783 research outputs found
Temperature dependent spatial oscillations in the correlations of the XXZ spin chain
We study the correlation for the XXZ chain in the
massless attractive (ferromagnetic) region at positive temperatures by means of
a numerical study of the quantum transfer matrix. We find that there is a range
of temperature where the behavior of the correlation for large separations is
oscillatory with an incommensurate period which depends on temperature.Comment: 4 pages, REVTEX, 6 table
Fusion Operators in the Generalized -model and Root-of-unity Symmetry of the XXZ Spin Chain of Higher Spin
We construct the fusion operators in the generalized -model using
the fused -operators, and verify the fusion relations with the truncation
identity. The algebraic Bethe ansatz discussion is conducted on two special
classes of which include the superintegrable chiral Potts model.
We then perform the parallel discussion on the XXZ spin chain at roots of
unity, and demonstrate that the -loop-algebra symmetry exists for the
root-of-unity XXZ spin chain with a higher spin, where the evaluation
parameters for the symmetry algebra are identified by the explicit
Fabricius-McCoy current for the Bethe states. Parallels are also drawn to the
comparison with the superintegrable chiral Potts model.Comment: Latex 33 Pages; Typos and errors corrected, New improved version by
adding explanations for better presentation. Terminology in the content and
the title refined. References added and updated-Journal versio
String Breaking in Non-Abelian Gauge Theories with Fundamental Matter Fields
We present clear numerical evidence for string breaking in three-dimensional
SU(2) gauge theory with fundamental bosonic matter through a mixing analysis
between Wilson loops and meson operators representing bound states of a static
source and a dynamical scalar. The breaking scale is calculated in the
continuum limit. In units of the lightest glueball we find . The implications of our results for QCD are discussed.Comment: 4 pages, 2 figures; equations (4)-(6) corrected, numerical results
and conclusions unchange
Field-induced Commensurate-Incommensurate phase transition in a Dzyaloshinskii-Moriya spiral antiferromagnet
We report an observation of a commensurate-incommensurate phase transition in
a Dzyaloshinskii-Moriya spiral magnet Ba_2CuGe_2O_7. The transition is induced
by applying a magnetic field in the plane of spin rotation. In this experiment
we have direct control over the strength of the commensurate potential, while
the preferred incommensurate period of the spin system remains unchanged.
Experimental results for the period of the soliton lattice and bulk
magnetization as a function of external magnetic field are in quantitative
agreement with theory.Comment: 4 pages, 4 figures, submitted to PR
Hipparcos red stars in the HpV_{T2} and VI_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibrated
instantaneous (epoch) Cousins color indices using newly derived
photometry. Three new sets of ground-based Cousins data have
been obtained for more than 170 carbon and red M giants. These datasets in
combination with the published sources of photometry served to obtain the
calibration curves linking Hipparcos/Tycho with the Cousins
index. In total, 321 carbon stars and 4464 M- and S-type stars have new
indices. The standard error of the mean is about 0.1 mag or better down
to although it deteriorates rapidly at fainter magnitudes. These
indices can be used to verify the published Hipparcos color
indices. Thus, we have identified a handful of new cases where, instead of the
real target, a random field star has been observed. A considerable fraction of
the DMSA/C and DMSA/V solutions for red stars appear not to be warranted. Most
likely such spurious solutions may originate from usage of a heavily biased
color in the astrometric processing.Comment: 10 figures, 1 electronic table, accepted in A&
Theory of Pump Depletion and Spike Formation in Stimulated Raman Scattering
By using the inverse spectral transform, the SRS equations are solved and the
explicit output data is given for arbitrary laser pump and Stokes seed profiles
injected on a vacuum of optical phonons. For long duration laser pulses, this
solution is modified such as to take into account the damping rate of the
optical phonon wave. This model is used to interprete the experiments of Druhl,
Wenzel and Carlsten (Phys. Rev. Lett., (1983) vol. 51, p. 1171), in particular
the creation of a spike of (anomalous) pump radiation. The related nonlinear
Fourier spectrum does not contain discrete eigenvalue, hence this Raman spike
is not a soliton.Comment: LaTex file, includes two figures in LaTex format, 9 page
Nonadiabatic Approach to Spin-Peierls Transitions via Flow Equations
The validity of the adiabatic approach to spin-Peierls transitions is
assessed. An alternative approach is developed which maps the initial
magneto-elastic problem to an effective magnetic problem only. Thus the
equivalence of magneto-elastic solitons and magnetic spinons is shown. No soft
phonon is required for the transition. Temperature dependent couplings are
predicted in accordance with the analysis of experimental data.Comment: Latex, 4 pages, Phys. Rev. B, Rap. Comm. in press final version
containing some clarification
Construction of some missing eigenvectors of the XYZ spin chain at the discrete coupling constants and the exponentially large spectral degeneracy of the transfer matrix
We discuss an algebraic method for constructing eigenvectors of the transfer
matrix of the eight vertex model at the discrete coupling parameters. We
consider the algebraic Bethe ansatz of the elliptic quantum group for the case where the parameter satisfies for arbitrary integers , and . When or
is odd, the eigenvectors thus obtained have not been discussed previously.
Furthermore, we construct a family of degenerate eigenvectors of the XYZ spin
chain, some of which are shown to be related to the loop algebra
symmetry of the XXZ spin chain. We show that the dimension of some degenerate
eigenspace of the XYZ spin chain on sites is given by , if
is an even integer. The construction of eigenvectors of the transfer matrices
of some related IRF models is also discussed.Comment: 19 pages, no figure (revisd version with three appendices
Field-induced incommensurate-to-commensurate transition in Ba_2CuGe_2O_7
We report an observation of a commensurate-incommensurate phase transition in
the Dzyaloshinskii-Moriya spiral antiferromagnet Ba_2 Cu Ge_2 O_7. The
transition is induced by an external magnetic field applied along the c-axis of
the tetragonal structure, i. e., in the plane of spin rotation. Bulk magnetic
measurements and neutron diffraction experiments show that the transition
occurs in a critical field Hc=2.1T. Experimental results for the period of the
magnetic structure and magnetization as functions of magnetic field are in
quantitative agreement with our exact analytical solution for Dzyaloshinskii's
model of commensurate-incommensurate transitions in spiral magnets.Comment: 11 double column pages, 9 figures, submitted to PR
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