889 research outputs found
Classification of Symmetry-Protected Phases for Interacting Fermions in Two Dimensions
Recently, it has been shown that two-dimensional bosonic symmetry-protected
topological(SPT) phases with on-site unitary symmetry can be completely
classified by the group cohomology class . Later, group
super-cohomology class was proposed as a partial classification for SPT phases
of interacting fermions. In this work, we revisit this problem based on the
mathematical framework of -extension of unitary braided tensor
category(UBTC) theory. We first reproduce the partial classifications given by
group super-cohomology, then we show that with an additional structure, a complete classification of SPT phases for
two-dimensional interacting fermion systems for a total symmetry group
can be achieved. We also discuss the classification of
interacting fermionic SPT phases protected by time-reversal symmetry.Comment: references added; published versio
Continuous-variable controlled-Z gate using an atomic ensemble
The continuous-variable controlled-Z gate is a canonical two-mode gate for
universal continuous-variable quantum computation. It is considered as one of
the most fundamental continuous-variable quantum gates. Here we present a
scheme for realizing continuous-variable controlled-Z gate between two optical
beams using an atomic ensemble. The gate is performed by simply sending the two
beams propagating in two orthogonal directions twice through a spin-squeezed
atomic medium. Its fidelity can run up to one if the input atomic state is
infinitely squeezed. Considering the noise effects due to atomic decoherence
and light losses, we show that the observed fidelities of the scheme are still
quite high within presently available techniques.Comment: 7 pages, 3 figures, to appear in Physical Review
Symmetric Mass Generation in the 1+1 Dimensional Chiral Fermion 3-4-5-0 Model
Lattice regularization of chiral fermions has been a long-standing problem in
physics. In this work, we present the density matrix renormalization group
(DMRG) simulation of the 3-4-5-0 model of (1+1)D chiral fermions with an
anomaly-free chiral U(1) symmetry, which contains two left-moving and two
right-moving fermions carrying U(1) charges 3,4 and 5,0, respectively.
Following the Wang-Wen chiral fermion model, we realize the chiral fermions and
their mirror partners on the opposite boundaries of a thin strip of (2+1)D
lattice model of multi-layer Chern insulator, whose finite-width implies the
quantum system is effectively (1+1)D. By introducing carefully designed two
sets of six-fermion local interactions to the mirror sector only, we
demonstrate that the mirror fermions can be gapped out by the interaction
beyond a critical strength without breaking the chiral U(1) symmetry, via the
symmetric mass generation (SMG) mechanism. We show that the interaction-driven
gapping transition is in the Berezinskii-Kosterlitz-Thouless (BKT) universality
class. We determine the evolution of Luttinger parameters before the
transition, which confirms that the transition happens exactly at the point
when the interaction term becomes marginal. As the mirror sector is gapped
after the transition, we check that the fermions in the light chiral fermion
sector remain gapless, which provides the desired lattice regularization of
chiral fermions.Comment: 5 + 3 pages, Symmetric Mass Generation of the chiral fermion model
arXiv:1307.748
Danshensu for Myocardial Ischemic Injury: Preclinical Evidence and Novel Methodology of Quality Assessment Tool
Background: Danshensu (DSS) possesses unique bioactivity on the cardiovascular system. However, there is a lack of systematical summary of DSS for acute myocardial ischemia injury and no quality assessment tool for the systematical review of cell experiments. Here, we aimed to assess the preclinical evidences and possible mechanisms of DSS for myocardial ischemia injury, and to develop a quality assessment tool for the systematical review of cell experiments.Methods: Thirty-two studies with 473 animals and 134 cells were identified by searching seven databases. All data analysis was performed using RevMan 5.3. CAMARADES 10-item checklist was used to assess the methodological quality of animal experiments. A new 10-item checklist was first developed to assess the methodological quality of cell studies.Results: The score of study quality ranged from 3 to 7 points in animal studies, while the cell studies scored 3–6 points. Meta-analysis showed that DSS had significant effects on reducing myocardial infarct (MI) size in vivo, and increasing cell viability and reducing apoptosis rate in vitro compared with controls (P < 0.01). The possible mechanisms of DSS for MI are improving circulation, antioxidant, anti-apoptosis, anti-inflammatory, promoting angiogenesis, anti-excessive autophagy, anti-calcium overload, and improving energy metabolism.Conclusions: DSS could exert cardioprotective effect on myocardial ischemia injury, and thus is a probable candidate for further clinical trials andtreatment of AMI. In addition, the newly devloped 10-item checklist for assessing methodological quality of cell study that recommened to use the sysmatic review of cell studies
Limited Genetic Connectivity Among Sargassum horneri (Phaeophyceae) Populations in the Chinese Marginal Seas Despite Their high Dispersal Capacity
Sargassum horneri is a habitat-forming species in the Northwest Pacific and an important contributor to seaweed rafts. In this study, 131 benthic samples and 156 floating samples were collected in the Yellow Sea and East China Sea (ECS) to test the effects of seaweed rafts on population structure and connectivity. Our results revealed high levels of genetic diversity in both benthic and floating samples based on concatenated mitochondrial markers (rpl5-rps3, rnl-atp9, and cob-cox2). Phylogenetic analyses consistently supported the existence of two lineages (lineages I and II), with divergence dating to c. 0.692 Mya (95% HPD: 0.255-1.841 Mya), indicating that long-term isolation may have occurred during the mid-Pleistocene (0.126-0.781 Mya). Extended Bayesian skyline plots demonstrated a constant population size over time in lineage I and slight demographic expansion in lineage II. Both lineages were found in each marginal sea (including both benthic and floating samples), but PCoA, F-ST, and AMOVA analyses consistently revealed deep genetic variation between regions. Highly structured phylogeographic pattern supports limited genetic connectivity between regions. IMA analyses demonstrated that asymmetric gene flow between benthic populations in the North Yellow Sea (NYS) and ECS was extremely low (ECS -> NYS, 2Nm = 0.6), implying that high dispersal capacity cannot be assumed to lead to widespread population connectivity, even without dispersal barriers. In addition, there were only a few shared haplotypes between benthic and floating samples, suggesting the existence of hidden donors for the floating masses in the Chinese marginal seas
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