426 research outputs found
Hydrodynamics with chiral anomaly and charge separation in relativistic heavy ion collisions
Matter with chiral fermions is microscopically described by theory with
quantum anomaly and macroscopically described (at low energy) by anomalous
hydrodynamics. For such systems in the presence of external magnetic field and
chirality imbalance, a charge current is generated along the magnetic field
direction --- a phenomenon known as the Chiral Magnetic Effect (CME). The
quark-gluon plasma created in relativistic heavy ion collisions provides an
(approximate) example, for which the CME predicts a charge separation
perpendicular to the collisional reaction plane. Charge correlation
measurements designed for the search of such signal have been done at RHIC and
the LHC for which the interpretations, however, remain unclear due to
contamination by background effects that are collective flow driven,
theoretically poorly constrained, and experimentally hard to separate. Using
anomalous (and viscous) hydrodynamic simulations, we make a first attempt at
quantifying contributions to observed charge correlations from both CME and
background effects in one and same framework. The implications for the search
of CME are discussed.Comment: 5 pages, 3 figures, Published version in Phys. Lett.
Self-weighted Multiple Kernel Learning for Graph-based Clustering and Semi-supervised Classification
Multiple kernel learning (MKL) method is generally believed to perform better
than single kernel method. However, some empirical studies show that this is
not always true: the combination of multiple kernels may even yield an even
worse performance than using a single kernel. There are two possible reasons
for the failure: (i) most existing MKL methods assume that the optimal kernel
is a linear combination of base kernels, which may not hold true; and (ii) some
kernel weights are inappropriately assigned due to noises and carelessly
designed algorithms. In this paper, we propose a novel MKL framework by
following two intuitive assumptions: (i) each kernel is a perturbation of the
consensus kernel; and (ii) the kernel that is close to the consensus kernel
should be assigned a large weight. Impressively, the proposed method can
automatically assign an appropriate weight to each kernel without introducing
additional parameters, as existing methods do. The proposed framework is
integrated into a unified framework for graph-based clustering and
semi-supervised classification. We have conducted experiments on multiple
benchmark datasets and our empirical results verify the superiority of the
proposed framework.Comment: Accepted by IJCAI 2018, Code is availabl
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