Existence of positive ground state solutions of critical nonlinear Klein-Gordon-Maxwell systems

In this paper we study the following nonlinear Klein–Gordon–Maxwell system −∆u + [m2 0 − (ω + φ) 2 ]u = f(u) in R3 ∆φ = (ω + φ)u in R3 where 0 < ω < m0. Based on an abstract critical point theorem established by Jeanjean, the existence of positive ground state solutions is proved, when the nonlinear term f(u) exhibits linear near zero and a general critical growth near infinity. Compared with other recent literature, some different arguments have been introduced and some results are extended

RSA: Byzantine-Robust Stochastic Aggregation Methods for Distributed Learning from Heterogeneous Datasets

In this paper, we propose a class of robust stochastic subgradient methods for distributed learning from heterogeneous datasets at presence of an unknown number of Byzantine workers. The Byzantine workers, during the learning process, may send arbitrary incorrect messages to the master due to data corruptions, communication failures or malicious attacks, and consequently bias the learned model. The key to the proposed methods is a regularization term incorporated with the objective function so as to robustify the learning task and mitigate the negative effects of Byzantine attacks. The resultant subgradient-based algorithms are termed Byzantine-Robust Stochastic Aggregation methods, justifying our acronym RSA used henceforth. In contrast to most of the existing algorithms, RSA does not rely on the assumption that the data are independent and identically distributed (i.i.d.) on the workers, and hence fits for a wider class of applications. Theoretically, we show that: i) RSA converges to a near-optimal solution with the learning error dependent on the number of Byzantine workers; ii) the convergence rate of RSA under Byzantine attacks is the same as that of the stochastic gradient descent method, which is free of Byzantine attacks. Numerically, experiments on real dataset corroborate the competitive performance of RSA and a complexity reduction compared to the state-of-the-art alternatives.Comment: To appear in AAAI 201

catena-Poly[dipropyl­ammonium [[bis­(benzotriazolato-κN 1)zinc(II)]-μ-benzotriazolato-κ2 N 1:N 3]]

In the title compound, {(C6H16N)[Zn(C6H4N3)3]}n, the ZnII atom has a distorted tetra­hedral geometry defined by four N atoms from four benzotriazolate (BTA) ligands. The compound is composed of extended polymeric chains in which two BTA N atoms bridge [Zn(BTA)2] fragments along [001]. Cations and anions are linked by N—H⋯N hydrogen-bond inter­actions along [010]