20,701 research outputs found
State-Augmentation Transformations for Risk-Sensitive Reinforcement Learning
In the framework of MDP, although the general reward function takes three
arguments-current state, action, and successor state; it is often simplified to
a function of two arguments-current state and action. The former is called a
transition-based reward function, whereas the latter is called a state-based
reward function. When the objective involves the expected cumulative reward
only, this simplification works perfectly. However, when the objective is
risk-sensitive, this simplification leads to an incorrect value. We present
state-augmentation transformations (SATs), which preserve the reward sequences
as well as the reward distributions and the optimal policy in risk-sensitive
reinforcement learning. In risk-sensitive scenarios, firstly we prove that, for
every MDP with a stochastic transition-based reward function, there exists an
MDP with a deterministic state-based reward function, such that for any given
(randomized) policy for the first MDP, there exists a corresponding policy for
the second MDP, such that both Markov reward processes share the same reward
sequence. Secondly we illustrate that two situations require the proposed SATs
in an inventory control problem. One could be using Q-learning (or other
learning methods) on MDPs with transition-based reward functions, and the other
could be using methods, which are for the Markov processes with a deterministic
state-based reward functions, on the Markov processes with general reward
functions. We show the advantage of the SATs by considering Value-at-Risk as an
example, which is a risk measure on the reward distribution instead of the
measures (such as mean and variance) of the distribution. We illustrate the
error in the reward distribution estimation from the direct use of Q-learning,
and show how the SATs enable a variance formula to work on Markov processes
with general reward functions
AEDNet: Adaptive Edge-Deleting Network For Subgraph Matching
Subgraph matching is to find all subgraphs in a data graph that are
isomorphic to an existing query graph. Subgraph matching is an NP-hard problem,
yet has found its applications in many areas. Many learning-based methods have
been proposed for graph matching, whereas few have been designed for subgraph
matching. The subgraph matching problem is generally more challenging, mainly
due to the different sizes between the two graphs, resulting in considerable
large space of solutions. Also the extra edges existing in the data graph
connecting to the matched nodes may lead to two matched nodes of two graphs
having different adjacency structures and often being identified as distinct
objects. Due to the extra edges, the existing learning based methods often fail
to generate sufficiently similar node-level embeddings for matched nodes. This
study proposes a novel Adaptive Edge-Deleting Network (AEDNet) for subgraph
matching. The proposed method is trained in an end-to-end fashion. In AEDNet, a
novel sample-wise adaptive edge-deleting mechanism removes extra edges to
ensure consistency of adjacency structure of matched nodes, while a
unidirectional cross-propagation mechanism ensures consistency of features of
matched nodes. We applied the proposed method on six datasets with graph sizes
varying from 20 to 2300. Our evaluations on six open datasets demonstrate that
the proposed AEDNet outperforms six state-of-the-arts and is much faster than
the exact methods on large graphs
Axially deformed relativistic Hartree Bogoliubov with separable pairing force
A separable form of pairing interaction in the channel has been
introduced and successfully applied in the description of both static and
dynamic properties of superfluid nuclei. By adjusting the parameters to
reproduce the pairing properties of the Gogny force in nuclear matter, this
separable pairing force is successful in depicting the pairing properties of
ground states and vibrational excitations of spherical nuclei on almost the
same footing as the original Gogny force. In this article, we extend these
investigations for Relativistic Hartree Bogoliubov theory in deformed nuclei
with axial symmetry (RHBZ) using the same separable pairing interaction. In
order to preserve translational invariance we construct one- and
two-dimensional Talmi-Moshinsky brackets for the cylindrical harmonic
oscillator basis. We show that the matrix elements of this force can then be
expanded in a series of separable terms. The convergence of this expansion is
investigated for various deformations. We observe a relatively fast
convergence. This allows for a considerable reduction in computing time as
compared to RHBZ-calculations with the full Gogny force in the pairing channel.
As an example we solve the RHBZ equations with this separable pairing force for
the ground states of the chain of Sm-isotopes. Good agreement with the
experimental data as well as with other theoretical results is achieved.Comment: 8 pages, 5 figures. accepted by Phys. Rev.
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