arXiv subjects

J. Virtanen

Publications and source records attributed to J. Virtanen.

4 recordsLinked to original sources

arXiv2025

Composition and Volterra type operators on large Bergman spaces with rapidly decreasing weights

We characterize boundedness, compactness and Schatten class properties of generalized Volterra-type integral operators acting between large Bergman spaces $A_ω^p$ and $A_ω^q$ for $0 <p, q\leq \infty$. To prove our characterizations, which involve Berezin-type integral transforms, we use the Littlewood-Paley formula of Constantin and Peláez and corresponding embedding theorems. Our results generalize the work on integration operators of Pau and Peláez in J. Funct. Anal. 259 (2010), 2727--2756.

math.FA↗

arXiv2009

Structure, classifcation, and conformal symmetry, of elementary particles over non-archimedean space-time

It is known that no length or time measurements are possible in sub-Planckian regions of spacetime. The Volovich hypothesis postulates that the micro-geometry of spacetime may therefore be assumed to be non-archimedean. In this letter, the consequences of this hypothesis for the structure, classification, and conformal symmetry of elementary particles, when spacetime is a flat space over a non-archimedean field such as the $p$-adic numbers, is explored. Both the Poincaré and Galilean groups are treated. The results are based on a new variant of the Mackey machine for projective unitary representations of semidirect product groups which are locally compact and second countable. Conformal spacetime is constructed over $p$-adic fields and the impossibility of conformal symmetry of massive and eventually massive particles is proved.

math-ph↗

arXiv2008

(42355) Typhon-Echidna: Scheduling Observations for Binary Orbit Determination

We describe a strategy for scheduling astrometric observations to minimize the number required to determine the mutual orbits of binary transneptunian systems. The method is illustrated by application to Hubble Space Telescope observations of (42355) Typhon-Echidna, revealing that Typhon and Echidna orbit one another with a period of 18.971 +/- 0.006 days and a semimajor axis of 1628 +/- 29 km, implying a system mass of (9.49 +/- 0.52) x 10^17 kg. The eccentricity of the orbit is 0.526 +/- 0.015. Combined with a radiometric size determined from Spitzer Space Telescope data and the assumption that Typhon and Echidna both have the same albedo, we estimate that their radii are 76 +14/-16 and 42 +8/-9 km, respectively. These numbers give an average bulk density of only 0.44 +0.44/-0.17 g cm^-3, consistent with very low bulk densities recently reported for two other small transneptunian binaries.

astro-ph↗

arXiv2002

Microflaring of a solar Bright point

A solar X-ray Bright point (BP) was observed with the SUMER-spectrograph of the SOHO-observatory. The data consist of four far-UV spectral lines formed between 2 10^4 - 6 10^5 K, with 2 arcsec spatial, 2.8 min temporal and 4 km/s spectral resolution. A striking feature is the strong microflaring and appearance of several short lived transients. Using simultaneous magnetic field measurements the region observed seemed to lie above a cancelling flux region. With respect to the filling factor and emission measure this particular BP was similar to the average surface of a moderately active solar type star.

astro-ph↗