The notion of persistence applied to breathers in thermal equilibrium

We study the thermal equilibrium of nonlinear Klein-Gordon chains at the limit of small coupling (anticontinuum limit). We show that the persistence distribution associated to the local energy density is a useful tool to study the statistical distribution of so-called thermal breathers, mainly when the equilibrium is characterized by long-lived static excitations; in that case, the distribution of persistence intervals turns out to be a powerlaw. We demonstrate also that this generic behaviour has a counterpart in the power spectra, where the high frequencies domains nicely collapse if properly rescaled. These results are also compared to non linear Klein-Gordon chains with a soft nonlinearity, for which the thermal breathers are rather mobile entities. Finally, we discuss the possibility of a breather-induced anomalous diffusion law, and show that despite a strong slowing-down of the energy diffusion, there are numerical evidences for a normal asymptotic diffusion mechanism, but with exceptionnally small diffusion coefficients.Comment: submitted to Physica

Boron in groundwater of the Island of Cyprus

Boron can be found in high concentrations in the groundwater of the Island of Cyprus, especially in the central part of the island. Boron in high concentrations is of major concern due to its toxicity to both animals and irrigated plants. The origin of the phenomenon is not very well understood and is usually explained as remains of seawater. This work quantifies the boron content through analytical techniques and provides more information on the levels found

Discrete breathers in thermal equilibrium: distributions and energy gaps

We study a discrete two-dimensional nonlinear system that allows for discrete breather solutions. We perform a spectral analysis of the lattice dynamics at thermal equilibrium and use a cooling technique to measure the amount of breathers at thermal equilibrium. Our results confirm the existence of an energy threshold for discrete breathers. The cooling method provides with a novel computational technique of measuring and analyzing discrete breather distribution properties in thermal equilibrium.Comment: 20 pages, 14 figure