8,429 research outputs found
Dual condensates at finite isospin chemical potential
The dual observables as order parameters for center symmetry are tested at
finite isospin chemical potential in a Polyakov-loop enhanced chiral
model of QCD with physical quark masses. As a counterpart of the dressed
Polyakov-loop, the first Fourier moment of pion condensate is introduced for
under the temporal twisted boundary conditions for quarks.
We demonstrate that this dual condensate exhibits the similar temperature
dependence as the conventional Polyakov-loop. We confirm that its rapid
increase with is driven by the evaporating of pion condensation. On the
other hand, the dressed Polyakov-loop shows abnormal thermal behavior, which
even decreases with at low temperatures due to the influence of pion
condensate. We thus argue that in QCD the critical temperature extracting from
a dual observable may have nothing to do with the quark
confinement-deconfinement transition if the quark mass is very small.Comment: 8 pages, 6 figure
Generalized rotating-wave approximation to biased qubit-oscillator systems
The generalized rotating-wave approximation with counter-rotating
interactions has been applied to a biased qubit-oscillator system. Analytical
expressions are explicitly given for all eigenvalues and eigenstates. For a
flux qubit coupled to superconducting oscillators, spectra calculated by our
approach are in excellent agreement with experiment. Calculated energy levels
for a variety of biases also agree well with those obtained via exact
diagonalization for a wide range of coupling strengths. Dynamics of the qubit
has also been examined, and results lend further support to the validity of the
analytical approximation employed here. Our approach can be readily implemented
and applied to superconducting qubit-oscillator experiments conducted currently
and in the near future with a biased qubit and for all accessible coupling
strengths
Coexistence of Localized and Extended States in Disordered Systems
It is commonly believed that Anderson localized states and extended states do
not coexist at the same energy. Here we propose a simple mechanism to achieve
the coexistence of localized and extended states in a band in a class of
disordered quasi-1D and quasi-2D systems. The systems are partially disordered
in a way that a band of extended states always exists, not affected by the
randomness, whereas the states in all other bands become localized. The
extended states can overlap with the localized states both in energy and in
space, achieving the aforementioned coexistence. We demonstrate such
coexistence in disordered multi-chain and multi-layer systems.Comment: 5 pages, 3 figure
Local diffusion theory of localized waves in open media
We report a first-principles study of static transport of localized waves in
quasi-one-dimensional open media. We found that such transport, dominated by
disorder-induced resonant transmissions, displays novel diffusive behavior. Our
analytical predictions are entirely confirmed by numerical simulations. We
showed that the prevailing self-consistent localization theory [van Tiggelen,
{\it et. al.}, Phys. Rev. Lett. \textbf{84}, 4333 (2000)] is valid only if
disorder-induced resonant transmissions are negligible. Our findings open a new
direction in the study of Anderson localization in open media.Comment: 4 pages, 2 figure
Effect of Silica Fume in Concrete on Mechanical Properties and Dynamic Behaviors under Impact Loading
The effect of silica fume (SF) in concrete on mechanical properties and dynamic behaviors was experimentally studied by split Hopkinson pressure bar (SHPB) device with pulse shaping technique. Three series of concrete with 0, 12%, and 16% SF as a cement replacement by weight were produced firstly. Then the experimental procedure for dynamic tests of concrete specimens with SF under a high loading rate was presented. Considering the mechanical performance and behaviors of the concrete mixtures, those tests were conducted under five different impact velocities. The experimental results clearly show concrete with different levels of SF is a strain-rate sensitive material. The tensile strength under impact loading of the tested specimens was generally improved with the increasing content of SF levels in concrete. Additionally, the tensile strength under impact loading of the concrete enhances with the increase of the strain rates. Finally, failure modes, dynamic tensile strength, dynamic increase factor (DIF), and critical strain are discussed and analyzed. These investigations are useful to improve the understanding of the effect of SF in concrete and guide the design of concrete structures
Effect of Silica Fume in Concrete on Mechanical Properties and Dynamic Behaviors under Impact Loading
The effect of silica fume (SF) in concrete on mechanical properties and dynamic behaviors was experimentally studied by split Hopkinson pressure bar (SHPB) device with pulse shaping technique. Three series of concrete with 0, 12%, and 16% SF as a cement replacement by weight were produced firstly. Then the experimental procedure for dynamic tests of concrete specimens with SF under a high loading rate was presented. Considering the mechanical performance and behaviors of the concrete mixtures, those tests were conducted under five different impact velocities. The experimental results clearly show concrete with different levels of SF is a strain-rate sensitive material. The tensile strength under impact loading of the tested specimens was generally improved with the increasing content of SF levels in concrete. Additionally, the tensile strength under impact loading of the concrete enhances with the increase of the strain rates. Finally, failure modes, dynamic tensile strength, dynamic increase factor (DIF), and critical strain are discussed and analyzed. These investigations are useful to improve the understanding of the effect of SF in concrete and guide the design of concrete structures
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