60,219 research outputs found
Determinant representations of scalar products for the open XXZ chain with non-diagonal boundary terms
With the help of the F-basis provided by the Drinfeld twist or factorizing
F-matrix for the open XXZ spin chain with non-diagonal boundary terms, we
obtain the determinant representations of the scalar products of Bethe states
of the model.Comment: Latex file, 28 pages, based on the talk given by W. -L. Yang at
Statphys 24, Cairns, Australia, 19-23 July, 201
The nonperturbative closed string tachyon vacuum to high level
We compute the action of closed bosonic string field theory at quartic order
with fields up to level ten. After level four, the value of the potential at
the minimum starts oscillating around a nonzero negative value, in contrast
with the proposition made in [5]. We try a different truncation scheme in which
the value of the potential converges faster with the level. By extrapolating
these values, we are able to give a rather precise value for the depth of the
potential.Comment: 24 pages. v2: typos corrected, clarified extrapolation in scheme B,
and added extrapolated tachyon and dilaton vev's at the end of Section
Carbon-doped ZnO: A New Class of Room Temperature Dilute Magnetic Semiconductor
We report magnetism in carbon doped ZnO. Our first-principles calculations
based on density functional theory predicted that carbon substitution for
oxygen in ZnO results in a magnetic moment of 1.78 per carbon. The
theoretical prediction was confirmed experimentally. C-doped ZnO films
deposited by pulsed laser deposition with various carbon concentrations showed
ferromagnetism with Curie temperatures higher than 400 K, and the measured
magnetic moment based on the content of carbide in the films (
per carbon) is in agreement with the theoretical prediction. The magnetism is
due to bonding coupling between Zn ions and doped C atoms. Results of
magneto-resistance and abnormal Hall effect show that the doped films are
-type semiconductors with intrinsic ferromagnetism. The carbon doped ZnO
could be a promising room temperature dilute magnetic semiconductor (DMS) and
our work demonstrates possiblity of produing DMS with non-metal doping.Comment: REVtex source with 4 figures in eps forma
Finite Size Effect on Correlation Functions of a Bose Gas in a Trap and Destruction of the Order Parameter by Phase Fluctuations
The influence of the finite sizes on the coherent properties of 3D Bose
systems is considered. As is shown, the correlation functions of a Bose gas in
a trap have essential differences from analogous correlation functions in an
infinite system. Thus, the anomalous correlation function vanishes due to the
divergency of phase fluctuations which destruct the order parameter too. The
normal correlation function decays exponentially in time for sufficiently large
time interval.Comment: 10 pages, RevTex4, some references have been added some changes in
text are mad
Patterns of entropy production in dissolving natural porous media with flowing fluid
The tendency for irreversible processes to generate entropy is the ultimate driving force for structure evolution in nature. In engineering, entropy production is often used as an indicator for loss of usable energy. In this study, we show that the analysis of entropy production patterns can provide insight into the diverse observations from experiments that investigate porous medium dissolution in imposed flow field. We first present a numerical scheme for the analysis of entropy production in dissolving porous media. Our scheme uses a greyscale digital model for chalk (an extremely fine grained rock), that was obtained using X-ray nanotomography. Greyscale models preserve structural heterogeneities with very high fidelity. We focussed on the coupling between two types of entropy production: the percolative entropy, generated by dissipating the kinetic energy of fluid flow, and the reactive entropy, originating from the consumption of chemical free energy. Their temporal patterns pinpoint three stages of microstructural evolution. We then showed that local mixing deteriorates fluid channelisation by reducing local variations of reactant concentration. We also showed that microstructural evolution can be sensitive to the initial transport heterogeneities, when the macroscopic flowrate is low. This dependence on flowrate indicates the need to resolve the structural features of a porous system when fluid residence time is long
Scrambling and Gate Effects in Realistic Quantum Dots
We evaluate the magnitude of two important mesoscopic effects using a
realistic model of typical quantum dots. ``Scrambling'' and ``gate effect'' are
defined as the change in the single-particle spectrum due to added electrons or
gate-induced shape deformation, respectively. These two effects are
investigated systematically in both the self-consistent Kohn-Sham (KS) theory
and a Fermi liquid-like Strutinsky approach. We find that the genuine
scrambling effect is small because the potential here is smooth. In the KS
theory, a key point is the implicit inclusion of residual interactions in the
spectrum; these dominate and make scrambling appear larger. Finally, the gate
effect is comparable in the two cases and, while small, is able to cause
gate-induced spin transitions.Comment: 5 pages, 3 figure
- …