Papers by marcello lissia
arXiv (Cornell University), Feb 1, 1999
We present a quantitative estimate of the accuracy of the calculated diffusion coefficients, by c... more We present a quantitative estimate of the accuracy of the calculated diffusion coefficients, by comparing predictions of solar models with observational data provided by helioseismology. By taking into account the major uncertainties in building solar models we conclude that helioseismology confirms the diffusion efficiency adopted in SSM calculations, to the 10% level.
Relativistic Aspects of Nuclear Physics, 1998
AIP Conference Proceedings, 2005
We analyze how different non-extensive, generalized entropic forms evolve in time for the logisti... more We analyze how different non-extensive, generalized entropic forms evolve in time for the logistic map at the onset of chaos, together with the associated sensitivity forms. Numerical evidence is given for the existence of an entropic index for which each entropy and the corresponding sensitivity increase linearly in time. The analogue of the Pesin equality is recovered when sensitivity to
Entropy, 2016
Negentropy (negative entropy) is the negative contribution to the total entropy of correlated man... more Negentropy (negative entropy) is the negative contribution to the total entropy of correlated many-body environments. Negentropy can play a role in transferring its related stored mobilizable energy to colliding nuclei that participate in spontaneous or induced nuclear fusions in solid or liquid metals or in stellar plasmas. This energy transfer mechanism can explain the observed increase of nuclear fusion rates relative to the standard Salpeter screening. The importance of negentropy in these specific many-body quantum systems and its relation to many-body correlation entropy are discussed.
Recent progresses in statistical mechanics indicate the Tsallis nonextensive thermostatistics as ... more Recent progresses in statistical mechanics indicate the Tsallis nonextensive thermostatistics as the natural generalization of the standard classical and quantum statistics, when memory effects and long-range forces are not negligible. In this framework, weakly nonextensive statistical deviations can strongly reduce the puzzling discrepancies between experimental data and theoretical previsions for solar neutrinos and for pion transverse-momentum correlations in Pb-Pb high-energy
Physica A: Statistical Mechanics and its Applications, 2003
The excess of solar-neutrino events above 13 MeV that has been recently observed by Superkamiokan... more The excess of solar-neutrino events above 13 MeV that has been recently observed by Superkamiokande can be explained by vacuum oscillations (VO). If the boron neutrino flux is 20% smaller than the standard solar model (SSM) prediction and the chlorine signal is assumed 30% (or 3.5σ) higher than the measured one, there exists a VO solution that reproduces both the observed boron neutrino spectrum, including the high energy distortion, and the other measured neutrino rates. This solution is already testable by the predicted anomalous seasonal variation of the gallium signal. Its most distinct signature, a large anomalous seasonal variation of 7 Be neutrino flux, can be easily observed by the future detectors, BOREXINO and LENS.
Nuclear Physics B - Proceedings Supplements, 2005
The detection of neutrinos from U, Th, and K decay in the Earth (geo-neutrinos) will help to fix ... more The detection of neutrinos from U, Th, and K decay in the Earth (geo-neutrinos) will help to fix the total amount of long-lived radioactive elements and thus the radiogenic contribution to the terrestrial heat. Moreover, it will provide a direct test of a fundamental paradigm about the origin, formation and structure of the Earth, i.e., the Bulk Silicate Earth model. Alternative or variant models of Earth (including the presence of potassium or the possibility of a giant reactor in the core) can also be checked. This short review presents the status and prospects in this exciting field of research.
Theoretical Nuclear Physics in Italy - Proceedings of the 9th Conference on Problems in Theoretical Nuclear Physics, 2003
Complexity, Metastability and Nonextensivity, 2005
Numerical experiments support the interesting conjecture that statistical methods be applicable n... more Numerical experiments support the interesting conjecture that statistical methods be applicable not only to fully-chaotic systems, but also at the edge of chaos by using Tsallis' generalizations of the standard exponential and entropy. In particular, the entropy increases linearly and the sensitivity to initial conditions grows as a generalized exponential. We show that this conjecture has actually a broader validity by using a large class of deformed entropies and exponentials and the logistic map as test cases.
Progress of Theoretical Physics, 2006
Asymptotically entropy of chaotic systems increases linearly and the sensitivity to initial condi... more Asymptotically entropy of chaotic systems increases linearly and the sensitivity to initial conditions is exponential with time: these two behaviors are related. Such relationship is the analogous of and under specific conditions has been shown to coincide with the Pesin identity. Numerical evidences support the proposal that the statistical formalism can be extended to the edge of chaos by using a specific generalization of the exponential and of the Boltzmann-Gibbs entropy. We extend this picture and a Pesin-like identity to a wide class of deformed entropies and exponentials using the logistic map as a test case. The physical criterion of finite-entropy growth strongly restricts the suitable entropies. The nature and characteristics of this generalization are clarified.
Physics Reports, 2007
The deepest hole that has ever been dug is about 12 km deep. Geochemists analyze samples from the... more The deepest hole that has ever been dug is about 12 km deep. Geochemists analyze samples from the Earth's crust and from the top of the mantle. Seismology can reconstruct the density profile throughout all Earth, but not its composition. In this respect, our planet is mainly unexplored. Geo-neutrinos, the antineutrinos from the progenies of U, Th and 40 K decays in the Earth, bring to the surface information from the whole planet, concerning its content of natural radioactive elements. Their detection can shed light on the sources of the terrestrial heat flow, on the present composition, and on the origins of the Earth. Geo-neutrinos represent a new probe of our planet, which can be exploited as a consequence of two fundamental advances that occurred in the last few years: the development of extremely low background neutrino detectors and the progress on understanding neutrino propagation. We review the status and the prospects of the field.
Physics Letters B, 2001
With SNO data [1] on electron-neutrino flux from the sun, it is possible to derive the ν e surviv... more With SNO data [1] on electron-neutrino flux from the sun, it is possible to derive the ν e survival probability P ee (E) from existing experimental data of Super-Kamiokande, gallium experiments and Homestake. The combined data of SNO and Super-Kamiokande provide boron ν e flux and the total flux of all active boron neutrinos, giving thus P ee (E) for boron neutrinos. The Homestake detector, after subtraction of the signal from boron neutrinos, gives the flux of Be+CNO neutrinos, and P ee for the corresponding energy interval, if the produced flux is taken from the Standard Solar Model (SSM). Gallium detectors, GALLEX, SAGE and GNO, detect additionally pp-neutrinos. The pp flux can be calculated subtracting from the gallium signal the rate due to boron, beryllium and CNO neutrinos. The ratio of the measured ppneutrino flux to that predicted by the SSM gives the survival probability for pp-neutrinos. Comparison with theoretical survival probabilities shows that the best (among known models) fit is given by LMA and LOW solutions.
Physics Letters B, 1995
The concept of dimensional reduction in the high temperature regime is generalized to static Gree... more The concept of dimensional reduction in the high temperature regime is generalized to static Green's functions of composite operators that contain fermionic fields. The recognition of a natural kinematic region where the lowest Matsubara modes are close to their mass-shell, and the ultraviolet behavior of the running coupling constant of the original theory are crucial for providing the necessary scale hierarchy. The general strategy is illustrated in the asymptotically-free Gross-Neveu model in 1 + 1 dimensions, where we verify that dimensional reduction occurs to the leading order in g 2 (T). We also find, in the same model, that the scale parameter characterizing the dependence on temperature of the coupling constant in the reduced theory, Λ T , is considerably smaller than Λ MS. Implications of our results for QCD are also discussed.
Physics Letters B, 1994
translated into a strict prediction on <I>pcp. In order to analyze the relevance of an experiment... more translated into a strict prediction on <I>pcp. In order to analyze the relevance of an experiment on pep neutrinos, OCR Output The pep and pp reactions are strongly connected with each other [9], so that one expects eq (1.1) can be of this limit will be a clear signal of non-standard neutrinos. one can derive an upper bound on the 7Be-neutrino flux. A measurement of the Berillium line intensity in excess Since the rate of fusion reactions (one half the rate of neutrino emission) is essentially fixed by solar energetics, in order to distinguish non-standard solar models from non-standard neutrinos. Next we investigate what can be leamt from future experiments aimed at the detection of the 7Be and pep lines, observing that all these ad-hoc models require huge variations of the parameters. Spp...). We will present a series of non-standard solar models which can account for the Gallex result. It is worth density...). Altematively, one can play on parameters which reduce the central temperature (opacity, age, of the He+He (3He+4He) cross section, without altering the inner solar structure (e.g. central temperature,
Physical Review D, 1995
Within the framework of the operator product expansion (OPE) and the renormalization group equati... more Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the zeroth moment of a spectral function (SF) is completely determined by the one-loop structure in an asymptotically free theory, and in particular in QCD. Logarithmic corrections are found to play an essential role in the derivation. This exact result constrains the shape of SF's, and implies striking effects near phase transitions. Phenomenological parameterizations of the SF, often used in applications such as the analysis of lattice QCD data or QCD sum rule calculations at finite temperature and baryon density must satisfy these constraints. We also explicitly illustrate in detail the exact sum rule in the Gross-Neveu model.
Physical Review D, 2003
We calculate the conversion rate of high-energy neutrinos propagating in constant magnetic field ... more We calculate the conversion rate of high-energy neutrinos propagating in constant magnetic field into an electron-W pair (ν → W + e) from the imaginary part of the neutrino self-energy. Using the exact propagators in constant magnetic field, the neutrino self-energy has been calculated to all orders in the field within the Weinberg-Salam model. We obtain a compact formula in the limit of B ≪ B cr ≡ m 2 /e. We find that above the process threshold E (th) ≈ 2.2•10 16 eV ×(B cr /B) this contribution to the absorption of neutrinos yields an asymptotic absorption length ≈ 1.1 m ×(B cr /B) 2 × (10 16 eV/E).
Nuclear Physics B, 1995
We introduce the running coupling constant of QCD in the high temperature phase,g 2 (T), through ... more We introduce the running coupling constant of QCD in the high temperature phase,g 2 (T), through a renormalization scheme where the dimensional reduction is optimal at the one-loop level. We then calculate the relevant scale parameter, Λ T , which characterizes the running ofg 2 (T) with T , using the background field method in the static sector. It is found that Λ T /Λ MS = e (γ E +1/22) /(4π) ≈ 0.148. We further verify that the couplingg 2 (T) is also optimal for lattice perturbative calculations. Our result naturally explains why the high temperature limit of QCD sets in at temperatures as low as a few times the critical temperature. In addition, our Λ T agrees remarkably well with the scale parameter determined from the lattice measurement of the spatial string tension of the SU(2) gauge theory at high T .
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Papers by marcello lissia