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Refinement of the Proposed Gamma-Ray Burst Time Delay Model

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International Journal of Astronomy and astrophysics 2024年第2期14卷 120-147页

作者： Godson Fortune Abbey Joseph Simfukwe Prospery Christopher Simpemba Saul Paul Phiri Alok Srivastava Golden Gadzirayi Nyambuya Department of Physic School of Mathematics and Natural Sciences The Copperbelt University Kitwe Republic of Zambia Fundamental theoretical and Research group Department of Applied Physics Faculty of Applied Sciences National University of Science & Technology Bulawayo Republic of Zimbabwe

This paper is the second instalment in our study of the observed time delay in the arrival times of radio photons emanating from Gamma Ray Bursts (GRBs). The mundane assumption in contemporary physics as to the cause of these pondersome time delays is that they are a result of the photon being endowed with a non-zero mass. While we do not rule out the possibility of a non-zero mass for the photon, our working assumption is that the major cause of these time delays may very well be that these photons are travelling in a rarefied cosmic plasma in which the medium’s electrons interact with the electric component of the Photon, thus generating tiny currents that lead to dispersion, hence, a frequency-dependent speed of Light (FDSL). In the present instalment, we “improve” on the model presented in the first instalment by dropping the assumption that the resultant pairs of these radio photons leave the shock front simultaneously. The new assumption of a non-simultaneous— albeit systematic—emission of these photon pairs allows us to obtain a much more convincing and stronger correlation in the time delay. This new correlation allows us to build a unified model for the four GRBs in our sample using a relative distance correction mechanism. The new unified model allows us to obtain as our most significant result a value for the frequency equivalence of the interstellar medium (ISM)’s conductance ν* ~ 1.500 ± 0.009 Hzand also an independent distance measure to the GRBs where we obtain for our four GRB samples an average distance of: ~69.40 ± 0.10, 40.00 ± 0.00, 58.40 ± 0.40, and 86.00 ± 1.00 Mpc, for GRB 030329, 980425, 000418 and 021004 respectively.

关键词： Gamma-Ray Bursts (GRB) Photon Mass Plasma Time Delay Fireball Model

IMEX Evolution of Scalar Fields on Curved Backgrounds

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Communications in Computational Physics 2009年第10期6卷 1063-1094页

作者： S.R.Lau H.P.Pfeiffer J.S.Hesthaven Division of Applied Mathematics Brown UniversityProvidenceRI 02912USA theoretical astrophysics and relativity group 130-33 California Institute of TechnologyPasadenaCA 91125USA Also at the Department of Mathematics and Statistics University of New MexicoAlbuquerqueNM 87131USA.

Inspiral of binary black holes occurs over a time-scale of many orbits,far longer than the dynamical time-scale of the individual black *** evolutions of a binary system therefore require excessively many time-steps to capture interesting *** present a strategy to overcome the Courant-Friedrichs-Lewy condition in such evolutions,one relying on modern implicit-explicit ODE solvers and multidomain spectral methods for elliptic *** analysis considers the model problem of a forced scalar field propagating on a generic curved ***,we encounter and address a number of issues pertinent to the binary black hole problem in full general *** to the Schwarzschild geometry in KerrSchild coordinates,we document the results of several numerical experiments testing our strategy.

关键词： Implicit-explicit schemes spectral methods numerical relativity black holes

Charged quark stars in f(R,T)gravity

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Chinese Physics C 2022年第11期46卷 308-317页

作者： Juan M.Z.Pretel Takol Tangphati Ayan Banerjee Anirudh Pradhan Centro Brasileiro de Pesquisas Físicas Rua Dr.Xavier Sigaud150 URCARio de Janeiro CEP 22290-180RJBrazil theoretical and Computational Physics group Theoretical and Computational Science Center(TaCS)Faculty of ScienceKing Mongkut’s University of Technology Thonburi126 Prachauthid Rd.Bangkok 10140Thailand astrophysics and Cosmology Research Unit School of MathematicsStatistics and Computer ScienceUniversity of KwaZulu-NatalPrivate Bag X54001Durban 4000South Africa Centre for Cosmology Astrophysics and Space ScienceGLA UniversityMathura-281406Uttar PradeshIndia

Recent advances in nuclear theory and new astrophysical observations have led to the need for specific theoretical models applicable to dense-matter physics *** chromodynamics(QCD)predicts the existence of non-nucleonic degrees of freedom at high densities in neutron-star matter,such as quark *** a confining quark matter model,which consists of homogeneous,neutral 3-flavor interacting quark matter with O(m_(s)^(4))corrections,we examine the structure of compact stars composed of a charged perfect fluid in the context of f(R,T)*** system of differential equations describing the structure of charged compact stars has been derived and numerically solved for a gravity model with f(R,T)=R+2β*** simplicity,we assumed that the charge density is proportional to the energy density,namely,ρ_(ch)=αρ.It is demonstrated that the matter-geometry coupling constant β and charge parameter α affect the total gravitational mass and the radius of the star.

关键词： charged stars f(R T)gravity

Bianchi type I in f(T) gravitational theories

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Chinese Physics B 2016年第5期25卷 58-64页

作者： M I Wanas G G L Nashed O A Ibrahim Astronomy Department Faculty of Science Cairo University Cairo Egypt Centre for theoretical Physics The British University in Egypt El-Sherouk City Egypt Mathematics Department Faculty of Science Ain Shams University Cairo Egypt Egyptian relativity group (ERG) Giza Egypt

A tetrad field that is homogeneous and anisotropic which contains two unknown functions A（t） and B（t） of cosmic time is applied to the field equations of f（T）, where T is the torsion scalar, T = T~μ_（νρ）S_μ^（νρ）. We calculate the equation of continuity and rewrite it as a product of two brackets, the first is a function of f（T） and the second is a function of the two unknowns A（t） and B（t）. We use two different relations between the two unknown functions A（t） and B（t） in the second bracket to solve it. Both of these relations give constant scalar torsion and solutions coincide with the de Sitter one. So,another assumption related to the contents of the matter fields is postulated. This assumption enables us to drive a solution with a non-constant value of the scalar torsion and a form of f（T） which represents ΛCDM.

关键词： f(T) gravitational theory Bianchi type I special solutions

Chiral edge state coupling theory of transport in quantum anomalous Hall insulators

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 101-107页

作者： Rui Chen Hai-Peng Sun Bin Zhou Dong-Hui Xu Department of Physics Hubei UniversityWuhan 430062China Institute for theoretical Physics and astrophysics University of WurzburgWurzburg 97074Germany Departmentof Physicsand Chongqing Key Laboratory for Strongly Coupled Physics Chongqing UniversityChongqing 40044China Center of Quantum Materials and Devices Chongqing UniversityChongqing 400044China

The quantum anomalous Hall effect is characterized by a quantized Hall resistance with a vanishing longitudinal *** experiments reported the quantization of the Hall resistance,which is always accompanied by a non-vanishing longitudinal resistance that is several k?.Meanwhile,the non-vanishing longitudinal resistance exhibits a universal exponential decay with the increase in magnetic *** propose that the coupling of chiral edge states,which has not been properly evaluated in the previous theories,can give rise to the non-vanishing longitudinal *** coupling between the chiral edges states along the opposite boundaries can be assisted by magnetic domains or defects inside the sample bulk,which has been already identified in recent *** theory provides a potential mechanism to understand the experimental result in both magnetic topological insulator and moirésuperlattice systems.

关键词： quantum anomalous Hall effect quantum transport chiral edge state coupling

Generic phase portrait analysis of finite-time singularities and generalized Teleparallel gravity

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Chinese Physics C 2017年第12期41卷 133-154页

作者： W. El Hanafy G.G.L. Nashed Centre for theoretical Physics The British University in Egypt P.O. Box 43 El Sherouk City Cairo 11837 Egypt Mathematics Department Faculty of Science Ain Shams University Cairo 11566 Egypt Egyptian relativity group (ERG) Cairo University Giza 12613 Egypt

We analyze the four common types of finite-time singularity using a generic framework of the phase portrait geometric approach. This technique requires the Friedmann system to be written as a one-dimensional autonomous system. We employ a scale factor that has been used widely in the literature to realize the four finite- time singularity types, then we give a detailed discussion for each case showing possible novel models. Moreover, we show how different singularity types can play essential roles in different cosmological scenarios. Among several modified gravity theories, we show that the f（T） cosmology is compatible with the phase portrait analysis, since the field equations include Hubble derivatives only up to first order. Therefore, we reconstruct the f（T） theory which generates these phase portraits. We also perform a complementary analysis using the effective equation of state. Furthermore, we investigate the role of the torsion fluid in realizing the cosmic singularities.

关键词： inflation bounce big brake ACDM teleparallel gravity

Two-dimensional Parameter Relationships for W UMa-type Systems Revisited

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Research in Astronomy and astrophysics 2024年第1期24卷 51-58页

作者： Atila Poro Ehsan Paki Ailar Alizadehsabegh Mehdi Khodadadilori Selda Ranjbar Salehian Mahya Hedayatjoo Fatemeh Hashemi Yasaman Dashti Fatemeh Mohammadizadeh Astronomy Department of the Raderon AI Lab. BurnabyBCCanada Faculty of Electrical and Computer Engineering Department of PhotonicsUniversity of TabrizTabriz 51664Iran Department of Electrical Engineering Amirkabir University of TechnologyTehranIran Astronomy Students'Scientific Association University of TabrizTabriz 51664Iran Department of Physics Iran University of Science and TechnologyTehranIran Institute for the Intellectual Development(Kanoon) Astronomy GroupBojnordIran Department of Mechanical Engineering Amirkabir University of TechnologyTehranIran Aerospace Engineering Department Science and Research Branch of Islamic Azad UniversityTehranIran

Reviewing the empirical and theoretical parameter relationships between various parameters is a good way to understand more about contact binary *** this investigation,two-dimensional(2D)relationships for P–MV(system),P–L1,2,M1,2–L1,2,and q–Lratiowere *** sample used is related to 118 contact binary systems with an orbital period shorter than 0.6 days whose absolute parameters were estimated based on the Gaia Data Release 3 *** reviewed previous studies on 2D relationships and updated six parameter ***,Markov chain Monte Carlo and Machine Learning methods were used,and the outcomes were *** selected 22 contact binary systems from eight previous studies for comparison,which had light curve solutions using spectroscopic *** results show that the systems are in good agreement with the results of this study.

关键词： (stars:)binaries(including multiple):close stars:fundamental parameters methods:data analysis

Slim Discs with Varying Accretion Rates

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Chinese Physics Letters 2009年第4期26卷 275-277页

作者：焦承亮卢炬甫 Department of Physics and Institute of theoretical Physics and astrophysics Xiamen University Xiamen 361005

It was revealed in our previous studies that there exists a maximal possible accretion rate for slim discs with constant accretion rates because the correctly calculated vertical gravitational force can only gather some limited amount of accreted matter. Here we show that when the accretion rate is not constant and instead decreases with decreasing radius because of outflows, such that the amount of accreted matter is adjusted to be within the allowed limit, global slim disc solutions can be constructed even for the case that accretion rates at large radii apparently exceed the maximal possible value. This result further demonstrates that outflows seem to be unavoidable for accretion flows with large accretion rates at large radii.

关键词： gamma-ray bursts gamma-rays relativity

Modelling Moran Process with Network Dynamics for the Evolution of Cooperation

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Chinese Physics Letters 2009年第6期26卷 302-305页

作者：杨冬平林海吴晨旭帅建伟 Department of Physics and Institute of theoretical Physics and astrophysics Xiamen University Xiamen 361005

We introduce a simple model based on the Moran process with network dynamics. Using pair approximation, the cooperation frequencies at equilibrium states are deduced for general interactions. Three usual social dilemmas are discussed in the framework of our model. It is found that they all have a phase transition at the same value of cost-to-benefit ratio. For the prisoner＇s dilemma game, notably it is exactly the simple rule reported in the literature [Nature 441 （2006） 502]. In our model, the simple rule results from the parent-offspring link. Thus the basic mechanism for cooperation enhancement in network reciprocity is in line with the Hamilton rule of kin selection. Our simulations verify the analysis obtained from pair approximation.

关键词： gamma-ray bursts gamma-rays relativity