The Stanford High Energy Theory Group proposes a broad program of research at the leading edge of theoretical physics. Elementary particle physics is poised to enter a new era as the Large Hadron Collider begins operation. Dimopoulos will continue his model building efforts to understand the data coming from this machine. Toward the same end Kachru and Silverstein will continue to investigate mechanisms of supersymmetry breaking, including distinctively stringy ones. They will also explore mediation mechanisms and other aspects of model building that are natural in string theory. Cosmology and especially inflation is a central interest of the Stanford group. An important topic will be to better understand metastable vacua in string theory and more generally the structure of the string landscape. This will include ideas building on the KKLT (Kachru, Kallosh, Linde, Trivedi) construction and work of Silverstein and collaborators. Linde, Shenker and Susskind will continue to study the puzzling phenomenon of eternal inflation. These studies will include work on the measure problem and on holographic definitions. Kachru, Kallosh and Linde will continue their efforts to build stringy models of slow roll inflation and to study the phenomenological constraints on the gravitino mass and gravity wave production. Linde and Susskind will study the phenomenological consequences of a relatively small number of e-foldings of slow roll inflation. Shenker and Silverstein will continue to study resolutions of spacelike singularities like the big bang and the black hole singularity in the context of string theory. Dimopoulos will continue to explore how atom interferometer techniques can be used to construct novel gravity wave detectors and implement sharp tests of General Relativity. The basic structure of string theory has long been a focus of this group. Examples of activities in this direction include Silverstein?s further study of D-duality and Kallosh?s proposed work on attractors and black hole composites. As leaders in their fields, members of the Stanford group will continue to mentor graduate students and postdocs. They will also continue their efforts to communicate physics to the broader public. As in the past these efforts will include the design and development of courses aimed at non-physicists, giving public lectures, writing popular articles and books, and participating in the making of films and videos aimed at the general public.
Savas Dimopoulos: Physics is at a conceptual crossroad: on one side is the principle of Naturalness, which asserts that there are no unexplained coincidences. On the other is the Multiverse where there is an enormous number of Universes each with its own physical laws and coincidences result from environmental selection. Over the last few years we worked on ways to observationally test the idea of the Multiverse. One is Split supersymmetry, which is actively being searched for at the LHC. Another is the Axiverse which impacts structure formation, polarization rotation, and rotating black holes. The third is the Photiniverse which has LHC signatures. Shamit Kachru: Novel phases of matter are ubiquitous in modern condensed matter physics. We used a duality between normal quantum matter theories and gravity theories to relate such phases to a wide variety of new geometries of black holes in general relativity. The classification of such black holes, and hence of holographic phases of doped matter, is within reach. Renata Kallosh: The main outcomes of the project are proposals for the possible explanation of the better than expected behaviour of the perturbative quantum supergravity. Such explanations rely on duality symmetry and on superconformal symmetry, which may have protected maximal and half-maximal supergravities at the 3-loop level and explain their good ultraviolet behavior. Andrei Linde: A progress has been made towards a unified description of advanced developments in particles physics and cosmology related to recent experimental data obtained by Planck satellite and LHC. Steve Shenker: My collaborators and I formulated a simple, exactly soluble model of eternal inflation where spacetime was represented by a tree. In addition we discussed the effects of bubble collisions on descriptions (called duals) of eternal inflation. In other work we studied a special kind of gravity due to Vasiliev in four dimensions and found evidence for a new phase transition here. We showed that related transitions were not present in lower dimensions. Eva Silverstein: Cosmological observations, such as the search for gravitational waves from the early universe, are sensitive to certain quantum gravity effects. I found a rather generic mechanism for inflationary expansion of the universe which generates this signal, and developed an understanding of its essential features in a simple way. In addition, I took concrete steps toward a complete framework for cosmological horizons, discovered how quantum fields behave in changing conditions, and developed new tools to analyze systems with many strongly interacting particles. Leonard Susskind: At the present time the results are too new to for me to have thought about public presentation. However, as stated above, I spend a great deal of time explaining modern physics developments to the public.
