1,720,976 research outputs found

    Hessian determinants as elements of dual Sobolev spaces

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    We present new integral formulas for the Hessian determinant. We use them for new definitions of Hessian under minimal regularity assumptions. The Hessian becomes a continuous linear functional on a Sobolev space

    Regularity result for nondivergence equations with unbounded coefficients

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    The aim of this paper is to establish a higher integrability result for the second derivatives of solutions to nondivergence elliptic equations of the type i,j=1naij(x)2uxixj=h\sum_{i,j=1}^n a_{ij}(x) \frac{\partial^2 u}{\partial x_i \partial x_j}=h. The matrix coefficient A(x)=[aij(x)]i,jA(x)=[a_{ij}(x)]_{i,j} is assumed to belong to the space BMOBMO

    New bounds for AinftyA_{infty} weights

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    Two new constants G1~(u)\tilde{G_1}(u) and A~(u)\tilde{A_{\infty}}(u) are studied for weights u:Rn[0,)u: \mathbb R^n \rightarrow [0,\infty), which are simultaneously finite exactly for AA_{\infty} weights. The special case v=hv=h', w=(h1)w=(h^{-1})' where h:RRh : \mathbb R \rightarrow \mathbb R is an increasing homeomorphism induces the identity A~(w)=G1~(v)\tilde{A_{\infty}}(w)=\tilde{G_1}(v). Other identities are established for such constants, when different measures are involved

    A higher integrability result for nondivergence elliptic equations

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    The aim of this paper is to establish a higher integrability result of the second derivatives of solutions for nondivergence elliptic equations of the type i,j=1naij2uxixj=h\sum_{i,j=1}^n a_{ij} \frac{\partial^2 u}{\partial x_i \partial x_j}=h. We assume that the coefficients aija_{ij} are bounded and have small BMO-norm

    New bounds for AinftyA_{infty} weights

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    Two new constants G1~(u)\tilde{G_1}(u) and A~(u)\tilde{A_{\infty}}(u) are studied for weights u:Rn[0,)u: \mathbb R^n \rightarrow [0,\infty), which are simultaneously finite exactly for AA_{\infty} weights. The special case v=hv=h', w=(h1)w=(h^{-1})' where h:RRh : \mathbb R \rightarrow \mathbb R is an increasing homeomorphism induces the identity A~(w)=G1~(v)\tilde{A_{\infty}}(w)=\tilde{G_1}(v). Other identities are established for such constants, when different measures are involved

    Nondivergence elliptic equations with unbounded coefficients

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    We study the nonvariational equation i,j=1naij(x)2uxixj=f \sum_{i,j=1}^n a_{ij}(x)\,\frac{\partial^2 u}{\partial x_i\,\partial x_j}=f in domains of \reale^n. We assume that the coefficients aija_{ij} are in BMOBMO and the equation is elliptic, but not uniformly, and consider ff in L^2(\reale^n), or even in the Zygmund class L^2\log^\alpha L(\reale^n). We also solve Dirichlet problem
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