1,189 research outputs found

    Complements or substitutes? The effect of ETFs on other managed funds

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    We examine the complementary and substitute effects of exchange-traded funds (ETFs) and two other investment vehicles: mutual funds (MFs) and closed-end funds (CEFs). Focusing on the capital flow into investment vehicles, we find a complementary effect between ETFs and MFs, and substitution effect between ETFs and CEFs. The complementarity and substitution effect remains robust when focusing on subsamples with different market conditions and fund management styles. We present further evidence that past inflows of the same investment vehicle are significantly correlated with current inflows. These findings have implications to both investors and regulators in understanding the interdependence of investment vehicles.</p

    Mass-losing accretion discs around supermassive black holes

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    We study the effects of outflow/wind on the gravitational stability of accretion discs around supermassive black holes using a set of analytical steady-state solutions. Mass-loss rate by the outflow from the disc is assumed to be a power-law of the radial distance and the amount of the energy and the angular momentum which are carried away by the wind are parameterized phenomenologically. We show that the mass of the first clumps at the self-gravitating radius linearly decreases with the total mass-loss rate of the outflow. Except for the case of small viscosity and high accretion rate, generally, the self-gravitating radius increases as the amount of mass-loss by the outflow increases. Our solutions show that as more angular momentum is lost by the outflow, then reduction to the mass of the first clumps is more significant.Comment: Accepted for publication in Astrophysics & Space Scienc

    Multi-timescale Solar Cycles and the Possible Implications

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    Based on analysis of the annual averaged relative sunspot number (ASN) during 1700 -- 2009, 3 kinds of solar cycles are confirmed: the well-known 11-yr cycle (Schwabe cycle), 103-yr secular cycle (numbered as G1, G2, G3, and G4, respectively since 1700); and 51.5-yr Cycle. From similarities, an extrapolation of forthcoming solar cycles is made, and found that the solar cycle 24 will be a relative long and weak Schwabe cycle, which may reach to its apex around 2012-2014 in the vale between G3 and G4. Additionally, most Schwabe cycles are asymmetric with rapidly rising-phases and slowly decay-phases. The comparisons between ASN and the annual flare numbers with different GOES classes (C-class, M-class, X-class, and super-flare, here super-flare is defined as \geq X10.0) and the annal averaged radio flux at frequency of 2.84 GHz indicate that solar flares have a tendency: the more powerful of the flare, the later it takes place after the onset of the Schwabe cycle, and most powerful flares take place in the decay phase of Schwabe cycle. Some discussions on the origin of solar cycles are presented.Comment: 8 pages, 4 figure

    Trapped two-component Fermi gases with up to six particles: Energetics, structural properties, and molecular condensate fraction

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    We investigate small equal-mass two-component Fermi gases under external spherically symmetric confinement in which atoms with opposite spins interact through a short-range two-body model potential. We employ a non-perturbative microscopic framework, the stochastic variational approach, and determine the system properties as functions of the interspecies s-wave scattering length a, the orbital angular momentum L of the system, and the numbers N1 and N2 of spin-up and spin-down atoms (with N1-N2 =0 or 1 and N < 7, where N=N1+N2). At unitarity, we determine the energies of the five- and six-particle systems for various ranges r0 of the underlying two-body model potential and extrapolate to the zero-range limit. These energies serve as benchmark results that can be used to validate and assess other numerical approaches. We also present structural properties such as the pair distribution function and the radial density. Furthermore, we analyze the one-body and two-body density matrices. A measure for the molecular condensate fraction is proposed and applied. Our calculations show explicitly that the natural orbitals and the momentum distributions of atomic Fermi gases approach those characteristic for a molecular Bose gas if the s-wave scattering length a, a>0, is sufficiently small.Comment: 21 pages, 15 figures; accepted for publication in special issue of CRA
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