Now showing items 8-27 of 51

    • Effective self-similar expansion for the Gross-Pitaevskii equation 

      Modugno M.; Pagnini G.; Valle-Basagoiti M. A. (Physical Review A, 2018-04)
      We consider an effective scaling approach for the free expansion of a one-dimensional quantum wave packet, consisting in a self-similar evolution to be satisfied on average, i.e., by integrating over the coordinates. A ...
    • 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 ...
    • 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 ...
    • Fractional kinetics emerging from ergodicity breaking in random media 

      Molina-Garcia D.; Minh Pham T.; Paradisi P.; Manzo C.; Pagnini G. (Physical Review E, 2016)
      We present a modelling approach for diffusion in a complex medium characterized by a random lengthscale. The resulting stochastic process shows subdiffusion with a behavior in qualitative agreement with single particle ...
    • 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 relaxation with time-varying coefficient 

      Garra R.; Giusti A.; Mainardi F.; Pagnini G. (Fractional Calculus and Applied Analysis, 2014-12-31)
      From the point of view of the general theory of the hyper-Bessel operators, we consider a particular operator that is suitable to generalize the standard process of relaxation by taking into account both memory effects of ...
    • From G - Equation to Michelson - Sivashinsky Equation in Turbulent Premixed Combustion Modelling 

      Pagnini G. (Proceedings/Extended Abstract Book (6 pages) of the XXXIX Meeting of the Italian Section of the Combustion Institute, Naples, Italy, 2017-06-20)
      It is well known that the Michelson-Sivashinky equation describes hydrodynamic instabilities in turbulent premixed combustion. Here a formulation of the flame front propagation based on the G-equation and on stochastic ...
    • Front Curvature Evolution and Hydrodynamics Instabilities 

      Pagnini G.; Trucchia A. (Proceedings/Extended Abstract Book (6 pages) of the XXXX Meeting of the Italian Section of the Combustion Institute, Rome, Italy, 2017-06-07)
      It is known that hydrodynamic instabilities in turbulent premixed combustion are described by the Michelson-Sivashinsky (MS) equation. A model of the flame front propagation based on the G-equation and on stochastic ...
    • Front propagation in anomalous diffusive media governed by time-fractional diffusion 

      Mentrelli A.; Pagnini G. (Journal of Computational Physics, 2014-12-31)
      In this paper, a multi-dimensional model is proposed to study the propagation of random fronts in media in which anomalous diffusion takes place. The front position is obtained as the weighted mean of fronts calculated by ...
    • 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 ...
    • 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 ...
    • 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 ...
    • Langevin equation in complex media and anomalous diffusion 

      Vitali S.; Sposini V.; Sliusarenko O.; Paradisi P.; Castellani G.; Pagnini G. (Journal of the Royal Society Interface, 2018-07-30)
      The problem of biological motion is a very intriguing and topical issue. Many efforts are being focused on the development of novel modelling approaches for the description of anomalous diffusion in biological systems, such ...
    • 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 ...
    • Modeling of birth-death and diffusion processes in biological complex environments 

      Vitali S. (2018-04-20)
      This thesis is centered on the theory of stochastic processes and their applications in biological systems characterized by a complex environment. Three case studies have been modeled by the use of the three fundamental ...
    • Modelling and simulation of wildland fire in the framework of the level set method 

      Mentrelli A.; Pagnini G. (Ricerche di Matematica, 2016-01-01)
      Among the modelling approaches that have been proposed for the simulation of wildfire propagation, two have gained considerable attention in recent years: the one based on a reaction-diffusion equation, and the one based ...
    • Modelling wildland fire propagation by tracking random fronts 

      Pagnini G.; Mentrelli A. (Natural Hazards and Earth System Sciences, 2014-12-31)
      Abstract. Wildland fire propagation is studied in the liter- ature by two alternative approaches, namely the reaction– diffusion equation and the level-set method. These two ap- proaches are considered alternatives to each ...