10,448 research outputs found
Field-dependent quantum nucleation of antiferromagnetic bubbles
The phenomenon of quantum nucleation is studied in a nanometer-scale
antiferromagnet with biaxial symmetry in the presence of a magnetic field at an
arbitrary angle. Within the instanton approach, we calculate the dependence of
the rate of quantum nucleation and the crossover temperature on the orientation
and strength of the field for bulk solids and two-dimensional films of
antiferromagnets, respectively. Our results show that the rate of quantum
nucleation and the crossover temperature from thermal-to-quantum transitions
depend on the orientation and strength of the field distinctly, which can be
tested with the use of existing experimental techniques.Comment: 21 pages, 5 figures, Final version and accepted by Eur. Phys. J
Towards High-Fidelity 3D Face Reconstruction from In-the-Wild Images Using Graph Convolutional Networks
3D Morphable Model (3DMM) based methods have achieved great success in
recovering 3D face shapes from single-view images. However, the facial textures
recovered by such methods lack the fidelity as exhibited in the input images.
Recent work demonstrates high-quality facial texture recovering with generative
networks trained from a large-scale database of high-resolution UV maps of face
textures, which is hard to prepare and not publicly available. In this paper,
we introduce a method to reconstruct 3D facial shapes with high-fidelity
textures from single-view images in-the-wild, without the need to capture a
large-scale face texture database. The main idea is to refine the initial
texture generated by a 3DMM based method with facial details from the input
image. To this end, we propose to use graph convolutional networks to
reconstruct the detailed colors for the mesh vertices instead of reconstructing
the UV map. Experiments show that our method can generate high-quality results
and outperforms state-of-the-art methods in both qualitative and quantitative
comparisons.Comment: Accepted to CVPR 2020. The source code is available at
https://github.com/FuxiCV/3D-Face-GCN
Post-Oligarchic Evolution of Protoplanetary Embryos and the Stability of Planetary Systems
We investigate the orbit-crossing time (T_c) of protoplanet systems both with
and without a gas-disk background. The protoplanets are initially with equal
masses and separation (EMS systems) scaled by their mutual Hill's radii. In a
gas-free environment, we find log (T_c/yr) = A+B \log (k_0/2.3). Through a
simple analytical approach, we demonstrate that the evolution of the velocity
dispersion in an EMS system follows a random walk. The stochastic nature of
random-walk diffusion leads to (i) an increasing average eccentricity ~
t^1/2, where t is the time; (ii) Rayleigh-distributed eccentricities
(P(e,t)=e/\sigma^2 \exp(-e^2/(2\sigma^2)) of the protoplanets; (iii) a
power-law dependence of T_c on planetary separation. As evidence for the
chaotic diffusion, the observed eccentricities of known extra solar planets can
be approximated by a Rayleigh distribution. We evaluate the isolation masses of
the embryos, which determine the probability of gas giant formation, as a
function of the dust and gas surface densities.Comment: 15 pages, 13 figures (2 color ones), accepted for publication in Ap
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