BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Vjekoslav Kovac (University of Zagreb) DTSTART:20220502T190000Z DTEND:20220502T200000Z DTSTAMP:20260423T021334Z UID:paw/53 DESCRIPTION:Title: Low er bounds for the L^p norms of some Fourier multipliers\nby Vjekoslav Kovac (University of Zagreb) as part of Probability and Analysis Webinar\n \n\nAbstract\nQuite often we wonder about the sharpness of estimates for c ertain singular integral operators. In theory\, their sharpness can be con firmed by constructing extremizers or approximate extremizers\, but\, in p ractice\, such extremizers might not be obvious\, or they might be impossi bly complicated to work with. In this talk we will discuss a reasonably ge neral way of proving lower bounds for the exact $L^p$ norms of unimodular homogeneous Fourier multipliers. We will then apply it to solve three open problems: one by Iwaniec and Martin (from 1996) on the powers of the comp lex Riesz transform\, one by Maz'ya (traced back to the 1970s) on multipli ers with smooth phases\, and one by Dragičević\, Petermichl\, and Volber g (from 2006) on the two-dimensional Riesz group. This is joint work with Aleksandar Bulj\, Andrea Carbonaro\, and Oliver Dragičević.\n LOCATION:https://researchseminars.org/talk/paw/53/ END:VEVENT END:VCALENDAR