8,728 research outputs found
Discovery of Crystallized Water Ice in a Silhouette Disk in the M43 Region
We present the 1.9--4.2um spectra of the five bright (L<11.2) young stars
associated with silhouette disks with moderate to high inclination angle of
39--80deg in the M42 and M43 regions. The water ice absorption is seen toward
d121-1925 and d216-0939, while the spectra of d182-316, d183-405, and d218-354
show no water ice feature around 3.1um within the detection limits. By
comparing the water ice features toward nearby stars, we find that the water
ice absorption toward d121-1925 and d216-0939 most likely originates from the
foreground material and the surrounding disk, respectively. The angle of the
disk inclination is found to be mainly responsible for the difference of the
optical depth of the water ice among the five young stars. Our results suggest
that there is a critical inclination angle between 65deg and 75deg for the
circumstellar disk where the water ice absorption becomes strong. The average
density at the disk surface of d216-0939 was found to be 6.38x10^(-18) g
cm^(-3). The water ice absorption band in the d216-0939 disk is remarkable in
that the maximum optical depth of the water ice band is at a longer wavelength
than detected before. It indicates that the primary carrier of the feature is
purely crystallized water ice at the surface of the d216-0939 disk with
characteristic size of ~0.8um, which suggests grain growth. This is the first
direct detection of purely crystallized water ice in a silhouette disk.Comment: 28 pages, 8 figures, Accepted by Ap
Fermi Surface Reconstruction without Breakdown of Kondo Screening at Quantum Critical Point
Motivated by recent Hall-effect experiment in YbRhSi, we study ground
state properties of a Kondo lattice model in a two-dimensional square lattice
using variational Monte Carlo method. We show that there are two types of phase
transition, antiferromagnetic transition and topological one (Fermi surface
reconstruction). In a wide region of parameters, these two transitions occur
simultaneously without the breakdown of Kondo screening, accompanied by a
discontinuous change of the Hall coefficient. This result is consistent with
the experiment and gives a novel theoretical picture for the quantum critical
point in heavy fermion systems.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
Continuum Coupling and Pair Correlation in Weakly Bound Deformed Nuclei
We formulate a new Hartree-Fock-Bogoliubov method applicable to weakly bound
deformed nuclei using the coordinate-space Green's function technique. An
emphasis is put on treatment of quasiparticle states in the continuum, on which
we impose the correct boundary condition of the asymptotic out-going wave. We
illustrate this method with numerical examples.Comment: 5 pages, 4 figures, Proceedings of the Japanese French Symposium -
New paradigms in Nuclear Physics, Paris, 29th September - 2nd October, to be
published in Int. J. of Modern Physics
"Indirect Network Effects and the Product Cycle: Video Games in the U.S., 1994-2002"
This paper examines the importance of indirect network effects in the U.S.video game market between 1994 and 2002. The diffusion of game systems is analyzed by the interaction between console adoption decisions and software supply decisions. Estimation results suggest that introductory pricing is an effective practice at the beginning of the product cycle, and expanding software variety becomes more effective later. The paper also finds a degree of inertia in the software market that does not exist in the hardware market. This observation implies that software providers continue to exploit the installed base of hardware users after hardware demand has slowed.
More on the Isomorphism
In this paper we revisit the isomorphism to
apply to some subjects in Quantum Computation and Mathematical Physics.
The unitary matrix by Makhlin giving the isomorphism as an adjoint action
is studied and generalized from a different point of view. Some problems are
also presented.
In particular, the homogeneous manifold which characterizes
entanglements in the case of is studied, and a clear-cut calculation of
the universal Yang-Mills action in (hep-th/0602204) is given for the abelian
case.Comment: Latex ; 19 pages ; 5 figures ; minor changes. To appear in
International Journal of Geometric Methods in Modern Physics (vol.4, no.3
Onsager-Machlup action-based path sampling and its combination with replica exchange for diffusive and multiple pathways
For sampling multiple pathways in a rugged energy landscape, we propose a
novel action-based path sampling method using the Onsager-Machlup action
functional. Inspired by the Fourier-path integral simulation of a quantum
mechanical system, a path in Cartesian space is transformed into that in
Fourier space, and an overdamped Langevin equation is derived for the Fourier
components to achieve a canonical ensemble of the path at a finite temperature.
To avoid "path trapping" around an initially guessed path, the path sampling
method is further combined with a powerful sampling technique, the replica
exchange method. The principle and algorithm of our method is numerically
demonstrated for a model two-dimensional system with a bifurcated potential
landscape. The results are compared with those of conventional transition path
sampling and the equilibrium theory, and the error due to path discretization
is also discussed.Comment: 20 pages, 5 figures, submitted to J. Chem. Phy
- …