We have developed the four-dimensional digital universe theater at which we can visualize the observational data and theoretical models of astronomical objects stereoscopically. The astronomical objects cover all scales of the universe from the solar system to the large-scale structure of the universe. We have also produced the three-dimensional movies of various astronomical processes based on the results of computer simulations. We plan to distribute all the products of this project through the internet.

This paper summarizes the recent progress made by our group at Seoul National University on studies of the evolution and formation of distant galaxies. Various research projects are currently underway, which include: (i) the number density of distant early-type galaxies (z < 1); (ii) the optical-NIR color gradient of nearby early-type galaxies; (iii) J - K-selected Extremely Red Objects (EROs) in field (CDF-S) and the cluster environment; and (iv) the Lyman-break galaxies in the Spitzer First Look Survey (FLS) field. These works will constrain the mass evolution and the star formation history of galaxies in different environments, and the results will serve as useful contraints on galaxy formation models.

The temperature (T) and entropy (S) fields of baryonic gas, or intergalactic medium (IGM), in the ACDM cosmology are analyzed using simulation samples produced by a hybrid cosmological hydrodynamic/N-body code based on the weighted essentially non-oscillatory scheme. We demonstrate that, in the nonlinear regime, the dynamical similarity between the IGM and dark matter will be broken in the presence of strong shocks in the IGM. The heating and entropy production by the shocks breaks the IGM into multiple phases. The multiphase and non-Gaussianity of the IGM field would be helpful to account for the high-temperature and high-entropy gas observed in groups and clusters with low-temperature IGM observed by Lyα forest lines and the intermittency observed by the spikes of quasi-stellar object's absorption spectrum.

Recently, claims have been made of the detection of 'warm-hot' gas in the intergalactic medium. Kaastra et al. (2003) claimed detection of ~ 106K material in the Coma Cluster but studies by Arnaud et al. (2001), and our analysis of the Chandra observations of Coma (Vikhlinin et al. 2001), find no evidence for a 106 K gas in the cluster. Finoguenov et al. (2003) claimed the detection of 3 X 106 gas slightly off-center from the Coma Cluster. However, our analysis of ROSAT data from this region shows no excess in this region. We propose an alternative explanation which resolves all these conflicting reports. A number of studies (e.g. Robertson et al., 2001) have shown that the local interstellar medium undergoes charge exchange with the solar wind. The resulting recombination spectrum shows lines of O VII and O VIII (Wargelin et al. 2004). Robertson & Cravens (2003) have .shown that as much as 25% of the Galactic polar flux is heliospheric recombination radiation and that this component is highly variable. Sporadic heliospheric emission could account for all the claims of detections of 'warm-hot' gas and explain the conflicts cited above.

We use simulations of large-scale structure formation to study the build-up of magnetic fields (MFs) in the intergalactic medium. Our basic assumption is that cosmological MFs grow in a magnetohy-drodynamical (MHD) amplification process driven by structure formation out of a magnetic seed field present at high redshift. This approach is motivated by previous simulations of the MFs in galaxy clusters which, under the same hypothesis that we adopt here, succeeded in reproducing Faraday rotation measurements (RMs) in clusters of galaxies. Our ACDM initial conditions for the dark matter density fluctuations have been statistically constrained by the observed large-scale density field within a sphere of 110 Mpc around the Milky Way, based on the IRAS 1.2-Jy all-sky redshift survey. As a result, the positions and masses of prominent galaxy clusters in our simulation coincide closely with their real counterparts in the Local Universe. We find excellent agreement between RMs of our simulated galaxy clusters and observational data. The improved numerical resolution of our simulations compared to previous work also allows us to study the MF in large-scale filaments, sheets and voids. By tracing the propagation of ultra high energy (UHE) protons in the simulated MF we construct full-sky maps of expected deflection angles of protons with arrival energies E = 1020 eV and 4 X 1019 eV, respectively. Accounting only for the structures within 110 Mpc, we find that strong deflections are only produced if UHE protons cross galaxy clusters. The total area on the sky covered by these structures is however very small. Over still larger distances, multiple crossings of sheets and filaments may give rise to noticeable deflections over a significant fraction of the sky; the exact amount and angular distribution depends on the model adopted for the magnetic seed field. Based on our results we argue that over a large fraction of the sky the deflections are likely to remain smaller than the present experimental angular sensitivity. Therefore, we conclude that forthcoming air shower experiments should be able to locate sources of UHE protons and shed more light on the nature of cosmological MFs.

The current state and future prospects of ultra high energy cosmic ray physics are reviewed. These cosmic rays with energies well above 1018 eV are messengers of an unknown extremely high-energy universe.

X-ray observations of galaxy clusters have played an important role in cosmology, especially in determining the cosmological density parameter and the fluctuation amplitude. While they represent the bright side of the universe together with the other probes including the cosmic microwave background and the Type Ia supernovae, the resulting information clearly indicates that the universe is dominated by dark components. Even most of cosmic baryons turns out to be dark. In order to elucidate the nature of dark baryons, we propose a dedicated soft-X-ray mission, DIOS (Diffuse Intergalactic Oxygen Surveyor). Recent numerical simulations suggest that approximately 30 to 50 percent of total baryons at z = 0 take the form of the warm-hot intergalactic medium (WHIM) with 105K < T < 107K which has evaded the direct detection so far. The unprecedented energy resolution (~ 2eV) of the XSA (X-ray Spectrometer Array) on-board DIGS enables us to identify WHIM with gas temperature T = 106 ~ 107K and overdensity δ = 10 ~ 100 located at z < 0.3 through emission lines of OVII and OVIII. In addition, WHIMs surrounding nearby clusters are detectable with a typical exposure time of a day, and thus constitute realistic and promising targets for DIOS.

예이츠는 일생에 걸쳐 그의 문학과 그의 신비주의적 관심을 함께 연결시키려고 노력해왔으며 이는 사후의 세계와 우주의 섭리, 천국과 지옥의 실체 등 인간이 인식하지 못하는 것들에 대한 지적 호기심이며 창조적 탐구의 과정이었다. 이런 신비한 것에 대한 관심의 직접적인 접촉은 물론 블레이크적인 접근이었지만 그 뿌리를 거슬러 올라가면 크게 몇 가지로 분류되는데 이는 철학적 접근, 밀교적 접근, 아일랜드의 신화전설, 낭만주의적 접근, 신학적 접근, 그리고 이 논문에서 언급된 고대 기독교적 접근 등이 그것이다. 기독교적 접근이라고 분류되는 것은 성경에 기초한 교조적인 해석이 아니라 어느 정도 신비주의적으로 기독교의 전통에 따라 보이지 않는 것들, 즉 사후의 영적 경험과 천국과 지옥의 존재의 증명 시도를 의미한다. 예이츠의 기독교 신비주의에 영향을 끼친 두 신학자는 스웨덴보리와 보엠이 있다. 예이츠는 스웨덴보리로부터 주로 사후의 세계에 대해 영향을 받고 있다. 비록 스웨덴보리가 기독교의 교리에서 벗어나지 못했다는 약점에도 불구하고 사후세계의 존재인식과 인간과 신, 혹은 우주가 통신한다는 개념들은 예이츠의 인간영혼의 불멸성과 거대기억의 이론에 직접적인 근거가 된다. 그의 중심사상은 자연계와 영계의 통신이며 이는 우주와 개인, 신과 인간, 사후의 세계와 현세, 귀신과 사람간의 연결이며 합일이다. 영적인 세계는 천당이나 지옥이 아니라 그 중간의 세계이며 죽은 영혼들이 윤회로 다시 태어나거나, 혹은 최종의 목적지에 도달하기 전 잠시 머무는 임시영역이다. 예이츠는 이 영역에서 아니마 문디가 정화되고 거대기억이 형성된다고 보았다. 따라서 이 영적인 세계에서는 우주와 인간의 영혼이 서로 통신하며 실제로 교류할 수 있다는 것이다. 보엠은 좀 더 인간에 관심을 가지고 있다. 그의 인간과 신의 합일사상이 블레이크의 신성인간이며 예이츠의 황금새벽의 이상형이다. 우주의 질서와 조화를 강조한 보엠은 예이츠에게 시적 상상력이 신성과 같은 단계이며 시인은 마치 영매처럼 우주와 영혼, 즉 인간의 세계와 신의 세계를 볼 수 있는 능력을 가진 견자(seer)이며 연결할 수 있는 통신자(correspondences)라는 것을 말해주고 있다.

Cosmological hydrodynamic simulations of large scale structure in the universe have shown that accretion shocks and merger shocks form due to flow motions associated with the gravitational collapse of nonlinear structures. Estimated speed and curvature radius of these shocks could be as large as a few 1000 km/s and several Mpc, respectively. According to the diffusive shock acceleration theory, populations of cosmic-ray particles can be injected and accelerated to very high energy by astrophysical shocks in tenuous plasmas. In order to explore the cosmic ray acceleration at the cosmic shocks, we have performed nonlinear numerical simulations of cosmic ray (CR) modified shocks with the newly developed CRASH (Cosmic Ray Amr SHock) numerical code. We adopted the Bohm diffusion model for CRs, based on the hypothesis that strong Alfven waves are self-generated by streaming CRs. The shock formation simulation includes a plasma-physics-based 'injection' model that transfers a small proportion of the thermal proton flux through the shock into low energy CRs for acceleration there. We found that, for strong accretion shocks, CRs can absorb most of shock kinetic energy and the accretion shock speed is reduced up to 20%, compared to pure gas dynamic shocks. For merger shocks with small Mach numbers, however, the energy transfer to CRs is only about 10-20% with an associated CR particle fraction of 10-3. Nonlinear feedback due to the CR pressure is insignificant in the latter shocks. Although detailed results depend on models for the particle diffusion and injection, these calculations show that cosmic shocks in large scale structure could provide acceleration sites of extragalactic cosmic rays of the highest energy.

In the framework of the C-gauge condition for the perturbed variables and the linear approximation for the anisotropy of the spacetime, we studied the formulae for the Sachs-Wolfe effect in dust filled and perturbed Bianchi type I universe model. The results were compared with those of the flat Friedmann model.

We describe the formation of large-scale inhomogeneous structure of expa-nding Universe on the basic of two components system-usual nonrelativistic particles and dark matter, with taking into account their interaction.

In the standard theory of the large scale structure formation, matter accretes onto high density perturbations via gravitational instability. Collision less dark matter forms caustics around such structures, while collisional baryonic matter forms accretion shocks which then halt and heat the infalling gas. Here we discuss the characteristics. roles, and observational consequences of these accretion shocks.