21,324 research outputs found
Staggered Fermion, its Symmetry and Ichimatsu-Patterned Lattice
We investigate exact symmetries of a staggered fermion in D dimensions. The
Dirac operator is reformulated by SO(2D) Clifford algebra. The chiral symmetry,
rotational invariance and parity symmetries are clarified in any dimension.
Local scalar and pseudo-scalar modes are definitely determined, in which we
find non-standard modes. The relation to Ichimatsu-patterned lattice approach
is discussed.Comment: 3 pages, 1 figure, "Talk at Lattice2004(theory), Fermilab, June
21-26, 2004
Vacuum Structure of the Ichimatsu-Decomposed Lattice Models
We proposed an `Ichimatsu'-decomposed lattice gauge theory with fermionic
symmetries. The vacuum structures of the gauge sector with two coupling
constants () are investigated for 3-dimensional Z and
4-dimensional SU(2) cases using mean-field approximation and numerical
simulation. We found two phases on the () phase diagram for
3-dim. Z case, while the diagram is a single phase for the latter.Comment: 3 pages, 6 figures, Lattice2002(higgssusy
Comment on ``Local dimer-adatom stacking fault structures from 3x3 to 13x13 along Si(111)-7x7 domain boundaries''
Zhao et al. [Phys.Rev.B 58, 13824 (1998)] depicted several atomic structures
of domain boundaries on a Si(111) surface and criticized the article by the
present author and the co-workers. I will point out that their criticism is
incorrect and their structure models have no consistency.Comment: 2 pages. Physical Review B, to appea
Presence of 3d Quadrupole Moment in LaTiO3 Studied by 47,49Ti NMR
Ti NMR spectra of LaTiO3 are reexamined and the orbital state of this
compound is discussed. The NMR spectra of LaTiO3 taken at 1.5 K under zero
external field indicate a large nuclear quadrupole splitting. This splitting is
ascribed to the presence of the rather large quadrupole moment of 3d electrons
at Ti sites, suggesting that the orbital liquid model proposed for LaTiO3 is
inappropriate. The NMR spectra are well explained by the orbital ordering model
expressed approximately as originating from
a crystal field effect. It is also shown that most of the orbital moment is
quenched.Comment: 4 pages, 3 fugures; to appear in Phys. Rev. Let
Near-Infrared Spectroscopy of Very Low-Luminosity Young Stellar Objects in the Taurus Molecular Cloud
We have carried out near-infrared spectroscopic observations of 23 very
low-luminosity young stellar object (YSO) candidates and 5 their companions in
Heiles Cloud 2, one of the densest parts of the Taurus molecular cloud. Twelve
objects were confirmed as YSOs by Br gamma feature. The effective temperatures
of the YSOs and of the companions are estimated from the 2.26 micron feature,
the 2.21 micron feature, and the H2O band strengths. Detailed comparisons of
our photometric and spectroscopic observations with evolutionary tracks on the
HR diagram suggest some objects to be very low-mass YSOs.Comment: 15 pages, 19 figures. PASJ accepte
Atomically straight steps on vicinal Si (111) surfaces prepared by step-parallel current in the kink-up direction
We demonstrate that annealing of a vicinal Si(111) surface at about 800 C
with a direct current in the direction that ascends the kinks enhances the
formation of atomically straight step edges over micrometer lengths, while
annealing with a current in the opposite direction does not. Every straight
step edge has the same atomic configuration U(2,0), which is useful as a
template for the formation of a variety of nanostructures. A phenomenological
model based on electromigration of charged mobile atoms explains the observed
current-polarity dependent behavior.Comment: Accepted for publication in Appl. Phys. Lett. Numbers of pages and
figures are 12 and 4, respectivel
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