266 research outputs found
Effect of the tensor force in the exchange channel on the spin-orbit splitting in 23F in the Hartree-Fock framework
We study the spin-orbit splitting (-splitting) for the proton d-orbits in
23F in the Hartree-Fock framework with the tensor force in the exchange
channel. 23F has one more proton around the neutron-rich nucleus 22O. A recent
experiment indicates that the ls-splitting for the proton d-orbits in 23F is
reduced from that in 17F. Our calculation shows that the ls-splitting in 23F
becomes smaller by about a few MeV due to the tensor force. This effect comes
from the interaction between the valence proton and the occupied neutrons in
the 0d5/2 orbit through the tensor force and makes the ls-splitting in 23F
close to the experimental data
Frustration-induced eta inversion in the S=1/2 bond-alternating spin chain
We study the frustration-induced enhancement of the incommensurate
correlation for a bond-alternating quantum spin chain in a magnetic field,
which is associated with a quasi-one-dimensional organic compound F5PNN. We
investigate the temperature dependence of the staggered susceptibilities by
using the density matrix renormalization group, and then find that the
incommensurate correlation becomes dominant in a certain range of the magnetic
field. We also discuss the mechanism of this enhancement on the basis of the
mapping to the effective S=1/2 XXZ chain and a possibility of the field-induced
incommensurate long range order.Comment: 4 pages, 5 figures, replaced with revised version accepted to PR
2018 Convocation
Welcome: Katie Berger, Executive Director of Student Affairs Pledge of Allegiance: Srivinay Tummarakota \u2719, Student Council President Opening Remarks: José M. Torres, Ph.D., President Opening Remarks: Robert Hernandez, Ph.D., Principal Featured Musical Selection: Luke Musgrave, Class of 2015 Keynote Address: Kiyomi Hamilton, Class of 2000, General Operations Manager at McMaster-Carr Closing Remarks: Robert Hernandez, Ph.D., Principa
How to distinguish the Haldane/Large-D state and the intermediate-D state in an S=2 quantum spin chain with the XXZ and on-site anisotropies
We numerically investigate the ground-state phase diagram of an S=2 quantum
spin chain with the and on-site anisotropies described by , where denotes the XXZ anisotropy parameter of the
nearest-neighbor interactions and the on-site anisotropy parameter. We
restrict ourselves to the and case for simplicity. Our main
purpose is to obtain the definite conclusion whether there exists or not the
intermediate- (ID) phase, which was proposed by Oshikawa in 1992 and has
been believed to be absent since the DMRG studies in the latter half of 1990's.
In the phase diagram with and there appear the XY state, the
Haldane state, the ID state, the large- (LD) state and the N\'eel state. In
the analysis of the numerical data it is important to distinguish three gapped
states; the Haldane state, the ID state and the LD state. We give a physical
and intuitive explanation for our level spectroscopy method how to distinguish
these three phases.Comment: Proceedings of "International Conference on Frustration in Condensed
Matter (ICFCM)" (Jan. 11-14, 2011, Sendai, Japan
A Great Space Weather Event in February 1730
Aims. Historical records provide evidence of extreme magnetic storms with
equatorward auroral extensions before the epoch of systematic magnetic
observations. One significant magnetic storm occurred on February 15, 1730. We
scale this magnetic storm with auroral extension and contextualise it based on
contemporary solar activity. Methods. We examined historical records in East
Asia and computed the magnetic latitude (MLAT) of observational sites to scale
magnetic storms. We also compared them with auroral records in Southern Europe.
We examined contemporary sunspot observations to reconstruct detailed solar
activity between 1729 and 1731. Results. We show 29 auroral records in East
Asian historical documents and 37 sunspot observations. Conclusions. These
records show that the auroral displays were visible at least down to 25.8{\deg}
MLAT throughout East Asia. In comparison with contemporary European records, we
show that the boundary of the auroral display closest to the equator surpassed
45.1{\deg} MLAT and possibly came down to 31.5{\deg} MLAT in its maximum phase,
with considerable brightness. Contemporary sunspot records show an active phase
in the first half of 1730 during the declining phase of the solar cycle. This
magnetic storm was at least as intense as the magnetic storm in 1989, but less
intense than the Carrington event.Comment: 30 pages, 5 figures, and 2 tables, accepted for publication in
Astronomy & Astrophysics on 25 April 2018. The figures and
transcriptions/translations of historical documents are partially omitted in
this manuscript due to the condition of reproduction. They are available in
the publisher versio
Theoretical analysis of the experiments on the double-spin-chain compound -- KCuCl
We have analyzed the experimental susceptibility data of KCuCl and found
that the data are well-explained by the double-spin-chain models with strong
antiferromagnetic dimerization. Large quantum Monte Carlo calculations were
performed for the first time in the spin systems with frustration. This was
made possible by removing the negative-sign problem with the use of the dimer
basis that has the spin-reversal symmetry. The numerical data agree with the
experimental data within 1% relative errors in the whole temperature region. We
also present a theoretical estimate for the dispersion relation and compare it
with the recent neutron-scattering experiment. Finally, the magnitude of each
interaction bond is predicted.Comment: 4 pages, REVTeX, 5 figures in eps-file
Quantum phase transitions of the asymmetric three-leg spin tube
We investigate quantum phase transitions of the S=1/2 three-leg
antiferromagnetic spin tube with asymmetric inter-chain (rung) exchange
interactions. On the basis of the electron tube system, we propose a useful
effective theory to give the global phase diagram of the asymmetric spin tube.
In addition, using other effective theories we raise the reliability of the
phase diagram. The density-matrix renormalization-group and the numerical
diagonalization analyses show that the finite spin gap appears in a narrow
region around the rung-symmetric line, in contrast to a recent paper by
Nishimoto and Arikawa [Phys. Rev. B78, 054421 (2008)]. The numerical
calculations indicate that this global phase diagram obtained by use of the
effective theories is qualitatively correct. In the gapless phase on the phase
diagram, the numerical data are fitted by a finite-size scaling in the c=1
conformal field theory. We argue that all the phase transitions between the
gapful and gapless phases belong to the Berezinskii-Kosterlitz-Thouless
universality class.Comment: 12 pages, 7 figures, 2 column, final versio
Ground state of an distorted diamond chain - model of
We study the ground state of the model Hamiltonian of the trimerized
quantum Heisenberg chain in which
the non-magnetic ground state is observed recently. This model consists of
stacked trimers and has three kinds of coupling constants between spins; the
intra-trimer coupling constant and the inter-trimer coupling constants
and . All of these constants are assumed to be antiferromagnetic. By
use of the analytical method and physical considerations, we show that there
are three phases on the plane (, ), the dimer phase, the spin fluid phase
and the ferrimagnetic phase. The dimer phase is caused by the frustration
effect. In the dimer phase, there exists the excitation gap between the
two-fold degenerate ground state and the first excited state, which explains
the non-magnetic ground state observed in . We also obtain the phase diagram on the
plane from the numerical diagonalization data for finite systems by use of the
Lanczos algorithm.Comment: LaTeX2e, 15 pages, 21 eps figures, typos corrected, slightly detailed
explanation adde
Critical Properties of the transition between the Haldane phase and the large-D phase of the spin-1/2 ferromagnetic-antiferromagnetic Heisenberg chain with on-site anisotropy"
We analytically study the ground-state quantum phase transition between the
Haldane phase and the large- (LD) phase of the
ferromagnetic-antiferromagnetic alternating Heisenberg chain with on-site
anisotropy. We transform this model into a generalized version of the
alternating antiferromagnetic Heisenberg model with anisotropy. In the
transformed model, the competition between the transverse and longitudinal bond
alternations yields the Haldane-LD transition. Using the bosonization method,
we show that the critical exponents vary continuously on the Haldane-LD
boundary. Our scaling relations between critical exponents very well explains
the numerical results by Hida.Comment: text 12 pages (Plain TeX), LaTeX sourse files of a table and a figure
on reques
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