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
79

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
156 118

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
98 110

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.
著者
Tomita S. Andersen J. U. Bonderup E. Hvelplund P. Liu B. Brøndsted Nielsen S. Pedersen U. V. Rangama J. Hansen K. Echt O.
出版者
American Physical Society
雑誌
Physical review letters (ISSN:00319007)
巻号頁・発行日
vol.94, no.5, pp.053002, 2005-02
被引用文献数
38

We have measured the near-infrared absorption spectrum for isolated C ions at room temperature. Two bands, at 9145 cm-1 and 10460 cm-1, have been identified in addition to the main absorption band at 9382 cm-1, seen also at low temperature in a matrix. An interpretation based on the theory of dynamic Jahn-Teller effects is proposed.
著者
Kokubo N. Kadowaki K. Takita K.
出版者
American Physical Society
雑誌
Physical review letters (ISSN:00319007)
巻号頁・発行日
vol.95, no.17, pp.177005, 2005-10
被引用文献数
57

We present a mode locking (ML) phenomenon of vortex matter observed around the peak effect regime of 2H-NbSe2 pure single crystals. The ML features allow us not only to trace how the shear rigidity of driven vortices persists on approaching the second critical field, but also to demonstrate a dynamic melting transition of driven vortices at a given velocity. We observe the velocity dependent melting signatures in the peak effect regime, which reveal a crossover between the disorder-induced transition at small velocity and the thermally induced transition at large velocity. This uncovers the relationship between the peak effect and the thermal melting.
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.95, no.20, pp.206804, 2005-11
被引用文献数
45 43

A total-energy electronic-structure calculation is performed to explore energetics and electronic structures of nanotubes adsorbed on metal surfaces. We find that the charge transfer from metal surfaces to the nanotubes takes place depending on both the electronic structures of the adsorbed nanotubes and the work functions of the metal surfaces. In addition, we also find a substantial hybridization between the electron states of metal atoms and those of the nanotubes, which results in the metal-induced inhomogeneous charge distribution in the nanotubes.
著者
Umeda T. Son N. T. Isoya J. Janzén E. Ohshima T. Morishita N. Itoh H. Gali A. Bockstedte M.
出版者
American Physical Society
雑誌
Physical review letters (ISSN:00319007)
巻号頁・発行日
vol.96, pp.145501, 2006-04
被引用文献数
70

The metastability of vacancies was theoretically predicted for several compound semiconductors alongside their transformation into the antisite-vacancy pair counterpart; however, no experiment to date has unambiguously confirmed the existence of antisite-vacancy pairs. Using electron paramagnetic resonance and first principles calculations we identify the SI5 center as the carbon antisite-vacancy pair in the negative charge state (CSiV<sub>C</sub><sup>-</sup>) in 4H-SiC. We suggest that this defect is a strong carrier-compensating center in n-type or high-purity semi-insulating SiC.
著者
Kanazawa Ken Taninaka Atsushi Takeuchi Osamu Shigekawa Hidemi
出版者
American Physical Society
雑誌
Physical review letters (ISSN:00319007)
巻号頁・発行日
vol.99, no.21, pp.216102, 2007-11
被引用文献数
15 13

The structures of two competing phases and their interrelationship in the self-organization of glycine molecules on a Cu(100) surface were clarified. Despite their similar structural energies predicted using first-principles calculation, completely different mechanisms were found to stabilize the two phases. The balance and coordination of the two mechanisms that induce a variety of self-assembled structures in this attractive system were revealed. Furthermore, the importance of the microscopic arrangement of the molecules in designing the macroscopic electronic structures was directly demonstrated.
著者
Shimada Kenya Mizokawa Takashi Mamiya Kazutoshi Saitoh Tomohiko Fujimori Atsushi Ono Kanta Kakizaki Akito Ishii Takehiko Shirai Masafumi Kamimura Takashi
出版者
American Physical Society
雑誌
Physical Review B - Condensed Matter and Materials Physics (ISSN:01631829)
巻号頁・発行日
vol.57, no.15, pp.8845-8853, 1998-04-15
被引用文献数
3 43

The electronic structures of the antiferromagnetic semiconductor FeS and ferrimagnetic metals Fe7S8 and Fe7Se8 have been studied by spin-integrated and spin-resolved photoemission spectroscopy and inverse-photoemission spectroscopy. The overall Fe 3d bandwidth in the photoemission spectra is 25-30 % narrower than the density of states (DOS) predicted by first-principles band-structure calculations and is accompanied by an intense tail on the high-binding-energy side, indicating the correlated nature of electrons in the Fe 3d band. Deviation from the band DOS is more significant in Fe7S8 than in Fe7Se8, and in the minority-spin spectra than in the majority-spin spectra. Cluster-model calculation for FeS has shown satellite structures at high binding energies, but the calculated spectral line shape is not in good agreement with experiment compared to the band DOS. By introducing a self-energy correction to the band DOS, we could explain the narrowing of the overall Fe 3d bandwidth and the high-binding-energy tail shape but not for the unusual broadening of the Fe 3d band within ∼ 1 eV of the Fermi level.