1,549 research outputs found
On the Possible Common Nature of Double Extensive Air Showers and Aligned Events
Double Extensive Air Showers and aligned events were discovered at energies E
{\gtsim} 1016 eV over fourth century back. But up to now there is no
sufficiently identical explanation of their nature. In this paper it is
expected that both types of events are the result of breakup of the string
formed in the collisions of super high energy particles
Heavy Ion Dynamics and Neutron Stars
Some considerations are reported, freely inspired from the presentations and
discussions during the Beijing Normal University Workshop on the above Subject,
held in July 2007. Of course this cannot be a complete summary but just a
collection of personal thougths aroused during the meeting.Comment: 11 pages, no figures, Summary Talk, Int.Workshop on "Nuclear Dynamics
in Heavy Ion Collisions and Neutron Stars", Beijing Normal Univ. July 07, to
appear in Int.Journ.Modern Physics E (2008
Thermonuclear Burning on the Accreting X-Ray Pulsar GRO J1744-28
We investigate the thermal stability of nuclear burning on the accreting
X-ray pulsar GRO J1744-28. The neutron star's dipolar magnetic field is
<3\times 10^{11} G if persistent spin-up implies that the magnetospheric radius
is less than the co-rotation radius. After inferring the properties of the
neutron star, we study the thermal stability of hydrogen/helium burning and
show that thermonuclear instabilities are unlikely causes of the hourly bursts
seen at very high accretion rates. We then discuss how the stability of the
thermonuclear burning depends on both the global accretion rate and the neutron
star's magnetic field strength. We emphasize that the appearance of the
instability (i.e., whether it looks like a Type I X-ray burst or a flare
lasting a few minutes) will yield crucial information on the neutron star's
surface magnetic field and the role of magnetic fields in convection. We
suggest that a thermal instability in the accretion disk is the origin of the
long (~300 days) outburst and that the recurrence time of these outbursts is
>50 years. We also discuss the nature of the binary and point out that a
velocity measurement of the stellar companion (most likely a Roche-lobe filling
giant with m_K>17) will constrain the neutron star mass.Comment: 19 pages, 3 PostScript figures, uses aaspp4.sty and epsfig.sty, to
appear in the Astrophysical Journa
Longitudinal and transversal spin dynamics of donor-bound electrons in fluorine-doped ZnSe: spin inertia versus Hanle effect
The spin dynamics of the strongly localized, donor-bound electrons in
fluorine-doped ZnSe epilayers is studied by pump-probe Kerr rotation
techniques. A method exploiting the spin inertia is developed and used to
measure the longitudinal spin relaxation time, , in a wide range of
magnetic fields, temperatures, and pump densities. The time of the
donor-bound electron spin of about 1.6 s remains nearly constant for
external magnetic fields varied from zero up to 2.5 T (Faraday geometry) and in
a temperature range K. The inhomogeneous spin dephasing time,
ns, is measured using the resonant spin amplification and Hanle
effects under pulsed and steady-state pumping, respectively. These findings
impose severe restrictions on possible spin relaxation mechanisms.Comment: 10 pages, 7 figure
The direct evaluation of attosecond chirp from a streaking measurement
We derive an analytical expression, from classical electron trajectories in a
laser field, that relates the breadth of a streaked photoelectron spectrum to
the group-delay dispersion of an isolated attosecond pulse. Based on this
analytical expression, we introduce a simple, efficient and robust procedure to
instantly extract the attosecond pulse's chirp from the streaking measurement.Comment: 4 figure
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