Let A and B be two factor von Neumann algebras. In this paper, we proved that a bijective mapping Φ:A→B satisfies Φ(a∘b+ba∗)=Φ(a)∘Φ(b)+Φ(b)Φ(a)∗ (where ∘ is the special Jordan product on B, respectively), for all elements a,b∈A, if only Φ ∗-ring isomorphism. particular, algebras are type I factors, then unitary isomorphism or conjugate

Multivariate quasi-projection operators Qj(f,φ,φ˜), associated with a function φ and distribution/function φ˜, are considered. The is supposed to satisfy the Strang-Fix conditions compatibility condition φ˜. Using technique based on Fourier multipliers, we study approximation properties of such for functions f from anisotropic Besov spaces Lp 1≤p≤∞. In particular, upper lower estimates Lp-error...

Let h≥2 and let A=(A1,…,Ah) be an h-tuple of sets integers. For nonzero integers c1,…,ch, consider the linear form φ=c1x1+c2x2+⋯+chxh. The representation function RA,φ(n) counts number h-tuples (a1,…,ah)∈A1×⋯×Ah such that φ(a1,…,ah)=n. A is a φ-Sidon system multiplicity g if RA,φ(n)≤g for all n∈Z. every positive integer g, Fφ,g(n) denote largest q there exists withAi⊆[1,n]and|Ai|=q i=1,…,h. It ...