this study, the authors show that a rotating magnetic field leads a ferrofluid droplet to wobble, migrate, clean surface impurities and transport cargo.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-7"},"PeriodicalIF":5.4,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01871-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1038/s42005-024-01868-3
Michael Klaiber, Karen Z. Hatsagortsyan, Christoph H. Keitel
The time delay in strong field tunneling ionization presents a captivating challenge in the field of attoscience. It is linked to the phase of the photoelectron wavepacket, a relationship that modern attosecond photoelectron interferometry can effectively probe. However, the connection between sub-barrier dynamics and the phase formation remains unclear. In this study, we investigate the role of under-the-barrier recollisions for shaping the phase of the photoelectron wavepacket. We establish a general analytical relationship between the phase of the tunneled electron wavepacket and the tunneling rate. Our results demonstrate that the Coulomb field effect of the atomic potential enhances both the amplitude of the recolliding path and the phase shift of the wavepacket, effectively countering the lateral spreading of the tunneling wavepacket during sub-barrier propagation. The insights gained from this research will aid in the development of free electron wavepackets with tailored properties through strong field ionization. This work investigates the origin of time delay in strong field tunneling ionization and its relation to the parameters of the photoelectron wavepacket. The authors establish a general analytical relationship between the phase of the wavepacket and the tunneling rate, and analyze the role of under-the-barrier recollisions for shaping the photoelectron wavepacket.
{"title":"Signatures of under-the-barrier dynamics in a tunneling electron wavepacket","authors":"Michael Klaiber, Karen Z. Hatsagortsyan, Christoph H. Keitel","doi":"10.1038/s42005-024-01868-3","DOIUrl":"10.1038/s42005-024-01868-3","url":null,"abstract":"The time delay in strong field tunneling ionization presents a captivating challenge in the field of attoscience. It is linked to the phase of the photoelectron wavepacket, a relationship that modern attosecond photoelectron interferometry can effectively probe. However, the connection between sub-barrier dynamics and the phase formation remains unclear. In this study, we investigate the role of under-the-barrier recollisions for shaping the phase of the photoelectron wavepacket. We establish a general analytical relationship between the phase of the tunneled electron wavepacket and the tunneling rate. Our results demonstrate that the Coulomb field effect of the atomic potential enhances both the amplitude of the recolliding path and the phase shift of the wavepacket, effectively countering the lateral spreading of the tunneling wavepacket during sub-barrier propagation. The insights gained from this research will aid in the development of free electron wavepackets with tailored properties through strong field ionization. This work investigates the origin of time delay in strong field tunneling ionization and its relation to the parameters of the photoelectron wavepacket. The authors establish a general analytical relationship between the phase of the wavepacket and the tunneling rate, and analyze the role of under-the-barrier recollisions for shaping the photoelectron wavepacket.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-9"},"PeriodicalIF":5.4,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01868-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1038/s42005-024-01882-5
Pinxuan He, Jiamin Liu, Honggang Gu, Hao Jiang, Shiyuan Liu
Numerical electromagnetic field solvers are significant for nanophotonic and photoelectronic technology, especially for computational imaging, metasurface, and biomedical microscopy, in which large-scale simulations serve as the core. Conventionally, these simulations use absorbing boundary conditions (ABC) to simulate open-domain systems. However, the existing ABCs require large memory to sufficiently suppress reflection at boundaries, which is prohibitive for large-scale applications. This work proposes a virtual absorbing boundary condition based on the angular spectrum method (ASM) to reduce the memory usage of ABC. The ASM is used to cover the polluted field in the boundary region, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit. This proposed method offers a substantial boost for applications related to large-scale simulations and memory-constrained devices like GPU. This work proposes a virtual boundary condition based on the angular spectrum method to reduce memory usage in electromagnetic simulations, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit.
{"title":"Modified Born series with virtual absorbing boundary enabling large-scale electromagnetic simulation","authors":"Pinxuan He, Jiamin Liu, Honggang Gu, Hao Jiang, Shiyuan Liu","doi":"10.1038/s42005-024-01882-5","DOIUrl":"10.1038/s42005-024-01882-5","url":null,"abstract":"Numerical electromagnetic field solvers are significant for nanophotonic and photoelectronic technology, especially for computational imaging, metasurface, and biomedical microscopy, in which large-scale simulations serve as the core. Conventionally, these simulations use absorbing boundary conditions (ABC) to simulate open-domain systems. However, the existing ABCs require large memory to sufficiently suppress reflection at boundaries, which is prohibitive for large-scale applications. This work proposes a virtual absorbing boundary condition based on the angular spectrum method (ASM) to reduce the memory usage of ABC. The ASM is used to cover the polluted field in the boundary region, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit. This proposed method offers a substantial boost for applications related to large-scale simulations and memory-constrained devices like GPU. This work proposes a virtual boundary condition based on the angular spectrum method to reduce memory usage in electromagnetic simulations, which eliminates the need to store the field in the boundary region. Combined with the Fourier transforms-based modified Born series, memory usage can be reduced to a level close to the theoretical limit.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-8"},"PeriodicalIF":5.4,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01882-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quantifying the strain, and even the strain state, is critical for the advancement of strain engineering in microelectronics and optoelectronics fields, whether using the classical semiconductors or emerging two-dimensional materials. Second Harmonic Generation (SHG) has emerged as a potent technique for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides (2D-TMDCs). Based on the theoretical framework of SHG, this work analyses the mechanism of different strain states acting on the SHG polarization-intensity spectrum (PIS) of MoS2. A quantifying method is proposed by establishing the analytic relationship between the in-plane strain components and the petal amplitude ratios (PARs) obtained from detected PIS. After calibrating the key parameters of MoS2 SHG PIS, a series of biaxial and uniaxial tensile experiments are performed, whose results are mostly agreed with the theoretical expectations, thus verifying the reliability, correctness and universality of the proposed method for quantitively characterizing the strain state of monolayer MoS2. Second Harmonic Generation (SHG) is potent for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides. This work presents a method to quantify the strain state influence on the SHG polarization-intensity spectrum of MoS2, and the reliability of proposed method is verified by numerical and physical experiments.
{"title":"Quantifying the in-plane strain influence on second harmonic generation of molybdenum disulfide","authors":"Huadan Xing, Jibin Liu, Zihao Zhao, Xiaoyong He, Wei Qiu","doi":"10.1038/s42005-024-01877-2","DOIUrl":"10.1038/s42005-024-01877-2","url":null,"abstract":"Quantifying the strain, and even the strain state, is critical for the advancement of strain engineering in microelectronics and optoelectronics fields, whether using the classical semiconductors or emerging two-dimensional materials. Second Harmonic Generation (SHG) has emerged as a potent technique for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides (2D-TMDCs). Based on the theoretical framework of SHG, this work analyses the mechanism of different strain states acting on the SHG polarization-intensity spectrum (PIS) of MoS2. A quantifying method is proposed by establishing the analytic relationship between the in-plane strain components and the petal amplitude ratios (PARs) obtained from detected PIS. After calibrating the key parameters of MoS2 SHG PIS, a series of biaxial and uniaxial tensile experiments are performed, whose results are mostly agreed with the theoretical expectations, thus verifying the reliability, correctness and universality of the proposed method for quantitively characterizing the strain state of monolayer MoS2. Second Harmonic Generation (SHG) is potent for exploring the optical-mechanical properties of two-dimensional transition metal dichalcogenides. This work presents a method to quantify the strain state influence on the SHG polarization-intensity spectrum of MoS2, and the reliability of proposed method is verified by numerical and physical experiments.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-10"},"PeriodicalIF":5.4,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01877-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1038/s42005-024-01869-2
Stefano Biasi, Alessio Lugnan, Davide Micheli, Lorenzo Pavesi
Photonic platforms are promising for implementing neuromorphic hardware due to their high processing speed, low power consumption, and ability to perform parallel processing. A ubiquitous device in integrated photonics, which has been extensively employed for the realization of optical neuromorphic hardware, is the microresonator. The ability of CMOS-compatible silicon microring resonators to store energy enhances the nonlinear interaction between light and matter, enabling energy efficient nonlinearity, fading memory and the generation of spikes via self-pulsing. In the self-pulsing regime, a constant input signal can be transformed into a time-dependent signal based on pulse sequences. Previous research has shown that self-pulsing enables the microresonator to function as an energy-efficient artificial spiking neuron. Here, we extend the experimental study of single and coupled microresonators in the self-pulsing regime to confirm their potential as building blocks for scalable photonic spiking neural networks. Furthermore, we demonstrate their potential for introducing all-optical long-term memory and event detection capabilities into integrated photonic neural networks. In particular, we show all-optical long-term memory up to at least 10 μs and detection of input spike rates, which is encoded into different stable self-pulsing dynamics. While silicon photonics is an attractive platform for neuromorphic computing, it generally lacks scalable nodes that provide nonlinearity and memory. Here, the authors show experimentally that simple and compact networks of silicon microring resonators exhibit complex self-pulsing responses that can be exploited for all-optical long-term memory and sensing.
{"title":"Exploring the potential of self-pulsing optical microresonators for spiking neural networks and sensing","authors":"Stefano Biasi, Alessio Lugnan, Davide Micheli, Lorenzo Pavesi","doi":"10.1038/s42005-024-01869-2","DOIUrl":"10.1038/s42005-024-01869-2","url":null,"abstract":"Photonic platforms are promising for implementing neuromorphic hardware due to their high processing speed, low power consumption, and ability to perform parallel processing. A ubiquitous device in integrated photonics, which has been extensively employed for the realization of optical neuromorphic hardware, is the microresonator. The ability of CMOS-compatible silicon microring resonators to store energy enhances the nonlinear interaction between light and matter, enabling energy efficient nonlinearity, fading memory and the generation of spikes via self-pulsing. In the self-pulsing regime, a constant input signal can be transformed into a time-dependent signal based on pulse sequences. Previous research has shown that self-pulsing enables the microresonator to function as an energy-efficient artificial spiking neuron. Here, we extend the experimental study of single and coupled microresonators in the self-pulsing regime to confirm their potential as building blocks for scalable photonic spiking neural networks. Furthermore, we demonstrate their potential for introducing all-optical long-term memory and event detection capabilities into integrated photonic neural networks. In particular, we show all-optical long-term memory up to at least 10 μs and detection of input spike rates, which is encoded into different stable self-pulsing dynamics. While silicon photonics is an attractive platform for neuromorphic computing, it generally lacks scalable nodes that provide nonlinearity and memory. Here, the authors show experimentally that simple and compact networks of silicon microring resonators exhibit complex self-pulsing responses that can be exploited for all-optical long-term memory and sensing.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-10"},"PeriodicalIF":5.4,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11584396/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142709489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Developing a comprehensive magnetic theory for correlated itinerant magnets poses challenges due to the difficulty in reconciling both local moments and itinerant electrons. In this work, we investigate the microscopic process of magnetic phase transition in ferromagnetic metal Fe3−δGeTe2. We find that Hund’s coupling is crucial for establishing ferromagnetic order. During the ferromagnetic transition, we observe the formation of quasiparticle flat bands and an opposing tendency in spectral weight transfer, primarily between the lower and upper Hubbard bands, across the two spin channels. Moreover, our results indicate that one of the inequivalent Fe sites exhibits Mott physics, while the other Fe site exhibits Hund’s physics, attributable to their distinct atomic environments. We suggest that ferromagnetic order reduces spin fluctuations and makes flat bands near the Fermi level more distinct. The hybridization between the distinctly flat bands and other itinerant bands offers a possible way to form heavy fermion behavior in ferromagnets. The complex interactions of competing orders drive correlated magnetic metals to a new frontier for discovering outstanding quantum states. Understanding magnetism in correlated itinerant systems has been an important yet challenging task due to the complex interplay among Hund, Mott, and Kondo physics. In this work, by using DFT + DMFT, the authors reveal the mechanism of the magnetic phase transition and the heavy-fermion behavior in low temperatures in a ferromagnetic metal, shedding light on the roles of the above three factors.
{"title":"Mechanism of magnetic phase transition in correlated magnetic metal: insight into itinerant ferromagnet Fe3−δGeTe2","authors":"Yuanji Xu, Yue-Chao Wang, Xintao Jin, Haifeng Liu, Yu Liu, Haifeng Song, Fuyang Tian","doi":"10.1038/s42005-024-01874-5","DOIUrl":"10.1038/s42005-024-01874-5","url":null,"abstract":"Developing a comprehensive magnetic theory for correlated itinerant magnets poses challenges due to the difficulty in reconciling both local moments and itinerant electrons. In this work, we investigate the microscopic process of magnetic phase transition in ferromagnetic metal Fe3−δGeTe2. We find that Hund’s coupling is crucial for establishing ferromagnetic order. During the ferromagnetic transition, we observe the formation of quasiparticle flat bands and an opposing tendency in spectral weight transfer, primarily between the lower and upper Hubbard bands, across the two spin channels. Moreover, our results indicate that one of the inequivalent Fe sites exhibits Mott physics, while the other Fe site exhibits Hund’s physics, attributable to their distinct atomic environments. We suggest that ferromagnetic order reduces spin fluctuations and makes flat bands near the Fermi level more distinct. The hybridization between the distinctly flat bands and other itinerant bands offers a possible way to form heavy fermion behavior in ferromagnets. The complex interactions of competing orders drive correlated magnetic metals to a new frontier for discovering outstanding quantum states. Understanding magnetism in correlated itinerant systems has been an important yet challenging task due to the complex interplay among Hund, Mott, and Kondo physics. In this work, by using DFT + DMFT, the authors reveal the mechanism of the magnetic phase transition and the heavy-fermion behavior in low temperatures in a ferromagnetic metal, shedding light on the roles of the above three factors.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-8"},"PeriodicalIF":5.4,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01874-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1038/s42005-024-01860-x
Priyanka Iyer, Rajendra Singh Negi, Andreas Schadschneider, Gerhard Gompper
Understanding the navigation through semi-dense crowds at intersections poses a significant challenge in pedestrian dynamics, with implications for facility design and insights into emergent collective behavior. To tackle this problem, a system of cognitive active agents at a crowded three-way intersection is studied using Langevin simulations of intelligent active Brownian particles (iABPs) with directed visual perception (resulting in non-reciprocal interactions) and self-steering avoidance—without volume exclusion. We find that the emergent self-organization depends on agent maneuverability, goal fixation, and vision angle, and identify several forms of collective behavior, including localized flocking, jamming and percolation, and self-organized rotational flows. Additionally, we demonstrate that the motion of individual agents can be characterized by fractional Brownian motion and Lévy walk models across different parameter regimes. Moreover, despite the rich variety of collective behavior, the fundamental flow diagram shows a universal curve for different vision angles. Our research highlights the impact of collision avoidance, goal following, and vision angle on the individual and collective dynamics of interacting pedestrians. The study of self-organisation of pedestrian movement at crossing is important for the design of strategies facilitating pedestrian flow in crowded areas and the mitigation of crowd-related accidents. The authors study the motion of pedestrians using a model inspired from active matter systems finding interesting phases of three interacting streams of agents, including jamming, and the emergence of a vortex state.
{"title":"Directed motion of cognitive active agents in a crowded three-way intersection","authors":"Priyanka Iyer, Rajendra Singh Negi, Andreas Schadschneider, Gerhard Gompper","doi":"10.1038/s42005-024-01860-x","DOIUrl":"10.1038/s42005-024-01860-x","url":null,"abstract":"Understanding the navigation through semi-dense crowds at intersections poses a significant challenge in pedestrian dynamics, with implications for facility design and insights into emergent collective behavior. To tackle this problem, a system of cognitive active agents at a crowded three-way intersection is studied using Langevin simulations of intelligent active Brownian particles (iABPs) with directed visual perception (resulting in non-reciprocal interactions) and self-steering avoidance—without volume exclusion. We find that the emergent self-organization depends on agent maneuverability, goal fixation, and vision angle, and identify several forms of collective behavior, including localized flocking, jamming and percolation, and self-organized rotational flows. Additionally, we demonstrate that the motion of individual agents can be characterized by fractional Brownian motion and Lévy walk models across different parameter regimes. Moreover, despite the rich variety of collective behavior, the fundamental flow diagram shows a universal curve for different vision angles. Our research highlights the impact of collision avoidance, goal following, and vision angle on the individual and collective dynamics of interacting pedestrians. The study of self-organisation of pedestrian movement at crossing is important for the design of strategies facilitating pedestrian flow in crowded areas and the mitigation of crowd-related accidents. The authors study the motion of pedestrians using a model inspired from active matter systems finding interesting phases of three interacting streams of agents, including jamming, and the emergence of a vortex state.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-11"},"PeriodicalIF":5.4,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01860-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding the evolution of cooperation in multi-player games is of vital significance for natural and social systems. An important challenge is that group interactions often lead to nonlinear synergistic effects. However, previous models mainly focus on deterministic nonlinearity, where synergy or discounting effects occur under specific conditions, not accounting for uncertainty and stochasticity in real-world systems. Here, we develop a probabilistic framework to study the cooperative behavior in stochastic nonlinear public goods games. Through both analytical treatment and Monte Carlo simulations, we provide a comprehensive understanding of social dilemmas with stochastic nonlinearity in both well-mixed and structured populations. We find that increasing the degree of nonlinearity makes synergy more advantageous when competing with discounting, thereby promoting cooperation. Furthermore, we show that network reciprocity loses effectiveness when the probability of synergy is small. Moreover, group size exhibits nonlinear effects on group cooperation regardless of the underlying structure. Our findings thus provide insights into how stochastic nonlinearity influences the emergence of prosocial behavior. Cooperation in multi-player games is influenced by nonlinear interactions and randomness found in natural and social systems. The authors develop a probabilistic framework and find that stronger nonlinear effects enhance cooperation by boosting the collective benefits of working together, and that network reciprocity loses effectiveness when synergistic interactions are rare.
{"title":"Evolutionary dynamics in stochastic nonlinear public goods games","authors":"Wenqiang Zhu, Xin Wang, Chaoqian Wang, Longzhao Liu, Jiaxin Hu, Zhiming Zheng, Shaoting Tang, Hongwei Zheng, Jin Dong","doi":"10.1038/s42005-024-01865-6","DOIUrl":"10.1038/s42005-024-01865-6","url":null,"abstract":"Understanding the evolution of cooperation in multi-player games is of vital significance for natural and social systems. An important challenge is that group interactions often lead to nonlinear synergistic effects. However, previous models mainly focus on deterministic nonlinearity, where synergy or discounting effects occur under specific conditions, not accounting for uncertainty and stochasticity in real-world systems. Here, we develop a probabilistic framework to study the cooperative behavior in stochastic nonlinear public goods games. Through both analytical treatment and Monte Carlo simulations, we provide a comprehensive understanding of social dilemmas with stochastic nonlinearity in both well-mixed and structured populations. We find that increasing the degree of nonlinearity makes synergy more advantageous when competing with discounting, thereby promoting cooperation. Furthermore, we show that network reciprocity loses effectiveness when the probability of synergy is small. Moreover, group size exhibits nonlinear effects on group cooperation regardless of the underlying structure. Our findings thus provide insights into how stochastic nonlinearity influences the emergence of prosocial behavior. Cooperation in multi-player games is influenced by nonlinear interactions and randomness found in natural and social systems. The authors develop a probabilistic framework and find that stronger nonlinear effects enhance cooperation by boosting the collective benefits of working together, and that network reciprocity loses effectiveness when synergistic interactions are rare.","PeriodicalId":10540,"journal":{"name":"Communications Physics","volume":" ","pages":"1-10"},"PeriodicalIF":5.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s42005-024-01865-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142714740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1038/s42005-024-01867-4
Jacob Lamers, Guy Verschaffelt, Guy Van der Sande
Ising machines are dedicated hardware solvers of NP-hard optimization problems. However, they do not always find the most optimal solution. The probability of finding this optimal solution depends on the problem at hand. Using continuation methods, we show that this is closely linked to how the ground state emerges from other states when a system parameter is changed, i.e. its bifurcation sequence. From this analysis, we can determine the effectiveness of solution schemes. Moreover, we find that the proper choice of implementation of the Ising machine can drastically change this bifurcation sequence and therefore vastly increase the probability of finding the optimal solution. Lastly, we also show that continuation methods themselves can be used directly to solve optimization problems. An Ising machine is a piece of hardware that tries to solve quadratic unconstrained binary optimization problems. The authors explain why some problems are significantly easier to tackle than others using Ising machines and demonstrate that different physical implementations can render some challenging problems a lot easier to solve.
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