5,227 research outputs found
Improved Successive Cancellation Decoding of Polar Codes
As improved versions of successive cancellation (SC) decoding algorithm,
successive cancellation list (SCL) decoding and successive cancellation stack
(SCS) decoding are used to improve the finite-length performance of polar
codes. Unified descriptions of SC, SCL and SCS decoding algorithms are given as
path searching procedures on the code tree of polar codes. Combining the ideas
of SCL and SCS, a new decoding algorithm named successive cancellation hybrid
(SCH) is proposed, which can achieve a better trade-off between computational
complexity and space complexity. Further, to reduce the complexity, a pruning
technique is proposed to avoid unnecessary path searching operations.
Performance and complexity analysis based on simulations show that, with proper
configurations, all the three improved successive cancellation (ISC) decoding
algorithms can have a performance very close to that of maximum-likelihood (ML)
decoding with acceptable complexity. Moreover, with the help of the proposed
pruning technique, the complexities of ISC decoders can be very close to that
of SC decoder in the moderate and high signal-to-noise ratio (SNR) regime.Comment: This paper is modified and submitted to IEEE Transactions on
Communication
Production of antimatter Li nuclei in central Au+Au collisions at GeV
Combining the covariant coalescence model and a blast-wave-like analytical
parametrization for (anti-)nucleon phase-space freezeout configuration, we
explore light (anti-)nucleus production in central Au+Au collisions at
GeV. Using the nucleon freezeout configuration (denoted
by FO1) determined from the measured spectra of protons (p), deutrons (d) and
He, we find the predicted yield of He is significantly smaller than
the experimental data. We show this disagreement can be removed by using a
nucleon freezeout configuration (denoted by FO2) in which the nucleons are
assumed to freeze out earlier than those in FO1 to effectively consider the
effect of large binding energy value of He. Assuming the binding energy
effect also exists for the production of ,
, and due to
their similar binding energy values as He, we find the yields of these
heavier (anti-)nuclei can be enhanced by a factor of about one order, implying
that although the stable (anti-)Li nucleus is unlikely to be observed, the
unstable (anti-)Li nucleus could be produced in observable abundance in
Au+Au collisions at GeV where it may be identified
through the p- (-)
invariant mass spectrum. The future experimental measurement on
(anti-) would be very useful to understand the production
mechanism of heavier antimatter.Comment: 8 pages, 2 figures, 3 tables. Typos fixed and one ref added. Accepted
version to appear in PL
Focusing RKKY interaction by graphene P-N junction
The carrier-mediated RKKY interaction between local spins plays an important
role for the application of magnetically doped graphene in spintronics and
quantum computation. Previous studies largely concentrate on the influence of
electronic states of uniform systems on the RKKY interaction. Here we reveal a
very different way to manipulate the RKKY interaction by showing that the
anomalous focusing - a well-known electron optics phenomenon in graphene P-N
junctions - can be utilized to refocus the massless Dirac electrons emanating
from one local spin to the other local spin. This gives rise to rich spatial
interference patterns and symmetry-protected non-oscillatory RKKY interaction
with a strongly enhanced magnitude. It may provide a new way to engineer the
long-range spin-spin interaction in graphene.Comment: 9 pages, 4 figure
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