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1.
We study automorphisms of the Hilbert scheme of n points on a generic projective K3 surface S, for any . We show that is either trivial or generated by a non‐symplectic involution and we determine numerical and divisorial conditions which allow us to distinguish between the two cases. As an application of these results we prove that, for any , there exist infinitely many admissible degrees for the polarization of the K3 surface S such that admits a non‐natural involution. This provides a generalization of the results of [7] for .  相似文献   
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We study quasilinear concave operators on Banach spaces with partial ordering. Additional assumption which makes comparison principles applicable is that Frechet derivative of a (smooth) non-linear part is a generator of a positive semigroup. Stable solutions are introduced for stationary problem and it is proved that they are attractors to the solutions of an evolution problem. Under stronger assumptions about spaces and operators we prove also the existence of the stable solutions.  相似文献   
4.
Guangjun Zhu 《代数通讯》2013,41(11):4120-4131
Let (R,𝔪) be a Cohen–Macaulay local ring of dimension d > 0, I an 𝔪-primary ideal of R, and K an ideal containing I. When depth G(I) ≥ d ? 1, depth FK(I) ≥ d ? 2, and r(I|K) < ∞, we calculate the fiber coefficients fi(I). Under the above assumptions on depth G(I) and r(I|K), we give an upper bound for f1(I), and also provide a characterization, in terms of f1(I), of the condition depth FK(I) ≥ d ? 2.  相似文献   
5.
In this paper,we study a Dirichlet-type boundary value problem(BVP) of nonlinear fractional differential equation with an order α∈(3,4],where the fractional derivative Dαo+is the standard Riemann-Liouville fractional derivative.By constructing the Green function and investigating its properties,we obtain some criteria for the existence of one positive solution and two positive solutions for the above BVP.The Krasnosel’skii fixedpoint theorem in cones is used here.We also give an example to illustrate the applicability of our results.  相似文献   
6.
We investigate the existence of positive solutions to the singular fractional boundary value problem: $^c\hspace{-1.0pt}D^{\alpha }u +f(t,u,u^{\prime },^c\hspace{-2.0pt}D^{\mu }u)=0$, u′(0) = 0, u(1) = 0, where 1 < α < 2, 0 < μ < 1, f is a Lq‐Carathéodory function, $q > \frac{1}{\alpha -1}$, and f(t, x, y, z) may be singular at the value 0 of its space variables x, y, z. Here $^c \hspace{-1.0pt}D$ stands for the Caputo fractional derivative. The results are based on combining regularization and sequential techniques with a fixed point theorem on cones.  相似文献   
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F. Lara 《Optimization》2017,66(8):1259-1272
In this paper, we use generalized asymptotic functions and second-order asymptotic cones to develop a general existence result for the nonemptiness of the proper efficient solution set and a sufficient condition for the domination property in nonconvex multiobjective optimization problems. A new necessary condition for a point to be efficient or weakly efficient solution is given without any convexity assumption. We also provide a finer outer estimate for the asymptotic cone of the weakly efficient solution set in the quasiconvex case. Finally, we apply our results to the linear fractional multiobjective optimization problem.  相似文献   
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Given a set of polyhedral cones C1,…,CkRd, and a convex set D, does the union of these cones cover the set D? In this paper we consider the computational complexity of this problem for various cases such as whether the cones are defined by extreme rays or facets, and whether D is the entire Rd or a given linear subspace Rt. As a consequence, we show that it is coNP-complete to decide if the union of a given set of convex polytopes is convex, thus answering a question of Bemporad, Fukuda and Torrisi.  相似文献   
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