5,376 research outputs found
Modified Reconstruction of Standard Model in Non-Commutative Differential Geometry
Sogami recently proposed the new idea to express Higgs particle as a kind of
gauge particle by prescribing the generalized covariant derivative with gauge
and Higgs fields operating on quark and lepton fields. The field strengths for
both the gauge and Higgs fields are defined by the commutators of the covariant
derivative by which he could obtain the Yang-Mills Higgs Lagrangian in the
standard model. Inspired by Sogami's work, we present a modification of our
previous scheme to formulate the spontaneously broken gauge theory in
non-commutative geometry on the discrete space; Minkowski space multiplied by
two points space by introducing the generation mixing matrix in operation of
the generalized derivative on the more fundamental fields a_i(x,y) which
compose the gauge and Higgs fields. The standard model is reconstructed
according to the modified scheme, which does not yields not only any special
relations between the particle masses but also the special restriction on the
Higgs potential.Comment: 21 page
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
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
BRST invariant Lagrangian of spontaneously broken gauge theories in noncommutative geometry
The quantization of spontaneously broken gauge theories in noncommutative
geometry(NCG) has been sought for some time, because quantization is crucial
for making the NCG approach a reliable and physically acceptable theory. Lee,
Hwang and Ne'eman recently succeeded in realizing the BRST quantization of
gauge theories in NCG in the matrix derivative approach proposed by Coquereaux
et al. The present author has proposed a characteristic formulation to
reconstruct a gauge theory in NCG on the discrete space .
Since this formulation is a generalization of the differential geometry on the
ordinary manifold to that on the discrete manifold, it is more familiar than
other approaches. In this paper, we show that within our formulation we can
obtain the BRST invariant Lagrangian in the same way as Lee, Hwang and Ne'eman
and apply it to the SU(2)U(1) gauge theory.Comment: RevTeX, page
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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Infrared spectroscopy of the cluster ions H<sup> + </sup><sub>3</sub>·(H2)n
The vibrational spectra of the clusters H + 3(H2)n were observed near 4000 cm−1 by vibrational predissociation spectroscopy. Spectra of mass-selected clusters were obtained by trapping the ions in a radio frequency ion trap, exciting vibrational transitions of the cluster ions to predissociating levels, and detecting the fragment ions with a mass spectrometer. Low resolution bands of the solvent H2 stretches were observed for the clusters of one to six H2 coordinated to an H + 3 ion. The red shift of these vibrations relative to the monomer H2 frequency supported the model of H + 9 as an H + 3 with a complete inner solvation shell of three H2, one bound to each corner of the ion. Two additional bands of H + 5 were observed, one assigned as the H + 3 symmetric stretch, and the other as a combination or overtone band. High-resolution scans (0.5 and 0.08 cm−1) of H + n, n=5, 7, and 9 yielded no observable rotational structure, a result of either spectral congestion or rapid cluster dissociation. The band contour of the H + 5 band changed upon cooling the internal degrees of freedom, but the peaks remained featureless. The observed frequencies of H + 7 and H + 9 agreed well with ab initio predictions, but those of H + 5 did not. This deviation is discussed in terms of the large expected anharmonicity of the proton bound dimer H + 5
The lifetimes for spontaneous emission from the X 3Sigma−(v=1) and a 1Delta states of CH−
The radiative decay of excited CH− trapped in a radio frequency ion trap was measured, and the total excited state population was probed by observing the depletion of trapped CH− caused by photodetachment at 1.16 eV, below the expected electron affinity for the ground 3Sigma− state. The signal decayed biexponentially with time. We assigned the long lived state (lifetime 5.9+0.8, −0.6 s) as the metastable a 1Delta state previously identified in the photoelectron spectrum. The fast decay, with a lifetime of 1.75±0.15 ms, was attributed to the first excited vibrational level of the ground 3Sigma− state, in good agreement with a theoretical result by Manz, Zilch, Rosmus, and Werner. These results support the electron affinity of 1.238 eV for CH− obtained by Kasdan, Herbst, and Lineberger from photoelectron spectroscopy, and contradict the value of 0.74 eV determined by Feldmann from photodetachment spectroscopy
Orbital Order, Structural Transition and Superconductivity in Iron Pnictides
We investigate the 16-band d-p model for iron pnictide superconductors in the
presence of the electron-phonon coupling g with the orthorhombic mode which is
crucial for reproducing the recently observed ultrasonic softening. Within the
RPA, we obtain the ferro-orbital order below TQ which induces the
tetragonal-orthorhombic structural transition at Ts = TQ, together with the
stripe-type antiferromagnetic order below TN. Near the phase transitions, the
system shows the s++ wave superconductivity due to the orbital fluctuation for
a large g case with TQ > TN, while the s+- wave due to the magnetic fluctuation
for a small g case with TQ < TN. The former case is consistent with the phase
diagram of doped iron pnictides with Ts > TN.Comment: 5 pages, 5 figures, minor changes, published in J. Phys. Soc. Jp
Vibrational spectroscopy of the hydrated hydronium cluster ions H3O+·(H2O)n (n=1, 2, 3)
The gas phase infrared spectra of the hydrated hydronium cluster ions H3O+·(H2O)n(n=1, 2, 3) have been observed from 3550 to 3800 cm^−1. The new spectroscopic method developed for this study is a two color laser scheme consisting of a tunable cw infrared laser with 0.5 cm^−1 resolution used to excite the O–H stretching vibrations and a cw CO2 laser that dissociates the vibrationally excited cluster ion through a multiphoton process. The apparatus is a tandem mass spectrometer with a radio frequency ion trap that utilizes the following scheme: the cluster ion to be studied is first mass selected; spectroscopic interrogation then occurs in the radio frequency ion trap; finally, a fragment ion is selected and detected using ion counting techniques. The vibrational spectra obtained in this manner are compared with that taken previously using a weakly bound H2 "messenger." A spectrum of H7 O + 3 taken using a neon messenger is also presented. Ab initio structure and frequency predictions by Remington and Schaefer are compared with the experimental results
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