Advanced Operator Algebra Research

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• MURAT ALTUNBULAK

Let M be a compact Stein surface with boundary.We show that M admits infinitely many pairwise nonequivalent positive allowable Lefschetz fibrations over D 2 with bounded fibers.

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• ÖZGÜR MARTİN

We obtain dimension free estimates for noncommutative Riesz transforms associated to conditionally negative length functions on group von Neumann algebras. This includes Poisson semigroups, beyond Bakry’s results in the commutative setting. Our proof is inspired by Pisier’s method and a new Khintchine inequality for c…

• SERAP ÖZTOP KAPTANOĞLU

For every integer g ≥ 2 there exist infinitely many pairwise nonhomeomorphic smooth 4-manifolds admitting genus-g Lefschetz fibration over S2 but not carrying any complex structure. This extends a recent result of Ozbagci and Stipsicz.

We promote the open-closed string map, originally formulated by Seiberg Witten, to a solution generating prescription in generalized supergravity. The approach hinges on a knowledge of an antisymmetric bivector $\mathrm{\ensuremath{\Theta}}$, built from antisymmetric products of Killing vectors, which is specified by…

• ÖZGÜR KELEKÇİ

Let M be a smooth 4-manifold which admits a Lefschetz fibration over D 2 or S 2 .We develop an algorithm to compute the signature of M using the global monodromy of this fibration.As a corollary we prove that there is no hyperelliptic Lefschetz fibration over S 2 with only reducible singular fibers.

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• MEHMET GÜRDAL

We describe explicit open books on arbitrary plumbings of oriented circle bundles over closed oriented surfaces. We show that, for a non-positive plumbing, the open book we construct is horizontal and the corresponding compatible contact structure is also horizontal and Stein fillable. In particular, on some Seifert f…

Continuing a line of research initiated by Larsen, Liu and Wang [12], Martin and Yap [13], Gürkanli [15], and influenced by Reiter′s presentation of Beurling and Segal algebras in Reiter [2,10] this paper presents the study of a family of Banach ideals of Beurling algebras , G a locally compact Abelian group. These sp…

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• UĞUR TIRNAKLI

Let K be a commutative ring with unit, R be a prime K-algebra with center Z(R), right Utumi quotient ring U and extended centroid C, and I a nonzero right ideal of R. Let g be a nonzero generalized derivation of R and f(X1,…,Xn) a multilinear polynomial over K. If g(f(x1,…,xn)) f(x1,…,xn) ∈ C for all x1,…,xn ∈ I, then…

• ÇAĞRI DEMİR