142,839 research outputs found

### Disassortativity of random critical branching trees

Random critical branching trees (CBTs) are generated by the multiplicative
branching process, where the branching number is determined stochastically,
independent of the degree of their ancestor. Here we show analytically that
despite this stochastic independence, there exists the degree-degree
correlation (DDC) in the CBT and it is disassortative. Moreover, the skeletons
of fractal networks, the maximum spanning trees formed by the edge betweenness
centrality, behave similarly to the CBT in the DDC. This analytic solution and
observation support the argument that the fractal scaling in complex networks
originates from the disassortativity in the DDC.Comment: 3 pages, 2 figure

### The q-component static model : modeling social networks

We generalize the static model by assigning a q-component weight on each
vertex. We first choose a component $(\mu)$ among the q components at random
and a pair of vertices is linked with a color $\mu$ according to their weights
of the component $(\mu)$ as in the static model. A (1-f) fraction of the entire
edges is connected following this way. The remaining fraction f is added with
(q+1)-th color as in the static model but using the maximum weights among the q
components each individual has. This model is motivated by social networks. It
exhibits similar topological features to real social networks in that: (i) the
degree distribution has a highly skewed form, (ii) the diameter is as small as
and (iii) the assortativity coefficient r is as positive and large as those in
real social networks with r reaching a maximum around $f \approx 0.2$.Comment: 5 pages, 6 figure

### Substrate-tuning of correlated spin-orbit oxides

We have systematically investigated substrate-strain effects on the
electronic structures of two representative Sr-iridates, a correlated-insulator
Sr$_2$IrO$_4$ and a metal SrIrO$_3$. Optical conductivities obtained by the
\emph{ab initio} electronic structure calculations reveal that the tensile
strain shifts the optical peak positions to higher energy side with altered
intensities, suggesting the enhancement of the electronic correlation and
spin-orbit coupling (SOC) strength in Sr-iridates. The response of the
electronic structure upon tensile strain is found to be highly correlated with
the direction of magnetic moment, the octahedral connectivity, and the SOC
strength, which cooperatively determine the robustness of $J_{eff}$=1/2 ground
states. Optical responses are analyzed also with microscopic model calculation
and compared with corresponding experiments. In the case of SrIrO$_3$, the
evolution of the electronic structure near the Fermi level shows high
tunability of hole bands, as suggested by previous experiments

### The Commercial Stainless Steel Tube Enveloping Technique for MgB2

A commercial stainless steel tube was employed to synthesize MgB2. The
specimen was prepared by a stoichiometric mixture of Mg and B. The specimen
that had been enveloped in the commercial stainless steel tube was synthesized
for 2 hours at 1193 K. X-ray spectra showed there were no second phases like
MgO. The transition temperature of the specimen was 37.5 K with a sharp
transition width within 1K. The specimen showed a good connection between
grains and critical current density as calculated with the Bean model is more
than 100,000 A/cm2 at 20 K and in zero field.Comment: 6 pages, 5 figure

### Structural instability and the Mott-Peierls transition in a half-metallic hollandite : K$_{2}$Cr$_{8}$O$_{16}$

In order to explore the driving mechanism of the concomitant metal-insulator
and structural transitions in quasi-one-dimensional hollandite
K$_{2}$Cr$_{8}$O$_{16}$, electronic structures and phonon properties are
investigated by employing the {\it ab initio} density functional theory (DFT)
calculations. We have found that the imaginary phonon frequency reflecting the
structural instability appears only in the DFT+$U$ ($U$: Coulomb correlation)
calculation, which indicates that the Coulomb correlation plays an essential
role in the structural transition. The lattice displacements of the softened
phonon at X explain the observed lattice distortions in K$_{2}$Cr$_{8}$O$_{16}$
perfectly well, suggesting the Peierls distortion vector {\bf Q} of X (0, 0,
1/2). The combined study of electronic and phonon properties reveals that
half-metallic K$_{2}$Cr$_{8}$O$_{16}$, upon cooling, undergoes the
correlation-assisted Peierls transition to become a Mott-Peierls ferromagnetic
insulator at low temperature

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### Spin glass phase transition on scale-free networks

We study the Ising spin-glass model on scale-free networks generated by the static model using the replica method. Based on the replica-symmetric solution, we derive the phase diagram consisting of the paramagnetic (P), ferromagnetic (F), and spin glass (SG) phases as well as the Almeida-Thouless line as functions of the degree exponent , the mean degree K, and the fraction of ferromagnetic interactions r. To reflect the inhomogeneity of vertices, we modify the magnetization m and the spin-glass order parameter q with vertex- weights. The transition temperature Tc (Tg) between the P-F (P-SG) phases and the critical behaviors of the order parameters are found analytically. When 21/2, while it is in the SG phase at r=1/2. m and q decay as power-laws with increasing temperature with different -dependent exponents. When >3, the Tc and Tg are finite and related to the percolation threshold. The critical exponents associated with m and q depend on for 3<<5 (3<<4) at the P-F (P-SG) boundar

### Reality conditions for (2+1)-dimensional gravity coupled with the Dirac field

The canonical formalism of three dimensional gravity coupled with the Dirac
field is considered. We introduce complex variables to simplify the Dirac
brackets of canonical variables and examine the canonical structure of the
theory. We discuss the reality conditions which guarantee the equivalence
between the complex and real theory.Comment: 13 pages, late

### A central limit theorem for descents and major indices in fixed conjugacy classes of $S_n$

The distribution of descents in fixed conjugacy classes of $S_n$ has been
studied, and it is shown that its moments have interesting properties. Kim and
Lee showed, by using Curtiss' theorem and moment generating functions, how to
prove a central limit theorem for descents in arbitrary conjugacy classes of
$S_n$. In this paper, we prove a modified version of Curtiss' theorem to shift
the interval of convergence in a more convenient fashion and use this to show
that the joint distribution of descents and major indices is asymptotically
bivariate normal.Comment: 18 page

### Opulent Operetta and Marvelous Musicals

Program listing performers and works performe

### The nature of Itinerant Ferromagnetism of SrRuO3 : A DFT+DMFT Study

We have investigated the temperature (T)-dependent evolution of electronic
structures and magnetic properties of an itinerant ferromagnet SrRuO3,
employing the combined scheme of the density functional theory and the
dynamical mean-field theory (DFT+DMFT). The inclusion of finite dynamical
correlation effects beyond the DFT well describes not only the incoherent hump
structure observed in the photoemission experiment but also the T-dependent
magnetic properties in accordance with experiments. We have shown that the
magnetization of SrRuO3 evolves with the Stoner behavior below the Curie
temperature (Tc), reflecting the weak itinerant ferromagnetic behavior, but the
local residual magnetic moment persists even above Tc, indicating the local
magnetic moment behavior. We suggest that the ferromagnetism of SrRuO3 has dual
nature of both weak and local moment limits, even though the magnetism of
SrRuO3 is more itinerant than that of Fe.Comment: 5 pages, 4 figure

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