2,064 research outputs found
Utility of su(1,1)-Algebra in a Schematic Nuclear su(2)-Model
The su(2)-algebraic model interacting with an environment is investigated
from a viewpoint of treating the dissipative system. By using the
time-dependent variational approach with a coherent state and with the help of
the canonicity condition, the time-evolution of this quantum many-body system
is described in terms of the canonical equations of motion in the classical
mechanics. Then, it is shown that the su(1,1)-algebra plays an essential role
to deal with this model. An exact solution with appropriate initial conditions
is obtained by means of Jacobi's elliptic function. The implication to the
dissipative process is discussed.Comment: 14 pages using PTPTeX.st
Electronic structure and thermoelectric properties of CuRh(1-x)MgxO2
Electronic structure calculations using the augmented spherical wave method
have been performed for CuRhO2. For this semiconductor crystallizing in the
delafossite structure, it is found that the valence band maximum is mainly due
to the 4d t2g orbitals of Rh^{3+}. The structural characterizations of
CuRh(1-x)MgxO2 show a broad range of Mg^{2+} substitution for Rh^{3+} in this
series, up to about 12%. Measurements of the resistivity and thermopower of the
doped systems show a Fermi liquid-like behavior for temperatures up to about
1000K, resulting in a large weakly temperature dependent power factor. The
thermopower is discussed both within the Boltzmann equation approach as based
on the electronic structure calculations and the temperature independent
correlation functions ratio approximation as based on the Kubo formalism.Comment: 9 pages, 12 figures, more information at
http://www.physik.uni-augsburg.de/~eyert
P-450; Structure, Function, and Regulation
開始ページ、終了ページ: 冊子体のページ付
First-principles study on the origin of large thermopower in hole-doped LaRhO3 and CuRhO2
Based on first-principles calculations, we study the origin of the large
thermopower in Ni-doped LaRhO3 and Mg-doped CuRhO2. We calculate the band
structure and construct the maximally localized Wannier functions from which a
tight binding Hamiltonian is obtained. The Seebeck coefficient is calculated
within the Boltzmann's equation approach using this effective Hamiltonian. For
LaRhO3, we find that the Seebeck coefficient remains nearly constant within a
large hole concentration range, which is consistent with the experimental
observation. For CuRhO2, the overall temperature dependence of the calculated
Seebeck coefficient is in excellent agreement with the experiment. The origin
of the large thermopower is discussed.Comment: 7 pages, to be published J. Phys.: Cond. Matt., Proc. QSD 200
A schematic model for QCD at finite temperature
The simplest version of a class of toy models for QCD is presented. It is a
Lipkin-type model, for the quark-antiquark sector, and, for the gluon sector,
gluon pairs with spin zero are treated as elementary bosons. The model
restricts to mesons with spin zero and to few baryonic states. The
corresponding energy spectrum is discussed. We show that ground state
correlations are essential to describe physical properties of the spectrum at
low energies. Phase transitions are described in an effective manner, by using
coherent states. The appearance of a Goldstone boson for large values of the
interaction strength is discussed, as related to a collective state. The
formalism is extended to consider finite temperatures. The partition function
is calculated, in an approximate way, showing the convenience of the use of
coherent states. The energy density, heat capacity and transitions from the
hadronic phase to the quark-gluon plasma are calculated.Comment: 33 pages, 11 figure
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