359 research outputs found
Possibility of Direct Measurement of the Acceleration of the Universe Using 0.1 Hz Band Laser Interferometer Gravitational Wave Antenna in Space
It may be possible to construct a laser interferometer gravitational wave
antenna in space with at in this
century. We show possible specification of this antenna which we call DECIGO.
Using this antenna we show that 1) typically () chirp
signals of coalescing binary neutron stars per year may be detected with S/N
. 2) We can directly measure the acceleration of the universe by ten
years observation of binary neutron stars. 3) The stochastic gravitational
waves of \Omega_{GW}\gsim 10^{-20} predicted by the inflation may be detected
by correlation analysis for which effects of the recent cosmic acceleration
would become highly important. Our formula for phase shift due to accelerating
motion might be also applied for binary sources of LISA.Comment: 5 pages, 1 figure, revised version, Phys.Rev.Lett in pres
Analysis of relative influence of nodes in directed networks
Many complex networks are described by directed links; in such networks, a
link represents, for example, the control of one node over the other node or
unidirectional information flows. Some centrality measures are used to
determine the relative importance of nodes specifically in directed networks.
We analyze such a centrality measure called the influence. The influence
represents the importance of nodes in various dynamics such as synchronization,
evolutionary dynamics, random walk, and social dynamics. We analytically
calculate the influence in various networks, including directed multipartite
networks and a directed version of the Watts-Strogatz small-world network. The
global properties of networks such as hierarchy and position of shortcuts,
rather than local properties of the nodes, such as the degree, are shown to be
the chief determinants of the influence of nodes in many cases. The developed
method is also applicable to the calculation of the PageRank. We also
numerically show that in a coupled oscillator system, the threshold for
entrainment by a pacemaker is low when the pacemaker is placed on influential
nodes. For a type of random network, the analytically derived threshold is
approximately equal to the inverse of the influence. We numerically show that
this relationship also holds true in a random scale-free network and a neural
network.Comment: 9 figure
Non-Gaussianity test for discriminating gravitational wave backgrounds around 0.1-1Hz
We propose a non-Gaussianity test for gravitational wave backgrounds by
combining data streams of multiple detectors. This simple method allows us to
check whether a detected background is "smooth" enough to be consistent with an
inflation-type background, or is contaminated by individually undetectable weak
burst signals. The proposed test would be quite useful for the Big Bang
Observer or DECIGO whose primary target is a background from inflation at
0.1-1Hz where gravitational wave bursts from supernovae of population III stars
might become a troublesome foreground.Comment: 5 pages, to appear in ApJ
Oberlin partial ulnar nerve transfer for restoration in obstetric brachial plexus palsy of a newborn: case report
An 8 month old male infant with Erb's birth palsy was treated with two peripheral nerve transfers. Except for rapid motor reinnervations, elbow flexion was obtained by an Oberlin's partial ulnar nerve transfer, while shoulder abduction was restored by an accessory-to-suprascapular nerve transfer. The initial contraction of the biceps muscle occurred two months after surgery. Forty months after surgery, elbow flexion reached M5 without functional loss of the ulnar nerve. This case demonstrates an excellent result of an Oberlin's nerve transfer for restoration of flexion of the elbow joint in Erb's birth palsy. However, at this time partial ulnar nerve transfer for Erb's birth palsy is an optional procedure; a larger number of cases will need to be studied for it to be widely accepted as a standard procedure for Erb's palsy at birth
Collective fluctuations in networks of noisy components
Collective dynamics result from interactions among noisy dynamical
components. Examples include heartbeats, circadian rhythms, and various pattern
formations. Because of noise in each component, collective dynamics inevitably
involve fluctuations, which may crucially affect functioning of the system.
However, the relation between the fluctuations in isolated individual
components and those in collective dynamics is unclear. Here we study a linear
dynamical system of networked components subjected to independent Gaussian
noise and analytically show that the connectivity of networks determines the
intensity of fluctuations in the collective dynamics. Remarkably, in general
directed networks including scale-free networks, the fluctuations decrease more
slowly with the system size than the standard law stated by the central limit
theorem. They even remain finite for a large system size when global
directionality of the network exists. Moreover, such nontrivial behavior
appears even in undirected networks when nonlinear dynamical systems are
considered. We demonstrate it with a coupled oscillator system.Comment: 5 figure
Update of : Newly added functions and methods in versions 2 and 3
[-] is an open-source software package of
numerically exact and stochastic calculations for a wide range of quantum
many-body systems. In this paper, we present the newly added functions and the
implemented methods in vers. 2 and 3. In ver. 2, we implement spectrum
calculations by the shifted Krylov method, and low-energy excited state
calculations by the locally optimal blocking preconditioned conjugate gradient
(LOBPCG) method. In ver. 3, we implement the full diagonalization method using
ScaLAPACK and GPGPU computing via MAGMA. We also implement a real-time
evolution method and the canonical thermal pure quantum (cTPQ) state method for
finite-temperature calculations. The Wannier90 format for specifying the
Hamiltonians is also implemented. Using the Wannier90 format, it is possible to
perform the calculations for the low-energy effective
Hamiltonians of solids obtained by the open-source software RESPACK. We also
update Standard mode \unicode{x2014}simplified input format in
\unicode{x2014} to use these functions and methods. We
explain the basics of the implemented methods and how to use them.Comment: 21 pages, 10 figures, 2 table
Kω — Open-source library for the shifted Krylov subspace method of the form (zI−H)x=b
We develop Kω, an open-source linear algebra library for the shifted Krylov subspace methods. The methods solve a set of shifted linear equations (zkI−H)x(k)=b(k=0,1,2,…) for a given matrix H and a vector b, simultaneously. The leading order of the operational cost is the same as that for a single equation. The shift invariance of the Krylov subspace is the mathematical foundation of the shifted Krylov subspace methods. Applications in materials science are presented to demonstrate the advantages of the algorithm over the standard Krylov subspace methods such as the Lanczos method. We introduce benchmark calculations of (i) an excited (optical) spectrum and (ii) intermediate eigenvalues by the contour integral on the complex plane. In combination with the quantum lattice solver HΦ, Kω can realize parallel computation of excitation spectra and intermediate eigenvalues for various quantum lattice models
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