Condensed Matter Theory
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.
Astrophysics and Cosmology
Black holes play a dual role in physics, both as astronomical objects routinely discovered nowadays in binaries and in galactic centers, and as basic elements in quantum gravity. The presence of a supermassive black hole in the center of our own galaxy is evident from the trajectories of stars around a small region known as SgA* (see movie). We study black holes such as the one hiding in SgA*, and their dense stellar environment.
Condensed Matter Experimental
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).
Atomic, Molecular and Optical Physics
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.
We have entered the fascinating era of the Large Hadron Collider. The microscopic theory describing the structure of protons and nuclei is the theory of strong interactions, known as Quantum ChromoDynamics (QCD). Even though the fundamental theory is known, it is extremely difficult to deduce results of collision processes from first principle QCD calculations. This is due to complexity of the theory involving mutual interactions between gluons, the "photons" of strong interactions.
Biological and Soft Matter Physics
We use single cell phase-contrast and fluorescence time-lapse microscopy to monitor morphological changes during the division of E. coli. To bypass the limitations of optical resolution, we process the images using pixel intensity values for edge detection. We study the dynamics of the constriction width, W, and find that its formation starts shortly after birth much earlier than can be detected by simply viewing phase-contrast images. A simple geometrical model is shown to reproduce the behavior of W(t). Moreover, the time-dependence of the cell length, L(t), consists of three linear regimes.