## Events - Weekly

Sunday,
October 23 |
---|

Monday,
October 24 |

Biophysics Seminar speaker Robert Gütig, Max Planck “Spiking neurons can discover predictive features by aggregate-label learning” Joseph Henry Room · 12:00 p.m.– 1:00 p.m.HET Seminar | Alba Grassi, ICTP in Trieste | "Topological string, spectral theory and Painlevé equations" In this talk I will review some aspects of a recently proposed duality between topological string on toric Calabi-Yau manifolds and the spectral theory of trace class operators. I will discuss the relation between this construction and Painlevé equations which can be used to prove the duality in a 4-dimensional limit. In addition I will apply these results to study Seiberg-Witten theory in the 4-dimensional self-dual omega background and show that this theory admits a dual description in terms of an ideal Fermi gas. PCTS Seminar Room · 2:30 p.m.– 3:30 p.m. |

Tuesday,
October 25 |

Pheno & Vino Seminar, David Shih, Rutgers, "Cornering Natural SUSY at the LHC" We derive the latest constraints on various simplified models of natural SUSY with light higgsinos, stops and gluinos, using a detailed and comprehensive reinterpretation of the most recent 13 TeV ATLAS and CMS searches with $\sim 15$~fb$^{-1}$ of data. We discuss the implications of these constraints for fine-tuning of the electroweak scale. A key aspect of this work is an improved calculation of the tuning measure (including two-loop effects, a proper treatment of UV vs.~IR masses, and threshold effects), which significantly relaxes the naturalness bounds on the stop and gluino masses. Despite this, natural SUSY is under pressure from the LHC. Jadwin 303 · 4:00 p.m.– 5:30 p.m.Math Physics Seminar, Eviatar Procaccia, Texas A & M, "Can one hear the shape of a random walk?" We consider a Gibbs distribution over random walk paths on the square lattice, proportional to a random weight of the path’s boundary . We show that in the zero temperature limit, the paths condensate around an asymptotic shape. This limit shape is characterized as the minimizer of the functional, mapping open connected subsets of the plane to the sum of their principle eigenvalue and perimeter (with respect to the first passage percolation norm). A prime novel feature of this limit shape is that it is not in the class of Wulff shapes. Joint work with Marek Biskup Jadwin 343 · 4:30 p.m.– 5:30 p.m. |

Wednesday,
October 26 |

Thursday,
October 27 |

Hamilton Colloquium Series: David Vanderbilt, Rutgers University; “The search for quantum anomalous Hall insulators” *Please note this colloquium starts at 4:30 p.m.* The quantum Hall effect, discovered 35 years ago, is a bizarre phenomenon in which a 2D gapped system can nevertheless carry a current. Moreover, the transverse conductivity of the system is precisely quantized in units of e^2/h. Unfortunately, this behavior requires a strong perpendicular magnetic field, and has only been observed at low temperatures. Work of Haldane in 1988 raised the possibility that similar physics could be observed in two-dimensional magnetic systems without any external magnetic field, and potentially at much higher temperatures. Such a system is known as a “quantum anomalous Hall” (QAH) or “Chern” insulator. In this talk I will introduce the essential physics of the QAH effect, provide a tutorial on its mathematical description in terms of Berry phases, and briefly describe recent successes in finding low-temperature realizations. I will then review some of our own recent work in which we propose the deposition of atoms with strong spin-orbit interactions onto the surfaces of magnetic insulators as a promising route toward the synthesis of higher-temperature QAH systems. Jadwin A10 · 4:30 p.m.– 6:00 p.m. |

Friday,
October 28 |

Gravity Group Seminar, Jonathan Blackman (CIT) TITLE Surrogate models of gravitational waveforms from numerical relativity simulations of black hole mergers ABSTRACT GW150914 was the first detection of gravitational waves from a binary black hole merger, bringing us into the era of gravitational wave astronomy. From such gravitational wave detections, we can put constraints on deviations from general relativity (GR), as well as measure the masses and spins of the black holes involved in the merger. Such measurements require knowledge of the gravitational waveforms predicted by GR for all relevant masses and spins. Numerical relativity(NR) simulations are now sufficiently robust that we can accurately simulate binary black hole mergers and obtain the waveform for all but the most extreme parameters, but they are too computationally expensive for a dense coverage of the parameter space. The effective-one-body model and phenomenological waveform models agree well with NR for the parameters of GW150914, but could be insufficiently accurate for estimating the parameters of a loud gravitational wave detection in other regions of the parameter space. NR surrogate models attempt to rapidly and accurately interpolate the waveforms from a set of NR simulations over a subset of parameter space. Using the Spectral Einstein Code (SpEC), we have built NR surrogate models for non-spinning binaries with mass ratios up to 10, and for spinning precessing binaries with a restricted spin direction on the smaller black hole. They typically perform an order of magnitude better than other waveform models when compared to NR waveforms which were not included in the surrogate training set, and can be used in gravitational wave parameter estimation. [Short talk presented by Stevie Bergman] Joseph Henry Room · 12:00 p.m.– 1:30 p.m.HET Seminar | Ellis Ye Yuan, School of Natural Sciences, IAS | “Projective Geometry of Scattering Amplitudes” I will introduce a technique in studying the analytic structure of perturbative S-matrix of QFTs. The main idea is to associate Feynman integrals to objects in a projective space: polytopes and hypersurfaces. At one loop, this reveals a universal structure for all possible Feynman integrals (in particular, including one-loop amplitudes in any QFTs), and gives rise to two simple algebraic algorithms to determine the integrals (as functions of the kinematics). I will also comment on the generalization to higher loop levels. Bloomberg Hall of Physics Library - Institute for Advanced Study · 1:45 p.m.– 2:45 p.m. |

Saturday,
October 29 |