arXiv subjects

D. Fargion

Publications and source records attributed to D. Fargion.

94 records · Page 6Linked to original sources

arXiv1996

Inverse Compton Scattering onto BBR in High Energy Physics and Gamma (MeV-Tev) Astrophysics

We considered the Inverse Compton Scattering (ICS) of charged particles onto photons whose distribution is a Black Body Radiation (BBR) deriving the exact energy and angular differential distribution in the general case and in its most useful expansions. These results can be successfully applied in high energy accelerators experiments to evaluate the ICS contribution from the thermal photons in the cavity as well as in astrophysics where the ICS of cosmic rays plays a relevant role in a variety of phenomena. In particular we show how our formulae reproduce the ICS energy spectrum recently measured at LEP, how it could be considered a key tool in explaining the Gamma Ray Bursts (GRB) , SGRs energy spectrum. Finally we predicted the presence of a low gamma flux, nearly detectable at hundred of TeV from SNRs SN1006 as well as, at lower energy (tens TeV, due to gamma ray cascading in cosmic BBR), from relic extragalactic highest cosmic rays sources born by jets in AGN,as blazars 3C279,Mrk421,Mrk 501.

astro-ph↗

arXiv1996

Gravitational Instability for a Multifluid Medium in an Expanding Universe

We consider the gravitational clustering of a multicomponent fluid in an expanding Newtonian universe, taking into account the mutual gravitational interactions of the medium. We obtain a set of exact and approximate solutions for two fluid components and for several fluid components: primordial hydrogen and helium or cosmological massive neutrinos of different mass and/or velocity distribution may be described by these solutions. The ratio between the two fluid perturbations, even if originally equal to unity, changes monotonically with time; this phenomenon leads to different epochs for nonlinear clustering that may be reflected into different epochs of galaxy formation. Additional note: see also D. Fargion (Nuovo Cimento 65,1981,316), L.V. Solov'eva & I.S. Nurgaliev (Sov. Astron. 29(3),1985,267-272), L.V. Solov'eva & A.A. Starobinskiy (Sov. Astron. 29(4),1985,367-371), I.S. Nurgaliev (Sov. Astron. Lett. 12(2),1986,73-76) and compare with astro-ph/9605133.

astro-ph↗

arXiv1996

Prompt And Delayed Radio Bangs At Kilohertz By SN 1987A: A Test For Graviton-Photon Conversion

A sequence of prompt and delayed radio signals at tens of kilohertz should reach the Earth (or Jupiter) due to graviton--photon conversion in interstellar as well as local planetary magnetic fields. These radio fluxes may be a detectable probe of a huge gravitational burst expected from Supernovae explosions. The earliest prompt radio signal, coinciding with the neutrino burst, is due to conversion in the terrestrial (or Jovian) magnetic field and is below the micro-Jansky (or milli-Jansky) level for a galactic Supernova like SN1987A. A later radio signal, a ``tail'', due to the same graviton - radio wave conversion in random interstellar fields will maintain a relic radio ``noise'' for hundreds or thousands of years and might even be still detectable by a very sensitive network of satellite antennas at the kilohertz band. Exact solutions are presented here for the graviton-photon conversion in a refractive medium, as well as their consequences for high energy supernovae and the 2.726 K background radiation.

astro-ph↗

arXiv1996

Gravitational Shapiro phase shift on pulsars' period to detect Dark Matter

The Shapiro Phase Shift on Pulsars (SPSP) influence at low , but detectable level the pulsars' (PSR) periods and their derivatives. This effect may be already written in PSRs' time derivative deviation and in particular it may explain the presence of a few negative pulse derivatives among 558 known PSRs. We describe in detail the phenomenon and predict that the SPSP may play a role in period derivative deviations for just a few PSRs a year ( 0.5 - 5 ev / yr) at a positive period derivative 10^-14 - 10^-15 s/s level , leading to a plausible explanation to the puzzling negative pulse derivative of few PSRs' periods.

astro-ph↗