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Forces of the Quantum Vacuum
Ulf Leonhardt (Weizmann Institute of Science, Israel)

ABC Physics (Atomic/Bio/Condensed Matter) Seminar

Date: Thursday, April 13, 2017 12:30 PM
Location: PAA C-520

The lecture discusses forces of the quantum vacuum, which may sound like an arcane subject, but it is not - such forces are acting all around us and play a major role in daily live and modern technology, but most people are simply not aware of them. These forces are known as generalisations of van-der-Waals/Casimir forces and their physics is enjoying a renaissance, both in theory and experiment. 

According to quantum physics, the vacuum is not simply a desert of emptiness and nothing, but a sea of possibilities. The fluctuations of the quantum vacuum play a similar role credit plays in economy: they make things possible by borrowing. For example, the quantum vacuum may lend a dipole moment to an atom (a deformation of its electric charge distribution) and then this atom interacts with other atoms around it, attracting them. The dipole moment disappears, the credit from the quantum vacuum is paid back, but the attraction remains. This attraction between neutral atoms and molecules is responsible for most of the stickiness in Nature, and it becomes an issue for nano-machinery where it causes friction. 

However, the theory of the quantum vacuum appears to suffer from a major problem: formally, the sum over all the vacuum energies is infinite. Regularisation is required to extract the finite contribution that can do physical work. The known methods of regularisation work for piece-wise homogenous materials that give the force between bodies, but fail for inhomogenous materials, for calculating the force inside bodies. Recently we have developed a regularisation method that is proven to work for planar inhomogeneous materials. The method is based on visual, intuitive ideas the seminar will explain. ​​