Topics of current interest

Statistical mechanics and quantum fields on fractals

Statistical mechanics and quantum fields on fractals – imageFractals define a new realm to study basic phenomena in quantum field theory and statistical mechanics.  This results from speci-[read more="Read more… »" less="Read less «"]

fic properties of fractals, e.g., their discrete scale invariance and the existence of distinct fractal dimensions each char­acterizing physical properties of fractals. We study different problems such as the conditions for Bose-Einstein condensation, superfluidity, phase transitions, thermo­dynamics of quantum radiation emitted by a fractal blackbody and quantum Einstein gravity.

Group: Dor Gitelman, Evgeni Gurevich

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Topology of tilings

Topology of tilings – imageThe notion of tilings recover structures also known as quasicrystals, quasiperiodic and dynamical systems, symbolic dynamics, au­tomatic  sequences  among  others.  On perio-[read more="Read more… »" less="Read less «"]

dic structures, the Bloch theorem relates structural (Bragg structure) and spectral (band structure) aspects. Not on quasicrystals. On periodic structures, topo­­­logical invariants exist and are obtained from a Berry curvature. On quasi-periodic tilings, these tools are not available. We have been able to identify topological features, to calculate and to measure them.

Group: Eli Levi, Evgeni Gurevich, Dor Gitelman, Yaroslav Don

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Quantum phase transitions – Anomalies

Quantum phase transitions – Anomalies – imageScale invariance is a property of our everyday environment. Its breaking gives rise to less common but beautiful structures like fractals. [read more="Read more… »" less="Read less «"]

At the quantum level, breaking of continuous scale invariance is a remarkable example of quantum phase transition also known as scale anomaly. We study the general features of this transition. In collaboration with exper­imentalists, we have shown evidence of this transition in Graphene. We also study other anomalies and critical properties of QED in (2+1) dimensions.

Group: Omrie Ovdat, Amit Goft

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Statistical mechanics of out of equilibrium systems

Statistical mechanics of out of equilibrium systems – imageThe best understood systems in statistical mechanics are those at equilibrium (fixed energy) or in thermal contact with a thermostat.  These  systems  are  well  descri- [read more="Read more… »" less="Read less «"]

bed by the Gibbs-Boltzmann probability to observe microscopic configurations. This breaks down far from equilibrium either in transient or stationary regimes.  Recent approaches have improved near equilibrium linear app­rox­i­mations (e.g., exact models, macroscopic fluctuation theory). We extend these classical approaches and apply them to wave and quantum non equilibrium systems.

Group: Ohad Shpielberg, Yaroslav Don, Ariane Soret, Boris Timchenko

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Quantum mesoscopic physics

Quantum mesoscopic physics – imageQuantum coherent effects are usually washed up at a macroscopic scale. De­co­her­ence originates from disorder, temperature, external couplings, etc.  But  carefully  prepa- [read more="Read more… »" less="Read less «"]

red systems display remaining quantum coherent effects. Quantum meso­scopic physics proposes a general formalism, which allows to understand among others the Aharonov-Bohm effect, weak and strong localization, and coherent backscattering. We work on new quantum interference effects, e.g., Ramsey interference and Casimir forces in mesoscopic systems. 

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Cooperative effects and superradiance

Cooperative effects and superradiance – imageSpontaneous emission of an atom coupled to quantum vacuum fluctuations is well un­derstood.    When two or more atoms are bro- [read more="Read more… »" less="Read less «"]

ught together, they may cooperate in order to coherently enhance and modify their spontaneous emission. This paradigm is often known as super (or sub) radiance. In the presence of disorder (e.g., Anderson localization) these cooperative coherent effects are qualitatively modified and may even lead to a new type of phase transition (not Anderson localization), which we have proposed and actively study. 

Group: Ari Gero

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