Showing papers in "Progress of Theoretical Physics Supplement in 2004"
TL;DR: The recent progress in understanding the QCD phase diagram and the physics of the critical point is reviewed in this paper, where the authors present a review of the recent progress on understanding the phase diagram.
Abstract: The recent progress in understanding the QCD phase diagram and the physics of the QCD critical point is reviewed.
375 citations
TL;DR: In this article, the authors review radiative processes responsible for X-ray emission in hard (low) and soft (high) spectral states of black-hole binaries and find that the main process in the hard state appears to be scattering of blackbody photons from a cold disk by thermal electrons in a hot inner flow, and any contribution from nonthermal synchrotron emission is at most small.
Abstract: We review radiative processes responsible for X-ray emission in hard (low) and soft (high) spectral states of black-hole binaries. The main process in the hard state appears to be scattering of blackbody photons from a cold disk by thermal electrons in a hot inner flow, and any contribution from nonthermal synchrotron emission is at most small. In the soft states, blackbody disk emission dominates energetically, and its high-energy tail is due to scattering by hybrid, thermal/nonthermal electrons, probably in active regions above the disk surface. State transitions appear to correspond to a variable inner radius of the cold disk driven by changes of the accretion rate. The existence of two accretion solutions, hot and cold, in a range of the accretion rate leads to hysteresis in low-mass X-ray binaries.
279 citations
TL;DR: The electron screening effect in the d(d,p)t reaction has been studied for deuterated metals, insulators, and semiconductors, i.e. 58 samples in total.
Abstract: The electron screening effect in the d(d,p)t reaction has been studied for deuterated metals, insulators, and semiconductors, i.e. 58 samples in total. As compared to measurements performed with a gaseous D 2 target, a large effect has been observed in most metals, while a small (gaseous) effect is found e.g. for the insulators, semiconductors and lanthanides. The periodic table provides the ordering of the observed small and large effects in the samples. An explanation of the large effects in metals is possibly provided by the classical plasma screening of Debye applied to the quasi-free metallic electrons. The data also provide information on the solubility of hydrogen in the samples.
103 citations
TL;DR: In this article, it was shown that the observable Kerr disk spectra becomes significantly harder than Schwarzschild disk spectras only when the disk is highly inclined, and that the emission from the innermost part of the accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen for a face-on disk.
Abstract: Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard optically thick accretion disk in the Schwarzschild metric. On the other hand, the standard accretion disk around the Kerr black hole might explain the observed high disk temperature, as the inner radius of the Kerr disk gets smaller and the disk temperature can be consequently higher. However, we point out that the observable Kerr disk spectra becomes significantly harder than Schwarzschild disk spectra only when the disk is highly inclined. This is because the emission from the innermost part of the accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen for a face-on disk. The Galactic superluminal jet sources are known to be highly inclined systems, thus their energy spectra may be explained with the standard Kerr disk with known black hole masses. For ULXs, on the other hand, the standard Kerr disk model seems implausible, since it is highly unlikely that their accretion disks are preferentially inclined, and, if edge-on Kerr disk model is applied, the black hole mass becomes unreasonably large (greater than or approximately equal to 300 Solar Mass). Instead, the slim disk (advection dominated optically thick disk) model is likely to explain the observed super- Eddington luminosities, hard energy spectra, and spectral variations of ULXs. We suggest that ULXs are accreting black holes with a few tens of solar mass, which is not unexpected from the standard stellar evolution scenario, and their X-ray emission is from the slim disk shining at super-Eddington luminosities.
74 citations
TL;DR: In this paper, the effects of color superconductivity on the mass-radius relationship of compact stars have been discussed, showing that one would have to fix the bag constant by other measurements in order to see the effects.
Abstract: According to quantum chromodynamics (QCD), matter at ultra-high densities will take the form of a color-superconducting quark liquid, in which there is a condensate of Cooper pairs of quarks near the Fermi surface. I present a review of the physics of color superconductivity. I give particular attention to the recently proposed gapless CFL (gCFL) phase, which has unusual properties such as quasiquarks with a near-quadratic dispersion relation, and which may well be the favored phase of quark matter in the density range relevant to compact stars. I also discuss the effects of color superconductivity on the mass-radius relationship of compact stars, showing that one would have to fix the bag constant by other measurements in order to see the effects of color superconductivity. An additional parameter in the quark matter equation of state connected with perturbative corrections allows quark matter to imitate nuclear matter over the relevant density range so that hybrid stars can show a mass-radius relationship very similar to that of nuclear matter, and their masses can reach 1.9 M O ..
72 citations
TL;DR: In this paper, the authors review the X-ray and optical data on the nature of the ULXs in nearby galaxies and find that the radio is usually rather luminous and extended.
Abstract: I briefly review much of the X-ray and optical data on the nature of the ULXs in nearby galaxies. I present new results on radio emission, finding that the radio is usually rather luminous and extended. I review the X-raydata on timing and spectra. There is no direct evidence in the X-ray data for either geometric or relativistic beaming and in 4 objects direct evidence against beaming. I argue that the X-ray timing and spectral properties of these objects, are in general, not good analogs of AGN or galactic black holes and that the ULX may represent a new mode of accretion only rarely seen in other objects.
56 citations
TL;DR: In this article, the phase structure and equation of state for QCD at non-zero temperature and density were discussed, and the phase transition line for 2 and 3-flavor QCD and the critical endpoint in the $(T, \mu_q)$ plane were investigated.
Abstract: We discuss the phase structure and the equation of state for QCD at non-zero temperature and density. Derivatives of $\ln Z$ with respect to quark chemical potential $\mu_q$ up to fourth order are calculated for 2-flavor QCD, enabling estimates of the pressure, quark number density and associated susceptibilities as functions of $\mu_q$ via a Taylor series expansion. Also, the phase transition line for 2 and 3-flavor QCD and the critical endpoint in the $(T, \mu_q)$ plane are investigated in the low density regime.
56 citations
TL;DR: In this paper, the renormalized free energy of a heavy quark anti-quark pair in different color channels in full QCD at finite temperature was studied and the temperature dependence as well as their short distance behavior was analyzed.
Abstract: We study the renormalized free energy of a heavy quark anti-quark pair in the different colour channels in full QCD at finite temperature. Similarities and differences to the quenched case are discussed and the temperature dependence as well as their short distance behavior are analyzed. The asymptotic large distance behavior of the free energy is used to define the non-perturbatively renormalized Polyakov loop which is well behaved in the continuum limit.
39 citations
TL;DR: In this paper, the axial-vector self-energy stemming from the Fock exchange term of the one-gluon exchange interaction has a central role to cause spin polarization.
Abstract: A coexistent phase of spin polarization and color superconductivity in high-density QCD is studied at zero temperature. The axial-vector self-energy stemming from the Fock exchange term of the one-gluon-exchange interaction has a central role to cause spin polarization. As a significant feature, the Fermi surface is deformed by the axial-vector self-energy and then rotation symmetry is spontaneously broken down. The gap function results in being anisotropic in the momentum space in accordance with the deformation. It is found that spin polarization barely conflicts with color superconductivity, and almost coexists with it.
30 citations
TL;DR: In the absence of a potential pocket, fusion does not occur in the commonly used realistic coupled channels code CCFULL where fusion is calculated by applying an incoming wave boundary condition at the position of the minimum of the attractive pocket.
Abstract: Fits to high precision fusion cross-sections even for Z P Z T < 1000 appear to need a value of the diffuseness parameter a of the Woods-Saxon potential of ≃1 fm, which is much larger than the commonly accepted value of ≃ 065 fm However, use of large values of a necessarily makes the potential pocket very shallow for realistic values of the nuclear potential depth For larger values of angular momenta the pocket disappears, and a fusion barrier energy or radius can no longer be defined In the absence of a potential pocket, fusion does not occur in the commonly used realistic coupled channels code CCFULL where fusion is calculated by applying an incoming wave boundary condition at the position of the minimum of the attractive pocket For this reason, realistic coupled channels calculations with large values of a have needed unrealistically deep nuclear potentials Once the potential depth is constrained to reasonable values, the data cannot be explained by simply changing the diffuseness of the nuclear potential This indicates the necessity to go beyond the potential model, and incorporate dynamical effects as the two nuclei move towards fusion, even for light systems with Z P Z T < 1000
28 citations
TL;DR: In this paper, the deuteron induced fusion reactions in metals at very low energies were investigated and it was shown that the low energy nuclear reactions are strongly affected by the metal environments surrounding the nuclei.
Abstract: In order to investigate the interplay between nuclei and their surroundings, we have studied deuteron induced fusion reactions in metals at very low energies. We summarize the results on the following measurements; reaction rates of the D(d,p)T reaction in various metals for bombarding energies between 2.5 and 10 keV and those of the 6 , 7 Li(d,α) 4 , 5 He reactions in Pd and Au for bombarding energies between 30 and 75 keV. These measurements clearly showed that the low energy nuclear reactions are strongly affected by the metal environments surrounding the nuclei.
TL;DR: In this paper, the decoherence effects of the imaginary parts of optical potentials without also losing flux are modeled using semigroup evolution equations, which can be used to predict complete and incomplete fusion of two-body projectiles.
Abstract: Theories of breakup and fusion of two-body projectiles are examined, to see how complete and incomplete fusion may be predicted separately. A proposal is made for an 'optical decoherence model' which uses semigroup evolution equations to describe the decoherence effects of the imaginary parts of optical potentials without also losing flux.
TL;DR: In this paper, the Ornstein-Uhlenbeck process was used to explain the distribution of RHIC energy at RHIC energies, assuming the existence of a third source in addition to two sources at the beam and target rapidities.
Abstract: To explain η-distributions at RHIC energies we consider the Ornstein-Uhlenbeck process. To account for hadrons produced in the central region, we assume existence of third source located there (y 0) in addition to two sources located at the beam and target rapidities (′y m a x = ′ In [√s N N /m N ]). This results in better Χ 2 /n.d.f. than those for only two sources when analysing data.
TL;DR: In this article, performance simulations of sub-mm VLBI arrays for imaging SgrA* were presented, and the authors showed that even with a small array, they can estimate the shadow size and then the mass of black hole from visibility analysis.
Abstract: Imaging the vicinity of black hole is one of the ultimate goals of VLBI astronomy. The closest massive black hole, SgrA*, located at Galactic center is the leading candidate for such observations. Combined with recent VLBI recording technique and sub-mm radio engineering, we now have the sufficient sensitivity for the observations. We here show performance simulations of sub-mm VLBI arrays for imaging SgrA*. An excellent image is obtained from a sub-mm. VLBI array in southern hemisphere like the configuration of VLBA. We also note that even with a small array, we. can estimate the shadow size and then the mass of black hole from visibility analysis. Now, if only constructing a, sub-mm VLBI array in southern hemisphere, we can unveil the black hole environments of SgrA*.
TL;DR: In this paper, the scalar polarizability of a nucleon is estimated from lattice QCD at relatively large "light quark" masses to the physical world to estimate the nucleon's saturation mechanism.
Abstract: As we search for an ever deeper understanding of the structure of hadronic matter one of the most fundamental questions is whether or not one can make a connection to the underlying theory of the strong interaction, QCD. We build on recent advances in the chiral extrapolation problem linking lattice QCD at relatively large "light quark" masses to the physical world to estimate the scalar polarizability of the nucleon. The latter plays a key role in modern relativistic mean-field descriptions of nuclei and nuclear matter (such as QMC) and, in particular, leads to a very natural saturation mechanism. We demonstrate that the value of the scalar polarizability extracted from the lattice data is consistent with that needed for a successful description of nuclei within the framework of QMC. In a very real sense this is the first hint of a direct connection between QCD and the properties of finite nuclei.
Journal Article•
TL;DR: In this paper, the Ornstein-Uhlenbeck process was used to explain the distribution of RHIC energy at RHIC energies, assuming the existence of a third source in addition to two sources at the beam and target rapidities.
Abstract: To explain η-distributions at RHIC energies we consider the Ornstein-Uhlenbeck process. To account for hadrons produced in the central region, we assume existence of third source located there (y 0) in addition to two sources located at the beam and target rapidities (′y m a x = ′ In [√s N N /m N ]). This results in better Χ 2 /n.d.f. than those for only two sources when analysing data.
TL;DR: In this article, the authors reviewed the approximations that are commonly made in coupled-channels calculations of heavy-ion fusion reactions in order to show where uncertainties exist and improvements can be made.
Abstract: The approximations that are commonly made in coupled-channels calculations of heavy-ion fusion reactions are reviewed in order to show where uncertainties exist and improvements can be made. In particular, the failure in modeling the fusion at extreme subbarrier energies is discussed.
TL;DR: In this paper, the role of resonances for the occurrence of the transition to the quark-gluon plasma in hot and dense matter was discussed and properties of a hadronic resonance gas were compared to lattice results on the equation of state at zero as well as non-zero baryon chemical potential.
Abstract: We present results from lattice calculations on the thermodynamics of QCD at nonzero temperature and baryon chemical potential and discuss the role of resonances for the occurrence of the transition to the quark-gluon plasma in hot and dense matter. Properties of a hadronic resonance gas are compared to lattice results on the equation of state at zero as well as non-zero baryon chemical potential. Furthermore, it is shown that the quark mass dependence of the transition temperature can be understood in terms of lines of constant energy density in a resonance gas.
TL;DR: A review of strong coupling approaches to grasp the nature of the phase transition in finite temperature and density QCD can be found in this article, where the effective action derived in the strong coupling limit gives qualitatively plausible behavior for the deconfinement transition at finite temperature.
Abstract: This is a review of strong coupling approaches to grasp the nature of the phase transition in finite temperature and density QCD. We commence with classics of the center symmetry and the Polyakov loop in pure gauge theories. The effective action derived in the strong coupling limit gives qualitatively plausible behavior for the deconfinement transition at finite temperature. We can apply the strong coupling analysis to describe the chiral phase transition with the help of large dimensional expansion. In order to make this article as self-contained as possible, we elucidate the computational procedure and its physical meaning in detail. Also the relation between the Polyakov loop behavior and the chiral dynamics, the phase structure of two-color QCD, and future possibilities to be pursued in the strong coupling analysis are discussed.
TL;DR: In this article, it was shown that the intermediate transfer channels with positive Q-values really enhance the fusion cross section at sub-barrier energies, especially for fusion of weakly bound nuclei.
Abstract: From the analysis of appropriate experimental data within a simple theoretical model it is shown that the intermediate neutron transfer channels with positive Q-values really enhance the fusion cross section at sub-barrier energies The effect of sequential fusion was found to be very large especially for fusion of weakly bound nuclei New experiments are proposed, which may shed additional light on the effect of neutron transfer in fusion processes
TL;DR: In this paper, the influence of an external magnetic field on chiral symmetry breaking in the Nambu-Jona-Lasinio (NJL) model at finite temperature and chemical potential was investigated.
Abstract: We investigate the influence of an external magnetic field on chiral symmetry breaking in the Nambu-Jona-Lasinio (NJL) model at finite temperature and chemical potential. According to the Fock-Schwinger proper-time method, we calculate the effective potential in the leading order of the 1/N c expansion. The phase boundary dividing the symmetric phase and the broken phase is illustrated numerically. A complex behavior of the phase boundary is found for large chemical potential.
TL;DR: In this paper, the authors show that the complete fusion process is hindered with respect to realistic theoretical predictions (CCFUSS) for the systems 9 Be+ 2 0 8 Pb, 2 0 9 Bi and 6 Li+ 2 1/8 Pb.
Abstract: From recent experimental data for the systems 9 Be+ 2 0 8 Pb, 2 0 9 Bi and 6 Li+ 2 0 8 Pb it results that the complete fusion process is hindered with respect to realistic theoretical predictions (CCFUSS). However the 9 Be+ 2 0 8 Pb, 2 0 9 Bi complete fusion cross sections are different from each other contrary to expectations. The 6 Li data show breakup of the projectile into two outgoing fragments, well reproduced by CDCC approach, as well as α or deuteron capture from the target; this is relevant for the theories on the reaction dynamics around the Coulomb barrier.
TL;DR: In this paper, hyperon mixing in neutron star matter is investigated by the G-matrix-based effective interaction approach under the attention to use the YN and the YY potentials compatible with hypernuclear data and is shown to occur atdensities relevant to neutron star cores, together with discussions to clarify the mechanism of hyperon contamination.
Abstract: Hyperon mixing in neutron star matter is investigated by the G-matrix-based effective interaction approach under the attention to use the YN and the YY potentials compatible with hypernuclear data and is shown to occur atdensities relevant to neutron star cores, together with discussions to clarify the mechanism of hyperon contamination. It is remarked that developed Y-mixed phase causes a dramatic softening of the neutron star equation of state and leads to the serious problem that the resulting maximum mass M m a x for neutron star model contradicts the observed neutron star mass (M m a x M o b s ) the threshold densities for A and Σ - are pushed to higher density side, from ∼ 2ρ 0 to ∼ 4ρ 0 (ρ 0 being the nuclear density). On the basis of a realistic Y-mixed neutron star model, occurrence of Y-superfluidity essential for "hyperon cooling" scenario is studied and both of A- and Σ - -superfluids are shown to be realized with their critical temperatures 10 8 - 9 K, meaning that the "hyperon cooling" is a promising candidate for a fast non-standard cooling demanded for some neutron stars with low surface temperature. A comment is given as to the consequence of less attractive ΛΛ interaction suggested by the "NAGARA event" 6 Λ Λ He.
TL;DR: In this article, the X-ray and optical variability properties of radio-quiet AGN and the relation between the two bands are discussed. But the relationship between optical and x-ray variability is complex, with some AGN showing strong X-rays/optical correlations while others show no obvious correlation.
Abstract: Long-time-scale X-ray and optical variability is a key characteristic of AGN. Here, we summarise our current understanding of the X-ray and optical continuum variability of radioquiet AGN and the relation between the two bands. We demonstrate the strong connection between the X-ray variability properties of AGN and the variability of stellar-mass black hole candidates on much shorter time-scales, and discuss the implications of this result for the origins of the variability. The relationship between optical and X-ray variability is complex, with some AGN showing strong X-ray/optical correlations while others show no obvious correlation. We suggest a possible explanation for this variety of behaviour.
Journal Article•
TL;DR: A brief overview of strangeness nuclear physics is given in this article, focussing on the recent determination of spin-dependent effects in A hypernuclei, on the recently established repulsive nature of the Σ nuclear potential and particularly on new developments in doublestrangeness physics.
Abstract: On this occasion of marking 50 years to the inception of hypernuclear physics, a brief overview of strangeness nuclear physics is given, focussing on the recent determination of spin-dependent effects in A hypernuclei, onthe recently established repulsive nature of the Σ nuclear potential and particularly on new developments in double-strangeness physics. Special emphasis is placed on the extrapolation to strange hadronic matter.
TL;DR: In this article, the authors discuss the properties of the friction form factor as function of the deformation and possibly of the temperature which are necessary to reproduce data concerning fission of hot nuclei and its accompanying light particle and γ-ray emission.
Abstract: Recent progress in the theory of fission of hot nuclei is reported. We discuss in particular the properties of the friction form factor as function of the deformation (and possibly of the temperature) which are necessary to reproduce data concerning fission of hot nuclei and its accompanying light particle and γ-ray emission. Recent theoretical work gives support to a phenomenological friction form factor (proposed some time ago [P. Frobrich, I. I. Gontchar and N. D. Mavlitov, Nucl. Phys. A 556 (1993), 281]), which is weak for compact shapes and increases on the way to scission.
TL;DR: In this article, Taylor series expansions of lattice results are used to extract properties of QCD at finite chemical potential (µ) using Taylor series expansion and the result of expanding the free energy density to 6th order in the expansion is shown.
Abstract: Properties of QCD at finite chemical potential (µ) are extracted using Taylor series expansions. The continuum limits of lattice results are presented. The result of expanding the free energy density, i.e., the pressure, to 6th order in the expansion is shown. The Taylor coefficients of the chiral condensate are also shown. Relations between various Taylor coefficients are demonstrated. All this information is utilised to remove various lattice artifacts from the determination of the Wroblewski parameter in strangeness production.
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Journal Article•
TL;DR: In this article, weak interaction rates involving Goldstone bosons in the neutral kaon condensed phase of color-locked quark matter were studied and the dominant processes that contribute to the neutrino mean free path and neutrinos production were identified.
Abstract: We study weak interaction rates involving Goldstone bosons in the neutral kaon condensed phase of color flavor locked quark matter. We identify the dominant processes that contribute to the neutrino mean free path and to neutrino production. We find unique characteristics of weak interaction rates in this novel phase and discuss how they might influence neutrino emission in a core collapse supernova.