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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.
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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
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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.
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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.
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Dark matter
Vraštil, Michal ; Mészáros, Attila (advisor) ; Heyrovský, David (referee)
The dark matter constituting approximately 85% of the mass is an integral part of our universe. As many astronomical observations at different scales of space so the theoretical models show that there is more matter than we can see directly. This overview describes the major historical events and observational data from the time of Zwicky to the present leading to today's view on the dark matter. The paper further describes the cosmological implications of the presence of dark matter - its impact on the formation of structures in the universe and reflection of fluctuations in the cosmic background radiation. Here I describe possible candidates for dark matter - a small contribution of baryonic matter and the main candidates among non-baryonic matter. In addition to possible new particles explaining the missing mass I describe alternatives to the theory of gravity, which do not require any extra matter, in particular, I deal with a very successful theory of MOND. At the end I mention a brief overview of today's possibilities of direct or indirect observation of dark matter.
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Studium negaussovských světelných křivek pomocí Karhunenova-Loveho rozvoje
Greškovič, Peter ; Pecháček, Tomáš (advisor) ; Mészáros, Attila (referee)
We present an innovative Bayesian method for estimation of statistical parameters of time series data. This method works by comparing coefficients of Karhunen-Lo\`{e}ve expansion of observed and synthetic data with known parameters. We show one new method for generating synthetic data with prescribed properties and we demonstrate on a numerical example how this method can be used for estimation of physically interesting features in power spectra calculated from observed light curves of some X-ray sources.
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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.
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Statistical Analysis of the Observable Data of Gamma-Ray Bursts
Řípa, Jakub ; Mészáros, Attila (advisor) ; Münz, Filip (referee) ; Ramirez-Ruiz, Enrico Jorge (referee)
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.
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Statistical analysis of the gamma-ray bursts satellite data
Bystřický, Pavel ; Mészáros, Attila (advisor) ; Brož, Miroslav (referee)
In this thesis the Gamma-Ray Bursts (GRBs) are studied, the brightest explosions in the universe. GRBs have been observed since year 1967, but there are several unsolved problems. In the first chapter there is an introduction to the issue of GRBs, and the history of observations are briefly described. The Fermi satellite, the latest satellite devoted to gamma-ray burst observations is described in chapter two. Characteristics of the Fermi instruments are also described. The observed data of GRBs are characterized in the third chapter. The distribution of GRB durations, distances, and spectral hardnesses are described. The characteristics of long and short GRBs (distance, isotropy of distribution, metalicity dependence, isotropic energy) are described. A chance of the appearance of a GRB in the Milky Way is discussed. New Fermi observations are described too. Fourth chapter is about models of GRBs. The fireball and canonball models are described. Fifth chapter is focused on the exposure function of CGRO-BATSE, Fermi-GBM, Swift. I have created the exposure function for GBM on Fermi satellite. It is quite difficult, and I have assumed some simplified hypotheses. Information of the satellite's position, position of detectors on the Fermi satellite, have been found on the Fermi web pages and in the article...
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