13,265 research outputs found
Open Cluster Characterization via Cross-Correlation with Spectral Library
We present a characterization method based on spectral cross-correlation to
obtain the physical parameters of the controversial stellar aggregate
ESO442-SC04. The data used was obtained with GMOS at Gemini-South telescope
including 17 stars in the central region of the ob ject and 6 standard-stars.
FXCOR was used in an iterative process to obtain self-consistent radial
velocities for the standard-stars and averaged radial velocities for the
science spectra. Spectral types, effective temperature, suface gravity and
metallicities parameters were determined using FXCOR to correlate cluster
spectra with ELODIE spectral library and selecting the best correlation matches
using the Tonry and Davis Ratio (TDR). Analysis of the results suggests that
the stars in ESO442-SC04 are not bound and therefore they do not constitute a
physical system.Comment: 4-page paper from IAU symposium 266. Contains 3 eps figures and IAU
document class file 'iau.cls
Experimental evidence of solitary wave interaction in Hertzian chains
We study experimentally the interaction between two solitary waves that
approach one to another in a linear chain of spheres interacting via the Hertz
potential. When these counter propagating waves collide, they cross each other
and a phase shift respect to the noninteracting waves is introduced, as a
result of the nonlinear interaction potential. This observation is well
reproduced by our numerical simulations and it is shown to be independent of
viscoelastic dissipation at the beads contact. In addition, when the collision
of equal amplitude and synchronized counter propagating waves takes place, we
observe that two secondary solitary waves emerge from the interacting region.
The amplitude of secondary solitary waves is proportional to the amplitude of
incident waves. However, secondary solitary waves are stronger when the
collision occurs at the middle contact in chains with even number of beads.
Although numerical simulations correctly predict the existence of these waves,
experiments show that their respective amplitude are significantly larger than
predicted. We attribute this discrepancy to the rolling friction at the beads
contacts during solitary wave propagation
Spanning avalanches in the three-dimensional Gaussian Random Field Ising Model with metastable dynamics: field dependence and geometrical properties
Spanning avalanches in the 3D Gaussian Random Field Ising Model (3D-GRFIM)
with metastable dynamics at T=0 have been studied. Statistical analysis of the
field values for which avalanches occur has enabled a Finite-Size Scaling (FSS)
study of the avalanche density to be performed. Furthermore, direct measurement
of the geometrical properties of the avalanches has confirmed an earlier
hypothesis that several kinds of spanning avalanches with two different fractal
dimensions coexist at the critical point. We finally compare the phase diagram
of the 3D-GRFIM with metastable dynamics with the same model in equilibrium at
T=0.Comment: 16 pages, 17 figure
Young diagrams and N-soliton solutions of the KP equation
We consider -soliton solutions of the KP equation,
(-4u_t+u_{xxx}+6uu_x)_x+3u_{yy}=0 . An -soliton solution is a solution
which has the same set of line soliton solutions in both
asymptotics and . The -soliton solutions include
all possible resonant interactions among those line solitons. We then classify
those -soliton solutions by defining a pair of -numbers with , which labels line solitons in the solution. The
classification is related to the Schubert decomposition of the Grassmann
manifolds Gr, where the solution of the KP equation is defined as a
torus orbit. Then the interaction pattern of -soliton solution can be
described by the pair of Young diagrams associated with . We also show that -soliton solutions of the KdV equation obtained by
the constraint cannot have resonant interaction.Comment: 22 pages, 5 figures, some minor corrections and added one section on
the KdV N-soliton solution
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