Recent Submissions

  • The random diffusivity approach for diffusion in heterogeneous systems 

    Sposini V. (2020-12-16)
    The two hallmark features of Brownian motion are the linear growth $\langle x^2(t) \rangle = 2 D d t$ of the mean squared displacement (MSD) with diffusion coefficient $D$ in $d$ spatial dimensions, and the Gaussian ...
  • Gut microbiota ecology: Biodiversity estimated from hybrid neutral-niche model increases with health status and aging 

    Sala C.; Giampieri E.; Vitali S.; Garagnani P.; Remondini D.; Bazzani A.; Franceschi C.; Castellani G. (Plos One, 2020-10-30)
    In this work we propose an index to estimate the gut microbiota biodiversity using a modeling approach with the aim of describing its relationship with health and aging. The gut microbiota, a complex ecosystem that links ...
  • Universal spectral features of different classes of random diffusivity processes 

    Sposini V.; Grebenkov D.S.; Metzler R.; Oshanin G.; Seno F. (New Journal of Physics, 2020-06-26)
    Stochastic models based on random diffusivities, such as the diffusing- diffusivity approach, are popular concepts for the description of non-Gaussian diffusion in heterogeneous media. Studies of these models typically ...
  • A generalized Stefan model accounting for system memory and non-locality 

    Garra R.; Falcini F.; Voller V.R.; Pagnini G. (International Communications in Heat and Mass Transfer, 2020-05)
    The Stefan problem, involving the tracking of an evolving phase-change front, is the prototypical example of a moving boundary problem. In basic one- dimensional problems it is well known that the front advances as the ...
  • A hypothesis about parallelism vs. seriality in dreams 

    Barcaro U.; Paradisi P.; Sebastiani L. (Front. Psychol., 2019-10-10)
    The current article discusses the hypothesis about parallelism vs. Seriality in dreams. The process of dream building implies the construction of a complex network of closely interrelated sources. On the other hand, the ...
  • Gaussian processes in complex media: new vistas on anomalous diffusion 

    Di Tullio F.; Paradisi P.; Spigler R.; Pagnini G. (Front. Phys., 2019-09)
    Normal or Brownian diffusion is historically identified by the linear growth in time of the variance and by a Gaussian shape of the displacement distribution. Processes departing from the at least one of the above conditions ...
  • Front Propagation in Random Media 

    Trucchia A. (2019)
    This PhD thesis deals with the problem of the propagation of fronts under random circumstances. A statistical model to represent the motion of fronts when are evolving in a media characterized by microscopical randomness ...
  • Stochastic processes for anomalous diffusion 

    Molina-Garcia D. (2019)
    Anomalous diffusion is a diffusion process which Mean Square Displacement (MSD) is not a linear funtion of time, what is known as normal diffusion. When the relation is faster than linear, it is called superdiffusion and ...
  • Single-trajectory spectral analysis of scaled Brownian motion 

    Sposini V.; Metzler R.; Oshanin G. (New Journal of Physics, 2019-06)
    A standard approach to study time-dependent stochastic processes is the power spectral density (PSD), an ensemble-averaged property defined as the Fourier transform of the autocorrelation function of the process in the ...
  • Reduced description method in the kinetic theory of Brownian motion with active fluctuations 

    Sliusarenko O.; Sliusarenko Y. (Journal of Physics A: Mathematical and Theoretical, 2019-09-01)
    We develop a microscopic approach to the kinetic theory of many-particle systems with dissipative and potential interactions in presence of active fluctuations. The approach is based on a generalization of Bogolyubov–Peletminskii ...
  • On the propagation of nonlinear transients of temperature and pore pressure in a thin porous boundary layer between two rocks. 

    Salusti E.; Kanivetsky R.; Droghei R.; Garra R. (Journal of Hydrology, 2019)
    The dynamics of transients of fluid-rock temperature, pore pressure, pollutants in porous rocks are of vivid interest for fundamental problems in hydrological, volcanic, hydrocarbon systems, deep oil drilling. This can ...
  • Restoring property of the Michelson-Sivashinsky equation 

    Trucchia A.; Pagnini G. (Combustion Science and Technology, 2019)
    In this paper we propose a derivation of the Michelson-Sivashinsky (MS) equation that is based on front propagation only, in opposition to the classical derivation based also on the flow field. Hence, the characteristics ...
  • Stochastic spatial models in ecology: a statistical physics approach 

    Pigolotti S.; Cencini M.; Molina-Garcia D.; Muñoz M.A. (Journal of Statistical Physics, 2017-11-21)
    Ecosystems display a complex spatial organization. Ecologists have long tried to characterize them by looking at how different measures of biodiversity change across spatial scales. Ecological neutral theory has provided ...
  • Fractional kinetics in random/complex media 

    Pagnini G. (Handbook of Fractional Calculus with Applications Volume 5 Applications in Physics, Part B, 2019)
    In this chapter, we consider a randomly-scaled Gaussian process and discuss a number of applications to model fractional diffusion. Actually, this approach can be understood as a Gaussian diffusion in a medium characterized ...
  • Fractional Brownian motion in a finite interval: correlations effect depletion or accretion zones of particles near boundaries 

    Guggenberger T.; Pagnini G.; Vojta T.; Metzler R. (New Journal of Physics, 2019-02)
    Fractional Brownian motion (FBM) is a Gaussian stochastic process with stationary, long-time correlated increments and is frequently used to model anomalous diffusion processes. We study numerically FBM confined to a finite ...
  • Surrogate-based uncertainty and sensitivity analysis for bacterial invasion in multi-species biofilm modeling 

    Trucchia A.; Mattei M.R.; Luongo V.; Frunzo L.; Rochoux M.C. (Communications Nonlinear Sciences and Numerical Simulation, 2019)
    In this work, we present a probabilistic analysis of a detailed one-dimensional biofilm model that explicitly accounts for planktonic bacterial invasion in a multi-species biofilm. The objective is (1) to quantify and ...
  • Finite-energy Lévy-type motion through heterogeneous ensemble of Brownian particles 

    Sliusarenko O.; Vitali S.; Sposini V.; Paradisi P.; Chechkin A.V.; Castellani G.; Pagnini G. (Journal of Physics A: Mathematical and Theoretical, 2019-02-01)
    Complex systems are known to display anomalous diffusion, whose signature is a space/time scaling $x \sim t^\delta$ with $\delta \neq 1/2$ in the probability density function (PDF). Anomalous diffusion can emerge jointly ...
  • Fire-spotting generated fires. Part I: The role of atmospheric stability 

    Egorova V.; Trucchia A.; Pagnini G. (Applied Mathematical Modelling, 2019-02)
    This is the first part of two papers concerning fire-spotting generated fires. In this part we deal with the impact of macroscale factors, such as the atmospheric stability, and in the second part we deal with mesoscale ...
  • Modeling anomalous heat diffusion: Comparing fractional derivative and non-linear diffusivity treatments 

    Falcini F.; Garra R.; Voller V. (International Journal of Thermal Sciences, 2018-11)
    In the Fourier heat conduction equation, when the flux definition is expressed as the product of a constant diffusivity and the temperature gradient, the characteristic length scale evolves as the square root of time. ...
  • Modeling non-stationarities in high-frequency financial time series 

    Ponta L.; Trinh M.; Raberto M.; Scalas E.; Cincotti S. (Physica A: Statistical Mechanics and its Applications, 2019-01)
    We study tick-by-tick financial returns for the FTSE MIB index of the Italian Stock Exchange (Borsa Italiana). We confirm previously detected non-stationarities. Scaling properties reported before for other high-frequency ...

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