|
|
Determinating the cosmological omega factors with supernovae Ia
Rieb, Tomáš ; Mészáros, Attila (advisor) ; Jungwiert, Bruno (referee)
My thesis is an attempt to determine cosmological omega factors using the data measured during observations of the supernovae type Ia with cosmological redshift z 0,1. For the determination of omega factors I use the method of fi tting measured data in Hubble s diagram. I evaluate the ts by the 2-tests. The values of omega factors, coming out of the analyses as the most probable ones di ffer from the results which are published in the contemporary scienti c literature. The question which I am posing is, if it is correct to reject the cosmological models with a zero value of the cosmological constant. At the first sight statistical results of 2-test, which issue from my thesis, seem to be su fficient enough to reject these models. But the denial of the zero cosmological constant appears as ambivalent by detailed analysis of the occasions and reasons for it. As the basis for my analyses, I use the data collected by a number of scientifi c teams. I cannot succesfully fi t most of these data, because the dispersions of their positions in Hubble s diagrams are too large. I can conclude that the observations of the supernovae Ia alone are not satisfactory for a reliable determination of the cosmological omega factors.
|
|
| |
|
|
The cosmological constant on the non-cosmological scales
Liška, Andrej ; Mészáros, Attila (advisor) ; Kofroň, David (referee)
The cosmological constant Λ was first added to the gravitational field equations in 1917 by Albert Einstein. Einstein preferred the static universe, whereas field equations without the cosmological constant did not allow for such a scenario. A series of later observations mainly by Slipher, Lemaitre and Hubble showed the universe to be dynamic, which led to the cosmological constant being ne- glected from Einstein's field equations. In the early 1990s, it became clear that the expansion of the universe accelerates and the cosmological constant emerged in the field equations again, as an explanatory element. Based on a study by Perlmutter and Riess who observed distant type Ia supernovae, the cosmological constant is positive with a value of 10−56 cm−2 . The 2011 Nobel Prize was awarded for this discovery. Within the limit of weak gravitational fields and low velocities, Einstein's theory of gravitation must be reduced into Newtonian theory of gravity, the so-called Newtonian limit of Einstein equations. The full Einstein equations of the gravitational field, in the Newtonian limit, are not reduced exactly to Poisson's equation of Newtonian theory of the gravitational field. The Newtonian limit contains two additional terms with the cosmological constant, which the classical theory of gravity does not account for....
|
|
|
Hungarian shamanism and its elements in Hungarian folk tales
Adamovský, Vít ; Kolmanová, Simona (advisor) ; Mészáros, Andor (referee)
The presented bachelor thesis maps the phenomenon of Hungarian shamanism and then analyzes its elements in Hungarian folk tales. According to ethnographers of the 19th and 20th centuries, the ancient tradition of shamanism reached the territory of the former Hungary from the Siberian region, where the Hungarian ethnic group comes from. The central figure of the reconstructed Hungarian shamanism is considered to be the táltos, who, following the example of Siberian shamans, was to play the role of a healer, seer, spiritual leader, and a mediator between the human world, heaven, and the underworld in the society of that time. However, this concept is criticized by contemporary ethnographers, and the presence of a relic of Siberian shamanism in Europe is questioned. Nevertheless, these ideas occupy a firm place in Hungarian culture and mythology. The first chapter thematizes Siberian shamanism, which, unlike the Hungarian one, is documented in detail. The second part of my research describes a journey of the Hungarian ethnic group from the Finno-Ugric homeland, which is followed by a chapter devoted to problematic Hungarian shamanism of which fragments have been preserved in the folk culture, more precisely oral folk literature. The practical part of this bachelor thesis is based on the...
|
|
|
Statistical Analysis of the Observable Data of Gamma-Ray Bursts
Řípa, Jakub ; Mészáros, Attila (advisor)
Gamma-ray bursts are still not fully understood events. However, their exploration could pro- vide a useful tool for a better understanding of the early Universe because they belong to the most distant and violent objects that astronomers know. This thesis tries to bring more information about a so-called group of intermediate-duration bursts claimed by different authors employing dif- ferent data samples. Firstly, duration and spectral hardness properties of bursts from the Reuven Ramaty High-Energy Solar Spectroscopic Imager are statistically analysed. The obtained results bring a suspicion that these intermediate bursts gather into a separate group. Secondly, these bursts are investigated in more detail with respect to their spectral lags, peak count rates, red- shifts, supernova observations, and so forth. Thirdly, long-duration bursts with known redshifts and with derived pseudo-redshifts detected by The Burst and Transient Source Experiment, Swift and Fermi bursts with known redshifts, are used to study the cosmological effects on the observed flux and fluence distributions.
|
|
|
Survey of the basic cosmological discoveries from years 1910-1930
Liška, Andrej ; Mészáros, Attila (advisor) ; Křížek, Michal (referee)
Between 1910 and 1930 a large number of astronomical discoveries took place. Henrietta Swan Leavitt revealed the relationship between the luminosity and the period of Cepheids, which then bacame the indicators for distance de- termination in the universe. Based on this relation in 1925 Edwin Powell Hubble calculated the distance to our neighboring Galaxy M31. Tireless exploration of the nebulae by Vesto Melvin Slipher brought a very important ratio between the red and blue shifts, where the red ones clearly dominated. In 1927 Georges Edouard Lemaître derived Hubble's law from Einstein's field equations, indepen- dently on Alexander Alexandrovich Friedmann. Two years later Hubble definitely demonstrated the linear behavior between the red shift and the distance. 1
|
|
|
Classification of distances in cosmology
Křížek, Michal ; Mészáros, A.
In cosmology many different distances are defined: angular, comoving, Euclidean, Hubble, light-year, luminosity, Minkowski, parallax, proper motion, redshift, ... distance. There is not one single natural distance, since the universe is expanding, curved, and we look back in time. In this survey paper we will concentrate on geometrical interpretations of the above-mentioned distances.
|
|
|
Method of standard candles for determining distances in the Universe
Mádlová, Tereza ; Šolc, Martin (advisor) ; Mészáros, Attila (referee)
The aim of this bachelor's thesis is to enrich the reader's knowledge about methods of determining distances in the universe. This study is particularly focused on the history of the evolution of these methods, a physical descrip- tion of the problem and interim results. Primarily, this thesis deals with the method of standard candles. First, the main information necessary for study- ing the methods of determining distances in the universe is clarified. Then the thesis describes in detail the issue of important historical events and inventions which affected the evolution of these methods. Through these topics we obtain knowledge of this method, and the knowledge of the theory of the expansion of the universe as well. 1
|
|
|
Cosmological constant
Bjelka, Jakub ; Mészáros, Attila (advisor) ; Křížek, Michal (referee)
The aim of this work is concentration of the relevant knowledges from area history of the cosmological constant. Theory listed in time sequence show its origin, evolution and problems associated with it. In this work are commented static models which are made possible by the existence of a cosmological constant. Parameters obtained from experiments BAO (baryon acoustic oscillations) from Supernova Type Ia measurements (SNe) and from measurements of the cosmic microwave background (CMB) are, as the marginal conditions determined also. Furthermore, there are commented alternative solutions of the problem of cosmological constant in the form of a cyclic model or time variable of the cosmological "constant". In conclusion, there is mentioned the possibility of alternative to cosmological constant in the form of quintescence.
|
|
|
Statistické zpracování družicových dat gama záblesků družice Fermi
Pitňa, Alexander ; Mészáros, Attila (advisor) ; Řípa, Jakub (referee)
Gamma-ray bursts (GRBs) are one of the phenomena that still puzzle the astrophysi- cists. Due to their extreme luminosities, they are visible in cosmological distances. They could provide a tool for understanding the early Universe. This thesis focuses on the estimation of the total energy released by the GRBs, their luminosities and how these quantities depend on the redshift. For a sample of 28 long GRBs with known redshifts, a dependence of their total energies and luminosities on the redshift is found. The thesis further studied if this dependence is either an observational bias or a real astrophysical phenomenon. Firstly, proper use of k-correction revealed that it has lit- tle effect on the redshift dependence of these quantities. Secondly, a new approach has been proposed to investigate the redshift dependence of the luminosity function. Thirdly, selection effect has been found, when investigating the sample of bursts with known redshifts, implying a caution when combining data from different sources. All these efforts show that the observational bias can still explain the redshift dependence.
|
guest ::
