2,359 research outputs found
Statistical theory of thermal evolution of neutron stars
Thermal evolution of neutron stars is known to depend on the properties of
superdense matter in neutron star cores. We suggest a statistical analysis of
isolated cooling middle-aged neutron stars and old transiently accreting
quasi-stationary neutron stars warmed up by deep crustal heating in low-mass
X-ray binaries. The method is based on simulations of the evolution of stars of
different masses and on averaging the results over respective mass
distributions. This gives theoretical distributions of isolated neutron stars
in the surface temperature--age plane and of accreting stars in the photon
thermal luminosity--mean mass accretion rate plane to be compared with
observations. This approach permits to explore not only superdense matter but
also the mass distributions of isolated and accreting neutron stars. We show
that the observations of these stars can be reasonably well explained by
assuming the presence of the powerful direct Urca process of neutrino emission
in the inner cores of massive stars, introducing a slight broadening of the
direct Urca threshold (for instance, by proton superfluidity), and by tuning
mass distributions of isolated and accreted neutron stars.Comment: 13 pages, 20 figure
Quantum Interference Controls the Electron Spin Dynamics in n-GaAs
Manifestations of quantum interference effects in macroscopic objects are
rare. Weak localization is one of the few examples of such effects showing up
in the electron transport through solid state. Here we show that weak
localization becomes prominent also in optical spectroscopy via detection of
the electron spin dynamics. In particular, we find that weak localization
controls the free electron spin relaxation in semiconductors at low
temperatures and weak magnetic fields by slowing it down by almost a factor of
two in -doped GaAs in the metallic phase. The weak localization effect on
the spin relaxation is suppressed by moderate magnetic fields of about 1 T,
which destroy the interference of electron trajectories, and by increasing the
temperature. The weak localization suppression causes an anomalous decrease of
the longitudinal electron spin relaxation time with magnetic field, in
stark contrast with well-known magnetic field induced increase in . This
is consistent with transport measurements which show the same variation of
resistivity with magnetic field. Our discovery opens a vast playground to
explore quantum magneto-transport effects optically in the spin dynamics.Comment: 8 pages, 3 figure
Production of high energy particles in laser and Coulomb fields and e^+e^- antenna
A strong laser field and the Coulomb field of a nucleus can produce
e^{+}e^{-} pairs. It is shown for the first time that there is a large
probability that electrons and positrons created in this process collide after
one or several oscillations of the laser field. These collisions can take place
at high energy resulting in several phenomena. The quasielastic collision
e^{+}e^{-} -> e^{+}e^{-} allows acceleration of leptons in the laser field to
higher energies. The inelastic collisions allow production of high energy
photons e^{+}e^{-}-> 2 gamma and muons, e^{+}e^{-} -> mu^{+}mu^{-}. The yield
of high-energy photons and muons produced via this mechanism exceeds
exponentially their production through conventional direct creation in laser
and Coulomb fields. A relation of the phenomena considered with the
antenna-mechanism of multiphoton absorption in atoms is discussed.Comment: 4 page
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
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