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+34 946 567 842
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+34 946 567 842
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gpagnini@bcamath.org
Information of interest
 Orcid: 0000000199174614
My scientific interests concern in a wide sense both turbulent dispersion and anomalous diffusion.
For what concerns turbulent mixing, my research activities are devoted to the Lagrangian features of turbulence with applications to environmental problems and turbulent premixed combustion, as well as to fundamental issues. In particular they are focused on the modelling of the absolute and the relative dispersion by means of nonlinear stochastic differential equations and on turbulent reacting flows by including the levelset method.
For what concerns anomalous diffusion, my research activities are driven in the framework of Fractional Calculus and focused on the socalled fractional diffusion. In particular they require tools and methods belonging to the integral transform theories and to the field of the socalled Special Functions and involve L�vy stable densities.

Preasymptotic analysis of Lévy flights
(2024)We study the properties of Lévy flights with index 0 < α < 2 at elapsed times smaller than those required for reaching the diffusive limit and we focus on the bulk of the walkers’ distribution rather than on its tails. ...

Sturm–Liouville systems for the survival probability in firstpassage time problems
(20231115)We derive a Sturm–Liouville system of equations for the exact calculation of the survival probability in firstpassage time problems. This system is the one associated with the Wiener–Hopf integral equation obtained from ...

Firespotting modelling in operational wildfire simulators based on cellular automata: a comparison study
(20230731)One crucial mechanism in the spread of wildfires is the socalled firespotting: a random phenomenon which occurs when embers are transported over large distances. Firespotting speeds up the Rate of Spread and starts new ...

Predicting the arrival of the unpredictable: An approach for foreseeing the transition to chaos of wildfire propagation
(20230707)A discrete map for modelling wildfire propagation is derived from a prototypical reactiondiffusion equation for the temperature field. We show that, for a constant fuel concentration at the firefront, the heat transfer ...

WienerHopf Integral Equations in Mean Firstpassage Time Problems for Continuoustime Random Walks
(2023)We study the mean firstpassage time (MFPT) for asymmetric continuous time random walks in continuous space characterised by finite mean waiting times and jump amplitudes with both finite average and finite variance. We ...

Firespotting modelling in operational wildfire simulators based on Cellular Automata: A comparison study
(2023)One crucial mechanism in the spread of wildfires is the socalled firespotting: a random phenomenon that occurs when embers are transported over large distances. Firespotting speeds up the rate of spread and starts new ...

The tempered spacefractional Cattaneo equation
(2023)We consider the timefractional Cattaneo equation involving the tempered Caputo spacefractional derivative. There is an increasing interest in the recent literature for the applications of the fractionaltype Cattaneo ...

Exact calculation of the mean firstpassage time of continuoustime random walks by nonhomogeneous WienerHopf integral equations
(20221223)We study the mean firstpassage time (MFPT) for asymmetric continuoustime random walks in continuousspace characterised by waitingtimes with finite mean and by jumpsizes with both finite mean and finite variance. In ...

Firespotting generated fires. Part II: The role of flame geometry and slope
(2022)This is the second part of a series of two papers concerning firespotting generated fires. While, in the first part, we focus on the impact of macroscale factors on the growth of the burning area by considering the ...

Anomalous diffusion originated by two Markovian hoppingtrap mechanisms
(2022)We show through intensive simulations that the paradigmatic features of anomalous diffusion are indeed the features of a (continuoustime) random walk driven by two different Markovian hoppingtrap mechanisms. If $p ...

A highresolution fuel type mapping procedure based on satellite imagery and neural networks: Updating fuel maps for wildfire simulators
(2022)A major limitation in the simulation of forest fires involves the proper characterization of the surface vegetation over the study area, based on land cover maps. Unfortunately, these maps may be outdated, with areas where ...

The Fokker–Planck equation of the superstatistical fractional Brownian motion with application to passive tracers inside cytoplasm
(2022)By collecting from literature data experimental evidence of anomalous diffusion of passive tracers inside cytoplasm, and in particular of subdiffusion of mRNA molecules inside live Escherichia coli cells, we obtain the ...

The tempered spacefractional Cattaneo equation
(2022)We consider the timefractional Cattaneo equation involving the tempered Caputo spacefractional derivative. There is an increasing interest in the recent literature for the applications of the fractionaltype Cattaneo ...

The FokkerPlanck equation of the superstatistical fractional Brownian motion with application to passive tracers inside cytoplasm.
(2022)By collecting from literature data the experimental evidences of anomalous diffusion of passive tracers inside cytoplasm, and in particular of subdiffusion of mRNA molecules inside live E. coli cells, we get the probability ...

Fractional Diffusion and Medium Heterogeneity: The Case of the Continuos Time Random Walk
(20210724)In this contribution we show that fractional diffusion emerges from a simple Markovian Gaussian random walk when the medium displays a powerlaw heterogeneity. Within the framework of the continuous time random walk, the ...

Study of Wound Healing Dynamics by Single PseudoParticle Tracking in Phase Contrast Images Acquired in TimeLapse
(202103)Cellular contacts modify the way cells migrate in a cohesive group with respect to a free single cell. The resulting motion is persistent and correlated, with cells’ velocities selfaligning in time. The presence of a dense ...

SHOULD I STAY OR SHOULD I GO? ZEROSIZE JUMPS IN RANDOM WALKS FOR LÉVY FLIGHTS
(202102)We study Markovian continuoustime random walk models for Lévy flights and we show an example in which the convergence to stable densities is not guaranteed when jumps follow a bimodal powerlaw distribution that is equal ...

Firespotting modelling in operational wildfire simulators based on cellular automata: a comparison study.
(2021)One crucial mechanism in the spread of wildfires is the socalled firespotting: a random phenomenon which occurs when embers are transported over large distances. Firespotting speeds up the Rate of Spread and starts ...

A generalized Stefan model accounting for system memory and nonlocality
(202005)The Stefan problem, involving the tracking of an evolving phasechange 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 ...

Gaussian processes in complex media: new vistas on anomalous diffusion
(201909)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 ...

Finiteenergy Lévytype motion through heterogeneous ensemble of Brownian particles
(20190201)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 ...

On the merits of sparse surrogates for global sensitivity analysis of multiscale nonlinear problems: Application to turbulence and firespotting model in wildland fire simulators
(201902)Many nonlinear phenomena, whose numerical simulation is not straightforward, depend on a set of parameters in a way which is not easy to predict beforehand. Wildland fires in presence of strong winds fall into this category, ...

Firespotting generated fires. Part I: The role of atmospheric stability
(201902)This is the first part of two papers concerning firespotting 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
(201902)Fractional Brownian motion (FBM) is a Gaussian stochastic process with stationary, longtime correlated increments and is frequently used to model anomalous diffusion processes. We study numerically FBM confined to a finite ...

Restoring property of the MichelsonSivashinsky equation
(2019)In this paper we propose a derivation of the MichelsonSivashinsky (MS) equation that is based on front propagation only, in opposition to the classical derivation based also on the flow field. Hence, the characteristics ...

Fractional kinetics in random/complex media
(2019)In this chapter, we consider a randomlyscaled 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 ...

RandomFront 2.3 A physical parametrisation of firespotting for operational fire spread models: Implementation in WRFSfire and response analysis with LSFire+
(201812)Firespotting is often responsible for a dangerous flare up in the wildfire and causes secondary ignitions isolated from the primary fire zone leading to perilous situations. The main aim of the present research to provide ...

Centreofmass like superposition of OrnsteinUhlenbeck processes: A pathway to nonautonomous stochastic differential equations and to fractional diffusion
(20181025)We consider an ensemble of Ornstein–Uhlenbeck processes featuring a population of relaxation times and a population of noise amplitudes that characterize the heterogeneity of the ensemble. We show that the centreofmass ...

Crossover from anomalous to normal diffusion: truncated powerlaw noise correlations and applications to dynamics in lipid bilayers
(20181018)The emerging diffusive dynamics in many complex systems shows a characteristic crossover behaviour from anomalous to normal diffusion which is otherwise fitted by two independent powerlaws. A prominent example for a ...

Langevin equation in complex media and anomalous diffusion
(20180730)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 ...

The role of the environment in front propagation
(20180709)In this work we study the role of a complex environment in the propagation of a front with curvaturedependent speed. The motion of the front is split into a drifting part and a fluctuating part. The drifting part is ...

Quasiprobability Approach for Modelling Local Extinction and Countergradient in Turbulent Premixed Combustion
(20180523)In opposition to standard probability distributions, quasiprobability distributions can have negative values which highlight nonclassical properties of the corresponding system. In quantum mechanics, such negative values ...

Random diffusivity from stochastic equations: comparison of two models for Brownian yet nonGaussian diffusion
(201804)A considerable number of systems have recently been reported in which Brownian yet nonGaussian dynamics was observed. These are processes characterised by a linear growth in time of the mean squared displacement, yet the ...

Effective selfsimilar expansion for the GrossPitaevskii equation
(201804)We consider an effective scaling approach for the free expansion of a onedimensional quantum wave packet, consisting in a selfsimilar evolution to be satisfied on average, i.e., by integrating over the coordinates. A ...

Concurent multiscale physical parametrization of firespotting: A study on the role of macro and mesoscale characteristics of the system
(2018)The strong impact of wildfires in terms of lives and homes lost and of damage to ecosystems, calls for an urgent improvement in the risk management. The aim of the present research is the improvement of these software ...

Wildfire propagation modelling
(2018)Wildfires are a concrete problem with a strong impact on human life, property and the environment, because they cause disruption and are an important source of pollutants. Climate change and ...

Wildland fire propagation modelling
(201712)Wildfire propagation modelling is a challenging problem due to its complex multiscale multiphysics nature. This process can be described by a reaction diffusion equation based on the energy balance principle. Alternative ...

Wildland fire propagation modeling: firespotting parametrisation and energy balance
(20170704)Present research concerns the physical background of a wildfire propagation model based on the split of the front motion into two parts  drifting and fluctuating. The drifting part is solved by the level set method and ...

From G  Equation to Michelson  Sivashinsky Equation in Turbulent Premixed Combustion Modelling
(20170620)It is well known that the MichelsonSivashinky equation describes hydrodynamic instabilities in turbulent premixed combustion. Here a formulation of the flame front propagation based on the Gequation and on stochastic ...

Front Curvature Evolution and Hydrodynamics Instabilities
(20170607)It is known that hydrodynamic instabilities in turbulent premixed combustion are described by the MichelsonSivashinsky (MS) equation. A model of the flame front propagation based on the Gequation and on stochastic ...

Discretizations of the spectral fractional Laplacian on general domains with Dirichlet, Neumann, and Robin boundary conditions
(20170428)In this work, we propose novel discretisations of the spectral fractional Laplacian on bounded domains based on the integral formulation of the operator via the heatsemigroup formalism. Specifically, we combine suitable ...

DarrieusLandau instabilities in the framework of the Gequation
(201704)We consider a model formulation of the flame front propagation in turbulent premixed combustion based on stochastic fluctuations imposed to the mean flame position. In particular, the mean flame motion is described by ...

Turbulence and firespotting effects into wildland fire simulators
(20160101)This paper presents a mathematical approach to model the effects and the role of phenomena with random nature such as turbulence and firespotting into the existing wildfire simulators. The formulation proposes that the ...

Modelling and simulation of wildland fire in the framework of the level set method
(20160101)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 reactiondiffusion equation, and the one based ...

Fractional kinetics emerging from ergodicity breaking in random media
(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 ...

Modelling wildland fire propagation by tracking random fronts
(20141231)Abstract. Wildland fire propagation is studied in the liter ature by two alternative approaches, namely the reaction– diffusion equation and the levelset method. These two ap proaches are considered alternatives to each ...

Selfsimilar stochastic models with stationary increments for symmetric spacetime fractional diffusion
(20141231)An approach to develop stochastic models for studying anomalous diffusion is proposed. In particular, in this approach the stochastic particle trajectory is based on the fractional Brownian motion but, for any realization, ...

Short note on the emergence of fractional kinetics
(20141231)In the present Short Note an idea is proposed to explain the emergence and the observation of processes in complex media that are driven by fractional nonMarkovian master equations. Particle trajectories are assumed to ...

Front propagation in anomalous diffusive media governed by timefractional diffusion
(20141231)In this paper, a multidimensional 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 ...

Fractional relaxation with timevarying coefficient
(20141231)From the point of view of the general theory of the hyperBessel operators, we consider a particular operator that is suitable to generalize the standard process of relaxation by taking into account both memory effects of ...

Twoparticle anomalous diffusion: Probability density functions and selfsimilar stochastic processes
(20131231)Twoparticle dispersion is investigated in the context of anomalous diffusion. Two different modeling approaches related to time subordination are considered and unified in the framework of selfsimilar stochastic processes. ...

The MWright function as a generalization of the Gaussian density for fractional diffusion processes
(20131231)The leading role of a special function of the Wrighttype, referred to as MWright or Mainardi function, within a parametric class of selfsimilar stochastic processes with stationary increments, is surveyed. This class ...
Date  Title  Place  
20130226  BCAM Workshop Environmental Mathematics Day  BCAM  Basque Center for Applied Mathematics, Bilbao, Basque Country  Spain  
20130122 

Department of Mathematics, University of Bologna, Italy 