#### From dark to dark: Anthropic selection of cosmological parameters and an analysis method for signals from cosmic reionization = 암흑에서 암흑으로: 인간 중심적 선택 효과와 우주 재이온화 시기의 신호 분석

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This thesis includes two independent works on dark energy and the cosmic dark ages. (1) Weinberg {\it et al.} calculated the anthropic likelihood of the cosmological constant $\Lambda$ using a model assuming that the number of observers is proportional to the total mass of gravitationally collapsed objects, with mass greater than a certain threshold at $t \to \infty$. We modify Weinbergs model in a way that the number of observers is proportional to the number of collapsed objects, with mass and time equal to certain preferred mass and time scales. Unlike Weinbergs model, the anthropic likelihood of the primordial density perturbation amplitude $Q$ from our model explains $Q_0$ well without any additional constraint. Furthermore, observers will be affected by the history of the collapsed object, and we introduce a method to calculate the anthropic likelihoods of $\Lambda$ and $Q$ from the mass history using the extended Press-Schechter formalism. In contrast to models using only a single mass constraint, the results from the models using the mass history are robust even if we allow both $\Lambda$ and $Q$ to vary. (2) We propose a topological analysis method of 21-cm signal using the 2D genus curve, a function defined as the difference of the number of hot regions and the number of cold regions, compared to a given temperature. We show that the 2D genus curve of the differential brightness temperature, $g_\mathrm{2D} (\delta T_\mathrm{b})$, by comparing to $g_\mathrm{2D}$ of the density fluctuation, $g_\mathrm{2D} (\delta T_\mathrm{b,n})$, clearly shows the evolution of the reionization process. We also show that the 2D genus topology method can effectively distinguish different reionization scenarios, especially with different source photon efficiency for a low-mass source $10^8 \lesssim M / M_\odot \lesssim 10^9$ and with different greatest ionized bubble size. In terms of the design of future detection, we show that observational beams insensitive to la...
Stewart, Ewan D.researcher유안 스튜어트researcher
Description
한국과학기술원 : 물리학과,
Publisher
한국과학기술원
Issue Date
2011
Identifier
466329/325007  / 020047999
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 물리학과, 2011.2, [ viii, 48p. ]

Keywords

Cosmic Reionization; Anthropic Principle; Cosmological Constant; Cosmology; 2D Genus Topology; 2차원 종수 함수 분석법; 우주 재이온화; 인간 중심적 원리; 우주 상수; 우주론

URI
http://hdl.handle.net/10203/47662