186,543 research outputs found
Pseudogap and Mott Transition Studied by Cellular Dynamical Mean Field Theory
We study metal-insulator transitions between Mott insulators and metals. The
transition mechanism completely different from the original dynamical mean
field theory (DMFT) emerges from a cluster extension of it. A consistent
picture suggests that the quasiparticle weight remains nonzero through
metals and suddenly jumps to zero at the transition, while the gap opens
continuously in the insulators. This is in contrast with the original DMFT,
where continuously vanishes but the gap opens discontinuously. The present
results arising from electron differentiation in momentum space agree with
recent puzzling bulk-sensitive experiments on CaVO and SrVO.Comment: 5 pages, 4 figure
Study of the ionic Peierls-Hubbard model using density matrix renormalization group methods
Density matrix renormalization group methods are used to investigate the
quantum phase diagram of a one-dimensional half-filled ionic Hubbard model with
bond-charge attraction, which can be mapped from the Su-Schrieffer-Heeger-type
electron-phonon coupling at the antiadiabatic limit. A bond order wave
(dimerized) phase which separates the band insulator from the Mott insulator
always exists as long as electron-phonon coupling is present. This is
qualitatively different from that at the adiabatic limit. Our results indicate
that electron-electron interaction, ionic potential and quantum phonon
fluctuations combine in the formation of the bond-order wave phase
Vision-based hand gesture interaction using particle filter, principle component analysis and transition network
Vision-based human-computer interaction is becoming important nowadays. It offers natural interaction with computers and frees users from mechanical interaction devices, which is favourable especially for wearable computers. This paper presents a human-computer interaction system based on a conventional webcam and hand gesture recognition. This interaction system works in real time and enables users to control a computer cursor with hand motions and gestures instead of a mouse. Five hand gestures are designed on behalf of five mouse operations: moving, left click, left-double click, right click and no-action. An algorithm based on Particle Filter is used for tracking the hand position. PCA-based feature selection is used for recognizing the hand gestures. A transition network is also employed for improving the accuracy and reliability of the interaction system. This interaction system shows good performance in the recognition and interaction test
Secure Quantum Secret Sharing Based on Reusable GHZ States as Secure Carriers
We show a potential eavesdropper can eavesdrop whole secret information when
the legitimate users use secure carrier to encode and decode classical
information repeatedly in the protocol [proposed in Bagherinezhad S and
Karimipour V 2003 Phys. Rev. A \textbf{67} 044302]. Then we present a revised
quantum secret sharing protocol by using Greenberger-Horne-Zeilinger state as
secure carrier. Our protocol can resist Eve's attack
Single-particle subband structure of Quantum Cables
We proposed a model of Quantum Cable in analogy to the recently synthesized
coaxial nanocable structure [Suenaga et al. Science, 278, 653 (1997); Zhang et
al. ibid, 281, 973 (1998)], and studied its single-electron subband structure.
Our results show that the subband spectrum of Quantum Cable is different from
either double-quantum-wire (DQW) structure in two-dimensional electron gas
(2DEG) or single quantum cylinder. Besides the double degeneracy of subbands
arisen from the non-abelian mirrow reflection symmetry, interesting
quasicrossings (accidental degeneracies), anticrossings and bundlings of
Quantum Cable energy subbands are observed for some structure parameters. In
the extreme limit (barrier width tends to infinity), the normal degeneracy of
subbands different from the DQW structure is independent on the other structure
parameters.Comment: 12 pages, 9 figure
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