## Events - Weekly

Sunday,
April 23 |
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Monday,
April 24 |

HET Seminar | Onkar Parrikar, University of Pennsylvania | "Entanglement Entropy and the Colored Jones Polynomial” We will study the entanglement structure of states in Chern-Simons (CS) theory obtained by performing the Euclidean path-integral on certain highly non-trivial 3-manifolds, namely link complements in S^3. This will allow us to assign an entanglement entropy to any bi-partition of an n-component link into sub-links; these entropies in fact provide framing independent link-invariants. In U(1) CS theory, we will give a general formula for the entanglement entropy across a bi-partition of a generic n-link into sub-links. In the non-Abelian SU(2) theory, we study various interesting 2 & 3-links including the Whitehead link and Borromean rings, both of which have non-trivial entanglement structures. If time permits, we will consider SL(2,C) and mention connections with gravity and hyperbolic geometry. PCTS Seminar Room · 2:45 p.m.– 3:45 p.m. |

Tuesday,
April 25 |

Wednesday,
April 26 |

Special Condensed Matter Seminar, G. Baskaran, Perimeter, "Bismuth - an Element of Surprise !" Elemental semi metals, Bi, As, Sb, alpha-Sn and Graphehe which straddle an insulator and a metal are fascinating. Bismuth, a member in this group has been investigated for more than a century, resulting in discovery of some well known effects in solid state physics. New phenomena have appeared in recent times. One such surprise is discovery of superconductivity at 0.5 mK. Focussing on a quasi one dimensional organization of half filled bands in this system, I will present a rich hidden physics including a crashed high Tc superconductivity and a normal state containing superconducting phase fluctuations. PCTS Seminar Room · 1:30 p.m.– 2:30 p.m. |

Thursday,
April 27 |

Hamilton Colloquium Series - James Olsen, Princeton University, "LHC at 13 TeV" In 2015 the Large Hadron Collider (LHC) resumed proton collisions at a new record energy of 13 trillion electronvolts (13 TeV) and doubled the interaction rate achieved in the 2010-2012 run. With the discovery of the Higgs boson in Run 1, the search for new particles and interactions beyond those described by the standard model has intensified in Run 2, during which the amount of data collected has already eclipsed the previous datasets at 7 and 8 TeV. I will describe the challenges presented by the new running conditions, how those challenges were met by the CMS experiment, and selected results from the 13 TeV data. Near-term and long-term goals will also be discussed, including detector upgrades targeting the High-Luminosity LHC era set to begin in the middle of the next decade. Jadwin A10 · 4:00 p.m.– 5:00 p.m. |

Friday,
April 28 |

Gravity Group Seminar, Chiara Mingarelli (Max Planck) TITLE Insights into Supermassive Black Hole Mergers, Stalling and Demographics with Pulsar Timing Arrays ABSTRACT Galaxy mergers are a standard aspect of galaxy formation and evolution, and likely all large galaxies contain central supermassive black holes (SMBH). Here I discuss a new bottom-up approach to identifying continuous nanohertz gravitational wave (GW) host galaxies by using massive elliptical galaxies in the 2 Micron All Sky Survey, assessing the likelihood of detecting one of these sources with Pulsar Timing Arrays (PTAs), their contribution to the GW background and its anisotropy, and report on the characteristics of the most detected SMBH binaries and host galaxies. We find that out to 225 Mpc there are on average 91 sources emitting GWs in the PTA band and 7 stalled binaries. The chance of detecting these GW sources with current PTA data is <1%, however in the next 10 years PTAs probe a region of the parameter space rich in sources, making a 3-sigma (or better) detection likely, depending on the source position of the sky and the ability to subtract the GW background. Joseph Henry Room · 12:00 p.m.– 1:00 p.m.HET Seminar | Wolfger Peelaers, Rutgers University | "4d/2d correspondences, localization and surface operators" Four-dimensional N=2 supersymmetric and superconformal quantum field theories take part in various 4d/2d correspondences, which map computations of certain protected data of the four-dimensional theory to problems in two-dimensional models. In this talk, I will explore the role of surface operators in two such correspondences, namely the AGT correspondence and the relation to chiral algebras. In the former, I will argue that a configuration of intersecting “M2-brane surface operators” in the four-dimensional theory translates in the insertion of a generic degenerate vertex operator, labeled by two arbitrary representations, in the Liouville/Toda correlator. In the correspondence with chiral algebras, considering the concrete example of free hypermultiplets, I will leverage a novel localization computation to identify the insertion of a class of surface operators orthogonal to the chiral algebra plane with the insertion of specific vertex operators in the chiral algebra. PCTS Seminar Room · 1:45 p.m.– 2:45 p.m. |

Saturday,
April 29 |