Journal of the Korean Physical Society

pISSN 0374-4884 eISSN 1976-8524
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< PreviousNext >J. Korean Phy. Soc. 2006; 49(9(2)): 697~0
  • 2006-08-15

    The History of Reionization

    Li-Zhi Fang
    J. Korean Phy. Soc. 2006; 49(9(2)): 697

    Abstract : The 3-K temperature of the cosmic microwave background shows that baryon matter in the present universe should be very cold if the evolution of baryon matter is always in (quasi)-thermal equilibrium. However, the observed sky shows that in the present universe, the baryon matter, which is mostly hydrogen and helium gas, is actually hot. Therefore, the baryon matter must have undergone a non-equilibrium transition from neutral to ionized gas. This is called the cosmic reionization because the hydrogen and helium gases were in an ionized state before the decoupling between radiation and baryon matter. In the standard model of the universe, the reionization is considered to be caused by the first generations of luminous objects, which are the sources of UV background radiation that reionized the cosmic gas. New observations indicate that the transition from dark ages (cold gas) to a transparent epoch (ionized gas) is complicated. This paper will briefly review the observations and the theories for the chronology of cosmic dark ages: when the universe warmed up? when the reionization occurred? when the universe became transparent? when the evolution of cosmic matter entered into the nonlinear and non-thermal region?

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  • 2006-08-15

    Relativistic Gyratons

    Valeri P. Frolov
    J. Korean Phy. Soc. 2006; 49(9(2)): 706

    Abstract : We study the gravitational field of a spinning radiation beam-pulse (a gyraton) in a higher dimensional spacetime. We show that the vacuum Einstein equations for gyratons reduce to two linear problems in Euclidean space. We obtain and discuss the solutions for relativistic gyratons and consider special examples.

  • 2006-08-15

    The Lifetime of the Universe

    Don N. Page
    J. Korean Phy. Soc. 2006; 49(9(2)): 711

    Abstract : Current observations of the fraction of dark energy and a lower limit on its tension, coupled with an assumption of the non-convexity of the dark energy potential, are used to derive a lower limit of 26 billion years for the future age of the universe. Conversely, our ordered observations, coupled with an assumption that observers are smaller than the universe, are used to argue for an upper limit of about $e^{10^{50}}$ years if the universe eventually undergoes power-law expansion and an upper limit of only about $10^{60}$ years left for our universe if it continues to expand exponentially at the current rate.

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  • 2006-08-15

    Effective Lagrangian of Quantum Electrodynamics

    Remo Ruffini and She-Sheng Xue
    J. Korean Phy. Soc. 2006; 49(9(2)): 715

    Abstract : From the Euler-Heisenberg formula, we calculate the exact real part of the one-loop effective Lagrangian of quantum electrodynamics in a constant electromagnetic field and determine its strong-field limit.

  • 2006-08-15

    Equations of Motion and Initial and Boundary Conditions for Gamma-ray Burst

    C. L. Bianco, R. Ruffini, G. V. Vereshchagin and S.-S. Xue
    J. Korean Phy. Soc. 2006; 49(9(2)): 722

    Abstract : We compare and contrast the three different approaches to the optically thick adiabatic phase of Gamma-ray Burst(GRB) all the way to transparency. Special attention is given to the role of the rate equation in self-consistently solving the rate equation with the relativistic hydrodynamic equations. The works of Shemi and Pirancite{1990ApJ...365L..55S}, Piran, Shemi and Narayancite{1993MNRAS.263..861P}, M'{e}sz'{a}ros, Laguna and Reescite{1993ApJ...415..181M} and Ruffini, Salmonson, Wilson and Xuecite{1999A&A...350..334R,2000A&A...359..855R} are compared and contrasted. The roles of the baryonic loading in these three treatments are pointed out. The constraints on initial conditions for the fireball produced by an electro-magnetic black hole are obtained

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  • 2006-08-15

    On the Equilibrium of Two Charged Masses in General Relativity

    V. A. Belinski
    J. Korean Phy. Soc. 2006; 49(9(2)): 732

    Abstract : In the exact relativistic equilibrium conditions, the Reissner-Nordstrom black hole and a charged spinning particle (represented by the Kerr-Newman naked singularity solution) were found to be in the rest with respect to each other. The problem was solved analytically by using the inverse scattering method by which the exact solutions for the metric and the electromagnetic potentials were obtained. In the framework of this approach, that is, when both objects can be represented as solitons, the equilibrium is shown to be possible only when both of them are critically charged ({it i.e.}, the charge is equal to the mass).

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  • 2006-08-15

    Relativistic Radiation Hydrodynamic Equations in Cylindrical Coordinates

    Myeong-Gu Park
    J. Korean Phy. Soc. 2006; 49(9(2)): 736

    Abstract : In many astrophysical systems such as accretion disks and jets, radiation interacts with relativistically moving matter. With applications to such systems in mind, I use the covariant tensor conservation laws to derive special relativistic, time-dependent, three-dimensional energy and momentum equations for matter and radiation in cylindrical coordinates. The equations can be conveniently applied to various radiation hydrodynamic processes with cylindrical symmetry. Radiation moments, like the radiation energy density, flux, and pressure, are defined in the comoving (with the flow) frame first and then transformed to the corresponding covariant quantities. The interaction between matter and radiation is also described in the comoving frame while the equations are represented in coordinates that are fixed with respect to the central object. As a concrete example, the relativistic equations of motion for a cylindrical gas flow interacting with a spherically symmetric radiation field are presented.

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  • 2006-08-15

    Nonequilibrium Backreaction on a Moving Charge and Mirror in Quantum Fields

    Jen-Tsung Hsiang, Da-Shin Lee and Chun-Hsien Wu
    J. Korean Phy. Soc. 2006; 49(9(2)): 742

    Abstract : Backreaction on a nonrelativistic moving charge and mirror under the influence of quantum fields is studied. We employ the closed-time-path formalism to obtain the influence functional by tracing out quantum fields. The respective semiclassical Langevin equation is derived and can be used to describe the stochastic behavior on its mean trajectory with a self-consistent backreaction. In particular, when backreaction dissipation and fluctuations are taken into account, the corresponding fluctuation-dissipation theorem obtained from the first-principles derivation must be fulfilled. The implications of the results from solving the semiclassical Langevin equation are discussed

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  • 2006-08-15

    Hydrodynamics and Global Structure of Rotating Schwarzschild Black Holes

    Soon-Tae Hong and Sung-Won Kim
    J. Korean Phy. Soc. 2006; 49(9(2)): 748

    Abstract : Exploiting a rotating Schwarzschild black hole metric, we study the hydrodynamic properties of a perfect fluid whirling inward toward a black hole along a conical surface. On the equatorial plane of the rotating Schwarzschild black hole, we derive the radial equations of motion with effective potentials and the Euler equation for a steady-state axisymmetric fluid. Moreover, a numerical analysis is performed to figure out the effective potentials of the particles on the rotating Schwarzschild manifolds in terms of the angular velocity, the total energy and the angular momentum per unit rest mass. Higher dimensional global embeddings are also constructed inside and outside the event horizon of the rotating Schwarzschild black hole

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  • 2006-08-15

    Cosmological Acceleration with a Wormhole

    Sung-Won Kim
    J. Korean Phy. Soc. 2006; 49(9(2)): 755

    Abstract : In this paper, we study the accelerating cosmological model with a static traversable wormhole. In this model, the phantom energy is considered as the engine of the acceleration of the universe. It is shown that the time to the `Big Rip', by using the phantom energy, will be delayed for a sufficient wormhole distribution.

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October, 2020
Vol.77 No.8

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Journal of the Korean Physical Society

pISSN 0374-4884 eISSN 1976-8524