baldassarri baronchelli barrat caglioti castellano cattuto complexity data_compression dattoli evolutionary_dynamics granular_media granular_media herrmann information_theory kreyon language_dynamics loreto mari mukherjee petri pietronero puglisi quantum_optics self_organization servedio statistical_physics techno_social_systems tria zapperi zippers
2000 |
Piccioni, Marina; Loreto, Vittorio; Roux, Stephane Criticality of the ``critical state'' of granular media: Dilatancy angle in the Tetris model Journal Article PHYSICAL REVIEW E, 61 , pp. 2813–2813, 2000. Links | BibTeX | Tags: granular_media, loreto, piccioni, roux, statistical_physics @article{b, title = {Criticality of the ``critical state'' of granular media: Dilatancy angle in the Tetris model}, author = {Marina Piccioni and Vittorio Loreto and Stephane Roux}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000085994000088&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {2000}, date = {2000-01-01}, journal = {PHYSICAL REVIEW E}, volume = {61}, pages = {2813--2813}, publisher = {American Institute of Physics}, keywords = {granular_media, loreto, piccioni, roux, statistical_physics}, pubstate = {published}, tppubtype = {article} } |
Barrat, Alain; Kurchan, Jorge; Loreto, Vittorio; Sellitto, Mauro Edwards' Measures for Powders and Glasses Journal Article PHYSICAL REVIEW LETTERS, 85 , pp. 5034–5037, 2000. Links | BibTeX | Tags: barrat, granular_media, kurchan, loreto, sellitto, statistical_physics @article{b, title = {Edwards' Measures for Powders and Glasses}, author = {Alain Barrat and Jorge Kurchan and Vittorio Loreto and Mauro Sellitto}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000165800000006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {2000}, date = {2000-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {85}, pages = {5034--5037}, publisher = {American Institute of Physics}, keywords = {barrat, granular_media, kurchan, loreto, sellitto, statistical_physics}, pubstate = {published}, tppubtype = {article} } |
Barrat, Alain; Loreto, Vittorio Response properties in a model for granular matter Journal Article JOURNAL OF PHYSICS. A, MATHEMATICAL AND GENERAL, 33 , pp. 4401–4426, 2000. Links | BibTeX | Tags: barrat, granular_media, loreto @article{b, title = {Response properties in a model for granular matter}, author = {Alain Barrat and Vittorio Loreto}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0034705247&partnerID=65&md5=82ed3ead2890ef9da53fc8533cf614c1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000088364500002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {2000}, date = {2000-01-01}, journal = {JOURNAL OF PHYSICS. A, MATHEMATICAL AND GENERAL}, volume = {33}, pages = {4401--4426}, keywords = {barrat, granular_media, loreto}, pubstate = {published}, tppubtype = {article} } |
1999 |
Puglisi, Andrea; Loreto, Vittorio; Bettolo, Umberto Marini; Vulpiani, Angelo A kinetic approach to granular gases Journal Article PHYSICAL REVIEW E, 59 , pp. 5582–5582, 1999. Links | BibTeX | Tags: granular_media, loreto, marini bettolo, puglisi, vulpiani @article{b, title = {A kinetic approach to granular gases}, author = {Andrea Puglisi and Vittorio Loreto and Umberto Marini Bettolo and Angelo Vulpiani}, url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000080382900021&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1999}, date = {1999-01-01}, journal = {PHYSICAL REVIEW E}, volume = {59}, pages = {5582--5582}, publisher = {American Institute of Physics}, keywords = {granular_media, loreto, marini bettolo, puglisi, vulpiani}, pubstate = {published}, tppubtype = {article} } |
Caglioti, Emanuele; Coniglio, Antonio; Hermann, Hans J; Loreto, Vittorio Cooperative lenght approach for granular media Journal Article PHYSICA. A, 265 , pp. 311–318, 1999. Abstract | Links | BibTeX | Tags: caglioti, coniglio, granular_media, herrmann, loreto @article{b, title = {Cooperative lenght approach for granular media}, author = {Emanuele Caglioti and Antonio Coniglio and Hans J. Hermann and Vittorio Loreto}, url = {http://www.sciencedirect.com/science/article/pii/S0378437198006608, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000079060800023&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1999}, date = {1999-01-01}, journal = {PHYSICA. A}, volume = {265}, pages = {311--318}, publisher = {Elsevier B.V.}, abstract = {We analyze the non-equilibrium relaxation properties of granular materials in the perspective of a cooperative length approach of Adam and Gibbs. The existence of complex geometrical interactions between the grains induces a rough landscape in the structure of the allowable phase space and in the configurational entropy. At their turn these effects induce the need of complex cooperative rearrangements which account for the very slow relaxation dynamics of these systems. On this basis we relate quantitatively the characteristic dynamical properties to quasistatic quantities, e.g. free-volume and configurational entropy.}, keywords = {caglioti, coniglio, granular_media, herrmann, loreto}, pubstate = {published}, tppubtype = {article} } We analyze the non-equilibrium relaxation properties of granular materials in the perspective of a cooperative length approach of Adam and Gibbs. The existence of complex geometrical interactions between the grains induces a rough landscape in the structure of the allowable phase space and in the configurational entropy. At their turn these effects induce the need of complex cooperative rearrangements which account for the very slow relaxation dynamics of these systems. On this basis we relate quantitatively the characteristic dynamical properties to quasistatic quantities, e.g. free-volume and configurational entropy. |
Caglioti, Emauele; Loreto, Vittorio Entropy for relaxation dynamics in granular media Journal Article PHYSICAL REVIEW LETTERS, 83 , pp. 4333–4336, 1999. Abstract | Links | BibTeX | Tags: caglioti, granular_media, loreto @article{b, title = {Entropy for relaxation dynamics in granular media}, author = {Emauele Caglioti and Vittorio Loreto}, url = {http://prl.aps.org/abstract/PRL/v83/i21/p4333_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000083745600028&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1999}, date = {1999-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {83}, pages = {4333--4336}, abstract = {We investigate the role of entropic concepts for the relaxation dynamics in granular systems. In these systems the existence of a geometrical frustration induces a drastic modification of the allowed phase space, which in its turn induces a dynamic behavior characterized by hierarchical relaxation phenomena with several time scales associated. In particular we show how, in the framework of a mean-field model introduced for the compaction phenomenon, there exists a free-energy-like functional which decreases along the trajectories of the dynamics and which allows to account for the asymptotic behavior: e.g. density profile, segregation phenomena. Also we are able to perform the continuous limit of the above mentioned model which turns out to be a diffusive limit. In this framework one can single out two separate physical ingredients: the free-energy-like functional that defines the phase-space and the asymptotic states and a diffusion coefficient $D(rho)$ accounting for the velocity of approach to the asymptotic stationary states.}, keywords = {caglioti, granular_media, loreto}, pubstate = {published}, tppubtype = {article} } We investigate the role of entropic concepts for the relaxation dynamics in granular systems. In these systems the existence of a geometrical frustration induces a drastic modification of the allowed phase space, which in its turn induces a dynamic behavior characterized by hierarchical relaxation phenomena with several time scales associated. In particular we show how, in the framework of a mean-field model introduced for the compaction phenomenon, there exists a free-energy-like functional which decreases along the trajectories of the dynamics and which allows to account for the asymptotic behavior: e.g. density profile, segregation phenomena. Also we are able to perform the continuous limit of the above mentioned model which turns out to be a diffusive limit. In this framework one can single out two separate physical ingredients: the free-energy-like functional that defines the phase-space and the asymptotic states and a diffusion coefficient $D(rho)$ accounting for the velocity of approach to the asymptotic stationary states. |
Khrishnamurthy, Supriya; Loreto, Vittorio; Hermmann, Hans J; Nicodemi, Mario; Roux, Stephane Internal avalanches in models of granular media Journal Article FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY, 7 , pp. 51–58, 1999. Abstract | Links | BibTeX | Tags: granular_media, herrmann, khrishnamurthy, loreto, nicodemi, roux @article{b, title = {Internal avalanches in models of granular media}, author = {Supriya Khrishnamurthy and Vittorio Loreto and Hans J. Hermmann and Mario Nicodemi and Stephane Roux}, url = {http://www.worldscinet.com/fractals/07/0701/S0218348X99000074.html, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000081441600006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1999}, date = {1999-01-01}, journal = {FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY}, volume = {7}, pages = {51--58}, abstract = {We study the phenomenon of internal avalanching within the context of recently introduced lattice models of granular media. The avalanche is produced by pulling out a grain at the base of the packing and then studying the number of grains to be rearranged before the packing is stable again. We find that the avalanches are long-ranged, decaying as a power law. We study the distribution of avalanches as a function of the density of the packing and find that the avalanche distribution is a very sensitive structural probe of the system.}, keywords = {granular_media, herrmann, khrishnamurthy, loreto, nicodemi, roux}, pubstate = {published}, tppubtype = {article} } We study the phenomenon of internal avalanching within the context of recently introduced lattice models of granular media. The avalanche is produced by pulling out a grain at the base of the packing and then studying the number of grains to be rearranged before the packing is stable again. We find that the avalanches are long-ranged, decaying as a power law. We study the distribution of avalanches as a function of the density of the packing and find that the avalanche distribution is a very sensitive structural probe of the system. |
Khirshnamurthy, Supriya; Loreto, Vittorio; Hermann, Hans J; Manna, Subhrangshu S; Roux, Stephane Self-structuring of granular media under internal avalanching Journal Article PHYSICAL REVIEW LETTERS, 83 , pp. 304–307, 1999. Abstract | Links | BibTeX | Tags: granular_media, herrmann, khrishnamurthy, loreto, manna, roux @article{b, title = {Self-structuring of granular media under internal avalanching}, author = {Supriya Khirshnamurthy and Vittorio Loreto and Hans J. Hermann and Subhrangshu S. Manna and Stephane Roux}, url = {http://prl.aps.org/abstract/PRL/v83/i2/p304_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000081358900016&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1999}, date = {1999-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {83}, pages = {304--307}, publisher = {American Physical Soc., One Physics Ellipse, College PK, MD 20740-3844 USA}, abstract = {We study the phenomenon of internal avalanching within the context of recently proposed "Tetris" lattice models for granular media. We define a recycling dynamics under which the system reaches a steady state which is self-structured, i.e., it shows a complex interplay between textured internal structures and critical avalanche behavior. Furthermore, we develop a general mean-field theory for this class of systems and discuss possible scenarios for the breakdown of universality.}, keywords = {granular_media, herrmann, khrishnamurthy, loreto, manna, roux}, pubstate = {published}, tppubtype = {article} } We study the phenomenon of internal avalanching within the context of recently proposed "Tetris" lattice models for granular media. We define a recycling dynamics under which the system reaches a steady state which is self-structured, i.e., it shows a complex interplay between textured internal structures and critical avalanche behavior. Furthermore, we develop a general mean-field theory for this class of systems and discuss possible scenarios for the breakdown of universality. |
Hascoet, Erwan; Herrmann, Hand J; Loreto, Vittorio Shock propagation in a granular chain Journal Article PHYSICAL REVIEW E, 59 , pp. 3202–3206, 1999. Abstract | Links | BibTeX | Tags: granular_media, hascoet, herrmann, loreto @article{b, title = {Shock propagation in a granular chain}, author = {Erwan Hascoet and Hand J. Herrmann and Vittorio Loreto}, url = {http://pre.aps.org/abstract/PRE/v59/i3/p3202_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000079233500019&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1999}, date = {1999-01-01}, journal = {PHYSICAL REVIEW E}, volume = {59}, pages = {3202--3206}, publisher = {AMERICAN PHYSICAL SOC.}, abstract = {We numerically solve the propagation of a shock wave in a chain of elastic beads with no restoring forces under traction (no-tension elasticity). We find a sequence of peaks of decreasing amplitude and velocity. Analyzing the main peak at different times we confirm a recently proposed scaling law for its decay.}, keywords = {granular_media, hascoet, herrmann, loreto}, pubstate = {published}, tppubtype = {article} } We numerically solve the propagation of a shock wave in a chain of elastic beads with no restoring forces under traction (no-tension elasticity). We find a sequence of peaks of decreasing amplitude and velocity. Analyzing the main peak at different times we confirm a recently proposed scaling law for its decay. |
1998 |
Chierchia, Rosaria; Loreti, Stefano; Loreto, Vittorio; Mariucci, Luigi; Minarini, Carla; Mittiga, Alberto A critical assessment of different models of the metastability in a-Si:H. Journal Article JAPANESE JOURNAL OF APPLIED PHYSICS, 37 , pp. 1736–1746, 1998. Abstract | Links | BibTeX | Tags: chierchia, loreti, loreto, mariucci, minarini, mittiga, statistical_physics @article{b, title = {A critical assessment of different models of the metastability in a-Si:H.}, author = {Rosaria Chierchia and Stefano Loreti and Vittorio Loreto and Luigi Mariucci and Carla Minarini and Alberto Mittiga}, url = {http://jjap.jsap.jp/link?JJAP/37/1736/, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000076042900016&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1998}, date = {1998-01-01}, journal = {JAPANESE JOURNAL OF APPLIED PHYSICS}, volume = {37}, pages = {1736--1746}, abstract = {We have studied the light degradation and the thermal annealing of a-Si:H at different light intensities and temperatures monitoring both the defect density and the photoconductivity. This large set of data is used as a benchmark for the models of the metastability in a-Si:H. We show that an entire class of these models (which predict stretched exponential kinetics) is not in good agreement with our data. We discuss the mathematical and physical basis of these models pointing out some weak points that could explain these failures. The data are in better agreement with the “recombination induced bond breaking" models if an accurate description of annealing processes is included. The annealing rate must be computed considering a broad distribution of energy barriers. It must be also taken into account that the energy barrier for the annealing of a metastable defect can be reduced by a monomolecular trapping event at the defect itself. Our calculations show that this reduction amounts to an energy of about half the gap and lasts for a time of the order of 1 ps.}, keywords = {chierchia, loreti, loreto, mariucci, minarini, mittiga, statistical_physics}, pubstate = {published}, tppubtype = {article} } We have studied the light degradation and the thermal annealing of a-Si:H at different light intensities and temperatures monitoring both the defect density and the photoconductivity. This large set of data is used as a benchmark for the models of the metastability in a-Si:H. We show that an entire class of these models (which predict stretched exponential kinetics) is not in good agreement with our data. We discuss the mathematical and physical basis of these models pointing out some weak points that could explain these failures. The data are in better agreement with the “recombination induced bond breaking" models if an accurate description of annealing processes is included. The annealing rate must be computed considering a broad distribution of energy barriers. It must be also taken into account that the energy barrier for the annealing of a metastable defect can be reduced by a monomolecular trapping event at the defect itself. Our calculations show that this reduction amounts to an energy of about half the gap and lasts for a time of the order of 1 ps. |
Loreto, Vittorio; Prosini, Pierpaolo; Cafiero, Raffaele Anisotropy and non-universality in kinetic roughening Journal Article EUROPHYSICS LETTERS, 42 , pp. 389–394, 1998. Abstract | Links | BibTeX | Tags: cafiero, loreto, prosini, statistical_physics @article{b, title = {Anisotropy and non-universality in kinetic roughening}, author = {Vittorio Loreto and Pierpaolo Prosini and Raffaele Cafiero}, url = {http://iopscience.iop.org/0295-5075/42/4/389/fulltext/42407.html, http://www.scopus.com/inward/record.url?eid=2-s2.0-0032523674&partnerID=65&md5=7ee2db2e9fa4b3390e2fa7b3d509cecb, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000073734100007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1998}, date = {1998-01-01}, journal = {EUROPHYSICS LETTERS}, volume = {42}, pages = {389--394}, abstract = {We introduce a new model for kinetic roughening which exhibits a non-universal behavior for the roughness exponent, in agreement with many experimental findings. The model, inspired by the chemical etching processes, takes explicitly into account the effect of anisotropy, say the dependence of the growth rule on the local environment conditions. The interplay between anisotropy and non-universality is investigated as well as the relationship with the known universality classes.}, keywords = {cafiero, loreto, prosini, statistical_physics}, pubstate = {published}, tppubtype = {article} } We introduce a new model for kinetic roughening which exhibits a non-universal behavior for the roughness exponent, in agreement with many experimental findings. The model, inspired by the chemical etching processes, takes explicitly into account the effect of anisotropy, say the dependence of the growth rule on the local environment conditions. The interplay between anisotropy and non-universality is investigated as well as the relationship with the known universality classes. |
Puglisi, Andrea; Loreto, Vittorio; Bettolo, Umberto Marini; Petri, Alberto; Vulpiani, Angelo Clustering and non-gaussian behavior in granular matter Journal Article PHYSICAL REVIEW LETTERS, 81 , pp. 3848–3848, 1998. BibTeX | Tags: granular_media, loreto, marini bettolo, petri, puglisi, vulpiani @article{b, title = {Clustering and non-gaussian behavior in granular matter}, author = {Andrea Puglisi and Vittorio Loreto and Umberto Marini Bettolo and Alberto Petri and Angelo Vulpiani}, year = {1998}, date = {1998-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {81}, pages = {3848--3848}, keywords = {granular_media, loreto, marini bettolo, petri, puglisi, vulpiani}, pubstate = {published}, tppubtype = {article} } |
Caglioti, Emanuele; Coniglio, Antonio; Herrmann, Hans J; Loreto, Vittorio; Nicodemi, Mario Segregation of granular mixtures in presence of compaction Journal Article EUROPHYSICS LETTERS, 43 , pp. 591–597, 1998. Abstract | Links | BibTeX | Tags: caglioti, coniglio, granular_media, herrmann, loreto, nicodemi, tetris @article{b, title = {Segregation of granular mixtures in presence of compaction}, author = {Emanuele Caglioti and Antonio Coniglio and Hans J. Herrmann and Vittorio Loreto and Mario Nicodemi}, url = {http://iopscience.iop.org/0295-5075/43/5/591/, http://www.scopus.com/inward/record.url?eid=2-s2.0-0032164694&partnerID=65&md5=c108ca4627474930d839d71d325afc8b, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000075612400017&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1998}, date = {1998-01-01}, journal = {EUROPHYSICS LETTERS}, volume = {43}, pages = {591--597}, abstract = {We study the segregation phenomena in granular media in the framework of Tetris-like models for granular compaction. The models, which focus on the geometrical properties of mixtures, exhibit segregation, i.e. separation of particles with different degrees of geometrical frustration. This effect is related to the effective average mobilities of the different particles. Mie study these effects in the context of an analytical mean-field-like model.}, keywords = {caglioti, coniglio, granular_media, herrmann, loreto, nicodemi, tetris}, pubstate = {published}, tppubtype = {article} } We study the segregation phenomena in granular media in the framework of Tetris-like models for granular compaction. The models, which focus on the geometrical properties of mixtures, exhibit segregation, i.e. separation of particles with different degrees of geometrical frustration. This effect is related to the effective average mobilities of the different particles. Mie study these effects in the context of an analytical mean-field-like model. |
1997 |
Caglioti, Emanuele; Loreto, Vittorio; Herrmann, Hans J; Nicodemi, Mario A "tetris-like" model for the compaction of dry granular media Journal Article PHYSICAL REVIEW LETTERS, 79 , pp. 1575–1578, 1997. Abstract | Links | BibTeX | Tags: caglioti, granular_media, herrmann, loreto, nicodemi, tetris @article{b, title = {A "tetris-like" model for the compaction of dry granular media}, author = {Emanuele Caglioti and Vittorio Loreto and Hans J. Herrmann and Mario Nicodemi}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.79.1575, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1997XT12400038&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1997}, date = {1997-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {79}, pages = {1575--1578}, abstract = {We propose a two-dimensional geometrical model, based on the concept of geometrical frustration, conceived for the study of compaction in granular media. The dynamics exhibits an interesting inverse logarithmic law that is well known from real experiments. Moreover, we present a simple dynamical model of N planes exchanging particles with excluded volume problems, which allows us to clarify the origin of the logarithmic relaxations and the stationary density distribution. A simple mapping allows us to cast this Tetris-like model in the form of an Ising-like spin system with vacancies.}, keywords = {caglioti, granular_media, herrmann, loreto, nicodemi, tetris}, pubstate = {published}, tppubtype = {article} } We propose a two-dimensional geometrical model, based on the concept of geometrical frustration, conceived for the study of compaction in granular media. The dynamics exhibits an interesting inverse logarithmic law that is well known from real experiments. Moreover, we present a simple dynamical model of N planes exchanging particles with excluded volume problems, which allows us to clarify the origin of the logarithmic relaxations and the stationary density distribution. A simple mapping allows us to cast this Tetris-like model in the form of an Ising-like spin system with vacancies. |
Vespignani, Alessandro; Zapperi, Stefano; Loreto, Vittorio Dynamically driven renormalization group Journal Article JOURNAL OF STATISTICAL PHYSICS, 88 , pp. 47–79, 1997. Abstract | Links | BibTeX | Tags: DDRG, loreto, self_organization, statistical_physics, vespignani, zapperi @article{b, title = {Dynamically driven renormalization group}, author = {Alessandro Vespignani and Stefano Zapperi and Vittorio Loreto}, url = {http://www.springerlink.com/content/d1215122128712g1/, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1997XT83300003&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1997}, date = {1997-01-01}, journal = {JOURNAL OF STATISTICAL PHYSICS}, volume = {88}, pages = {47--79}, abstract = {We present a detailed discussion of a novel dynamical renormalization group scheme: the dynamically driven renormalization group (DDRG). This is a general renormalization method developed for dynamical systems with non-equilibrium critical steady state. The method is based on a real-space renormalization scheme driven by a dynamical steady-state condition which acts as a feedback on the transformation equations. This approach has been applied to open nonlinear systems such as self-organized critical phenomena, and it allows the analytical evaluation of scalling dimensions and critical exponents. Equilibrium models at the critical point can also be considered. The explicit application to some models and the corresponding results are discussed.}, keywords = {DDRG, loreto, self_organization, statistical_physics, vespignani, zapperi}, pubstate = {published}, tppubtype = {article} } We present a detailed discussion of a novel dynamical renormalization group scheme: the dynamically driven renormalization group (DDRG). This is a general renormalization method developed for dynamical systems with non-equilibrium critical steady state. The method is based on a real-space renormalization scheme driven by a dynamical steady-state condition which acts as a feedback on the transformation equations. This approach has been applied to open nonlinear systems such as self-organized critical phenomena, and it allows the analytical evaluation of scalling dimensions and critical exponents. Equilibrium models at the critical point can also be considered. The explicit application to some models and the corresponding results are discussed. |
Hallgass, Riccardo; Loreto, Vittorio; Mazzella, Orfeo; Paladin, Giovanni Earthquakes statistics and fractal faults Journal Article PHYSICAL REVIEW E, 56 , pp. 1346–1356, 1997. Abstract | Links | BibTeX | Tags: earthquakes, hallgass, loreto, mazzella, paladin, self_organization, statistical_physics @article{b, title = {Earthquakes statistics and fractal faults}, author = {Riccardo Hallgass and Vittorio Loreto and Orfeo Mazzella and Giovanni Paladin}, url = {http://pre.aps.org/abstract/PRE/v56/i2/p1346_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1997XR16000015&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1997}, date = {1997-01-01}, journal = {PHYSICAL REVIEW E}, volume = {56}, pages = {1346--1356}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {We introduce a Self-affine Asperity Model (SAM) for the seismicity that mimics the fault friction by means of two fractional Brownian profiles (fBm) that slide one over the other. An earthquake occurs when there is an overlap of the two profiles representing the two fault faces and its energy is assumed proportional to the overlap surface. The SAM exhibits the Gutenberg-Richter law with an exponent $beta$ related to the roughness index of the profiles. Apart from being analytically treatable, the model exhibits a non-trivial clustering in the spatio-temporal distribution of epicenters that strongly resembles the experimentally observed one. A generalized and more realistic version of the model exhibits the Omori scaling for the distribution of the aftershocks. The SAM lies in a different perspective with respect to usual models for seismicity. In this case, in fact, the critical behaviour is not Self-Organized but stems from the fractal geometry of the faults, which, on its turn, is supposed to arise as a consequence of geological processes on very long time scales with respect to the seismic dynamics. The explicit introduction of the fault geometry, as an active element of this complex phenomenology, represents the real novelty of our approach.}, keywords = {earthquakes, hallgass, loreto, mazzella, paladin, self_organization, statistical_physics}, pubstate = {published}, tppubtype = {article} } We introduce a Self-affine Asperity Model (SAM) for the seismicity that mimics the fault friction by means of two fractional Brownian profiles (fBm) that slide one over the other. An earthquake occurs when there is an overlap of the two profiles representing the two fault faces and its energy is assumed proportional to the overlap surface. The SAM exhibits the Gutenberg-Richter law with an exponent $beta$ related to the roughness index of the profiles. Apart from being analytically treatable, the model exhibits a non-trivial clustering in the spatio-temporal distribution of epicenters that strongly resembles the experimentally observed one. A generalized and more realistic version of the model exhibits the Omori scaling for the distribution of the aftershocks. The SAM lies in a different perspective with respect to usual models for seismicity. In this case, in fact, the critical behaviour is not Self-Organized but stems from the fractal geometry of the faults, which, on its turn, is supposed to arise as a consequence of geological processes on very long time scales with respect to the seismic dynamics. The explicit introduction of the fault geometry, as an active element of this complex phenomenology, represents the real novelty of our approach. |
1996 |
Hur, Asa Ben; Hallgass, Riccardo; Loreto, Vittorio A renormalization procedure for directed sandpile models Journal Article PHYSICAL REVIEW E, 54 , pp. 1426–1432, 1996. Abstract | Links | BibTeX | Tags: ben-hur, DDRG, hallgass, loreto, self_organization, statistical_physics @article{b, title = {A renormalization procedure for directed sandpile models}, author = {Asa Ben Hur and Riccardo Hallgass and Vittorio Loreto}, url = {http://pre.aps.org/abstract/PRE/v54/i2/p1426_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1996VD67400057&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1996}, date = {1996-01-01}, journal = {PHYSICAL REVIEW E}, volume = {54}, pages = {1426--1432}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {Directed models of self-organized criticality are studied in the framework of a real-space renormalization group of a different type. The identification of a suitable phase space in which to define the renormalization transformation and the coupling with the stationarity condition enables us to clarify the nature of the critical state. The renormalization equations are found to have an attractive fixed point, as expected from the self-critical nature of the model. The values of the critical exponents obtained by this procedure are in excellent agreement with exact results.}, keywords = {ben-hur, DDRG, hallgass, loreto, self_organization, statistical_physics}, pubstate = {published}, tppubtype = {article} } Directed models of self-organized criticality are studied in the framework of a real-space renormalization group of a different type. The identification of a suitable phase space in which to define the renormalization transformation and the coupling with the stationarity condition enables us to clarify the nature of the critical state. The renormalization equations are found to have an attractive fixed point, as expected from the self-critical nature of the model. The values of the critical exponents obtained by this procedure are in excellent agreement with exact results. |
Loreto, Vittorio; Paladin, Giovanni; Pasquini, Michele; Vulpiani, Angelo Characterization of chaos in random maps Journal Article PHYSICA. A, 232 , pp. 189–200, 1996. Abstract | Links | BibTeX | Tags: dynamical_systems, loreto, paladin, pasquini, vulpiani @article{b, title = {Characterization of chaos in random maps}, author = {Vittorio Loreto and Giovanni Paladin and Michele Pasquini and Angelo Vulpiani}, url = {http://www.sciencedirect.com/science/article/pii/0378437196000878 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1996VN65900016&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1996}, date = {1996-01-01}, journal = {PHYSICA. A}, volume = {232}, pages = {189--200}, publisher = {ELSEVIER SCIENCE, AMSTERDAM}, abstract = {We discuss the characterization of chaotic behaviors in random maps both in terms of the Lyapunov exponent and of the spectral properties of the Perron-Frobenius operator. In particular, we study a logistic map where the control parameter is extracted at random at each time step by considering finite-dimensional approximation of the Perron-Frobenius operator.}, keywords = {dynamical_systems, loreto, paladin, pasquini, vulpiani}, pubstate = {published}, tppubtype = {article} } We discuss the characterization of chaotic behaviors in random maps both in terms of the Lyapunov exponent and of the spectral properties of the Perron-Frobenius operator. In particular, we study a logistic map where the control parameter is extracted at random at each time step by considering finite-dimensional approximation of the Perron-Frobenius operator. |
Loreto, Vittorio; Paladin, Giovanni; Vulpiani, Angelo Concept of complexity in random dynamical systems Journal Article PHYSICAL REVIEW E, 53 , pp. 2087–2098, 1996. Abstract | Links | BibTeX | Tags: complexity, dynamical_systems, loreto, paladin, statistical_physics, vulpiani @article{b, title = {Concept of complexity in random dynamical systems}, author = {Vittorio Loreto and Giovanni Paladin and Angelo Vulpiani}, url = {http://pre.aps.org/abstract/PRE/v53/i3/p2087_1 http://samarcanda.phys.uniroma1.it/vittorioloreto/PAPERS/1996/Loreto_PhysRevE_1996.pdf}, year = {1996}, date = {1996-01-01}, journal = {PHYSICAL REVIEW E}, volume = {53}, pages = {2087--2098}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {We introduce a measure of complexity in terms of the average number of bits per time unit necessary to specify the sequence generated by the system. In dynamical systems with small random perturbations, this indicator coincides with the rate K of divergence of nearby trajectories evolving under two different noise realizations. The meaning of K is discussed in the context of the information theory, and it is shown that it can be determined from real experimental data. In the presence of strong dynamical intermittency, the value of K is very different from the standard Lyapunov exponent lambda(sigma) computed considering two nearby trajectories evolving under the same realization of the randomness. However, the former is much more relevant than the latter from a physical point of view, as illustrated by some numerical computations for noisy maps and sandpile models.}, keywords = {complexity, dynamical_systems, loreto, paladin, statistical_physics, vulpiani}, pubstate = {published}, tppubtype = {article} } We introduce a measure of complexity in terms of the average number of bits per time unit necessary to specify the sequence generated by the system. In dynamical systems with small random perturbations, this indicator coincides with the rate K of divergence of nearby trajectories evolving under two different noise realizations. The meaning of K is discussed in the context of the information theory, and it is shown that it can be determined from real experimental data. In the presence of strong dynamical intermittency, the value of K is very different from the standard Lyapunov exponent lambda(sigma) computed considering two nearby trajectories evolving under the same realization of the randomness. However, the former is much more relevant than the latter from a physical point of view, as illustrated by some numerical computations for noisy maps and sandpile models. |
Caglioti, Emanuele; Loreto, Vittorio Dynamical properties and predictability in a class of self-organized critical models Journal Article PHYSICAL REVIEW E, 53 , pp. R2953–R2956, 1996. Abstract | Links | BibTeX | Tags: caglioti, dynamical_systems, loreto, self_organization, statistical_physics @article{b, title = {Dynamical properties and predictability in a class of self-organized critical models}, author = {Emanuele Caglioti and Vittorio Loreto}, url = {http://pre.aps.org/abstract/PRE/v53/i3/p2953_1 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1996UA37100116&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1996}, date = {1996-01-01}, journal = {PHYSICAL REVIEW E}, volume = {53}, pages = {R2953--R2956}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {We consider a particular class of self-organized critical models. For these systems we show that the Lyapunov exponent is strictly lower than zero. That allows us to describe the dynamics in terms of a piecewise linear contractive map. We describe the physical mechanisms underlying the approach to the recurrent set in the configuration space and we discuss the structure of the attractor for the dynamics. Finally the problem of the chaoticity of these systems and the definition of a predictability are addressed.}, keywords = {caglioti, dynamical_systems, loreto, self_organization, statistical_physics}, pubstate = {published}, tppubtype = {article} } We consider a particular class of self-organized critical models. For these systems we show that the Lyapunov exponent is strictly lower than zero. That allows us to describe the dynamics in terms of a piecewise linear contractive map. We describe the physical mechanisms underlying the approach to the recurrent set in the configuration space and we discuss the structure of the attractor for the dynamics. Finally the problem of the chaoticity of these systems and the definition of a predictability are addressed. |
Vespignani, Alessandro; Zapperi, Stefano; Loreto, Vittorio Renormalization of non-equilibrium systems with critical stationary state Journal Article PHYSICAL REVIEW LETTERS, 77 , pp. 4560–4563, 1996. Abstract | Links | BibTeX | Tags: DDRG, loreto, self_organization, statistical_physics, vespignani, zapperi @article{b, title = {Renormalization of non-equilibrium systems with critical stationary state}, author = {Alessandro Vespignani and Stefano Zapperi and Vittorio Loreto}, url = {http://prl.aps.org/abstract/PRL/v77/i22/p4560_1 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1996VU50200020&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1996}, date = {1996-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {77}, pages = {4560--4563}, abstract = {We introduce the general formulation of a renormalization method suitable to study the critical properties of non-equilibrium systems with steady-states: the Dynamically Driven Renormalization Group. We renormalize the time evolution operator by computing the rescaled time transition rate between coarse grained states. The obtained renormalization equations are coupled to a stationarity condition which provides the approximate non-equilibrium statistical weights of steady-state configurations to be used in the calculations. In this way we are able to write recursion relations for the parameters evolution under scale change, from which we can extract numerical values for the critical exponents. This general framework allows the systematic analysis of several models showing self-organized criticality in terms of usual concepts of phase transitions and critical phenomena.}, keywords = {DDRG, loreto, self_organization, statistical_physics, vespignani, zapperi}, pubstate = {published}, tppubtype = {article} } We introduce the general formulation of a renormalization method suitable to study the critical properties of non-equilibrium systems with steady-states: the Dynamically Driven Renormalization Group. We renormalize the time evolution operator by computing the rescaled time transition rate between coarse grained states. The obtained renormalization equations are coupled to a stationarity condition which provides the approximate non-equilibrium statistical weights of steady-state configurations to be used in the calculations. In this way we are able to write recursion relations for the parameters evolution under scale change, from which we can extract numerical values for the critical exponents. This general framework allows the systematic analysis of several models showing self-organized criticality in terms of usual concepts of phase transitions and critical phenomena. |
Loreto, Vittorio; Vespignani, Alessandro; Zapperi, Stefano Renormalization scheme for forest-fire models Journal Article JOURNAL OF PHYSICS. A, MATHEMATICAL AND GENERAL, 29 , pp. 2981–3004, 1996. Links | BibTeX | Tags: DDRG, loreto, self_organization, statistical_physics, vespignani, zapperi @article{b, title = {Renormalization scheme for forest-fire models}, author = {Vittorio Loreto and Alessandro Vespignani and Stefano Zapperi}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0040108749&partnerID=65&md5=f34393a56c2dfc0797f394df2fda943a http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1996UU80300008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1996}, date = {1996-01-01}, journal = {JOURNAL OF PHYSICS. A, MATHEMATICAL AND GENERAL}, volume = {29}, pages = {2981--3004}, publisher = {IOP Publishing Limited:Dirac House, Temple Back, Bristol BS1 6BE United Kingdom:011 44 117 9297481, EMAIL: custserv@iop.org, INTERNET: http://www.iop.org, Fax: 011 44 117 9294318}, keywords = {DDRG, loreto, self_organization, statistical_physics, vespignani, zapperi}, pubstate = {published}, tppubtype = {article} } |
Rubeis, Valerio De; Hallgass, Riccardo; Loreto, Vittorio PHYSICAL REVIEW LETTERS, 76 , pp. 2599–2602, 1996. Abstract | Links | BibTeX | Tags: derubeis, earthquakes, halgass, loreto, statistical_physics @article{b, author = {Valerio De Rubeis and Riccardo Hallgass and Vittorio Loreto}, url = {http://prl.aps.org/abstract/PRL/v76/i14/p2599_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1996UC77700049&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1996}, date = {1996-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {76}, pages = {2599--2602}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {A model for fault dynamics consisting of two rough and rigid Brownian profiles that slide one over the other is introduced. An earthquake occurs when there is an intersection between the two profiles. The energy released is proportional to the overlap interval. Our model exhibits some specific features which follow from the fractal geometry of the fault: (1) nonuniversality of the exponent of the Gutenberg-Richter law for the magnitude distribution, (2) presence of local stress accumulation before a large seismic event, and (3) nontrivial space-time clustering of the epicenters.}, keywords = {derubeis, earthquakes, halgass, loreto, statistical_physics}, pubstate = {published}, tppubtype = {article} } A model for fault dynamics consisting of two rough and rigid Brownian profiles that slide one over the other is introduced. An earthquake occurs when there is an intersection between the two profiles. The energy released is proportional to the overlap interval. Our model exhibits some specific features which follow from the fractal geometry of the fault: (1) nonuniversality of the exponent of the Gutenberg-Richter law for the magnitude distribution, (2) presence of local stress accumulation before a large seismic event, and (3) nontrivial space-time clustering of the epicenters. |
1995 |
Cafiero, Raffaele; Loreto, Vittorio; Pietronero, Luciano; Vespignani, Alessandro; Zapperi, Stefano Local rigidity and self-organized criticality for avalanches Journal Article EUROPHYSICS LETTERS, 29 , pp. 111–116, 1995. Abstract | Links | BibTeX | Tags: cafiero, loreto, pietronero, self_organization, statistical_physics, vespignani, zapperi @article{b, title = {Local rigidity and self-organized criticality for avalanches}, author = {Raffaele Cafiero and Vittorio Loreto and Luciano Pietronero and Alessandro Vespignani and Stefano Zapperi}, url = {http://iopscience.iop.org/0295-5075/29/2/001;jsessionid=8822A74DE3C96358510326242C4AF4E3.c3 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1995QC36900001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1995}, date = {1995-01-01}, journal = {EUROPHYSICS LETTERS}, volume = {29}, pages = {111--116}, publisher = {EDITIONS PHYSIQUE}, abstract = {The general conditions for a sandpile system to evolve spontaneously into a critical state characterized by a power law distribution of avalanches or bursts are identified as: a) the existence of a stationary state with a global conservation law; b) long-range correlations in the continuum limit (i.e. Laplacian diffusive field); c) the existence of a local rigidity for the microscopic dynamics. These conditions permit a classification of the models that have been considered up to now and the identification of the local rigidity as a new basic parameter that can lead to various possible scenarios ranging continuously from SOC behaviour to standard diffusion.}, keywords = {cafiero, loreto, pietronero, self_organization, statistical_physics, vespignani, zapperi}, pubstate = {published}, tppubtype = {article} } The general conditions for a sandpile system to evolve spontaneously into a critical state characterized by a power law distribution of avalanches or bursts are identified as: a) the existence of a stationary state with a global conservation law; b) long-range correlations in the continuum limit (i.e. Laplacian diffusive field); c) the existence of a local rigidity for the microscopic dynamics. These conditions permit a classification of the models that have been considered up to now and the identification of the local rigidity as a new basic parameter that can lead to various possible scenarios ranging continuously from SOC behaviour to standard diffusion. |
Loreto, Vittorio; Pietronero, Luciano; Vespignani, Alessandro; Zapperi, Stefano Renormalization group approach to the crtical behavior of the forest-fire model Journal Article PHYSICAL REVIEW LETTERS, 75 , pp. 465–468, 1995. Abstract | Links | BibTeX | Tags: DDRG, loreto, pietronero, self_organization, statistical_physics, vespignani, zapperi @article{b, title = {Renormalization group approach to the crtical behavior of the forest-fire model}, author = {Vittorio Loreto and Luciano Pietronero and Alessandro Vespignani and Stefano Zapperi}, url = {http://prl.aps.org/abstract/PRL/v75/i3/p465_1, http://www.scopus.com/inward/record.url?eid=2-s2.0-0000977225&partnerID=65&md5=4f03991047dc2820ef6c00a2e81b3c7d http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1995RK33000028&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1995}, date = {1995-01-01}, journal = {PHYSICAL REVIEW LETTERS}, volume = {75}, pages = {465--468}, abstract = {We introduce a renormalization scheme for the one- and two-dimensional forest-fire model in order to characterize the nature of the critical state and its scale invariant dynamics. We show the existence of a relevant scaling field associated with a repulsive fixed point. This model is therefore critical in the usual sense because the control parameter has to be tuned to its critical value in order to get criticality. It turns out that this is not just the condition for a time scale separation. The critical exponents are computed analytically and we obtain ν = 1.0, τ = 1.0 and ν = 0.65, τ = 1.16, respectively, for the one- and two-dimensional cases, in very good agreement with numerical simulations.}, keywords = {DDRG, loreto, pietronero, self_organization, statistical_physics, vespignani, zapperi}, pubstate = {published}, tppubtype = {article} } We introduce a renormalization scheme for the one- and two-dimensional forest-fire model in order to characterize the nature of the critical state and its scale invariant dynamics. We show the existence of a relevant scaling field associated with a repulsive fixed point. This model is therefore critical in the usual sense because the control parameter has to be tuned to its critical value in order to get criticality. It turns out that this is not just the condition for a time scale separation. The critical exponents are computed analytically and we obtain ν = 1.0, τ = 1.0 and ν = 0.65, τ = 1.16, respectively, for the one- and two-dimensional cases, in very good agreement with numerical simulations. |
1992 |
Dattoli, Giuseppe; Cabrini, Stefano; Giannessi, Luca; Loreto, Vittorio Exact treatment of spontaneous emission in helical and solenoidal magnetic field Journal Article NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA. D CONDENSED MATTER, ATOMIC, MOLECULAR AND CHEMICAL PHYSICS, BIOPHYSICS, 14D , pp. 719–727, 1992. Abstract | Links | BibTeX | Tags: cabrini, dattoli, giannessi, loreto, quantum_optics @article{b, title = {Exact treatment of spontaneous emission in helical and solenoidal magnetic field}, author = {Giuseppe Dattoli and Stefano Cabrini and Luca Giannessi and Vittorio Loreto}, url = {http://www.springerlink.com/content/6721v8246070j327/ http://www.scopus.com/inward/record.url?eid=2-s2.0-51249166997&partnerID=65&md5=9c29969a031a9ce6d5973430113711d9 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1992JN19500005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1992}, date = {1992-01-01}, journal = {NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA. D CONDENSED MATTER, ATOMIC, MOLECULAR AND CHEMICAL PHYSICS, BIOPHYSICS}, volume = {14D}, pages = {719--727}, publisher = {EDITRICE COMPOSITORI BOLOGNA}, abstract = {In this paper we discuss the spectral properties of the radiation emitted by electrons moving in helical undulators and solenoids. The analysis is exact, in the sense that the electron beam is not assumed to be ultrarelativistic but the far-field condition is still retained. We also discuss the low-energy corrections, the limits of validity of the usual approximations and the relevance of our results to gyrotron-type devices.}, keywords = {cabrini, dattoli, giannessi, loreto, quantum_optics}, pubstate = {published}, tppubtype = {article} } In this paper we discuss the spectral properties of the radiation emitted by electrons moving in helical undulators and solenoids. The analysis is exact, in the sense that the electron beam is not assumed to be ultrarelativistic but the far-field condition is still retained. We also discuss the low-energy corrections, the limits of validity of the usual approximations and the relevance of our results to gyrotron-type devices. |
Dattoli, Giuseppe; Giannessi, Luca; Cabrini, Stefano; Loreto, Vittorio Gain saturation in bunched free electrons lasers Journal Article PHYSICAL REVIEW A, 45 , pp. 8842–8845, 1992. Abstract | Links | BibTeX | Tags: cabrini, dattoli, giannessi, loreto, mari, quantum_optics @article{b, title = {Gain saturation in bunched free electrons lasers}, author = {Giuseppe Dattoli and Luca Giannessi and Stefano Cabrini and Vittorio Loreto}, url = {http://link.aps.org/doi/10.1103/PhysRevA.45.8842, http://www.scopus.com/inward/record.url?eid=2-s2.0-0008760169&partnerID=65&md5=2da9957ef0ea338cb9c72159a32160a3 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1992JA21400064&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1992}, date = {1992-01-01}, journal = {PHYSICAL REVIEW A}, volume = {45}, pages = {8842--8845}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {We propose a model of gain saturation in free-electron lasers operating with a bunched electron beam. A simple method to evaluate the steady-state intensity as a function of the optical cavity length is given and the result is in close agreement with the intensity measured in the Los Alamos free-electron-laser experiment [B. E. Newnam et al., Nucl. Instrum. Methods A 237, 187 (1985)].}, keywords = {cabrini, dattoli, giannessi, loreto, mari, quantum_optics}, pubstate = {published}, tppubtype = {article} } We propose a model of gain saturation in free-electron lasers operating with a bunched electron beam. A simple method to evaluate the steady-state intensity as a function of the optical cavity length is given and the result is in close agreement with the intensity measured in the Los Alamos free-electron-laser experiment [B. E. Newnam et al., Nucl. Instrum. Methods A 237, 187 (1985)]. |
Dattoli, Giuseppe; Cabrini, Stefano; Giannessi, Luca; Loreto, Vittorio; Mari, Carlo Gain saturation in free-electron lasers Journal Article NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT, 318 , pp. 495–499, 1992. Abstract | Links | BibTeX | Tags: cabrini, dattoli, giannessi, loreto, mari, quantum_optics @article{b, title = {Gain saturation in free-electron lasers}, author = {Giuseppe Dattoli and Stefano Cabrini and Luca Giannessi and Vittorio Loreto and Carlo Mari}, url = {http://www.sciencedirect.com/science/article/pii/016890029291105I http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1992JD76700094&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1992}, date = {1992-01-01}, journal = {NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT}, volume = {318}, pages = {495--499}, publisher = {ELSEVIER SCIENCE, AMSTERDAM}, abstract = {We propose a model of gain saturation in a free-electron laser, drawing a parallel with the dynamics of saturation in a conventional laser. The results achieved are then extended phenomenologically to bunched-beam operations and the results has been compared to that measured in the experiments at Los Alamos.}, keywords = {cabrini, dattoli, giannessi, loreto, mari, quantum_optics}, pubstate = {published}, tppubtype = {article} } We propose a model of gain saturation in a free-electron laser, drawing a parallel with the dynamics of saturation in a conventional laser. The results achieved are then extended phenomenologically to bunched-beam operations and the results has been compared to that measured in the experiments at Los Alamos. |
1991 |
Dattoli, Giuseppe; Loreto, Vittorio; Mari, Carlo; Richetta, Maria; Torre, Amalia Biunitary transformations and ordinary differential equations - I Journal Article LA RIVISTA DEL NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA, 106B , pp. 1357–1374, 1991. Abstract | Links | BibTeX | Tags: dattoli, loreto, mari, quantum_optics, richetta, torre @article{b, title = {Biunitary transformations and ordinary differential equations - I}, author = {Giuseppe Dattoli and Vittorio Loreto and Carlo Mari and Maria Richetta and Amalia Torre}, url = {http://dx.doi.org/10.1007/BF02728366, http://www.scopus.com/inward/record.url?eid=2-s2.0-51249174048&partnerID=65&md5=71e6cba395d9f74b6cdd9da971d3c6e0 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1991HE48800002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1991}, date = {1991-01-01}, journal = {LA RIVISTA DEL NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA}, volume = {106B}, pages = {1357--1374}, publisher = {Italian Physical Society}, abstract = {We reformulate the theory of ordinary differential equations of arbitrary order with nonconstant coefficients, using the formalism of non-Hermitian operators. In particular, exploiting the technique of dissipative quantum mechanics, we show that the solution of the equations can be written in terms of a nonunitary evolution operator. Furthermore, we point out that the solution of the adjoint equations can be derived from an associated biunitary operator. We show that a number of invariants, not previously discussed, exhists. Finally, we prove that the method allows the search for approximate solutions that can be used in many physical problems.}, keywords = {dattoli, loreto, mari, quantum_optics, richetta, torre}, pubstate = {published}, tppubtype = {article} } We reformulate the theory of ordinary differential equations of arbitrary order with nonconstant coefficients, using the formalism of non-Hermitian operators. In particular, exploiting the technique of dissipative quantum mechanics, we show that the solution of the equations can be written in terms of a nonunitary evolution operator. Furthermore, we point out that the solution of the adjoint equations can be derived from an associated biunitary operator. We show that a number of invariants, not previously discussed, exhists. Finally, we prove that the method allows the search for approximate solutions that can be used in many physical problems. |
Dattoli, Giuseppe; Loreto, Vittorio; Mari, Carlo; Richetta, Maria; Torre, Amalia Biunitary transformations and ordinary differential equations - II Journal Article LA RIVISTA DEL NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA, 106 , pp. 1375–1390, 1991. Abstract | Links | BibTeX | Tags: dattoli, loreto, mari, quantum_optics, richetta, torre @article{b, title = {Biunitary transformations and ordinary differential equations - II}, author = {Giuseppe Dattoli and Vittorio Loreto and Carlo Mari and Maria Richetta and Amalia Torre}, url = {http://rd.springer.com/article/10.1007/BF02728367, http://www.scopus.com/inward/record.url?eid=2-s2.0-51249177614&partnerID=65&md5=2b85bcbf36039a33533f9e968c2e627e http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1991HE48800003&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1991}, date = {1991-01-01}, journal = {LA RIVISTA DEL NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA}, volume = {106}, pages = {1375--1390}, publisher = {EDITRICE COMPOSITORI BOLOGNA, VIA STALINGRADO 97/2, I-40128 BOLOGNA, ITALY}, abstract = {We use the results of a recent reformulation of the theory of arbitrary-order differential equations in terms of non-Hermitian operators to show that the invariant binorm is associated to a generalized Courant-Snyder invariant. Furthermore, we indicate the existence of higher-order invariants associated to the Casimir operators of the group, utilized to treat higher-order equations. We also discuss the intrinsic supersymmetric nature of the theory developed. Finally, we show the relevance of the proposed mathematical technique to the design of fiber-optics transport systems.}, keywords = {dattoli, loreto, mari, quantum_optics, richetta, torre}, pubstate = {published}, tppubtype = {article} } We use the results of a recent reformulation of the theory of arbitrary-order differential equations in terms of non-Hermitian operators to show that the invariant binorm is associated to a generalized Courant-Snyder invariant. Furthermore, we indicate the existence of higher-order invariants associated to the Casimir operators of the group, utilized to treat higher-order equations. We also discuss the intrinsic supersymmetric nature of the theory developed. Finally, we show the relevance of the proposed mathematical technique to the design of fiber-optics transport systems. |
Dattoli, Giuseppe; Loreto, Vittorio; Mari, Carlo; Richetta, Maria; Torre, Amalia Biunitary transformations and ordinary differential equations - III Journal Article LA RIVISTA DEL NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA, 106 B , pp. 1391–1399, 1991. Abstract | Links | BibTeX | Tags: dattoli, loreto, mari, quantum_optics, richetta, torre @article{b, title = {Biunitary transformations and ordinary differential equations - III}, author = {Giuseppe Dattoli and Vittorio Loreto and Carlo Mari and Maria Richetta and Amalia Torre}, url = {http://rd.springer.com/article/10.1007/BF02728368, http://www.scopus.com/inward/record.url?eid=2-s2.0-51249177364&partnerID=65&md5=84b216f43701ba80b3ce08d77b98f277 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1991HE48800004&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1991}, date = {1991-01-01}, journal = {LA RIVISTA DEL NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA}, volume = {106 B}, pages = {1391--1399}, publisher = {EDITRICE COMPOSITORI BOLOGNA}, abstract = {In two previous papers, the authors have introduced the concept of binormal differential equations. It has been shown that invariants of the Courant-Snyder type are associated to the scalar products of the column vector associated to an ordinary differential equation and to its binormal. In this paper, we show the equivalence of the above invariant and the Lewis form. We also introduce a density matrix for a second-order differential equation and clarify the geometrical meaning of the Twiss parameters. The importance of the above results in the analysis of quantum problems such as, e.g., the evolution of squeezed states is finally stressed.}, keywords = {dattoli, loreto, mari, quantum_optics, richetta, torre}, pubstate = {published}, tppubtype = {article} } In two previous papers, the authors have introduced the concept of binormal differential equations. It has been shown that invariants of the Courant-Snyder type are associated to the scalar products of the column vector associated to an ordinary differential equation and to its binormal. In this paper, we show the equivalence of the above invariant and the Lewis form. We also introduce a density matrix for a second-order differential equation and clarify the geometrical meaning of the Twiss parameters. The importance of the above results in the analysis of quantum problems such as, e.g., the evolution of squeezed states is finally stressed. |
Dattoli, Giuseppe; Giannessi, Luca; Loreto, Vittorio; Mari, Carlo Cavity lenght adjustment and output FEL intensity optimization Journal Article IEEE JOURNAL OF QUANTUM ELECTRONICS, 27 , pp. 2370–2372, 1991. Abstract | Links | BibTeX | Tags: dattoli, giannessi, loreto, mari, quantum_optics @article{b, title = {Cavity lenght adjustment and output FEL intensity optimization}, author = {Giuseppe Dattoli and Luca Giannessi and Vittorio Loreto and Carlo Mari}, url = {http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=100874 http://www.scopus.com/inward/record.url?eid=2-s2.0-0026258699&partnerID=65&md5=550a698360dc171a27534fcac1e9f659 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1991GN87900001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1991}, date = {1991-01-01}, journal = {IEEE JOURNAL OF QUANTUM ELECTRONICS}, volume = {27}, pages = {2370--2372}, abstract = {The authors reconsider in more quantitative detail the possibility of enhancing the output intensity of a free electron laser (FEL) oscillator operating with bunched electron beam and finite macropulse duration, adjusting the cavity length while the signal grows. In a forthcoming publication G. Dattoli et al. point out that the output power can be enhanced by moving the cavity mirrors while the intercavity signal grows in such a way that the system is operating at the value of the cavity length providing the maximum gain. Practical solutions to realize the mirror movements will also be discussed. The authors complete the analysis to be published by presenting simple formulas which allow a straightforward evaluation of the power enhancement.}, keywords = {dattoli, giannessi, loreto, mari, quantum_optics}, pubstate = {published}, tppubtype = {article} } The authors reconsider in more quantitative detail the possibility of enhancing the output intensity of a free electron laser (FEL) oscillator operating with bunched electron beam and finite macropulse duration, adjusting the cavity length while the signal grows. In a forthcoming publication G. Dattoli et al. point out that the output power can be enhanced by moving the cavity mirrors while the intercavity signal grows in such a way that the system is operating at the value of the cavity length providing the maximum gain. Practical solutions to realize the mirror movements will also be discussed. The authors complete the analysis to be published by presenting simple formulas which allow a straightforward evaluation of the power enhancement. |
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