2023-10-25 2026, Volume 14 Issue 1

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  • research-article
    Hua-Lin Huang, Lili Liao, Huajun Lu, Yu Ye, Chi Zhang

    This paper is mainly concerned with identities like

    x1d+x2d++xrdy1d+y2d+ynd=z1d+z2d++zmd
    where
    d>2,
    m{n,n+1},
    x=(x1,x2,,xr)
    and
    y=(y1,y2,,yn)
    are systems of indeterminates and each
    zk
    is a linear form in y with coefficients in the rational function field
    k(x)
    over any field
    k
    of characteristic 0 or greater than d. These identities are higher degree analogue of the well-known composition formulas of sums of squares of Hurwitz, Radon and Pfister. We show that all but one such composition identities of sums of higher powers are trivial, i.e., r necessarily equals 1. Our proof is simple and elementary, in which the crux is Harrison’s center theory of homogeneous polynomials.

  • research-article
    Runju Wei, Leiye Xu, Xiaomin Zhou

    In this paper, we study the directional entropy along irrational directions in $\mathbb {R}^2$ and present the structure of directional Pinsker $\sigma $-algebra of $\mathbb {Z}^2$-MPSs.

  • research-article
    Lijun Bo, Tongqing Li

    We study a cooperative mean field game problem arising from the production control for multiple firms with price stickiness in the commodity market. The price dynamics for each firm is described as a controlled jump-diffusion process with mean-field interaction. Each firm aims to maximize the so-called social rewards which is defined by the average of individual rewards for all firms. By solving the limiting control problem for the representative firm and an associated fixed-point problem, we construct an explicit approximating optimal strategy when the number of firms grows large.

  • research-article
    Guanghui Wang, Long Feng, Ping Zhao

    Testing slope homogeneity is important in panel data modeling. Existing approaches typically take the summation over a sequence of test statistics that measure the heterogeneity of individual panels; they are referred to as Sum tests. We propose two procedures for slope homogeneity testing in large panel data models. One is called a Max test that takes the maximum over these individual test statistics. The other is referred to as a Combo test, which combines a certain Sum test (i.e., that of Pesaran and Yamagata in J Econom 142:50-93, 2008) and the proposed Max test together. We derive the limiting null distributions of the two test statistics, respectively, when both the number of individuals and temporal observations jointly diverge to infinity, and demonstrate that the Max test is asymptotically independent of the Sum test. Numerical results show that the proposed approaches perform satisfactorily.

  • research-article
    Duc Thoan Pham, Van Khien Tran, Thi Hong Nguyen

    In this paper, we show some vanishing theorems for harmonic p-forms on a locally conformally flat Riemannian manifold. In the concrete, provided that the integral of the traceless Ricci tensor has a suitable bound, we obtain a vanishing theorem for them without any scalar curvature conditions. Another theorem is also given under the condition on nonpositive scalar curvature, which improves and extends the ones previous.

  • research-article
    Qian Ni, Xuhui Wang

    When a parameterized probability density function is used to represent a landmark-based shape, the shape can be viewed as a point on the manifold that equips with a Riemannian metric corresponding to the mixture models. Hence, given two shapes parameterized by the same density model, the geodesic distance between them can be used for an appropriate shape distance measure. We provide a computational strategy, which is based on the cubic B-splines, to get geodesics and geodesic distances between plane shapes represented by the mixture of Gaussians. In contrast to the methods that discretize geodesic into a sequence of line segments, the proposed method is computationally efficient and numerically stable.

  • research-article
    Hejun Wang, Jiazu Zhou

    Lutwak et al. (Adv Math 329:85–132, 2018) introduced the $L_p$ dual curvature measure that unifies several other geometric measures in dual Brunn–Minkowski theory and Brunn–Minkowski theory. Motivated by works in Lutwak et al. (Adv Math 329:85–132, 2018), we consider the uniqueness and continuity of the solution to the $L_p$ dual Minkowski problem. To extend the important work (Theorem A) of LYZ to the case for general convex bodies, we establish some new Minkowski-type inequalities which are closely related to the optimization problem associated with the $L_p$ dual Minkowski problem. When $q< p$, the uniqueness of the solution to the $L_p$ dual Minkowski problem for general convex bodies is obtained. Moreover, we obtain the continuity of the solution to the $L_p$ dual Minkowski problem for convex bodies.

  • research-article
    Xiaosheng Lin, Dachun Yang, Sibei Yang, Wen Yuan

    Let

    (X,d,μ)
    be a doubling metric measure space in the sense of R. R. Coifman and G. Weiss, L a non-negative self-adjoint operator on
    L2(X)
    satisfying the Davies–Gaffney estimate, and
    X(X)
    a ball quasi-Banach function space on
    X
    satisfying some extra mild assumptions. In this article, the authors introduce the Hardy type space
    HX,L(X)
    by the Lusin area function associated with L and establish the atomic and the molecular characterizations of
    HX,L(X).
    As an application of these characterizations of
    HX,L(X)
    , the authors obtain the boundedness of spectral multiplies on
    HX,L(X)
    . Moreover, when L satisfies the Gaussian upper bound estimate, the authors further characterize
    HX,L(X)
    in terms of the Littlewood–Paley functions
    gL
    and
    gλ,L
    and establish the boundedness estimate of Schrödinger groups on
    HX,L(X)
    . Specific spaces
    X(X)
    to which these results can be applied include Lebesgue spaces, Orlicz spaces, weighted Lebesgue spaces, and variable Lebesgue spaces. This shows that the results obtained in the article have extensive generality.