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Plane Symmetric Solutions in f(R,T) Gravity

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Communications in Theoretical Physics 2016年第3期65卷 301-307页

作者： m.Farasat shamir Department of Sciences and Humanities National University of Computer and Emerging SciencesLahore Campus

The main purpose of this paper is to investigate the exact solutions of plane symmetric spacetime in the context of f(R,T)gravity[***.D 84(2011)024020],where f(R,T)is an arbitrary function of Ricci scalar R and trace of the energy momentum tensor *** explore the exact solutions for two different classes of f(R,T)*** first class f(R,T)=R+2f(T)yields a solution which corresponds to Taub's metric while the second class f(R,T)=f_1(R)+f_2(T)provides two additional solutions which include the well known anti-deSitter *** energy densities and corresponding functions for f(R,T)models are evaluated in each case.

关键词：重力作用 deSitter时空对称解平面能量动量张量能量密度评价模型精确解

Energy Bounds for Static Spherically Symmetric Spacetime in f(R, G) Gravity

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Communications in Theoretical Physics 2018年第8期69卷 190-196页

作者： m.Farasat shamir Ayesha Komal Department of Sciences and Humanities National University of Computer and Emerging Sciences

The main purpose of this paper is to investigate energy bounds in the context of f(R, G) gravity. To meet this aim, we choose static spherically symmetric spacetime in f(R, G) gravity to develop the field equations. We select three different models of f(R, G) gravity, which are thoroughly discussed in the literature. Firstly, the inequalities are formulated using energy bounds and then viability of the considered models are checked respectively. Graphical analysis show that specific f(R, G) gravity models are satisfied under suitable values of model parameters. It is shown that in a certain case energy bounds are satisfied expect SEC, which supports the late time acceleration expansion of unverse.

关键词：精力对称球状静态模型参数上下文

f(G,T) Gravity with Cylindrically Symmetric Relativistic Fluids

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Communications in Theoretical Physics 2019年第2期71卷 220-230页

作者： m.Farasat shamir m.Awais Sadiq Department of Sciences and Humanities National University of Computer and Emerging SciencesLahore Campus

The aim of this paper is to examine the structure scalars with account of f(G, T) theory of gravity. We consider the cylindrically symmetric spacetime with dissipative anisotropic background. We have determined the structure scalars by orthogonally decomposing the Riemann curvature tensor and it is shown that these scalars are associated with fundamental properties of fluid. We further investigate the mass function along with the transport equation and discuss their role on the evolutionary stages of relativistic stellar systems. We have also analyzed these structure scalars for static fluid distributions and it is concluded that all possible solutions of field equations can be expressed through these scalars.

关键词： f(G,T) gravity cylindrically symmetric spacetime structure scalars

Behavior of Anisotropic Compact Stars in f(R,∅) Gravity

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Communications in Theoretical Physics 2019年第5期71卷 599-609页

作者： m.Farasat shamir Adnan malik Department of Sciences and Humanities National University of Computer and Emerging Sciences

The aim of this paper is to investigate modified f(R, ?) theory of gravity, where R and ? represent the Ricci scalar and scalar potential respectively. Specifically, we take the spherically symmetric spacetime to discuss the possible emergence of compact stars. We study the physical behavior of compact stars by considering 4 U 1820-30, SAX J1808-3658 and Her X1, which are three popular models of compact stars. The graphical analysis of energy density, radial pressure, tangential pressure, energy conditions as well as stability of compact stars has been shown. It is concluded that behavior of these three stars is usual for f(R, ?) gravity models with some specific choices of model parameters.

关键词： f(R,∅) gravity spherically symmetric spacetime compact stars Klein-Gordon equation

Dust Static Cylindrically Symmetric Solutions in f(R) Gravity

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Communications in Theoretical Physics 2014年第9期61卷 348-352页

作者： m. Farasat shamir Zahid Raza Department of Sciences and Humanities National University of Computer and Emerging SciencesLahore Campus Pakistan

This paper is devoted to investigate non-vacuum solutions of cylindrically symmetric spacetime in the context of metric f(R) gravity. We take dust matter to find energy density of the universe. In particular, we find two exact solutions, which correspond to two f(R) models in each case. The first solution provides constant curvature while the second solution corresponds to non-constant curvature. The functions of the Ricci scalar and energy densities are evaluated in each case.

关键词： f(R) gravity cylindrically symmetric spacetime

Conserved Quantities in f(R) Gravity via Noether Symmetry

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Chinese Physics Letters 2012年第8期29卷 33-37页

作者： m.Farasat shamir Adil Jhangeer Akhlaq Ahmad Bhatti Department of Sciences&Humanities National University of Computer&Emerging SciencesLahore CampusPakistan

We investigate f(R)gravity using the Noether symmetry *** this purpose,we consider Friedmann Robertson–Walker(FRW)universe and spherically symmetric *** Noether symmetry generators are evaluated for some specific choice of f(R)models in the presence of the gauge ***,we calculate the corresponding conserved quantities in each ***,the importance and stability criteria of these models are discussed.

关键词： symmetry Noether gauge

Wormhole solutions and energy conditions in f(R,G)gravity

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Communications in Theoretical Physics 2021年第11期73卷 131-141页

作者： m Farasat shamir G mustafa Saad Waseem mushtaq Ahmad National University of Computer and Emerging Sciences Lahore CampusPakistan Department of mathematics Shanghai UniversityShanghai200444China National University of Computer and Emerging Sciences Chiniot-Faisalabad CampusPakistan

In this manuscript,the traversable wormhole solutions have been explored in modified f(R,G)gravity by taking into consideration the model f(R,G)=R+rG2,where R is the Ricci curvature scalar and G is the Gauss–Bonnet *** acceptable form of the redshift function has been incorporated which is a non-constant in nature along with the implementation of those already defined in literature,the two shape functions namely b(r)=r/exp(r-r0)and b(r)=r0log(r+1)/log(r0+1).It is shown by studying the energy condition and through the graphical analysis that the null energy bounds for the effective energy-momentum tensor are generally violated for the presence of the ordinary matter in modified f(R,G)*** conditions associated with the matter content threading the wormhole geometries are evaluated and in general are found to favor the null energy conditions in the vicinity of the wormhole throat,the existence of the nonexotic wormhole geometries threaded by the matter has been confirmed under this gravity.

关键词： f(R,G)gravity energy conditions wormholes shape function

Comprehensive analysis of relativistic embedded class-I exponential compact spheres in f(R,φ)gravity via Karmarkar condition

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Communications in Theoretical Physics 2023年第10期75卷 100-110页

作者： Zoya Asghar Adnan malik m Farasat shamir Fatemah mofarreh National University of Computer and Emerging Sciences Lahore CampusPakistan School of mathematical Sciences Zhejiang Normal UniversityJinhuaZhejiangChina Department of mathematics University of Management and TechnologySialkot CampusPakistan mathematical Science Department Faculty of Science Princess Nourah bint Abdulrahman University Riyadh 11546Saudi Arabia

In this article,we use the prominent Karmarkar condition to investigate some novel features of astronomical objects in the f(R,φ)gravity;R andφrepresent the Ricci curvature and the scalar field,*** is worth noting that we classify the exclusive set of modified field equations using the exponential type model of the f(R,φ)theory of gravity f(R,φ)=φ(R+α(eβR-1)).We show the embedded class-I approach via a static,spherically symmetric spacetime with an anisotropic *** accomplish our objective,we use a particular interpretation of metric potential(grr)that has already been given in the literature and then presume the Karmarkar condition to derive the second metric *** employ distinct compact stars to determine the values of unknown parameters emerging in metric *** ensure the viability and consistency of our exponential model,we execute distinct physical evolutions,*** graphical structure of energy density and pressure evolution,mass function,adiabatic index,stability,equilibrium,and energy *** investigation reveals that the observed anisotropic findings are physically appropriate and have the highest level of precision.

关键词： stellar structures metric potentials f(R,φ)theory of gravity Karmarkar condition

Rescue from complications after pancreaticoduodenectomies at a low-volume Caribbean center:Value of tailored peri-pancreatectomy protocols

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World Journal of Gastrointestinal Surgery 2024年第3期16卷 681-688页

作者： shamir O Cawich Elijah Dixon Parul J Shukla Shailesh V Shrikhande Rahul R Deshpande Fawwaz mohammed Neil W Pearce Wesley Francis Shaneeta Johnson Johann Bujhawan Department of Surgery University of the West IndiesSt Augustine 000000Trinidad and Tobago Department of Surgery Faculty of MedicineUniversity of CalgaryCalgaryAlberta T2N2T9Canada Department of Surgery Weill Cornell Medical CollegeNew YorkNY 10065United States Department of Surgical Oncology Tata Memorial CenterHomi Bhabha National UniversityMumbai 400012India Department of Surgery Manchester Royal InfirmaryManchester M139WLUnited Kingdom University Surgical Unit Southampton General HospitalSouthampton SO166YDUnited Kingdom Department of Surgery University of the West IndiesNassau N-1184Bahamas Department of Surgery Morehouse School of MedicineAtlantaGA 30310United States Department of Surgery General Hospital in Port of SpainPort of Spain 000000Trinidad and Tobago

BACKGROUND Pancreaticoduodenectomy(PD)is a technically complex operation,with a re-latively high risk for *** ability to rescue patients from post-PD complications is as a recognized quality *** protocols were instituted at our low volume facility in the year *** To document the rate of rescue from post-PD complications with tailored protocols in place as a measure of *** A retrospective audit was performed to collect data from patients who experienced major post-PD complications at a low volume pancreatic surgery unit in Trinidad and Tobago between January 1,2013 and June 30,***-dardized definitions from the International Study Group of Pancreatic Surgery were used to define post-PD complications,and the modified Clavien-Dindo classification was used to classify post-PD *** Over the study period,113 patients at a mean age of 57.5 years(standard deviation[SD]±9.23;range:30-90;median:56)underwent PDs at this *** complications were recorded in 33(29.2%)patients at a mean age of 53.8 years(SD:±7.9).Twenty-nine(87.9%)patients who experienced major morbidity were salvaged after aggre-ssive treatment of their ***(3.5%)died from bleeding pseudoaneurysm(1),septic shock secondary to a bile leak(1),anastomotic leak(1),and myocardial infarction(1).There was a significantly greater salvage rate in patients with American Society of Anesthesiologists scores≤2(93.3%vs 25%;P=0.0024).CONCLUSION This paper adds to the growing body of evidence that volume alone should not be used as a marker of quality for patients requiring *** low volumes at our facility,we demonstrated that 87.9%of patients were rescued from major *** attributed this to several factors including development of rescue protocols,the competence of the pancreatic surgery teams and continuous,and adaptive learning by the entire institution,cul-minating in the development of tailored peri-pancreatectomy protoc

关键词： Pancreas Complication Rescue Failure morbidity mortality Pancreaticoduodenectomy