2,428 research outputs found
A Schwinger term in q-deformed su(2) algebra
An extra term generally appears in the q-deformed algebra for the
deformation parameter , if one combines the
Biedenharn-Macfarlane construction of q-deformed , which is a
generalization of Schwinger's construction of conventional , with the
representation of the q-deformed oscillator algebra which is manifestly free of
negative norm. This extra term introduced by the requirement of positive norm
is analogous to the Schwinger term in current algebra. Implications of this
extra term on the Bloch electron problem analyzed by Wiegmann and Zabrodin are
briefly discussed.Comment: 9 pages. A couple of clarifying comments have been added. This
modified version has been published in Mod. Phys. Lett.
A class of Heisenberg models with the orthogonal dimer ground states
Extensions of the Shastry-Sutherland model are possible in various ways. In
particular, it is possible to construct a natural model in three dimensions
which has the exact dimer ground state. Recently found spin gap system
SrCu_2(BO_3)_2 has this structure. The exchange constants between the layers is
expected to be smaller than the intra-layer couplings. However, the exactness
of the dimer state for the three dimensional structure is important to
understand why magnetic properties of SrCu_2(BO_3)_2 are described well by the
two dimensional model.Comment: 3 pages, 5 figures, to appear in Journal of Physics: Condensed Matte
Magnetization Plateaus in One Dimensional Heisenberg Model with Dimerization and Quadrumerization
The one dimensional Heisenberg model with dimerization () and
quadrumerization () in the magnetic field is studied by means of the
numerical exact diagonalization of finite size systems and the conformal field
theory. It is found that the magnetization plateau at half of the saturation
value exists for . For , this model is described by
the conformal field theory with central charge at this value of
magnetization. The critical exponent which characterizes the
-dependence of the width of the plateau is calculated using the level
spectroscopy method. The -dependence of the critical exponent is found
to be non-monotonic and discontinuous at . The effective theory of the
magnetization plateau is also presented for various limiting cases.Comment: 5 pages, 9 figure
Baryons with D5 Brane Vertex and k-Quarks
We study baryons in SU(N) gauge theories, according to the gauge/string
correspondence based on IIB string theory. The D5 brane, in which
fundamental strings are dissolved as a color singlet, is introduced as the
baryon vertex, and its configurations are studied. We find point- and
split-type of vertex. In the latter case, two cusps appears and they are
connected by a flux composed of dissolved fundamental strings with a definite
tension. In both cases, fundamental quarks are attached on the cusp(s) of
the vertex to cancel the surface term. In the confining phase, we find that the
quark in the baryon feel the potential increasing linearly with the distance
from the vertex. At finite temperature and in the deconfining phase, we find a
stable k-quarks "baryons", which are constructed of arbitrary number of
quarks.Comment: 20 pages, 11 figure
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