114 research outputs found
Dynamical correlation functions of the XXZ spin-1/2 chain
We derive a master equation for the dynamical spin-spin correlation functions
of the XXZ spin-1/2 Heisenberg finite chain in an external magnetic field. In
the thermodynamic limit, we obtain their multiple integral representation.Comment: 25 page
Staggered dimer order in S=1/2 quantum spin ladder system with four spin exchange
We study the S=1/2 quantum spin ladder system with the four-spin exchange,
using density matrix renormalization group method and an exact diagonalization
method. Recently, the phase transition in this system and its universality
class are studied. But there remain controversies whether the phase transition
is second order type or the other type and the nature of order parameter. There
are arguments that the massless phase appears. But this does not agree with our
previous result. Analyzing DMRG data, we try a new approach in order to
determine a phase which appears after the phase transition. We find that the
edge state appears in the open boundary condition, investigating excitation
energies of states with higher magnetizations.Comment: Submitted to Phys. Rev. B, (REVTeX4
The Microarcsecond Sky and Cosmic Turbulence
Radio waves are imprinted with propagation effects from ionized media through
which they pass. Owing to electron density fluctuations, compact sources
(pulsars, masers, and compact extragalactic sources) can display a wide variety
of scattering effects. These scattering effects, particularly interstellar
scintillation, can be exploited to provide *superresolution*, with achievable
angular resolutions (<~ 1 microarcsecond) far in excess of what can be obtained
by very long baseline interferometry on terrestrial baselines. Scattering
effects also provide a powerful sub-AU probe of the microphysics of the
interstellar medium, potentially to spatial scales smaller than 100 km, as well
as a tracer of the Galactic distribution of energy input into the interstellar
medium through a variety of integrated measures. Coupled with future gamma-ray
observations, SKA observations also may provide a means of detecting fainter
compact gamma-ray sources. Though it is not yet clear that propagation effects
due to the intergalactic medium are significant, the SKA will either detect or
place stringent constraints on intergalactic scattering.Comment: 20 pages, 8 figures in 8 PostScript files, to appear in "Science with
the Square Kilometer Array," eds. C. Carilli and S. Rawlings, New Astronomy
Reviews (Elsevier: Amsterdam
Nonlinear excitations in CsNiF3 in magnetic fields perpendicular to the easy plane
Experimental and numerical studies of the magnetic field dependence of the
specific heat and magnetization of single crystals of CsNiF3 have been
performed at 2.4 K, 2.9 K, and 4.2 K in magnetic fields up to 9 T oriented
perpendicular to the easy plane. The experimental results confirm the presence
of the theoretically predicted double peak structure in the specific heat
arising from the formation of nonlinear spin modes. The demagnetizing effects
are found to be negligible, and the overall agreement between the data and
numerical predictions is better than reported for the case when the magnetic
field was oriented in the easy plane. Demagnetizing effects might play a role
in generating the difference observed between theory and experiment in previous
work analyzing the excess specific heat using the sine-Gordon model.Comment: 6 pages, 5 figures, submitted to Phys. Rev.
ENSINO E AVALIAÇÃO NO ENSINO SUPERIOR: REFLEXÕES A PARTIR DA PESQUISA REALIZADA NO ÂMBITO DO PROJETO AVENA
Plantas medicinais conhecidas por especialistas locais de uma comunidade rural maranhense
Recuperação funcional de cães com doença do disco intervertebral toracolombar submetidos ao tratamento cirúrgico
Avaliação das atividades antimicrobiana, citotóxica, moluscicida e antioxidante de Bromelia antiacantha Bertol. (Bromeliaceae)
- …