1,620 research outputs found
Diffusion-limited deposition with dipolar interactions: fractal dimension and multifractal structure
Computer simulations are used to generate two-dimensional diffusion-limited
deposits of dipoles. The structure of these deposits is analyzed by measuring
some global quantities: the density of the deposit and the lateral correlation
function at a given height, the mean height of the upper surface for a given
number of deposited particles and the interfacial width at a given height.
Evidences are given that the fractal dimension of the deposits remains constant
as the deposition proceeds, independently of the dipolar strength. These same
deposits are used to obtain the growth probability measure through Monte Carlo
techniques. It is found that the distribution of growth probabilities obeys
multifractal scaling, i.e. it can be analyzed in terms of its
multifractal spectrum. For low dipolar strengths, the spectrum is
similar to that of diffusion-limited aggregation. Our results suggest that for
increasing dipolar strength both the minimal local growth exponent
and the information dimension decrease, while the fractal
dimension remains the same.Comment: 10 pages, 7 figure
Diffusion-limited deposition of dipolar particles
Deposits of dipolar particles are investigated by means of extensive Monte
Carlo simulations. We found that the effect of the interactions is described by
an initial, non-universal, scaling regime characterized by orientationally
ordered deposits. In the dipolar regime, the order and geometry of the clusters
depend on the strength of the interactions and the magnetic properties are
tunable by controlling the growth conditions. At later stages, the growth is
dominated by thermal effects and the diffusion-limited universal regime
obtains, at finite temperatures. At low temperatures the crossover size
increases exponentially as T decreases and at T=0 only the dipolar regime is
observed.Comment: 5 pages, 4 figure
Energy loss mechanism for suspended micro- and nanoresonators due to the Casimir force
A so far not considered energy loss mechanism in suspended micro- and
nanoresonators due to noncontact acoustical energy loss is investigated
theoretically. The mechanism consists on the conversion of the mechanical
energy from the vibratory motion of the resonator into acoustic waves on large
nearby structures, such as the substrate, due to the coupling between the
resonator and those structures resulting from the Casimir force acting over the
separation gaps. Analytical expressions for the resulting quality factor Q for
cantilever and bridge micro- and nanoresonators in close proximity to an
underlying substrate are derived and the relevance of the mechanism is
investigated, demonstrating its importance when nanometric gaps are involved
Modeling Nonequilibrium Phase Transitions and Critical Behavior in Complex Systems
We comment on some recent, yet unpublished results concerning instabilities
in complex systems and their applications. In particular, we briefly describe
main observations during extensive computer simulations of two lattice
nonequilibrium models. One exhibits robust and efficient processes of pattern
recognition under synaptic coherent activity; the second example exhibits
interesting critical behavior and simulates nucleation and spinodal
decomposition processes in driven fluids.Comment: 6 pages, 4 figure
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