91,345 research outputs found
Long-range frustration in T=0 first-step replica-symmetry-broken solutions of finite-connectivity spin glasses
In a finite-connectivity spin-glass at the zero-temperature limit, long-range
correlations exist among the unfrozen vertices (whose spin values being
non-fixed). Such long-range frustrations are partially removed through the
first-step replica-symmetry-broken (1RSB) cavity theory, but residual
long-range frustrations may still persist in this mean-field solution. By way
of population dynamics, here we perform a perturbation-percolation analysis to
calculate the magnitude of long-range frustrations in the 1RSB solution of a
given spin-glass system. We study two well-studied model systems, the minimal
vertex-cover problem and the maximal 2-satisfiability problem. This work points
to a possible way of improving the zero-temperature 1RSB mean-field theory of
spin-glasses.Comment: 5 pages, two figures. To be published in JSTA
Comment on ``Scientific collaboration networks. II. Shortest paths, weighted networks, and centrality"
In this comment, we investigate a common used algorithm proposed by Newman
[M. E. J. Newman, Phys. Rev. E {\bf 64}, 016132(2001)] to calculate the
betweenness centrality for all vertices. The inaccurateness of Newman's
algorithm is pointed out and a corrected algorithm, also with O() time
complexity, is given. In addition, the comparison of calculating results for
these two algorithm aiming the protein interaction network of Yeast is shown.Comment: 3 pages, 2 tables, and 2 figure
Information-Theoretic Measure of Genuine Multi-Qubit Entanglement
We consider pure quantum states of N qubits and study the genuine N-qubit
entanglement that is shared among all the N qubits. We introduce an
information-theoretic measure of genuine N-qubit entanglement based on
bipartite partitions. When N is an even number, this measure is presented in a
simple formula, which depends only on the purities of the partially reduced
density matrices. It can be easily computed theoretically and measured
experimentally. When N is an odd number, the measure can also be obtained in
principle.Comment: 5 pages, 2 figure
Spin-Hall and Anisotropic Magnetoresistance in Ferrimagnetic Co-Gd / Pt layers
We present the Co-Gd composition dependence of the spin-Hall
magnetoresistance (SMR) and anisotropic magnetoresistance (AMR) for
ferrimagnetic Co100-xGdx / Pt bilayers. With Gd concentration x, its magnetic
moment increasingly competes with the Co moment in the net magnetization. We
find a nearly compensated ferrimagnetic state at x = 24. The AMR changes sign
from positive to negative with increasing x, vanishing near the magnetization
compensation. On the other hand, the SMR does not vary significantly even where
the AMR vanishes. These experimental results indicate that very different
scattering mechanisms are responsible for AMR and SMR. We discuss a possible
origin for the alloy composition dependence.Comment: 31 Pages, 9 figure
Modeling of Transitional Channel Flow Using Balanced Proper Orthogonal Decomposition
We study reduced-order models of three-dimensional perturbations in
linearized channel flow using balanced proper orthogonal decomposition (BPOD).
The models are obtained from three-dimensional simulations in physical space as
opposed to the traditional single-wavenumber approach, and are therefore better
able to capture the effects of localized disturbances or localized actuators.
In order to assess the performance of the models, we consider the impulse
response and frequency response, and variation of the Reynolds number as a
model parameter. We show that the BPOD procedure yields models that capture the
transient growth well at a low order, whereas standard POD does not capture the
growth unless a considerably larger number of modes is included, and even then
can be inaccurate. In the case of a localized actuator, we show that POD modes
which are not energetically significant can be very important for capturing the
energy growth. In addition, a comparison of the subspaces resulting from the
two methods suggests that the use of a non-orthogonal projection with adjoint
modes is most likely the main reason for the superior performance of BPOD. We
also demonstrate that for single-wavenumber perturbations, low-order BPOD
models reproduce the dominant eigenvalues of the full system better than POD
models of the same order. These features indicate that the simple, yet accurate
BPOD models are a good candidate for developing model-based controllers for
channel flow.Comment: 35 pages, 20 figure
Field theoretic calculation of scalar turbulence
The cascade rate of passive scalar and Bachelor's constant in scalar
turbulence are calculated using the flux formula. This calculation is done to
first order in perturbation series. Batchelor's constant in three dimension is
found to be approximately 1.25. In higher dimension, the constant increases as
.Comment: RevTex4, publ. in Int. J. Mod. Phy. B, v.15, p.3419, 200
Fermionic R-operator approach for the small-polaron model with open boundary condition
Exact integrability and algebraic Bethe ansatz of the small-polaron model
with the open boundary condition are discussed in the framework of the quantum
inverse scattering method (QISM). We employ a new approach where the fermionic
R-operator which consists of fermion operators is a key object. It satisfies
the Yang-Baxter equation and the reflection equation with its corresponding
K-operator. Two kinds of 'super-transposition' for the fermion operators are
defined and the dual reflection equation is obtained. These equations prove the
integrability and the Bethe ansatz equation which agrees with the one obtained
from the graded Yang-Baxter equation and the graded reflection equations.Comment: 10 page
- …