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    Parameter Estimation for an Ornstein-Uhlenbeck Process Driven by a Type of Gaussian Noise with Hurst Parameter $H\in (0,\frac{1}{2})$
    Chen Yong,Li Ying,Sheng Ying,Gu Xiangmeng
    Acta mathematica scientia,Series A    2023, 43 (5): 1483-1518.  
    Abstract137)   HTML6)    PDF(pc) (867KB)(638)       Save

    In 2021, Chen and Zhou consider an inference problem for an Ornstein-Uhlenbeck process driven by a type of centered fractional Gaussian process $(G_t)_{t\ge 0}$. The second order mixed partial derivative of the covariance function $ R(t,\, s)=\mathbb{E}[G_t G_s]$ can be decomposed into two parts, one of which coincides with that of fractional Brownian motion and the other is bounded by $(ts)^{H-1}$ with $H\in (\frac12,\,1)$, up to a constant factor. In this paper, we investigate the same problem but with the assumption of $H\in (0,\,\frac12)$. It is well known that there is a significant difference between the Hilbert space associated with the fractional Gaussian processes in the case of $H\in (\frac12, 1)$ and that of $H\in (0, \frac12)$. The starting point of this paper is a quantitative relation between the inner product of $\mathfrak{H}$ associated with the Gaussian process $(G_t)_{t\ge 0}$ and that of the Hilbert space $\mathfrak{H}_1$ associated with the fractional Brownian motion $(B^{H}_t)_{t\ge 0}$. We prove the strong consistency with $H\in (0, \frac12)$, and the asymptotic normality and the Berry-Esséen bounds with $H\in (0,\frac38)$ for both the least squares estimator and the moment estimator of the drift parameter based on the continuous observations.

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    Some Properties of Quasi-Periodic Functions and Their Applications
    Hu Keqi, Zhang Qingcai
    Acta mathematica scientia,Series A    2024, 44 (6): 1415-1425.  
    Abstract285)   HTML10)    PDF(pc) (560KB)(532)       Save

    In this paper, we estimate relevant properties of quasi-periodic functions, and these properties are applied. Under the additional condition, the conjecture proposed by Yang is solved.

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    The Schödinger Uncertainty Relation in the Fock-Type Spaces
    Li Wenxin,Lian Pan,Liang Yuxia
    Acta mathematica scientia,Series A    2023, 43 (5): 1321-1332.  
    Abstract290)   HTML21)    PDF(pc) (660KB)(530)       Save

    In this paper, the Schödinger uncertainty relation for the unilateral weighted shift operators on Fock space is established, and the explicit expression when the equality attained is given, which further extends the Heisenberg uncertainty relation on Fock space established in [4] and overcomes the difficulty in [16]. In addition, we generalize the uncertainty relation to the multiple operators case. A new uncertainty inequality in the form of non-self adjoint operators is obtained as well.

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    Locally Minimizing Solutions of a Two-component Ginzburg-Landau System
    Xiong Chen, Gao Qi
    Acta mathematica scientia,Series A    2023, 43 (2): 321-340.  
    Abstract220)   HTML10)    PDF(pc) (446KB)(475)       Save

    In this paper, we consider a Ginzburg-Landau functional for a complex vector order parameter $\Psi=[\psi_+, \psi_-]$. In particular, we consider entire solutions in all ${\Bbb R}^2$, which are obtained by blowing up around vortices. Among the entire solutions we distinguish those which are locally minimizing solutions, and we show that locally minimizing solutions must have degrees $n_\pm \in \{0, \pm1\}$. By studying the local structure of these solutions, we also show that one component of the solution vanishes, but the other does not, which describes the coreless vortex phenomenon in physics.

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    Normalized Solutions of the Quasilinear Schrödinger System in Bounded Domains
    Zhang Qian
    Acta mathematica scientia,Series A    2025, 45 (1): 1-30.  
    Abstract337)   HTML12)    PDF(pc) (779KB)(463)       Save

    This paper is concerned with the following nonlinear coupled system
    $\left\{\begin{array}{l} -\Delta u_{1}+\omega_{1} u_{1}-\frac{1}{2} \Delta\left(u_{1}^{2}\right) u_{1}=\mu_{1}\left|u_{1}\right|^{p-1} u_{1}+\beta\left|u_{2}\right|^{\frac{p+1}{2}}\left|u_{1}\right|^{\frac{p-3}{2}} u_{1} \\ -\Delta u_{2}+\omega_{2} u_{2}-\frac{1}{2} \Delta\left(u_{2}^{2}\right) u_{2}=\mu_{2}\left|u_{2}\right|^{p-1} u_{2}+\beta\left|u_{1}\right|^{\frac{p+1}{2}}\left|u_{2}\right|^{\frac{p-3}{2}} u_{2} \\ \int_{\Omega}\left|u_{i}\right|^{2} \mathrm{~d} x=\rho_{i}, \quad i=1,2, \quad\left(u_{1}, u_{2}\right) \in H_{0}^{1}\left(\Omega ; \mathbb{R}^{2}\right) \end{array}\right.$
    and linear coupled system
    $\left\{\begin{array}{l} -\Delta u_{1}+\omega_{1} u_{1}-\frac{1}{2} \Delta\left(u_{1}^{2}\right) u_{1}=\mu_{1}\left|u_{1}\right|^{p-1} u_{1}+\beta u_{2} \\ -\Delta u_{2}+\omega_{2} u_{2}-\frac{1}{2} \Delta\left(u_{2}^{2}\right) u_{2}=\mu_{2}\left|u_{2}\right|^{p-1} u_{2}+\beta u_{1} \\ \int_{\Omega}\left|u_{i}\right|^{2} \mathrm{~d} x=\rho_{i}, \quad i=1,2, \quad\left(u_{1}, u_{2}\right) \in H_{0}^{1}\left(\Omega ; \mathbb{R}^{2}\right) \end{array}\right.$
    where $\Omega\subset\mathbb R^N(N\geq1)$ is a bounded smooth domain, $\omega_i,\ \beta\in\mathbb R$, $\mu_i,\ \rho_i>0,\ i=1,2.$ Moreover, $p>1$ if $N=1,2$ and $1<p\leqslant\frac{3N+2}{N-2}$ if $N\geqslant3$. Using change of variables, on the one hand, we prove the existence and stability of normalized solutions in nonlinear coupled system and the limiting behavior of normalized solutions as $\beta\rightarrow -\infty$. On the other hand, we apply the minimization constraint technique to obtain the existence of normalized solutions for linear coupled system. Compared with some previous results, we extend the existing results to the quasilinear Schrödinger system and also obtain normalized solutions for the linear coupling case.

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    An Extension of Minkowski Formulae for Free Boundary Hypersurfaces in a Ball
    Sheng Weimin, Wang Yinhang
    Acta mathematica scientia,Series A    2023, 43 (6): 1641-1648.  
    Abstract277)   HTML21)    PDF(pc) (508KB)(455)       Save

    In this article, we prove a generalization of Hsiung-Minkowski formula for free boundary hypersurfaces in a ball in space forms. As corollaries, we obtain some Alexandrov-type results.

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    The Rogue Wave Solution of MNLS Equation Based on Hirota's Bi-linear Derivative Transformation
    Tang Yuxuan, Zhou Guoquan
    Acta mathematica scientia,Series A    2023, 43 (1): 132-142.  
    Abstract173)   HTML7)    PDF(pc) (519KB)(437)       Save

    The modified nonlinear Schrodinger (MNLS for brevity) equation and the Derivative nonlinear Schrodinger (DNLS for brevity) equation are two nonlinear differential equations that are closely correlated and fully integrable. Firstly, the spatially periodic breather solution of the MNLS equation has been obtained by method of Hirota's bilinear derivative transform, and then its rogue wave solution is also obtained by a long-wave limit of the Akhmediev-type breather, which can be naturally reduced to a rogue wave solution of the DNLS equation by a simple operation of parameters. The existence of global soliton/rogue wave solutions for the MNLS/DNLS equations is briefly discussed.

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    Boundary Layer Separation of 2-D Incompressible Navier-Stokes-Allen-Cahn System
    Chen Min,Hu Biyan,Luo Hong
    Acta mathematica scientia,Series A    2023, 43 (4): 1123-1132.  
    Abstract96)   HTML1)    PDF(pc) (354KB)(430)       Save

    In this paper, boundary layer separation of 2-D incompressible Navier-Stokes-Allen-Cahn system is considered. Firstly, the condition of boundary layer separation under flat boundary is obtained with the help of the geometric theory of incompressible flow and Taylor expansion. Secondly, the expression for boundary singularity is presented and the condition of boundary layer separation under curved boundary is discovered. The conditions, determined by initial values and external forces, can predict when and where boundary layer separation for Navier-Stokes-Allen-Cahn system will occur.

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    On the Blow-Up Solutions of Inhomogeneous Nonlinear Schrödinger Equation with a Partial Confinement
    Jian Hui, Gong Min, Wang Li
    Acta mathematica scientia,Series A    2023, 43 (5): 1350-1372.  
    Abstract153)   HTML5)    PDF(pc) (797KB)(428)       Save

    This paper is devoted to the Cauchy problem of inhomogeneous nonlinear Schrödinger equation in the presence of a partial confinement, which is an important model in Bose-Einstein condensates. Combining the variational characterization of the ground state of a nonlinear elliptic equation and the conservations of mass and energy, we first obtain a global solution and show the existence of blow-up solutions for some special initial data by scaling techniques. Then, we study the $L^2$-concentration phenomenon for the blow-up solutions. Finally, we apply the variational arguments connected to the above ground state to investigate the dynamics of $L^2$-minimal blow-up solutions, i.e., the limiting profile, mass-concentration and blow-up rate of the blow-up solutions with minimal mass. We extend the global existence and blow-up results of Zhang[34] to the case of inhomogeneous nonlinearities and improve partial results of Pan and Zhang[23] to space dimensions $N\geq2$ in the inhomogeneous case.

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    Time Decay Rate for Large-Solution About 3D Compressible MHD Equations
    Chen Fei,Wang Shuai,Zhao Yongye,Wang Chuanbao
    Acta mathematica scientia,Series A    2023, 43 (5): 1397-1408.  
    Abstract143)   HTML4)    PDF(pc) (697KB)(424)       Save

    This paper focus on time decay rate for large-solution about compressible magnetohydrodynamic equations in $\mathbb{R}^3$. Provided that $(\sigma_{0}-1,u_{0},M_{0})\in L^1\cap H^2$, based on the work of Chen et al.[1], $\|\nabla(\sigma-1,u,M)\|_{H^1}\leqslant C(1+t)^{-\frac{5}{4}}$ is obtained in reference [2], obviously, time decay rate of the 2nd-order derivative of the solution in [2] is not ideal. Here, we improve that of $\|\nabla^2 (\sigma-1,u,M)\|_{L^2}$ to be $(1+t)^{-\frac{7}{4}}$ by the frequency decomposition method[3].

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    The Complete Classification of Solutions to the Step Initial Condition: Analysis and Numerical Verification for the Generalized Gardner Equation in Fluid Mechanics
    Zhang Yan, Hao Huiqin, Guo Rui
    Acta mathematica scientia,Series A    2024, 44 (5): 1242-1282.  
    Abstract75)   HTML3)    PDF(pc) (10179KB)(394)       Save

    In this paper, we investigate the evolution of the initial discontinuity for the generalized Gardner equation through the Whitham modulation theory, which the generalized Gardner equation can describe the transcritical flow of stratified fluids over topography. Firstly, we derive the linear harmonic wave, soliton and nonlinear trigonometric wave in different limiting cases via the periodic waves represented by the Jacobi elliptic functions. Then we obtain the Whitham characteristic velocities and modulation system based on the Riemann invariants by the finite-gap integration method. Since the modulation system of the generalized Gardner equation is neither strictly elliptic nor hyperbolic type, which makes the dynamical evolution behavior more varied in different regions compared to the KdV equation. Furthermore, we perform a complete classification for all wave structures in the cases of positive and negative cubic nonlinear terms, including the dispersive shock wave, rarefaction wave, trigonometric dispersive shock wave, solibore and their combinations. In addition, the correctness of the results is verified by numerical simulations, and the numerical solutions are in good agreement with the analytical solutions. Finally, the influences of the coefficients of the linear and nonlinear terms on the step initial value problem under certain conditions are analyzed.

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    The Inner Layer of a Class of Singularly Perturbed High-Order Equations with Discontinuous Right-Hand Side
    Fu Yuechen, Ni Mingkang
    Acta mathematica scientia,Series A    2024, 44 (5): 1153-1166.  
    Abstract97)   HTML2)    PDF(pc) (711KB)(391)       Save

    This paper introduces some work on singular perturbation problems with discontinuous right-hand side, mainly discusses a class of fourth-order Dirichlet boundary value singular perturbation equations with discontinuous right-hand sides. After introducing complex equation form, we construct a formal asymptotic solution with an internal transfer layer by using the boundary layer function method, and give the existence and residual estimation of smooth solutions. Finally, an example is given to verify the correctness of the algorithm.

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    Existence Results of Periodic Solutions for Semilinear Evolution Equation in Banach Spaces and Applications
    Li Yongxiang,Wei Qilin
    Acta mathematica scientia,Series A    2023, 43 (3): 702-712.  
    Abstract83)   HTML0)    PDF(pc) (361KB)(387)       Save

    In this paper, we deal with the existence of periodic solutions for the semilinear evolution equation in a Banach space $X$,

    $ u'(t)+Au(t)=f(t,\,u(t)),\quad t\in{\Bbb R}, $

    where $A: D(A)\subset X\to X$ is a closed linear operator and $ -A$ generates a $C_{0}$-semigroup $X$, $f:{\Bbb R}\times X\to X$ is a continuous mapping and $f(t,\,x)$ is $\omega$-periodic in $t$. Existence results of $\omega$-periodic mild solutions are obtained by using operator semigroup theory, estimation technique of noncompact measure and fixed point theorem. Examples of applications in parabolic partial differential equations and weakly damped wave equations are present.

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    Exact Multiplicity of Positive Solutions for a Semipositone Mean Curvature Problem with Concave Nonlinearity
    Li Xiaodong, Gao Hongliang, Xu Jing
    Acta mathematica scientia,Series A    2023, 43 (5): 1341-1349.  
    Abstract104)   HTML8)    PDF(pc) (770KB)(386)       Save

    In this paper, we study the exact multiplicity and bifurcation diagrams of positive solutions for the prescribed mean curvature problem in one-dimensional Minkowski space in the form of

    $ \left\{\begin{array}{ll} -\left(\frac{u'}{\sqrt{1-u'^{2}}}\right)'=\lambda f(u), x\in(-L,L),\\ u(-L)=0=u(L), \end{array} \right. $

    where $\lambda>0$ is a bifurcation parameter and $L>0$ is an evolution parameters, $f\in C^{2}([0,\infty), \mathbb{R})$ satisfies $f(0)<0$ and $f$ is concave for $0. In two different cases, we obtain that the above problem has zero, exactly one, or exactly two positive solutions according to different ranges of $\lambda$. The arguments are based upon a detailed analysis of the time map.

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    Existence of Positive Solutions for a Class of Schrödinger-Newton Systems with Critical Exponent
    Cheng Qingfang,Liao Jiafeng,Yuan Yanxiang
    Acta mathematica scientia,Series A    2023, 43 (5): 1373-1381.  
    Abstract142)   HTML6)    PDF(pc) (629KB)(379)       Save

    In this paper, we study the existence of positive solutions for a class of Schrödinger-Newton system with critical exponents on bounded domain, and obtain two positive solutions by the variational method.

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    The Radial Symmetry and Monotonicity of Entire Solutions for Fractional Parabolic Equations
    Tang Yanjuan
    Acta mathematica scientia,Series A    2023, 43 (5): 1409-1416.  
    Abstract131)   HTML3)    PDF(pc) (581KB)(377)       Save

    This paper mainly develops the radial symmetry and monotonicity of entire solutions for fractional parabolic equations. To obtain the symmetry and monotonicity of entire solutions, the narrow region principle and maximum principle for antisymmetric functions in [9] are needed. Furthermore, to circumvent the difficulty from nonlocality for the fractional Laplacian, a fractional parabolic version of the method of moving planes will be adopted.

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    Two-Step Inertial Bregman Proximal Alternating Linearized Minimization Algorithm for Nonconvex and Nonsmooth Problems
    Jing Zhao, Chenzheng Guo
    Acta mathematica scientia,Series A    2024, 44 (6): 1630-1651.  
    Abstract153)   HTML1)    PDF(pc) (9184KB)(376)       Save

    In this paper, for solving a class of nonconvex and nonsmooth nonseparable optimization problems, based on proximal alternating linearized minimization method we propose a new iterative algorithm which combines two-step inertial extrapolation and Bregman distance. By constructing appropriate benefit function, with the help of Kurdyka-Łojasiewicz property we establish the convergence of the whole sequence generated by proposed algorithm. We apply the proposed algorithm to solve sparse nonnegative matrix factorization, signal recovery and quadratic fractional programming problems, and show the effectiveness of proposed algorithm.

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    Survival Analysis of an SVIR Epidemic Model with Media Coverage
    Li Dan,Wei Fengying,Mao Xuerong
    Acta mathematica scientia,Series A    2023, 43 (5): 1595-1606.  
    Abstract161)   HTML4)    PDF(pc) (1602KB)(373)       Save

    We consider the long-term properties of a stochastic SVIR epidemic model with media coverage and the logistic growth in this paper. We firstly derive the fitness of a unique global positive solution. Then we construct appropriate Lyapunov functions and obtain the existence of ergodic stationary distribution when ${R}_{0}^{s}>1$ is valid, and also derive sufficient conditions for persistence in the mean. Moreover, the exponential extinction to the density of the infected is figured out when ${R}_{0}^{e}<1$ holds.

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    Degeneration Behaviors of Solutions and Hybrid Solutions for the New (3+1)-Dimensional KP Equation
    Guo Yanfeng, Cui Jingyi, Xiao Haijun, Zhang Jingjun
    Acta mathematica scientia,Series A    2024, 44 (6): 1520-1536.  
    Abstract78)   HTML1)    PDF(pc) (6402KB)(370)       Save

    We concentrate on the nonlinear wave solutions of the new (3+1)-dimensional KP equation, which was firstly proposed by Wazwaz in 2022. Based on the Hirota bilinear form, the $ P $-breathing solutions are mainly obtained from the $ N $-soliton solutions utilizing the module resonance technique. Then, using parameter limit approach, the Lump solutions are derived by degenerating behaviors of the homoclinic breathing solutions and $ N $-soliton solutions on the basis of the special relations of parameters. In addition, from the partial degeneration of the $ N $-soliton solutions, some hybrid solutions are investigated by the interaction solutions among the breathing, soliton and Lump solutions.

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    Similarity and Unitary Similarity of a Class of Upper Triangular Operator Matrices
    Liqiong Lin,Jiahua Que,Yunnan Zhang
    Acta mathematica scientia,Series A    2022, 42 (5): 1281-1293.  
    Abstract239)   HTML21)    PDF(pc) (268KB)(369)       Save

    This paper introduces a class of upper triangular operator matrices related to Cowen-Douglas operators, and studies its similarity on Banach spaces and its unitary similarity on Hilbert spaces.

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