23,147 research outputs found
A study of the high-inclination population in the Kuiper belt - II. The Twotinos
As the second part of our study, in this paper we proceed to explore the
dynamics of the high-inclination Twotinos in the 1:2 Neptune mean motion
resonance (NMMR). Depending on the inclination , we show the existence of
two critical eccentricities and , which are lower limits of
the eccentricity for the resonant angle to exhibit libration and
asymmetric libration, respectively. Accordingly, we have determined the
libration centres for inclined orbits, which are strongly dependent
on . With initial on a fine grid of , the
stability of orbits in the 1:2 NMMR is probed by 4-Gyr integrations. It is
shown that symmetric librators are totally unstable for ; while
stable asymmetric librators exist for up to .
We further investigate the 1:2 NMMR capture and retention of planetesimals
with initial inclinations in the planet migration model
using a time-scale of yr. We find that: (1) the capture
efficiency of the 1:2 NMMR decreases drastically with the increase of ,
and it goes to 0 when ; (2) the probability of discovering
Twotinos with , beyond observed values, is roughly estimated to
be per cent; (3) more particles are captured into the leading rather
than the trailing asymmetric resonance for , but this number
difference appears to be the opposite at and is continuously
varying for even larger ; (4) captured Twotinos residing in the trailing
resonance or having are practically outside the Kozai mechanism,
like currently observed samples.Comment: 13 pages, 10 figures, Accepted by MNRAS. Comments welcome
DAP3D-Net: Where, What and How Actions Occur in Videos?
Action parsing in videos with complex scenes is an interesting but
challenging task in computer vision. In this paper, we propose a generic 3D
convolutional neural network in a multi-task learning manner for effective Deep
Action Parsing (DAP3D-Net) in videos. Particularly, in the training phase,
action localization, classification and attributes learning can be jointly
optimized on our appearancemotion data via DAP3D-Net. For an upcoming test
video, we can describe each individual action in the video simultaneously as:
Where the action occurs, What the action is and How the action is performed. To
well demonstrate the effectiveness of the proposed DAP3D-Net, we also
contribute a new Numerous-category Aligned Synthetic Action dataset, i.e.,
NASA, which consists of 200; 000 action clips of more than 300 categories and
with 33 pre-defined action attributes in two hierarchical levels (i.e.,
low-level attributes of basic body part movements and high-level attributes
related to action motion). We learn DAP3D-Net using the NASA dataset and then
evaluate it on our collected Human Action Understanding (HAU) dataset.
Experimental results show that our approach can accurately localize, categorize
and describe multiple actions in realistic videos
A unified variance-reduced accelerated gradient method for convex optimization
We propose a novel randomized incremental gradient algorithm, namely,
VAriance-Reduced Accelerated Gradient (Varag), for finite-sum optimization.
Equipped with a unified step-size policy that adjusts itself to the value of
the condition number, Varag exhibits the unified optimal rates of convergence
for solving smooth convex finite-sum problems directly regardless of their
strong convexity. Moreover, Varag is the first accelerated randomized
incremental gradient method that benefits from the strong convexity of the
data-fidelity term to achieve the optimal linear convergence. It also
establishes an optimal linear rate of convergence for solving a wide class of
problems only satisfying a certain error bound condition rather than strong
convexity. Varag can also be extended to solve stochastic finite-sum problems.Comment: 33rd Conference on Neural Information Processing Systems (NeurIPS
2019
Dynamical spacetimes in conformal gravity
The conformal gravity remarkably boosts our prehension of gravity theories.
We find a series of dynamical solutions in the -conformal gravity,
including generalized Schwarzschild-Friedmann-Robertson-Walker (GSFRW), charged
generalized Schwarzschild-Friedmann-Robertson-Walker (CGSFRW), especially
rotating Friedmann-Robertson-Walker (RFRW), charged rotating
Friedmann-Robertson-Walker (CRFRW), and a dynamical cylindrically symmetric
solutions. The RFRW, CRFRW and the dynamical cylindrically symmetric solutions
are never found in the Einstein gravity and modified gravities. The GSFRW and
CGSFRW solutions take different forms from the corresponding solutions in the
Einstein gravity.Comment: 13 pages, no fi
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