Infinite-Volume Limit of Stochastic s-d System with Single-Component Impurity and s-Electron Spins

2021 ◽  
Vol 28 (01) ◽  
pp. 2150003
Author(s):  
Jan Maćkowiak
Keyword(s):  
Impurity Concentration ◽  
Mean Field ◽  
Magnetic Alloy ◽  
Magnetic Impurities ◽  
Infinite Volume ◽  
Volume Limit ◽  
Laplace Expansion ◽  
The Mean ◽  
Impurity Sites ◽  
Infinite Volume Limit

A Hamiltonian [Formula: see text], with locally smeared Ising-type s-d exchange between s-electrons and magnetic impurities, in a dilute magnetic alloy, is investigated. The Feynman-Kac theorem, Laplace expansion and Bogolyubov inequality are applied to obtain a lower and upper bound (lb and ub) on the system’s free energy per conducting electron [Formula: see text]. The two bounds differ, in the infinite-volume limit by a term [Formula: see text], linear in impurity concentration: lb[Formula: see text], ub[Formula: see text], [Formula: see text] denoting the Hamiltonian of the approximating mean-field s-d system. [Formula: see text] represents randomly positioned impurities interacting with a mean field implemented by the gas of conduction s-electrons, the latter interacting with the field of barriers and wells (according to the s-electron’s spin orientation) localized at the impurity sites. The inequality [Formula: see text] demonstrates increasing accuracy of the mean-field [Formula: see text]-theory, with decreasing impurity concentration.

scholarly journals ON THE MEAN FIELD ANSATZ IN ANYON THEORIES

1992 ◽  
Vol 07 (19) ◽  
pp. 4619-4632
Author(s):  
DANIEL BOYANOVSKY
Keyword(s):  
Magnetic Field ◽  
Mean Field ◽  
Finite Geometry ◽  
Density Fluctuations ◽  
Coulomb Interactions ◽  
Translational Invariance ◽  
Gauge Transformations ◽  
Volume Limit ◽  
The Mean ◽  
Infinite Volume Limit

We study the physics of the mean field ansatz in a simplified anyon model. The model is solved exactly in a finite geometry with particular attention to boundary conditions compatible with a mean statistical magnetic field. The spectrum consists of bosonic plasma-like density fluctuations with a gap. We find that the repulsive Coulomb interactions introduced by the fluctuations around the mean field force the statistical charge and magnetic field to become localized near the boundaries. Translational invariance, broken by the mean field, is restored in the infinite volume limit as the statistical charge and magnetic field escape to infinity. The polarization effects of an external magnetic field and the role of “large” gauge transformations are also studied.

scholarly journals Tree Polymers in the Infinite Volume Limit at Critical Strong Disorder

2011 ◽  
Vol 48 (03) ◽  
pp. 885-891
Author(s):  
Torrey Johnson ◽  
Edward C. Waymire
Keyword(s):  
Asymptotic Variance ◽  
Standard Theory ◽  
Convergence In Probability ◽  
Infinite Volume ◽  
Weak Disorder ◽  
Branching Random Walks ◽  
Strong Disorder ◽  
Volume Limit ◽  
Specific Formula ◽  
Infinite Volume Limit

The almost-sure existence of a polymer probability in the infinite volume limit is readily obtained under general conditions of weak disorder from standard theory on multiplicative cascades or branching random walks. However, speculations in the case of strong disorder have been mixed. In this note existence of an infinite volume probability is established at critical strong disorder for which one has convergence in probability. Some calculations in support of a specific formula for the almost-sure asymptotic variance of the polymer path under strong disorder are also provided.

scholarly journals Non-integrable Ising Models in Cylindrical Geometry: Grassmann Representation and Infinite Volume Limit

2021 ◽  
Author(s):  
Giovanni Antinucci ◽  
Alessandro Giuliani ◽  
Rafael L. Greenblatt
Keyword(s):  
Nearest Neighbor ◽  
Scaling Limit ◽  
Ising Models ◽  
Infinite Volume ◽  
Effective Potentials ◽  
Volume Limit ◽  
Cylindrical Domains ◽  
Key Aspects ◽  
Infinite Volume Limit ◽  
Detailed Derivation

AbstractIn this paper, meant as a companion to Antinucci et al. (Energy correlations of non-integrable Ising models: the scaling limit in the cylinder, 2020. arXiv: 1701.05356), we consider a class of non-integrable 2D Ising models in cylindrical domains, and we discuss two key aspects of the multiscale construction of their scaling limit. In particular, we provide a detailed derivation of the Grassmann representation of the model, including a self-contained presentation of the exact solution of the nearest neighbor model in the cylinder. Moreover, we prove precise asymptotic estimates of the fermionic Green’s function in the cylinder, required for the multiscale analysis of the model. We also review the multiscale construction of the effective potentials in the infinite volume limit, in a form suitable for the generalization to finite cylinders. Compared to previous works, we introduce a few important simplifications in the localization procedure and in the iterative bounds on the kernels of the effective potentials, which are crucial for the adaptation of the construction to domains with boundaries.

scholarly journals QUANTUM NOISE INDUCED ENTANGLEMENT AND CHAOS IN THE DISSIPATIVE QUANTUM MODEL OF BRAIN

2004 ◽  
Vol 18 (06) ◽  
pp. 841-858 ◽  
Author(s):  
ELIANO PESSA ◽  
GIUSEPPE VITIELLO
Keyword(s):  
Degrees Of Freedom ◽  
Quantum Noise ◽  
Random Force ◽  
Quantum Model ◽  
Infinite Volume ◽  
Quantum Dissipation ◽  
Memory Space ◽  
Volume Limit ◽  
System Ground State ◽  
Infinite Volume Limit

We discuss some features of the dissipative quantum model of brain in the frame of the formalism of quantum dissipation. Such a formalism is based on the doubling of the system degrees of freedom. We show that the doubled modes account for the quantum noise in the fluctuating random force in the system-environment coupling. Remarkably, such a noise manifests itself through the coherent structure of the system ground state. The entanglement of the system modes with the doubled modes is shown to be permanent in the infinite volume limit. In such a limit the trajectories in the memory space are classical chaotic trajectories.

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