Aula Conversi, Dipartimento di Fisica (I piano edificio Marconi)
Complexity models in biophysics and material science
I will review three topics of my recent activity:
- Fractional Langevin Equation and its application to linear stochastic models.
The Generalized Elastic Model accounts for the dynamics of several physical systems, such as polymers, fluctuating interfaces, growing surfaces, membranes, proteins and file systems. The fractional Langevin equation rules the motion of a probe particle (tracer) in such kind of systems. Spatial correlations appearing in the Generalized Elastic Model are translated into time correlations described by the fractional derivative together with the space-time correlations of the fractional Gaussian noise. I discuss dependence on initial conditions and linear-response relations in the case of an applied potential.
- DNA tug-of-war (TOW) at micro-nanofluidic interfaces.
By establishing an entropy-driven single molecule tug-of-war at two micro−nanofluidic interfaces bridged by a nanoslit, it is possible to study the scaling relations that govern both the TOW regime and confinement-induced recoiling at various slit lengths and heights.
The recoiling force is shown to be constant for a given degree of confinement, and to scale as the inverse of the slit depth.
- Thermally activated theory of cracks in materials failure.
The idea that the solid failure can be described by means of the Kramer theory, where the intrinsic energy barrier is reduced proportionally to the applied field, dates back to ’40s. Starting from recent theories developed for single-molecule pulling, I generalize the extreme value theory to account for failures of materials with an explicit dependence on temperature and loading rate. Several experimental data and numerical outcomes will be analyzed within this framework.