The Racah Institute of Physics

In a series of groundbreaking papers, Racah developed the mathematical methods, which are now textbook methods, for the calculation of the spectra of complex atoms. This work was carried out in Jerusalem in complete scientific isolation during the years of World War II. In this work he pioneered the use of symmetries and group theory for these calculations. Theoretical atomic spectroscopy was also the subject of most of his students and visitors. However, some of his best students started to apply his elaborate methods to the young science of nuclear spectroscopy. In Jerusalem, Nissan Zeldes, who became the world expert in the theory of nuclear masses, and Gideon Rakavy. Two of Racah's students, Amos de-Shalit and Igal Talmi, became the world leaders in theoretical nuclear spectroscopy. They founded the nuclear physics department at the Weizmann Institute in Rehovoth. As mentioned, experimental physics was carried out from the late 1920s, first by Sambursky in atomic spectroscopy then by Alexander and Wolfson in X-ray spectroscopy, crystallography and optics. In 1950 William Low (Ze'ev Lev), who was a student of Charles Townes in the United States, joined the experimental physics. He started new fields of research in Jerusalem. Starting to work on microwaves, he then set up a laboratory for magnetic resonance research. He also pioneered cryogenics and laser physics in Jerusalem. Nuclear magnetic resonance followed, including its medical application. Abraham Halperin and Abraham Many, two of Racah's early graduates, started new research directions in the physics of the solid state. They did experimental research on the optical and electrical properties of insulators and semiconductors, as well as the surface properties of solids. These fields of research were just starting to thrive along with the birth of the transistor. An important addition to the experimental group was Solly G. Cohen from England. He joined the physics in 1949 and became its first nuclear experimentalist measuring very long lived radionuclides as well as extremely short lived nuclear states. In the early sixties his interests shifted to the newly discovered Mossbauer effect, and established a research group which turned Jerusalem into a world center in this field.

Many graduates of the Racah Institute (and the physics departments which preceded it) became leading professors and scientists (including a Nobel Laureate) in Israel and all over the world. During its existence the Institute enjoyed visits of many important physicists from all over the world. Niels Bohr, Paul Dirac, Wolfgang Pauli, Robert Oppenheimer, John Wheeler and Stephen Hawking, to mention just a few. All Wolf Prize winners and a great number of Nobel Laureates were amongst the visitors.[5]

Current research at the Racah Institute covers the fields of astrophysics, high energy physics, nuclear physics, condensed matter physics, statistical physics, nonlinear physics, biophysics, quantum optics, quantum information and computational neuroscience.

Condensed Matter Physics at the Racah Institute contains both a strong theoretical and an experimental effort. Most investigations are performed within the expansive field of many-body physics, with particular emphasis on nonequilibrium phenomena, the effects of decoherence and dissipation, the study of low-dimensional systems, and glassy systems, to name but a few subjects. Another direction of research includes statistical physics applied, for example, to reaction diffusion systems, especially in cases where fluctuations have an important effect.

Within the realm of theory, the methods being employed range from various field theoretic methods, both exact and perturbative, to numerical methods and exact methods based on the theory of both classical and quantum integrability. These concepts and methods are applied to a variety of physical systems, such as quantum impurity problems (realized, e.g., in quantum dots), the fractional quantum Hall effect, one-dimensional fermionic gases, Anderson transitions, and superconductivity, including special aspects related to high-Tc superconductivity.

On the experimental side, benefiting from the facilities of the Harvey M. Krueger center for nanoscience and nanotechnology, researchers apply modern measuring and fabrication techniques to study the physics of nano-structures, their application to quantum information processing, the interaction of light and matter, high-Tc superconductivity, and the physics of electron glasses. More specifically, and summarizing but a few of the research directions, researchers study excitonic fluids in semiconductor nanostructures with an eye on both a better physical understanding of their macroscopic quantum coherence properties and possible future applications in electro-optic devices. Josephson junctions are being studied in order to expose and optimize the conditions that allow for long-lived macroscopic quantum coherence, and to clarify the processes that lead to noise and decoherence. Electron glasses are being studied in order to understand the underlying mechanisms that lead to their peculiar properties, specifically the interplay of interactions, disorder and nonequilibrium, as well as how these are manifested in transport properties.

High Energy Physics (HEP) research includes both HEP theory and particle phenomenology.

One of the current activities of the High Energy Physics group at the Racah Institute of Physics involves the fundamental laws of nature, touching upon both Quantum Field Theory and General relativity (Einstein's gravity) together with the geometry and mathematics which underlie them. Evaluation of Feynman diagrams lies at the computational core of Quantum Field Theory, yet despite considerable progress over more than 70 years a general and full theory is not available. Research in the group addresses this issue. This research line grew out of an approach to solving the two-body problem in Einstein's gravity in the post-Newtonian limit through a (classical) effective field theory, a problem which is essential for detection of interpretation of gravitational waves. In this approach Feynman diagrams are used to compute the two-body effective action.

A second research area is focused on physics beyond the Standard Model of the electro-weak and the strong interactions. Examples include models of Supersymmetry-breaking and its mediation to Supersymmetric extensions of the Standard Model, with an emphasize on models whose properties may allow a relatively early discovery at the Large Hadron Collider at CERN, models of extra dimensions and their potential signatures at the LHC and future colliders, as well as their embedding in string theory, the dynamics of Supersymmetric theories and Supersymmetry-breaking, the interplay between gauge theory and its embedding on brane constructions in string theory, the physics of black holes and the early universe in string theory, and its interplay with brane dynamics and gauge theory, e.g. via the Anti-de-Sitter/Conformal-Field-Theory correspondence, as well as various aspects of the underlying structure of string theory.

A third research area addresses quantum entanglement in Quantum Field Theory.

The Nonlinear and Statistical Physics group pursues extensive theoretical and experimental studies, trying to understand the behavior of complex non-equilibrium systems. The subjects are diverse and span from plasma, laser and atomic physics to physics of materials and biophysics. Specific research areas include the fundamental physics of fracture and frictional motion, elasticity of growing objects, theory of large fluctuations in systems far from equilibrium, theory and applications of autoresonance, nonequilibrium statistical physics of ultrashort laser pulse formation, and semiclassical wave packet theory of cavity/circuit quantum electrodynamics and cold atom physics.

Quantum Information is researched both experimentally and theoretically at the Racah institute. The experimental implementations include atomic, photonic, semiconductor and superconducting realizations. Entanglement and the production of single photons is actively pursued. On the theoretical side, fundamental questions of entanglement and its characterization are investigated. Another topic of research is the theory of dynamical control of ion traps and Nitrogen vacancies in Diamond.