The various experimental sectors of physics in which superluminal motions seem to appear are brie... more The various experimental sectors of physics in which superluminal motions seem to appear are briefly mentioned. In particular, a bird's-eye view is presented of the experiments with evanescent waves (and/or tunneling photons) and with the "localized superluminal solutions" (SLS) to the wave equation, like the so-called X-shaped beams. The authors also present a series of new SLSs to the Maxwell equations, suitable for arbitrary frequencies and arbitrary bandwidths, some of them endowed with finite total energy. Among the others, the authors set forth an infinite family of generalizations of the classical X-shaped wave and show how to deal with the case of a dispersive medium. Results of this kind may find application in other fields in which an essential role is played by a wave equation (like acoustics, seismology, geophysics, gravitation, elementary particle physics, etc.).
In this paper we present a theoretical method, together with its experimental confirmation, to ob... more In this paper we present a theoretical method, together with its experimental confirmation, to obtain structures of light by connecting diffraction-resistant cylindrical beams of finite lengths and different radii. The resulting ``Lego-beams'' can assume, on demand, various interesting spatial configurations. We experimentally generate some of them by using a computational holographic technique and a Spatial Light Modulator. Our results can find applications in all fields where structured light beams are needed, such as optical tweezers, optical guiding of atoms, light orbital angular momentum control and others. [OCIS codes: (999.9999) Non-diffracting waves; (260.1960) Diffraction theory; (070.7545) Wave propagation; (050.1120) Apertures; (050.1755) Computational electromagnetic methods].
In previous papers we investigated the classical theory of Barut and Zanghi (BZ) for the electron... more In previous papers we investigated the classical theory of Barut and Zanghi (BZ) for the electron spin [who interpreted the Zitterbewegung (zbw) motion as an internal motion along helical paths], and its " quantum " version, just by using the language of Clifford algebras; and, in so doing, we ended with a new non-linear Dirac-like equation (NDE). We want to re-address in this Review the whole subject, and extend it, by translating it however into the ordinary tensorial language, within the frame of a first quantization formalism. In particular, we re-derive here the NDE for the electron field, and show it to be associated with a new conserved probability current (which allows us to work out a " quantum probabilistic " interpretation of the NDE). Incidentally, the Dirac equation results from the former by averaging over a zbw cycle. Afterward, we derive an equation of motion for the 4-velocity field, which allows us to regard the electron as an extended-like object with a classically intelligible internal structure. We carefully study the solutions of the NDE; with special attention to those implying (at the classical limit) light-like helical motions, since they appear to be the most adequate solutions for the electron description from the kinematical and physical points of view, and do cope with the electromagnetic properties of the electron.
At last we introduce a natural generalization of our approach, for the case in which an external electromagnetic potential A^\mu is present; it happens to be based on a new system of five first-order differential field equations.
At the kind request of the Editor of this Journal, and of TEC/TNRG (Usa), we recall in this artic... more At the kind request of the Editor of this Journal, and of TEC/TNRG (Usa), we recall in this article some elementary historical information about the role played by Ettore Majorana[l-17] with regard to the Neutron, and to the Neutrino. We often do explicitly insert direct quotations from the original written statements-in particular by Edoardo Amaldi[22-24]-, which in some cases, and for some topics, constitute the main available evidence. We also reply to some recent (unjustified) rumors about Enrico Fermi and Ettore Majorana.
The recent literature shows a renewed interest, with various independent approaches, in the class... more The recent literature shows a renewed interest, with various independent approaches, in the classical theories for spin. Considering the possible interest of those results, at least for the electron case, we purpose in this paper to explore their physical and mathematical meaning, by the natural and powerful language of Clifford algebras (which, incidentally, will allow us to unify those different approaches). In such theories, the ordinary electron is in general associated to the mean motion of a point-like "constituent" Q, whose trajectory is a cylindrical helix. We find, in particular, that the object Q obeys a new, non-linear Dirac-like equation, such that -when averaging over an internal cycle (which corresponds to linearization)-it transforms into the ordinary Dirac equation (valid for the electron as a whole).
articolo giornalistico apparso su "L'Eco di Bergamo" nel settore Scienze e Coscienze il 13.03.200... more articolo giornalistico apparso su "L'Eco di Bergamo" nel settore Scienze e Coscienze il 13.03.2005 e occupante le intere due pagine 4 e 5 / Popularization article
In recent times, we (theoretically and) experimentally realized quite an efficient modeling of th... more In recent times, we (theoretically and) experimentally realized quite an efficient modeling of the shape of diffraction-resistant optical beams, thus generating for the first time the so-called Frozen Waves (FW), whose longitudinal intensity pattern can be arbitrarily chosen within a prefixed space interval of the propagation axis. In this Letter, we extend our theory of FWs, which led to beams endowed with a static envelope, through a dynamic modeling of the FWs whose shape is now allowed to slowly evolve in time in a predetermined way. Further, we experimentally create such dynamic FWs (DFWs) in Optics via a computational holographic technique and a spatial light modulator. Experimental results are presented here for two cases of DFWs, one of zeroth order and the other of higher order, the latter being the most interesting, since it exhibits a cylindrical surface of light whose geometry changes in space and time.
In Italian AND in English -- IN ITALIAN: Si dà notizia delle scoperte: a) del "Riparo Longo", gi... more In Italian AND in English -- IN ITALIAN: Si dà notizia delle scoperte: a) del "Riparo Longo", giacimento preistorico tardi-gravettiano all'interno della Sicilia Orientale, presso Agira (EN); b) della prima stazione paleolitica sup. a ben 1500 m di altitudine in Sicilia, nel cuore delle montagne Madonìe (Valle Marabilice, comune di Isnello, PA); e soprattutto: c) di una dozzina di stazioni con industria di tipo paleolitico inferiore nella Sicilia orientale. La ricca presenza di industrie apparentemente clactoniana, proto-levalloisiana e perfino olduvaiana ("pebble culture" smentiscono la convinzione che la Sicilia sia sterile nel Paleolitico interiore. ABSTRACT IN ENGLISH - We put forth notice of the following discoveries: (i) of the "Longo shelter", prehistoric epi-gravettian bed in the interior of East Sicily, near Agira (EN); (ii) of the first Upper-Paleolithical station found at 1,500 m altitude in Sicily in the heart of the Madonìe mountains (Valle Marabilice, Isnello commune, PA); and before all: (iii) of a dozen of Lower-Paleolithical industrtry localities in East Sicily. The abundance of apparently clactonian, proto-levalloisian, and even olduvaian (pebble culture) industried disproves the old conviction that Sicily was Lower-Paleolithically sterile.
Si riportano una serie di fenomeni crionivali (anticamente detti anche "periglaciali") osservati ... more Si riportano una serie di fenomeni crionivali (anticamente detti anche "periglaciali") osservati negli anni 1959 e 1961 in Val di Sole
RECENTI SCOPERTE SUL PALEOLITICO SICILIANO, et alia
In alcuni articoli del 1976 (e 1977) si diede notizia della scoperta di numerosi giacimenti di ma... more In alcuni articoli del 1976 (e 1977) si diede notizia della scoperta di numerosi giacimenti di manufatti litici di industria di tipo paleolitico inferiore --soprattutto industrie di tipo clactoniano e proto-levalloisiano, e probabile pebble culture--, situati ad esempio lungo il fiume Simeto o nei pressi del fiume Dittaino. Uno studio (posteriore) dei manufatti è stato effettuato da Anna Revedin A. M., dell'I.I.P.P. di Firenze, e pubblicato sulla Rivista di Scienze Preistoriche: tale articolo viene copiato al termine del file.pdf qui presentato.
Nel 1976-1977 si è data notizia in vari articoli, qui allegati, della scoperta in contrada Piccon... more Nel 1976-1977 si è data notizia in vari articoli, qui allegati, della scoperta in contrada Piccone presso Mandarano e sul fiume Simeto (in comune di Centuripe, EN, Sicilia) di un riparo sotto roccia caratterizzato --tra l'altro-- da numerose pitture in ocra (rossa) ascrivibili probabilmente al Neolitico medio. Fu allora visitato da Paolo Graziosi e da Mara Guerri (IIPP, Firenze).
A seguito di una nostra piccola campagna glaciologica (1959), nel 1961 ho effettuato alcune ulter... more A seguito di una nostra piccola campagna glaciologica (1959), nel 1961 ho effettuato alcune ulteriori osservazioni sullo stato dei ghiacciaietti della Val di Rabbi (Val di Sole, TN) con l'aiuto di un altimetro. Dato che queste osservazioni non giunsero in tempo [vedere ad es. la lettera di G.Nangeroni riprodotta alla fine] per la eventuale inclusione nel Catasto dei Ghiacciai Italiani del 1957-1958, Vol.III, vengono qui aggiunte le copie di numerose pagine del detto Catasto con l'inserimento manuale di varie nostre fotografie di possibile interesse: e ciò non solo per la Val di Rabbi, ma anche per la Val di Peio.
Biografia sintetica di MAJORANA Ettore, per il Dizionario Biografico degli Italiani (Treccani), v... more Biografia sintetica di MAJORANA Ettore, per il Dizionario Biografico degli Italiani (Treccani), vol.67
Special Relativity can be based on the whole proper group of both ortho-and antichronous Lorentz ... more Special Relativity can be based on the whole proper group of both ortho-and antichronous Lorentz transformations, and a clear physical meaning can be given also to antichronous G.e., nonorthochronous) Lorentz transformations. From the active point of view, the latter requires existence, for any particle, of its antiparticle within a purely relativistic, classical context, From the passive point of view, they give rise to frames "dua" to the ordinary ones, whose properties --here brieflydiscussed-- are linked with the fact that in relativity it is impossible to teach another, far observer (by transmitting only instructions, and no physical objects) our own conventions about the choices right/left, matter/antimatter, and positive/negative time direction. Interesting considerations follow, in particular, by considering --as it is the case-- the CPT operation as an actual (even if antichronous) Lorentz transformation.
In a previous paper we have shown localized nonevanescent solutions to Maxwell equations to exist... more In a previous paper we have shown localized nonevanescent solutions to Maxwell equations to exist, which propagate without distortion with superluminal speed along normal-sized waveguides, and consist in trains of ''X-shaped'' beams. Those solutions possessed infinite energy. In this paper we show how to obtain, by contrast, finite-energy solutions, with the same localization and superluminality properties.
In a previous paper we showed that localized superluminal solutions to the Maxwell equations exis... more In a previous paper we showed that localized superluminal solutions to the Maxwell equations exist, which propagate down nonevanescence regions of a metallic cylindrical waveguide. In this paper we construct analogous nondispersive waves propagating along coaxial cables. Such new solutions, in general, consist in trains of undistorted superluminal ''X-shaped'' pulses. Particular attention is paid to the construction of finite total energy solutions. Any results of this kind may find application in the other fields in which an essential role is played by a wave equation like acoustics, geophysics, etc..
In this paper we analyze the effects of the time modulation of (zeroth-order) Bessel beams, by co... more In this paper we analyze the effects of the time modulation of (zeroth-order) Bessel beams, by considering a few different pulse shapes. Namely, three modulating functions are considered: a train of rectangular waves, a single rectangular pulse, and a gaussian pulse. The influence of the carrier frequency, and of shape and spectral bandwidth of the modulating function, is also discussed; while further support to our results is met by using the convolution technique in the time domain. At the beginning, a brief review of the X-shaped solutions to the wave equation, and of some properties of theirs, is presented.
In this paper, we start from the well known DurninÕs experimental setup, finding general analytic... more In this paper, we start from the well known DurninÕs experimental setup, finding general analytical formulae to investigate generation and propagation of nondiffracting beams. Our general formula makes possible considering any kind of angular modulation. As an example we discuss the Mathieu beams. Moreover, in the study of Bessel beams we consider the width of the slit to compare with the ideal case represented by a Dirac d transmittance function.
Tunneling of optical pulses at 1.5 m wavelength through double-barrier periodic fiber Bragg grati... more Tunneling of optical pulses at 1.5 m wavelength through double-barrier periodic fiber Bragg gratings is experimentally investigated in this paper. Tunneling time measurements as a function of the barrier distance show that, far from resonances of the structure, the transit time is paradoxically short—implying superluminal propagation—and almost independent of the barrier distance. This result is in agreement with theoretical predictions based on phase-time analysis and provides, in the optical context, an experimental evidence of the analogous phenomenon in quantum mechanics of nonresonant superluminal tunneling of particles across two successive potential barriers.
—The various experimental sectors of physics in which superluminal motions seem to appear are bri... more —The various experimental sectors of physics in which superluminal motions seem to appear are briefly mentioned. In particular, a bird's-eye view is presented of the experiments with evanescent waves (and/or tunneling photons) and with the " localized superluminal solutions " (SLS) to the wave equation, like the so-called X-shaped beams. The authors also present a series of new SLSs to the Maxwell equations, suitable for arbitrary frequencies and arbitrary bandwidths, some of them endowed with finite total energy. Among the others, the authors set forth an infinite family of generalizations of the classical X-shaped wave and show how to deal with the case of a dispersive medium. Results of this kind may find application in other fields in which an essential role is played by a wave equation (like
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Papers by Erasmo Recami
interesting spatial configurations. We experimentally generate
some of them by using a computational holographic technique and a
Spatial Light Modulator. Our results can find applications in all
fields where structured light beams are needed, such as optical
tweezers, optical guiding of atoms, light orbital angular momentum
control and others. [OCIS codes: (999.9999) Non-diffracting waves; (260.1960) Diffraction theory; (070.7545) Wave propagation; (050.1120)
Apertures; (050.1755) Computational electromagnetic methods].
At last we introduce a natural generalization of our approach, for the case in which an external electromagnetic potential A^\mu is present; it happens to be based on a new system of five first-order differential field equations.
ABSTRACT IN ENGLISH - We put forth notice of the following discoveries: (i) of the "Longo shelter", prehistoric epi-gravettian bed in the interior of East Sicily, near Agira (EN); (ii) of the first Upper-Paleolithical station found at 1,500 m altitude in Sicily in the heart of the Madonìe mountains (Valle Marabilice, Isnello commune, PA); and before all: (iii) of a dozen of Lower-Paleolithical industrtry localities in East Sicily. The abundance of apparently clactonian, proto-levalloisian, and even olduvaian (pebble culture) industried disproves the old conviction that Sicily was Lower-Paleolithically sterile.
Dato che queste osservazioni non giunsero in tempo [vedere ad es. la lettera di G.Nangeroni riprodotta alla fine] per la eventuale inclusione nel Catasto dei Ghiacciai Italiani del 1957-1958, Vol.III, vengono qui aggiunte le copie di numerose pagine del detto Catasto con l'inserimento manuale di varie nostre fotografie di possibile interesse: e ciò non solo per la Val di Rabbi, ma anche per la Val di Peio.