Cosmic Microwave Background Anisotropy from Nonlinear Structures in Accelerating Universes (2008)
Sakai, Nobuyuki, Inoue, Kaiki Taro
We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving...
The universe out of a breathing bubble (2008)
Guendelman, Eduardo I., Sakai, Nobuyuki
We consider the model of a false vacuum bubble with a thin wall where the surface energy density is composed of two different components, "domain-wall" type and "dust" type, with opposite signs. We...
Stability of Q-balls and Catastrophe (2007)
Sakai, Nobuyuki, Sasaki, Misao
We propose a practical method for analyzing stability of Q-balls for the whole parameter space, which includes the intermediate region between the thin-wall limit and thick-wall limit as well as...
Dynamics of Gravitating Magnetic Monopoles (2007)
According to previous work on magnetic monopoles, static regular solutions are nonexistent if the vacuum expectation value of the Higgs field j is larger than a critical value j cr , which is of the...
Dinamic Monopoles And Spacetime Structure (2007)
According to previous work on magnetic monopoles, static regular solutions are nonexistent if the vacuum expectation value of the Higgs field j is larger than a critical value j cr , which is of the...
Production of Global Monopoles through the Nucleation of O(3) Bubbles (2007)
First-order cosmological phase transitions are considered in the models with an O(3)-symmetric scalar field, in the high temperature limit. It is shown that a global monopole can be produced at the...
Sakai, Nobuyuki, Okada, Yoshio, Tsuji, Takao
The serum levels of the carbohydrate antigen sialyl Lewis X (SLEX) increase in liver diseases (Sunayama T, Okada Y, Tsuji T., J Hepatol 1994; 19: 451-458). However, it is not known whether the...
The universe out of a monopole in the laboratory? (2006)
Sakai, Nobuyuki, Nakao, Ken-ichi, Ishihara, Hideki, Kobayashi, Makoto
To explore the possibility that an inflationary universe can be created out of a stable particle in the laboratory, we consider the classical and quantum dynamics of a magnetic monopole in the...
Optimal supply against fluctuating demand (2005)
Sakai, Nobuyuki, Kudoh, Hisanori
Sornette et al. claimed that the optimal supply does not agree with the average demand, by analyzing a bakery model where a daily demand fluctuates with a uniform distribution. In this note, we...
Properties of global monopoles with an event horizon (2003)
Tamaki, Takashi, Sakai, Nobuyuki
We investigate the properties of global monopoles with an event horizon. We find that there is an unstable circular orbit even if a particle does not have an angular momentum when the core mass is...
Generality of Topological Inflation (2003)
Many authors claimed that a large initial inhomogeneity prevents the onset of inflation and therefore inflation takes place only if the scalar field is homogeneous or appropriately chosen over the...
Wang, Lianzhou, Omomo, Yoshitomo, Sakai, Nobuyuki, Fukuda, Katsutoshi, Nakai, Izumi, Ebina, Yasuo, ...
Multilayer ultrathin films composed of exfoliated nanosheets of manganese oxide and poly(diallyldimethylammonium) (PDDA) ions have been fabricated onto various substrates via electrostatic...
Wang, Lianzhou, Omomo, Yoshitomo, Sakai, Nobuyuki, Fukuda, Katsutoshi, Nakai, Izumi, Ebina, Yasuo, ...
Multilayer ultrathin films composed of exfoliated nanosheets of manganese oxide and poly(diallyldimethylammonium) (PDDA) ions have been fabricated onto various substrates via electrostatic...
Cosmological Evolution of Black Holes in Brans-Dicke Gravity (2001)
Sakai, Nobuyuki, Barrow, John D.
We consider a modified ``Swiss cheese'' model in Brans-Dicke theory, and use it to discuss the evolution of black holes in an expanding universe. We define the black hole radius by the Misner-Sharp...
Evolution of Black Holes in Brans-Dicke Cosmology (2000)
Sakai, Nobuyuki, Barrow, John D.
We consider a modified ``Swiss cheese'' model in the Brans-Dicke theory, and discuss the evolution of black holes in the expanding universe. We define the black hole radius by the Misner-Sharp mass...
Topological Inflation in Supergravity (2000)
Kawasaki, M., Sakai, Nobuyuki, Yamaguchi, Masahide, Yanagida, T.
We investigate a topological inflation model in supergravity. By means of numerical simulations, it is confirmed that topological inflation can take place in supergravity. We also show that the...
Topological Defect Inflation (1999)
We address some issues of topological defect inflation. (1) We clarify the causal structure of an inflating magnetic monopole. The spacetime diagram shows explicitly that this model is free from the...
How Do Nonlinear Voids Affect Light Propagation ? (1999)
Sugiura, Norimasa, Nakao, Ken-ichi, Ida, Daisuke, Sakai, Nobuyuki, Ishihara, Hideki
Propagation of light in a clumpy universe is examined. As an inhomogeneous matter distribution, we take a spherical void surrounded by a dust shell where the ``lost mass'' in the void is compensated...
Peculiar Velocities of Nonlinear Structure: Voids in McVittie Spacetime (1999)
As a study of peculiar velocities of nonlinear structure, we analyze the model of a relativistic thin-shell void in the expanding universe. (1) Adopting McVittie (MV) spacetime as a background...
Causal Structure of an Inflating Magnetic Monopole (1999)
Sakai, Nobuyuki, Nakao, Ken-ichi, Harada, Tomohiro
We clarify the causal structure of an inflating magnetic monopole. The spacetime diagram shows explicitly that this model is free from ``graceful exit'' problem, while the monopole itself undergoes...
Kim, Yoonbai, Lee, Seung Joo, Maeda, Kei-ichi, Sakai, Nobuyuki
The decay of a metastable false vacuum by bubble nucleation is studied in the high temperature limit of the gauge theory in which an SO(3) gauge symmetry is spontaneously broken to an SO(2). The...
Topological inflation induced by a non-minimally coupled massive scalar field (1999)
Sakai, Nobuyuki, Yokoyama, Jun'ichi
We reanalyze cosmology of a non-minimally coupled massive scalar field which was originally discussed by Futamase and Maeda in the context of chaotic inflation scenario. We find a new type of...
Monopole Inflation in Brans-Dicke Theory (1998)
Sakai, Nobuyuki, Yokoyama, Jun'ichi, Maeda, Kei-ichi
According to previous work, topological defects expand exponentially without an end if the vacuum expectation value of the Higgs field is of the order of the Planck mass. We extend the study of...
Topic-prominence and L1 typological transfer in ESL learners' interlanguage / (1998)
Thesis (M.A.) -- Brigham Young University. Dept. of Linguistics, 1998.
Effect of Void Network on CMB Anisotropy (1997)
Sakai, Nobuyuki, Sugiyama, Naoshi, Yokoyama, Jun'ichi
We study the effect of a void network on the CMB anisotropy in the Einstein-de Sitter background using Thompson &Vishniac's model. We consider comprehensively the Sacks-Wolfe effect, the Rees-Sciama...
Production of Global Monopoles through the Nucleation of $O(3)$ Bubbles (1996)
Kim, Yoonbai, Maeda, Kei-ichi, Sakai, Nobuyuki
First-order cosmological phase transitions are considered in the models with an $O(3)$-symmetric scalar field, in the high temperature limit. It is shown that a global monopole can be produced at the...
Monopole-Bubble in Early Universe (1996)
Kim, Yoonbai, Maeda, Kei-ichi, Sakai, Nobuyuki
The nucleation and evolution of bubbles are investigated in the model of an $O(3)$-symmetric scalar field coupled to gravity in the high temperature limit. It is shown that, in addition to the...
Solitonic Island in the Bubble (1996)
Kim, Yoonbai, Maeda, Kei-ichi, Sakai, Nobuyuki
We review how the continuous symmetry can support a soliton inside a high-temperature bubble at the time of its nucleation. This solitonic island in disoriented phase remains stable during the growth...
Fluctuations of the Gravitational Constant Induced by Primordial Bubbles (1996)
We consider the classical fluctuations of the gravitational constant generated by bubbles in the inflationary universe. For extended inflation, we demonstrate numerically how and how large...
Dynamics of Gravitating Magnetic Monopoles (1995)
According to previous work on magnetic monopoles, static regular solutions are nonexistent if the vacuum expectation value of the Higgs field $\eta$ is larger than a critical value $\eta_{{\rm cr}}$,...
Dynamic Monopoles and Spacetime Structure (1995)
According to previous work on magnetic monopoles, static regular solutions are nonexistent if the vacuum expectation value of the Higgs field $\eta$ is larger than a critical value $\eta_{{\rm cr}}$,...
Bubbles with an O(3) Symmetric Scalar Field in Curved Spacetime (1995)
Sakai, Nobuyuki, Kim, Yoonbai, Maeda, Kei-ichi
We study the first-order phase transition in a model of scalar field with $O(3)$ symmetry coupled to gravity, and, in high temperature limit, discuss the existence of new bubble solution with a...
Dynamics of Topological Defects and Inflation (1995)
Sakai, Nobuyuki, Shinkai, Hisa-aki, Tachizawa, Takashi, Maeda, Kei-ichi
We study the dynamics of topological defects in the context of ``topological inflation" proposed by Vilenkin and Linde independently. Analysing the time evolution of planar domain walls and of global...
Junction Conditions of Friedmann-Robertson-Walker Space-Times (1993)
Sakai, Nobuyuki, Maeda, Kei-ichi
We complete a classification of junctions of two Friedmann-Robertson-Walker space-times bounded by a spherical thin wall. Our analysis covers super-horizon bubbles and thus complements the previous...