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Jiang Zhou

Publications and source records attributed to Jiang Zhou.

At least 73 records · Page 4Linked to original sources
arXiv2021

Incident-angle dependence of deformation characteristics of aluminum surface under low-energy xenon-ion impact

Ion thruster is a revolution technology with potential applications in space mission but the thrusters operation lifetime is limited by the sputtering from thruster components. In this work, molecular dynamic simulations are performed to explore the dependence of deformation characteristics of an aluminum surface on incident angle and kinetic energy under low-energy xenon-ion impact. The fraction of non-12-coordinated atoms is used to quantitatively characterize the microstructural evolution and defect density levels. It is found that defect density level has a linear relation with incident energy, and there exists a critical incident angle around 20 degrees, at which the aluminum surface has the maximum defect density level. In addition, a collision model is developed to theoretically reveal the physical mechanisms behind the dependence. Our findings may helpful in developing long endurance electric propulsion devices for practical applications.

cond-mat.mtrl-sci↗
arXiv2020

Fermionic criticality with enlarged fluctuations in Dirac semimetals

The fluctuations-driven continuous quantum criticality has sparked tremendous interest in condensed matter physics. It has been verified that the gapless fermions fluctuations can change the nature of phase transition at criticality. In this paper, we study the fermionic quantum criticality with enlarged Ising$\times$Ising fluctuations in honeycomb lattice materials. The Gross-Neveu-Yukawa theory for the multicriticality between the semimetallic phase and two ordered phases that break Ising symmetry is investigated by employing perturbative renormalization group approach. We first determine the critical range in which the quantum fluctuations may render the phase transition continuous. We find that the Ising criticality is continuous only when the flavor numbers of four-component Dirac fermions $N_f\geq1/4$. Using the $ε$ expansion in four space-time dimensions, we then study the Ising$\times$Ising multicriticality stemming from the symmetry-breaking electronic instabilities. We analyze the underlying fixed-point structure and compute the critical exponents for the Ising$\times$Ising Gross-Neveu-Yukawa universality class. Further, the correlation scaling behavior for the fermion bilinear on the honeycomb lattice at the multicritical point are also briefly discussed.

cond-mat.str-el↗
arXiv2020

Parity Anomaly of Lattice Maxwell Fermions in Two Spatial Dimensions

Unconventional lattice fermions with high degeneracies beyond Weyl and Dirac fermions have attracted intensive attention in recent years. In this paper, attention is drawn to the pseudospin-1 Maxwell fermions and the $(2+1)$ dimensional parity anomaly, which goes beyond the scope of "fermion doubling theorem". We have derived the Hall conductivity of a single Maxwell fermion, and showcased each Maxwell fermion contributes a quantized Hall conductance $e^{2}/h$. We observe that the parity is spontaneously broken in the effective theory of lattice Maxwell fermions interacting with an (auxiliary) $U(1)$ gauge field, leading to an effective anomaly-induced Chern-Simons theory. An interesting observation from the parity anomaly is that the lattice Maxwell fermions beyond the "fermion doubling theorem", so there exists single Maxwell fermion in a lattice model. In addition, our work indicates the quantum anomaly in odd-dimensional spinor space.

cond-mat.str-el↗
arXiv2020

Critical behavior of QED$_3$--Gross-Neveu-Yukawa Theory in an Arbitrary Gauge

The chiral QED$_3$--Gross-Neveu-Yukawa (QED$_3$-GNY) theory is a $2+1$-dimensional U(1) gauge theory with $N_f$ flavors of four-component Dirac fermions coupled to a scalar field. For $N_f=1$, the specific chiral Ising QED$_3$-GNY model has recently been conjectured to be dual to the deconfined quantum critical point that describes Neel--valence-bond-solid transition of frustrated quantum magnets on square lattice. We study the universal critical behaviors of the chiral QED$_3$-GNY model in $d=4-ε$ dimensions for an arbitrary $N_f$ . We calculate the boson anomalous dimensions, inverse correlation length exponent, as well as the scaling dimensions of nonsinglet fermion bilinear in the chiral QED$_3$-GNY model. The Pad$\acute{e}$ estimates for the exponents are obtained in the chiral Ising-, XY- and Heisenberg-QED$_3$-GNY universality class respectively. We also establish the general condition of the supersymmetric criticality for the ungauged QED$_3$-GNY model. For the conjectured duality between chiral QED$_3$-GNY critical point and deconfined quantum critical point, we find the inverse correlation length exponent has a lower boundary $ν^{-1}>0.75$, beyond which the Ising-QED$_3$-GNY--$\mathbb{C}$P$^1$ duality may hold.

cond-mat.str-el↗
arXiv2020

Integrating Boundary Assembling into a DNN Framework for Named Entity Recognition in Chinese Social Media Text

Named entity recognition is a challenging task in Natural Language Processing, especially for informal and noisy social media text. Chinese word boundaries are also entity boundaries, therefore, named entity recognition for Chinese text can benefit from word boundary detection, outputted by Chinese word segmentation. Yet Chinese word segmentation poses its own difficulty because it is influenced by several factors, e.g., segmentation criteria, employed algorithm, etc. Dealt improperly, it may generate a cascading failure to the quality of named entity recognition followed. In this paper we integrate a boundary assembling method with the state-of-the-art deep neural network model, and incorporate the updated word boundary information into a conditional random field model for named entity recognition. Our method shows a 2% absolute improvement over previous state-of-the-art results.

cs.CL↗
arXiv2017

Inverse Perron values and connectivity of a uniform hypergraph

In this paper, we show that a uniform hypergraph $\mathcal{G}$ is connected if and only if one of its inverse Perron values is larger than $0$. We give some bounds on the bipartition width, isoperimetric number and eccentricities of $\mathcal{G}$ in terms of inverse Perron values. By using the inverse Perron values, we give an estimation of the edge connectivity of a $2$-design, and determine the explicit edge connectivity of a symmetric design. Moreover, relations between the inverse Perron values and resistance distance of a connected graph are presented.

math.CO↗
arXiv2017

A note on commutator in the multilinear setting

Let $m\in \mathbb{N}$ and $\vec{b}=(b_{1},\cdots,b_{m})$ be a collection of locally integrable functions. It is proved that $b_{1},b_{2},\cdots, b_{m}\in BMO$ if and only if $$\sup_{Q}\frac{1}{|Q|^{m}}\int_{Q^{m}}\Big|\sum_{i=1}^{m}\big(b_{i}(x_{i})-(b_{i})_{Q}\big)\Big|d\vec{x}<\infty,$$ where $(b_{i})_{Q}=\frac{1}{|Q|}\int_{Q}b_{i}(x)dx$. As an application, we show that if the linear commutator of certain multilinear Calderón-Zygmund operator $[Σ\vec{b},T]$ is bounded from $L^{p_{1}}\times\cdots\times L^{p_{m}}$ to $L^{p}$ with $\sum_{i=1}^{m}1/p_{i}=1/p$ and $1<p,p_{1},\cdots,p_{m}<\infty$, then $b_{1},\cdots,b_{m}\in BMO$. Therefore, the result of Chaffee \cite{C} (or Li and Wick \cite{LW}) is extended to the general case.

math.CA↗
arXiv2017

Duality of deconfined quantum critical point in two dimensional Dirac semimetals

In this paper we discuss the N$\acute{e}$el and Kekul$\acute{e}$ valence bond solids quantum criticality in graphene Dirac semimetal. Considering the quartic four-fermion interaction $g(\barψ_iΓ_{ij}ψ_j)^2$ that contains spin,valley, and sublattice degrees of freedom in the continuum field theory, we find the microscopic symmetry is spontaneously broken when the coupling $g$ is greater than a critical value $g_c$. The symmetry breaking gaps out the fermion and leads to semimetal-insulator transition. All possible quartic fermion-bilinear interactions give rise to the uniform critical coupling, which exhibits the multicritical point for various orders and the Landau-forbidden quantum critical point. We also investigate the typical critical point between N$\acute{e}$el and Kekul$\acute{e}$ valence bond solid transition when the symmetry is broken. The quantum criticality is captured by the Wess-Zumino-Witten term and there exist a mutual-duality for N$\acute{e}$el-Kekul$\acute{e}$ VBS order. We show the emergent spinon in the N$\acute{e}$el-Kekul$\acute{e}$ VBS transition , from which we conclude the phase transition is a deconfined quantum critical point. Additionally, the connection between the index theorem and zero energy mode bounded by the topological defect in the Kekul$\acute{e}$ VBS phase is studied to reveal the N$\acute{e}$el-Kekul$\acute{e}$ VBS duality.

cond-mat.str-el↗
arXiv2017

Necessary and sufficient conditions for boundedness of commutators of bilinear Hardy-Littlewood maximal function

Let $\mathcal{M}$ be the bilinear Hardy-Littlewood maximal function and $\vec{b}=(b,b)$ be a collection of locally integrable functions. In this paper, the authors establish characterizations of the weighted {\rm BMO} space in terms of several different commutators of bilinear Hardy-Littlewood maximal function, respectively; these commutators include the maximal iterated commutator $\mathcal{M}_{Π\vec{b}}$, the maximal linear commutator $\mathcal{M}_{Σ\vec{b}}$, the iterated commutator $[Π\vec{b},\mathcal{M}]$ and the linear commutator $[Σ\vec{b},\mathcal{M}]$.

math.FA↗
arXiv2017

Central BMO spaces with variable exponent

In this paper, the central BMO spaces with variable exponent are introduced. As an application, we characterize these spaces by the boundedness of commutators of Hardy operator and its dual operator on variable Lebesgue spaces. The boundedness of vector-valued commutators on Herz spaces with variable exponent are also considered.

math.FA↗
arXiv2017

Characterizations of weighted BMO space and its application

In this paper, we prove that the weighted BMO space as follows $${\rm BMO}^{p}(ω)=\Big\{f\in L^{1}_{\rm loc}:\sup_{Q}\|χ_{Q}\|^{-1}_{L^{p}(ω)}\big\|(f-f_{Q})ω^{-1}χ_{Q}\big\|_{L^{p}(ω)}<\infty\Big\}$$ is independent of the scale $p\in (0,\infty)$ in sense of norm when $ω\in A_{1}$. Moreover, we can replace $L^{p}(ω)$ by $L^{p,\infty}(ω)$. As an application, we characterize this space by the boundedness of the bilinear commutators $[b,T]_{j} (j=1,2)$, generated by the bilinear convolution type Calderón-Zygmund operators and the symbol $b$, from $L^{p_{1}}(ω)\times L^{p_{2}}(ω)$ to $L^{p}(ω^{1-p})$ with $1<p_{1},p_{2}<\infty$, $1/p=1/p_{1}+1/p_{2}$ and $ω\in A_{1}$. Thus we answer the open problem proposed in \cite{C} affirmatively.

math.FA↗
arXiv2017

Boundedness and Compactness of commutator of Hardy-Littlewood maximal operator

We study the mapping property of the commutator of bilinear Hardy-Littlewood maximal operator in homogeneous Triebel-Lizorkin space. We also show that the commutator of bilinear Hardy-Littlewood maximal operator is a compact operator acting on product of Lebesgue spaces. The results are new even in the linear case.

math.FA↗
arXiv2017

Occupation times of refracted Levy processes with jumps having rational Laplace transforms

We investigate a refracted Levy process driven by a jump diffusion process, whose jumps have rational Laplace transforms. For such a stochastic process, formulas for the Laplace transform of its occupation times are deduced. To derive the main results, some modifications on our previous approach have been made. In addition, we obtain a very interesting identity, which is conjectured to hold for a general refracted Levy process.

math.PR↗
arXiv2017

Sharp estimates for commutators of bilinear operators on Morrey type spaces

Denote by $T$ and $I_α$ the bilinear Calderón-Zygmund operators and bilinear fractional integrals, respectively. In this paper, it is proved that if $b_{1},b_{2}\in {\rm CMO}$ (the {\rm BMO}-closure of $C^{\infty}_{c}(\mathbb{R}^n)$), $[Π\vec{b},T]$ and $[Π\vec{b},I_α]$ $(\vec{b}=(b_{1},b_{2}))$ are all the compact operators from $\mathcal{M}^{p_{0}}_{\vec{P}}$ (the norm of $\mathcal{M}^{p_{0}}_{\vec{P}}$ is strictly smaller than $2-$fold product of the Morrey norms) to $M^{q_{0}}_{q}$ for some suitable indexes $p_{0},p_{1},p_{2}$ and $q_{0},q$. Specially, we also show that if $b_{1}=b_{2}$, then $b_{1}, b_{2}\in {\rm CMO}$ is necessary for the compactness of $[Π\vec{b},I_α]$ on Morrey space.

math.FA↗
arXiv2016

Characterizations of the BMO and Lipschitz spaces via commutators on weak Lebesgue and Morrey spaces

We prove that the weak Morrey space $WM^{p}_{q}$ is contained in the Morrey space $M^{p}_{q_{1}}$ for $1\leq q_{1}< q\leq p<\infty$. As applications, we show that if the commutator $[b,T]$ is bounded from $L^p$ to $L^{p,\infty}$ for some $p\in (1,\infty)$, then $b\in \mathrm{BMO}$, where $T$ is a Calderón-Zygmund operator. Also, for $1<p\leq q<\infty$, $b\in \mathrm{BMO}$ if and only if $[b,T]$ is bounded from $M^{p}_{q}$ to $WM_{q}^{p}$. For $b$ belonging to Lipschitz class, we obtain similar results.

math.FA↗
arXiv2016

Characterization of CMO via compactness of the commutators of bilinear fractional integral operators

Let $I_α$ be the bilinear fractional integral operator, $B_α$ be a more singular family of bilinear fractional integral operators and $\vec{b}=(b,b)$. Bényi et al. in \cite{B1} showed that if $b\in {\rm CMO}$, the {\rm BMO}-closure of $C^{\infty}_{c}(\mathbb{R}^n)$, the commutator $[b,B_α]_{i}(i=1,2)$ is a separately compact operator. In this paper, it is proved that $b\in {\rm CMO}$ is necessary for $[b,B_α]_{i}(i=1,2)$ is a compact operator. Also, the authors characterize the compactness of the {\bf iterated} commutator $[Π\vec{b},I_α]$ of bilinear fractional integral operator. More precisely, the commutator $[Π\vec{b},I_α]$ is a compact operator if and only if $b\in {\rm CMO}$.

math.FA↗
arXiv2016

Another characterizations of Muckenhoupt $A_{p}$ class

This manuscript addresses Muckenhoupt $A_{p}$ weight theory in connection to Morrey and BMO spaces. It is proved that $ω$ belongs to Muckenhoupt $A_{p}$ class, if and only if Hardy-Littlewood maximal function $M$ is bounded from weighted Lebesgue spaces $L^{p}(ω)$ to weighted Morrey spaces $M^{p}_{q}(ω)$ for $1<q< p<\infty$. As a corollary, if $M$ is (weak) bounded on $M^{p}_{q}(ω)$, then $ω\in A_{p}$. The $A_{p}$ condition also characterizes the boundedness of the Riesz transform $R_{j}$ and convolution operators $T_ε$ on weighted Morrey spaces. Finally, we show that $ω\in A_{p}$ if and only if $ω\in \mathrm{BMO}^{p'}(ω)$ for $1\leq p< \infty$ and $1/p+1/p'=1$.

math.FA↗