Constraints on RnR^n gravity from precession of orbits of S2-like stars: a case of a bulk distribution of mass

Here we investigate possible applications of observed stellar orbits around Galactic Center for constraining the R$^n$ gravity at Galactic scales. For that purpose, we simulated orbits of S2-like stars around the massive black hole at Galactic Center, and study the constraints on the R$^n$ gravity which could be obtained by the present and next generations of large telescopes. Our results show that R$^n$ gravity affects the simulated orbits in the qualitatively similar way as a bulk distribution of matter (including a stellar cluster and dark matter distributions) in Newton's gravity. In the cases where the density of extended mass is higher, the maximum allowed value of parameter $\beta$ in R$^n$ gravity is noticeably smaller, due to the fact that the both extended mass and $R^n$ gravity cause the retrograde orbital precession.Comment: 10 pages, 4 figures, accepted for publication in Advances in Space Researc

Good Governance and Institution Building as a Condition of EU Integration and Economic Growth

Institutions represent rules of behavior in a particular society, the limitations that a person has designed to shape interactions between people. Inclusive institutions promote the rule of law, maximize efficiency and social well-being and contribute to the achievement of higher rates of economic growth and represent key economic freedoms. Inclusive institutions provide security of private property, an impartial legal system and public services that provide equality in exchange and contracting, as well as citizens' participation in economic activities. Residents of countries with such type of institutions have access to political institutions, which gives them the opportunity to participate in the democratic process, to elect representatives of the authorities, change them, etc. Extractive institutions, as opposite to inclusive institutions, allow access to political power only to a privileged circle of people. The aim of this institutions is to subtract income and wealth from one social subgroup in favor of the other. The emergence, development and establishment of inclusive institutions is not a short process and it also implies the fulfillment of certain political prerequisites such as: the representation of parliamentary tradition and therefore political culture, compliance with laws and regulations, respecting private property rights, respecting state property rights, strong public opinion etc. Greater representation of inclusive institutions will certainly contribute to EU integration

Gravitational Redshift of Emission Lines in the AGN Spectra

The detection of gravitationally redshifted optical emission lines has been reported just for a few active galaxies. In this paper we give a short overview of studies that analyzed or exploited the detection of the gravitational redshift in optical AGN spectra. In addition, we tested the consistency of gravitational redshift as the physical origin of the redward shifts observed in their spectra using a sample of $\approx$ 50 Hamburg-ESO intermediate to high redshift quasars that are among the most luminous quasars known ($10^{47} \lesssim L \lesssim 10^{48}$ erg/s), and are expected to host very massive black holes. To this aim we modeled the line profile with accretion disk models around a black hole.Comment: 10 pages, 2 figures, 3 table

Constraining Scalar-Tensor gravity models by S2 star orbits around the Galactic Center

The aim of our investigation is to derive a particular theory among the class of scalar-tensor(ST) theories of gravity, and then to test it by studying kinematics and dynamics of S-stars around supermassive black hole (BH) at Galactic Center (GC). We also discuss the Newtonian limit of this class of ST theories of gravity, as well as its parameters. We compare the observed orbit of S2 star with our simulated orbit which we obtained theoretically with the derived ST potential and constrained the parameters. Using the obtained best fit parameters we calculated orbital precession of S2 star in ST gravity,and found that it has the same direction as in General Relativity (GR), but causes much larger pericenter shift.Comment: 13 pages, 1 table, 6 figures. Accepted for publication in Facta Universitatis: Series Phys. Chem. Tech. (Invited lecture at Balkan Workshop 2018

Distribution of radio spectral index over the Lupus loop

We use all-sky surveys at 408 and 1420 MHz with aim to investigate properties of the Galactic radio source Lupus Loop. We estimate the brightness temperature, surface brightness and radio spectral index of this supernova remnant using the method we have developed. The non-thermal nature of its radiation is confirmed, and also the distribution of spectral index over its area is given

Flux densities and spectral indices of Relaxed Double radio galaxy 3C 84

Here we study the flux densities distribution at 1380, 4908 and 15365 MHz, as well as the radio spectral index of 3C 84, a Double Radio source Associated with Galactic Nucleus (DRAGN). 3C 84 is the dominant giant elliptical galaxy in the Perseus cluster, and thus very interesting for our research. This famous radio galaxy Perseus A has Relaxed Double classification because it has the large halo, with the lack of its compact structure. We show its structure (using 2D and 3D flux density plot). Besides, we calculated the radio spectral index, which we then used to investigate the nature and mechanisms of its radiation. The obtained values of spectral indices indicated that the northern hotspot is dominated by synchrotron radiation, while in southern hotspot there are thermal and non-thermal radiations, depending on the studied frequency pairs.BPU11 : 11th International Conference of the Balkan Physical Union : Proceedings book; Aug 11 - Sep 1, 2022S02-AA Astronomy and Astrophysic

Relation between planning and realization of open spaces in New Belgrade super-blocks : case studies of block 45 and 70

During the postwar period, from the 1960s to the 1980s, very large area of today's New Belgrade was built using the concept of the Funtional city, which a lot of professionals consider as a successful example of modern urbanism. Still, with a change of socio-political situation in the Republic of Serbia during the 1990s and 2000s, a number of New Belgrade’s super-bloks started to be replanned. Having that in mind, this paper argues that there has been a substantial difference between planning intentions and real needs of the inhabitants, considering the treatment of open spaces inside the modernistic blocks. The main aim of this research is to show this potential conflict on the case studies of super-blocks number 45 and 70. After review of the plan making process, there will be shown some real needs of the local community that manifest themselves through open spaces, and comparative analyzes will be made. This research examines the question of the direction in which the process of planning should be addressed in order to include the real needs of the local community

Gravitational microlensing of AGN dusty tori

We investigated the gravitational microlensing of active galactic nucleus dusty tori in the case of lensed quasars in the infrared domain. The dusty torus is modeled as a clumpy two-phase medium. To obtain spectral energy distributions and images of tori at different wavelengths, we used the 3D Monte Carlo radiative transfer code SKIRT. A ray-shooting technique has been used to calculate microlensing magnification maps. We simulated microlensing by the stars in the lens galaxy for different configurations of the lensed system and different values of the torus parameters, in order to estimate (a) amplitudes and timescales of high magnification events, and (b) the influence of geometrical and physical properties of dusty tori on light curves in the infrared domain. We found that, despite their large size, dusty tori could be significantly affected by microlensing in some cases, especially in the near-infrared domain (rest-frame). The very long time-scales of such events, in the range from several decades to hundreds of years, are limiting the practical use of this method to study the properties of dusty tori. However, our results indicate that, when studying flux ratios between the images in different wavebands of lensed quasars, one should not disregard the possibility that the near and mid-infrared flux ratios could be under the influence of microlensing.Comment: 10 pages, 6 figures, 1 table, MNRAS accepted. V3: corrected values in Table

The shape of Fe Kα\alpha line emitted from relativistic accretion disc around AGN black holes

The relativistically broadened Fe K$\alpha$ line, originating from the accretion disc in a vicinity of a super massive black hole, is observed in only less than 50\% of type 1 Active Galactic Nuclei (AGN). In this study we investigate could this lack of detections be explained by the effects of certain parameters of the accretion disc and black hole, such as the inclination, the inner and outer radius of disc and emissivity index. In order to determine how these parameters affect the Fe K $\alpha$ line shape, we simulated about 60,000 Fe K $\alpha$ line profiles emitted from the relativistic disc. Based on simulated line profiles, we conclude that the lack of the Fe K$\alpha$ line detection in type 1 AGN could, be caused by the specific emitting disc parameters, but also by the limits in the spectral resolution and sensitivity of the X-ray detectors.Comment: Based on the talk presented Balkan Workshop BW2018 (10-14 June 2018, Ni\v{s}, Serbia), accepted for publishing in International Journal of Modern Physics A, 8 figures, 1 table, 15 page