During the semester we have a high energy seminar and a lunch seminar. In addition to these two seminars we participate in a joint theoretical high energy theory seminar in Newe Shalom. The joint seminar takes place on Tuesdays from 10:30 until 13:30 and includes two talks and lunch. This seminar is attended by the high energy groups of all the Israeli institutions and usually attracts a crowd of roughly twenty participants.
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Title: Emergent symmetries in 3d and compactification from 5d
Abstract: We study the phenomenon of symmetry enhancement in quantum field theories in three dimensions, where the global symmetry of a model is larger in the IR than in the UV. We focus on supersymmetric theories where the situation is more tractable,and find an organizing principle for such enhancements in the form of compactifications of 5d theories on Riemann surfaces with flux in their global symmetries. We illustrate this by considering the compactification of the so-called 5d Seiberg SCFTs on tori,and obtain 3d theories with enhanced IR symmetries given by the 5d symmetry preserved by the chosen flux.
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Title: The structure of the initial conditions of the universe
Abstract: I will review what we know about the initial conditions of the universe from observations. Then, I will explain how they arise within the framework of inflation, and describe recent progress in classifying (or “bootstrapping”) the possible correlation functions between primordial fluctuations. Finally, time permitting, I will touch upon work in progress trying to apply the bootstrap philosophy to more general cosmologies.
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Title: Holography of Chronology Protection
Abstract: After an introduction to time-machine spacetimes and simple models of them, I will discuss recent work with M. Tomasevic where we use holography to study quantum effects when closed timelike curves (CTCs) are developed. We address the question of whether it is possible to send a signal across the chronology horizon, passing into the region where CTCs are present. We find that the self-interaction of quantum fields manages to banish the passage of field excitations into the non-chronal region. Going further, we compute the gravitational backreaction of the quantum fields, and show that the null chronology horizon turns into a strong, spacelike curvature singularity. This is one of the few controlled, explicit examples where we can see quantum effects change a Cauchy horizon into a spacelike singularity.
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Title: Mastering bounds on correlators
Abstract: We discuss a new viewpoint onto the CFT landscape: bounds on values of CFT correlators. We show that such bounds can be obtained by constructing suitable ‘master functionals’. We present both numerical results for 3d CFTs as well as exact results for correlators on the line. The latter follow from crossing symmetric dispersion relations. We briefly discuss how these may be used to study the Regge and flat space limits of CFT correlators.