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UNT College of Arts and Sciences
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Physics
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2000-2009
Event-Driven Power-Law Relaxation in Weak Turbulence
Date: January 5, 2009
Creator: Silvestri, Ludovico; Fronzoni, Leone; Grigolini, Paolo & Allegrini, Paolo
Description: This article discusses event-driven power-law relaxation in weak turbulence. Abstract: We characterize the spectral properties of weak turbulence in a liquid crystal sample driven by an external electric field, as a function of the applied voltage, and we find a 1/f noise spectrum S(f) ∝ 1/fn within the whole range 0< ɳ <2. We theoretically explore the hypothesis that the system complexity is driven by non-Poisson events resetting the system through creation and annihilation of coherent structures, retaining no memory of previous history (crucial events). The authors study the time asymptotic regime by means of the density ψ(τ) of the time distances between two crucial events, yielding ɳ = 3 - μ, where μ is defined through the long-time form ψ(τ) ∝ 1/τµ, with 1 < µ < 3. The system regression to equilibrium after an abrupt voltage change experimentally confirms the theory, proving violations of the ordinary linear response theory for both ɳ > 1 and ɳ < 1.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc40395/
Experimental Quenching of Harmonic Stimuli: Universality of Linear Response Theory
Date: July 15, 2009
Creator: Allegrini, Paolo; Bologna, Mauro; Fronzoni, Leone; Grigolini, Paolo & Silvestri, Ludovico
Description: This article discusses experimental quenching of harmonic stimuli. Abstract: We show that liquid crystals in the weak turbulence electroconvective regime respond to harmonic perturbations with oscillations whose intensity decay with an inverse power law of time. We use the results of this experiment to prove that this effect is the manifestation of a form of linear response theory (LRT) valid in the out-of-equilibrium case, as well as at thermodynamic equilibrium where it reduces to the ordinary LRT. We argue that this theory is a universal property, which is not confined to physical processes such as turbulent or excitable media, and that it holds true in all possible conditions, and for all possible systems, including a complex networks, thereby establishing a bridge between statistical physics and all the fields of research in complexity.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc40394/
A fluctuating environment as a source of periodic modulation
Date: March 2007
Creator: Bianco, Simone; Grigolini, Paolo & Paradisi, Paolo
Description: This article discusses a fluctuating environment as a source of periodic modulation. Abstract: We study the intermittent fluorescence of a single molecule, jumping from the "light on" to the "light off" state, as a Poisson process modulated by a fluctuating environment. We show that the quasi-periodic and quasi-deterministic environmental fluctuations make the distribution of the times of sojourn in the "light off" state depart from the exponential form, and that their succession in time mirrors environmental dynamics. As an illustration, the authors discuss some recent experimental results, where the environmental fluctuations depend on enzymatic activity.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc132981/
Fluctuation-dissipation process without a time scale
Date: May 2000
Creator: Annunziato, Mario; Grigolini, Paolo & Riccardi, Juri
Description: This article discusses fluctuation-dissipation process without a time scale. Abstract: We study the influence of a dissipation process on diffusion dynamics triggered by fluctuations with long-range correlations. We make the assumption that the perturbation process involved is of the same kind as those recently studied numerically and theoretically, with a good agreement between theory and numerical treatment. As a result of this assumption the equilibrium distribution departs from the ordinary canonical distribution. The distribution tails are truncated, the distribution border is signaled by sharp peaks, and, in the weak dissipation limit, the central distribution body becomes identical to a truncated Lévy distribution.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc77161/
Fluctuation-Dissipation Theorem for Event-Dominated Processes
Date: July 6, 2007
Creator: Allegrini, Paolo; Bologna, Mauro; Grigolini, Paolo & West, Bruce J.
Description: This article discusses fluctuation-dissipation theorem for event-dominated processes. Abstract: We study a system whose dynamics are driven by non-Poisson, renewal, and nonergodic events. We show that external perturbations influencing the times at which these events occur violate the standard fluctuation-dissipation prescription due to renewal aging. The fluctuation-dissipation relation of this Letter is shown to be the linear response limit of an exact expression that has been recently proposed to account for the luminescence decay in a Gibbs ensemble of semiconductor nanocrystals, with intermittent fluorescence.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc40397/
From power law intermittence to macroscopic coherent regime
Date: June 25, 2009
Creator: Bologna, Mauro; Budini, Adrián A.; Giraldi, Filippo & Grigolini, Paolo
Description: This article offers discussions from power law intermittence to macroscopic coherent regime. Abstract: We address the problem of establishing which is the proper form of quantum master equation generating a survival probability identical to that corresponding to the nonergodic sequence of "light on" and "light off" fluorescence fluctuations in blinking quantum dots. We adopt a theoretical perspective based on the assumption that the abrupt transitions from the light on to light off state are the results of many collisions between system and environment, properly described by the Linkblad equation, and that between two consecutive collisions the system dynamics are frozen. This generates a quantum master equation belonging to the recently proposed class of generalized Lindblad equations, with a time convoluted structure, involving in the specific case of this paper both the unitary and the nonunitary contribution of the Lindlad equation. This is the property that under the low-frequency condition makes the new class of generalized Lindblad equation generates the required survival probability. We make the conjecture that this equation corresponds to the cooperative dynamics of many units that, in isolation, are described by the ordinary Lindblad equation. When the time scale of the unitary term of the Lindblad equation is ...
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc132992/
Generalized Master Equation Via Aging Continuous-Time Random Walks
Date: 2003
Creator: Allegrini, Paolo; Aquino, Gerardo; Grigolini, Paolo; Palatella, Luigi & Rosa, Angelo
Description: This article discusses generalized master equation via aging continuous-time random walks. Abstract: We discuss the problem of the equivalence between continuous-time random walk (CTRW) and generalized master equation (GME). The walker, making instantaneous jumps from one site of the lattice to another, resides in each site for extended times. The sojourn times have a distribution density ψ(t) that is assumed to be an inverse power law with the power index μ. We assume that the Onsager principle is fulfilled, and we use this assumption to establish a complete equivalence between GME and the Montroll-Weiss CTRW.We prove that this equivalence is confined to the case where ψ(t) is an exponential. We argue that is so because the Montroll-Weiss CTRW, as recently proved by Barkai [E. Barkai, Phys. Rev. Lett. 90, 104101 (2003)], is nonstationary, thereby implying aging, while the Onsager principle is valid only in the case of fully aged systems. The case of a Poisson distribution of sojourn times is the only one with no aging associated to it, and consequently with no need to establish special initial conditions to fulfill the Onsager principle. We consider the case of a dichotomous fluctuation, and we prove that the Onsager principle is ...
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc67635/
Generation of correlated binary sequences from white noise
Date: August 21, 2007
Creator: Izrailev, Felix M.; Krokhin, Arkadii A.; Makarov, N. M. & Usatenko, O. V.
Description: This article discusses the generation of correlated binary sequences from white noise. Abstract: We suggest a method for generation of random binary sequences of elements 0 and 1, with prescribed correlation properties. It is based on a modification of the widely used convolution method of constructing continuous random processes. Using this method, a binary sequence with a power-law decaying pair correlator can be easily generated.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc103260/
High sensitivity measurement of implanted As in the presence of Ge in Ge(x)Si(1-x)/Si layered alloys using trace element accelerator mass spectrometry
Date: December 11, 2000
Creator: Datar, Sameer A.; Wu, Liying; Guo, Baonian N.; Nigam, Mohit; Necsoiu, Daniela; Zhai, Y. J. et al
Description: This article discusses high sensitivity measurement of implanted As in the presence of Ge in Ge(x)Si(1-x)/Si layered alloys using trace element accelerator mass spectrometry. Abstract: Various devices can be realized on strained GeSi/Si substrates by doping the substrate with different impurities such as As. As is an n-type dopant in both Ge and Si. As cross contamination can also arise during germanium preamorphization implantation due to inadequate mass resolution in the implanter. Thus, it is important to be able to accurately measure low-level As concentrations in the presence of Ge. Secondary ion mass spectrometry (SIMS) is the standard technique for these types of measurements but is constrained by mass interferences from molecular ions (⁷⁴GeH, ²⁹Si³⁰Si¹⁶O). The trace element accelerator mass accelerator technique allows the breakup of interfering molecules. As is measured in a GeSi matrix with sensitivity significantly better than SIMS.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc146576/
Homogenization of Magnetodielectric Photonic Crystals
Date: July 9, 2004
Creator: Krokhin, Arkadii A. & Reyes, E.
Description: This article discusses homogenization of magnetodielectric photonic crystals. Abstract: We calculate the low-frequency index of refraction of a medium which is homogeneous along axis z and possesses a periodic dependence of the permittivity ɛ(r) and permeability μ(r) in the x-y plane (2D magnetodielectric photonic crystal). Exact analytical formulas for the effective index of refraction for two eigenmodes with vector E or H polarized along axis z are obtained. We show that, unlike nonmagnetic photonic crystals where the E mode is ordinary and the H mode is extraordinary, now both modes exhibit extraordinary behavior. Because of this distinction, the magnetodielectric photonic crystals exhibit optical properties that do not exist for natural crystals. We also discuss the limiting case of perfectly conducting cylinders and clarify the so-called problem of noncommuting limits, ω → 0 and ɛ → ∞.
Contributing Partner: UNT College of Arts and Sciences
Permallink:digital.library.unt.edu/ark:/67531/metadc107768/