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Search Results: 1 - 10 of 138876 matches for " K. Kanaya "
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Deconfining Chiral Transition in QCD on the Lattice
K. Kanaya
Physics , 1995, DOI: 10.1143/PTPS.120.25
Abstract: The deconfining chiral transition in finite-temperature QCD is studied on the lattice using Wilson quarks. After discussing the nature of chiral limit with Wilson quarks, we first study the case of two degenerate quarks $N_F=2$, and find that the transition is smooth in the chiral limit on both $N_t=4$ and 6 lattices. For $N_F=3$, on the other hand, clear two state signals are observed for $m_q \simm{<} 140$ MeV on $\nt=4$ lattices. For a more realistic case of $N_F=2+1$, i.e.\ two degenerate u and d-quarks and a heavier s-quark, we study the cases $m_s \simeq 150$ and 400 MeV with $m_u = m_d \simeq 0$: In contrast to a previous result with staggered quarks, clear two state signals are observed for both cases, suggesting a first order QCD phase transition in the real world.
An Introduction to Finite Temperature Quantum Chromodynamics on the Lattice
K. Kanaya
Physics , 1998, DOI: 10.1143/PTPS.131.73
Abstract: In these lectures, we introduce finite temperature QCD on the lattice to non-experts of the subject. We first formulate lattice QCD both at zero and finite temperatures. Then a section is devoted to the topic of improved lattice actions which are becoming an essential ingredient of precision studies of QCD on the lattice. We then discuss about finite temperature SU(3) gauge theory, i.e. QCD without dynamical quarks (quenched QCD). Finally, we report recent status of studies in full QCD taking into account the effects of dynamical quarks.
FINITE TEMPERATURE PHASE TRANSITION IN QCD WITH STRANGE QUARK: STUDY WITH WILSON FERMIONS ON THE LATTICE
K. Kanaya
Physics , 1995,
Abstract: The effect of the strange quark in the finite temperature phase transition of QCD is studied on the lattice. Using the one-plaquette gauge action and the Wilson quark action, the transition in the chiral limit is shown to be continuous for the case of degenerate two flavors, $N_F=2$, while it is of first order for $N_F \geq 3$. For a more realistic case of massless up and down quarks and a light strange quark, $N_F=2+1$, clear two state signals are observed both for $m_s \simeq 150$ and 400 MeV. In contrast to a previous result with staggered quarks, this suggests a first order transition in the real world. In order to see the implication of these results to the continuum limit, we started to study these issues using improved actions. First results using a RG improved gauge action combined with the standard Wilson quark is presented for the case of $N_F=2$: With this action the finite temperature transition is shown to be continuous in the chiral limit confirming the result of the standard action. Furthermore, not like the case of the standard action where lattice artifacts make the transition once very strong at intermediate values of the hopping parameter $K$ on $N_t=4$ and 6 lattices, a smooth crossover is found for the improved action when we increase $1/K-1/K_c$, in accord with a naive expectation about the fate of second order chiral transition at finite $m_q$.
QCD phase transition with two flavors of Wilson quarks using a RG improved action
K. Kanaya
Physics , 1995, DOI: 10.1143/PTPS.122.115
Abstract: The finite temperature QCD phase transition is studied on the lattice with degenerate two flavors of Wilson quarks. Motivated by reported strange behaviors with the standard action on lattices with the temporal extention $N_t=4$ and 6, a renormalization group improved gauge action is applied. On an $N_t=4$ lattice, the strange behaviors observed with the standard action are removed with our improved action. The finite temperature transition is continuous in the chiral limit and it becomes quite smooth in all observables we studied when we increase the quark mass by increasing $\beta$ along the crossover line.
Hadronic Properties from Lattice QCD with Dynamical Quarks
K. Kanaya
Physics , 2000, DOI: 10.1016/S0375-9474(00)00415-2
Abstract: The lattice regularization of QCD provides us with the most systematic way of computing non-perturbative properties of hadrons directly from the first principles of QCD. The recent rapid development of parallel computers has enabled us to start realistic and systematic simulations with dynamical quarks. In this paper, I report on the first results from recent systematic studies on the lattice with dynamical quarks.
Critical exponents of a three dimensional O(4) spin model
K. Kanaya,S. Kaya
Physics , 1994, DOI: 10.1103/PhysRevD.51.2404
Abstract: By Monte Carlo simulation we study the critical exponents governing the transition of the three-dimensional classical O(4) Heisenberg model, which is considered to be in the same universality class as the finite-temperature QCD with massless two flavors. We use the single cluster algorithm and the histogram reweighting technique to obtain observables at the critical temperature. After estimating an accurate value of the inverse critical temperature $\Kc=0.9360(1)$, we make non-perturbative estimates for various critical exponents by finite-size scaling analysis. They are in excellent agreement with those obtained with the $4-\epsilon$ expansion method with errors reduced to about halves of them.
Non-perturbative determination of anisotropy coefficients and pressure gap at the deconfining transition of QCD
S. Ejiri,Y. Iwasaki,K. Kanaya
Physics , 1998, DOI: 10.1016/S0920-5632(99)85089-0
Abstract: We propose a new non-perturbative method to compute derivatives of gauge coupling constants with respect to anisotropic lattice spacings (anisotropy coefficients). Our method is based on a precise measurement of the finite temperature deconfining transition curve in the lattice coupling parameter space extended to anisotropic lattices by applying the spectral density method. We determine the anisotropy coefficients for the cases of SU(2) and SU(3) gauge theories. A longstanding problem, when one uses the perturbative anisotropy coefficients, is a non-vanishing pressure gap at the deconfining transition point in the SU(3) gauge theory. Using our non-perturbative anisotropy coefficients, we find that this problem is completely resolved.
Non-perturbative determination of anisotropy coefficients in lattice gauge theories
S. Ejiri,Y. Iwasaki,K. Kanaya
Physics , 1998, DOI: 10.1103/PhysRevD.58.094505
Abstract: We propose a new non-perturbative method to compute derivatives of gauge coupling constants with respect to anisotropic lattice spacings (anisotropy coefficients), which are required in an evaluation of thermodynamic quantities from numerical simulations on the lattice. Our method is based on a precise measurement of the finite temperature deconfining transition curve in the lattice coupling parameter space extended to anisotropic lattices by applying the spectral density method. We test the method for the cases of SU(2) and SU(3) gauge theories at the deconfining transition point on lattices with the lattice size in the time direction $N_t=4$ -- 6. In both cases, there is a clear discrepancy between our results and perturbative values. A longstanding problem, when one uses the perturbative anisotropy coefficients, is a non-vanishing pressure gap at the deconfining transition point in the SU(3) gauge theory. Using our non-perturbative anisotropy coefficients, we find that this problem is completely resolved: we obtain $\Delta p/T^4 = 0.001(15)$ and $-0.003(17)$ on $N_t=4$ and 6 lattices, respectively.
Global carbon monoxide as retrieved from SCIAMACHY by WFM-DOAS
K. Toyota, Y. Kanaya, M. Takahashi,H. Akimoto
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2004,
Abstract: A new chemical scheme is developed for the multiphase photochemical box model SEAMAC (size-SEgregated Aerosol model for Marine Air Chemistry) to investigate photochemical interactions between volatile organic compounds (VOCs) and reactive halogen species in the marine boundary layer (MBL). Based primarily on critically evaluated kinetic and photochemical rate parameters as well as a protocol for chemical mechanism development, the new scheme has achieved a near-explicit description of oxidative degradation of up to C3-hydrocarbons (CH4, C2H6, C3H8, C2H4, C3H6, and C2H2) initiated by reactions with OH radicals, Cl- and Br-atoms, and O3. Rate constants and product yields for reactions involving halogen species are taken from the literature where available, but the majority of them need to be estimated. In particular, addition reactions of halogen atoms with alkenes will result in forming halogenated organic intermediates, whose photochemical loss rates are carefully evaluated in the present work. Model calculations with the new chemical scheme reveal that the oceanic emissions of acetaldehyde (CH3CHO) and alkenes (especially C3H6) are important factors for regulating reactive halogen chemistry in the MBL by promoting the conversion of Br atoms into HBr or more stable brominated intermediates in the organic form. The latter include brominated hydroperoxides, bromoacetaldehyde, and bromoacetone, which sequester bromine from a reactive inorganic pool. The total mixing ratio of brominated organic species thus produced is likely to reach 10-20% or more of that of inorganic gaseous bromine species over wide regions over the ocean. The reaction between Br atoms and C2H2 is shown to be unimportant for determining the degree of bromine activation in the remote MBL. These results imply that reactive halogen chemistry can mediate a link between the oceanic emissions of VOCs and the behaviors of compounds that are sensitive to halogen chemistry such as dimethyl sulfide, NOx, and O3 in the MBL.
A 5.9 GHz Low Power and Wide Tuning Range CMOS Current-controlled Ring Oscillator
Prapto Nugroho,Ramesh K. Pokharel,Haruichi Kanaya,Keiji Yoshida
International Journal of Electrical and Computer Engineering , 2012, DOI: 10.11591/ijece.v2i3.229
Abstract: Designing low power, low noise, wide tuning range and small size circuit in one single chip is very challenging. This paper describe a low power, wide tuning range three-stage current-controlled ring oscillator (CCO) designed on 0.18um CMOS technology. The CCO circuit has tuning range from 251 MHz to 5.5 GHz or 183% wide. It consumes only 144 uA to 9.76mA by using 1.8V power supply. Phase noise is -104 dBc /Hz at 5.5 GHz and 4 Mhz offset frequency. Calculated FoM is -154.4 dBc /Hz which is the best among published counterpart papers. The size of the core oscillator circuits without bonding pads is only 0.0003 mm2.
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