Critical domain slowing down

A molecular simulation of a macroscopic biosensor is still beyond our computational means. We have therefore used only the field theory to model its dynamical behavior. We have found that the eflfect of the presence of adsorbed particles at the confining walls is to slow down the coarsening of domains in the middle of the cell. When the concentration of adsorbed particles reaches a critical value, the correlation length seems to be frozen and the system never orders into a single cell-encompassing domain, as it does in the absence of adsorbed particles. Hence, the time dependent response of the sensor encodes additional information regarding the amount (and perhaps also the distribution) of adsorbed particles. 

These results are in line with others obtained by different - but less direct-techniques applied to unilamellar systems. For instance, ultrasound propagation and attenuation were found continuous at [12] and a critical slowing down of membrane relaxation was obseiwed [13]. Pretransitional phenomena in L, pha near are correlated to structure fluctuations in the form of gel-like domains, of finite size and lifetime, and whose existence was experimentally detected by fluorescence spectroscopy [14]. 

This is the simultaneous existence, for the same given set of conditions, of two different stable stationary states. The selection of the state actually occupied at a given time is a consequence of the system past history. By appropriate variation of a parameter (or, possibly, by a sufficiently intense perturbation), the transition from one state to the other can be triggered. Since the value of the parameter for which this occurs depends on the direction of the applied variation, a classical hysteresis phenomenon occurs, which is of the same type as that observed in mechanics or magnetism. In addition, near the boundaries of the bistationary domain, the approach to the stationary state gets slower and slower the evolution is then subject to the so-called "critical slowing down". 

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