6,061 research outputs found
Schwinger boson mean field theory of the Heisenberg Ferrimagnetic Spin Chain
The Schwinger boson mean field theory is applied to the quantum ferrimagnetic
Heisenberg chain. There is a ferrimagnetic long range order in the ground
state. We observe two branches of the low lying excitation and calculate the
spin reduction, the gap of the antiferromagnetic branch, and the spin
fluctuation at . These results agree with the established numerical
results quite well. At finite temperatures, the long range order is destroyed
because of the disappearance of the Bose condensation. The thermodynamic
observables, such as the free energy, magnetic susceptibility, specific heat,
and the spin correlation at , are calculated. The has a
minimum at intermediate temperatures and the spin correlation length behaves as
at low temperatures. These qualitatively agree with the numerical
results and the difference is small at low temperatures.Comment: 15 pages, 5 figures. Accepted by Phys. Rev.
Wave dynamics of a six-dimensional black hole localized on a tensional three-brane
We study the quasinormal modes and the late-time tail behavior of scalar
perturbation in the background of a black hole localized on a tensional
three-brane in a world with two large extra dimensions. We find that finite
brane tension modifies the standard results in the wave dynamics for the case
of a black hole on a brane with completely negligible tension. We argue that
the wave dynamics contains the imprint of the extra dimensions.Comment: revised version, 10 pages, 1 table and 2 figures. Accepted for
publication in Phys. Lett.
Relating Friedmann equation to Cardy formula in universes with cosmological constant
A relation between the Friedmann equation and the Cardy formula has been
found for de Sitter closed and Anti de Sitter flat universes. For the remaining
(Anti) de Sitter universes the arguments fail, and we speculate whether the
general philosophy of holography can be satisfied in such contents.Comment: 11 pages, Latex file, References added. New version to be published
in Phys. Lett.
- …