CEA, DRF, Joliot, NeuroSpin, Paris-Saclay University(法国原子能委员会,DRF,若利奥中心,NeuroSpin,巴黎萨克雷大学);Inria MIND team, Paris-Saclay University(法国国家信息与自动化研究所,MIND团队,巴黎萨克雷大学);Department of Neuroscience and Biomedical Engineering, Aalto University(阿尔托大学,神经科学与生物医学工程系);Neuroscience Center, Helsinki Institute of Life Science, Helsinki University(赫尔辛基大学生命科学研究所,神经科学中心);School of Psychology & Neuroscience, University of Glasgow(格拉斯哥大学,心理学与神经科学学院)
Merlin Dumeur, Sheng H. Wang, J. Matias Palva, Philippe Ciuciu
The brain criticality hypothesis has largely only characterized brain dynamics in terms of their self-similarity, although experimental evidence suggests that the brain exhibits significant multifractality. To understand how multifractality may emerge in critical-like systems modeling neuronal activity, we used a neural field model exhibiting neural oscillations and a critical phase transition. We find that multifractality emerges near a synchronization phase transition, and that the pattern of variation of multifractality changes when placing the model at a different phase transition. These findings show that multifractality in temporal dynamics emerges near criticality in neural fields, providing a formal basis for interpreting multifractality in brain recordings.
Generalized multifractality characterizes scaling of eigenstate observables at Anderson-localization critical points. We explore generalized multifractality in 2D systems, with the main focus on the spin quantum Hall (SQH) transition in superconductors of symmetry class C. Relations and differences with the conventional integer quantum Hall (IQH) transition are also studied. Using the field-theoretical formalism of non-linear sigma-model, we derive the pure-scaling operators representing generalizing multifractality and then "translate" them to the language of eigenstate observables. Performin…
Describing the critical behavior of the Anderson transition in infinite dimension by random-matrix ensembles: logarithmic multifractality and critical localization
Entanglement entropy and multifractality at localization transitions
von Neumann纠缠熵是表征量子相变的一个有用的度量。我们研究了非相互作用电子系统中无序主导的量子相变中熵的非解析性。在这些临界点上,冯诺伊曼熵由单个粒子的波函数强度决定,它表现出复杂的标度不变波动。我们发现,多重分形的概念自然适合于研究临界波函数的冯诺伊曼熵。我们对三维安德森局域化跃迁和整数量子Hall平台跃迁的数值模拟表明,多重分形分析可以很好地描述这些跃迁处的纠缠.
The spin quantum Hall (or class C) transition represents one of the few localization-delocalization transitions for which some of the critical exponents are known exactly. Not known, however, is the multifractal spectrum, $τ_q$, which describes the system-size scaling of inverse participation ratios $P_q$, i.e., the $q$-moments of critical wavefunction amplitudes. We here report simulations based on the class C Chalker-Coddington network and demonstrate that $τ_q$ is (essentially) a quartic polynomial in $q$. Analytical results fix all prefactors except the quartic curvature that we obtain as …
This work extends the analysis of the generalized multifractality of critical eigenstates at the spin quantum Hall transition in two-dimensional disordered superconductors [J. F. Karcher et al, Annals of Physics, 435, 168584 (2021)]. A mapping to classical percolation is developed for a certain set of generalized-multifractality observables. In this way, exact analytical results for the corresponding exponents are obtained. Furthermore, a general construction of positive pure-scaling eigenfunction observables is presented, which permits a very efficient numerical determination of scaling expon…
We study generalized multifractality characterizing fluctuations and correlations of eigenstates in disordered systems of symmetry classes AII, D, and DIII. Both metallic phases and Andersonlocalization transitions are considered. By using the non-linear sigma-model approach, we construct pure-scaling eigenfunction observables. The construction is verified by numerical simulations of appropriate microscopic models, which also yield numerical values of the corresponding exponents. In the metallic phases, the numerically obtained exponents satisfy Weyl symmetry relations as well as generalized p…
Repeated local measurements of quantum many body systems can induce a phase transition in their entanglement structure. These measurement-induced phase transitions (MIPTs) have been studied for various types of dynamics, yet most cases yield quantitatively similar values of the critical exponents, making it unclear if there is only one underlying universality class. Here, we directly probe the properties of the conformal field theories governing these MIPTs using a numerical transfer-matrix method, which allows us to extract the effective central charge, as well as the first few low-lying scal…
We implement a recursive Green function method to extract the Fock space (FS) propagator and associated self-energy across the many-body localization (MBL) transition, for one-dimensional interacting fermions in a random onsite potential. We show that the typical value of the imaginary part of the local FS self-energy, Δ_t, related to the decay rate of an initially localized state, acts as a probabilistic order parameter for the thermal to MBL phase transition; and can be used to characterize critical properties of the transition as well as the multifractal nature of MBL states as a function o…
Multifractality at the Integer Quantum Hall Transition: Acquittal of the Parabolic Law
Max Planck Institute for the Physics of Complex Systems(马克斯·普朗克复杂系统物理研究所);School of Science, Constructor University(康斯特鲁克特大学理学院);Institute for Theoretical Physics, University of Cologne(科隆大学理论物理研究所)