Condensed Matter Physics Seminar: MSc Seminar

Curved membrane protein scaffolds in membrane budding and fission

Speaker: Sharon Elias Panahi, TAU

Abstract:

Biological membranes undergo persistent shaping and topological rearrangements creating highly curved structures, such as endocytic vesicles. The formation of these structures requires sufficient energy, which is provided by polymerization of the membrane scaffolding proteins. The energy of the membrane shaping is governed by the membrane tension and bending elasticity. We suggest and analyze a theoretical model predicting the shape and elastic energy of a vesicle budding from an initially flat membrane. We define the criterion for fission of the vesicle neck in terms of the membrane tension and polymerization energy of the protein scaffold.

Finite width of the sonic event horizon and enhanced Hawking radiation.

Speaker: Yaniv Vinish, TAU

Abstract:

Coherent light propagating in a bulk Kerr nonlinear de-focusing medium obeys Nonlinear Schr ̈odinger equation, which is similar to the Gross-Pitaevskii equation for Bose-Einstein condensates. An equivalent hydrodynamic approach allows one to consider propagation of light as a flow of an equivalent "luminous fluid".

An analogue event horizon can be formed when the flow velocity of this fluid equals the local sound velocity, determined by the nonlinear term in NLS.

The analog event horizon is characterized by a finite width, also determined by the non-linearity length, or by the healing length in Bose-Einstein condensates.

The various eigen-modes of fluctuations are found in the immediate vicinity of the event horizon and the scattering matrix due to the finite width horizon is calculated to within the leading order corrections in the non-linearity length.

The Hawking radiation is found to be enhanced with respect to that of a Planck black body spectrum and is characterized by the emissivity larger than one.

A procedure of paraxial quantization of the fluctuation field is discussed and its connection to the conventional quantization of the electromagnetic field is demonstrated.

Seminar Organizer: Prof. Sasha Gerber