In this paper,the non-static solutions for perfect fluid distribution with plane symmetry in f(R,T)gravitational theory are obtained.Firstly,using the Lie symmetries,symmetry reductions are performed for considered ve...In this paper,the non-static solutions for perfect fluid distribution with plane symmetry in f(R,T)gravitational theory are obtained.Firstly,using the Lie symmetries,symmetry reductions are performed for considered vector fields to reduce the number of independent variables.Then,corresponding to each reduction,exact solutions are obtained.Killing vectors lead to different conserved quantities.Therefore,we figure out the Killing vector fields corresponding to all derived solutions.The derived solutions are further studied and it is observed that all of the obtained spacetimes,at least admit to the minimal symmetry group which consists of δ_(y),δ_(z) and -zδ_(y)+yδ_(z).The obtained metrics,admit to 3,4,6,and 10,Killing vector fields.Conservation of linear momentum in the direction of y and z,and angular momentum along the x axis is provided by all derived solutions.展开更多
In this paper,we study the Joule–Thomson expansion for RN-AdS black holes immersed in perfect fluid dark matter.As perfect fluid dark matter is one of the dark matter candidates,we are interested in how it influences...In this paper,we study the Joule–Thomson expansion for RN-AdS black holes immersed in perfect fluid dark matter.As perfect fluid dark matter is one of the dark matter candidates,we are interested in how it influences the thermodynamic properties of black holes.Firstly,the negative cosmological constant could be interpreted as thermodynamic pressure and its conjugate quantity as the thermodynamic volume,which give us more physical insights into the black hole.Moreover,we derive the thermodynamic definitions and study the critical behaviour of the black hole.Secondly,the explicit expression of Joule–Thomson coefficient is obtained from the basic formulas of the pressure,the volume,the entropy and the temperature.Then,we obtain the inversion curves in terms of charge Q and parameterλ.Furthermore,we analyse the isenthalpic curve in T–P graph with the cooling–heating region determined by the inversion curve.At last,we derive the ratio of minimum inversion temperature to critical temperature and compare the result with that in the RN-AdS case.展开更多
In work, it is constructed a discrete mathematical model of motion of a perfect fluid. The fluid is represented as an ensemble of identical so-called liquid particles, which are in the form of extended geometrical obj...In work, it is constructed a discrete mathematical model of motion of a perfect fluid. The fluid is represented as an ensemble of identical so-called liquid particles, which are in the form of extended geometrical objects: circles and spheres for two-dimensional and three-dimensional cases, respectively. The mechanism of interaction between the liquid particles on a binary level and on the level of the n-cluster is formulated. This mechanism has previously been found by the author as part of the mathematical modeling of turbulent fluid motion. In the turbulence model was derived and investigated the potential interaction of pairs of liquid particles, which contained a singularity of the branch point. Exactly, this is possible to build in this article discrete stochastic-deterministic model of an ideal fluid. The results of computational experiment to simulate various kinds of flows in two-dimensional and three-dimensional ensembles of liquid particles are presented. Modeling was carried out in the areas of quadratic or cubic form. On boundary of a region satisfies the condition of elastic reflection liquid particles. The flows with spontaneous separation of particles in a region, various kinds of eddy streams, with the quite unexpected statistical properties of an ensemble of particles characteristic for the Fermi-Pasta-Ulam effect were found. We build and study the flow in which the velocity of the particles is calibrated. It was possible using the appropriate flows of liquid particles of the ensemble to demonstrate the possibility to reproduce any prescribed image by manipulating the parameters of the interaction. Calculations of the flows were performed with using MATLAB software package according to the algorithms presented in this article.展开更多
Mesonic perfect fluid solutions are found in general relativity with the aid of Einstein’s Rosen cylindrically symmetric space time. A static vacuum model and a non-static cosmological model corresponding to perfect ...Mesonic perfect fluid solutions are found in general relativity with the aid of Einstein’s Rosen cylindrically symmetric space time. A static vacuum model and a non-static cosmological model corresponding to perfect fluid are investigated. The cosmological term Λ is found to be a decreasing function of time which is supported by the result found from recent type Ia Supernovae observations. The various physical and geometrical features of the model are discussed.展开更多
Einstein’s field equations with variable gravitational and cosmological constants are considered in presence of perfect fluid for locally-rotationally-symmetric (LRS) Bianchi type-V space-time discussion in context o...Einstein’s field equations with variable gravitational and cosmological constants are considered in presence of perfect fluid for locally-rotationally-symmetric (LRS) Bianchi type-V space-time discussion in context of the particle creation. We present new shear free solutions for both absence and presence of particle creation. The solution describes the particle and entropy generation in the anisotropic cosmological models. We observe that time variation of gravitational and cosmological constant is needed for particle creation phenomena. Moreover, we obtained the particle production rate Γ(t) for this model and discussed in detail.展开更多
Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect ...Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect fluid Bianchi type- IX cosmological model is presented since other models doesn’t exist in Brans-Dicke scalar tensor theory of gravitation. Some physical properties of the model are also discussed.展开更多
This manuscript investigates a Schwarzschild black hole surrounded by perfect fluid dark matter embedded in a cloud of strings.The effects of its surroundings on thermodynamics,timelike and null geodesics,shadows,and ...This manuscript investigates a Schwarzschild black hole surrounded by perfect fluid dark matter embedded in a cloud of strings.The effects of its surroundings on thermodynamics,timelike and null geodesics,shadows,and quasinormal modes are analyzed.It is demonstrated that changes in spacetime,induced by the surrounding environment,significantly influence the stability,thermal phases,energy dynamics,particle trajectories,and observable features of the black hole's shadow,as well as its oscillation frequency and decay rate.展开更多
We obtain an exact solution for spherically symmetric Letelier AdS black holes immersed in perfect fluid dark matter(PFDM).Considering the cosmological constant as the positive pressure of the system and volume as its...We obtain an exact solution for spherically symmetric Letelier AdS black holes immersed in perfect fluid dark matter(PFDM).Considering the cosmological constant as the positive pressure of the system and volume as its conjugate variable,we analyze the thermodynamics of our black holes in the extended phase space.Owing to the background clouds of strings parameter(a)and the parameter endowed with PFDM(β),we analyze the Hawking temperature,entropy,and specific heat.Furthermore,we investigate the relationship between the photon sphere radius and phase transition for the Letelier AdS black holes immersed in PFDM.Through the analysis,with a particular condition,non-monotonic behaviors are found between the photon sphere radius,impact parameter,PFDM parameter,temperature,and pressure.We can regard the changes in both the photon sphere radius and impact parameter before and after phase transition as the order parameter;their critical exponents near the critical point are equal to the same value,1/2,similar to that in ordinary thermal systems.This indicates that a universal relation of gravity may exist near the critical point for a black hole thermodynamic system.展开更多
In this survey we report some recent results on the dynamics of a rigid body immersed in a twodimensional incompressible perfect fluid, with an emphasis on the zero-radius limit.
Math and physics proceed from assumptions to conclusions via a logical path. Artificial intelligence possesses the ability to follow logic, herein specifically applied to the problem of defining ontologically real 2D ...Math and physics proceed from assumptions to conclusions via a logical path. Artificial intelligence possesses the ability to follow logic, herein specifically applied to the problem of defining ontologically real 2D manifolds in a 3D continuum. Vortices and tori in fluids exhibit effective 2D surfaces, which, treated as manifolds, allow application of calculus on the boundaries of the structures. Recent papers in primordial field theory (PFT) have employed Calabi-Yau geometry and topology to develop a fermion structure. We desire a logical justification of this application and herein explore the use of artificial intelligence to assist in logic verification. A proof is outlined by the author and formalized by the AI.展开更多
A perfect fluid with self-similarity of the second kind is studied within the framework of the teleparallel equivalent of general relativity （TEGR）. A spacetime which is not asymptotically fiat is derived. The energ...A perfect fluid with self-similarity of the second kind is studied within the framework of the teleparallel equivalent of general relativity （TEGR）. A spacetime which is not asymptotically fiat is derived. The energy conditions of this spacetime are studied. It is shown that after some time the strong energy condition is not enough to satisfy showing a transition from standard matter to dark energy. The singularities of this solution are discussed.展开更多
Exact solution of Einstein＇s field equations is obtained for massive string cosmological model of Bianchi III space-time using the technique given by Letelier （1983） in presence of perfect fluid and electromagnetic...Exact solution of Einstein＇s field equations is obtained for massive string cosmological model of Bianchi III space-time using the technique given by Letelier （1983） in presence of perfect fluid and electromagnetic field. To get the deterministic solution of the field equations the expansion 0 in the model is considered as proportional to the eigen value σ2^2of the shear tensor σi^j and also the fluid obeys the barotropic equation of state. It is observed that in early stage of the evolution of the universe string dominates over the particle whereas the universe is dominated by massive string at the late time. It is also observed that the string phase of the universe disappears in our model because particle density becomes negative. Some physical and geometric properties of the model are also discussed.展开更多
The wave diffraction and radiation around a floating body is considered within the framework of the linear potential theory in a fairly perfect fluid. The fluid domain extended infinitely in the horizontal directions ...The wave diffraction and radiation around a floating body is considered within the framework of the linear potential theory in a fairly perfect fluid. The fluid domain extended infinitely in the horizontal directions but is limited by the sea bed, the body hull, and the part of the free surface excluding the body waterplane, and is subdivided into two subdomains according to the body geometry. The two subdomains are connected by a control surface in fluid. In each subdomain, the velocity potential is described by using the usual boundary integral representation involving Green functions. The boundary integral equations are then established by satisfying the boundary conditions and the continuous condition of the potential and the normal derivation across the control surface. This multi-domain boundary element method （MDBEM） is particularly interesting for bodies with a hull form including moonpools to which the usual BEM presents singularities and slow convergence of numerical results. The application of the MDBEM to study the resonant motion of a water column in moonpools shows that the MDBEM provides an efficient and reliable prediction method.展开更多
基金UGC for providing financial support in the form of the JRF fellowship via letter NTA Ref.No.:201610006334the financial support provided under the scheme‘Fund for Improvement of S&T Infrastructure(FIST)’of the Department of Science&Technology(DST),Government of India via letter No.SR/FST/MS-I/2021/104 to the Department of Mathematics and Statistics,Central University of Punjab。
文摘In this paper,the non-static solutions for perfect fluid distribution with plane symmetry in f(R,T)gravitational theory are obtained.Firstly,using the Lie symmetries,symmetry reductions are performed for considered vector fields to reduce the number of independent variables.Then,corresponding to each reduction,exact solutions are obtained.Killing vectors lead to different conserved quantities.Therefore,we figure out the Killing vector fields corresponding to all derived solutions.The derived solutions are further studied and it is observed that all of the obtained spacetimes,at least admit to the minimal symmetry group which consists of δ_(y),δ_(z) and -zδ_(y)+yδ_(z).The obtained metrics,admit to 3,4,6,and 10,Killing vector fields.Conservation of linear momentum in the direction of y and z,and angular momentum along the x axis is provided by all derived solutions.
基金supported by NSFC(Grant No.11947408 and 11875196)。
文摘In this paper,we study the Joule–Thomson expansion for RN-AdS black holes immersed in perfect fluid dark matter.As perfect fluid dark matter is one of the dark matter candidates,we are interested in how it influences the thermodynamic properties of black holes.Firstly,the negative cosmological constant could be interpreted as thermodynamic pressure and its conjugate quantity as the thermodynamic volume,which give us more physical insights into the black hole.Moreover,we derive the thermodynamic definitions and study the critical behaviour of the black hole.Secondly,the explicit expression of Joule–Thomson coefficient is obtained from the basic formulas of the pressure,the volume,the entropy and the temperature.Then,we obtain the inversion curves in terms of charge Q and parameterλ.Furthermore,we analyse the isenthalpic curve in T–P graph with the cooling–heating region determined by the inversion curve.At last,we derive the ratio of minimum inversion temperature to critical temperature and compare the result with that in the RN-AdS case.
文摘In work, it is constructed a discrete mathematical model of motion of a perfect fluid. The fluid is represented as an ensemble of identical so-called liquid particles, which are in the form of extended geometrical objects: circles and spheres for two-dimensional and three-dimensional cases, respectively. The mechanism of interaction between the liquid particles on a binary level and on the level of the n-cluster is formulated. This mechanism has previously been found by the author as part of the mathematical modeling of turbulent fluid motion. In the turbulence model was derived and investigated the potential interaction of pairs of liquid particles, which contained a singularity of the branch point. Exactly, this is possible to build in this article discrete stochastic-deterministic model of an ideal fluid. The results of computational experiment to simulate various kinds of flows in two-dimensional and three-dimensional ensembles of liquid particles are presented. Modeling was carried out in the areas of quadratic or cubic form. On boundary of a region satisfies the condition of elastic reflection liquid particles. The flows with spontaneous separation of particles in a region, various kinds of eddy streams, with the quite unexpected statistical properties of an ensemble of particles characteristic for the Fermi-Pasta-Ulam effect were found. We build and study the flow in which the velocity of the particles is calibrated. It was possible using the appropriate flows of liquid particles of the ensemble to demonstrate the possibility to reproduce any prescribed image by manipulating the parameters of the interaction. Calculations of the flows were performed with using MATLAB software package according to the algorithms presented in this article.
文摘Mesonic perfect fluid solutions are found in general relativity with the aid of Einstein’s Rosen cylindrically symmetric space time. A static vacuum model and a non-static cosmological model corresponding to perfect fluid are investigated. The cosmological term Λ is found to be a decreasing function of time which is supported by the result found from recent type Ia Supernovae observations. The various physical and geometrical features of the model are discussed.
文摘Einstein’s field equations with variable gravitational and cosmological constants are considered in presence of perfect fluid for locally-rotationally-symmetric (LRS) Bianchi type-V space-time discussion in context of the particle creation. We present new shear free solutions for both absence and presence of particle creation. The solution describes the particle and entropy generation in the anisotropic cosmological models. We observe that time variation of gravitational and cosmological constant is needed for particle creation phenomena. Moreover, we obtained the particle production rate Γ(t) for this model and discussed in detail.
文摘Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect fluid Bianchi type- IX cosmological model is presented since other models doesn’t exist in Brans-Dicke scalar tensor theory of gravitation. Some physical properties of the model are also discussed.
基金B.C.Lütfüoğlu is grateful to Excellence project PřF UHK 2211/2023-2024 for the financial support。
文摘This manuscript investigates a Schwarzschild black hole surrounded by perfect fluid dark matter embedded in a cloud of strings.The effects of its surroundings on thermodynamics,timelike and null geodesics,shadows,and quasinormal modes are analyzed.It is demonstrated that changes in spacetime,induced by the surrounding environment,significantly influence the stability,thermal phases,energy dynamics,particle trajectories,and observable features of the black hole's shadow,as well as its oscillation frequency and decay rate.
基金Supported by the National Natural Science Foundation of China(11875151,12347177,12247101)the 111 Project under(B20063)the Lanzhou City's Scientific Research Funding Subsidy to Lanzhou University。
文摘We obtain an exact solution for spherically symmetric Letelier AdS black holes immersed in perfect fluid dark matter(PFDM).Considering the cosmological constant as the positive pressure of the system and volume as its conjugate variable,we analyze the thermodynamics of our black holes in the extended phase space.Owing to the background clouds of strings parameter(a)and the parameter endowed with PFDM(β),we analyze the Hawking temperature,entropy,and specific heat.Furthermore,we investigate the relationship between the photon sphere radius and phase transition for the Letelier AdS black holes immersed in PFDM.Through the analysis,with a particular condition,non-monotonic behaviors are found between the photon sphere radius,impact parameter,PFDM parameter,temperature,and pressure.We can regard the changes in both the photon sphere radius and impact parameter before and after phase transition as the order parameter;their critical exponents near the critical point are equal to the same value,1/2,similar to that in ordinary thermal systems.This indicates that a universal relation of gravity may exist near the critical point for a black hole thermodynamic system.
基金supported by the Agence Nationale de la Recherche, Project IFSMACS (Grant No. ANR-15-CE40-0010)Project BORDS (Grant No. ANR-16-CE40-0027-01)+3 种基金Project SINGFLOWS (Grant No. ANR-18-CE40-0027-01)the Conseil Régionale d’Aquitaine (Grant No. 2015.1047.CP)the H2020MSCA-ITN-2017 program Project ConFlex Grant ETN-765579the Institut Universitaire de France
文摘In this survey we report some recent results on the dynamics of a rigid body immersed in a twodimensional incompressible perfect fluid, with an emphasis on the zero-radius limit.
文摘Math and physics proceed from assumptions to conclusions via a logical path. Artificial intelligence possesses the ability to follow logic, herein specifically applied to the problem of defining ontologically real 2D manifolds in a 3D continuum. Vortices and tori in fluids exhibit effective 2D surfaces, which, treated as manifolds, allow application of calculus on the boundaries of the structures. Recent papers in primordial field theory (PFT) have employed Calabi-Yau geometry and topology to develop a fermion structure. We desire a logical justification of this application and herein explore the use of artificial intelligence to assist in logic verification. A proof is outlined by the author and formalized by the AI.
文摘A perfect fluid with self-similarity of the second kind is studied within the framework of the teleparallel equivalent of general relativity （TEGR）. A spacetime which is not asymptotically fiat is derived. The energy conditions of this spacetime are studied. It is shown that after some time the strong energy condition is not enough to satisfy showing a transition from standard matter to dark energy. The singularities of this solution are discussed.
文摘Exact solution of Einstein＇s field equations is obtained for massive string cosmological model of Bianchi III space-time using the technique given by Letelier （1983） in presence of perfect fluid and electromagnetic field. To get the deterministic solution of the field equations the expansion 0 in the model is considered as proportional to the eigen value σ2^2of the shear tensor σi^j and also the fluid obeys the barotropic equation of state. It is observed that in early stage of the evolution of the universe string dominates over the particle whereas the universe is dominated by massive string at the late time. It is also observed that the string phase of the universe disappears in our model because particle density becomes negative. Some physical and geometric properties of the model are also discussed.
文摘The wave diffraction and radiation around a floating body is considered within the framework of the linear potential theory in a fairly perfect fluid. The fluid domain extended infinitely in the horizontal directions but is limited by the sea bed, the body hull, and the part of the free surface excluding the body waterplane, and is subdivided into two subdomains according to the body geometry. The two subdomains are connected by a control surface in fluid. In each subdomain, the velocity potential is described by using the usual boundary integral representation involving Green functions. The boundary integral equations are then established by satisfying the boundary conditions and the continuous condition of the potential and the normal derivation across the control surface. This multi-domain boundary element method （MDBEM） is particularly interesting for bodies with a hull form including moonpools to which the usual BEM presents singularities and slow convergence of numerical results. The application of the MDBEM to study the resonant motion of a water column in moonpools shows that the MDBEM provides an efficient and reliable prediction method.
