arXiv subjects

A. Varela

Publications and source records attributed to A. Varela.

3 recordsLinked to original sources

arXiv2023

Maximizing science return by coordinating the survey strategies of Roman with Rubin, and other major facilities

[Abridged] The Nancy Grace Roman Space Telescope will be one of several flagship survey facilities operating over the next decade starting $\sim$2025. The deep near-IR imaging that Roman will deliver will be highly complementary to the capabilities of other survey telescopes that will operate contemporaneously, particularly those that can provide data at different wavelengths and messengers, or different time intervals. Combining data from multiple facilities can provide important astrophysical insights, provided the data acquisition is carefully scheduled, and careful plans are made for appropriate joint data analyses. In this White Paper, we discuss the broad range of science that would be enabled by coordinating Roman observations of the Galactic Bulge with those of the Vera C. Rubin Observatory. Specifically, we discuss how Roman's characterization of lensing events caused by exoplanets, stellar systems and stellar remnants can be enhanced by data from Rubin. The same data will also be highly advantageous for the determination of stellar properties, and for distinguishing exoplanetary transits. It will enable more accurate period-color-luminosity relationships to be measured for RR~Lyrae throughout the Milky Way Bulge and Bar, probing galactic structure and dynamics. But we stress that this is only a sample of the full potential and advocate for a more complete study to be made as a joint effort between these major projects. We note that we do not suggest any changes beyond the established Science Requirements for the RGBTDS, in terms of survey footprint or filter selection.

astro-ph.IM↗

arXiv1999

Homotopy of state orbits

Let M be a von Neumann algebra, f a faithful normal state and denote by M^f the fixed point algebra of the modular group of f. Let U_M and U_{M^f} be the unitary groups of M and M^f. In this paper we study the quotient U_M/U_{M^f} endowed with two natural topologies: the one induced by the usual norm of M (called here usual topology), and the one induced by the pre-Hilbert C*-module norm given by the f-invariant conditional expectation E_f:M \to M^f (called the modular topology). It is shown that U_M/U_{M^f} is simply connected with the usual topology. Both topologies are compared, and it is shown that they coincide if and only if the Jones index of E_f is finite. The set U_M/U_{M^f} can be regarded as a model for the unitary orbit {f \circ Ad(u^*): u\in U_M} of f, and either with the usual or the modular it can be embedded continuously in the conjugate space M* (although not as a topological submanifold).

math.OA↗

arXiv1999

LAPW frozen-phonon calculation, shell model lattice dynamics and specific-heat measurement of SnO

An ab-initio Linear Augmented Plane-Wave (LAPW) calculation of the zone-centered phonon frequencies of SnO has been performed. E$_g$ symmetry has been ascribed to the mode observed at 113 cm$^{-1}$ in Raman measurements, discarding a previous B$_{1g}$ assignement. The other phonon modes measured by Raman spectroscopy are also well reproduced. A new shell-model has also been developed, that gives good agreement of the zone-centered frequencies compared to the measured data and the LAPW results. Specific heat measurements have been performed between 5 K and 110 K. Computation of the specific heat and the Mössbauer recoilless fraction with the improved shell-model shows a good agreement with the experimental data as a function of temperature.

cond-mat↗