Massive vector fields on the Schwarzschild spacetime: quasinormal modes and bound states

We study the propagation of a massive vector or Proca field on the Schwarzschild spacetime. The field equations are reduced to a one-dimensional wave equation for the odd-parity part of the field and two coupled equations for the even-parity part of the field. We use numerical techniques based on solving (scalar or matrix-valued) three-term recurrence relations to compute the spectra of both quasi-normal modes and quasi-bound states, which have no massless analogue, complemented in the latter case by a forward-integration method. We study the radial equations analytically in both the near-horizon and far-field regions and use a matching procedure to compute the associated spectra in the small-mass limit. Finally, we comment on extending our results to the Kerr geometry and its phenomenological relevance for hidden photons arising e.g. in string theory compactifications.Comment: 15 pages, 8 figures; minor corrections, to be published in Phys. Rev.

Bound states of spin-half particles in a static gravitational field close to the black hole field

We consider the bound-state energy levels of a spin-1/2 fermion in the gravitational field of a near-black hole object. In the limit that the metric of the body becomes singular, all binding energies tend to the rest-mass energy (i.e. total energy approaches zero). We present calculations of the ground state energy for three specific interior metrics (Florides, Soffel and Schwarzschild) for which the spectrum collapses and becomes quasi-continuous in the singular metric limit. The lack of zero or negative energy states prior to this limit being reached prevents particle pair production occurring. Therefore, in contrast to the Coulomb case, no pairs are produced in the non-singular static metric. For the Florides and Soffel metrics the singularity occurs in the black hole limit, while for the Schwarzschild interior metric it corresponds to infinite pressure at the centre. The behaviour of the energy level spectrum is discussed in the context of the semi-classical approximation and using general properties of the metric.Comment: 16 pages, 6 Figures. Submitted to General Relativity and Gravitatio

Reconstruction of extended ureteral defects using sections of the ileum and colon

The incidence of extended ureteral strictures has been on the rise in the past decade. This increase is attributed to the growing number of endoscopic surgeries, expanded criteria for surgical treatment of cancer patients, and complications from radiation therapy. When correcting an extended ureteral stricture, if there is a lack of urinary system tissues to replace the defect or if they are involved in the pathological process, replacement reconstruction using a segment of small or large intestine becomes necessary. Options for ureteral reconstructions using ileum and colon sections were discussed, as well as the use of the appendix as a graft. Data on the effectiveness and frequency of postoperative complications were analysed, and the pros and cons of different surgical techniques for ureteroplasty were evaluated. It is necessary to conduct further scientific and practical research and evaluation of long-term results to solve the remaining unclear problems and to inform the doctors of our country about the existence of this pathology

Resonance and absorption spectra of the Schwarzschild black hole for massive scalar perturbations: a complex angular momentum analysis

We reexamine some aspects of scattering by a Schwarzschild black hole in the framework of complex angular momentum techniques. More precisely, we consider, for massive scalar perturbations, the high-energy behavior of the resonance spectrum and of the absorption cross section by emphasizing analytically the role of the mass. This is achieved (i) by deriving asymptotic expansions for the Regge poles of the $S$-matrix and then for the associated weakly damped quasinormal frequencies and (ii) by taking into account the analytic structure of the greybody factors which allows us to extract by resummation the physical information encoded in the absorption cross section.Comment: v2: Minor changes to match the published version. v3: Typos correcte

Optimal intestinal graft selection for reconstruction of extended ureteral stricture: an animal model study

Introduction. The prevalence of patients with extended ureteral strictures has been steadily increasing over the past decades. When it is not possible to perform reconstruction with the tissues of the urinary system, the best solution is intestinal replacement plasty. However, despite the great world experience, the search for the optimal method of intestinal reconstruction does not stop, which determines the relevance of conducting an experimental prospective study.Objective. To evaluate morphological changes in renal parenchyma after ureteral replacement reconstruction by segments of small and large intestine.Materials & methods. Fifteen white giant rabbits (6-months-old, weighing 5 kg) were divided into three groups. Group A (n = 5) underwent small intestine [ilealplasty] replacement plasty. Group B (n = 5) double-flap ileoplasty using the Yang-Monti technique. Group C (n = 5) – large intestine [coloplasy] ureteral reconstruction. Before the operation and before withdrawal from the experiment, the level of creatinine and electrolytes was assessed, kidney ultrasound was performed on days 2, 5, 10. Excretory urography was performed to assess the patency of the anastomoses. Animals were withdrawn from the experiment from day 10 to 30. The material used for morphological study included kidneys from the operated and intact sides, proximal and distal anastomoses.Results. No increase in creatinine level, metabolic disorders were detected in animals. According to ultrasound data, hydronephrosis developed in all animals on day 2 and remained unchanged during the entire follow-up. Group A: no complications were detected. Histologically, the renal parenchyma showed moderate signs of chronic inflammation, single foci of lymphoid infiltration, but there were no irreversible processes in the form of necrosis and sclerosis. Group B: complications — stricture in the anastomosis area of the detubularised fragments and necrosis of the small intestine due to compression of the mesentery by the graft vascular stem. Histologically there were marked dilatation of the tubules at all levels, enlargement of the Bowman-Shumlansky capsule, as well as signs of moderate inflammatory process, there were hydropic and hyaline-droplet dystrophy, tubular necrosis foci. Group C: complications — accumulation of a significant amount of grit, mucus, and fibrin in the colocystoanastomosis area. Histologically, the renal parenchyma showed a marked inflammatory process, in particular, purulent inflammation with demarcation zones, infiltration with polymorphonuclear leukocytes and bacterial cells, foci of necrosis and sclerosis of both stroma and tubules, dilatation of tubules and Bowman-Schumlansky capsules.Conclusion. The use of an unchanged ileal-graft reconstruction of an extended ureteral defect showed acceptable histological results in an animal model, which confirms the feasibility of its use in clinical practice. The absence of foci of necrosis and fibrosis in the renal parenchyma indicates the preserved functional potential, which suggests the stabilization of renal function in the long term

Warm-Start AlphaZero Self-Play Search Enhancements

Recently, AlphaZero has achieved landmark results in deep reinforcement learning, by providing a single self-play architecture that learned three different games at super human level. AlphaZero is a large and complicated system with many parameters, and success requires much compute power and fine-tuning. Reproducing results in other games is a challenge, and many researchers are looking for ways to improve results while reducing computational demands. AlphaZero's design is purely based on self-play and makes no use of labeled expert data ordomain specific enhancements; it is designed to learn from scratch. We propose a novel approach to deal with this cold-start problem by employing simple search enhancements at the beginning phase of self-play training, namely Rollout, Rapid Action Value Estimate (RAVE) and dynamically weighted combinations of these with the neural network, and Rolling Horizon Evolutionary Algorithms (RHEA). Our experiments indicate that most of these enhancements improve the performance of their baseline player in three different (small) board games, with especially RAVE based variants playing strongly

From Chalcogen Bonding to S–π Interactions in Hybrid Perovskite Photovoltaics

The stability of hybrid organic–inorganic halide perovskite semiconductors remains a significant obstacle to their application in photovoltaics. To this end, the use of low‐dimensional (LD) perovskites, which incorporate hydrophobic organic moieties, provides an effective strategy to improve their stability, yet often at the expense of their performance. To address this limitation, supramolecular engineering of noncovalent interactions between organic and inorganic components has shown potential by relying on hydrogen bonding and conventional van der Waals interactions. Here, the capacity to access novel LD perovskite structures that uniquely assemble through unorthodox S‐mediated interactions is explored by incorporating benzothiadiazole‐based moieties. The formation of S‐mediated LD structures is demonstrated, including one‐dimensional (1D) and layered two‐dimensional (2D) perovskite phases assembled via chalcogen bonding and S–π interactions, through a combination of techniques, such as single crystal and thin film X‐ray diffraction, as well as solid‐state NMR spectroscopy, complemented by molecular dynamics simulations, density functional theory calculations, and optoelectronic characterization, revealing superior conductivities of S‐mediated LD perovskites. The resulting materials are applied in n‐i‐p and p‐i‐n perovskite solar cells, demonstrating enhancements in performance and operational stability that reveal a versatile supramolecular strategy in photovoltaics

From Chalcogen Bonding to S–π Interactions in Hybrid Perovskite Photovoltaics

The stability of hybrid organic–inorganic halide perovskite semiconductors remains a significant obstacle to their application in photovoltaics. To this end, the use of low‐dimensional (LD) perovskites, which incorporate hydrophobic organic moieties, provides an effective strategy to improve their stability, yet often at the expense of their performance. To address this limitation, supramolecular engineering of noncovalent interactions between organic and inorganic components has shown potential by relying on hydrogen bonding and conventional van der Waals interactions. Here, the capacity to access novel LD perovskite structures that uniquely assemble through unorthodox S‐mediated interactions is explored by incorporating benzothiadiazole‐based moieties. The formation of S‐mediated LD structures is demonstrated, including one‐dimensional (1D) and layered two‐dimensional (2D) perovskite phases assembled via chalcogen bonding and S–π interactions, through a combination of techniques, such as single crystal and thin film X‐ray diffraction, as well as solid‐state NMR spectroscopy, complemented by molecular dynamics simulations, density functional theory calculations, and optoelectronic characterization, revealing superior conductivities of S‐mediated LD perovskites. The resulting materials are applied in n‐i‐p and p‐i‐n perovskite solar cells, demonstrating enhancements in performance and operational stability that reveal a versatile supramolecular strategy in photovoltaics

Global maps of the magnetic thickness and magnetization of the Earth’s lithosphere

International audienceWe have constructed global maps of the large-scale magnetic thickness and magnetization of Earth's lithosphere. Deriving such large-scale maps based on lithospheric magnetic field measurements faces the challenge of the masking effect of the core field. In this study, the maps were obtained through analyses in the spectral domain by means of a new regional spatial power spectrum based on the Revised Spherical Cap Harmonic Analysis (R-SCHA) formalism. A series of regional spectral analyses were conducted covering the entire Earth. The R-SCHA surface power spectrum for each region was estimated using the NGDC-720 spherical harmonic (SH) model of the lithospheric magnetic field, which is based on satellite, aeromagnetic, and marine measurements. These observational regional spectra were fitted to a recently proposed statistical expression of the power spectrum of Earth's lithospheric magnetic field, whose free parameters include the thickness and magnetization of the magnetic sources. The resulting global magnetic thickness map is compared to other crustal and magnetic thickness maps based upon different geophysical data. We conclude that the large-scale magnetic thickness of the lithosphere is on average confined to a layer that does not exceed the Moho