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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: 0000-0001-9917-4614
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 level-set method.
For what concerns anomalous diffusion, my research activities are driven in the framework of Fractional Calculus and focused on the so-called fractional diffusion. In particular they require tools and methods belonging to the integral transform theories and to the field of the so-called Special Functions and involve L�vy stable densities.
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Pre-asymptotic analysis of Lévy flights
Pagnini, G.
; Araújo, H. (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. ...
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Sturm–Liouville systems for the survival probability in first-passage time problems
Pagnini, G.; Dahlenburg, M. (2023-11-15)
We derive a Sturm–Liouville system of equations for the exact calculation of the survival probability in first-passage time problems. This system is the one associated with the Wiener–Hopf integral equation obtained from ...
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Fire-spotting modelling in operational wildfire simulators based on cellular automata: a comparison study
López-De-Castro, M; Trucchia, A.; Morra di Cella, U; Fiorucci, P; Cardillo, A; Pagnini, G. (2023-07-31)
One crucial mechanism in the spread of wildfires is the so-called fire-spotting: a random phenomenon which occurs when embers are transported over large distances. Fire-spotting speeds up the Rate of Spread and starts new ...
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Predicting the arrival of the unpredictable: An approach for foreseeing the transition to chaos of wildfire propagation
Mampel, J.; Egorova, V.; Pagnini, G. (2023-07-07)
A discrete map for modelling wildfire propagation is derived from a prototypical reaction-diffusion equation for the temperature field. We show that, for a constant fuel concentration at the fire-front, the heat transfer ...
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Wiener-Hopf Integral Equations in Mean First-passage Time Problems for Continuous-time Random Walks
Dahlenburg, M.; Pagnini, G. (2023)
We study the mean first-passage 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 ...
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Fire-spotting modelling in operational wildfire simulators based on Cellular Automata: A comparison study
López-De-Castro, M; Trucchia, A.; Morra di Cella, U; Fiorucci, P; Cardillo, A; Pagnini, G. (2023)
One crucial mechanism in the spread of wildfires is the so-called fire-spotting: a random phenomenon that occurs when embers are transported over large distances. Fire-spotting speeds up the rate of spread and starts new ...
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The tempered space-fractional Cattaneo equation
Beghin, L.; Garra, R.; Mainardi, F.; Pagnini, G. (2023)
We consider the time-fractional Cattaneo equation involving the tempered Caputo space-fractional derivative. There is an increasing interest in the recent literature for the applications of the fractional-type Cattaneo ...
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Exact calculation of the mean first-passage time of continuous-time random walks by nonhomogeneous Wiener-Hopf integral equations
Dahlenburg, M.; Pagnini, G. (2022-12-23)
We study the mean first-passage time (MFPT) for asymmetric continuous-time random walks in continuous-space characterised by waiting-times with finite mean and by jump-sizes with both finite mean and finite variance. In ...
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Fire-spotting generated fires. Part II: The role of flame geometry and slope
Egorova, V.; Trucchia, A.; Pagnini, G. (2022)
This is the second part of a series of two papers concerning fire-spotting generated fires. While, in the first part, we focus on the impact of macro-scale factors on the growth of the burning area by considering the ...
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Anomalous diffusion originated by two Markovian hopping-trap mechanisms
Vitali, S.; Paradisi, P.; Pagnini, G. (2022)
We show through intensive simulations that the paradigmatic features of anomalous diffusion are indeed the features of a (continuous-time) random walk driven by two different Markovian hopping-trap mechanisms. If $p ...
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A high-resolution fuel type mapping procedure based on satellite imagery and neural networks: Updating fuel maps for wildfire simulators
López-De-Castro, M.; Prieto-Herráez, D.; Asensio-Sevilla, M.I.; Pagnini, G. (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 ...
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The Fokker–Planck equation of the superstatistical fractional Brownian motion with application to passive tracers inside cytoplasm
Runfola, C.; Vitali, S.; Pagnini, G. (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 ...
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The tempered space-fractional Cattaneo equation
Beghin, L.; Garra, R.; Mainardi, F.; Pagnini, G. (2022)
We consider the time-fractional Cattaneo equation involving the tempered Caputo space-fractional derivative. There is an increasing interest in the recent literature for the applications of the fractional-type Cattaneo ...
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The Fokker-Planck equation of the superstatistical fractional Brownian motion with application to passive tracers inside cytoplasm.
Runfola, C.; Vitali, S.; Pagnini, G. (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 ...
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Fractional Diffusion and Medium Heterogeneity: The Case of the Continuos Time Random Walk
Sposini, V.; Vitali, S.; Paradisi, P.; Pagnini, G. (2021-07-24)
In this contribution we show that fractional diffusion emerges from a simple Markovian Gaussian random walk when the medium displays a power-law heterogeneity. Within the framework of the continuous time random walk, the ...
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Study of Wound Healing Dynamics by Single Pseudo-Particle Tracking in Phase Contrast Images Acquired in Time-Lapse
Scheda, R.; Vitali, S.; Giampieri, E.; Pagnini, G.; Zironi, I. (2021-03)
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 self-aligning in time. The presence of a dense ...
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SHOULD I STAY OR SHOULD I GO? ZERO-SIZE JUMPS IN RANDOM WALKS FOR LÉVY FLIGHTS
Pagnini, G.; Vitali, S. (2021-02)
We study Markovian continuous-time 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 bi-modal power-law distribution that is equal ...
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Fire-spotting modelling in operational wildfire simulators based on cellular automata: a comparison study.
López-De-Castro, M; Trucchia, A.; Morra di Cella, U; Fiorucci, P; Cardillo, A; Pagnini, G. (2021)
One crucial mechanism in the spread of wildfires is the so-called fire-spotting: a random phenomenon which occurs when embers are transported over large distances. Fire-spotting speeds up the Rate of Spread and starts ...
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A generalized Stefan model accounting for system memory and non-locality
Garra, R.; Falcini, F.; Voller, V.R.; Pagnini, G. (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 ...
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Gaussian processes in complex media: new vistas on anomalous diffusion
Di Tullio, F.; Paradisi, P.; Spigler, R.; Pagnini, G. (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 ...
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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. (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 ...
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On the merits of sparse surrogates for global sensitivity analysis of multi-scale nonlinear problems: Application to turbulence and fire-spotting model in wildland fire simulators
Trucchia, A.; Egorova, V.; Pagnini, G.; Rochoux, M.C. (2019-02)
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, ...
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Fire-spotting generated fires. Part I: The role of atmospheric stability
Egorova, V.; Trucchia, A.; Pagnini, G. (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 ...
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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. (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 ...
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Restoring property of the Michelson-Sivashinsky equation
Trucchia, A.; Pagnini, G. (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 ...
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Fractional kinetics in random/complex media
Pagnini, G. (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 ...
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RandomFront 2.3 A physical parametrisation of fire-spotting for operational fire spread models: Implementation in WRF-Sfire and response analysis with LSFire+
Trucchia, A.; Egorova, V.; Butenko, A.; Kaur, I.; Pagnini, G. (2018-12)
Fire-spotting 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 ...
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Centre-of-mass like superposition of Ornstein-Uhlenbeck processes: A pathway to non-autonomous stochastic differential equations and to fractional diffusion
D’Ovidio, M.; Vitali, S.; Sposini, V.; Sliusarenko, O.; Paradisi, P.; Castellani, G.; Pagnini, G. (2018-10-25)
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 centre-of-mass ...
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Crossover from anomalous to normal diffusion: truncated power-law noise correlations and applications to dynamics in lipid bilayers
Molina-Garcia, D.; Sandev, T.; Safdari, H.; Pagnini, G.; Chechkin, A.V.; Metzler, R. (2018-10-18)
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 power-laws. A prominent example for a ...
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Langevin equation in complex media and anomalous diffusion
Vitali, S.; Sposini, V.; Sliusarenko, O.; Paradisi, P.; Castellani, G.; Pagnini, G. (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 ...
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The role of the environment in front propagation
Trucchia, A.; Pagnini, G. (2018-07-09)
In this work we study the role of a complex environment in the propagation of a front with curvature-dependent speed. The motion of the front is split into a drifting part and a fluctuating part. The drifting part is ...
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Quasi-probability Approach for Modelling Local Extinction and Counter-gradient in Turbulent Premixed Combustion
Pagnini, G.; Trucchia, A. (2018-05-23)
In opposition to standard probability distributions, quasi-probability distributions can have negative values which highlight nonclassical properties of the corresponding system. In quantum mechanics, such negative values ...
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Random diffusivity from stochastic equations: comparison of two models for Brownian yet non-Gaussian diffusion
Sposini, V.; Chechkin, A.V.; Seno, F.; Pagnini, G.; Metzler, R. (2018-04)
A considerable number of systems have recently been reported in which Brownian yet non-Gaussian dynamics was observed. These are processes characterised by a linear growth in time of the mean squared displacement, yet the ...
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Effective self-similar expansion for the Gross-Pitaevskii equation
Modugno, M.; Pagnini, G.; Valle-Basagoiti, M.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 ...
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Concurent multi-scale physical parametrization of fire-spotting: A study on the role of macro- and meso-scale characteristics of the system
Egorova, V.; Trucchia, A.; Pagnini, G. (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 ...
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Wildfire propagation modelling
Pagnini, G.; Egorova, V.; Trucchia, A.; Mentrelli, A.; Kaur, I. (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 ...
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Wildland fire propagation modelling
Egorova, V.; Pagnini, G.; Trucchia, A. (2017-12)
Wildfire propagation modelling is a challenging problem due to its complex multi-scale multi-physics nature. This process can be described by a reaction- diffusion equation based on the energy balance principle. Alternative ...
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Wildland fire propagation modeling: fire-spotting parametrisation and energy balance
Egorova, V.; Pagnini, G.; Trucchia, A. (2017-07-04)
Present research concerns the physical background of a wild-fire 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 ...
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From G - Equation to Michelson - Sivashinsky Equation in Turbulent Premixed Combustion Modelling
Pagnini, G. (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 ...
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Front Curvature Evolution and Hydrodynamics Instabilities
Pagnini, G.; Trucchia, A. (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 ...
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Discretizations of the spectral fractional Laplacian on general domains with Dirichlet, Neumann, and Robin boundary conditions
Cusimano, N.; Del Teso, F.; Gerardo-Giorda, L.; Pagnini, G. (2017-04-28)
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 heat-semigroup formalism. Specifically, we combine suitable ...
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Darrieus-Landau instabilities in the framework of the G-equation
Pagnini, G.; Trucchia, A. (2017-04)
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 ...
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Turbulence and fire-spotting effects into wild-land fire simulators
Kaur, I.; Mentrelli, A.; Bosseur, F.; Filippi, J.-B.; Pagnini, G. (2016-01-01)
This paper presents a mathematical approach to model the effects and the role of phenomena with random nature such as turbulence and fire-spotting into the existing wildfire simulators. The formulation proposes that the ...
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Modelling and simulation of wildland fire in the framework of the level set method
Mentrelli, A.; Pagnini, G. (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 ...
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Fractional kinetics emerging from ergodicity breaking in random media
Molina-Garcia, D.; Minh Pham, T.; Paradisi, P.; Manzo, C.; Pagnini, G. (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 ...
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Modelling wildland fire propagation by tracking random fronts
Pagnini, G.; Mentrelli, A. (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 ...
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Self-similar stochastic models with stationary increments for symmetric space-time fractional diffusion
Pagnini, G. (2014-12-31)
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, ...
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Short note on the emergence of fractional kinetics
Pagnini, G. (2014-12-31)
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 non-Markovian master equations. Particle trajectories are assumed to ...
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Front propagation in anomalous diffusive media governed by time-fractional diffusion
Mentrelli, A.; Pagnini, G. (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 ...
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Fractional relaxation with time-varying coefficient
Garra, R.; Giusti, A.; Mainardi, F.; Pagnini, G. (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 ...
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Two-particle anomalous diffusion: Probability density functions and self-similar stochastic processes
Pagnini, G.; Mura, A.; Mainardi, F. (2013-12-31)
Two-particle 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 self-similar stochastic processes. ...
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The M-Wright function as a generalization of the Gaussian density for fractional diffusion processes
Pagnini, G. (2013-12-31)
The leading role of a special function of the Wright-type, referred to as M-Wright or Mainardi function, within a parametric class of self-similar stochastic processes with stationary increments, is surveyed. This class ...
| Date | Title | Place | |
| 2013-02-26 | BCAM Workshop Environmental Mathematics Day | BCAM - Basque Center for Applied Mathematics, Bilbao, Basque Country - Spain | |
| 2013-01-22 |
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Department of Mathematics, University of Bologna, Italy |