808 research outputs found
Interaction induced mergence of Dirac points in Non-Abelian optical lattices
We study the properties of an ultracold Fermi gas loaded in a square optical
lattice and subjected to an external and classical non-Abelian gauge field. We
calculate the energy spectrum of the system and show that the Dirac points in
the energy spectrum will remain quite stable under onsite interaction of
certain strength. Once the on-site interaction grows stronger than a critical
value, the Dirac points will no longer be stable and merge into a single hybrid
point. This mergence implies a quantum phase transition from a semimetallic
phase to a band insulator. The on-site interaction between ultracold fermions
could be conveniently controlled by Feshbach resonances in current experiments.
We proposed that this remarkable interaction induced mergence of Dirac points
may be observed in the ultracold fermi gas experiments
Quantum resonance and anti-resonance for a periodically kicked Bose-Einstein Condensate in a one dimensional Box
We investigate the quantum dynamics of a periodically kicked Bose-Einstein
Condensate confined in a one dimensional (1D) Box both numerically and
theoretically, emphasizing on the phenomena of quantum resonance and
anti-resonance. The quantum resonant behavior of BEC is different from the
single particle case but the anti-resonance condition ( and ) is not affected by the atomic interaction. For the anti-resonance case, the
nonlinearity (atom interaction) causes the transition between oscillation and
quantum beating. For the quantum resonance case, because of the coherence of
BEC, the energy increase is oscillating and the rate is dramatically affected
by the many-body interaction. We also discuss the relation between the quantum
resonant behavior and the KAM or non-KAM property of the corresponding
classical system.Comment: 7 pages, 7 figure
Parametric Study on Self-centering Precast Concrete Frames with Hysteretic Dampers
The self-centering precast concrete frame structure combines the advantages of industrialization and low earthquake damage, and its energy dissipation capacity and seismic performance have always been the focus of research. This paper proposed a kind of self-centering precast concrete frame with hysteretic dampers (SCPCHD). Its modular design makes the energy dissipation device and components easy to repair and replace. In order to obtain the optimal design, the finite element models of SCPCHD frames with different layout types of post-tensioned (PT) tendons and different shapes of hysteretic dampers are established, and the elastoplastic dynamic time-history analyses are carried out. The results show that the layout types and vertical margin of PT tendons have little effect on the displacement response of the frame structure. Compared to linear PT tendons, polygonal PT tendons can better bear the bending moment of the beam and reduce the stress of longitudinal reinforcements in the beam. The reduce effect of shortening the vertical margin on the tensile damage of beam concrete is obvious in the frame with polygonal PT tendons, but not obvious in the frame with linear PT tendons. Rational design of the prestressing force also plays a crucial role in the energy dissipation capacity of SCPCHD frames
Diagnosis and location of power cable faults based on characteristic frequencies of impedance spectroscopy
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