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51.
52.
Philippe?JetzerEmail author Denis?Puy Monique?Signore Crescenzo?Tortora 《General Relativity and Gravitation》2011,43(4):1083-1093
The nature of the dark energy is still a mystery and several models have been proposed to explain it. Here we consider a phenomenological
model for dark energy decay into photons and particles as proposed by Lima (Phys Rev D 54:2571, 1996). He studied the thermodynamic
aspects of decaying dark energy models in particular in the case of a continuous photon creation and/or disruption. Following
his approach, we derive a temperature redshift relation for the cosmic microwave background (CMB) which depends on the effective
equation of state w
eff and on the “adiabatic index” γ. Comparing our relation with the data on the CMB temperature as a function of the redshift obtained from Sunyaev–Zel’dovich
observations and at higher redshift from quasar absorption line spectra, we find w
eff = −0.97 ± 0.03, adopting for the adiabatic index γ = 4/3, in good agreement with current estimates and still compatible with w
eff = −1, implying that the dark energy content being constant in time. 相似文献
53.
Antonio Tortora 《代数通讯》2013,41(2):431-438
For any integer n ≠ 0,1, a group G is said to be “n-Bell” if it satisfies the identity [x n ,y] = [x,y n ]. It is known that if G is an n-Bell group, then the factor group G/Z 2(G) has finite exponent dividing 12n 5(n ? 1)5. In this article we show that this bound can be improved. Moreover, we prove that every n-Bell group is n-nilpotent; consequently, using results of Baer on finite n-nilpotent groups, we give the structure of locally finite n-Bell groups. Finally, we are concerned with locally graded n-Bell groups for special values of n. 相似文献
54.
Giuseppe Belletti Carola Tortora Indradevi D. Mellema Dr. Paul Tinnemans Dr. Hugo Meekes Prof. Dr. Floris P. J. T. Rutjes Prof. Dr. Svetlana B. Tsogoeva Prof. Dr. Elias Vlieg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):839-844
Viedma ripening is a deracemization process that has been used to deracemize a range of chiral molecules. The method has two major requirements: the compound needs to crystallize as a conglomerate and it needs to be racemizable under the crystallization conditions. Although conglomerate formation can be induced in different ways, the number of racemization methods is still rather limited. To extend the scope of Viedma ripening, in the present research we applied UV-light-induced racemization in a Viedma ripening process, and report the successful deracemization of a BINOL derivative crystallizing as a conglomerate. Irradiation by UV light activates the target compound in combination with an organic base, required to promote the excited-state proton transfer (ESPT), leading thereafter to racemization. This offers a new tool towards the development of Viedma ripening processes, by using a cheap and “green” catalytic source like UV light to racemize suitable chiral compounds. 相似文献
55.
Mariarosaria Rizzardi 《Numerical Algorithms》2018,77(4):955-982
For several applications, it is important to know the location of the singularities of a complex function: just for example, the rightmost singularity of a Laplace Transform is related to the exponential order of its inverse function. We discuss a numerical method to approximate, within an input accuracy tolerance, a finite sequence of Laurent coefficients of a function by means of the Discrete Fourier Transform (DFT) of its samples along an input circle. The circle may also enclose some singularities, since the method works with the Laurent expansion. The DFT is computed by the FFT algorithm so that, from a computational point of view, the efficiency is guaranteed. The function samples may be obtained by solving a numerical problem such as, for example, a differential problem. We derive, as consequences of the method, some new outcomes able to detect those singularities which are close to the circle and to discover if the singularities are all external or internal to the circle so that the Laurent expansion reduces to its regular or singular part, respectively. Other singularities may be located by means of a repeated application of the method, as well as an analytic continuation. Some examples and results, obtained by a first implementation, are reported. 相似文献
56.
D. Fong M. Heller A.M. Shapiro M. Widgoff F. Bruyant D. Bogert M. Johnson R. Burnstein C. Fu D. Petersen M. Robertson H. Rubin R. Sard A. Snyder J. Tortora D. Alyea C.-Y. Chien P. Lucas H.D. Taft 《Physics letters. [Part B]》1975,60(1):124-128
We present data on inclusive and semi-inclusive ?0 production in 147 GeV/c π?p interactions. We find a total cross section of 7.3 ± 1.3 mb. Most of this cross section is found in the lower topology events (? 10 prongs), and in the central and forward rapidity regions. The PT2 dependence of ?0 production, 〈:n>?0 per event, and the ?0/π+ ratios are also discussed. 相似文献
57.
D. Fong M. Heller A. Shapiro M. Widgoff F. Bruyant D. Bogert M. Johnson R. Burnstein C. Fu D. Petersen M. Robertson H. Rubin R. Sard A. Snyder J. Tortora D. Alyea C.-Y. Chien P. Lucas T. Watts 《Nuclear Physics B》1976,104(1):32-51
An SU(3) gauge-field non-topological soliton in three space-dimensions is discussed. Let N be the largest among the magnitudes of eigenvalues of the matrix Σ18λaQa, where the Qa's are the eight conserved charges in the classical SU(3) gauge theory, and the λa's the usual 3 × 3 Gell-Mann matrices. We show that stable solitons exist if N > a critical value NS, and if the ratio between the mass of the SU(3) gauge field and that of a relevant spin-0 field is >√6. Our trial function analysis suggests that, for large N, states with dets (Σ18λaQa) ≠ 0 are unstable against fission. 相似文献
58.
59.
F. Ambrosino A. Antonelli M. Antonelli F. Archilli P. Beltrame G. Bencivenni C. Bini C. Bloise S. Bocchetta F. Bossi P. Branchini G. Capon D. Capriotti T. Capussela F. Ceradini P. Ciambrone E. De Lucia A. De Santis P. De Simone G. De Zorzi A. Denig A. Di Domenico C. Di Donato B. Di Micco M. Dreucci G. Felici S. Fiore P. Franzini C. Gatti P. Gauzzi S. Giovannella E. Graziani M. Jacewicz V. Kulikov G. Lanfranchi J. Lee-Franzini M. Martini P. Massarotti S. Meola S. Miscetti M. Moulson S. Müller F. Murtas M. Napolitano F. Nguyen M. Palutan A. Passeri V. Patera P. Santangelo B. Sciascia A. Sibidanov T. Spadaro L. Tortora P. Valente G. Venanzoni R. Versaci 《The European Physical Journal C - Particles and Fields》2009,64(4):627-636
We present a precise measurement of the ratio R K =Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and a study of the radiative process K→e ν γ, performed with the KLOE detector. The results are based on data collected at the Frascati e + e ? collider DAΦNE for an integrated luminosity of 2.2 fb?1. We find R K =(2.493±0.025stat±0.019syst)×10?5, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate dΓ(K→e ν γ)/dE γ for photon energies 10<E γ < 250 MeV. Results are compared with predictions from theory. 相似文献
60.
Pino Sabia Marco Lubrano Lavadera Giancarlo Sorrentino Paola Giudicianni Raffaele Ragucci Mariarosaria de Joannon 《Flow, Turbulence and Combustion》2016,96(2):433-448
MILD combustion is a very attractive technology because of its intrinsic features for energy production from diluted gas deriving from bio- or thermochemical degradation of biomass. An effective use of such a technology for diluted fuel requires a thorough analysis of ignition and oxidation behavior to highlight the potential effects of the different fuel components on the basis of temperature and diluent/oxygen/fuel mixture composition. In this work, ignition and oxidation of a model gas surrogate for the gaseous fraction of biomass pyrolysis products containing C1-C2 species, CO and CO2 were experimentally and numerically studied over a wide range of temperature and overall composition in the presence of large amounts of CO2 or H2O. Experimental results showed that such species significantly alter the evolution of the ignition process in dependence on temperature range and mixture composition. Several kinetic models were tested to simulate experimental results. Significant discrepancies occur, especially in the case of steam dilution. Numerical analyses suggested that such diluents acted mainly as third body species at low temperatures, conditioning both radical production pathways and the relative weight of C1 oxidation/recombination routes, while strongly interacting with the H2/O2 high temperature branching mechanisms at high temperatures. Further analyses are mandatory to improve the predictability of the models and extend the applicability of the chemical schemes to non-standard conditions. 相似文献