2,159 research outputs found
Effects of Mutual Transits by Extrasolar Planet-Companion Systems on Light Curves
We consider the effects of mutual transits by extrasolar planet-companion
systems (in a true binary or a planet-satellite system) on light curves. We
show that induced changes in light curves depend strongly on a ratio between a
planet-companion's orbital velocity around their host star and a
planet-companion's spin speed around their common center of mass. In both the
slow and fast spin cases (corresponding to long and short distances between
them, respectively), a certain asymmetry appears in light curves. We show that,
especially in the case of short distances, occultation of one faint object by
the other, while the transit of the planet-companion system occurs in front of
its parent star, causes an apparent increase in light curves and characteristic
fluctuations appear as important evidence of mutual transits. We show also that
extrasolar mutual transits provide a complementary method of measuring the
radii of two transiting objects, their separation and mass, and consequently
identifying them as a true binary, planet-satellite system or others.
Monitoring stars for three years with Kepler may lead to a discovery of
a second Earth-Moon-like system if the fraction of such systems for an averaged
star is larger than 0.05, or it may put upper limits on the fraction as f <
0.05.Comment: 15 pages, 6 figures, 1 table; text improved, typos corrected; PASJ in
pres
Characterization of foreign exchange market using the threshold-dealer-model
We introduce a deterministic dealer model which implements most of the
empirical laws, such as fat tails in the price change distributions, long term
memory of volatility and non-Poissonian intervals. We also clarify the
causality between microscopic dealers' dynamics and macroscopic market's
empirical laws.Comment: 10pages, 5figures, 1table, Proceedings of APFA
Successful reprogramming of epiblast stem cells by blocking nuclear localization of β-catenin.
Epiblast stem cells (EpiSCs) in mice and rats are primed pluripotent stem cells (PSCs). They barely contribute to chimeric embryos when injected into blastocysts. Reprogramming of EpiSCs to embryonic stem cell (ESC)-like cells (rESCs) may occur in response to LIF-STAT3 signaling; however, low reprogramming efficiency hampers potential use of rESCs in generating chimeras. Here, we describe dramatic improvement of conversion efficiency from primed to naive-like PSCs through upregulation of E-cadherin in the presence of the cytokine LIF. Analysis revealed that blocking nuclear localization of β-CATENIN with small-molecule inhibitors significantly enhances reprogramming efficiency of mouse EpiSCs. Although activation of Wnt/β-catenin signals has been thought desirable for maintenance of naive PSCs, this study provides the evidence that inhibition of nuclear translocation of β-CATENIN enhances conversion of mouse EpiSCs to naive-like PSCs (rESCs). This affords better understanding of gene regulatory circuits underlying pluripotency and reprogramming of PSCs
Conformally Schwarzschild cosmological black holes
We thoroughly investigate conformally Schwarzschild spacetimes in different
coordinate systems to seek for physically reasonable models of a cosmological
black hole. We assume that a conformal factor depends only on the time
coordinate and that the spacetime is asymptotically flat
Friedmann-Lema\^{\i}tre-Robertson-Walker universe filled by a perfect fluid
obeying a linear equation state with . In this class of
spacetimes, the McClure-Dyer spacetime, constructed in terms of the isotropic
coordinates, and the Thakurta spacetime, constructed in terms of the standard
Schwarzschild coordinates, are identical and do not describe a cosmological
black hole. In contrast, the Sultana-Dyer and Culetu classes of spacetimes,
constructed in terms of the Kerr-Schild and Painlev\'{e}-Gullstrand
coordinates, respectively, describe a cosmological black hole. In the
Sultana-Dyer case, the corresponding matter field in general relativity can be
interpreted as a combination of a homogeneous perfect fluid and an
inhomogeneous null fluid, which is valid everywhere in the spacetime unlike
Sultana and Dyer's interpretation. In the Culetu case, the matter field can be
interpreted as a combination of a homogeneous perfect fluid and an
inhomogeneous anisotropic fluid. However, in both cases, the total
energy-momentum tensor violates all the standard energy conditions at a finite
value of the radial coordinate in late times. As a consequence, the
Sultana-Dyer and Culetu black holes for cannot describe the
evolution of a primordial black hole after its horizon entry.Comment: 58 pages, 10 figures, 8 tables; v3, this version corrects the
published version according to the corrigendum (2023 Class. Quantum Grav. 40,
079501). The main results remain unchange
A note on the differences between European and international methodologies of banking regulation and supervision
Although monetary policy is the main tool for central banking in order to control inflation/deflation, micro- and macroprudential instruments are also essential for crisis management. In this paper, we aim to clarify the differences between European and international banking methodologies. The European approach as represented by the European Banking Union, is based on a harder legalistic approach, whereas the international approach implemented by the Basel Committee on Banking Supervision has a soft-law methodology. We propose two comparative standpoints: “uniformity” versus “diversity”, and a “legislative” versus "principle-based” approach
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