455,548 research outputs found
Interlayer Coherence in the and Bilayer Quantum Hall States
We have measured the Hall-plateau width and the activation energy of the
bilayer quantum Hall (BLQH) states at the Landau-level filling factor
and 2 by tilting the sample and simultaneously changing the electron density in
each quantum well. The phase transition between the commensurate and
incommensurate states are confirmed at and discovered at . In
particular, three different BLQH states are identified; the compound
state, the coherent commensurate state, and the coherent incommensurate state.Comment: 4 pages including 5 figure
Spin-Pseudospin Coherence and CP Skyrmions in Bilayer Quantum Hall Ferromagnets
We analyze bilayer quantum Hall ferromagnets, whose underlying symmetry group
is SU(4). Spin-pseudospin coherence develops spontaneously when the total
electron density is low enough. Quasiparticles are CP^3 skyrmions. One skyrmion
induces charge modulations on both of the two layers. At the filling factor one elementary excitation consists of a pair of skyrmions and its charge
is . Recent experimental data due to Sawada et al. [Phys. Rev. Lett. {\bf
80}, 4534 (1998)] support this conclusion.Comment: 4 pages including 2 figures (published version
Synthetic horizontal branch morphology for different metallicities and ages under tidally enhanced stellar wind
It is believed that, except for metallicity, some other parameters are needed
to explain the horizontal branch (HB) morphology of globular clusters (GCs).
Furthermore, these parameters are considered to be correlated with the mass
loss of the red giant branch (RGB) stars. In our previous work, we proposed
that tidally enhanced stellar wind during binary evolution may affect the HB
morphology by enhancing the mass loss of the red giant primary. As a further
study, we now investigate the effects of metallicity and age on HB morphology
by considering tidally enhanced stellar winds during binary evolution. We
incorporated the tidally enhanced-stellar-wind model into Eggleton's stellar
evolution code to study the binary evolution. To study the effects of
metallicity and age on our final results, we conducted two sets of model
calculations: (i) for a fixed age, we used three metallicities, namely
Z=0.0001, 0.001, and 0.02. (ii) For a fixed metallicity, Z=0.001, we used five
ages in our model calculations: 14, 13, 12, 10, and 7 Gyr. We found that HB
morphology of GCs becomes bluer with decreasing metallicity, and old GCs
present bluer HB morphology than young ones. These results are consistent with
previous work. Although the envelope-mass distributions of zero-age HB stars
produced by tidally enhanced stellar wind are similar for different
metallicities, the synthetic HB under tidally enhanced stellar wind for Z=0.02
presented a distinct gap between red and blue HB. However, this feature was not
seen clearly in the synthetic HB for Z=0.001 and 0.0001. We also found that
higher binary fractions may make HB morphology become bluer, and we discussed
the results with recent observations.Comment: 16 pages, 6 figures, 3 tables, accepted for publication in Astronomy
& Astrophysic
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