In this thesis the relative spectral energy density of stochastic primordial gravitational waves is investigated. Decoupling of Standard Model particles and neutrino free-streaming affect the...Show moreIn this thesis the relative spectral energy density of stochastic primordial gravitational waves is investigated. Decoupling of Standard Model particles and neutrino free-streaming affect the expansion history of the universe and thus leave characteristic signatures on the amplitude of the gravitational wave spectrum. Adding extra light or heavy particles damps the spectrum at frequencies before the particle decouples. Including an extra neutrino species amplifies the spectrum at larger wave numbers, but damps it at shorter wave numbers. Measuring these primordial gravitational waves reveals the thermal history of the universe. One possible non-standard thermal history is early matter domination due to the inflaton. It is shown that, in this cosmology, the end of early matter domination and beginning of the radiation era depend linearly on the reheating temperature.Show less
The collapse of the Soviet Union in 1989 marked a turning point for Eastern European nations, triggering a wave of democratic revolutions. This shift from communist governance to democracy was...Show moreThe collapse of the Soviet Union in 1989 marked a turning point for Eastern European nations, triggering a wave of democratic revolutions. This shift from communist governance to democracy was marked by numerous obstacles, notably the influence wielded by former communist elites, commonly referred to as the nomenklatura. This thesis examines the impact of the nomenklatura on the post-communist political environments and privatization processes of Bulgaria and Poland between 1989 and 2001. Both countries, influenced to varying extents by Soviet ideology, embarked on divergent paths toward democracy and economic liberalization. The thesis investigates how the nomenklatura, entrenched in positions of power, sought to maintain their political relevance and exploit state resources. Through a multidisciplinary analysis drawing from academic literature and primary sources, the study evaluates the strategies employed by the nomenklatura to adapt to democratic structures, their influence on post-communist political systems, and their role in the privatization of public resources. The results provide a deeper understanding of the lasting impact of the nomenklatura on Bulgaria and Poland's political and economic trajectories during the pivotal transitional period. This analysis offers valuable perspectives on the challenges encountered during democratization and economic reform in post-communist societies.Show less
This thesis discusses the human security of women in Okinawa, as they live alongside US military bases, through a critical feminist analysis of Japan-US security agreements. Ultimately, this thesis...Show moreThis thesis discusses the human security of women in Okinawa, as they live alongside US military bases, through a critical feminist analysis of Japan-US security agreements. Ultimately, this thesis concludes that the security of women in Okinawa is deemed secondary to both Japan's national interests and the US' national interests, and, thus, the security agreements between these two countries pose an active risk to the everyday security of women in Okinawa.Show less
The intergalactic medium (IGM) contains most of the baryonic matter of the Universe and serves as a suitable environment for probing the thermal history of the Universe. The crucial moment in IGM...Show moreThe intergalactic medium (IGM) contains most of the baryonic matter of the Universe and serves as a suitable environment for probing the thermal history of the Universe. The crucial moment in IGM evolution is the Epoch of Reionization, corresponding to the transition from neutral to ionized IGM. However, due to the observational limitations, this period is still not well understood. In this thesis, we focus on constraining IGM thermal history by using Lyman-alpha forests data. This method is applicable in a wide range of temperatures, densities, and ionization fractions of cosmic gas at z about 2 − 5. Observations show that the longitudinal flux power spectrum of the Lyman-α forest exhibits a cut-off at small scales. This phenomenon is caused by thermal Doppler broadening, peculiar velocities along the line of sight (LOS), Hydrogen pressure smoothing, and warm dark matter. The first two effects act only along LOS, while the last two affect all spatial directions. To separate the one-dimensional and three-dimensional effects, we used the method of close quasar pairs, which is based on studying the correlations between Lyman-alpha forests of close quasar pairs. We used the Kolmogorov-Smirnov test to analyze the differences between distributions of phase difference, which characterizes correlations between Lyman-alpha forests. The calculations were performed for various thermal histories, parameters characterizing IGM, LOS separations, and wavenumbers, and accounting for different effects (Doppler broadening and peculiar velocities). Our results indicate that this method can distinguish various thermal histories regardless of the IGM thermal state and one-dimensional effects. Moreover, at separations of the order of pressure broadening, there is a prominent feature caused by different influences of pressure smoothing at large and small scales. In addition, this simple and powerful approach has the potential to distinguish scenarios with warm dark matter.Show less
This study examines how the obsession with education affects the total fertility rate in South Korea. Among many factors, educational expenses weigh heavy when it comes to deciding to have another...Show moreThis study examines how the obsession with education affects the total fertility rate in South Korea. Among many factors, educational expenses weigh heavy when it comes to deciding to have another child. This study shows how education has been a means of social mobility throughout Korea’s history, how traces of this are still visible in contemporary South Korea, and how educational developments during the last century have caused private educational expenses to rise significantly. The results show that the societal preoccupation with status and education brings about excessive educational expenditures, causing parents to hold off on having a child or to give up on having another child completely, and thus lowering the total fertility rate.Show less
The adoption of UNSC Resolution 2375 and 2397 in 2017 marked the intended beginning of the end for North Korea’s lucrative labour exports, to dissuade the country from continuing its nuclear...Show moreThe adoption of UNSC Resolution 2375 and 2397 in 2017 marked the intended beginning of the end for North Korea’s lucrative labour exports, to dissuade the country from continuing its nuclear weapons programmes. However, incongruent outcomes after the repatriation deadline (December 22, 2019) pose the question of how effective sanctions targeting overseas labour have been in practice. Two empirical case studies analyse disruptions and continuities in North Korean overseas labour in (1) Russia as a whole by using visa issuance statistics, and (2) in the restaurant sector, using online review data, to gain insight into the sanctions’ effects. The findings of the first study suggest that Russia has altered its way of registering DPRK workers, rather than banning the phenomenon. Similarly, the second study shows that onethird of the North Korean overseas restaurants with online reviews is still operational far beyond the deadline. These are concentrated in China, Russia and Laos, while more distant countries have mostly closed the restaurants in connection with the sanctions. Overall, despite tangible effects, and keeping in mind hindrances posed by the Covid-19 pandemic, the effectiveness of the sanctions is most substantially undermined by China and Russia.Show less