10,922 research outputs found

    Neutrino Emission from Superfluid Neutron-Star Cores: Various Types of Neutron Pairing

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    We calculate and provide analytic fits of the factors which describe the reduction of the neutrino emissivity of modified Urca and nucleon-nucleon bremsstrahlung processes by superfluidity of neutrons and protons in neutron-star cores. We consider 1^1S0_0 pairing of protons and either 1^1S0_0 or 3^3P2_2 pairing of neutrons. We analyze two types of 3^3P2_2 pairing: the familiar pairing with zero projection of the total angular momentum of neutron pairs onto quantization axis, mJ=0m_J=0; and the pairing with ‚ą£mJ‚ą£=2|m_J|=2 which leads to the gap with nodes at the neutron Fermi surface. Combining the new data with those available in the literature we fully describe neutrino emission by nucleons from neutron star cores to be used in simulations of cooling of superfluid neutron stars.Comment: 14 pages, 6 figures, A&A, accepte

    Direct Urca Process in a Neutron Star Mantle

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    We show that the direct Urca process of neutrino emission is allowed in two possible phases of nonspherical nuclei (inverse cylinders and inverse spheres) in the mantle of a neutron star near the crust-core interface. The process is open because neutrons and protons move in a periodic potential created by inhomogeneous nuclear structures. In this way the nucleons acquire large quasimomenta needed to satisfy momentum-conservation in the neutrino reaction. The appropriate neutrino emissivity in a nonsuperfluid matter is about 2--3 orders of magnitude higher than the emissivity of the modified Urca process in the stellar core. The process may noticeably accelerate the cooling of low-mass neutron stars.Comment: 7 pages, 3 figures, submitted to A&

    State-business relations and improvement of corporate governance in Russia

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    In this paper, we analyze the influence of the state on the improvement of corporate governance in Russia of the early 2000s. Taking into account the low quality of market institutions in the 1990s (i.e., the market failure phenomenon), we assume that state intervention as the ‚Äúsecond best‚ÄĚ institution had a positive impact in this case. Using a dataset of 822 joint-stock companies, we tested this hypothesis in two types of corporate models ‚Äď state-owned or mixed firms and ‚Äúpolitically connected‚ÄĚ firms. The first model confirmed a strong positive influence of state ownership on the corporate governance in Russia in 2001-2004. The estimation results of this model are statistically robust in different specifications. We connect this result with attempts of the Russian government to use standard mechanisms and procedures of corporate governance to defend its property rights in its relations with state-owned and mixed enterprises.corporate governance; market institutions; state-owned companies; Russia

    State-business relations in Russia in the 2000s: From the capture model to a variety of exchange models?

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    Using data from a 2009 survey of 957 manufacturing enterprises, this paper examines relations between the state and business as well as priority differences in the distribution of governmental support by federal, regional and local authorities. Regression analysis reveals that a ‚Äúmodel of exchange‚ÄĚ is the predominant pattern as opposed to ‚Äústate capture‚ÄĚ (in the case of big firms) or ‚Äúgrabbing hand‚ÄĚ (in the case of SMEs), both of which were typical of the 1990s. However, there are some differences in priorities at different levels of government. The federal government in 2007-2008 provided more support to state-owned and mixed enterprises providing stable employment, while regional authorities more often supported firms that were pursuing modernization. These trends could pave the way for a shift in governmental policy at the regional level from ‚ÄĚstate capture‚ÄĚ/‚ÄĚgrabbing hand‚ÄĚ to the Chinese-style ‚Äúhelping hand‚ÄĚ model.state capture; state-business relations; Russia
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