5,557 research outputs found
Density functional characterization of the antiferromagnetism in oxygen-deficient anatase and rutile TiO2
We present theoretical evidence for local magnetic moments on Ti3+ ions in
oxygen-deficient anatase and rutile TiO2 observed in a recent experiment [S.
Zhou, et al., Phys. Rev. B 79, 113201 (2009)]. Results of our first-principles
GGA+U calculations reveal that an oxygen vacancy converts two Ti4+ ions to two
Ti3+ ions in anatase phase, which results in a local magnetic moment of 1.0
per Ti3+. The two Ti3+ ions, however, form a stable antiferromagnetic
state, and similar antiferromagnetism is also observed in oxygen-deficient
rutile phase TiO2. The calculated results are in good agreement with the
experimentally observed antiferromagnetic-like behavior in oxygen-deficient
Ti-O systems.Comment: 16 pages, 5 figure
New predictions on the mass of the light hybrid meson from QCD sum rules
We calculate the coefficients of the dimension-8 quark and gluon condensates
in the current-current correlator of light hybrid current
. With inclusion of these
higher-power corrections and updating the input parameters, we re-analyze the
mass of the light hybrid meson from Monte-Carlo based QCD sum rules.
Considering the possible violation of factorization of higher dimensional
condensates and variation of , we obtain a conservative
mass range 1.72--2.60\,GeV, which favors as a better hybrid
candidate compared with and .Comment: 12pages, 2 figures, the version appearing in JHE
Backward Stackelberg Differential Game with Constraints: a Mixed Terminal-Perturbation and Linear-Quadratic Approach
We discuss an open-loop backward Stackelberg differential game involving
single leader and single follower. Unlike most Stackelberg game literature, the
state to be controlled is characterized by a backward stochastic differential
equation (BSDE) for which the terminal- instead initial-condition is specified
as a priori; the decisions of leader consist of a static terminal-perturbation
and a dynamic linear-quadratic control. In addition, the terminal control is
subject to (convex-closed) pointwise and (affine) expectation constraints. Both
constraints are arising from real applications such as mathematical finance.
For information pattern: the leader announces both terminal and open-loop
dynamic decisions at the initial time while takes account the best response of
follower. Then, two interrelated optimization problems are sequentially solved
by the follower (a backward linear-quadratic (BLQ) problem) and the leader (a
mixed terminal-perturbation and backward-forward LQ (BFLQ) problem). Our
open-loop Stackelberg equilibrium is represented by some coupled
backward-forward stochastic differential equations (BFSDEs) with mixed
initial-terminal conditions. Our BFSDEs also involve nonlinear projection
operator (due to pointwise constraint) combining with a Karush-Kuhn-Tucker
(KKT) system (due to expectation constraint) via Lagrange multiplier. The
global solvability of such BFSDEs is also discussed in some nontrivial cases.
Our results are applied to one financial example.Comment: 38 page
Instanton Effects in QCD Sum Rules for the Hybrid
In this paper, we study instanton contributions to the correlator of the
hybrid current . These contributions
are then included in a QCD sum-rule analysis of the isoscalar hybrid
mass. We find a mass at 1.83 GeV for the hybrid.
However, for the hybrid, we find the sum rules are unstable. We also
study non-zero width effects, which affect the mass prediction. The mixing
effects between these two states are studied and we find QCD sum rules support
the existence of a flavor singlet hybrid with mass at around 1.9 GeV. Finally,
we study the mixing effects between hybrid and glueball currents. The mixing
between the () and the glueball causes
two states, one in the region 1.4-1.8 GeV(1.4-2.2 GeV), and the other in the
range 1.8-2.2 GeV(2.2-2.6 GeV).Comment: 12 pages, revised versio
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