Messanae Universitas Studiorum: No conditions. Results ordered -Date Deposited. 2017-03-26T03:20:56ZEPrintshttp://cab.unime.it/images/sitelogo.pnghttp://cab.unime.it/mus/2009-11-26Z2010-04-13T11:14:35Zhttp://cab.unime.it/mus/id/eprint/550This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5502009-11-26ZNon-vanishing theorems for non-split rank 2 bundles on P^3: A simple approachThe paper investigates vanishing conditions on the first cohomology module of a normalized rank 2 vector bundle on P^3 which force to split, and finds therefore strategic levels of non-vanishing for a non-split bundle. The present conditions improve other conditions known in the literature and are obtained with simple computations on the Euler characteristic function, avoiding the speciality lemma, BarthÂ’s restriction theorem, the discriminat property, and other heavy tools.Paolo ValabregaMario Valenzano2009-11-26Z2010-04-13T11:14:23Zhttp://cab.unime.it/mus/id/eprint/558This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5582009-11-26ZNon-reactive strategies in decision-form gamesIn this paper we propose a concept of rationalizable solution for two-player decision-form games: the solution by iterated elimination of non-reactive strategies. Several original theorems are proved about this kind of solution. We study the relations between solutions by iterated elimination of non reactive strategies and game equilibria. We present an existence theorem for bistrategies surviving the iterated elimination and an existence theorem for solution by iterated elimination in contracting games. We, also, show that an equilibrium of a game survives iterated elimination of non reative strategies. At the end we prove a characterization of solvability by iterated elimination of non-reactive strategies.David CarfìAngela Ricciardello2009-11-26Z2010-04-13T11:14:47Zhttp://cab.unime.it/mus/id/eprint/539This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5392009-11-26ZStatistical entropy and clustering in absence of attractive terms in the interparticle potentialRecently a new intriguing class of systems has been introduced, the so-called generalized exponential models, which exhibit clustering phenomena even if the attractive term is missing in their interaction potential. This model is characterized by a index n which tunes the repulsive penetrability of the potential. This family of potentials can represent the effective interactions for a large number of soft matter systems. In this paper we study the structural and thermodynamic properties in the fluid regime of the generalized exponential model with a value of index n suggested by Mladek et al. [B. M. Mladek, G. Kahl, and C. N. Likos, Phys. Rev. Lett. (2008)] to fit the effective potential of a typical amphiphilic dendrimers. We use the conventional approach of the liquid state theory based on the hypernetted chain closure of the Ornstein-Zernike equation together with some Monte Carlo numerical simulations. Moreover, we try to detect qualitatively the freezing line exploiting the predictive properties of a one-phase rule based on the expansion of the statistical entropy.Franz Saija2009-11-26Z2010-04-13T11:14:48Zhttp://cab.unime.it/mus/id/eprint/540This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5402009-11-26ZHarmonic wavelet solution of Poisson's problem with a localized sourceA method, based on a multiscale (wavelet) decomposition of the solution is proposed for the analysis of the Poisson problem. The solution is approximated by a finite series expansion of harmonic wavelets and is based on the computation of the connection coefficients. It is shown, how a sourceless Poisson's problem, solved with the Daubechies wavelets, can also be solved in presence of a localized source in the harmonic wavelet basis.Carlo Cattani2009-11-26Z2010-04-13T11:14:41Zhttp://cab.unime.it/mus/id/eprint/542This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5422009-11-26ZDoes an I(z) correlation exist for the back-part of the Shroud body image?Nowadays it is not known if an I(z) correlation exists for the back-part of the Shroud body image. This occurs because it is difficult to measure the cloth-body distances and to correlate them with the intensities of the image. By a scientific analysis we find a correlation with a slope that is different from the one related to the front-part of the above image.Giovanni FazioGiuseppe Mandaglio2009-11-26Z2010-04-13T11:14:45Zhttp://cab.unime.it/mus/id/eprint/544This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5442009-11-26ZStructures on the space of financial eventsIn this paper we endow the space of financial events with some structures, each of them represents basic facts of financial mathematics. We introduce a preordered structure, that we shall call the usual preorder of the financial events plane, and an algebraic structure, that we call the usual linearoid structure of the financial events plane. The algebraic structures introduced are not void of properties: the usual addition will confer to the space a gruppoid structure and the multiplication by scalars will be a law of action associative and distributive with respect to the addition. We shall prove that these structures are compatible among them and with the standard topology of the plane. Then we show the possibility of defining new (economically relevant) preorders by the use of capitalization factors and that there is a manner (the conjunction) to obtain the usual preorder from infinite continuous families of these new preorders induced by a capitalization factor.David Carfì2009-11-26Z2010-04-13T11:14:38Zhttp://cab.unime.it/mus/id/eprint/546This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5462009-11-26ZArchimede aristotelico o platonico: "tertium non datur"? The aim of the present paper is to continue a critical study on Hellenistic Sciences. Such a study began with some previous papers on Euclid, where some remarkable aspects of the Alexandrinian mathematician emerged; in particular, we focused on some characters, innovative with respect to the previous Greek philosophical tradition and undervalued until now by historiography and critical literature. Here, the figure of Archimedes is analysed in the light of previous results and consequent criteria; he is freed from a long tradition, started with Plutarch, that sees the Sicilian scientist inside a Platonistic (in some sense) paradigm or, inversely, in an Aristotelian one. The re-reading of his works in the light of the new hypotheses, as expressed by other authors and scholars, allows us to delineate a more pragmatic and modern figure of scientist. In particular, some metaphysical problems as those concerning the Truth and Prime Causes, that were central in the Platonic-Aristotelian tradition, are in such a way avoided or suspended, in favour of more exact and appropriate modelling tools that make the phenomenical world more predictable and controllable also by technologies.Giuseppe GentileRenato Migliorato2009-11-26Z2010-04-13T11:14:40Zhttp://cab.unime.it/mus/id/eprint/547This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5472009-11-26ZAristosseno tra aristotelismo e nuova scienzaThe Armonica of Aristoxenus is re-read in the light of a paper by F. Bellissima [Nuncius, XVII, n.1, 2-44 (2002)] that emphasizes its basically deductive structure, although with some limitations at a strictly logical level. We further address some problems recently posed by R. Migliorato, G. Gentile and L. Russo. In particular, Migliorato introduced the expression Euclidean revolution to denote a change in the scientific paradigm with respect to the Aristotelian conception, which, on the ground of extant texts, is observed for the first time in the Euclidean works. Since very few textual sources are available, Migliorato remained prudent as to the total attribution of the perspective change. The analysis carried out here discloses an attempt to overcome the Pitagorean dogmatism already in Aristoxenus, as well as the metaphysical foundation of the Aristotelian deductive science, without however enacting in a clear way the epistemological step that we can observe in Euclid. Such a process partially merges into the Euclidean revolution as formulated by Migliorato.Alessandro Sarritzu2009-11-26Z2010-04-13T11:14:32Zhttp://cab.unime.it/mus/id/eprint/548This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5482009-11-26ZAdaptive web data extraction policiesWeb data extraction is concerned, among other things, with routine data accessing and downloading from continuously-updated dynamic Web pages. There is a relevant trade-off between the rate at which the external Web sites are accessed and the computational burden on the accessing client. We address the problem by proposing a predictive model, typical of the Operating Systems literature, of the rate-of-update of each Web source. The presented model has been implemented into a new version of the Dynamo project: a middleware that assists in generating informative RSS feeds out of traditional HTML Web sites. To be effective, i.e., make RSS feeds be timely and informative and to be scalable, Dynamo needs a careful tuning and customization of its polling policies, which are described in detail.Giacomo FiumaraMassimo MarchiAlessandro Provetti2009-11-26Z2010-04-13T11:14:33Zhttp://cab.unime.it/mus/id/eprint/549This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5492009-11-26ZInsulator-insulator and insulator-conductor transitions in the phase diagram of aluminium trichlorideWe report a classical computer-simulation study of the phase diagram of AlCl3 in the pressure-temperature (p, T) plane, showing (i) that melting from a layered crystal structure occurs into a molecular liquid at low (p, T) and into a dissociated ionic liquid at high (p, T), and (ii) that a broad transition from a molecular insulator to an ionic conductor takes place in the liquid state.Romina RubertoGiorgio PastoreMario P. Tosi2009-11-26Z2010-04-13T11:14:21Zhttp://cab.unime.it/mus/id/eprint/557This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5572009-11-26ZFurther results on approximate inertial manifolds for the FitzHugh-Nagumo modelFor two particular choices of the three parameters in the FitzHugh-Nagumo model the equilibrium points are found. The corresponding phase portrait around them is graphically represented allowing us to delimit an absorbing domain. Then the Jolly-Rosa-Temam numerical method is applied in order to study the approximate inertial manifold for the model. To this aim the own numerical code of the first author is used.Simona Cristina NarteaAdelina Georgescu2009-11-26Z2010-04-13T11:14:16Zhttp://cab.unime.it/mus/id/eprint/559This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5592009-11-26ZOn the set of coactions of an Hopf algebra on K-algebrasFor a K-Hopf algebra H, for a K-algebra A, K a field, we study when the set of coactions of H on A is closed with respect to the product of two coactions.Gaetana Restuccia2009-11-26Z2010-04-13T11:14:16Zhttp://cab.unime.it/mus/id/eprint/560This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5602009-11-26ZAn algorithm to compute primary decomposition of monomial ideals equigenerated in degree 2We give an algorithm to compute primary decomposition of monomial ideals equigenerated in degree 2 and establish connections with minimal vertex covers of a simple graph. We also describe an implementation in C++ of the algorithm.Giancarlo Rinaldo2009-11-25Z2010-04-13T11:15:23Zhttp://cab.unime.it/mus/id/eprint/520This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5202009-11-25ZThe fundamental principle for mean-periodic distributionsThe purpose of this paper is to provide a proof for a Fundamental Principle for convolution equations ...Adelina Fabiano2009-11-25Z2010-04-13T11:15:19Zhttp://cab.unime.it/mus/id/eprint/523This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5232009-11-25ZOn the finite generation of the monoid of effective divisor classes on rational surfaces of type (n, m)We prove that every projective rational surface of type (n, m) has only a finite number of (-1) curves and only a finite number of (-2) curves, where n and m are nonnegative integers satisfying the inequality mn-m-4n<0. As a consequence of this result, it follows the finite generation of the monoid of effective divisor classes on such surface. Thus giving in particular, a uniform proof of the classical results stating that the monoid of effective divisor classes on the surface obtained by blowing up the projective plane at points which are either all collinear or which are all on a conic is finitely generated.
Gioia FaillaMustapha LahyaneGiovanni Molica Bisci2009-11-25Z2010-04-13T11:14:59Zhttp://cab.unime.it/mus/id/eprint/534This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5342009-11-25ZTopological characterizations of S-linearity We give several characterizations of basic concepts of S-linear algebra in terms of weak duality on topological vector spaces. On the way, some classic results of Functional Analysis are reinterpreted in terms of S-linear algebra, by an application-oriented fashion. The results are required in the S-linear algebra formulation of infinite dimensional Decision Theory and in the study of abstract evolution equations in economical and physical Theories.David Carfì2009-11-25Z2010-04-13T11:15:21Zhttp://cab.unime.it/mus/id/eprint/519This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5192009-11-25ZA few splitting theorems for rank 2 vector bundles on P4
The paper investigates vanishing conditions on the intermediate cohomology of a normalized rank 2 vector bundle on which force to split or, at least, to be a non-stable bundle (with few possible exceptions). The results are applied to see when subcanonical surfaces in are forced to be complete intersections of two hypersurfaces, since subcanonical surfaces are zero loci of non-zero sections of rank vector bundles.
Margherita RoggeroPaolo Valabrega2009-11-25Z2010-04-13T11:15:08Zhttp://cab.unime.it/mus/id/eprint/527This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5272009-11-25ZAsymptotic waves from the point of view of double-scale method In this paper the asymptotic waves (smooth solutions of nonlinear hyperbolic partial differential equations (PDEs)) are introduced from the point of view of double scale method, giving a physical interpretation of the new (fast) variable, related to the surface across which the derivatives of the solution vary steeply.
Adelina GeorgescuLiliana Restuccia2009-11-25Z2010-04-13T11:15:07Zhttp://cab.unime.it/mus/id/eprint/528This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5282009-11-25ZVocal tecnology: A normalization approach From the 1990s onwards the use of digital technology for voice and image transmission (GSM mobile telephones, satellite transmissions and Frame Relay and ATM networks) has brought about the convergence of information technology and telecommunications, leading to the birth of the ICT (Information & Communication Technologies) sector. Currently, internal telephone networks, LANs, internet connections and geographical data transmission networks are being unified in most organizations of a certain size .
Alfio Puglisi2009-11-25Z2010-04-13T11:15:00Zhttp://cab.unime.it/mus/id/eprint/529This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5292009-11-25ZConditions (Sq) and (Gq) on graded ringsLet R be a commutative noetherian graded ring. We study SerreÂ’s condition and Ischebeck-AuslanderÂ’s condition in the graduate case. Let q be an integer, we characterize the * q-torsion freeness of graded modules on a * Gq-ring.Monica La Barbiera2009-11-25Z2010-04-13T11:15:04Zhttp://cab.unime.it/mus/id/eprint/531This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5312009-11-25ZRSA: Dagli anni '70 al giorno d'oggiIn this note, after a brief historical excursus, we describe the revolution in cryptography of the 70es, due to the introduction of public key cryptography and the RSA
algorithm. We also consider some contemporary applications of this algorithm. Modern cryptography has indeed become a commodity technology, which is currently used for
applications ranging from eÂ–commerce to digital television.Silvia Pellegrini2009-11-25Z2010-04-13T11:14:51Zhttp://cab.unime.it/mus/id/eprint/535This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5352009-11-25ZSuperpositions in distributions spaces We present a deep topological study of the operation of superposition, it is applied in several papers to phisics and economics and the study is just motivated by the increasing use of superpositions in physical and economical theories. Several characterizations in topological terms are presented, with some properties useful in the applications.
David CarfìMaria Magaudda2009-11-25Z2010-04-13T11:15:12Zhttp://cab.unime.it/mus/id/eprint/525This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5252009-11-25ZSome results on the dynamics generated by the Bazykin model A predator-prey model formerly proposed by A. Bazykin et al. [Bifurcation diagrams of planar dynamical systems (1985)] is analyzed in the case when two of the four parameters are kept fixed. Dynamics and bifurcation results are deduced by using the methods developed by D. K. Arrowsmith and C. M. Place [Ordinary differential equations (1982)], S.-N. Chow et al. [Normal forms and bifurcation of planar fields (1994)], Y. A. Kuznetsov [Elements of applied bifurcation theory (1998)], and A. Georgescu [Dynamic bifurcation diagrams for some models in economics and biology (2004)]. The global dynamic bifurcation diagram is constructed and graphically represented. The biological interpretation is presented, too.
Raluca Mihaela GeorgescuAdelina Georgescu2008-03-03Z2010-04-13T11:16:11Zhttp://cab.unime.it/mus/id/eprint/476This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4762008-03-03ZOptimal boundaries for decisions In this paper we state and prove some new results on the optimal boundaries. These boundaries (called Pareto boundaries too) are of increasing importance in the applications to Decision Theory. First of all the Pareto boundaries are the first and most important generalization of the concept of optimum; on the other hand, if f is a real functional defined on a non empty set X and K is a part of X, the determination of the optimal boundaries of the part K with respect to some preorder ? of X for which f is strictly increasing permits to reduce the optimization problem (f, K, inf) (or (f, K, sup)) to the problem (f, minP(K), inf) (resp. (f, maxP(K), sup)), where by minP(K) we denoted the minimal boundary of K (that in general is greatly smoller than K).
David Carfì2008-01-28Z2010-04-13T11:17:00Zhttp://cab.unime.it/mus/id/eprint/450This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4502008-01-28ZNon equilibrium thermodynamics with internal variables in Kluitenberg's theoryWe show a method to verify experimentally some inequalities which occur for phenomenological coefficients in the thermodynamical model for dielectric relaxation and viscoanelastic media developed in the ambit of non-equilibrium thermodynamic Kluitenberg's theory. In particular, for dielectric relaxation we assume a sinusoidal form for induction vector (extensive variable: cause), the electric field (intensive variable: effect) inside the system, which depends on unknown phenomenological coefficients, has been obtained by integration. Then we compare it with a similar form of the electric field obtained by experimental considerations, where well known experimentally determinable coefficients appear. We carry out dielectric measurements on PMMA and PVC at different frequencies and fixed temperature in order to obtain the phenomenological coefficients as functions of the frequency. For viscoanelastic media we consider the relative rheological equation and we compare the solution of this equation with a well known expression of the stress obtained, by experimentally considerations, in the linear response theory. This comparison will be able to determine the phenomenological an state coefficients as function of frequency dependent quantities experimentally measurable. This method will be applied to polymeric materials as Polyisobutilene. Vincenzo Ciancio2008-01-28Z2010-04-13T11:16:29Zhttp://cab.unime.it/mus/id/eprint/467This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4672008-01-28ZWaves propagation in superfluid helium in presence of combined rotation and counterflow Using the linear macroscopic mono-fluid model of liquid helium II, in which the fundamental fields are the density ?, the velocity v, the temperature T and heat flux q and taking into account the expression of an additional pressure tensor P(w), introduced to describe phenomena linked to vortices, a complete study of wave propagation is made in the complex situation involving thermal counterflow in a rotating cylinder.
Rosa Anna PeruzzaMichele Sciacca2008-01-28Z2010-04-13T11:16:30Zhttp://cab.unime.it/mus/id/eprint/468This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4682008-01-28ZIndefinite metric of R. Mrugala and the geometry of thermodynamical phase space We study an indefinite metric G which was introduced by R. Mrugala and is defined on the contact phase space (P,?) of a homogeneous thermodynamical system. We describe the curvature properties and the isometry group of the metric G. We established an isomorphism of the space (P,?,G) with the Heisenberg Lie group Hn, endowed with the right invariant contact structure and the right invariant indefinite metric. The lift of the metric G to the symplectization of contact space (P,?) and its properties are studied. Finally we introduce the "hyperbolic projectivization" of the space () that can be considered as the natural compactification of the thermodynamical phase space (P, q, G).
Serge PrestonJames Vargo2008-01-28Z2012-09-20T06:54:58Zhttp://cab.unime.it/mus/id/eprint/457This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4572008-01-28ZThermodynamics of heterogeneous and anisotropic nonlinear ferroelastic crystals
In a previous paper, in a geometrized framework for the description of simple materials with internal variables, the specific example of ferroelastic crystals with anisotropy grain-tensors Ã la Maruszewski was considered and the relevant structure of the entropy 1-form was derived. In this contribution the linear morphism defined on the fibre bundle of the process and the transformation induced by the process are obtained as new results within the geometrical model. Furthermore, Clausius-Duhem inequality for these media is exploited, and, using a Maugin technique (see also Colemann-Noll procedure), the laws of state, the extra entropy flux and the residual dissipation inequality are worked out. Finally, following Maugin, the heat equation in the first and the second form are derived.
Mauro FrancavigliaLiliana Restuccia2008-01-28Z2010-04-13T11:16:49Zhttp://cab.unime.it/mus/id/eprint/456This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4562008-01-28ZNon-equilibrium thermodynamics with higher order fluxes: Balance laws and exploitation of the entropy inequality Weakly non-local extended thermodynamics of rigid heat conductors is presented. The two celebrated procedures by Coleman-Noll and Liu for the exploitation of second law of thermodynamics are compared. It is proved that the two procedures are equivalent, if in the Coleman-Noll procedure all relevant equations are taken into account as constraints.Vito Antonio CimmelliWolfgang MuschikVita Triani2008-01-28Z2010-04-13T11:16:56Zhttp://cab.unime.it/mus/id/eprint/454This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4542008-01-28ZSuperpositions in Prigogine's approach to irreversibility for physical and financial applications In this paper we apply the theory of superpositions for Radon measures on compact subsets of the real Euclidean n-space R^n to Prigogine's approach in the study of irreversible processes, which emerge in physics and in economics, showing that the superposition is a natural rigorous tool feasible to face the problem.
David Carfì2008-01-28Z2012-09-20T08:30:09Zhttp://cab.unime.it/mus/id/eprint/465This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4652008-01-28ZIntroduction to the thermomechanics of configurational forces Configurational forces are thermodynamic conjugates to irreversible material body evolutions such as extension of cracks, progress of phase-transition fronts, movement of shock waves, etc. They do correspond to a change of material configuration. Accordingly, their realm is the material manifold of a body. Furthermore, they acquire a physical meaning only in so far as they contribute to the global dissipation. Therefore, the present contribution of a pedagogical nature proposes a primer introduction to the thermodynamics of configurational forces. To that purpose, we first introduce a consistent thermomechanics of general deformable continua on the material manifold (and not in physical space). This is achieved in a canonical manner by full projection of the balance equation of momentum onto the material manifold and constructing in parallel a formally consistent expression of the energy conservation. Then various configurational forces such as those appearing in inhomogeneous bodies, at the tip of a propagating crack, at the surface of a propagating phase-transition front, or of a shock wave, and those due to local structural rearrangements (plasticity, damage, growth), are examined from the point of view of their dissipated power.
Gérard A. MauginArkadi Berezovski2008-01-16Z2010-04-13T11:17:07Zhttp://cab.unime.it/mus/id/eprint/448This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4482008-01-16ZCohen Macaulay fibres of a morphism We present the main results about morphisms whose fibres are Cohen-Macaulay and about rings having Cohen-Macaulay formal fibers. We give new proofs for the localization theorems for morphisms with Cohen-Macaulay or (Sn) fibres and we point out some open questions in this direction. Cristodor Ionescu2007-10-09Z2010-04-13T11:17:04Zhttp://cab.unime.it/mus/id/eprint/446This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4462007-10-09ZComplete intersections in P2 through separating sequences
In this paper we characterize the finite sets of points in P2, arising as a complete intersection of two curves, by means of their realizable sequences. Actually, we show that a reduced 0-dimensional scheme in P2 is a complete intersection of type (a, b) iff all its realizable sequences can be obtained by means of direct transpositions from a special one Mab.
Carla MassazaGiannina Beccari2007-10-09Z2010-04-13T11:17:12Zhttp://cab.unime.it/mus/id/eprint/445This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4452007-10-09ZGeneralizing double graphs In this paper we study the graphs which are direct product of a simple graph G with the graphs obtained by the complete graph Kk adding a loop to each vertex; thus these graphs turn out to be a generalization of the double graphs. Maria Corinna MarinoNorma Zagaglia Salvi2007-10-09Z2010-04-13T11:17:05Zhttp://cab.unime.it/mus/id/eprint/447This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4472007-10-09ZAsymptotic study of the Rayleigh equation This paper provides an asymptotic treatment of the Cauchy problem for the Rayleigh equation ÂµÃ¿ + ?3/3 + ay Â– ? = 0 modelling a harmonic oscillator. The method of boundary layer functions and our version of the Tikhonov theorem are used. The models of asymptotic approximations are derivedMarin-Nicolae PopescuGheorghescu Nistor2007-04-16Z2010-04-13T11:17:37Zhttp://cab.unime.it/mus/id/eprint/429This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4292007-04-16ZOn the k-unirationality of the cubic complexWe show that the complete intersection V = V (2, 3) ! P5 of a quadric
and a cubic in 5-dimensional projective space defined over a field k, of char. "= 2, 3, is
unirational over this field k itself if moreover V has a point p rational over k and if one of
the two planes through p on the quadric is also rational over k.Alberto ConteMarina MarchisioJacob P. Murre2007-04-16Z2010-04-13T11:17:38Zhttp://cab.unime.it/mus/id/eprint/430This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4302007-04-16ZActions of formal groups on special quotients of algebrasLet k be a field of characteristic p > 0 and let F be a one dimensional
commutative formal group over k. The endomorphisms of a k-algebra A that defines an
action of F on A when A is isomorphic to the quotient B/pB, with B torsion free Zalgebra,
are studied.Marilena CrupiGaetana Restuccia2007-04-16Z2010-04-13T11:17:31Zhttp://cab.unime.it/mus/id/eprint/432This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/4322007-04-16ZA generalization of minimal distributionsWe connect here various harmonic geometric objects (including a generalization of minimal distributions that we define here), we relate them with the theory of
foliations and we construct some examples.Cornelia Livia BejanMassimiliano Ferrara2007-02-13Z2010-04-13T11:17:52Zhttp://cab.unime.it/mus/id/eprint/399This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3992007-02-13ZQuantum-Classical Dynamics of Wave FieldsAn approach to the quantum-classical mechanics of
phase space dependent operators, which has been proposed recently, is remodeled as a formalism for wave fields.
Such wave fields obey a system of coupled non-linear equations that can be written by means of a suitable non-Hamiltonian bracket.
As an example, the theory is applied to the relaxation dynamics of the spin-boson model.
In the adiabatic limit, a good agreement with calculations
performed by the operator approach is obtained.
Moreover, the theory proposed in this paper
can take nonadiabatic effects into account
without resorting to surface-hopping approximations.
Hence, the results obtained follow qualitatively those
of previous surface-hopping calculations
and increase by a factor of (at least) two the time length
over which nonadiabatic dynamics can be propagated
with small statistical errors.
Moreover, it is worth to note that the dynamics of
quantum-classical wave fields here proposed is a straightforward non-Hamiltonian generalization of the formalism for non-linear quantum mechanics that Weinberg introduced recently.Alessandro Sergiasergi@unime.it2006-05-12Z2010-04-13T11:17:55Zhttp://cab.unime.it/mus/id/eprint/392This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3922006-05-12ZQuantum-Classical Dynamics of Wave FieldsThe recent approach to the quantum-classical mechanics of
phase space dependent operators is recast
into a formalism for wave fields.
It turns out that such wave fields
obey a system of coupled non-linear equations where
each equation is not Hermitian. However,
backward and forward time-evolution
is combined in such a way as to conserve probability.
Notwithstanding their non-linear form, the equations of motion
for such phase space dependent wave fields can be
expressed by means of a suitable non-Hamiltonian bracket.
Thus, it can be realized that the non-Hamiltonian dynamics of
quantum-classical wave fields is a straightforward
generalization of the formalism for non-linear
quantum mechanics that Weinberg proposed recently.Alessandro Sergiasergi@unime.it2005-12-02Z2010-04-13T11:19:28Zhttp://cab.unime.it/mus/id/eprint/354This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3542005-12-02ZNon-Hamiltonian Quantum Mechanics.
Relation between operator and wave schemes of motionThe symplectic structure of Weinberg's formalism for nonlinear
quantum mechanics is first unveiled and then generalized
to introduce non-Hamiltonian quantum mechanics.
By exploiting the correspondence between wave
and matrix mechanics, a link between this generalization
and a non-Hamiltonian commutator, proposed recently by this author,
is found.
The general correspondence between operator and wave formalisms
in non-Hamiltonian quantum mechanics
is exploited to introduce a quantum-classical theory
of wave fields.
This can be considered as a first step toward a deeper
understanding of the relation between operator quantum-classical
mechanics, introduced some time ago, and the original
quantum-classical scheme of motion where
wave functions are evolved in time and
the classical degrees of freedom follows
surface-hopping trajectories on single quantum states.Alessandro Sergiasergi@unime.it2005-11-23Z2010-04-13T11:19:36Zhttp://cab.unime.it/mus/id/eprint/350This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3502005-11-23ZOn the Geometry of Non-Hamiltonian Phase SpaceIn this paper the statistical mechanics of canonical,
non-canonical and non-Hamiltonian systems is analyzed rigorously
by throwing light onto the peculiar geometric structure of phase
space. Misleading points, regarding generalized brackets and
Jacobi relations, are clarified. The accessory role of phase space
compressibility in the statistical mechanics of non-canonical and
non-Hamiltonian systems is also unveiled. A rigorous definition of
the (relative) entropy for continuous probability distributions is
adopted and used in order to introduce maximum entropy principles
for non-canonical and non-Hamiltonian systems. Although the
attention is concentrated on the geometry of phase space under
equilibrium thermodynamic conditions, the results and the points of view
presented lay the foundations for a maximum entropy approach to
non-Hamiltonian dissipative systems.Alessandro Sergiasergi@unime.it2005-11-23Z2010-04-13T11:19:39Zhttp://cab.unime.it/mus/id/eprint/351This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3512005-11-23ZStatistical Mechanics of Quantum-Classical Systems with Holonomic ConstraintsThe statistical mechanics of quantum-classical systems
with holonomic constraints
is formulated rigorously by unifying the classical Dirac bracket and the
quantum-classical bracket in matrix form.
The resulting Dirac quantum-classical
theory, which conserves the holonomic constraints exactly, is then used
to formulate time evolution and statistical mechanics.
The correct momentum-jump approximation for constrained system arises
naturally from this formalism.
Finally, in analogy with what was found in the classical case, it
is shown that the rigorous linear
response function of constrained quantum-classical systems
contains non-trivial additional terms which are absent
in the response of unconstrained systems.Alessandro Sergiasergi@unime.it2005-11-14Z2010-04-13T11:19:48Zhttp://cab.unime.it/mus/id/eprint/348This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3482005-11-14ZNon-Hamiltonian Commutators in Quantum MechanicsThe symplectic structure of quantum commutators is first unveiled and then exploited
to introduce generalized non-Hamiltonian brackets in quantum mechanics.
It is easily recognized that quantum-classical systems
are described by a particular realization of such a bracket.
In light of previous work, this introduces
a unified approach to classical and
quantum-classical non-Hamiltonian dynamics.
In order to illustrate the use
of non-Hamiltonian commutators, it is shown how to define
thermodynamic constraints in quantum-classical systems.
In particular, quantum-classical Nos\'e-Hoover equations of motion
and the associated stationary density matrix are derived.
The non-Hamiltonian commutators for both Nos\'e-Hoover chains
and Nos\'e-Andersen (constant-pressure constant temperature)
dynamics are also given.
Perspectives of the formalism are discussed.Alessandro Sergiasergi@unime.it2005-09-26Z2010-04-13T11:20:13Zhttp://cab.unime.it/mus/id/eprint/334This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3342005-09-26ZPhase space flows for non-Hamiltonian systems with constraintsIn this paper, non-Hamiltonian systems with holonomic constraints
are treated by a generalization of Dirac's formalism.
Non-Hamiltonian phase space flows can be described
by generalized antisymmetric brackets
or by general Liouville operators which cannot be derived
from brackets. Both situations are treated.
In the first case, a Nos\'e-Dirac
bracket is introduced as an example.
In the second one, Dirac's recipe for
projecting out constrained variables from time translation operators
is generalized and then applied to non-Hamiltonian linear response.
Dirac's formalism avoids spurious terms in the response function
of constrained systems. However, corrections coming from phase
space measure must be considered for general perturbations.Alessandro Sergi