1,721,000 research outputs found
Role of saddles in topologically driven phase transition: the case of d-dimensional spherical model.
No full textSaddles of the energy landscape and folding of model proteins
No full textWe numerically investigate the Potential Energy Landscape of an off-lattice beta-sheet model protein, looking at saddles and minima probed by the system during the folding process. Go-like (with native-state-dependent force field and funnel-like landscape) and non-Go-like models are considered. In the Go-like case, on varying the temperature, we observe: i) a pronounced peak at the collapse/folding temperature T(theta) similar or equal to T(f) in the energy elevation of visited saddles from underlying minima, ii) a crossover at the same point of the saddle order. Saddles-based quantities seem then to be good candidates as indicators of the funneled shape of the landscape in protein models. Copyright (C) EPLA, 200
Light diffusion and localization in three-dimensional nonlinear disordered media
No full textBy using a three-dimensional finite-difference time-domain parallel code, the linear and nonlinear propagation of light pulses in a disordered assembly of scatterers, generated by a molecular dynamics code, is simulated. We calculate the static and dynamical light diffusion constant and the transmission in the presence of localized states. We numerically demonstrate the "modulational instability random laser": at high input peak power, energy is transferred to localized states from the input pulse, resulting in a power-dependent nonexponential time decay of the transmitted pulse
Condensation in disordered lasers: Theory, 3D+1 simulations, and experiments
No full textThe complex processes underlying the generation of a coherent emission from the multiple scattering of photons and wave localization in the presence of structural disorder are still mostly unexplored. Here we show that a single nonlinear Schrodinger equation, playing the role of the Schwalow-Townes law for standard lasers, quantitatively reproduces experimental results and three-dimensional time- domain parallel simulations of a colloidal laser system
Phase diagram and complexity of mode-locked lasers: From order to disorder
No full textWe investigate mode-locking processes in lasers displaying a variable degree of structural randomness. By a spin-glass theoretic approach, we analyze the mean-field Hamiltonian and derive a phase diagram in terms of pumping rate and degree of disorder. Paramagnetic (noisy continuous wave emission), ferromagnetic (standard passive mode locking), and spin-glass phases with an exponentially large number of configurations are identified. The results are also relevant for other physical systems displaying a random Hamiltonian, such as Bose-condensed gases and nonlinear optics. © 2009 The American Physical Society
Ultrashort pulse propagation and the Anderson localization
No full textWe investigate the dynamics of a 10 fs light pulse propagating in a random medium by the direct solution of the three-dimensional Maxwell equations. Our approach employs molecular dynamics to generate a distribution of spherical scatterers and a parallel finite-difference time-domain code for the vectorial wave propagation. We calculate the disorder-averaged energy velocity and the decay time of the transmitted pulse versus the localization length for an increasing refractive index. (C) 2009 Optical Society of Americ
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