Astrophysics And Space Science Research Articles

Reconstruction of f(R) Gravity from Cosmological Unified Dark Fluid Model

In this work, we reconstruct the cosmological unified dark fluid model proposed previously by Elkhateeb (Astrophys Space Sci 363(1):7, 2018) in the framework of f(R) gravity. Utilizing the equivalence between the scalar-tensor theory and the f(R) gravity theory, the scalar field for the dark fluid is obtained, whence the f(R) function is extracted and its viability is discussed. The f(R) functions and the scalar field potentials have then been extracted in the early and late times of asymptotically de Sitter spacetime. The ability of our function to describe early time inflation is also tested. The early time scalar field potential is used to derive the slow roll inflation parameters. Our results of the tensor-to-scalar ratio r and the scalar spectral index ns\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n_s$$\\end{document} are in good agreement with results from Planck-2018 TT+TE+EE+lowE data for the model parameter n>2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n > 2$$\\end{document}.

Geant4 silver anniversary: 25 years enabling scientific production

This paper summarizes Geant4 contribution to scientific research overthe past 25 years through a scientometric analysis of the results with which it has beenassociated. The scientometric data collected from scholarly literature anddatabases are evaluated with methods pertaining to econometrics and ecology toquantify relevant traits, diversity and disparity in their scientific andgeographic distributions, and to identify statistically significant trends. Theanalysis reviews the contribution of Geant4 to the field — experimental particlephysics — that originally motivated its development and highlights its role inother research domains including nuclear physics and engineering, astrophysicsand space science, biomedical physics, archaeology and the cultural heritage.

Development of local density perturbation scheme in f(R) gravity to identify cracking points

In this work, the extension of concept of cracking in modified f(R) theory of gravity is presented for spherically symmetric compact objects. We develop general framework to observe the instabilities in self-gravitating spherical system through cracking with anisotropic inner matter configuration. For this purpose, the local density perturbation is applied on the hydrostatic equilibrium equation to identify cracking points/intervals. The physical viability of developed technique is tested on the data of three different stars namely 4U 1820-30, Her X-1 and SAX J1808.4-3658, presented in f(R) model developed in Zubair and Abbas (Astrophys Space Sci 361:342, 2016). It is concluded that these objects exhibit cracking in different interior regions and identification of cracking points refine the stability analysis of the system by extracting instabilities.

Thermodynamic analysis for Non-linear system (Van-der-Waals EOS) with viscous cosmology

The following paper is motivated by the recent works of Kremer [Gen Relativ Gravit 36(6):1423–1432, 2004; Phys Rev D 68(12):123507, 2003], Vardiashvili (Inflationary constraints on the van Der Waals equation of state, arXiv:1701.00748, 2017), Jantsch (Int J Mod Phys D 25(03):1650031, 2016), Capozziello (Phys Lett A 299(5–6):494–498, 2002) on Van-Der-Waals EOS cosmology. The main aim of this paper is to analyze the thermodynamics of a Non-linear system which in this case is Van-Der-Waals fluid EOS (Capozziello et al., Quintessence without scalar fields, arXiv:astro-ph/0303041, 2003). We have investigated the Van-Der-Waals fluid system with the generalized EOS as p=wleft( rho ,t right) rho +fleft( rho right) -3eta left( H,t right) H (Brevik et al., Int J Geom Methods Mod Phys 15(09):1850150, 2018). The third term signifies viscosity which has been considered as an external parameter that only modifies pressure but not the density of the liquid. The w(rho ,t) and f(rho )are the two functions of energy density and time that are different for the 3 types of Vander Waal models namely one parameter model, two parameters model and three parameters model (Ivanov and Prodanov, Eur Phys J C 79(2):118, 2019; Elizalde and Khurshudyan, Int J Mod Phys D 27(04):1850037, 2018). The value of EOS parameter (w_{EOS}) (Capozziello et al., Quintessence without scalar fields, arXiv:astro-ph/0303041, 2003; Obukhov and Timoshkin, Russ Phys J 60(10):1705–1711, 2018) will showdifferent values for different models. We have studied the changes in the parameters for different cosmic phases [Kremer, Phys Rev D 68(12):123507, 2003; Capozziello et al., Phys Lett A 299(5–6):494–498, 2002; Capozziello et al., Quintessence without scalar fields, arXiv:astro-ph/0303041, 2003]. We have also studied the thermodynamics and the stability conditions for the three models in viscous condition [Obukhov and Timoshkin, Russ Phys J 60(10):1705–1711, 2018; Panigrahi and Chatterjee, Gen Relativ Gravit 49(3):35, 2017; Panigrahi and Chatterjee, J Cosmol Astropart Phys 2016(05):052, 2016; Chakraborty et al., Evolution of FRW Universe in Variable Modified Chaplygin Gas Model, arXiv:1906.12185, 2019]. We have discussed the importance of viscosity (Brevik and Grøn, Astrophys Space Sci 347(2):399–404, 2013) in explaining accelerating universe with negative pressure (Panigrahi and Chatterjee, Gen Relativ Gravit 49(3):35, 2017).Finally, we have resolved the finite time future singularity problems [Brevik et al., The effect of thermal radiation on singularities in the Dark Universe, arXiv:2103.08430, 2021; Odintsov and Oikonomou, Phys Rev D 98(2):024013, 2018; Odintsov and Oikonomou, Int J Mod Phys D 26(08):1750085, 2017; Frampton et al., Phys Rev D 85(8):083001, 2012; Frampton et al., Phys Lett B 708(1–2):204–211, 2012; Frampton et al., Phys Rev D 84(6):063003, 2011] and discussed the thermodynamics energy conditions [Visser and Barcelo, Energy conditions and their cosmological implications. In: Cosmo-99, pp 98–112, 2000; Chattopadhyay et al., Eur Phys J C 74(9):1–13, 2014; Arora et al., Phys. Dark Universe 31:100790, 2021; Sharma and Pradhan, Int J Geom Methods Mod Phys 15(01):1850014, 2018; Sahoo et al., AstronomischeNachrichten 342(1–2):89–95, 2021; Yadav et al., Mod Phys Lett A 34(19):1950145, 2019; Sharma et al., Int J Geom Methods Mod Phys 17(07):2050111, 2020, Moraes and Sahoo, Eur Phys J C 77(7):1–8, 2017; Hulke et al., New Astron 77:101357, 2020; Singla et al., Gravit Cosmol 26(2):144–152, 2020; Sharif et al., Eur Phys J Plus 128(10):1–11, 2013] with those models.

Correction to: Orbit error characteristic and distribution of TLE using CHAMP orbit data

Correction to: Astrophys Space Sci (2018) 363:31 The first author’s third affiliation was missing in the original publication.

Retraction Note to: X-ray observations of PSR B0355+54 and its pulsar wind nebula (Astrophysics and Space Science, (2007), 308, 1-4, (309-316), 10.1007/s10509-007-9319-9)

Retraction Note to: Astrophys. Space. Sci. (2007) 308: 309–316https://doi.org/10.1007/s10509-007-9319-9 The authors have retracted this article (McGowan et al. 2007) which was unintentionally submitted in full length as part of a conference proceedings. However, the authors had already published the article in another journal (McGowan et al. 2006). Therefore this article is redundant. All authors agree with this retraction.

Correction to: The high energy emission of the Crab’s twin pulsar PSR J0540-6919 in the Large Magellanic Cloud

Correction to: Astrophys Space Sci (2019) 364:71 The third author’s name is incorrectly spelled in the original article. It is spelled correctly here.

Correction to: Constraints on Janus Cosmological model from recent observations of supernovae type Ia

Correction to: Astrophys Space Sci (2018) 363:139 The original article has been updated for copyright reasons with Fig. 1 and a too vague formulation intended to give credit to Farnes (2017) for the originally displayed figure. The sentences “JCM explains the confinement of galaxies and their flat rotation curves, as recently showed by Farnes (2017), see Fig. 1. Mysterious dark matter is no longer required, while the mainstream model does.” have been replaced by “JCM explains the confinement of galaxies and the shape of their rotation curves. As we showed in Petit et al. (2001), if one introduces a surrounding repellent negative matter environment, it gives larger rotation velocities at distance, see Fig. 1. Mysterious dark matter is no longer required, while the mainstream model does.” Figure 1 has been replaced. The figure caption of the earlier Fig. 1 has been replaced by “ Circular velocity, after Petit et al. (2001). This can be compared with results from numerical simulations by Farnes (2017)” The original article has been corrected.

Correction to: Soliton and shocks in pair ion plasma in presence of superthermal electron

Correction to: Astrophys Space Sci (2013) 345:291–296 There were typos in the last author’s name in the original publication. The name is correctly shown here.

Correction to: Investigation of recurrent EUV jets from highly dynamic magnetic field region

Correction to: Astrophys Space Sci (2017) 362:10 DOI There was an error in the sixth author’s name in the original publication. It is correctly shown here.

Effects of manifold correction methods on chaos indicators

The manifold approach of Nacozy et al. (Astrophys Space Sci 14:40–51, 1971), the approximate velocity correction method of Wu et al. (Astron J 133:2643–2653, 2007), and the velocity scaling method of Ma et al. (New Astron 13:216–223, 2008a) are some of the available manifold correction methods. They have been highly successful at maintaining invariant integrals in two-body problems and the Sun–Jupiter–Saturn system. This paper discusses their efficiency on chaos indicators. Because the planar circular restricted three-body problem involves the Jacobi constant $$C_\mathrm{j}$$ and chaotic phenomena, it is preferable to check the numerical performances of manifold corrections. First, we find that a low-order algorithm combined with manifold corrections can greatly improve the precision of the Jacobi constant $$C_\mathrm{j}$$ . Then, numerical experiments show that these manifold correction methods have the same performance in Poincare sections, Lyapunov exponents, fast Lyapunov indicators, smaller alignment indices, and relative finite time Lyapunov indicators. Moreover, manifold corrections not only allow for the use of larger step sizes compared to low-order algorithms without correction but also save substantial computation time compared to the high-order algorithm RKF7(8). In particular, the velocity scaling method of Ma et al. (2008a) lends itself to practical application in long-term integration.

Thermodynamics and holography of tachyon cosmology

Recently, we have investigated the dynamics of the universe in tachyon cosmology with non-minimal coupling to matter (Farajollahi et al. in Mod Phys Lett A 26(15):1125–1135, 2011; Phys Lett B 711(3–4)15:225–231,2012; Phys Rev D 83:124042, 2011; JCAP 10:014, 20112011; JCAP 05:017, 2011). In particular, for the interacting holographic dark energy (IHDE), the model is studied in Farajollahi et al. (Astrophys Space Sci 336(2):461–467, 2011). In the current work, a significant observational program has been conducted to unveil the model’s thermodynamic properties. Our result shows that the IHDE version of our model better fits the observational data than $$\Lambda $$ CDM model. The first and generalized second thermodynamics laws for the universe enveloped by cosmological apparent and event horizon are revisited. From the results, both first and generalized second laws, constrained by the observational data, are satisfied on cosmological apparent horizon.In addition, the total entropy is verified with the observation only if the horizon of the universe is taken as apparent horizon. Then, due to validity of generalized second law, the current cosmic acceleration is also predicted.

The role of astronomy and space sciences in Arab societies and cultures

AbstractAstronomy, Astrophysics and Space Sciences (AASS) play an effective rôle in Sciences, Technology and Community Development. Unfortunately, a small percentage of this knowledge is actually used in teaching at schools, universities and other academic institutions in Arab countries. The challenge is to provide effective professional development for AASS educators and researchers at all levels, from elementary school to university.There is an urgent need for a better communication channels among Arab astronomers and space scientists nowadays. In this respect, the best choice is to identify in the vast cultural heritage of the Arab basin, particularly in astronomy. Building modern and good observatories, planetariums and research centres in the region jointly by Arab astronomers and space scientists is essential and will be an excellent step towards developing AASS. The aim of this paper is to show the importance of the formal and informal astronomical research and education, giving examples of possible astronomical projects, and comments of the experiences that have been carried out in a few Arab Countries. We show as well the importance of the Astronomical Societies in developing Science and Technology in the fields of AASS, and the role of these societies on the community and the country development.

Maximum growth rate of magnetoatmospheric instabilities. II. A Hilbert space approach

For pt.I, see Astrophys Space Sci. vol.47, L.5 (1977). An upper bound is derived on the growth rates of instabilities occurring in media with restoring forces due to compressibility, buoyancy and magnetic fields (a magnetoatmosphere). The magnetic field considered is horizontal but arbitrarily varying in the vertical direction. The formalism used is based on the concept of an energy inner product in Hilbert space.