8,246 research outputs found
BRST invariant formulation of spontaneously broken gauge theory in generalized differential geometry
Noncommutative geometry(NCG) on the discrete space successfully reproduces
the Higgs mechanism of the spontaneously broken gauge theory, in which the
Higgs boson field is regarded as a kind of gauge field on the discrete space.
We could construct the generalized differential geometry(GDG) on the discrete
space which is very close to NCG in case of .
GDG is a direct generalization of the differential geometry on the ordinary
manifold into the discrete one. In this paper, we attempt to construct the BRST
invariant formulation of spontaneously broken gauge theory based on GDG and
obtain the BRST invariant Lagrangian with the t'Hooft-Feynman gauge fixing
term.Comment: 15 page
Effect of the Zero-Mode on the Response of a Trapped Bose-Condensed Gas
The dynamical response of a trapped Bose-Einstein condensate (BEC) is
formulated consistently with quantum field theory and is numerically evaluated.
We regard the BEC as a manifestation of the breaking of the global phase
symmetry. Then, the Goldstone theorem implies the existence of a zero energy
excitation mode (the zero-mode). We calculate the effect of the zero-mode on
the response frequency and show that the contribution of the zero-mode to the
first excitation mode is not so important in the parameter set realized in the
existing experiment. This is the reason that experimental results can be
described using the Bogoliubov prescription, although it breaks the consistency
of the description in quantum field theory.Comment: 18 pages, 3 figure
Microcomputer system for medium-sized and experimental finite element analysis
The development of a microcomputer system is described. A series of finite element analysis programs are evaluated in terms of their cost effective application within the microcomputer system. It is shown that the system is practically maintenance free and can be sustained by individual laboratories of standard scale in the educational or academic environment
The vibrational predissociation spectroscopy of hydrogen cluster ions
The first infrared spectra of protonated hydrogen clusters in the gas phase have been observed. Predissociation spectra were taken with a tandem mass spectrometer: mass selected hydrogen cluster ions were irradiated inside a rf ion trap by a tunable infrared laser, and the fragment ions created by photodissociation of the clusters were mass selected and detected. Spectra for each product channel were measured by counting fragment ions as a function of laser frequency. Low resolution spectra (Deltanu=10 cm^−1) in the region from 3800 to 4200 cm^−1 were observed for the ions H + 5, H + 7, and H + 9 at 3910, 3980, and 4020 cm−1, respectively. A band was also observed for H + 5 at 3532 cm^−1. No rotational structure was resolved. The frequencies of the band maxima agree well with the frequencies predicted by previous ab initio calculations for the highest modes
The Mid-Infrared Spectrum of the Zodiacal and Exozodiacal Light
The zodiacal light is the dominant source of the mid-infrared sky brightness
seen from Earth, and exozodiacal light is the dominant emission from planetary
and debris systems around other stars. We observed the zodiacal light spectrum
with ISOCAM over 5-16 over a wide range of orientations relative to the Sun and
the ecliptic. We present theoretical models for a wide range of particle size
distributions and compositions. The observed temperature is as expected for
large (>10 um radius), low-albedo (< 0.08), rapidly-rotating, grey particles 1
AU from the Sun. In addition to the continuum, we detect a weak excess in the
9-11 um range, with an amplitude of 6% of the continuum. The shape of the
feature can be matched by a mixture of silicates: amorphous forsterite/olivine,
dirty crystalline olivine, and a hydrous silicate (montmorillonite). The
presence of hydrous silicate suggests the parent bodies of those particles were
formed in the inner solar nebula. Large particles dominate the size
distribution, but at least some small particles (radii ~1 um) are required to
produce the silicate emission feature. To compare the properties of zodiacal
dust to dust around other main sequence stars, we reanalyzed the exozodiacal
light spectrum for Beta Pic. The exozodiacal spectra are dominated by cold
dust, with emission peaking in the far-infrared, while the zodiacal spectrum
peaks around 20 um. The shape of the silicate feature from Beta Pic is nearly
identical to that derived from the ISO spectrum of 51 Oph; both exozodiacal
features are very different from that of the zodiacal light. The exozodiacal
features are roughly triangular, peaking at 10.3 um while the zodiacal feature
is more boxy.Comment: accepted to Icaru
Infrared spectra of the cluster ions H7O<sup> + </sup><sub>3</sub>·H2 and H9O<sup> + </sup><sub>4</sub>·H2
Infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O + 3 ·H2 and H9O + 4 ·H2, have been observed. Mass-selected parent ions, trapped in a radio frequency ion trap, are excited by a tunable infrared laser; following absorption, the complex predissociates with loss of the H2, and the resulting fragment ions are detected. Spectra have been taken from 3000 to 4000 cm^−1, with a resolution of 1.2 cm^−1. They are compared to recent theoretical and experimental spectra of the hydronium ion hydrates alone. Binding an H2 molecule to these clusters should only weakly perturb their vibrations; if so, our spectra should be similar to spectra of the hydrated hydronium ions H7O + 3 and H9O + 4
Dense and Warm Molecular Gas between Double Nuclei of the Luminous Infrared Galaxy NGC 6240
High spatial resolution observations of the 12CO(1-0), HCN(1-0), HCO+(1-0),
and 13CO(1-0) molecular lines toward the luminous infrared merger NGC 6240 have
been performed using the Nobeyama Millimeter Array and the RAINBOW
Interferometer. All of the observed molecular emission lines are concentrated
in the region between the double nuclei of the galaxy. However, the
distributions of both HCN and HCO+ emissions are more compact compared with
that of 12CO, and they are not coincident with the star-forming regions. The
HCN/12CO line intensity ratio is 0.25; this suggests that most of the molecular
gas between the double nuclei is dense. A comparison of the observed high
HCN/13CO intensity ratio, 5.9, with large velocity gradient calculations
suggests that the molecular gas is dense [n(H_2)=10^{4-6} cm^-3] and warm
(T_kin>50 K). The observed structure in NGC 6240 may be explained by time
evolution of the molecular gas and star formation, which was induced by an
almost head-on collision or very close encounter of the two galactic nuclei
accompanied with the dense gas and star-forming regions.Comment: 25 pages, 8 figures, To be appeared in PASJ 57, No.4 (August 25,
2005) issu
Mott Phase in Polarized Two-component Atomic Fermi Lattice Gas:A Playground for S=1/2 Heisenberg Model in Magnetic Field
We investigate effects of pseudo-spin population imbalance on Mott phases in
1D trapped two-component atomic Fermi gases loaded on optical lattices based on
the repulsive Hubbard model in harmonic traps. By using the density matrix
renormalization group method, we numerically calculate density profiles of each
component and clarify the pseudo-spin magnetism. Consequently, we find that all
the features from weakly imbalance to fully polarized cases are well described
by S=1/2 antiferromagnetic Heisenberg chain under magnetic field. These results
indicate that the Mott phases offer experimental stages for studying various
interacting spin systems
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