1,222 research outputs found
The Russian corporation: patterns of behavior during the crisis
This paper considers the behavior patterns of Russian firms before and during the financial crisis of 2008-2009. To facilitate comparison, we define three main
groups of actors at the firm level in the Russian economy – large, politically connected companies; mid-size firms that expanded in the 2000s with the help of administrative support, and successful mid-size firms driven by market factors.
Many of the large companies practiced highly risky financial policy and experienced a decrease in efficiency before the crisis, and the managers and owners of some Russian firms have been engaging in opportunistic behavior
during the crisis; the forms and causes of this behavior are analyzed here. We conclude by proposing some policy implications with emphasis on supporting successful mid-size firms driven by market factors
The Cooling Neutron Star in 3C 58
The upper limit of the effective surface temperature of the neutron star (NS)
PSR J0205+6449 in the supernova remnant 3C 58 obtained recently by Slane et al.
(2002) is analyzed using a modern theory of NS cooling (Kaminker et al. 2002).
The observational limit can be explained by cooling of a superfluid NS with the
core composed of neutrons, protons and electrons, where direct Urca process is
forbidden. However, combined with the data on the surface temperatures of other
isolated NSs, it gives evidence (emphasized by Slane et al.) that direct Urca
process is open in the inner cores of massive NSs. This evidence turns out to
be less stringent than the evidence provided by the well known observations of
Vela and Geminga.Comment: 3 pages, 2 figures, AA Letters (submitted
Neutrino Emission from Neutron Stars
We review the main neutrino emission mechanisms in neutron star crusts and
cores. Among them are the well-known reactions such as the electron-positron
annihilation, plasmon decay, neutrino bremsstrahlung of electrons colliding
with atomic nuclei in the crust, as well as the Urca processes and neutrino
bremsstrahlung in nucleon-nucleon collisions in the core. We emphasize recent
theoretical achievements, for instance, band structure effects in neutrino
emission due to scattering of electrons in Coulomb crystals of atomic nuclei.
We consider the standard composition of matter (neutrons, protons, electrons,
muons, hyperons) in the core, and also the case of exotic constituents such as
the pion or kaon condensates and quark matter. We discuss the reduction of the
neutrino emissivities by nucleon superfluidity, as well as the specific
neutrino emission produced by Cooper pairing of the superfluid particles. We
also analyze the effects of strong magnetic fields on some reactions, such as
the direct Urca process and the neutrino synchrotron emission of electrons. The
results are presented in the form convenient for practical use. We illustrate
the effects of various neutrino reactions on the cooling of neutron stars. In
particular, the neutrino emission in the crust is critical in setting the
initial thermal relaxation between the core and the crust. Finally, we discuss
the prospects of exploring the properties of supernuclear matter by confronting
cooling simulations with observations of the thermal radiation from isolated
neutron stars.Comment: review, 165 pages, Physics Reports, 2001 in pres
Neutron star cooling after deep crustal heating in the X-ray transient KS 1731-260
We simulate the cooling of the neutron star in the X-ray transient KS
1731-260 after the source returned to quiescence in 2001 from a long (>~ 12.5
yr) outburst state. We show that the cooling can be explained assuming that the
crust underwent deep heating during the outburst stage. In our best theoretical
scenario the neutron star has no enhanced neutrino emission in the core, and
its crust is thin, superfluid, and has the normal thermal conductivity. The
thermal afterburst crust-core relaxation in the star may be not over.Comment: 5 pages, 2 figures, accepted by MNRAS. In v.2, two references added
and typos correcte
Neutrino-pair bremsstrahlung by electrons in neutron star crusts
Neutrino-pair bremsstrahlung by relativistic degenerate electrons in a
neutron-star crust at densities (10^9 - 1.5x10^{14}) g/cm^3 is analyzed. The
processes taken into account are neutrino emission due to Coulomb scattering of
electrons by atomic nuclei in a Coulomb liquid, and electron-phonon scattering
and Bragg diffraction (the static-lattice contribution) in a Coulomb crystal.
The static-lattice contribution is calculated including the electron
band-structure effects for cubic Coulomb crystals of different types and also
for the liquid crystal phases composed of rod- and plate-like nuclei in the
neutron-star mantle (at 10^{14} - 1.5x10^{14} g/cm^3). The phonon contribution
is evaluated with proper treatment of the multi-phonon processes which removes
a jump in the neutrino bremsstrahlung emissivity at the melting point obtained
in previous works. Below 10^{13} g/cm^3, the results are rather insensitive to
the nuclear form factor, but results for the solid state near the melting point
are affected significantly by the Debye-Waller factor and multi-phonon
processes. At higher densities, the nuclear form factor becomes more
significant. A comparison of the various neutrino generation mechanisms in
neutron star crusts shows that electron bremsstrahlung is among the most
important ones.Comment: 17 pages, 13 figures, LaTeX using aa.cls and epsf.sty. A&A, in pres
Three Types of Cooling Superfluid Neutron Stars: Theory and Observations
Cooling of neutron stars (NSs) with the cores composed of neutrons, protons,
and electrons is simulated assuming S pairing of neutrons in the NS
crust, and also S pairing of protons and weak P pairing of
neutrons in the NS core, and using realistic density profiles of the superfluid
critical temperatures . The theoretical cooling models of
isolated middle-aged NSs can be divided into three main types. (I) {\it
Low-mass}, {\it slowly cooling} NSs where the direct Urca process of neutrino
emission is either forbidden or almost fully suppressed by the proton
superfluidity. (II) {\it Medium-mass} NSs which show {\it moderate} cooling via
the direct Urca process suppressed by the proton superfluidity. (III) {\it
Massive} NSs which show {\it fast} cooling via the direct Urca process weakly
suppressed by superfluidity. Confronting the theory with observations we treat
RX J0822--43, PSR 1055--52 and RX J1856--3754 as slowly cooling NSs. To explain
these sufficiently warm sources we need a density profile in
the crust with a rather high and flat maximum and sharp wings. We treat 1E
1207--52, RX J0002+62, PSR 0656+14, Vela, and Geminga as moderately cooling
NSs. We can determine their masses for a given model of proton superfluidity,
, and the equation of state in the NS core. No rapidly
cooling NS has been observed so far.Comment: 12 pages, 10 figures, Astron. Astrophys., submitte
- …