22,689,094 research outputs found
About J-flow, J-balanced metrics, uniform J-stability and K-stability
From the work of Dervan-Keller, there exists a quantization of the critical
equation for the J-flow. This leads to the notion of J-balanced metrics. We
prove that the existence of J-balanced metrics has a purely algebro-geometric
characterization in terms of Chow stability, complementing the result of
Dervan-Keller. We also obtain various criteria that imply uniform J-stability
and uniform K-stability. Eventually, we discuss the case of K\"ahler classes
that may not be integral over a compact manifold.Comment: 23 pages; In honor of Ngaiming Mok's 60th birthday. To appear in
Asian J. Mat
Isotropic realizability of current fields in R^3
This paper deals with the isotropic realizability of a given regular
divergence free field j in R^3 as a current field, namely to know when j can be
written as sigma Du for some isotropic conductivity sigma, and some gradient
field Du. The local isotropic realizability in R^3 is obtained by Frobenius'
theorem provided that j and curl j are orthogonal in R^3. A counter-example
shows that Frobenius' condition is not sufficient to derive the global
isotropic realizability in R^3. However, assuming that (j, curl j, j x curl j)
is an orthogonal basis of R^3, an admissible conductivity sigma is constructed
from a combination of the three dynamical flows along the directions j/|j|,
curl j/|curl j| and (j/|j|^2) x curl j. When the field j is periodic, the
isotropic realizability in the torus needs in addition a boundedness assumption
satisfied by the flow along the third direction (j/|j|^2) x \curl j. Several
examples illustrate the sharpness of the realizability conditions.Comment: 22 page
Systematic analysis of the , , , , and in meson family
In this work, we tentatively assign the charmed mesons ,
, , , and
observed by the LHCb collaboration according to their
spin-parity and masses, then study their strong decays to the ground state
charmed mesons plus light pseudoscalar mesons with the model.
According to these study, we assigned the as the
state, the as the
or state, the as the or
state in the meson family. As a byproduct, we also
study the strong decays of ,,
, etc, states, which will be helpful
to further experimentally study mixings of these mesons.Comment: 16 pages,1 figure. arXiv admin note: text overlap with
arXiv:0801.4821 by other author
Impurity Energy Level Within The Haldane Gap
An impurity bond in a periodic 1D antiferromagnetic, spin 1 chain with
exchange is considered. Using the numerical density matrix renormalization
group method, we find an impurity energy level in the Haldane gap,
corresponding to a bound state near the impurity bond. When the level
changes gradually from the edge of the Haldane gap to the ground state energy
as the deviation changes from 0 to 1. It seems that there is
no threshold. Yet, there is a threshold when . The impurity level
appears only when the deviation is greater than ,
which is near 0.3 in our calculation.Comment: Latex file,9 pages uuencoded compressed postscript including 4
figure
The spin-half Heisenberg antiferromagnet on two Archimedian lattices: From the bounce lattice to the maple-leaf lattice and beyond
We investigate the ground state of the two-dimensional Heisenberg
antiferromagnet on two Archimedean lattices, namely, the maple-leaf and bounce
lattices as well as a generalized - model interpolating between both
systems by varying from (bounce limit) to (maple-leaf
limit) and beyond. We use the coupled cluster method to high orders of
approximation and also exact diagonalization of finite-sized lattices to
discuss the ground-state magnetic long-range order based on data for the
ground-state energy, the magnetic order parameter, the spin-spin correlation
functions as well as the pitch angle between neighboring spins. Our results
indicate that the "pure" bounce () and maple-leaf () Heisenberg
antiferromagnets are magnetically ordered, however, with a sublattice
magnetization drastically reduced by frustration and quantum fluctuations. We
found that magnetic long-range order is present in a wide parameter range and that the magnetic order parameter varies only
weakly with . At a direct first-order transition to
a quantum orthogonal-dimer singlet ground state without magnetic long-range
order takes place. The orthogonal-dimer state is the exact ground state in this
large- regime, and so our model has similarities to the Shastry-Sutherland
model. Finally, we use the exact diagonalization to investigate the
magnetization curve. We a find a 1/3 magnetization plateau for and another one at 2/3 of saturation emerging only at large .Comment: 9 pages, 10 figure
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