1,843 research outputs found
Growth diversity in one dimensional fluctuating interfaces
A set of one dimensional interfaces involving attachment and detachment of
-particle neighbors is studied numerically using both large scale
simulations and finite size scaling analysis. A labeling algorithm introduced
by Barma and Dhar in related spin Hamiltonians enables to characterize the
asymptotic behavior of the interface width according to the initial state of
the substrate. For equal deposition--evaporation probability rates it is found
that in most cases the initial conditions induce regimes of saturated width. In
turn, scaling exponents obtained for initially flat interfaces indicate power
law growths which depend on . In contrast, for unequal probability rates the
interface width exhibits a logarithmic growth for all regardless of the
initial state of the substrate.Comment: Thoroughly extended and corrected version. Typeset in Latex, 20
pages, 7 postscript figure
Low temperature Glauber dynamics under weak competing interactions
We consider the low but nonzero temperature regimes of the Glauber dynamics
in a chain of Ising spins with first and second neighbor interactions . For it is known that at the dynamics is
both metastable and non-coarsening, while being always ergodic and coarsening
in the limit of . Based on finite-size scaling analyses of
relaxation times, here we argue that in that latter situation the asymptotic
kinetics of small or weakly frustrated ratios is characterized
by an almost ballistic dynamic exponent and arbitrarily slow
velocities of growth. By contrast, for non-competing interactions the
coarsening length scales are estimated to be almost diffusive.Comment: 12 pages, 5 figures (composite). Brief additions and few changes. To
appear in Phys. Rev.
Non-linear spectroscopy of rubidium: An undergraduate experiment
In this paper, we describe two complementary non-linear spectroscopy methods
which both allow to achieve Doppler-free spectra of atomic gases. First,
saturated absorption spectroscopy is used to investigate the structure of the
transition in rubidium. Using a slightly
modified experimental setup, Doppler-free two-photon absorption spectroscopy is
then performed on the transition in
rubidium, leading to accurate measurements of the hyperfine structure of the
energy level. In addition, electric dipole selection rules of
the two-photon transition are investigated, first by modifying the polarization
of the excitation laser, and then by measuring two-photon absorption spectra
when a magnetic field is applied close to the rubidium vapor. All experiments
are performed with the same grating-feedback laser diode, providing an
opportunity to compare different high resolution spectroscopy methods using a
single experimental setup. Such experiments may acquaint students with quantum
mechanics selection rules, atomic spectra and Zeeman effect.Comment: 16 pages, 8 figure
No phase transition for Gaussian fields with bounded spins
Let a<b, \Omega=[a,b]^{\Z^d} and H be the (formal) Hamiltonian defined on
\Omega by
H(\eta) = \frac12 \sum_{x,y\in\Z^d} J(x-y) (\eta(x)-\eta(y))^2 where
J:\Z^d\to\R is any summable non-negative symmetric function (J(x)\ge 0 for all
x\in\Z^d, \sum_x J(x)<\infty and J(x)=J(-x)). We prove that there is a unique
Gibbs measure on \Omega associated to H. The result is a consequence of the
fact that the corresponding Gibbs sampler is attractive and has a unique
invariant measure.Comment: 7 page
Non-universal disordered Glauber dynamics
We consider the one-dimensional Glauber dynamics with coupling disorder in
terms of bilinear fermion Hamiltonians. Dynamic exponents embodied in the
spectrum gap of these latter are evaluated numerically by averaging over both
binary and Gaussian disorder realizations. In the first case, these exponents
are found to follow the non-universal values of those of plain dimerized
chains. In the second situation their values are still non-universal and
sub-diffusive below a critical variance above which, however, the relaxation
time is suggested to grow as a stretched exponential of the equilibrium
correlation length.Comment: 11 pages, 5 figures, brief addition
Spatial diffusion in a periodic optical lattice: revisiting the Sisyphus effect
We numerically study the spatial diffusion of an atomic cloud experiencing
Sisyphus cooling in a three-dimensional linlin optical lattice in a broad
range of lattice parameters. In particular, we investigate the dependence on
the size of the lattice sites which changes with the angle between the laser
beams. We show that the steady-state temperature is largely independent of the
lattice angle, but that the spatial diffusion changes significantly. It is
shown that the numerical results fulfil the Einstein relations of Brownian
motion in the jumping regime as well as in the oscillating regime. We finally
derive an effective Brownian motion model from first principles which gives
good agreement with the simulations.Comment: accepted for publication in Eur. Phys. J.
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