49,163 research outputs found
Control Regularization for Reduced Variance Reinforcement Learning
Dealing with high variance is a significant challenge in model-free
reinforcement learning (RL). Existing methods are unreliable, exhibiting high
variance in performance from run to run using different initializations/seeds.
Focusing on problems arising in continuous control, we propose a functional
regularization approach to augmenting model-free RL. In particular, we
regularize the behavior of the deep policy to be similar to a policy prior,
i.e., we regularize in function space. We show that functional regularization
yields a bias-variance trade-off, and propose an adaptive tuning strategy to
optimize this trade-off. When the policy prior has control-theoretic stability
guarantees, we further show that this regularization approximately preserves
those stability guarantees throughout learning. We validate our approach
empirically on a range of settings, and demonstrate significantly reduced
variance, guaranteed dynamic stability, and more efficient learning than deep
RL alone.Comment: Appearing in ICML 201
Superquadrics for segmentation and modeling range data
We present a novel approach to reliable and efficient recovery of part-descriptions in terms of superquadric models from range data. We show that superquadrics can directly be recovered from unsegmented data, thus avoiding any presegmentation steps (e.g., in terms of surfaces). The approach is based on the recover-andselect paradigm. We present several experiments on real and synthetic range images, where we demonstrate the stability of the results with respect to viewpoint and noise
Coalescence Rate of Supermassive Black Hole Binaries Derived from Cosmological Simulations: Detection Rates for LISA and ET
The coalescence history of massive black holes has been derived from
cosmological simulations, in which the evolution of those objects and that of
the host galaxies are followed in a consistent way. The present study indicates
that supermassive black holes having masses greater than underwent up to 500 merger events along their history. The derived
coalescence rate per comoving volume and per mass interval permitted to obtain
an estimate of the expected detection rate distribution of gravitational wave
signals ("ring-down") along frequencies accessible by the planned
interferometers either in space (LISA) or in the ground (Einstein). For LISA,
in its original configuration, a total detection rate of about is
predicted for events having a signal-to-noise ratio equal to 10, expected to
occur mainly in the frequency range . For the Einstein gravitational
wave telescope, one event each 14 months down to one event each 4 years is
expected with a signal-to-noise ratio of 5, occurring mainly in the frequency
interval . The detection of these gravitational signals and their
distribution in frequency would be in the future an important tool able to
discriminate among different scenarios explaining the origin of supermassive
black holes.Comment: 18 pages, 7 figures, to appear in the IJMP
Jets in Hadron-Hadron Collisions
In this article, we review some of the complexities of jet algorithms and of
the resultant comparisons of data to theory. We review the extensive experience
with jet measurements at the Tevatron, the extrapolation of this acquired
wisdom to the LHC and the differences between the Tevatron and LHC
environments. We also describe a framework (SpartyJet) for the convenient
comparison of results using different jet algorithms.Comment: 68 pages, 54 figure
N-Body Simulation of Planetesimal Formation through Gravitational Instability of a Dust Layer in Laminar Gas Disk
We investigate the formation process of planetesimals from the dust layer by
the gravitational instability in the gas disk using local -body simulations.
The gas is modeled as a background laminar flow. We study the formation process
of planetesimals and its dependence on the strength of the gas drag. Our
simulation results show that the formation process is divided into three stages
qualitatively: the formation of wake-like density structures, the creation of
planetesimal seeds, and their collisional growth. The linear analysis of the
dissipative gravitational instability shows that the dust layer is secularly
unstable although Toomre's value is larger than unity. However, in the
initial stage, the growth time of the gravitational instability is longer than
that of the dust sedimentation and the decrease in the velocity dispersion.
Thus, the velocity dispersion decreases and the disk shrinks vertically. As the
velocity dispersion becomes sufficiently small, the gravitational instability
finally becomes dominant. Then wake-like density structures are formed by the
gravitational instability. These structures fragment into planetesimal seeds.
The seeds grow rapidly owing to mutual collisions.Comment: 32 pages, 11 figures, accepted for publication in Ap
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