70,175 research outputs found
Quantum Phase Transition of S=1/2 Trimerized XXZ Spin Chain in Magnetic Field
We study the magnetization plateau at a third of the saturation magnetization
of the S=1/2 trimerized XXZ spin chain at T=0. The appearance of the plateau
depends on the values of the XXZ anisotropy and the magnitude of the
trimerization. This plateauful-plateauless transition is a quantum phase
transition of the Berezinskii-Kosterlitz-Thouless type, which is difficult to
precisely detect from the numerical data. To determine the phase boundary line
of this transition precisely, we use the level crossing of low-lying
excitations obtained from the numerical diagonalization. We also discuss the
S=1/2 ferromagnetic-ferromagnetic-antiferromagnetic chain.Comment: LaTeX2e, 4 pages, 2eps figures, submitted to conference on Strongly
Correlated Electron System
Inversion phenomenon and phase diagram of the distorted diamond chain with the interaction anisotropy
We discuss the anisotropies of the Hamiltonian and the wave-function in an
distorted diamond chain. The ground-state phase diagram of this model
is investigated using the degenerate perturbation theory up to the first order
and the level spectroscopy analysis of the numerical diagonalization data. In
some regions of the obtained phase diagram, the anisotropy of the Hamiltonian
and that of the wave-function are inverted, which we call inversion phenomenon;
the N\'{e}el phase appears for the XY-like anisotropy and the spin-fluid phase
appears for the Ising-like anisotropy. Three key words are important for this
nature, which are frustration, the trimer nature, and the anisotropy.Comment: 4pages, 10 figures, for proceedings of SPQS 200
Distribution of TT virus (TTV), TTV-like minivirus, and related viruses in humans and nonhuman primates
AbstractTT virus (TTV) and TTV-like minivirus (TLMV) are small DNA viruses with single-stranded, closed circular, antisense genomes infecting man. Despite their extreme sequence heterogeneity (>50%), a highly conserved region in the untranslated region (UTR) allows both viruses to be amplified by polymerase chain reaction (PCR). TTV/TLMV infection was detected in 88 of 100 human plasma samples; amplified sequences were differentiated into TTV and TLMV by analysis of melting profiles, showing that both viruses were similarly prevalent. PCR with UTR primers also detected frequent infection with TTV/TLMV-related viruses in a wide range of apes (chimpanzees, gorillas, orangutans, gibbons) and African monkey species (mangabeys, drills, mandrills). These findings support the hypothesis for the co-evolution of TTV-like viruses with their hosts over the period of primate speciation, potentially analogous to the evolution of primate herpesviruses
Inversion Phenomena of the Anisotropies of the Hamiltonian and the Wave-Function in the Distorted Diamond Type Spin Chain
We investigate the ground-sate phase diagram of the XXZ version of the S=1/2
distorted diamond chain by use of the degenerate perturbation theory near the
truncation point. In case of the XY-like interaction anisotropy, the phase
diagram consists of the Neel phase and the spin-fluid phase. For the Ising-like
interaction anisotropy case, it consists of three phases: the ferrimagnetic
phase, the Neel phase and the spin-fluid phase. The magnetization in the
ferrimagnetic phase is 1/3 of the saturation magnetization. The remarkable
nature of the phase diagram is the existence of the Neel phase, although the
interaction anisotropy is XY-like. And also, the spin-fluid phase appears in
spite of the Ising-like interaction anisotropy. We call these regions
"inversion regions".Comment: 7 pages, 4 figure
Level Spectroscopy: Physical Meaning and Application to the Magnetization Plateau Problems
We review the level spectroscopy, which is a powerful method of analyzing the
numerical data with respect to the Berezinskii-Kosterlitz-Thouless quantum
phase transition in one dimension. We focus on its physical meaning and also
its application to the magnetization plateau problems.Comment: 6 pages, 3 figures (embedded), Conference paper:
Yukawa-Institute-for-Theoretical-Physics International Workshop "Order,
Disorder, and Dynamics in Quantum Spin Systems" (Nov.15-16,2001): will be
published as a special issue of Supplement Prog. Theor. Phys. Several
refereces are added and typos are correcte
Cosmological pseudobulge formation
Bulges can be classified into classical and pseudobulges; the former are
considered to be end products of galactic mergers and the latter to form via
secular evolution of galactic disks. Observationally, bulges of disk galaxies
are mostly pseudobulges, including the Milky Way's. We here show, by using
self-consistent cosmological simulations of galaxy formation, that the
formation of pseudobulges of Milky Way-sized disk galaxies has mostly completed
before disk formation; thus the main channel of pseudobulge formation is not
secular evolution of disks. Our pseudobulges form by rapid gas supply at
high-redshift and their progenitors would be observed as high-redshift disks.Comment: 3 pages, 2 figures, to appear in the proceedings of `First Stars IV -
from Hayashi to the future', M. Umemura, K. Omukai (eds.
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