We have analyzed the sunspot and aurora data recorded in Go-Ryer-Sa. We have collected 35 records of sunspot observations for 46 days, and 232 records of auroral observations. To objectively estimate the periods of the solar activity appearing in these records a method of calculating the one-dimensional power spectrum from inhomogeneous data is developed, and applied to the sunspot and auroral data. We have found statistically significant 10.5 and 10 year periodicities in the distributions of sunspot and aurora records, respectively. These periods are consistent with the well-known solar activity cycle. There are indications of the long-term variations, but the period is not certain. We have also calculated the cross-correlations between the sunspot and auroral data. In particular, we have divided the aurora data into several subgroups to study their nature. We conclude that the historical records of strong auroral activity correspond to non-recurrent magnetic storms related to the sunspots. On the other hand, the records of weak auroral activity are thought to be related with the recurrent magnetic storms which occur frequently due to the coronal hole near the sunspot minimum.

We show that the low density regions of the matter distribution preserve the properties of the primordial density field better than the high density regions. We have performed a cosmological N-body simulation of large-scale structure formation in the standard CDM cosmology, and studied the evolution of statistics of under-density and over-density regions separately. The rank-order of the under-density regions is closer to the original one compared to that of the over-density regions. The under-density peaks (or voids) has moved less than over-density peaks (or dense clusters of galaxies) from their initial positions. Therefore, the under-density regions are more useful than the over-density regions in the study of the statistical property of the primordial density field.

We have found that the two-point correlation function of the APM clusters of galaxies has an amplitude much higher than that claimed by the APM group. As the richness limit increases from R = 53 to 80, the correlation length increases from 17.5 to 28.9 h-1Mpc. This indicates that the richness dependence of the APM cluster correlation function is also much stronger than what the APM group has reported. The richness dependence can be represented by a fitting formula ro = 0.53dc + 0.01, which is consistent with the Bahcall's formula ro = 0.4dc. We have tried to find the possible reason for discrepancies. However, our estimates for the APM cluster correlation function are found to be robust against variation of the method of calculation and of sample definition.

We have developed a cosmological N-body code which can simulate unprecedently large number of massive particles. This code is based on the Particle-Mesh scheme, and utilize the recent fast I/O devices to swap all variables. Using the new code we have simulated the formation and evolution of structures at high redshifts in the standard Cold Dark Matter (CDM) cosmogony. A simulation evolving 1024^3 particles on a 2048^3 mesh with the initial standard CDM power spectrum is being made. This is the first billion particle cosmological simulation with initial conditions representing the theoretical model over the widest range of space. A smaller, but still very large CDM simulation with 512^3 particles on a 1024^3 mesh has been completed. We have found that the galaxy-scale CDM halos with diameters of tens of kpcs undergo complete collapse before redshift 10. Our results clearly indicate that galactic and subgalactic structures have formed far before redshift 5 which is the present upper limit to the epoch of observed structures. We emphasize that the non-linear evolution of the galactic and subgalactic-scale structures starts as early as z ~ 50, and that cosmological simulations must start at such high redshifts. A high mass resolution is also indispensable to accurately represent the theoretical model in the initial conditions down to subgalactic scales, and to correctly study the subsequent formation and evolution of structures through hierarchical clustering.

We have identified the candidates for the primordial galaxies in the process of formation in the Hubble Deep Field (hereafter HDF). In order to select these objects we have removed objects brighter than 29-th magnitude in the HDF images and smoothed the maps with the Gaussian filters with the FWHM of 0.8' and 4' to obtain the difference maps. This has enabled us to find. very faint diffuse structures close to the sky level. Peaks are identified in the difference map for each of three HDF chips with three filters (F450W, F606W, and F814W). They have the apparent AB magnitudes typically between 29 and 31. The objects identified in different wavelengths filters have a strong cross-correlations. The correlation lengths are about 0.8'. This means that an object found in one filter can be also found as a peak within 0.8' separation in another filter, thus telling the reality of the identified objects. This angular scale is also the size of the primordial galaxies which have strong color fluctuations on their surfaces. Their large-scale distribution quite resembles that of nearby galaxies, supporting the idea that these objects are ancestors of the present bright galaxies forming at statistically high density regions. Inspections on individual objects show that these primordial galaxy candidates have tiny multiple glares embedded in diffuse backgrounds. Their radial light distributions are quite different from that of nearby bright galaxies. We may be now looking at the epoch of galaxy formation.

We have analyzed the content of the Korean stone star chart. Ch'on-Sang-Yul-Cha-Bun-Ya-Ji-Do(here-after Ch'on-Sang-Do). In the star map we have found 1468 stars, 4 more than the Chinese star catalog Bo-Chun-Ga. The four extra stars form a constellation, Jong Dae Boo. The map projection law used in the star chart is found to be the polar equtorial and equidistance projection. The linear distance of an object on Ch'on-Sang-Do from the center is linearly proportional to the north polar angular distance. We have found from a statistical analysis that most stars with declination lower than 50 are at positions representing the epoch of around the first century. On the other hand, stars near the north pole with declination higher than 50 are at the epoch of about 1300, which is close to the time the chart was engraved. This implies that the original Ko-Gu-Rye Dynasty's star chart has been revised by astronomers of Cho-Sun Dynasty. We have also shown that stars on Ch'on-Sang-Do are engraved in such a way that their area is linearly proportional to the visual magnitude.

We present a model that rotating primordial blackholes(PBHs) produced at the end of inflation generate the random, non-oriented primordial magnetic field. PBHs are copiously produced as the Universe completes the cosmic phase transition via bubble nucleation and tunneling processes in the extended inflation hypothesis. The PBHs produced acquire angular momentum through the mutual tidal gravitational interaction. For PBHs of mass less than 1013g, one can show that the evaporation (photon) luminosity of PBHs exceeds the Eddington limit. Thus throughout the lifetime of the rotating PBH, radiation flow from the central blackhole along the Kerr-geodesic exerts torque to ambient plasma. In the process similar to the Bierman's battery mechanism electron current reaching up to the horizon scale is induced. For PBHs of Grand Unified Theories extended inflation with the symmetry breaking temperature of TGUT ~1010 GeV, which evaporate near decoupling, we find that they generate random, non-oriented magnetic fields of ~10-11G on the last-scattering surface on (the present comoving) scales of ~O(10)Mpc.

Events of eclipses as well as other major astronomical events observable in the eastern sector of Asian continent are computed and checked with astronomical records of antiquity. Particular attention was given to two types of the events recorded in remaining records of Dangun Chosun Period (DCP): (1) concentration of major planets near the constellation of Nu-Sung ( β A r i e s ) and (2) a large ebb-tide. We find them most likely to have occurred in real time. i.e., when the positions of the sun, moon, and planets happen to be aligned in the most appropriate position. For solar eclipses data, however, we find among 10 solar eclipse events recorded, only 6 of them are correct up to months, implying its statistical significance is no less insignificant. We therefore conclude that the remaining history books of DCP indeed contains important astronomical records, thereby the real antiquity of the records of DCP cannot be disproved.