Well known results related to the compactness of Hankel operators of one complex variable are extended to little Hankel operators of two complex variables. Critical to these considerations is the result of Ferguson and Lacey [5] characterizing the boundedness of the little Hankel operators in terms of the product BMO of S.-Y. Chang and R. Fefferman [2,3].

We prove that the theorem of Egorov, on the canonical transformation of symbols of pseudodifferential operators conjugated by Fourier integral operators, can be sharpened. The main result is that the statement of Egorov’s theorem remains true if, instead of just considering the principal symbols in S/S for the pseudodifferential operators, one uses refined principal symbols in S/S, which for cl...

We study different approaches for decision making with linguistic information. We describe some basic linguistic aggregation operators. We then analyze the problem of linguistic decision making with Dempster-Shafer (D-S) belief structure. We suggest the use of different types of linguistic aggregation operators in the D-S framework such as the linguistic ordered weighted averaging (LOWA) operat...

String equations for the vertex operators of type IIB on AdS3×S 3 background with NS-NS flux are calculated using Berkovits-Vafa-Witten formalism. With suitable field definitions, the linearized field equations for six-dimensional supergravity and a tensor multiplet on AdS3 × S 3 are recovered from these. We also discuss the massless degrees of freedom that survive the S3 Kaluza-Klein compactif...

We study the basic Galois connection induced by the ”satisfaction” relation between external functions An → B defined on a set A and valued in a possibly different set B, and ordered pairs (R, S) of relations R ⊆ Am and S ⊆ Bm, called relational constraints. We represent the induced Galois operators as compositions of closure operators associated with necessary and sufficient conditions describ...

We analyze under which conditions the missing label problem associated to a reduction chain s ⊂ s of (simple) Lie algebras can be completely solved by means of an Inönü-Wigner contraction g naturally related to the embedding. This provides a new interpretation of the missing label operators in terms of the Casimir operators of the contracted algebra, and shows that the available labeling operat...

Let G be a semigroup of commuting linear operators on a linear space S with the group operation of composition. The solvability of the system of equations /,/ = ,■, i = I, ... , r, where /, e G and j e S , was considered by Dahmen and Micchelli in their studies of the dimension of the kernel space of certain linear operators. The compatibility conditions Ijfr = Irfj , i ^ j , are necessar...

Lecomte and Ovsienko constructed SLn+1(R)-equivariant quantization maps Qλ for symbols of differential operators on λ-densities on RP . We derive some formulas for the associated graded equivariant star products ⋆λ on the symbol algebra Pol(T ∗RP). These give some measure of the failure of locality. Our main result expresses (for n odd) the coefficients Cp(·, ·) of ⋆λ when λ = 1 2 in terms of s...