著者

Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.64, no.3, pp.034505, 2001-07

被引用文献数

30 98

---

We present a calculation of the B and D meson decay constants in lattice QCD with two (Nf=2) flavors of light dynamical quarks, using an O(a)-improved Wilson action for both light and heavy quarks and a renormalization-group improved gauge action. Simulations are made at three values of lattice spacing a=0.22,0.16,0.11 fm and four values of sea quark mass in the range mPS/mV≈0.8-0.6. Our provisional estimate for the continuum values of the decay constants are fBd=208(10)(29) MeV, fBs=250(10)(35)(-0+8) MeV, fDd=225(14)(40) MeV, fDs=267(13)(48)(-0+10) MeV for Nf=2 where the statistical and systematic errors are separately listed, and the third error for fBs and fDs shows the uncertainty of the determination of the strange quark mass. We also carry out a set of quenched simulations using the same action to make a direct examination of sea quark effects. Taking the ratio of results for Nf=2 and Nf=0, we obtain fBdNf=2/fBdNf=0=1.11(6),fBsNf=2/fBsNf=0=1.14(5),fDdNf=2/fDdNf=0=1.03(6),fDsNf=2/fDsNf=0=1.07(5). They show a 10–15 % increase in the Nf=2 results over those of Nf=0 for the B meson decay constants, while evidence for such a trend is statistically less clear for the D meson decay constants.

著者

Khan A. Ali Aoki S. Aoki Y. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Izubuchi T. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. I. Noaki J. Okawa M. Shanahan H. P. Taniguchi Y. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.63, no.11, pp.114504, 2001-05

被引用文献数

47 61

---

We investigate the chiral properties of quenched domain-wall QCD (DWQCD) at the lattice spacings a-1≃1 and 2 GeV for both plaquette and renormalization-group (RG) improved gauge actions. In the case of the plaquette action we find that the quark mass defined through the axial Ward-Takahashi identity remains non-vanishing in the DWQCD chiral limit that the bare quark mass mf→0 and the length of the fifth dimension Ns→∞, indicating that chiral symmetry is not realized with quenched DWQCD up to a-1≃2 GeV. The behavior is much improved for the RG-improved gauge action: while a nonvanishing quark mass remains in the chiral limit at a-1≃1 GeV, the result at a-1≃2 GeV is consistent with an exponentially vanishing quark mass in the DWQCD chiral limit, indicating the realization of exact chiral symmetry. An interpretation and implications are briefly discussed.

著者

Nomura S. Yamaguchi M. Akazaki T. Tamura H. Maruyama T. Miyashita S. Hirayama Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.76, no.20, pp.201306, 2007-11

被引用文献数

8 7

---

Both the electron and the optically created hole effective masses are found to be density dependent in a two-dimensional electron system of a GaAs/Al0.33Ga0.67As back-gated quantum well by magnetophotoluminescence spectroscopy. We show that the density-dependent electron effective mass increases with a decrease in the electron density (ns) to ns<1×1011 cm−2. It is found that the electron effective masses determined from the lowest and the second Landau levels are larger than those from the higher Landau levels. The hole effective mass is found to increase with a decrease in ns and the hole is found to localize at ns<3×1010 cm−2. We observe an upward convex curve of the photoluminescence peak energy at 2<ν<3 depending on the electron-hole distance divided by the magnetic length. These results clearly show the important roles of both electron-electron and electron-hole interactions in the recombination of a valence hole with a high-quality two-dimensional electron system.

著者

Manke T. Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.62, no.11, pp.114508, 2000-11

被引用文献数

32

---

We study the effects of two dynamical sea quarks on the spectrum of heavy quarkonia. Within the non-relativistic approach to lattice QCD we find sizable changes to the hyperfine splitting, but we do not observe any changes for the fine structure. We also investigate the scaling behavior of our results for several different lattice spacings.

著者

Ishikawa K-I. Yamada N. Aoki S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneda T. Kaya S. Kuramashi Y. Matsufuru H. Okawa M. Onogi T. Tominaga S. Tsutsui N. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.61, no.7, pp.074501, 2000-02

被引用文献数

27 72

---

We present a lattice NRQCD study of the B meson decay constant in the quenched approximation with emphasis given to the scaling behavior. The NRQCD action and the heavy-light axial vector current we use include all terms of order 1/M and the perturbative O(αsa) and O(αs/M) corrections. Using simulations at three values of couplings β=5.7, 5.9, and 6.1 on lattices of sizes 123×32, 163×48, and 243×64, we find a significant a dependence disappears in fB if the O(αsa) correction is included in the axial vector current. We observe that β=5.9-6.1 is the window where systematic errors are expected to be minimum within one-loop improved theory. Our final results are fB=170(5)(15) MeV, fBs=191(4)(17)(-0+4) MeV, and fBs/fB=1.12(2)(1)(-0+3), where the first error is statistical, the second is systematic, and the third is due to the uncertainty of the strange quark mass, while quenching errors are not included.

著者

Aoki S. Boyd G. Burkhalter R. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Okawa M. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.60, no.11, pp.114508, 1999-11

被引用文献数

52 138

---

We investigate the effects of action improvement on the light hadron spectrum and the static quark potential in two-flavor QCD for a-1≈1 GeV and mPS/mV=0.7–0.9. We compare a renormalization group improved action with the plaquette action for gluons and the SW-clover action with the Wilson action for quarks. We find a significant improvement in the hadron spectrum by improving the quark action, while the gluon improvement is crucial for a rotationally invariant static potential. We also explore the region of light quark masses corresponding to mPS/mV>~0.4 on a 2.7 fm lattice using the improved gauge and quark action. A flattening of the potential is not observed up to 2 fm.

著者

Okamoto M. Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. Okawa M. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.60, no.9, pp.094510, 1999-10

被引用文献数

104 166

---

A lattice study of the equation of state for pure SU(3) gauge theory using a renormalization-group (RG) improved action is presented. The energy density and pressure are calculated on a 163×4 and a 323×8 lattice employing the integral method. Extrapolating the results to the continuum limit, we find the energy density and pressure to be in good agreement with those obtained with the standard plaquette action within the error of 3–4 %.

著者

Aoki Y. Csikor F. Fodor Z. Ukawa A.

出版者

American Physical Society

雑誌

Physical review D (ISSN:15507998)

巻号頁・発行日

vol.60, no.1, pp.013001, 1999-07

被引用文献数

81

---

We study the first-order finite-temperature electroweak phase transition of the SU~2! gauge-Higgs modeldefined on a four-dimensional isotropic lattice with the temporal extension Nt52. A finite-size scaling study ofLee-Yang zeros yields the value of the Higgs self-coupling of the end point at lc50.00116(16). An independentanalysis of the Binder cumulant gives a consistent value for the end point. Combined with our zerotemperaturemeasurement of Higgs and W boson masses, this leads to MH,c573.366.4 GeV for the criticalHiggs boson mass beyond which the electroweak transition turns into a crossover.

著者

Aoki S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kuramashi Y. Okawa M. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.60, no.3, pp.034511, 1999-07

被引用文献数

24 47

---

A lattice QCD calculation of the kaon B parameter BK is carried out with the Wilson quark action in the quenched approximation at β=6/g2=5.9–6.5. The mixing problem of the Δs=2 four-quark operators is solved nonperturbatively with full use of chiral Ward identities employing four external quarks with an equal off-shell momentum in the Landau gauge. This method, without invoking any effective theory, enables us to construct the weak four-quark operators exhibiting good chiral behavior. Our results for BK with the nonperturbative mixing coefficients show small scaling violation beyond the lattice cutoff a-1∼2.5 GeV. Our estimate concludes BK(NDR,2 GeV)=0.69(7) at a-1=2.7–4.3 GeV, which agrees with the value obtained with the Kogut-Susskind quark action. For comparison we also calculate BK with one-loop perturbative mixing coefficients. While this yields incorrect values at finite lattice spacing, a linear extrapolation to the continuum limit as a function of a leads to a result consistent with those obtained with the Ward identity method.

著者

Ejiri S. Iwasaki Y. Kanaya K.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.58, no.9, pp.094505, 1998-10

被引用文献数

19 24

---

We propose a new nonperturbative method to compute the 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 Nt=4–6. In both cases, there is a clear discrepancy between our results and perturbative values. A long standing problem, when one uses the perturbative anisotropy coefficients, is a nonvanishing pressure gap at the deconfining transition point in the SU(3) gauge theory. Using our nonperturbative anisotropy coefficients, we find that this problem is completely resolved: we obtain Δp/T4=0.001(15) and -0.003(17) on Nt=4 and 6 lattices, respectively.

著者

Aoki S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kuramashi Y. Okawa M. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.58, no.5, pp.054503, 1998-07

被引用文献数

13 39

---

We present a calculation for the K+→π+π0 decay amplitude using a quenched simulation of lattice QCD with the Wilson quark action at β=6/g2=6.1. The decay amplitude is extracted from the ratio, the K→ππ three-point function divided by either K and π meson two-point functions or K meson two-point function and I=2 ππ four-point function; the two different methods yield consistent results. Finite size effects are examined with calculations made on 243×64 and 323×64 lattices, and are shown that they are explained by one-loop effects of chiral perturbation theory. The lattice amplitude is converted to the continuum value by employing a one-loop calculation of chiral perturbation theory, yielding a value in agreement with experiment if extrapolated to the chiral limit. We also report on the K meson B parameter BK obtained from the K+→π+π0 amplitude using chiral perturbation theory.

著者

Aoki S. Fukugita M. Hashimoto S. Ishikawa K-I. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Okawa M. Onogi T. Tsutsui N. Ukawa A. Yamada N. Yoshié T.

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.91, no.21, pp.212001, 2003-11

被引用文献数

63 155

---

We present an unquenched lattice calculation for the B0-B̅ 0 transition amplitude. The calculation, carried out at an inverse lattice spacing 1/a=2.22(4)  GeV, incorporates two flavors of dynamical quarks described by the O(a)-improved Wilson fermion action and heavy quarks described by nonrelativistic QCD. Particular attention is paid to the uncertainty that arises from the chiral extrapolation, especially the effect of pion loops, for light quarks, which we find could be sizable for the leptonic decay constant, whereas it is small for the B parameters. We obtain fBd=191(10)(-22+12)   MeV, fBs/fBd=1.13(3)(-2+13), BBd(mb)=0.836(27)(-62+56), BBs/BBd=1.017(16)(-17+56), and ξ=1.14(3)(-2+13), where the first error is statistical, and the second is systematic, including uncertainties due to chiral extrapolation, finite lattice spacing, heavy quark expansion, and perturbative operator matching.

著者

Kanda A. Baelus B. J. Peeters F. M. Kadowaki K. Ootuka Y.

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.93, no.25, pp.257002, 2004-12

被引用文献数

233 187

---

The response of a mesoscopic superconducting disk to perpendicular magnetic fields is studied by using the multiple-small-tunnel-junction method, in which transport properties of several small tunnel junctions attached to the disk are measured simultaneously. This allows us to make the first experimental distinction between the giant vortex states and multivortex states. Moreover, we experimentally find a magnetic-field induced rearrangement and combination of vortices. The experimental results are well reproduced in numerical results based on the nonlinear Ginzburg-Landau theory.

著者

Sasagawa Y. Katanuma I. Mizoguchi Y. Cho T. Pastukhov V. P.

出版者

American Institute of Physics

雑誌

Physics of Plasmas (ISSN:1070664X)

巻号頁・発行日

vol.13, no.12, pp.122506, 2006-12-18

被引用文献数

9 9

---

Magnetohydrodynamic stabilization of an axisymmetric mirror plasma with a magnetic divertor is studied. An equation is found for the flute modes, which includes the stabilizing influence of ion temperature anisotropy and nonparaxial magnetic fields, as well as a finite ion Larmor radius. It is shown that if the density profile is sufficiently gentle, then the nonparaxial configuration can stabilize all modes as long as ion temperature is radially uniform. This can be demonstrated even when the density vanishes on the separatrix and even for small ion Larmor radii. It is found, however, that the ion temperature gradient makes the unstable region wider; high ion temperature is required to stabilize the flute mode.

著者

Katanuma I. Yagi K. Nakashima Y. Ichimura M. Imai T.

出版者

American Institute of Physics

雑誌

Physics of Plasmas (ISSN:1070664X)

巻号頁・発行日

vol.17, no.3, pp.032303, 2010-03

被引用文献数

8 7

---

The computer code by reduced magnetohydrodynamic equations were made which can simulate the flute interchange modes (similar to the Rayleigh–Taylor instability) and the instability associated with the presence of nonuniform plasma flows (similar to the Kelvin–Helmholtz instability). This code is applied to a model divertor and the GAMMA10 [ M. Inutake et al., Phys. Rev. Lett. 55, 939 (1985) ] with divertor in order to investigate the flute modes in these divertor cells. The linear growth rate of the flute instability determined by the nonlocal linear analysis agrees with that in the linear phase of the simulations. There is a stable nonlinear steady state in both divertor cells, but the nonlinear steady state is different between the model divertor and the GAMMA10 with divertor.

著者

Katanuma I. Yagi K. Haraguchi Y. Ichioka N. Masaki S. Ichimura M. Imai T.

出版者

American Institute of Physics

雑誌

Physics of plasmas (ISSN:1070664X)

巻号頁・発行日

vol.17, no.11, pp.112506, 2010-11

被引用文献数

8 7

---

The flute instability and the associated radial transport are investigated in the tandem mirror with a divertor mirror cell (the GAMMA10 A-divertor) with help of computer simulation, where GAMMA10 is introduced [ Inutake et al., Phys. Rev. Lett. 55, 939 (1985) ]. The basic equations used in the simulation were derived on the assumption of an axisymmetric magnetic field. So the high plasma pressure in a nonaxisymmetric minimum-B anchor mirror cell, which is important for the flute mode stability, is taken into account by redefining the specific volume of a magnetic field line. It is found that the flute modes are stabilized by the minimum-B magnetic field even with a divertor mirror although its stabilizing effects are weaker than that without the divertor mirror. The flute instability enhances the radial transport by intermittently repeating the growing up and down of the Fourier amplitude of the flute instability in time.

著者

Turkoglu F Koseoglu H Demirhan Y Ozyuzer L Preu S Malzer S Simsek Y Müller P Yamamoto T Kadowaki K

出版者

IOP Publishing

雑誌

Superconductor science & technology (ISSN:09532048)

巻号頁・発行日

vol.25, no.12, pp.125004, 2012-10

被引用文献数

39 16

---

We fabricated rectangular mesa structures of superconducting Bi2Sr2CaCu2O8+d (Bi2212) using e-beam lithography and Ar ion beam etching techniques for terahertz (THz) emission. c-axis resistance versus temperature (R–T), current–voltage (I–V) characteristics and bolometric THz power measurements were performed to characterize Bi2212 mesas. The emission frequency of mesas was determined using a Michelson interferometer setup which also demonstrates polarized emission. Interference patterns of THz radiation from Bi2212 mesas were detected by various detectors such as a liquid helium cooled silicon composite bolometer, a Golay cell and a pyroelectric detector. An emitted power as high as 0.06 mW was detected from Bi2212 mesas. For the first time, most of the pumped power was extracted as THz emission from a Bi2212 mesa. The radiation at 0.54 THz was detected using the Michelson interferometric setup.

著者

Sawaki D. Kobayashi W. Moritomo Y. Terasaki I.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.8, pp.081915, 2011-02

被引用文献数

104 26

---

We investigate thermal rectification in a bulk material with a pyramid shape to elucidate shape dependence of the thermal rectification, and find that rectifying coefficient R is 1.35 for this shape, which is smaller than R = 1.43 for a rectangular shape. This result is fully duplicated by our numerical calculation based on Fourier’s law. We also apply this calculation to a given shape, and show a possible way to increase R depending on the shape.

著者

Egorov A. Yu. Kalevich V. K. Afanasiev M. M. Shiryaev A. Yu. Ustinov V. M. Ikezawa M. Masumoto Y.

出版者

American Institute of Physics

雑誌

Journal of applied physics (ISSN:00218979)

巻号頁・発行日

vol.98, no.1, pp.013539, 2005-07

被引用文献数

24

---

The paper studies the circularly polarized photoluminescence (PL) from dilute GaAsN alloys with nitrogen content of 1%–3.4%, grown on GaAs substrates. The room-temperature PL is found to consist of two bands whose splitting grows with increasing nitrogen content. The analysis of the PL circular polarization has shown that the PL bands originate from the splitting of light- and heavy-hole subbands, induced by an elastic strain in GaAsN layer. The dependence of the energy gap of unstrained GaAsN on the nitrogen content has been calculated using the measured light- and heavy-hole splittings.

著者

中嶋 眞弓 大野 耕一 竹内 由則 竹内 文乃 中島 亘 Fujino Y. 辻本 元

出版者

日本ペット栄養学会

雑誌

ペット栄養学会誌 (ISSN:13443763)

巻号頁・発行日

vol.15, no.2, pp.65-71, 2012-10-10 (Released:2013-01-25)

参考文献数

22

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重症動物の蛋白質やエネルギー摂取不足による低栄養状態を短期的かつ客観的に評価するため、医学領域において動的栄養指標蛋白として利用されている急速代謝回転蛋白 (RTP) のうち血漿トランスフェリン (Tf)、レチノール結合蛋白 (RBP) のイヌにおける有用性について検討した。健常イヌにおける短期的な給餌量調整試験では、給餌制限に伴いTf値は有意に低下し、給餌再増量に伴い上昇傾向を認めたが、RBP、ALB値に関しては一定の傾向は認められなかった。臨床例における検討では1週間以上50%以上安静時エネルギー必要量 (RER) を維持している慢性消化器疾患症例と比較して、摂取量が50%未満RERである食欲不振症例のTf値は有意に低値を示した。積極的な栄養療法を行った2症例におけるTf値の経時的測定では、上昇を認めた症例では経過良好であったが、徐々に下降した症例では斃死した。今回の結果からイヌの血漿Tf値測定は動的栄養指標蛋白として有用である事が示唆された。