• Title/Summary/Keyword: cosmological term

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CONSTRAINTS ON A-DECAYING COSMOLOGY FROM OBSERVATIONAL POINT OF VIEW

  • KOMIYA ZEN;KAWABATA KIYOSHI;HIRANO KOICHI;BUNYA HIROSHI;YAMAMOTO NAOTAKA
    • Journal of The Korean Astronomical Society
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    • v.38 no.2
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    • pp.157-160
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    • 2005
  • To constrain the values of the model parameters for the cosmological models involving the time-decaying $\Lambda$ term, we have computed sets of theoretical predictions for the N-m relation of galaxies as well as the CMB angular power spectrum: three types of variation, viz., ${\Lambda}{\propto} T^{-1},\;a^{-m}$, and $H^n$ are thereby assumed following Overduin & Cooperstock (1998), although we concentrate here on the discussion of the results obtained from the first type. Our results for the N-m relation indicate that the observed excess of the galaxy counts N in the faint region beyond the blue apparent magnitude 24 can be reasonably well accounted for with the value of ${\iota}$ in the range between 0.2 and 1. Furthermore, a comparison of our computational results of the CMB spectra with the observational data shows that the models with a mild degree of the $\Lambda$ term decay, viz., with the value of ${\iota}{\le}$0.4, are favorable. In this case, the age of our universe turns out to be larger than or equal to 14 Gyr, the lower limit inferred from some Uranium datings.

HALO SPIN PARAMETER IN COSMOLOGICAL SIMULATIONS

  • Ahn, Jieun;Kim, Juhan;Shin, Jihye;Kim, Sungsoo S.;Choi, Yun-Young
    • Journal of The Korean Astronomical Society
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    • v.47 no.2
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    • pp.77-86
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    • 2014
  • Using a cosmological ${\Lambda}CDM$ simulation, we analyze the differences between the widely-used spin parameters suggested by Peebles and Bullock. The dimensionless spin parameter ${\lambda}$ proposed by Peebles is theoretically well-justified but includes an annoying term, the potential energy, which cannot be directly obtained from observations and is computationally expensive to calculate in numerical simulations. The Bullock's spin parameter ${\lambda}^{\prime}$ avoids this problem assuming the isothermal density profile of a virialized halo in the Newtonian potential model. However, we find that there exists a substantial discrepancy between ${\lambda}$ and ${\lambda}^{\prime}$ depending on the adopted potential model (Newtonian or Plummer) to calculate the halo total energy and that their redshift evolutions differ to each other significantly. Therefore, we introduce a new spin parameter, ${\lambda}^{\prime\prime}$, which is simply designed to roughly recover the value of ${\lambda}$ but to use the same halo quantities as used in ${\lambda}^{\prime}$. If the Plummer potential is adopted, the ${\lambda}^{\prime\prime}$ is related to the Bullock's definition as ${\lambda}^{\prime\prime}=0.80{\times}(1+z)^{-1/12}{\lambda}^{\prime}$. Hence, the new spin parameter ${\lambda}^{\prime\prime}$ distribution becomes consistent with a log-normal distribution frequently seen for the ${\lambda}^{\prime}$ while its mean value is much closer to that of ${\lambda}$. On the other hand, in case of the Newtonian potential model, we obtain the relation of ${\lambda}^{\prime\prime}=(1+z)^{-1/8}{\lambda}^{\prime}$; there is no significant difference at z = 0 as found by others but ${\lambda}^{\prime}$ becomes more overestimated than ${\lambda}$ or ${\lambda}^{\prime\prime}$ at higher redshifts. We also investigate the dependence of halo spin parameters on halo mass and redshift. We clearly show that although the ${\lambda}^{\prime}$ for small-mass halos with $M_h$ < $2{\times}10^{12}M_{\odot}$ seems redshift independent after z = 1, all the spin parameters explored, on the whole, show a stronger correlation with the increasing halo mass at higher redshifts.

Scalar Perturbation and Stability of a New Wormhole in Einstein-Born-Infeld Gravity (아인슈타인-본-인펠트 중력 이론에서 새로운 웜홀의 스칼라장 섭동과 안정성)

  • Kim, Jin Young
    • New Physics: Sae Mulli
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    • v.68 no.11
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    • pp.1262-1267
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    • 2018
  • We introduce a new method to construct wormholes without adopting exotic matters in Einstein-Born-Infeld gravity with a negative cosmological constant. Contrary to the conventional method, the throat of the wormhole is located at the point where the metric solutions are joined smoothly. Thus, exotic matters are not needed to sustain the throat. We consider the behavior of a minimally coupled scalar field to study the stability of the new wormhole. If we define the quasinormal mode of the scalar field as the purely ingoing flux at the throat of the wormhole, the stability of wormhole can be discussed in analogy with the argument that we use for the stability of a black hole. Because an analytic solution can not be found, we suggest a formalism to find quasinormal modes numerically. The crucial difference from the black hole case is that the coefficient of the second-order derivative term of the radial equation is expanded from n = -1, which is contrary to the black hole case where it is expanded from n = 0.

The Characteristics of 'Podeok (布德 Spreading Virtue)' in Daesoon Jinrihoe (대순진리회의 '포덕'개념의 특징)

  • Lee, Bong-ho;Park, Yong-cheol
    • Journal of the Daesoon Academy of Sciences
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    • v.32
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    • pp.77-108
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    • 2019
  • The purpose of this paper is to clarify the characteristics of 'Podeok' in Daesoon Jinrihoe. The term Podeok can cause some misunderstanding as the same word Deok (德 virtue) has long been used in the Eastern Tradition. In other words, for most people who are used to traditional thought, Podeok may be conflated with the similar word 'Deok (virtue)' as used within Confucianism. People who are familiar with Confucian culture might thereby misunderstand the term Podeok as an aspect of Confucian moral ethics, or they could misconstrue Daesoon Jinrihoe as having appropriated and misused Confucian ideas. Furthermore, there are other problems that could arise if people compare Daesoon Jinrihoe's 'Podeok' with 'Deok (virtue)' as used by Laozi. While Deok in Laozi's usage represents the ability of an individual who can exercise his or her rationality with excellence, Deok in Daesoon Jinrihoe indicates the idea of actualizing Mutual Beneficence and the conditions that enable Mutual Beneficence. If one understands Deok as used by Laozi to contain the meaning of Mutual Beneficence, then it is possible to think that the two tradition share a similar meaning of Deok as Podeok in Daesoon Jinrihoe pursues Mutual Beneficence as its ultimate value. In order to preemptively correct these misunderstandings, I need to clarify how the idea of Deok was born out of traditional thought and what meanings it embodies. Additionally, it is necessary to examine how it became meaningful in Confucianism, and how it was criticized and ascribed new meanings in Laozi's thought. Through these clarification, it will become clear that Deok originally indicated a religious ritual that the king of the Zhou Dynasty performed after receiving the heavenly mandate and assuming rule over the nation. Later, this idea was transformed into a moral virtue and norm by Confucius. This moral virtue and norm was criticized by Laozi as an unnatural form of control as it was understood by Laozi as a teleological argument justifying whether or not lives were to be saved or sustained based on the perceived merits of each individual. On the contrary, Deok in Daesoon Jinrihoe and traditional thought stand on a totally different theological bases. Deok in Daesoon Jinrihoe is a means to practice and realize the truth of the earthly paradise of the Later World and the truth of Mutual Beneficence which were posited to the world through Kang Jeungsan's Works of Haewon (grievance resolution) that resolved the pattern of mutual conflict that characterized the Former World. Therefore, the idea of Podeok in Daesoon Jinrihoe gains completion only on the premises of Haewon Sangsaeng (resolution of grievances for mutual beneficence) and Boeun Sangsaeng (reciprocation of favors for mutual beneficence), and the way to practice Podeok is to practice Haewon Sangsaeng and Boeun Sangsaeng. In addition, the subordinate virtues such as loyalty, filial piety, and faithfulness that exist within Daesoon Jinrihoe's religious practice are not same as those of traditional thought. They are new concepts of virtues drawn from the cosmological laws of Daesoon Jinrihoe. To be specific, the virtues of Daesoon Jinrihoe are not rules that create discrimination and mutual conflict, but are instead ethical rules established upon the basis of Heaven and Earth having been newly organized, and thus, they will bring virtuous concordance, harmonious union, and mutual beneficence. The idea of 'Podeok' in Daesoon Jinrihoe can be understood as a religious practice that requires doctrinal understanding and tangible practice in daily life of followers. In other words, it is not the same Deok of earlier traditional thought in East Asia, but is instead a religious truth by which practitioners realize the truth of Sangje's Works of Haewon in human world as they practice Haewon Sangsaeng and Boeun Sangsaeng.

A Study on Dosu Theory in Daesoon Thought (대순사상의 도수론(度數論) 연구)

  • Park, In-gyu
    • Journal of the Daesoon Academy of Sciences
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    • v.28
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    • pp.207-241
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    • 2017
  • In the scripture of Daesoon Jinrihoe, the expression 'Dosu (度數)' is frequently used and Jeungsan, Jeongsan, and Wudang also left behind many teachings related to Dosu. In this paper, the concept of Dosu is analyzed in detail and the achievement of an in-depth understanding of the concept of Dosu is attempted. The term Dosu is often used in traditional literature. In the classics, Dosu was used to mean institutions, standards, rules, law, figures, and the laws of heavenly bodies. In other words, Dosu is used to mean the laws of astronomy and the norms of human society. This meaning is expanded and used as the principle of the universe and nature. This concept of Dosu is related to the mathematical cosmological understanding of numbers as the principle of the universe. This type of mathematical cosmology was systematized by Shao Yong (邵雍). In the Joseon Dynasty, Seo Gyungduk (徐敬德) accepted it positively, and it thereby became an influential trend in Korean thought. In the world view of Daesoon thought, there exists the view that numbers as a principle of the universe, and of course this world view is connected to mathematical cosmology. In Daesoon thought, the concept of Dosu is based on the concept of traditional Dosu and adds an additional meaning which connects it to the Reordering of the Universe (Cheonjigongsa). Also, Dosu is used to mean the process of changing the principles and laws of cosmos through Jeungsan's Reordering of the Universe. It is especially the case that discourse about Dosu is widely used when describing the Reordering of the Universe. Jeungsan corrected, reorganized, and adjusted Dosu, as well as establishing new Dosu. Jeongsan, who succeeded Jeungsan, followed the Reordering of the Universe by Jeungsan, and also realized Dosu. In other words, Jeongsan acted and practiced according to the Dosu that had been enacted by Jeungsan. Also, Dosu means the process of the transformation of principle according to the Reordering of the Universe, and Wudang used the concept of Dosu to describe the historical process of Daesoon Jinrihoe. This means that the foundation of Mugeukdo, the change to Taegukdo, the establishment of Daesoon Jinrihoe, and the contruction of Yeoju headquarters are episodes in a divine history carried out through Dosu. Through this discourse, Daesoon Jinrihoe asserts a legitimacy that distinguishes itself from other sects, and believers can be inspired by the sacred meaning that they are participating in the Dosu of heaven and earth. This empowers their devotion and sincerity.