Condensed Matter Experimental
Mechanical properties on the nm scale
Yishay Manassen
Strain map from Gd islands and Local young modulus of nanoparticles.
The scanning tunneling microscope is a device capable of observing an image with atomic resolution and is capable of observing physical phenomena on the atomic scale. In this study we are interested in the nm scale mechanical properties, normally studied macroscopically, which can vary in different locations on the surface. These properties are the stress and strain tensors, the elastic constants, the surface energy and stress. These values can be measured either using a external perturbation (the STM tip) or internal perturbation (a heteroepitaxial island, chemical reaction).
High-Energy Physics
Quantum gravity & quantum black holes
Ram Brustein
Quantum black hole swallows matter and evaporates quantum mechanically
Are Einstein's equations and general relativity compatible with quantum mechanics? In spite of intense efforts over the last 40 years by some of the best physicists we still do not know the answer . I study the properties of black holes and other space-times with horizons to probe the laws of quantum gravity. Based on our recent research, our proposed answer is: Yes. The apparent incompatibilities between general relativity and quantum mechanics originate from the extreme approximation of treating spacetime as a strictly classical geometric object.
Astrophysics and Cosmology
Virial shocks
Uri Keshet
In the hierarchical paradigm of large-scale structure formation, galaxy clusters are the largest objects ever to virialize. These island universes are thought to grow by accreting mass through surrounding large scale, strong yet elusive, virial shocks. A combination of analytical, numerical, and observational techniques has recently led us to the first detections of these shocks, thus providing new routes for studying large-scale structure, tracing the cosmic-web, constraining shock physics, and probing dark matter and dark energy.
Atomic, Molecular and Optical Physics
Quantum Cheshire Cat
Daniel Rohrlich
If D1 clicks, then intermediate measurements find the Cat (photon) in |L> while its grin (polarization) is nonzero only in |R>.
Y. Aharonov, S. Popescu, D. Rohrlich and P. Skrzypczyk, "Quantum Cheshire Cats", New J. Phys. 15 (2013) 113015. We present a quantum Cheshire Cat. Weak measurements on a pre- and post-selected ensemble find the Cat in one place and its grin in another. The Cat could be a photon, with circular polarization as its quantum "grin" state. But see T. Denkmayr et al., "Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment", Nat. Comm. 5, 4492 (2014); they send neutrons through a silicon crystal interferometer, while weakly probing their locations and magnetic moments. The results suggest that the neutrons go along one beam path while magnetic moments go along the other.
Condensed Matter Theory
Non-equilibrium steady state of low-dimensional systems
Doron Cohen
It is possible to induce non-equilibrium steady state current, which required e.g. a radiation source. We have studied the non-monotonic dependence of the current on the intensity of the driving, and its statistical properties. We also have addressed questions that concern the relaxation of such current, and how it depends on percolation and localization properties of the model.
Biological and Soft Matter Physics
Dynamics of Complex Fluids and Geophysical Flows
Roiy Sayag
Experiment of polymer solution flowing radially under weak friction
The front of a fluid that displaces a less viscous fluid in shear-dominated flows is known to be stable. We show that in predominantly extensional flows on a sphere, a similar front of a strain-rate-softening fluid can become unstable and evolve fingerlike patterns comprised of rifts and tongues. The number of rifts and tongues declines with time and is selected by competition between interfacial hoop stress, geometric stretching, momentum dissipation, and spatial curvature. Our results elucidate fracture dynamics in complex fluids under extension and are applicable to a wide range of systems, including planetary-scale ice shelves as in snowball epochs and icy moons.