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Divyang Bhimani

Publications and source records attributed to Divyang Bhimani.

4 recordsLinked to original sources
arXiv2023

Factorizations for quasi-Banach time-frequency spaces and Schatten classes

We deduce factorization properties for a quasi-Banach module over a quasi-Banach algebra. Especially we extend a result by Hewitt and prove that if any such algebra which possess a bounded left approximate identity, then any element in the module can be factorized. As applications, we deduce factorization properties for Wiener amalgam spaces, for an extended family of modulation spaces and for Schatten symbol classes in pseudo-differential calculus under multiplications like convolutions, twisted convolutions and symbolic products. For example we show for Wiener amalgam spaces that WL^{1,r}*WL^{p,q}=WL^{p,q} when r in (0,1], and p and q are finite and larger than r. In particular we improve Rudin's identity L^1*L^1=L^1.

math.FA↗
arXiv2022

Normalized solutions to nonlinear Schr\"odinger equations with competing Hartree-type nonlinearities

In this paper, we consider solutions to the following nonlinear Schr\"odinger equation with competing Hartree-type nonlinearities, $$ -\Delta u + \lambda u=\left(|x|^{-\gamma_1} \ast |u|^2\right) u - \left(|x|^{-\gamma_2} \ast |u|^2\right) u\quad \mbox{in} \,\, \R^N, $$ under the $L^2$-norm constraint $$ \int_{\R^N} |u|^2 \, dx=c>0, $$ where $N \geq 1$, $0<\gamma_2 < \gamma_1 <\min\{N, 4\}$ and $\lambda \in \R$ appearing as Lagrange multiplier is unknown. First we establish the existence of ground states in the mass subcritical, critical and supercritical cases. Then we consider the well-posedness and dynamical behaviors of solutions to the Cauchy problem for the associated time-dependent equations.

math.AP↗
arXiv2021

Fractional Fourier transforms, harmonic oscillator propagators and Strichartz estimates on Pilipovic and modulation spaces

We show that harmonic oscillator propagators and fractional Fourier transforms are essentially the same. We deduce continuity properties and fix time estimates for such operators on modulation spaces, and apply the results to prove Strichartz estimates for the harmonic oscillator propagator when acting on modulation spaces. Especially we extend some results by Balhara, Cordero, Nicola, Rodino and Thangavelu. We also show that general forms of fractional harmonic oscillator propagators are continuous on suitable Pilipovic spaces.

math.FA↗