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Phantom Energy Accretion by a Stringy Charged Black Hole

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Chinese Physics Letters 2012年第1期29卷 28-30页

作者： M.Sharif g.abbas Department of Mathematics University of the PunjabQuaid-e-Azam CampusLahore-54590Pakistan

We investigate the dynamical behavior of phantom energy near a stringy magnetically charged black *** this purpose,we derive equations of motion for steady-state spherically symmetric flow of phantom energy onto the stringy magnetically charged black *** is found that phantom energy accreting onto a black hole decreases its ***,the location of the critical points of accretion is explored,which yields a mass to charge *** ratio implies that accretion process cannot transform a black hole into an extremal black hole or a naked singularity,hence cosmic censorship hypothesis remains valid here.

关键词： singularity hence implies

Singularities of noncompact charged objects

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Chinese Physics B 2013年第3期22卷 192-195页

作者： M.Sharif g.abbas Department of Mathematics University of the PunjabQuaid-e-Azam CampusLahore-54590Pakistan

We formulate a model for noncompact spherical charged objects in the framework of noncommutative field *** Einstein-Maxwell field equations are solved with charged anisotropic *** choose matter and charge densities as functions of the two parameters,instead of defining these quantities in terms of the gaussian distribution *** is found that the corresponding densities and the Ricci scalar are singular in origin,whereas the metric is nonsingular,indicating a spacelike *** numerical solution of the horizon equation implies that there are two or one or no horizon（s）,depending on the *** also evaluate the Hawking temperature and find that a black hole with two horizons is evaporated to an extremal black hole with one horizon.

关键词： noncommutative geometry electromagnetic field spacetime singularity

Thermodynamics of Phantom Energy Accreting onto a Black Hole in Einstein–Power–Maxwell gravity

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Chinese Physics Letters 2013年第10期30卷 34-37页

作者： g.abbas R.M.Ramzan Department of Mathematics COMSATS Institute of Information TechnologySahiwal-67000Pakistan Department of Mathematics The Islamia University BahawalpurPakistan

We investigate the phantom energy accretion onto a 3D black hole formulated in the Einstein–Power–Maxwell theory,and present the conditions for critical accretion of phantom energy onto the black ***,we discuss the thermodynamics of phantom energy accreting onto the black hole and find that the first law of thermodynamics is easily satisfied while the second law and the generalized second law of thermodynamics remain invalid and conditionally valid,*** results for the Banados–Teitelboim–Zanelli black hole can be recovered by taking Maxwellian contribution equal to zero.

关键词： Maxwell black law Power

Parallel propagating modes and anomalous spatial damping in the ultra-relativistic electron plasma with arbitrary degeneracy

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Chinese Physics B 2017年第11期26卷 76-82页

作者： H Farooq M Sarfraz Z Iqbal g abbas H A Shah Department of Physics Government College University government College University

The dispersion relations of parallel propagating modes（Langmuir mode, right and left handed circular polarized waves） in the weak magnetic field limit ｜ω-k·v｜〉〉？ are considered for ultra-relativistic arbitrary degenerate electron plasma. The results are presented in terms of moments of Fermi-Dirac distribution. The increase in the electron equilibrium number density from negative large（weakly degenerate） to positive large（highly degenerate） values of μ/Te is observed（where μ is the electron chemical potential and Te is the electron thermal energy）. As a result, shifting of the cutoff points in all the real dispersion branches towards the higher values and increasing in the band gap between unmagnetized longitudinal and transverse modes in k-space are examined. Also, the suppression of the weak magnetic field effects in weakly magnetized right handed and left handed circular polarized waves and a decrease in the longitudinal and transverse screening effects are observed in the graphical patterns due to an increase in the equilibrium number density.

关键词： degenerate Fermi gases relativistic plasmas electromagnetic waves

Physical aspects of anisotropic compact stars in f(T,T) gravity with off diagonal tetrad

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Chinese Physics C 2021年第8期45卷 190-205页

作者： M.Zubair Allah Ditta g.abbas Rabia Saleem Department of Mathematics COMSATS University IslamabadLahore CampusLahorePakistan Department of Mathematics The Islamia University of BahawalpurBahawalpurPakistan

This study addresses the formation of anisotropic compact star models in the background of f(T,T)gravity(where T and T represent the torsion and trace of the energy momentum tensor,respectively).f(T,T)gravity is an extension of the f(T)theory,and it allows a general non-minimal coupling between T and *** this setup,we apply Krori and Barua's solution to the static spacetime with the components ξ=Br^(2)+c and ψ=Ar^(2).To develop viable solutions,we select a well-known model f(T,T)=αT^(m)+βT+Ф(where α and β are coupling parameters,and Ф indicates the cosmological constant).We adopt the conventional matching of interior and exterior space time to evaluate the unknowns,which are employed in the stellar *** present a comprehensive discussion on the stellar properties to elaborate the anisotropic nature of compact stars corresponding to well-known models:PSRJ1416-2230,4U1608-52,CenX-3,EXO1785-248,and *** physical analysis,it is observed that the solution of compact spheres satisfy the acceptability criteria,and its models behave optimally and depict stability and consistency,in accordance with f(T,T)gravity.

关键词： f(T,T)gravity compact stars stellar models

Heat transfer analysis in particle-laden flows using the immersed boundary method

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Particuology 2024年第7期90卷 394-403页

作者： Ali abbas Zaidi Department of Mechanical Engineering University of Manitoba75A Chancellors CircleWinnipegR3T 5V6Canada

This paper investigates an efficient immersed boundary method(IBM)for multiple-core CPU machines with local grid refinement for the calculation of heat transfer between fluids and finite-sized *** fluid momentum equations are solved by using the fractional step method,while the energy equation is solved by employing the second-order Adams-Bashforth *** efficient load balancing between the CPU cores,the coupling between particles and fluid is obtained by applying the body force in the fluid equations,which depends on the solid volume fraction of particles contained in each grid cell,and then by linearly interpolating the particle temperature and velocity on the fluid grid cell(in place of the delta function commonly used in literature).Several test cases from the literature are studied,and good agreement is observed between the simulation results and the ***,a scaling study on multiple core machines is performed,demonstrating the proposed IBM's capabilities for a significant reduction in processing time.

关键词： Heat transfer Immersed boundary method Particle resolved direct numerical simulations Fluid solid interactions

Physical aspects of anisotropic compact stars in f(T,■) gravity with off diagonal tetrad

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Chinese Physics C 2021年第8期 195-210页

作者： M.Zubair Allah Ditta g.abbas Rabia Saleem Department of Mathematics COMSATS University Islamabad Department of Mathematics The Islamia University of Bahawalpur

This study addresses the formation of anisotropic compact star models in the background of f(T,■)gravity(where T and ■ represent the torsion and trace of the energy momentum tensor,respectively).f(T,■) gravity is an extension of the f(T) theory,and it allows a general non-minimal coupling between T and ■.In this setup,we apply Krori and Barua’s solution to the static spacetime with the components ξ=Br~2+c and Ψ=Ar~*** develop viable solutions,we select a well-known model f(T,■)=aT~m+β■+φ(where α and β are coupling parameters,and φ indicates the cosmological constant).We adopt the conventional matching of interior and exterior space time to evaluate the unknowns,which are employed in the stellar *** present a comprehensive discussion on the stellar properties to elaborate the anisotropic nature of compact stars corresponding to well-known models:PSRJ1416-2230,4U1608-52,CenX-3,EX01785-248,and *** physical analysis,it is observed that the solution of compact spheres satisfy the acceptability criteria,and its models behave optimally and depict stability and consistency,in accordance with f(T,■) gravity.

关键词：

Seismic performance evaluation of hybrid coupled shear wall system with shear and flexural fuse-type steel coupling beams

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Earthquake Engineering and Engineering Vibration 2024年第3期23卷 691-712页

作者： Zahra Ramezandoust abbas Tajaddini Panam Zarfam Department of Civil Engineering Science and Research branchIslamic Azad UniversityTehran 14778-93855Iran Department of Civil Engineering Karaj BranchIslamic Azad UniversityKaraj 31485-313Iran

Replaceable flexural and shear fuse-type coupling beams are used in hybrid coupled shear wall(HCSW)systems,enabling concrete buildings to be promptly recovered after severe *** study aimed to analytically evaluate the seismic behavior of flexural and shear fuse beams situated in short-,medium-and high-rise RC buildings that have *** building groups hypothetically located in a high seismic hazard zone were studied.A series of 2D nonlinear time history analyses was accomplished in OpenSees,using the ground motion records scaled at the design basis earthquake *** was found that the effectiveness of fuses in HCSWs depends on various factors such as size and scale of the building,allowable rotation value,inter-story drift ratio,residual drift quantity,energy dissipation value of the fuses,*** results show that shear fuses better meet the requirements of rotations and *** contrast,flexural fuses dissipate more energy,but their sectional stiffness should increase to meet other *** was concluded that adoption of proper fuses depends on the overall scale of the building and on how associated factors are considered.

关键词： hybrid coupled shear wall steel fuse coupling beam shear and flexural fuse nonlinear dynamic analysis seismic performance

Accretion around a hairy black hole in the framework of gravitational decoupling theory

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Chinese Physics C 2023年第12期47卷 180-194页

作者： H.Rehman g.abbas Department of Mathematics The Islamia University of BahawalpurBahawalpur Pakistan

We investigate astrophysical accretion onto a static and spherically symmetric hairy black hole withinthe framework of gravitational decoupling. To achieve this goal, we examine the accretion procedure for severaltypes of perfect fluids, including polytropic fluid and ultra-stiff, ultra-relativistic, radiation, and sub-relativistic isothermalfluids. Moreover, we determine the critical or sonic points for numerous fluid forms that are accreting ontothe black hole by utilizing the Hamiltonian dynamical approach. Additionally, the closed form of the solutions arepresented for a number of fluids, which are represented in phase diagram curves. We estimate the mass accretion rateof a static and spherically symmetric hairy black hole within the framework of gravitational decoupling. These findingsare helpful in constraining the parameters of black holes while physical matter accretes onto the black holes.

关键词： general relativity astrophysical accretion black hole