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Quantum effects on the black hole shadow and deflection angle in the presence of plasma

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Chinese Physics C 2023年第3期47卷 262-272页

作者： Farruh Atamurotov Mubasher Jamil Kimet Jusufi Inha University in Tashkent Ziyolilar 9Tashkent 100170Uzbekistan Akfa University Milliy Bog'Street 264Tashkent 111221Uzbekistan National University of Uzbekistan Tashkent 100174Uzbekistan Tashkent State Technical University Tashkent 100095Uzbekistan School of Natural Sciences National University of Sciences and TechnologyIslamabad44000Pakistan Physics Department State University of Tetovolinden Street nn120oTetovoNorth Macedonia

In this study,the optical properties of a renormalization group improved(RGI)Schwarzschild black hole(BH)are investigated in a plasma *** with the equations of motion in a plasma medium,we aim to present the modifications in the shadow radius of the RGI *** this end,we compute the deflection angle of light in the weak gravity regime for uniform and non-uniform plasma ***,owing to the plasma media,we discover that the equations of motion for light obtained from the radiating and infalling/rest gas have to be ***,in turn,changes and modifies the expression for the intensity observed far away from the ***,we obtain the shadow images for the RGI BH for different plasma *** quantum effects change the background geometry,such effects are minimal,and practically detecting these effects using the current technology based on supermassive BH shadows is *** parameterΩencodes the quantum effects,and in principle,one expects such quantum effects to play significant roles only for very small ***,the effects of plasma media can play an important role in the optical appearance of BHs,as they affect and modify the equations of motion.

关键词： black hole shadow ofa black hole deflection angle

Thermal fluctuations,deflection angle,and greybody factor of a high-dimensional Schwarzschild black hole in scalar-tensor-vector gravity

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Communications in Theoretical Physics 2024年第11期76卷 100-112页

作者： Qian Li Yu Zhang Qi-Quan Li Qi Sun Faculty of Science Kunming University of Science and TechnologyKunmingYunnan 650500China

In this study,we examined the thermal fluctuations,deflection angle,and greybody factor of a high-dimensional Schwarzschild black hole in scalar-tensor-vector gravity(STVG).We calculated some thermodynamic quantities related to the correction of the black hole entropy caused by thermal fluctuations and discussed the effect of the correction parameters on these *** analyzing the changes in the corrected specific heat,we found that thermal fluctuations made the small black hole more *** is worth noting that the STVG parameter did not affect the thermodynamic stability of this black ***,by utilizing the Gauss-Bonnet theorem,the deflection angle was obtained in the weak field limit,and the effects of the two parameters on the results were ***,we calculated the bounds on the greybody factor of a massless scalar *** observed that as the STVG parameter around the black hole increased,the weak deflection angle became larger,and more scalar particles can reach ***,the spacetime dimension has the opposite effect on the STVG parameter on the weak deflection angle and greybody factor.

关键词： black hole thermal fluctuations deflection angle greybody factor

Is dark energy necessary for the sustainability of traversable wormholes?

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Chinese Physics C 2025年第1期49卷 290-304页

作者： Ayan Banerjee Sudan Hansraj Anirudh Pradhan Abdelghani Errehymy Astrophysics Research Centre School of MathematicsStatistics and Computer ScienceUniversity of KwaZulu-NatalPrivate Bag X54001Durban 4000South Africa Atrophysics Research Centre School of MathematicsStatistics and Computer ScienceUniversity of KwaZulu-NatalPrivate Bag X54001Durban 4000South Africa Centre for Cosmology Astrophysics and Space ScienceGLA UniversityMathura-281406Uttar PradeshIndia

Dark energy is typically the principal component needed for the traversability of wormholes(WH),as it provides the negative gravity effect required to keep the throat ***,can this be achieved without dark energy?It turns out that if we couple the trace of energy-momentum with the standard Einstein-Hilbert Lagrangian and utilize a specific equation of state(EoS),dark energy may be *** Casimir stress energy is known to result in the violation of the null energy condition(NEC)on the energy momentum *** phenomenon makes such an EoS an ideal candidate for generating traversable WH *** laboratory proven phenomenon provides a natural mechanism to sustain an open WH throat without relying on dark ***,we generate two classes of WH solutions using this in energy-momentum trace-coupling *** the specific choice of the Casimir EoS relating the energy-momentum tensor components[Kar and Sahdev:***.D 52,2030(1995)]and different choices of redshift functions,we determine the WH geometry *** obtained WH solutions violate the NECs,and all qualitative constraints demanded for physically realizable WHs are *** is demonstrated via graphical plots for a suitably chosen range of coupling parameter ***,our study investigates the repulsive effect of gravity,revealing that its presence leads to a negative deflection angle for photons traveling along null ***,we observe a consistent pattern of negative values for the deflection angle across all values of in the three scenarios considered,thus indicating the clear manifestation of the repulsive gravity *** of this is possible without invoking the existence of dark energy.

关键词： wormholes traversability casimir f(R,T)gravity deflection angle

Influence of deflection angles on flow behaviours in openchannel bends

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Journal of Mountain Science 2018年第10期15卷 2292-2306页

作者： LI Bing-dong ZHANG Xin-hua TANG Han-song TSUBAKI Ryota State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Department of Civil Engineering/City College City University of New York Department of Civil Engineering Nagoya University

The deflection angle of a river bend plays an important role on behaviours of the flow within it, and a clear understanding of the angle's influence is significant in both theoretical study and engineering application. This paper presents a systematic numerical investigation on effects of deflection angles(30°, 60°, 90°, 120°, 150°, and 180°) on flow phenomena and their evolution in open-channel bends using a Re-Normalization Group(RNG) κ-ε model and a volume of fluid(VOF) method. The numerical results indicate that the deflection angle is a key factor for flows in bends. It is shown that the maximum transverse slope of water surface occurs at the middle cross section of a bend, and it increases with the deflection angle. Besides a major vortex, or, the primary circulation cell near the channel bottom, a secondary vortex, or, an outer bank cell, may also appear above the former and near the outer bank when the deflection angle is sufficiently large, and it will gradually migrate towards the inner bank and evolve into an inner bank cell. The strength of the secondary circulations increases with the deflection angle. The simulation demonstrates that there is alow-stress zone on the bed near the outer bank and a high-stress zone on the bed near the inner bank, and both of them increase in size with the deflection angle. The maximum of shear stress on the inner bank increases nonlinearly with the angle, and its maximums on the outer bank and on the bed take place when the deflection angle becomes 120°.

关键词： Open channel deflection angle Transverse slope of water surface Secondary flow Shear stress

Effect of the Wick deflection angles on Heat Transfer Characteristics for the Flat LHP

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Frontiers in Heat and Mass Transfer 2023年第1期21卷 107-123页

作者： Zhuohuan Hu Sixian Sun Chengwei Yuan Yan Cao Jiayin Xu School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai200093China Aerospace System Engineering Shanghai Shanghai201109China

Loop Heat Pipe(LHP)is an efficient two-phase heat transfer device,which can be used in waste heat recovery,electronics cooling,aerospace and other *** wick,the core component of LHP,plays an important role in its start-up and *** this paper,the wick fabricated by 3D printing technology had uniform and interconnected *** the experiment,the position of the parallel vapor removal grooves was always fixed towards the vapor *** the cylindrical wick was placed in the evaporator,the rotation angle relative to its central axis could be changed,thus changing the number and shape of the pores facing the vapor removal *** wick deflection angle represented its change in spatial position relative to the fixed vapor removal *** effect of the wick deflection angles on the heat transfer characteristics of the flat LHP was experimentally *** was found that with the change of deflection angle,the number of pores in the evaporation-oriented zone would also change,which had a significant impact on the start-up process and heat transfer performance of *** the deflection angle was 30°,LHP could start fastest at a low heat load of 20 W and operate stable at a high heat load of 180 W.

关键词： Loop heat pipe heat transfer phase change 3D-printed wick deflection angle

deflection of cavitation bubble near the rigid wall with a gas-containing hole

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Journal of Hydrodynamics 2023年第2期35卷 330-337页

作者： Yu-rong Sun Qiang Zhong Zhi-feng Yao Dan Zi Ruo-fu Xiao Fu-jun Wang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing100083China

The presence of a rigid wall causes a microjet of the cavitation bubble to collapse to move toward the wall,while a free surface does the *** a rigid wall surface is combined with a free surface,it may affect the direction of the *** motive of this study is to find out the influence of the dynamic behavior of a laser-induced bubble near the rigid wall with a gas-containing *** of the bubble at different distances from the gas-containing hole in the horizontal and vertical directions were recorded by a high-speed camera(2.3×10^(5) fps).When the bubble collapse near the boundary,the bubble will produce two situations:away from or toward the *** focuses on the direction of the bubble,the oscillation period of a bubble,and reflection angle,and quantitative analysis of the *** was found that the boundary not only changes the morphologic of the bubble and the overall direction of movement but also affects the oscillation *** addition,it can control the deflection of the bubble.

关键词： Cavitation bubble bubble migration deflection angle gas-containing hole

Numerical analysis of deflection control of a gas plasma jet based on magnetohydrodynamic staggered electrode configuration

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Chinese Journal of Aeronautics 2022年第12期35卷 47-58页

作者： Jingjia ZHANG Junwei LI Zelin ZHANG Zhijun WEI School of Aerospace Beijing Institute of TechnologyBeijing 100081China

To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.

关键词： deflection angle deflection control Gas plasma Magnetohydrodynamic Thrust vector

Evolution of light deflection and shadow from a gauge-potential-like AdS black hole under the influence of a non-magnetic plasma medium

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Communications in Theoretical Physics 2024年第9期76卷 83-94页

作者： Riasat Ali Xia Tiecheng Muhammad Awais Rimsha Babar Department of Mathematics Shanghai University and Newtouch Center for Mathematics of Shanghai UniversityShanghai-200444China Department of Mathematics University of Engineering and Technology Lahore-54890Pakistan Department of Mathematics GC University Faisalabad Layyah CampusLayyah-31200Pakistan

We investigate the light deflection in the weak field approximation from the accelerating charged AdS black *** this purpose,we apply the Gauss–Bonnet theorem to calculate the light deflection in the weak field area and use the Gibbons–Werner approach to analyze the optical geometry of the accelerating charged AdS black hole in the non-magnetic plasma absence/presence of a non-magnetic *** also represent the graphical behavior of the light deflection angle *** impact *** also compute the light deflection angle using Keeton and Petters approximations under the impact of accelerating charged AdS black hole ***,by using the ray-tracing approach,we determine the shadow in the nonmagnetic plasma presence and also demonstrate that graphical shadow has an impact on the gauge potential,non-magnetic plasma frequencies and charge.

关键词： accelerating charged Ad S black hole Gibbons-Werner approach deflection angle ray-tracing approach shadow

Enhanced Recognition Algorithm for Facial Expressions under deflection angles

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Enhanced Recognition Algorithm for Facial Expressions under ...