6,452 research outputs found
Fidelity, dynamic structure factor, and susceptibility in critical phenomena
Motivated by the growing importance of fidelity in quantum critical
phenomena, we establish a general relation between fidelity and structure
factor of the driving term in a Hamiltonian through a newly introduced concept:
fidelity susceptibility. Our discovery, as shown by some examples, facilitates
the evaluation of fidelity in terms of susceptibility using well developed
techniques such as density matrix renormalization group for the ground state,
or Monte Carlo simulations for the states in thermal equilibrium.Comment: 4 pages, 2 figures, final version accepted by PR
Experimental Studies of Low-field Landau Quantization in Two-dimensional Electron Systems in GaAs/AlGaAs Heterostructures
By applying a magnetic field perpendicular to GaAs/AlGaAs two-dimensional
electron systems, we study the low-field Landau quantization when the thermal
damping is reduced with decreasing the temperature. Magneto-oscillations
following Shubnikov-de Haas (SdH) formula are observed even when their
amplitudes are so large that the deviation to such a formula is expected. Our
experimental results show the importance of the positive magneto-resistance to
the extension of SdH formula under the damping induced by the disorder.Comment: 9 pages, 3 figure
SU(2) gluon propagator on a coarse anisotropic lattice
We calculated the SU(2) gluon propagator in Landau gauge on an anisotropic
coarse lattice with the improved action. The standard and the improved scheme
are used to fix the gauge in this work. Even on the coarse lattice the lattice
gluon propagator can be well described by a function of the continuous
momentum. The effect of the improved gauge fixing scheme is found not to be
apparent. Based on the Marenzoni's model, the mass scale and the anomalous
dimension are extracted and can be reasonably extrapolated to the continuum
limit with the values and . We also extract the
physical anisotropy from the gluon propagator due to the explicit
dependence of the gluon propagator.Comment: LaTeX, 14 pages including 4 ps figure
From insulator to quantum Hall liquid at low magnetic fields
We have performed low-temperature transport measurements on a GaAs
two-dimensional electron system at low magnetic fields. Multiple
temperature-independent points and accompanying oscillations are observed in
the longitudinal resistivity between the low-field insulator and the quantum
Hall (QH) liquid. Our results support the existence of an intermediate regime,
where the amplitudes of magneto-oscillations can be well described by
conventional Shubnikov-de Haas theory, between the low-field insulator and QH
liquid.Comment: Magneto-oscillations governed by Shubnikov-de Haas theory are
observed between the low-field insulator and quantum Hall liqui
Effects of force load, muscle fatigue and extremely low frequency magnetic stimulation on EEG signals during side arm lateral raise task
Objective: This study was to quantitatively investigate the effects of force load, muscle fatigue and extremely low frequency (ELF) magnetic stimulation on electroencephalography (EEG) signal features during side arm lateral raise task.
Approach: EEG signals were recorded by a BIOSEMI Active Two system with Pin-Type active-electrodes from 18 healthy subjects when they performed the right arm side lateral raise task (90° away from the body) with three different loads (0 kg, 1 kg and 3 kg; their order was randomized among the subjects) on the forearm. The arm maintained the loads until the subject felt exhausted. The first 10 s recording for each load was regarded as non-fatigue status and the last 10 s before the subject was exhausted as fatigue status. The subject was then given a 5 min resting between different loads. Two days later, the same experiment was performed on each subject except that ELF magnetic stimulation was applied to the subject's deltoid muscle during the 5 min resting period. EEG features from C3 and C4 electrodes including the power of alpha, beta and gamma and sample entropy were analyzed and compared between different loads, non-fatigue/fatigue status, and with/without ELF magnetic stimulation.
Main results: The key results were associated with the change of the power of alpha band. From both C3-EEG and C4-EEG, with 1 kg and 3 kg force loads, the power of alpha band was significantly smaller than that from 0 kg for both non-fatigue and fatigue periods (all p    0.05 for all the force loads except C4-EEG with ELF simulation). The power of alpha band at fatigue status was significantly increased for both C3-EEG and C4-EEG when compared with the non-fatigue status (p    0.05, except between non-fatigue and fatigue with magnetic stimulation in gamma band of C3-EEG at 1 kg, and in the SampEn at 1 kg and 3 kg force loads from C4-EEG).
Significance: Our study comprehensively quantified the effects of force, fatigue and the ELF magnetic stimulation on EEG features with difference forces, fatigue status and ELF magnetic stimulation
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