In this study we investigate possible applications of observed S2 orbit around Galactic Center for constraining the Yukawa gravity at scales in the range between several tens and several thousands ...astronomical units (AU) to obtain graviton mass constraints. In our model we suppose that bulk distribution of matter (includes stellar cluster, interstellar gas distribution and dark matter) exists near Supermassive Black Hole (SMBH) in our Galactic Center. We obtain the values of orbital precession angle for different values of mass density of matter, and we require that the value of orbital precession is the same like in general relativity (GR). From that request we determine gravity parameter
λ
and the upper value for graviton mass. We found that in the cases where the density of extended mass is higher, the maximum allowed value for parameter
λ
is smaller and the upper limit for graviton mass is higher. It is due to the fact that the extended mass causes the retrograde orbital precession. We believe that this study is a very efficient tool to evaluate a gravitational potential at the Galactic Center, parameter
λ
of the Yukawa gravity model, and to constrain the graviton mass.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We use the Fundamental Plane of Elliptical Galaxies to constrain the so-called Hybrid Gravity, a modified theory of gravity where General Relativity is improved by further degrees of freedom of ...metric-affine Palatini formalism of
f
(
R
)
gravity. Because the Fundamental Plane is connected to the global properties of elliptical galaxies, it is possible to obtain observational constraints on the parameters of Hybrid Gravity in the weak field limit. We analyze also the velocity distribution of elliptical galaxies comparing our theoretical results in the case of Hybrid Gravity with astronomical data for elliptical galaxies. In this way, we are able to constrain the Hybrid Gravity parameters
m
ϕ
and
ϕ
0
. We show that the Fundamental Plane, i.e.,
v
c
/
σ
relations, can be used as a standard tool to probe different theories of gravity in the weak field limit. We conclude that Hybrid Gravity is able to explain elliptical galaxies with different stellar kinematics without the dark matter hypothesis.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We investigate the velocity distribution of elliptical galaxies in the framework of Non-local Gravity. According to this approach, it is possible to recover the fundamental plane of elliptical ...galaxies without the dark matter hypothesis. Specifically, we compare theoretical predictions for circular velocity in Non-local Gravity context with the corresponding values coming from a large sample of observed elliptical galaxies. We adopt the surface brightness, effective radius and velocity dispersion as structural parameters for the fundamental plane. As final result, it is possible to show that non-local gravity effects can reproduce the stellar dynamics in elliptical galaxies and fit consistently observational data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A knapsack problem based approach is proposed for computing the optimal allocation of buffer times.•The priority of each candidate is determined with respect to its delay sensitivity and delay ...impact to all other events.•The optimal amount of buffer for each minimum headway time is determined.
Reliability and punctuality of railway traffic are among the key performance indicators, which have a significant impact on user satisfaction. A way to improve the reliability and on-time performance in the timetable design stage is by improving the timetable robustness. In order to increase the robustness, most railway companies in Europe insert a fixed amount of buffer time between possibly conflicting events in order to reduce or prevent delay propagation if the first event occurs with a delay. However, this often causes an increase of capacity consumption which is a problem for heavily utilised lines. A sufficient amount of buffer time can therefore not be added between every two conflicting events. Thus, buffer times need to be allocated carefully to protect events with the highest priority. In this paper we consider the problem of increasing the robustness of a timetable by finding an optimal allocation of buffer times on a railway corridor. We model this resource allocation problem as a knapsack problem, where each candidate buffer time is treated as an object with the value (priority for buffer time assignment) determined according to the commercial and operational criteria, and size equal to its time duration. The validity of the presented approach is demonstrated on a case study from a busy mixed-traffic line in Sweden.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Here we present an overview of some of the most significant observational and theoretical studies of the broad Fe Kα spectral line, which is believed to originate from the innermost regions of ...relativistic accretion disks around central supermassive black holes of galaxies. The most important results of our investigations in this field are also listed. All these investigations indicate that the broad Fe Kα line is a powerful tool for studying the properties of the supermassive black holes (such as their masses and spins), space–time geometry (metric) in their vicinity, their accretion physics, probing the effects of their strong gravitational fields, and for testing the certain predictions of General Relativity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•We propose a model for station capacity determination, independent of a timetable.•The model uses two-stage optimization approach that minimizes total occupation time of a station.•The number of ...sets of compatible routes is optimized by a weighted graph vertex coloring approach.•The total follow-up time between the sets is minimized by a traveling salesman problem.•We verify the model and test it on six station layouts.
This study develops an optimization model for strategic decision-making in railway station design, enabling the comparison and selection of a station layout that maximizes the theoretical infrastructure capacity, completely independent of timetables. The model, using well-known combinatorial problems, such as the weighted vertex coloring problem and traveling salesman problem, identifies a route sequence that occupies a minimum amount of infrastructure and calculates the theoretical capacity. The model is tested on six different layouts for a station in the design phase, as well as on one fully operating station. The test results demonstrate the simplicity of implementing the model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The development of New Belgrade, initiated in the post-war period, was based on the Modernist concept of urban structure. The planned central zone was never built, but the local community places, as ...urban hubs for meeting and gathering, have been developed within the initially conceived open public spaces. Considering their importance for establishing and strengthening local communities, the article focuses on the development tendencies detected in emerging urban hubs of the residential Blocks 37 and 38. Unlike many other blocks of New Belgrade, which have been exposed to drastic changes of their original Modernist structure, their authentic setting have remained mostly intact since their construction in the 1970s. Therefore, they are selected as the examples of a new process of community planning which has followed the activities of place making. Triggered both by the changed patterns of use and the specificities of original spatial features, these changes also influence the local neighborhood while shifting the perception of the previously neglected open public spaces. The emerging hubs are analyzed on the level of networks, configuration and places, providing an insight into ongoing transformation of both the space and the local community.
The goal of this paper is to investigate the flux and spectral index distribution of FR II radio galaxy 4C 14.11. We focused on the distribution of flux and spectral indices over the lobes, as well ...as in their hot spots. For that purpose, we used publicly available observations of this radio galaxy given at 1450 and 8440 MHz. Particularly, we used Leahy’s Atlas of radio-emitting double radio sources, Jodrell Bank Centre for Astrophysics in Manchester, as well as NASA/IPAC Extragalactic Database. We found that the non-thermal (synchrotron) radiation dominates over the areas of the lobes. Distinction between hot spots and rest of the lobes are much smaller in the spectral index than in the flux. We also found that over the inner parts of both lobes, spectral index α is flat in average and significantly higher than 1.2, indicating that 4C 14.11 is old AGN.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper we use a modification of the Newtonian gravitational potential with a non-linear Yukawa-like correction, as it was proposed by C. Will earlier to obtain new bounds on graviton mass from ...the observed orbits of S-stars around the Galactic Center (GC). This phenomenological potential differs from the gravitational potential obtained in the weak field limit of Yukawa gravity, which we used in our previous studies. We also assumed that the orbital precession of S-stars is close to the prediction of General Relativity (GR) for Schwarzschild precession, but with a possible small discrepancy from it. This assumption is motivated by the fact that the GRAVITY Collaboration in 2020 and in 2022 detected Schwarzschild precession in the S2 star orbit around the Supermassive Black Hole (SMBH) at the GC. Using this approach, we were able to constrain parameter λ of the potential and, assuming that it represents the graviton Compton wavelength, we also found the corresponding upper bound of graviton mass. The obtained results were then compared with our previous estimates, as well as with the estimates of other authors.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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