Asymptotic quasinormal frequencies of different spin fields in d-dimensional spherically-symmetric black holes

While Hod's conjecture is demonstrably restrictive, the link he observed between black hole (BH) area quantisation and the large overtone ($n$) limit of quasinormal frequencies (QNFs) motivated intense scrutiny of the regime, from which an improved understanding of asymptotic quasinormal frequencies (aQNFs) emerged. A further outcome was the development of the ``monodromy technique", which exploits an anti-Stokes line analysis to extract physical solutions from the complex plane. Here, we use the monodromy technique to validate extant aQNF expressions for perturbations of integer spin, and provide new results for the aQNFs of half-integer spins within higher-dimensional Schwarzschild, Reissner-Nordstr{\"o}m, and Schwarzschild (anti-)de Sitter BH spacetimes. Bar the Schwarzschild anti-de Sitter case, the spin-1/2 aQNFs are purely imaginary; the spin-3/2 aQNFs resemble spin-1/2 aQNFs in Schwarzschild and Schwarzschild de Sitter BHs, but match the gravitational perturbations for most others. Particularly for Schwarzschild, extremal Reissner-Nordstr{\"o}m, and several Schwarzschild de Sitter cases, the application of $n \rightarrow \infty$ generally fixes $\mathbb{R}e \{ \omega \}$ and allows for the unbounded growth of $\mathbb{I}m \{ \omega \}$ in fixed quantities.

Melanin diagnostics with nonlinear optics: a mini-review

Optical methods are widely used to perform fundamental studies of living systems and solve problems of biomedical diagnostics. Along with the classical spectroscopy, methods of nonlinear optics (e.g., multiphoton microscopy) are also applied in biophotonics. The potential of nonlinear optical methods for visualisation and analysis of the properties of endogenous chromophore molecules are considered in this minireview. Melanin - a pigment with specific spectral features of photophysical properties in the visible and near-IR ranges - is taken as an example. It is discussed what information about its localisation in tissues and structural organisation can be obtained by nonlinear optical methods: multiphoton fluorescence microscopy (including fluorescence lifetime imaging), third harmonic generation, pump - probe spectroscopy, and coherent anti- Stokes Raman spectroscopy.

Laser synthesis of nanocomposite hydrocarbon fuel and CARS diagnostics of its combustion flame

We report an analysis of diffusive combustion in oxygen of a composite fuel formed by the addition of aluminium nanoparticles (NPs) to isopropanol. The process of obtaining Al NPs consisted in laser fragmentation of initially large industrial NPs using radiation of a pulsed nanosecond neodymium laser. The size distribution of Al NPs was determined using a measuring disk centrifuge. The average nanoparticle size was 20 nm, which is confirmed by transmission electron microscopy data. A diagnostic system based on coherent anti-Stokes Raman scattering (CARS) was used to experimentally study the diffusive combustion of composite fuel. The temperature distributions were measured in two mutually orthogonal directions (along the flame and in the transverse direction) in pure isopropanol and in isopropanol with the addition of 0.15 wt % of Al nanoparticles.