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Green's function Zero and Symmetric Mass Generation [article]

Yichen Xu, Cenke Xu
2021 arXiv   pre-print
Xu, Physical Re- view B 91 (2015), ISSN 1550-235X, A. P. Schnyder, S. Ryu, A. Furusaki, and A. W. W. Ludwig, AIP Conf. Proc. 1134, 10 (2009). 2 S. Ryu, A. Schnyder, A. Furusaki, and A.  ... 
arXiv:2103.15865v1 fatcat:mk5fjeb6dbedrc4hemduwmrmpa

Deconfined Quantum Critical Point with Non-locality [article]

Yichen Xu, Xiao-Chuan Wu, Cenke Xu
2022 arXiv   pre-print
The deconfined quantum critical point (DQCP) between the Néel and valence bond solid (VBS) order was originally proposed in quantum spin systems with a local Hamiltonian. In the last few years analogues of DQCPs with nonlocal interactions have been explored, which can lead to rich possibilities. The nonlocal interactions can either arise from an instantaneous long range interaction in the Hamiltonian, or from gapless modes that reside in one higher spatial dimension. Here we consider another
more » ... hanism of generating nonlocal interactions by coupling the DQCP to the "hot spots" of a Fermi surface. We demonstrate that at least within a substantial energy window, the physics of the DQCP is controlled by a new fixed point with dynamical exponent z > 1
arXiv:2206.14222v1 fatcat:i5vm2h44e5btbga5e2wrq5437e

Boundary Criticality of Topological Quantum Phase Transitions in 2d systems [article]

Xiao-Chuan Wu, Yichen Xu, Hao Geng, Chao-Ming Jian, Cenke Xu
2020 arXiv   pre-print
We discuss the boundary critical behaviors of two dimensional quantum phase transitions with fractionalized degrees of freedom in the bulk, motivated by the fact that usually it is the 1d boundary that is exposed and can be conveniently probed in many experimental platforms. In particular, we mainly discuss boundary criticality of two examples: i. the quantum phase transition between a 2dZ_2 topological order and an ordered phase with spontaneous symmetry breaking; ii. the continuous quantum
more » ... se transition between metal and a particular type of Mott insulator (U(1) spin liquid). This theoretical study could be relevant to many purely 2d systems, where recent experiments have found correlated insulator, superconductor, and metal in the same phase diagram.
arXiv:2001.10550v1 fatcat:xsrccx2vqrbpzgodk36bs3s6wq

Physics of Symmetry Protected Topological phases involving Higher Symmetries and their Applications [article]

Chao-Ming Jian, Xiao-Chuan Wu, Yichen Xu, Cenke Xu
2020 arXiv   pre-print
We discuss physical constructions, and the boundary properties of various symmetry protected topological phases that involve 1-form symmetries, from one spatial dimension (1d) to four spatial dimensions (4d). For example, the prototype 3d boundary state of 4d SPT states involving 1-form symmetries can be either a gapless photon phase (quantum electrodynamics) or gapped topological order enriched by 1-form symmetries, namely the loop excitations of these topological orders carry nontrivial
more » ... symmetry charges. This study also serves the purpose of diagnosing anomaly of 3d states of matter. Connection between SPT states with 1-form symmetries and condensed matter systems such as quantum dimer models at one lower dimension will also be discussed. Whether a quantum dimer model can have a trivial gapped phase or not depends on the nature of its corresponding bulk state in one higher dimension.
arXiv:2009.00023v1 fatcat:xlpmjjd2trb4lm46vnfbucrea4

Provably Secure Certificate-based Proxy Signature Schemes

Jiguo Li, Lizhong Xu, Yichen Zhang
2009 Journal of Computers  
In this paper, we first propose the definition and security model of certificate-based proxy signature (CBPS). We then show that the certificate-based proxy signature scheme presented by Kang, Park and Hahn in CT-RSA 2004 are insecure against key replacement attacks. We further propose two certificate-based proxy signature schemes, which are shown to be existentially unforgeable against adaptive chosen message attacks under the computational Diffie-Hellman assumption in the random oracle model.
more » ... Compared with the certificate-based proxy signature scheme in CT-RSA 2004, one of our schemes enjoys the same signature length and computation cost, another one requires a little more computation and communication cost. Index Terms-certificate-based signature; proxy signature; key replacement attack . His major interests are cryptography theory and technology, cryptography protocol and network and information security. He has published over 30 research papers.
doi:10.4304/jcp.4.6.444-452 fatcat:dacnd326ujgv3m7q7wb45nb35a

Deep Graph Contrastive Representation Learning [article]

Yanqiao Zhu, Yichen Xu, Feng Yu, Qiang Liu, Shu Wu, Liang Wang
2020 arXiv   pre-print
Graph representation learning nowadays becomes fundamental in analyzing graph-structured data. Inspired by recent success of contrastive methods, in this paper, we propose a novel framework for unsupervised graph representation learning by leveraging a contrastive objective at the node level. Specifically, we generate two graph views by corruption and learn node representations by maximizing the agreement of node representations in these two views. To provide diverse node contexts for the
more » ... stive objective, we propose a hybrid scheme for generating graph views on both structure and attribute levels. Besides, we provide theoretical justification behind our motivation from two perspectives, mutual information and the classical triplet loss. We perform empirical experiments on both transductive and inductive learning tasks using a variety of real-world datasets. Experimental experiments demonstrate that despite its simplicity, our proposed method consistently outperforms existing state-of-the-art methods by large margins. Moreover, our unsupervised method even surpasses its supervised counterparts on transductive tasks, demonstrating its great potential in real-world applications.
arXiv:2006.04131v2 fatcat:zdnorcmxmfcvxoukjbndaj5tce

BiCo-Net: Regress Globally, Match Locally for Robust 6D Pose Estimation [article]

Zelin Xu, Yichen Zhang, Ke Chen, Kui Jia
2022 arXiv   pre-print
., 2017] 65.0 80.0 78.0 86.0 70.0 73.0 66.0 100.0 100.0 49.0 78.0 73.0 79.0 79.0 PointFusion [Xu et al., 2018] 70.4 80.7 60.8 61.1 79.1 47.3 63.0 99.9 99.3 71.8 83.2 62.3 78.8 73.7 DenseFusion [Wang et  ... 
arXiv:2205.03536v1 fatcat:mylgsstczjf2vghuoyk7beswle

Hypoxia-inducible factor-1α activates transforming growth factor-β1/Smad signaling and increases collagen deposition in dermal fibroblasts

Xu Mingyuan, Pang Qianqian, Xu Shengquan, Ye Chenyi, Lei Rui, Shen Yichen, Xu Jinghong
2017 OncoTarget  
Hypoxia of local tissue occurs during the scar formation; however, the degree of ischemia and hypoxia in the central areas of keloids is more serious than those in normal scars. Hypoxia-induced factor (HIF), is one of the main cellular responses to hypoxia, allowing cells to adapt to low-oxygen conditions. We investigated the correlation among hypoxia, transforming growth factor-β1/Smad signaling and collagen deposition. Hypoxia up-regulated TGF-β1, Smad2/3, p-Smad2/3, Smad4, and total collagen
more » ... in both normal and keloid fibroblasts via HIF-1α, which was attenuated by HIF-1α inhibition, but TβRII levels were not significantly altered. Silencing Smad4 under hypoxia decreased the mRNA and protein levels of HIF-1α, suggesting upregulated Smad4 may also plays a role in promoting HIF-1α. Finally, we examined the role of the TGF-β1/Smad pathway in collagen deposition. When TβRII was inhibited by ITD-1 under hypoxic conditions, p-Smad2/3 levels and collagen deposition decreased. When inhibited TβRII by siRNA under normoxia, the levels of p-Smad2/3, Smad4 and collagen deposition also decreased. This result demonstrated that hypoxia promoted TGF-β1/Smad signaling via HIF-1α and that both HIF-1α and the TGF-β1/Smad signaling promotes collagen deposition in hypoxia, which is an important mechanism of keloid formation. www.impactjournals.com/oncotarget/
doi:10.18632/oncotarget.23225 pmid:29423039 pmcid:PMC5790456 fatcat:vtr4k4vcgzf2tlvht4ntbjyh5y

MicroRNA-152-5p inhibits proliferation and migration and promotes apoptosis by regulating expression of Smad3 in human keloid fibroblasts

Qianqian Pang, Yuming Wang, Mingyuan Xu, Jiachao Xu, Shengquan Xu, Yichen Shen, Jinghong Xu, Rui Lei
2019 BMB Reports  
Keloids are the most common pathological form of trauma healing, with features that seriously affect appearance and body function, are difficult to treat and have a high recurrence rate. Emerging evidence suggests that miRNAs are involved in a variety of pathological processes and play an important role in the process of fibrosis. In this study, we investigated the function and regulatory network of miR-152-5p in keloids. The miRNA miR-152-5p is frequently downregulated in keloid tissue and
more » ... ary cells compared to normal skin tissue and fibroblasts. In addition, the downregulation of miR-152-5p is significantly associated with the proliferation, migration and apoptosis of keloid cells. Overexpression of miR-152-5p significantly inhibits the progression of fibrosis in keloids. Smad3 is a direct target of miR-152-5p, and knockdown of Smad3 also inhibits fibrosis progression, consistent with the overexpression of miR-152-5p. The interaction between miR-152-5p and Smad3 occurs through the Erk1/2 and Akt pathways and regulates collagen3 production. In summary, our study demonstrates that miR-152-5p/Smad3 regulatory pathways involved in fibrotic progression may be a potential therapeutic target of keloids. [BMB Reports 2019; 52(3): 202-207].
pmid:30638178 pmcid:PMC6476487 fatcat:wgyngugienb3nc5ieog3pdmh3i

Non-Landau Quantum Phase Transitions and nearly-Marginal non-Fermi Liquid [article]

Yichen Xu, Hao Geng, Xiao-Chuan Wu, Chao-Ming Jian, Cenke Xu
2020 arXiv   pre-print
Non-fermi liquid and unconventional quantum critical points (QCP) with strong fractionalization are two exceptional phenomena beyond the classic condensed matter doctrines, both of which could occur in strongly interacting quantum many-body systems. This work demonstrates that using a controlled method one can construct a non-Fermi liquid within a considerable energy window based on the unique physics of unconventional QCPs. We will focus on the "nearly-marginal non-Fermi liquid", defined as a
more » ... tate whose fermion self-energy scales as Σ_f(i ω) ∼ i sgn(ω)|ω|^α with α close to 1 in a considerable energy window. The nearly-marginal non-fermi liquid is obtained by coupling an electron fermi surface to unconventional QCPs that are beyond the Landau's paradigm. This mechanism relies on the observation that the anomalous dimension η of the order parameter of these unconventional QCPs can be close to 1, which is significantly larger than conventional Landau phase transitions, for example the Wilson-Fisher fixed points. The fact that η∼ 1 justifies a perturbative renormalization group calculation proposed earlier. Various candidate QCPs that meet this desired condition are proposed.
arXiv:1911.08503v2 fatcat:ur2ddrhxpfevja2bgewj4guyiy

Evaluating bistability of Bax activation switch

Tingzhe Sun, Xuzhu Lin, Yinna Wei, Yichen Xu, Pingping Shen
2010 FEBS Letters  
Mitochondrial apoptotic pathway is precisely controlled by BCL-2 family. Complex interactions of BCL-2 family proteins constitute a bistable switch of which detailed experimental and theoretical delineation remains elusive. In this paper, combined approaches were used to explore the bistability of Bax activation switch. We found that Bax activation is indeed in an 'all-or-none' manner. The 'variable-delay, snap-action' nature for Bax activation is further explored theoretically. We suggest that
more » ... bistability is largely attributed to topological structure and shows considerable robustness. Therefore, our study characterizes dynamics and sensitivities in intrinsic apoptotic pathway. Crown (P. Shen). 1 These authors contributed equally to this work. FEBS Letters 584 (2010) 954-960 j o u r n a l h o m e p a g e : w w w . F E B S L e t t e r s . o r g
doi:10.1016/j.febslet.2010.01.034 pmid:20096692 fatcat:2fb6fvssfjg75ljvpp5cmr3cpy

Fundamental Tradeoffs in Uplink Grant-Free Multiple Access with Protected CSI [article]

Dongyang Xu, Pinyi Ren, Yichen Wang, James A. Ritcey
2019 arXiv   pre-print
In the envisioned 5G, uplink grant-free multiple access will become the enabler of ultra-reliable low-latency communications (URLLC) services. By removing the forward scheduling request (SR) and backward scheduling grant (SG), pilot-based channel estimation and data transmission are launched in one-shot communications with the aim of maintaining the reliability of 99.999% or more and latency of 1ms or less under 5G new radio (NR) numerologies. The problem is that channel estimation can easily
more » ... ffer from pilot aware attack which significantly reduces the system reliability. To solve this, we proposed to apply the hierarchical 2-D feature coding (H2DF) coding on time-frequency-code domain to safeguard channel state information (CSI), which informs a fundamental rethinking of reliability, latency and accessibility. Considering uplink large-scale single-input multiple-output (SIMO) reception of short packets, we characterize the analytical closed-form expression of reliability and define the accessibility of system. We find two fundamental tradeoffs: reliability-latency and reliability-accessibility. With the the help of the two fundamental trade-offs, we demonstrate how CSI protection could be integrated into uplink grant-free multiple access to strengthen URLLC services comprehensively.
arXiv:1909.01521v1 fatcat:bnvnhmcybzboxkjveefs6tkviq

An Empirical Study of Graph Contrastive Learning [article]

Yanqiao Zhu, Yichen Xu, Qiang Liu, Shu Wu
2021 arXiv   pre-print
Graph Contrastive Learning (GCL) establishes a new paradigm for learning graph representations without human annotations. Although remarkable progress has been witnessed recently, the success behind GCL is still left somewhat mysterious. In this work, we first identify several critical design considerations within a general GCL paradigm, including augmentation functions, contrasting modes, contrastive objectives, and negative mining techniques. Then, to understand the interplay of different GCL
more » ... components, we conduct extensive, controlled experiments over a set of benchmark tasks on datasets across various domains. Our empirical studies suggest a set of general receipts for effective GCL, e.g., simple topology augmentations that produce sparse graph views bring promising performance improvements; contrasting modes should be aligned with the granularities of end tasks. In addition, to foster future research and ease the implementation of GCL algorithms, we develop an easy-to-use library PyGCL, featuring modularized CL components, standardized evaluation, and experiment management. We envision this work to provide useful empirical evidence of effective GCL algorithms and offer several insights for future research.
arXiv:2109.01116v2 fatcat:kjfrkg26tbfxhoiomx2mdgao5y

Structure-Aware Hard Negative Mining for Heterogeneous Graph Contrastive Learning [article]

Yanqiao Zhu, Yichen Xu, Hejie Cui, Carl Yang, Qiang Liu, Shu Wu
2021 arXiv   pre-print
Recently, heterogeneous Graph Neural Networks (GNNs) have become a de facto model for analyzing HGs, while most of them rely on a relative large number of labeled data. In this work, we investigate Contrastive Learning (CL), a key component in self-supervised approaches, on HGs to alleviate the label scarcity problem. We first generate multiple semantic views according to metapaths and network schemas. Then, by pushing node embeddings corresponding to different semantic views close to each
more » ... (positives) and pulling other embeddings apart (negatives), one can obtain informative representations without human annotations. However, this CL approach ignores the relative hardness of negative samples, which may lead to suboptimal performance. Considering the complex graph structure and the smoothing nature of GNNs, we propose a structure-aware hard negative mining scheme that measures hardness by structural characteristics for HGs. By synthesizing more negative nodes, we give larger weights to harder negatives with limited computational overhead to further boost the performance. Empirical studies on three real-world datasets show the effectiveness of our proposed method. The proposed method consistently outperforms existing state-of-the-art methods and notably, even surpasses several supervised counterparts.
arXiv:2108.13886v1 fatcat:sqsy56q3incsxj5bi36ixxg74q

Icones of Medicinal Fungi from China

Donald H. Pfister, Ying Jianzhe, Mao Xiaolan, Ma Qiming, Zong Yichen, Wen Huaan, Xu Yuehan
1990 Mycologia  
doi:10.2307/3759865 fatcat:qycwhk2nr5bkncyo4fxsjr5kpy
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