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TienSon PHAM(sonptdlu.edu.vn) Abstract: Consider a semialgebraic function $f\colon\mathbb{R}^n \to {\mathbb{R}},$ which is continuous around a point $\bar{x} \in \mathbb{R}^n.$ Using the socalled {\em tangency variety} of $f$ at $\bar{x},$ we first provide necessary and sufficient conditions for $\bar{x}$ to be a local minimizer of $f,$ and then in the case where $\bar{x}$ is an isolated local minimizer of $f,$ we define a ``tangency exponent'' $\alpha_* > 0$ so that for any $\alpha \in \mathbb{R}$ the following four conditions are always equivalent: (i) the inequality $\alpha \ge \alpha_*$ holds; (ii) the point $\bar{x}$ is an $\alpha$order sharp local minimizer of $f;$ (iii) the limiting subdifferential $\partial f$ of $f$ is $(\alpha  1)$order strongly metrically subregular at $\bar{x}$ for $0;$ and (iv) the function $f$ satisfies the \L ojaseiwcz gradient inequality at $\bar{x}$ with the exponent $1  \frac{1}{\alpha}.$ Besides, we also present a counterexample to a conjecture posed by Drusvyatskiy and Ioffe in [Math. Program. Ser. A, 153(2):635653, 2015]. Keywords: Local minimizers, \L ojasiewicz gradient inequality, Optimality conditions, Semialgebraic, Sharp minimality, Strong metric subregularity, Tangencies Category 1: Nonlinear Optimization (Unconstrained Optimization ) Category 2: Convex and Nonsmooth Optimization (Nonsmooth Optimization ) Citation: Download: [PDF] Entry Submitted: 01/07/2019 Modify/Update this entry  
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