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A proof of the reverse isoperimetric inequality using a geometric-analytic approach
No full textWe present the first proof of the reverse isoperimetric inequality for black holes in arbitrary dimension using a two-pronged geometric-analytic approach. The proof holds for compact Riemannian hypersurfaces in AdS space and seems to be a generic property of black holes in the extended phase space formalism. Using Euclidean gravitational action, we show that, among all hypersurfaces of given volume, the round sphere in the -dimensional Anti-de Sitter space maximizes the area (and hence the entropy). This analytic result is supported by a geometric argument in a decomposition of spacetime: gravitational focusing enforces a strictly negative conformal deformation, and the Sherif–Dunsby rigidity theorem then forces the deformed 3-sphere to be isometric to round 3-sphere, establishing the round sphere as the extremal surface, in fact, a maximally entropic surface. Our work establishes that the reversal of the usual isoperimetric inequality occurs due to the structure of curved background governed by Einstein's equation, underscoring the role of gravity in the reverse isoperimetric inequality for black hole horizons in AdS space
Creation of a flat universe-antiuniverse pair from nothing
No full textIn this letter, we show that a universe-antiuniverse (U/AU) pair with zero spatial curvature (k = 0), consistent with observations, can emerge from “nothing”. This provides a novel approach towards the creation of the universe other than Vilenkin's tunnelling and Hartle-Hawking no-boundary proposal. The idea discussed in the paper can solve problems associated with these two proposals, namely scalar perturbations (Vilenkin) and a small number of inflationary e-folds (Hartle-Hawking). We also discuss various cosmological implications of this idea
Dual-Functional Gold Nanoparticles for Plasmon-Enhanced Photothermal Reductive Amination of Aldehydes
No full textWe demonstrate plasmon-mediated reductive amination of aldehydes, utilizing gold nanoparticles (AuNPs) that serve a dual role: enabling efficient hydride transfer to the imine intermediate via Si–H bond activation and providing a localized heat source to enhance the catalytic process. Notably, reaction conversions of 94 and 89% were achieved when using light-emitting diode (LED) light and sunlight, respectively, underscoring the potential for practical applications. Furthermore, the efficacy of this method is also highlighted in the efficient reduction of biomass-derived aldehydes
A district-level flood severity index for flood management in India
No full textIndia is one of the worst affected countries in the world in terms of fatalities and economic damage due to natural disasters, particularly floods. For planning flood mitigating and relief measures, granular historical information on a pan-India basis is required, which has been missing. Through recent efforts, a few national scale datasets have been created, but they lack the requisite information on fatalities and damages, which has limited the ability to develop a flood severity index. This paper describes the development of the India Flood Inventory with Impacts (IFI-Impacts) database, which contains death and damage statistics, and combines population and historically flooded area information sourced from a national hydrologic-hydrodynamic modeling system. We also propose a novel District Flood Severity Index (DFSI), which accounts for the historical severity of floods in India based on the number of people they have affected and the spread and duration of such floods. Districts being the administrative units of the government, this novel index fulfills a major need and gap in currently available flood management tools. The dataset as well as the index is expected to significantly advance disaster preparedness towards floods in the country. DFSI can be improved further by collecting and incorporating additional variables, e.g., economic losses and by improving the reliability/robustness of the data of other variables. Based on DFSI, actions need to be addressed to mitigate flood damages, beginning with the districts with the high DFSI values
Solution representation formula and Hopf lemma to Pucci’s equation
No full textAbstract.: We establish the existence of a viscosity subsolution along with its representation formula to the equation involving Pucci’s extremal operator (Formula presented.) with zero-th order term. We use a method based on a dynamic programming principle presented by Denis et-al. (Potential Analysis, 34(2), (2010), 139–161). As an application of our solution representation formula, we prove the Hopf lemma for (Formula presented.) with zero-th order term. Our approach is based on stochastic calculus and probabilistic methods
Smart Hybrid Energy Management System for Green Microgrid with Optimized Energy and Enhanced Voltage Stability
No full textEnergy management systems (EMSs) are an integral part of power networks with distributed energy resources (DERs) for optimized energy transactions. Conventional EMS performs rule-based actions for energy transactions between the DERs without considering optimization of resource and network stability. This paper proposes a smart hybrid EMS for an AC microgrid with optimal energy transactions with the utility distribution grid for improved cost-benefits along with stabilizing the voltage levels at the point of common coupling (PCC) using VAr compensation. The proposed EMS incorporates a hybrid scheme of rule based prioritization combined with an optimization module for energy management based on forecasted data of AC microgrid under grid-connected and islanded conditions. This reduces the operational cost of energy by at least 20% compared to classical EMS through a systematic cost-benefit analysis of microgrid. Besides, it aims at reduction of carbon emissions by at least 30% compared to classical EMS by prioritizing renewable energy sources and optimizing energy transfers. The proposed EMS not only ensures the active power management of a photovoltaic (PV) source, a battery energy storage system (BESS) and a diesel generator under different operating conditions but also performs VAr compensation using the grid-tied converters of PV and BESS which are dynamically limited by the EMS depending on the rated VA of the respective entities and the real-time active power injected. The simulation results from MATLAB/SIMULINK, analysis along with validation using the laboratory grid-tied converter prototype with PV source and battery setups establish the effectiveness of the proposed smart EMS
Observational study of the atmospheric gravity waves in the lower solar atmosphere
No full textThe solar chromosphere exhibits a variety of waves originating from the photosphere and deeper layers, causing oscillations at different heights with distinct frequencies. This study identifies and analyze Atmospheric Gravity Waves (AGWs) and acoustic waves at various height pairs within the solar atmosphere utilising Hα, Ca II IR and Fe I 6173 A imaging spectroscopic observations from Swedish 1m Solar Telescope. We study and compare oscillations by analyzing power maps generated using velocities obtained from the filtergram difference and bisector methods. Our analysis shows a consistent increase in power with height in the solar chromosphere for both methods. In addition to this, our results show that AGWs are detected within or near magnetic flux concentration regions, where spicules are also predominant, exhibiting significant power in the chromosphere. These regions also feature inclined magnetic fields, which might be contributing to the propagation of these low-frequency AGWs in the chromosphere. Examining average power maps at spicule locations reveals significant power at AGWs frequency across different chromospheric heights. We speculate that these AGWs propagate upward along spicular structures and were not previously detected in the studies employing space-time map due to their limited lifetime. This study provides insights into the complex dynamics of solar chromospheric waves influenced by magnetic field, contributing to our understanding of AGWs and acoustic waves propagation across different layers of the solar atmosphere
Visible light assisted oxidation of organic compounds by iridium(iii)dipyrrinato complexes
No full textPhoto-assisted oxidation of organic compounds is a greener and more sustainable approach, which utilizes a very small amount of photocatalyst and visible light or sunlight. Ir(iii) cyclometalated complexes have been explored extensively for photocatalytic applications in the past. Alternatively, Ir(iii)dipyrrinato complexes can be employed for photocatalysis as they have attractive optical properties with high singlet oxygen generation ability. An efficient protocol for the photocatalytic aerobic oxidation of amines and sulfides by utilizing only 0.05 mol% Ir(iii)dipyrrinato complexes is reported. The reactions are completed in 2 hours, providing imines and sulfoxides, in excellent yields. Additionally, a methodology for the hydroxylation of aryl boronic acids using 0.05 mol% Ir(iii)dipyrrinato catalyst is reported. These methods display excellent substrate tolerance and offer an effective strategy for synthesizing a diverse range of functionalized imines, sulfoxides and phenols in a highly efficient manner, which validates the versatility of Ir(iii)dipyrrinato complexes as photocatalysts for various organic transformations. Notably, these photochemical transformations require only a minimal catalyst loading of 0.05 mol% for these reactions, which demonstrates their exceptional cost-effectiveness