Chang-Hwan Lee

Pusan National University, Tsau-liang-hai, Busan, South Korea

Are you Chang-Hwan Lee?

Claim your profile

Publications (51)178.43 Total impact

  • Hans A. Bethe, Gerald E. Brown, Chang-Hwan Lee
    Hans Bethe and his Physics. 01/2006;
  • Source
    Hong-Jo Park, Chang-Hwan Lee, Gerald E. Brown
    [show abstract] [hide abstract]
    ABSTRACT: We discuss the problem of mass, noting that meson masses decrease with increasing scale as the dynamically generated condensate of “soft glue” is melted (Brown/Rho scaling). We then extend the Bielefeld LGS (Lattice Gauge Simulation) color-singlet interaction computed for heavy quarks in a model-dependent way by including the Ampére law velocity–velocity interaction. Parameterizing the resulting interaction in terms of effective strength of the potential and including screening, we find that the masses of π, σ, ρ and A1 excitations, 32 degrees of freedom in all, go to zero (in the chiral limit) as T→Tc essentially independently of the input quark (thermal) masses in the range of 1–2 GeV, calculated also in Bielefeld. We discuss other LGS which show bound states, which we interpret as our chirally restored mesons, for T>Tc.
    Nuclear Physics A 12/2005; · 1.53 Impact Factor
  • Source
    Chang-Hwan Lee, Gerald E. Brown
    [show abstract] [hide abstract]
    ABSTRACT: Double neutrons are especially important because they give most accurate informations on the masses of neutron stars. Observations on double neutron stars show that all masses of the neutron stars are below 1.5$\msun$. Furthermore, two neutron stars in a given double pulsar are nearly equal in mass. With hypercritical accretion, we found that the probability of having companion mass $>1.5\msun$ is larger than 90%, while there is no observations on such systems. We believe that those companions with masses higher than $1.5\msun$ went into black holes, which is consistent with our preferred maximum neutron star mass $M_{NS}^{max} \approx 1.5\msun$ due to the kaon condensation. In this work, we point out that the black-hole neutron star binaries are 10 times more dominant than double neutron star binaries. As a result, black-hole, neutron star binaries can increase the LIGO detection rate by a factor 20.
    11/2005;
  • Source
    Gerald E. Brown, Chang-Hwan Lee, Mannque Rho
    [show abstract] [hide abstract]
    ABSTRACT: We construct the nature of the matter found in RHIC when its temperature has dropped down close to, and below, $T_c$. Just above $T_c$ it is composed of extremely strongly bound quark-antiquark pairs forming chirally restored mesons of the quantum numbers of the $\pi, S, \rho$ and $a_1$ with very small size and zero energy and just below $T_c$, it is composed of mesons of the same quantum numbers with zero mass. We invoke infrared slavery for the former and the vector manifestation (VM) of hidden local symmetry for the latter. As the temperature drops below $T_c$, the strongly bound quark-antiquark pairs are ejected into what is basically a region of "hadronic freedom" in which the interactions are zero. Experimental evidences for this are seen in the STAR data.
    08/2005;
  • Source
    G. E. Brown, Chang-Hwan Lee, Mannque Rho
    [show abstract] [hide abstract]
    ABSTRACT: The hidden local symmetry effective theory, Wilsonian matched to QCD at a matching scale near the chiral scale $\sim 4\pi f_\pi$ as formulated by Harada and Yamawaki, presents a scenario drastically different from the standard scenario of heavy-ion collisions in that as the temperature approaches the critical temperature $T_c$ of chiral restoration from below, the mass of the vector mesons and their widths go to zero in the chiral limit or nearly zero otherwise, proportionally to some power of the quark condensate at what is called "vector manifestation (VM) fixed point". This scenario makes a striking prediction that as the fire-ball expands and cools from $T_c$ down toward the freezeout temperature $T_{freezeout}$ in heavy ion collisions, what we call "hadronic freedom" sets in in which hadrons do not interact or barely interact. We suggest that this scenario is testable at RHIC and as a specific example, we provide an astonishingly simple explanation in terms of the vector manifestation suitably extended to include axial-vector mesons for the anomalously large $\rho^0/\pi^-$ ratio measured in peripheral collisions by STAR. Comment: 4 pages, no figures
    07/2005;
  • Source
    Gerald E. Brown, Chang-Hwan Lee, Mannque Rho
    [show abstract] [hide abstract]
    ABSTRACT: Combining the recent experimental indications of density dependence in the pion decay constant $f_\pi^\star$ and the $\omega$ meson mass $m_\omega^\star$ and the discovery of $S^0 (3115)$ and other "strange nuggets" with the vector manifestation of chiral symmetry in hidden local symmetry proposed by Harada and Yamawaki, we show that the mechanism responsible for dense strangeness nuggets can be related to that responsible for kaon condensation in neutron-star matter. We suggest that this relation assures kaon condensation at a density $\sim$ three times nuclear matter density which supports the Brown-Bethe scenario for the $M_{\rm NS}^{max} \simeq 1.5\msun$. This low $M_{\rm NS}^{\rm max}\sim 1.5\msun$ has major consequences in astrophysics, especially for the merging rate of compact stellar objects.
    05/2005;
  • [show abstract] [hide abstract]
    ABSTRACT: We consider the strangeness-conserving effective weak chiral Lagrangian based on the nonlocal chiral quark model from the instanton vacuum. We incorporate the effect of the strong interaction by the gluon into the effective Lagrangian. The effect of the Wilson coefficients on the weak pion-nucleon coupling constant is discussed briefly.
    12/2004: pages 105-105; · 2.04 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The main objective of this work is to explore the evolution in the structure of the quark-anti-quark bound states in going down in the chirally restored phase from the so-called ``zero binding points'' Tzb to the full (unquenched) QCD critical temperature Tc at which the Nambu-Goldstone and Wigner-Weyl modes meet. In doing this, we adopt the idea recently introduced by Shuryak and Zahed for charmed c¯c, light-quark q¯q mesons π,σ,ρ,A1 and gluons that at Tzb, the quark-anti-quark scattering length goes through ∞ at which conformal invariance is restored, thereby transforming the matter into a near perfect fluid behaving hydrodynamically, as found at RHIC. We show that the binding of these states is accomplished by the combination of (i) the color Coulomb interaction, (ii) the relativistic effects, and (iii) the interaction induced by the instanton-anti-instanton molecules. The spin-spin forces turned out to be small. While near Tzb all mesons are large-size nonrelativistic objects bound by Coulomb attraction, near Tc they get much more tightly bound, with many-body collective interactions becoming important and making the σ and π masses approach zero (in the chiral limit). The wave function at the origin grows strongly with binding, and the near-local four-Fermi interactions induced by the instanton molecules play an increasingly more important role as the temperature moves downward toward Tc.
    Nuclear Physics A 07/2004; 740:171-194. · 1.53 Impact Factor
  • Source
    Gerald E. Brown, Chang-Hwan Lee, Mannque Rho
    [show abstract] [hide abstract]
    ABSTRACT: In the hadronic sector of relativistic heavy ion physics, the ρ⇆2π reaction is the strongest one, strong enough to equilibrate the ρ with the pions throughout the region from chemical freezeout to thermal freezeout when free-particle interactions (with no medium-dependent effects) are employed. Above the chiral restoration temperature, only ρ's and π's are present, in that the chirally restored A1 is equivalent to the ρ and the mesons have an SU(4) symmetry, with no dependence on isospin and negligible dependence on spin. In the same sense the σ and π are “equivalent” scalars. Thus the chirally restored ρ⇆2π exhaust the interspecies transitions. We evaluate this reaction at Tc and find it to be much larger than below Tc, certainly strong enough to equilibrate the chirally restored mesons just above Tc. When emitted just below Tc the mesons remain in the Tc+ε freezeout distribution, at least in the chiral limit because of the Harada–Yamawaki “vector manifestation” that requires that mesonic coupling constants go to zero (in the chiral limit) as T goes to Tc from below. Our estimates in the chiral limit give deviations in some particle ratios from the standard scenario (of equilibrium in the hadronic sector just below Tc) of about double those indicated experimentally. This may be due to the neglect of explicit chiral symmetry breaking in our estimates. We also show that the instanton molecules present above Tc are the giant multipole vibrations found by Asakawa, Hatsuda and Nakahara and of Wetzorke et al. in lattice gauge calculations. Thus, the matter formed by RHIC can equivalently be called: chirally restored mesons, instanton molecules, or giant collective vibrations. It is a strongly interacting liquid.
    Nuclear Physics A 05/2004; · 1.53 Impact Factor
  • Chang-Hwan Lee, Gerald E. Brown
    [show abstract] [hide abstract]
    ABSTRACT: We discuss the possibility that the soft X-ray transient GRS1915 + 105 evolved from a binary similar to V4641Sgr (XTEJ1819 - 254) by conservative mass-transfer, and estimate the possible mass-transfer rates during the evolution. The results indicate that the high mass-transfer rates could explain the high luminosities in ultraluminous X-ray sources. Although the high mass-transfer rates during evolution are accompanied by high luminosities, we find that much of the transferred matter may sweeps accompanying radiation in an adiabatic inflow of super-Eddington accretion. We suggest that soft X-ray transients with evolved companions (initial companion mass > 3 Modot), e.g. GRS 1915 + 105, can be ultraluminous X-ray sources if they are seen through their beaming axis.
    Publications- Astronomical Society of Japan 04/2004; · 2.44 Impact Factor
  • Source
    Gerald E. Brown, Chang-Hwan Lee, Mannque Rho
    [show abstract] [hide abstract]
    ABSTRACT: The main objective of this work is to explore the evolution in the structure of the quark-antiquark bound states in going down in the chirally restored phase from the so-called "zero binding points" $T_{zb}$ to the QCD critical temperature $T_c$ at which the Nambu-Goldstone and Wigner-Weyl modes meet. In doing this, we adopt the idea recently introduced by Shuryak and Zahed for charmed $\bar c c$, light-quark $\bar q q$ mesons $\pi, \sigma, \rho, A_1$ and gluons that at $T_{zb}$, the quark-antiquark scattering length goes through $\infty$ at which conformal invariance is restored, thereby transforming the matter into a near perfect fluid behaving hydrodynamically, as found at RHIC. We name this new state of matter as "sticky molasses". We show that the binding of these states is accomplished by the combination of (i) the color Coulomb interaction, (ii) the relativistic effects, and (iii) the interaction induced by the instanton-anti-instanton molecules. The spin-spin forces turned out to be small. While near $T_{zb}$ all mesons are large-size nonrelativistic objects bound by Coulomb attraction, near $T_c$ they get much more tightly bound, with many-body collective interactions becoming important and making the $\sigma$ and $\pi$ masses approach zero (in the chiral limit). The wave function at the origin grows strongly with binding, and the near-local four-Fermi interactions induced by the instanton molecules play an increasingly more important role as the temperature moves downward toward $T_c$.
    03/2004;
  • Source
    Hyun-Chul Kim, Chang-Hwan Lee, Hee-Jung Lee
    [show abstract] [hide abstract]
    ABSTRACT: We investigate medium modifications of the pentaquark $\Theta^+$ in dense medium, taking into account different parities of the exotic $\Theta^+$ baryon. We find that the chemical potential of the $\Theta^+$ is shifted in a density-dependent way to one-loop order. We also investigated the effect of the scaled nucleon mass in dense medium on the $\Theta^+$ propagator. The results turn out to depend sensitively on the scaled nucleon mass and on the parity of the $\Theta^+$.
    03/2004;
  • 01/2004;
  • Source
    Gerald E. Brown, Chang-Hwan Lee
    [show abstract] [hide abstract]
    ABSTRACT: Earlier works, which we review, have shown that if the Fe core in a presupernova star is to be sufficiently massive to collapse into a black hole, earlier in the evolution of the star the He core must be covered (clothed) by a hydrogen envelope during He core burning and removed only following this, in, e.g. common envelope evolution. This is classified as Case C mass transfer. These previous arguments were based chiefly on stellar evolution, especially depending on the way in which 12C burned. In this work we argue for Case C mass transfer on the basis of binary evolution. The giant progenitor of the black hole will have a large radius 1000 Rsun at the end of its supergiant stage. Its lifetime at that point will be short, about 1000 yrs, so it will not expand much further. Thus, the initial giant radius for Case C mass transfer will be constrained to a narrow band about 1000 Rsun. This has the consequence that the final separation a_f following common envelope evolution will depend nearly linearly on the mass of the companion m_d which becomes the donor after the He core of the giant has collapsed into the black hole. The separation at which this collapse takes place is essentially a_f, because of the rapid evolution of the giant. (In at least two binaries the black hole donor separation has been substantially increased because of mass loss in the black hole formation. These can be reconstructed from the amount of mass deposited on the donor in this mass loss.) We show that the reconstructed preexplosion separations of the black hole binaries fit well the linear relationship. Comment: 20 pages, 5 figures, accepted for the publication in New Astronomy
    New Astronomy 11/2003; · 1.85 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: As the chirally restored phase ends with T coming down to Tc, a phase resembling a mixed phase is realized, during which the hadrons (which are massless at Tc in the chiral limit) get their masses back out of their kinetic energy. The gluon condensation energy is fed into the system to keep the temperature (nearly) constant. Lattice results for the gluon condensation are matched by a Nambu–Jona–Lasinio calculation. The latter shows that below Tc the chiral symmetry is barely broken, so that with an ∼6% drop in the scalar coupling G it is restored at Tc. Nearly half of the glue, which we call epoxy, is not melted at Tc.
    Physics Reports. 08/2003;
  • Source
    Chang-Hwan Lee, Gerald E. Brown
    [show abstract] [hide abstract]
    ABSTRACT: We show that a common evolutionary history can produce the black hole binaries in the Galaxy in which the black holes have masses of ~ 5 - 10Msolar. In the black hole binaries with low-mass, <~ 2.5Msolar ZAMS (zero age main sequence) companions, the latter remain in main sequence during the active stage of soft X-ray transients (SXT's), most of them being of K or M classification. In two intermediate cases, IL Lupi and Nova Scorpii with ZAMS ~ 2.5Msolar companions the orbits are greatly widened because of large mass loss in the explosion forming the black hole, and whereas these companions are in late main sequence evolution, they are close to evolving. Binaries with companion ZAMS masses >~ 3Msolar are initially ``silent'' until the companion begins evolving across the Herzsprung gap. We provide evidence that the narrower, shorter period binaries, with companions now in main sequence, are fossil remnants of gamma ray bursters (GRB's). We also show that the GRB is generally accompanied by a hypernova explosion (a very energetic supernova explosion). We further show that the binaries with evolved companions are good models for some of the ultraluminous X-ray sources (ULX's) recently seen by Chandra in other galaxies. The great regularity in our evolutionary history, especially the fact that most of the companions of ZAMS mass <~ 2.5Msolar remain in main sequences as K or M stars can be explained by the mass loss in common envelope evolution to be Case C; i.e. to occur only after core He burning has finished. Since our argument for Case C mass transfer is not generally understood in the community, we add an appendix, showing that with certain assumptions which we outline we can reproduce the regularities in the evolution of black hole binaries by Case C mass transfer.
    International Journal of Modern Physics A 01/2003; 18:527-576. · 1.13 Impact Factor
  • Chang-Hwan Lee, Heon-Young Chang
    03/2002; -1.
  • Source
    Heon-Young Chang, Chang-Hwan Lee, Insu Yi
    [show abstract] [hide abstract]
    ABSTRACT: We investigate consequences of a continuously energy-injecting central engine of gamma-ray burst (GRB) afterglow emission, assuming that a highly magnetized pulsar is left beaming in the core of a GRB progenitor. Beaming and continuous energy-injection are natural consequences of the pulsar origin of GRB afterglows. Whereas previous studies have considered continuous energy-injection from a new-born pulsar to interpret the deviation of afterglow light curves of GRBs from those with the simple power law behavior, a beaming effect, which is one of the most important aspects of pulsar emissions, is ignored in earlier investigations. We explicitly include the beaming effect and consider a change of the beaming with time due to a dynamical evolution of a new-born pulsar. We show that the magnitude of the afterglow from this fireball indeed first decreases with time, subsequently rises, and declines again. One of the most peculiar optical afterglows light curve of GRB 970508 can be accounted for by continuous energy injection with beaming due to a highly magnetized new-born pulsar. We discuss implications on such observational evidence for a pulsar. Comment: 4 pages, 1 table, submitted to Astronomy and Astrophysics (Letters)
    Astronomy and Astrophysics 10/2001; · 5.08 Impact Factor
  • Source
    Chang-Hwan Lee, G. E. Brown, R. A. M. J. Wijers
    [show abstract] [hide abstract]
    ABSTRACT: We investigate the soft X-ray transients with black hole primaries which may have been the sources of gamma-ray bursts and hypernovae earlier in their evolution. We find that the black-hole mass increases with the orbital period of the binary, both for systems with main-sequence donors and for those with evolved donors. This correlation can be understood in terms of angular-momentum support in the helium star progenitor of the black hole, if the systems with shorter periods had more rapidly rotating primaries prior to their explosion: centrifugal support will then prevent more of its mass from collapsing into the black hole. This trend of more rapidly rotating stars in closer binaries is very generally seen, and in the present case can be understood in terms of spin-up during spiral in and subsequent tidal coupling. We investigate the relation quantitatively and obtain reasonable agreement with the observed mass-period correlation. A natural consequence of this observation is that black holes formed in soft X-ray transients acquire significant Kerr parameters. This makes them good sources of power for gamma-ray bursts and hypernovae, via the Blandford-Znajek mechanism, and thus supports our model for the origin of gamma-ray bursts in soft X-ray transients. Comment: 33 pages, 12 figures,substantial changes
    The Astrophysical Journal 09/2001; · 6.73 Impact Factor
  • 01/2001;

Publication Stats

236 Citations
30 Downloads
178.43 Total Impact Points

Institutions

  • 2003–2011
    • Pusan National University
      • Department of Physics
      Tsau-liang-hai, Busan, South Korea
  • 2008
    • SUNY Ulster
      Kingston, New York, United States
  • 2007
    • Cornell University
      Ithaca, New York, United States
  • 2006
    • State University of New York
      New York City, New York, United States
  • 1994–2003
    • Seoul National University
      • Center for Theoretical Physics
      Sŏul, Seoul, South Korea
  • 1996
    • University of Washington Seattle
      • Institute for Nuclear Theory
      Seattle, Washington, United States