arXiv subjects
Publications and source records attributed to Serap Öztop.
We establish continuity and Schatten-von Neumann properties for Fourier integral operators with amplitudes in Orlicz modulation spaces, when acting on other Orlicz modulation spaces themselves. The phase functions are non smooth and admit second order derivatives in suitable classes of modulation spaces.
We deduce continuity, compactness and invariance properties for quasi-Banach Orlicz modulation spaces. We characterize such spaces in terms of Gabor expansions and by their images under the Bargmann transform.
Let $G$ be a locally compact group, $w$ be a weight on $G$ and $Φ$ be a Young function. We give some characterizations for translation operators to be topologically transitive and chaotic on the weighted Orlicz space $L_w^Φ(G)$. In particular, transitivity is equivalent to the blow-up/collapse property in our case. Moreover, the dense set of periodic elements implies transitivity automatically.
Let G be a locally compact group, let $Ω:G\times G\to \mathbb{C}$ be a 2-cocycle, and let ($Φ$,$Ψ$) be a complementary pair of strictly increasing continuous Young functions. It is shown in \cite{OS2} that $(L^Φ(G),\circledast)$ becomes an Arens regular dual Banach algebra if \begin{align}\label{Eq:2-cocycle bdd sum-abstract} |Ω(s,t)|\leq u(s)+v(t) \ \ \ (s,t\in G) \end{align} for some $u,v\in \mathcal{S}^Ψ(G)$. We prove if $L^Φ(G)\subseteq L^2(G)$ and $u,v$ can be chosen to belong to $L^2(G)$, then $(L^Φ(G),\circledast)$ with the maximal operator space structure is completely isomorphic to an operator algebra. We also present further classes of 2-cocycles for which one could obtain such algebras generalizing in part the results of \cite{OS1}. We apply our methods to compactly generated group of polynomial growth and demonstrate that our results could be applied to variety of cases.
Let G be a locally compact abelian group, $ω:G\to (0,\infty)$ be a weight, and ($Φ$,$Ψ$) be a complementary pair of strictly increasing continuous Young functions. We show that for the weighted Orlicz algebra $L^Φ_ω(G)$, the weak amenability is obtained under conditions similar to the one considered by Y. Zhang for weighted group algebras. Our methods can be applied to various families of weighted Orlicz algebras, including weighted $L^p$-spaces.
Let G be a locally compact group, let $Ω:G\times G\to \mathbb{C}^*$ be a 2-cocycle, and let $Φ$ be a Young function. In this paper, we consider the Orlicz space $L^Φ(G)$ and investigate its algebraic property under the twisted convolution $\circledast$ coming from $Ω$. We find sufficient conditions under which $(L^Φ(G),\circledast)$ becomes a Banach algebra or a Banach $*$-algebra; we call it a {\it twisted Orlicz algebra}. Furthermore, we study its harmonic analysis properties, such as symmetry, existence of functional calculus, regularity, and having Wiener property, mostly for the case when $G$ is a compactly generated group of polynomial growth. We apply our methods to several important classes of polynomial as well as subexponential weights and demonstrate that our results could be applied to variety of cases.
Let G be a locally compact group, let $Ω:G\times G\to \mathbb{C}^*$ be a 2-cocycle, and let ($Φ$,$Ψ$) be a complementary pair of strictly increasing continuous Young functions. We continue our investigation of the algebraic properties of the Orlicz space $L^Φ(G)$ with respect to the twisted convolution $\circledast$ coming from $Ω$. We show that the twisted Orlicz algebra $(L^Φ(G),\circledast)$ posses a bounded approximate identity if and only if it is unital if and only if $G$ is discrete. On the other hand, under suitable condition on $Ω$, $(L^Φ(G),\circledast)$ becomes an Arens regular, dual Banach algebra. We also look into certain cohomological properties of $(L^Φ(G),\circledast)$, namely amenability and Connes-amenability, and show that they rarely happen. We apply our methods to compactly generated group of polynomial growth and demonstrate that our results could be applied to variety of cases.
We consider the minimal boundedly-translation-invariant Segal algebra $S_0^p(G)$ in the Figà-Talamanca--Herz algebra $A_p(G)$ of a locally compact group $G$. In the case that $p=2$ and $G$ is abelian this is the classical Segal algebra of Feichtinger. Hence we call this the Feichtinger--Figà-Talamanca--Herz Segal algebra of $G$. Remarkably, this space is also a Segal algebra in $L^1(G)$ and is, in fact, the minimal such algebra which is closed under pointwise multiplication by $\apg$. Even for $p=2$, this result is new for non-abelian $G$. We place a $p$-operator space structure on $S_0^p(G)$, and demonstrate the naturality of this by showing that it satisfies all natural functiorial properties: projective tensor products, restriction to subgroups and averaging over normal subgroups. However, due to complications arising within the theory of $p$-operator spaces, we are forced to work with weakly completely bounded maps in many of our results.