著者

Taniguchi Yusuke

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.63, no.1, pp.014502, 2000-12

被引用文献数

24 31

---

The one loop correction to the SUSY Ward-Takahashi identity is calculated on the lattice with a Wilson fermion. The supersymmetry on the lattice is broken explicitly by the gluino mass and the lattice artifact. We should fine-tune the parameters in the theory to the point given by the additive mass correction in order to eliminate the breaking effect of the lattice artifact. It is shown that the additive mass correction appearing from the SUSY Ward-Takahashi identity coincide with that from the axial U(1)R symmetry, as suggested by Curci and Veneziano. Two important symmetries of the super Yang-Mills theory can be recovered simultaneously in the continuum with a single fine-tuning. The operator mixing of the supercurrent is also investigated. We find that the supercurrent mixes only with a gauge-invariant current Tμ which is related to the gamma-trace anomaly.

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

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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

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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

Izubuchi Taku Noaki Junichi Ukawa Akira

出版者

American Physical Society

雑誌

Physical review D (ISSN:15507998)

巻号頁・発行日

vol.58, no.11, pp.114507, 1998-12

被引用文献数

10 17

---

We investigate the phase structure of the two-dimensional lattice Gross-Neveu model formulated with theWilson fermion action to leading order of 1/N expansion. The structural change of the parity-broken phaseunder the influence of finite temperature and chemical potential is studied. The connection between the latticephase structure and the chiral phase transition of the continuum theory is clarified.

著者

Aoki Sinya Nagai Kei-ichi Taniguchi Yusuke Ukawa Akira

出版者

American Physical Society

雑誌

Physical review.D (ISSN:15507998)

巻号頁・発行日

vol.58, no.7, pp.074505, 1998-10

被引用文献数

44 90

---

We calculate one-loop renormalization factors of bilinear quark operators for the gluon action includingsix-link loops and an O(a)-improved quark action in the limit of a massless quark. We find that finite parts ofthe one-loop coefficients of renormalization factors diminish monotonically as either of the coefficients c1 orc21c3 of the six-link terms is decreased below zero. Detailed numerical results are given, for general valuesof the clover coefficient, for the tree-level improved gluon action in the Symanzik approach (c1521/12,c25c350) and for the choices suggested by Wilson (c1520.252,c250,c3520.17) and by Iwasaki (c1520.331,c25c350 and c1520.27,c21c3520.04) from renormalization-group analyses. Compared with thecase of the standard plaquette gluon action, the finite parts of the one-loop coefficients are reduced by 10–20 %for the Symanzik action, and approximately by a factor of 2 for the renormalization-group improved gluonactions.

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

Taniguchi Yusuke Ukawa Akira

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.58, no.11, pp.114503, 1998-10

被引用文献数

38 60

---

We calculate the O(g2a) mixing coefficients of bilinear quark operators in lattice QCD using a standard perturbative evaluation of on-shell Green’s functions. Our results for the plaquette gluon action are in agreement with those previously obtained with the Schrödinger functional method. The coefficients are also calculated for a class of improved gluon actions having six-link terms.

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

Okada Susumu Shiraishi Kenji Oshiyama Atsushi

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.90, no.2, pp.026803, 2003-01

被引用文献数

33 21

---

Based on total-energy electronic-structure calculations within the density-functional theory, we find that a high spin state is realized for an ultimate dangling bond unit on an otherwise hydrogen-covered Si(111) surface. We further propose a systematic method of constructing nanometer-scale dangling bond networks that exhibit the ferrimagnetic spin ordering. The interplay between the electron-electron interaction and the surface reconstruction is elucidated.

著者

Boero Mauro Parrinello Michele Terakura Kiyoyuki Ikeshoji Tamio Liew Chee Chin

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.90, no.22, pp.226403, 2003-06

被引用文献数

157 118

---

A first principles study of a hydrated electron in water at ordinary and supercritical conditions is presented. In the first case, the electron cleaves a cavity in the hydrogen bond network in which six H2O molecules form the solvation shell. The electron distribution assumes an ellipsoidal shape, and the agreement of the computed and the experimental optical absorption seems to support this picture. At supercritical conditions, instead, the H-bond network is not continuous and allows us to predict that the electron localizes in preexisting cavities in a more isotropic way. Four water molecules form the solvation shell but the localization time shortens significantly.

著者

Sato T. Matsui H. Takahashi T. Ding H. Yang H.-B. Wang S.-C. Fujii T. Watanabe T. Matsuda A. Terashima T. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.91, no.15, pp.157003, 2003-10

被引用文献数

99 110

---

We report a systematic high-resolution angle-resolved photoemission spectroscopy on high-Tc superconductors Bi2Sr2Can-1CunO2n+4 (n=1–3) to study the origin of many-body interactions responsible for superconductivity. For n=2 and 3, a sudden change in the energy dispersion, so called “kink”, becomes pronounced on approaching (π,0) in the superconducting state, while a kink appears only around the nodal direction in the normal state. For n=1, the kink shows no significant temperature dependence even across Tc. This could suggest that the coupling of electrons with Q=(π,π) magnetic mode is dominant in the superconducting state for multilayered cuprates, while the interactions at the normal state and that of single-layered cuprates have a different origin.

著者

Okada Susumu Oshiyama Atsushi

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.91, no.21, pp.216801, 2003-11

被引用文献数

73 70

---

We report total-energy electronic-structure calculations that provide energetics and electronic structures of double-walled carbon nanotubes consisting of semiconducting (n,0) nanotubes. We find that optimum spacing between the walls of the nanotubes is slightly larger than the interlayer spacing of the graphite. We also find that the electronic structures of the double-walled nanotubes with the inner (7,0) nanotube are metallic with multicarrier characters in which electrons and holes exist on inner and outer nanotubes, respectively. Interwall spacing and curvature difference are found to be essential for the electron states around the Fermi level.

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

Boero Mauro Oshiyama Atsushi Silvestrelli Pier Luigi

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.91, no.20, pp.206401, 2003-11

被引用文献数

27 22

---

The displacement of an oxygen atom in pure α quartz is studied via first-principles molecular dynamics. The simulations show that when an O atom in a Si-O-Si bridge is moved away from its original equilibrium position, a new stable energy minimum can be reached. Depending on the spin state and charge Q of the system, this minimum can give rise to either a threefold oxygen (singlet ground state and Q=+1) or to an unsaturated Si atom carrying a dangling bond (triplet state). In the latter case, the hyperfine parameters associated with the 29Si dangling bond are in rather good agreement with electron paramagnetic resonance/electron nuclear double resonance experiments.

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.