1,086 research outputs found
Fractional Quantum Hall Effect in Topological Flat Bands with Chern Number Two
Recent theoretical works have demonstrated various robust Abelian and
non-Abelian fractional topological phases in lattice models with topological
flat bands carrying Chern number C=1. Here we study hard-core bosons and
interacting fermions in a three-band triangular-lattice model with the lowest
topological flat band of Chern number C=2. We find convincing numerical
evidence of bosonic fractional quantum Hall effect at the filling
characterized by three-fold quasi-degeneracy of ground states on a torus, a
fractional Chern number for each ground state, a robust spectrum gap, and a gap
in quasihole excitation spectrum. We also observe numerical evidence of a
robust fermionic fractional quantum Hall effect for spinless fermions at the
filling with short-range interactions.Comment: 5 pages, 7 figures, with Supplementary Materia
Spectra of Baryons Containing Two Heavy Quarks in Potential Model
In this work, we employ the effective vertices for interaction between
diquarks (scalar or axial-vector) and gluon where the form factors are derived
in terms of the B-S equation, to obtain the potential for baryons including a
light quark and a heavy diquark. The concerned phenomenological parameters are
obtained by fitting data of mesons instead of the heavy quarkonia.
The operator ordering problem in quantum mechanics is discussed. Our numerical
results indicate that the mass splitting between and
is very small and it is consistent with the heavy quark effective
theory (HQET).Comment: 16 page
Frequency tracking by method of least squares combined with channel estimation for OFDM over mobile wireless channels
[[abstract]]To track frequency offset and time-varying channel in orthogonal frequency division multiplexing (OFDM) systems over mobile wireless channels, a common technique is, based on one OFDM training block sample, to apply the maximum-likelihood (ML) algorithm to perform joint frequency tracking and channel estimation employing some adaptive iteration processes. The major drawback of such joint estimation techniques is the local extrema problem arising from the highly nonlinear nature of the log-likelihood function. This makes the joint estimation process very difficult and complicated, and many a time the results are not very satisfactory if the algorithm is not well designed. In this study, rather than using the ML algorithm, we shall apply the method of least squares (LS) for frequency tracking utilizing repeated OFDM training blocks. As will be seen, by using such an LS approach, the frequency offset estimation requires no channel knowledge. The channel state can be estimated separately after the LS frequency offset correction. This not only circumvents the local extrema complication, but also obviates the need for the lengthy adaptive iteration process of joint estimation thus greatly simplifies the entire estimation process. Most importantly, our technique can achieve excellent estimation performance as compared to the usual ML algorithms.[[incitationindex]]SCI[[booktype]]ç´™
An FHA domain–mediated protein interaction network of Rad53 reveals its role in polarized cell growth
The DNA damage checkpoint kinase Rad53 is important for the survival of budding yeast under genotoxic stresses. We performed a biochemical screen to identify proteins with specific affinity for the two Forkhead associated (FHA) domains of Rad53. The N-terminal FHA1 domain was found to coordinate a complex protein interaction network, which includes nuclear proteins involved in DNA damage checkpoints and transcriptional regulation. Unexpectedly, cytosolic proteins involved in cytokinesis, including septins, were also found as FHA1 binding proteins. Consistent with this interaction, a Rad53 mutant defective in its nuclear localization was found to localize to the bud neck. Abnormal morphology was observed in cells overexpressing the FHA1 domain and in rad53Δ cells under DNA replication stress. Further, septin Shs1 appears to have an important role in the response to DNA replication stress. Collectively, the results suggest a novel function of Rad53 in the regulation of polarized cell growth in response to DNA replication stress
Non-Fermi-liquid d-wave metal phase of strongly interacting electrons
Developing a theoretical framework for conducting electronic fluids
qualitatively distinct from those described by Landau's Fermi-liquid theory is
of central importance to many outstanding problems in condensed matter physics.
One such problem is that, above the transition temperature and near optimal
doping, high-transition-temperature copper-oxide superconductors exhibit
`strange metal' behaviour that is inconsistent with being a traditional Landau
Fermi liquid. Indeed, a microscopic theory of a strange-metal quantum phase
could shed new light on the interesting low-temperature behaviour in the
pseudogap regime and on the d-wave superconductor itself. Here we present a
theory for a specific example of a strange metal---the 'd-wave metal'. Using
variational wavefunctions, gauge theoretic arguments, and ultimately
large-scale density matrix renormalization group calculations, we show that
this remarkable quantum phase is the ground state of a reasonable microscopic
Hamiltonian---the usual t-J model with electron kinetic energy and two-spin
exchange supplemented with a frustrated electron `ring-exchange' term,
which we here examine extensively on the square lattice two-leg ladder. These
findings constitute an explicit theoretical example of a genuine
non-Fermi-liquid metal existing as the ground state of a realistic model.Comment: 22 pages, 12 figures: 6 pages, 7 figures of main text + 16 pages, 5
figures of Supplementary Information; this is approximately the version
published in Nature, minus various subedits in the main tex
Observation of a near-threshold enhancement in th p pbar mass spectrum from radiative J/psi-->gamma p pbar decays
We observe a narrow enhancement near 2mp in the invariant mass spectrum of
ppbar pairs from radiative J/psi-->gamma ppbar decays. The enhancement can be
fit with either an S- or P-wave Breit Wigner fuction. In the case of the S-wave
fit, the peak mass is below the 2mp threshold and the full width is less than
30 MeV. These mass and width values are not consistent with the properties of
any known meson resonance.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Let
Measurements of the Cross Section for e+e- -> hadrons at Center-of-Mass Energies from 2 to 5 GeV
We report values of for 85 center-of-mass energies between
2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing
Electron-Positron Collider.Comment: 5 pages, 3 figure
First Measurement of the Branching Fraction of the Decay psi(2S) --> tau tau
The branching fraction of the psi(2S) decay into tau pair has been measured
for the first time using the BES detector at the Beijing Electron-Positron
Collider. The result is ,
where the first error is statistical and the second is systematic. This value,
along with those for the branching fractions into e+e- and mu+mu of this
resonance, satisfy well the relation predicted by the sequential lepton
hypothesis. Combining all these values with the leptonic width of the resonance
the total width of the psi(2S) is determined to be keV.Comment: 9 pages, 2 figure
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