1,866 research outputs found
Effective theory of Black Holes in the 1/D expansion
The gravitational field of a black hole is strongly localized near its
horizon when the number of dimensions D is very large. In this limit, we can
effectively replace the black hole with a surface in a background geometry (eg
Minkowski or Anti-deSitter space). The Einstein equations determine the
effective equations that this 'black hole surface' (or membrane) must satisfy.
We obtain them up to next-to-leading order in 1/D for static black holes of the
Einstein-(A)dS theory. To leading order, and also to next order in Minkowski
backgrounds, the equations of the effective theory are the same as soap-film
equations, possibly up to a redshift factor. In particular, the Schwarzschild
black hole is recovered as a spherical soap bubble. Less trivially, we find
solutions for 'black droplets', ie black holes localized at the boundary of
AdS, and for non-uniform black strings.Comment: 32 pages, 3 figure
Structure of the Milky Way stellar halo out to its outer boundary with blue horizontal-branch stars
We present the structure of the Milky Way stellar halo beyond Galactocentric
distances of kpc traced by blue horizontal-branch (BHB) stars, which
are extracted from the survey data in the Hyper Suprime-Cam Subaru Strategic
Program (HSC-SSP). We select BHB candidates based on photometry,
where the -band is on the Paschen series and the colors that involve the
-band are sensitive to surface gravity. About 450 BHB candidates are
identified between kpc and 300 kpc, most of which are beyond the reach
of previous large surveys including the Sloan Digital Sky Survey. We find that
the global structure of the stellar halo in this range has substructures, which
are especially remarkable in the GAMA15H and XMM-LSS fields in the HSC-SSP. We
find that the stellar halo can be fitted to a single power-law density profile
with an index of () with (without) these fields and
its global axial ratio is (). Thus, the stellar halo may be
significantly disturbed and be made in a prolate form by halo substructures,
perhaps associated with the Sagittarius stream in its extension beyond kpc. For a broken power-law model allowing different power-law indices
inside/outside a break radius, we obtain a steep power-law slope of outside a break radius of kpc ( kpc) for the case
with (without) GAMA15H and XMM-LSS. This radius of kpc might be as close
as a halo boundary if there is any, although larger BHB sample is required from
further HSC-SSP survey to increase its statistical significance.Comment: 12 pages, 8 figures, revised version, accepted for publication in
PAS
A cross-licensing system discourages R&D investments in completely complementary technologies.
We consider the R&D investments competition of the duopolistic firms in completely complementarty technologies. By "completely complementary technologies" ,we mea that each firm cannot produce the goods without both of the technologies. We derive the investments competiton equilibria in R&D of the two completely complementary technologies with and without the cross-licensing system. By comparing the R&D incestment levels in the two equilibria, we show that the crosslicensing system discourages the R&D investments when the duopolistic firms produce goods by using the two completely complementary technologies
Licensing (cross-licensing) system and R&D investments in a weakly complementary technologies economy
We consider the R&D investments competition of the two duopolistic firms in a weakly complementary technologies economy. By “the weakly complementary technologies”, we mean that each firm can produce goods without both of the two technologies but it incurs more redundant costs than that in the case each or both of the technologies may be available for it. By “the strongly complementary technologies,” we mean that the firm cannot produce the goods at all without the use of both of them. We derive the investments competition equilibria in R&D of the two weakly complementary technologies with and without the (cross-) licensing system. By comparing of the R&D investment levels in the two equilibria, we show that the (cross-) licensing system promotes the R&D investments when the duopolistic firms can produce goods by using of the two weakly complementary technologies
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