12,775 research outputs found
Holographic model for antiferromagnetic quantum phase transition induced by magnetic field
We propose a gravity dual of antiferromagnetic quantum phase transition (QPT)
induced by magnetic field and study the critical behavior around the quantum
critical point (QCP). It turns out that the boundary critical theory is a
strong coupling theory with dynamic exponent and that the hyperscaling
law is violated and logarithmic corrections appear near the QCP. Some novel
scaling relations are predicated, which can be tested by experiment data in
future. We also make some comparison with experimental data on low-dimensional
magnets BiCoPO and pyrochlores ErYTiO.Comment: published versions in PR
Cluster dynamical mean field theory of quantum phases on a honeycomb lattice
We have studied the ground state of the half-filled Hubbard model on a
honeycomb lattice by performing the cluster dynamical mean field theory
calculations with exact diagonalization on the cluster-impurity solver. Through
using elaborate numerical analytic continuation, we identify the existence of a
`spin liquid' from the on-site interaction U=0 to (between and
) with a smooth crossover correspondingly from the charge fluctuation
dominating phase into the charge correlation dominating phase. The
semi-metallic state exits only at U=0. We further find that the magnetic phase
transition at from the `spin liquid' to the N\'{e}el antiferromagnetic
Mott insulating phase is a first-order quantum phase transition. We also show
that the charge fluctuation plays a substantial role on keeping the `spin
liquid' phase against the emergence of a magnetic order.Comment: 5 pages and 8 figure
Electromechanical Simulation of Actively Controlled Rotordynamic Systems with Piezoelectric Actuators
Theories and tests for incorporating piezoelectric pushers as actuator devices for active vibration control are discussed. It started from a simple model with the assumption of ideal pusher characteristics and progressed to electromechanical models with nonideal pushers. Effects on system stability due to the nonideal characteristics of piezoelectric pushers and other elements in the control loop were investigated
Statistical Geometry of Packing Defects of Lattice Chain Polymer from Enumeration and Sequential Monte Carlo Method
Voids exist in proteins as packing defects and are often associated with
protein functions. We study the statistical geometry of voids in
two-dimensional lattice chain polymers. We define voids as topological features
and develop a simple algorithm for their detection. For short chains, void
geometry is examined by enumerating all conformations. For long chains, the
space of void geometry is explored using sequential Monte Carlo importance
sampling and resampling techniques. We characterize the relationship of
geometric properties of voids with chain length, including probability of void
formation, expected number of voids, void size, and wall size of voids. We
formalize the concept of packing density for lattice polymers, and further
study the relationship between packing density and compactness, two parameters
frequently used to describe protein packing. We find that both fully extended
and maximally compact polymers have the highest packing density, but polymers
with intermediate compactness have low packing density. To study the
conformational entropic effects of void formation, we characterize the
conformation reduction factor of void formation and found that there are strong
end-effect. Voids are more likely to form at the chain end. The critical
exponent of end-effect is twice as large as that of self-contacting loop
formation when existence of voids is not required. We also briefly discuss the
sequential Monte Carlo sampling and resampling techniques used in this study.Comment: 29 pages, including 12 figure
ENVIRONMENTAL LABELING OF ELECTRICITY: EFFECTS ON CONSUMER UNCERTAINTY ABOUT PRODUCT ATTRIBUTES AND LIKELIHOOD TO BUY DECISIONS
Using data collected by the U.S. Department of Energy we test how price and environmental marketing and labeling affects respondents' uncertainty about product attributes and about their purchase intentions.Consumer/Household Economics,
Optimal Beamforming for Non-Regenerative MIMO Relays with Direct Link
Abstract—In this letter, we generalize the existing works on the design of the optimal relay amplifying matrix for nonregenerative multiple-input multiple-output (MIMO) relay communication systems by including the direct source-destination link. We show that for most commonly used objective functions, the optimal relay amplifying matrix has a general beamforming structure, that is, the relay first sets beams to the direction of the source-relay channel, then conducts a linear precoding, and finally beamforms towards the direction of the relay-destination channel. Index Terms—MIMO relay, linear non-regenerative relay, direct link. I
Evolving small-world networks with geographical attachment preference
We introduce a minimal extended evolving model for small-world networks which
is controlled by a parameter. In this model the network growth is determined by
the attachment of new nodes to already existing nodes that are geographically
close. We analyze several topological properties for our model both
analytically and by numerical simulations. The resulting network shows some
important characteristics of real-life networks such as the small-world effect
and a high clustering.Comment: 11 pages, 4 figure
- …