6,768 research outputs found
Low-frequency discrete breathers in long-range systems without on-site potential
We propose a new mechanism of long-range coupling to excite low-frequency
discrete breathers without the on-site potential. This mechanism is universal
in long-range systems irrespective of the spatial boundary conditions, of
topology of the inner degree of freedom, and of precise forms of the coupling
functions. The limit of large population is theoretically discussed for the
periodic boundary condition. Existence of discrete breathers is numerically
demonstrated with stability analysis.Comment: 5 pages, 4 figure
Monoidal Hom-Hopf algebras
Hom-structures (Lie algebras, algebras, coalgebras, Hopf algebras) have been
investigated in the literature recently. We study Hom-structures from the point
of view of monoidal categories; in particular, we introduce a symmetric
monoidal category such that Hom-algebras coincide with algebras in this
monoidal category, and similar properties for coalgebras, Hopf algebras and Lie
algebras.Comment: 25 pages; extended version: compared to the version that appeared in
Comm. Algebra, the Section Preliminary Results and Remarks 5.1 and 6.1 have
been adde
Microstructure and mechanical properties of hip-consolidated Rene 95 powders
The effects of heat-treatments on the microstructure of P/M Rene 95 (a nickel-based powder metal), consolidated by the hot-isostatic pressing (HIP), were examined. The microstructure of as-HIP'd specimen was characterized by highly serrated grain boundaries. Mechanical tests and microstructural observations reveal that the serrated grain boundaries improved ductility at both room and elevated temperatures by retarding crack propagation along grain boundaries
Spin 3/2 Penta-quarks in anisotropic lattice QCD
A high-precision mass measurement for the pentaquark (5Q) Theta^+ in
J^P=3/2^{\pm} channel is performed in anisotropic quenched lattice QCD using a
large number of gauge configurations as N_{conf}=1000. We employ the standard
Wilson gauge action at beta=5.75 and the O(a) improved Wilson (clover) quark
action with kappa=0.1210(0.0010)0.1240 on a 12^3 \times 96 lattice with the
renormalized anisotropy as a_s/a_t = 4. The Rarita-Schwinger formalism is
adopted for the interpolating fields. Several types of the interpolating fields
with isospin I=0 are examined such as (a) the NK^*-type, (b) the
(color-)twisted NK^*-type, (c) a diquark-type. The chiral extrapolation leads
to only massive states, i.e., m_{5Q} \simeq 2.1-2.2 GeV in J^P=3/2^- channel,
and m_{5Q} = 2.4-2.6 GeV in J^P=3/2^+ channel. The analysis with the hybrid
boundary condition(HBC) is performed to investigate whether these states are
compact 5Q resonances or not. No low-lying compact 5Q resonance states are
found below 2.1GeV.Comment: 15 pages, 6 figures, 4 table
Monolithic Ge:Ga Detector Development for SAFARI
We describe the current status and the prospect for the development of
monolithic Ge:Ga array detector for SAFARI. Our goal is to develop a 64x64
array for the 45 -- 110 um band, on the basis of existing technologies to make
3x20 monolithic arrays for the AKARI satellite. For the AKARI detector we have
achieved a responsivity of 10 A/W and a read-out noise limited NEP (noise
equivalent power) of 10^-17 W/rHz. We plan to develop the detector for SAFARI
with technical improvements; significantly reduced read-out noise with newly
developed cold read-out electronics, mitigated spectral fringes as well as
optical cross-talks with a multi-layer antireflection coat. Since most of the
elemental technologies to fabricate the detector are flight-proven, high
technical readiness levels (TRLs) should be achieved for fabricating the
detector with the above mentioned technical demonstrations. We demonstrate some
of these elemental technologies showing results of measurements for test
coatings and prototype arrays.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
Spatial Distributions of Cold and Warm Interstellar Dust in M101 Resolved with AKARI/Far-Infrared Surveyor (FIS)
The nearby face-on spiral galaxy M101 has been observed with the Far-Infrared
Surveyor (FIS) onboard AKARI. The far-infrared four-band images reveal fine
spatial structures of M101, which include global spiral patterns, giant HII
regions embedded in outer spiral arms, and a bar-like feature crossing the
center. The spectral energy distribution of the whole galaxy shows the presence
of the cold dust component (18 K) in addition to the warm dust component (55
K). The distribution of the cold dust is mostly concentrated near the center,
and exhibits smoothly distributed over the entire extent of the galaxy, whereas
the distribution of the warm dust indicates some correlation with the spiral
arms, and has spotty structures such as four distinctive bright spots in the
outer disk in addition to a bar-like feature near the center tracing the CO
intensity map. The star-formation activity of the giant HII regions that
spatially correspond to the former bright spots is found to be significantly
higher than that of the rest of the galaxy. The latter warm dust distribution
implies that there are significant star-formation activities in the entire bar
filled with molecular clouds. Unlike our Galaxy, M101 is a peculiar normal
galaxy with extraordinary active star-forming regions.Comment: 18 pages, 9 figures, accepted for publication in PASJ AKARI special
issu
Large time dynamics and aging of a polymer chain in a random potential
We study the out-of-equilibrium large time dynamics of a gaussian polymer
chain in a quenched random potential. The dynamics studied is a simple Langevin
dynamics commonly referred to as the Rouse model. The equations for the
two-time correlation and response function are derived within the gaussian
variational approximation. In order to implement this approximation faithfully,
we employ the supersymmetric representation of the Martin-Siggia-Rose dynamical
action. For a short ranged correlated random potential the equations are solved
analytically in the limit of large times using certain assumptions concerning
the asymptotic behavior. Two possible dynamical behaviors are identified
depending upon the time separation- a stationary regime and an aging regime. In
the stationary regime time translation invariance holds and so is the
fluctuation dissipation theorem. The aging regime which occurs for large time
separations of the two-time correlation functions is characterized by history
dependence and the breakdown of certain equilibrium relations. The large time
limit of the equations yields equations among the order parameters that are
similar to the equations obtained in the statics using replicas. In particular
the aging solution corresponds to the broken replica solution. But there is a
difference in one equation that leads to important consequences for the
solution. The stationary regime corresponds to the motion of the polymer inside
a local minimum of the random potential, whereas in the aging regime the
polymer hops between different minima. As a byproduct we also solve exactly the
dynamics of a chain in a random potential with quadratic correlations.Comment: 21 pages, RevTeX
Metastable tight knots in a worm-like polymer
Based on an estimate of the knot entropy of a worm-like chain we predict that
the interplay of bending energy and confinement entropy will result in a
compact metastable configuration of the knot that will diffuse, without
spreading, along the contour of the semi-flexible polymer until it reaches one
of the chain ends. Our estimate of the size of the knot as a function of its
topological invariant (ideal aspect ratio) agrees with recent experimental
results of knotted dsDNA. Further experimental tests of our ideas are proposed.Comment: 4 pages, 3 figure
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