2,673 research outputs found
Computation of the p6 order chiral Lagrangian coefficients from the underlying theory of QCD
We present results of computing the p6 order low energy constants in the
normal part of chiral Lagrangian both for two and three flavor pseudo-scalar
mesons. This is a generalization of our previous work on calculating the p4
order coefficients of the chiral Lagrangian in terms of the quark self energy
Sigma(p2) approximately from QCD. We show that most of our results are
consistent with those we can find in the literature.Comment: 51 pages,2 figure
Definition and Classification of Fermi Surface Anomalies
We propose that the Fermi surface anomaly of symmetry group in any
dimension is universally classified by -symmetric interacting fermionic
symmetry-protected topological (SPT) phases in -dimensional spacetime.
The argument is based on the perspective that the gapless fermions on the Fermi
surface can be viewed as the topological boundary modes of Chern insulators in
the phase space (position-momentum space). Given the non-commutative nature of
the phase space coordinates, we show that the momentum space dimensions should
be counted as negative dimensions for SPT classification purposes. Therefore,
the classification of phase-space Chern insulators (or, more generally
fermionic SPT phases) always reduces to a -dimensional problem, which
can then be answered by the cobordism approach. In addition to the
codimension-1 Fermi surface case, we also discuss the codimension- Fermi
surface case briefly. We provide concrete examples to demonstrate the validity
of our classification scheme, and make connections to the recent development of
Fermi surface symmetric mass generation.Comment: 13 pages + references, 2 figures, 2 tables. Update Tab. II,
clarifications to codimension-p Fermi surface, and references adde
Ego Group Partition: A Novel Framework for Improving Ego Experiments in Social Networks
Estimating the average treatment effect in social networks is challenging due
to individuals influencing each other. One approach to address interference is
ego cluster experiments, where each cluster consists of a central individual
(ego) and its peers (alters). Clusters are randomized, and only the effects on
egos are measured. In this work, we propose an improved framework for ego
cluster experiments called ego group partition (EGP), which directly generates
two groups and an ego sub-population instead of ego clusters. Under specific
model assumptions, we propose two ego group partition algorithms. Compared to
the original ego clustering algorithm, our algorithms produce more egos, yield
smaller biases, and support parallel computation. The performance of our
algorithms is validated through simulation and real-world case studies
Progressive amorphization of GeSbTe phase-change material under electron beam irradiation
Fast and reversible phase transitions in chalcogenide phase-change materials
(PCMs), in particular, Ge-Sb-Te compounds, are not only of fundamental
interests, but also make PCMs based random access memory (PRAM) a leading
candidate for non-volatile memory and neuromorphic computing devices. To RESET
the memory cell, crystalline Ge-Sb-Te has to undergo phase transitions firstly
to a liquid state and then to an amorphous state, corresponding to an abrupt
change in electrical resistance. In this work, we demonstrate a progressive
amorphization process in GeSb2Te4 thin films under electron beam irradiation on
transmission electron microscope (TEM). Melting is shown to be completely
absent by the in situ TEM experiments. The progressive amorphization process
resembles closely the cumulative crystallization process that accompanies a
continuous change in electrical resistance. Our work suggests that if
displacement forces can be implemented properly, it should be possible to
emulate symmetric neuronal dynamics by using PCMs
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