Estimation of Rock Characteristics Based on Polarization Spectra: Surface Roughness, Composition, and Density

Surface polarization characteristics provide crucial structural information of the Earth's surface. As two key elements of the natural geographical environment, rocks and soils play an important role in the study of surface processes. Inherent surface characteristics, such as surface roughness, composition, and density are critical parameters for the remote monitoring of land surfaces as they affect the polarization characteristics of scattered light waves. In this study, we investigated the relationship between surface roughness, composition, and density, and the polarization spectra of limestone-dolomite series rock. Results reveal a power function relationship between the surface roughness and the degree of polarization peaks among different detection zenith and azimuth angles. The depth and position of the absorbing waveband are significantly correlated with the characteristic component contents. The rock density was determined via the polarized reflection spectra, with the Earth's surface density calculations associated with a 2.6% divergence from the current recognized data. Our results demonstrate the ability of polarized spectra to retrieve surface roughness, composition, and density, with potential for further development in future work.

Polarized kilonovae from black hole–neutron star mergers

ABSTRACT We predict linear polarization for a radioactively powered kilonova following the merger of a black hole and a neutron star. Specifically, we perform 3D Monte Carlo radiative transfer simulations for two different models, both featuring a lanthanide-rich dynamical ejecta component from numerical-relativity simulations while only one including an additional lanthanide-free disc-wind component. We calculate polarization spectra for nine different orientations at 1.5, 2.5, and 3.5 d after the merger and in the $0.1\!-\!2\, \mu$m wavelength range. We find that both models are polarized at a detectable level 1.5 d after the merger while show negligible levels thereafter. The polarization spectra of the two models are significantly different. The model lacking a disc wind shows no polarization in the optical, while a signal increasing at longer wavelengths and reaching $\sim 1\!-\!6{{\ \rm per\ cent}}$ at $2\, \mu$m depending on the orientation. The model with a disc-wind component, instead, features a characteristic ‘double-peak’ polarization spectrum with one peak in the optical and the other in the infrared. Polarimetric observations of future events will shed light on the debated neutron richness of the disc-wind component. The detection of optical polarization would unambiguously reveal the presence of a lanthanide-free disc-wind component, while polarization increasing from zero in the optical to a peak in the infrared would suggest a lanthanide-rich composition for the whole ejecta. Future polarimetric campaigns should prioritize observations in the first ∼48 h and in the $0.5\!-\!2\, \mu$m range, where polarization is strongest, but also explore shorter wavelengths/later times where no signal is expected from the kilonova and the interstellar polarization can be safely estimated.

Spin characterization of systematics in CMB surveys – a comprehensive formalism

ABSTRACT The CMB B-mode polarization signal – both the primordial gravitational wave signature and the signal sourced by lensing – is subject to many contaminants from systematic effects. Of particular concern are systematics that result in mixing of signals of different ‘spin’, particularly leakage from the much larger spin-0 intensity signal to the spin-2 polarization signal. We present a general formalism, which can be applied to arbitrary focal plane setups, that characterizes signals in terms of their spin. We provide general expressions to describe how spin-coupled signals observed by the detectors manifest at map-level, in the harmonic domain, and in the power spectra, focusing on the polarization spectra – the signals of interest for upcoming CMB surveys. We demonstrate the presence of a previously unidentified cross-term between the systematic and the intrinsic sky signal in the power spectrum, which in some cases can be the dominant source of contamination. The formalism is not restricted to intensity to polarization leakage but provides a complete elucidation of all leakage including polarization mixing, and applies to both full and partial (masked) sky surveys, thus covering space-based, balloon-borne, and ground-based experiments. Using a pair-differenced setup, we demonstrate the formalism by using it to completely characterize the effects of differential gain and pointing systematics, incorporating both intensity leakage and polarization mixing. We validate our results with full time ordered data simulations. Finally, we show in an Appendix that an extension of simple binning map-making to include additional spin information is capable of removing spin-coupled systematics during the map-making process.

The large-scale magnetic field of Proxima Centauri near activity maximum

ABSTRACT We report the detection of a large-scale magnetic field at the surface of the slowly rotating fully convective (FC) M dwarf Proxima Centauri. 10 circular polarization spectra, collected from 2017 April to July with the HARPS-Pol spectropolarimeter, exhibit rotationally modulated Zeeman signatures suggesting a stellar rotation period of 89.8 ± 4.0 d. Using Zeeman–Doppler Imaging, we invert the circular polarization spectra into a surface distribution of the large-scale magnetic field. We find that Proxima Cen hosts a large-scale magnetic field of typical strength 200 G, whose topology is mainly poloidal, and moderately axisymmetric, featuring, in particular, a dipole component of 135 G tilted at 51° to the rotation axis. The large-scale magnetic flux is roughly 3× smaller than the flux measured from the Zeeman broadening of unpolarized lines, which suggests that the underlying dynamo is efficient at generating a magnetic field at the largest spatial scales. Our observations occur ∼1 yr after the maximum of the reported 7 yr-activity cycle of Proxima Cen, which opens the door for the first long-term study of how the large-scale field evolves with the magnetic cycle in an FC very low mass star. Finally, we find that Proxima Cen’s habitable zone planet, Proxima-b, is likely orbiting outside the Alfvèn surface, where no direct magnetic star–planet interactions occur.

The evidence for a spatially flat Universe

ABSTRACT We use a new and statistically powerful Planck likelihood to show that the Planck temperature and polarization spectra are consistent with a spatially flat Universe, in contrast to recent claims in the literature. When combined with other astrophysical data, particularly geometrical measurements of baryon acoustic oscillations, our likelihood constrains the Universe to be spatially flat to extremely high precision. We deduce a curvature density parameter ΩK = 0.0004 ± 0.0018 in good agreement with the 2018 results of the Planck team. In the context of inflationary cosmology, the observations offer strong support for models of inflation with a large number of e-foldings and disfavour models of incomplete inflation.

Качественный анализ вин и виноматериалов методами поляризованно-люминесцентной голографии на основе использования их оптических поляризационных спектров

The article describes the qualitative analysis of wines and wine products using polarization-luminescent holography methods. Identification and classification of wines is carried out on the basis of combined processing of various types of polarization spectra of multiplex reflective luminescent holograms of Denisyuk, obtained from the analyzed samples of the wine products (specific brands of wine). The following types of optical spectra of dynamic holograms were selected for analysis: 1) spectral intensity distribution of polarized luminescence (parameter-I); 2) the spectral distribution of the degree of anisotropy of luminescence (parameter-r) and - the ellipticity coefficient (Ce parameter) of the luminescence of the reconstructed virtual image of an object (object beam). An experimental study has been performed of the polarization properties of a reflective hologram Denisyuk, obtained in a luminescent photoanisotropic-gyrotropic material using a linearly polarized coherent light source. The dependence of the polarization state of the reconstructed image on the polarization of the recovering beam (polarization-holographic memory) is observed.An experiment is described on the investigation of samples, conducted to verify the possibility of using polarization spectra for identification of wine. Not individual fragments of the spectra are processed, as when using scalar spectroscopy methods and vector spectra as a whole, which increases the information content and reliability of the analysis. The results presented in the article can serve as the basis for creating guidelines, using spectral-holographic “portrait” of specific brands of wine, according to the set of characteristic features. This will allow revealing the authenticity of wine products, including such properties as variety composition of the annual harvest.

Поляризационно-чувствительные регистрирующие среды для голографии на базе красителя--флуорофора lucifer yellow

Polarization-sensitive hologram media based on matrices of polyvinyl pyrrolidone and gelatin are created, containing Lucifer Yellow and Coummarine 466. A multiplexed dynamic hologram of Denisyuk is recorded in a luminescent photoanisotropic gyrotropic material, using linearly polarized radiation of the laser LSR 405 NL-50 (= 405 nm). Using the method of polarization-luminescent holography, the photoanisotropic characteristics of the beam have been measured corresponding to the reconstructed imaginary image of the object field. The polarization spectra and photoluminescence intensity spectra of the reconstructed image were measured, depending on the composition of the recording medium. The possibility of multiplex recording has been demonstrated, as well as simultaneous observation of several images of an anisotropic-gyrotropic object encoded by different emission frequencies and / or polarization state. The combination of non-destructive polarization-luminescent holographic measurement method with other luminescent spectroscopic methods significantly expands the scope of this application by increasing dramatically the overall information content of the study.