Monday, September 16th, 2024

**Math Event:**Symplectic Geometry, Gauge Theory, and Low-Dimensional Topology Seminar: Riccardo Pedrotti - Towards a count of holomorphic sections of Lefschetz fibrations over the disc

Time: 12:30 PM - 1:55 PM

Location: Math P-131

**Title:**Towards a count of holomorphic sections of Lefschetz fibrations over the disc**Speaker:**Riccardo Pedrotti [UMass Amherst]**Abstract:**Given a positive factorisation of the identity in the mapping class group of a surface S, we can associate to it a Lefschetz fibration over S^2 with S as a regular fiber. Its total space X is a symplectic 4-manifold, so it is natural to ask what kind of invariants of X can be read off from this construction. I will report on an ongoing joint work with Tim Perutz, aimed at obtaining an explicit formula for counting holomorphic sections of a Lefschetz fibration over the disk, while keeping track of their relative homology classes. This is the first step in our program to give explicit formulas for the Donaldson-Smith invariants of a Lefschetz fibration which, thanks to a combination of results by Usher and Taubes, are equivalent to the SW invariants of X. View Details
Tuesday, September 17th, 2024

CN Yang Colloquium Series: David Gross

Time: 3:00 PM - 5:15 PM

Location: 103

**Title:**"A Half Century of Quantum Chromodynamics (QCD)"Coffee/Tea: 3:00pm, Simons Center LobbyLecture: 3:45 pm, Della Pietra Family Auditorium**Speaker:**Prof. David Gross,Â Kavli Institute for Theoretical PhysicsÂ (KITP),Â University of California, Santa Barbara, Nobel Prize in Physics 2004 Â Â**Math Event:**Geometry/Topology Seminar: Bernhard Hanke - Rigidity results for initial data sets satisfying the dominant energy condition

Time: 4:00 PM - 5:00 PM

Location: P-131

**Title:**Rigidity results for initial data sets satisfying the dominant energy condition**Speaker:**Bernhard Hanke [University of Augsburg]**Abstract:**On spacelike hypersurfaces $M$ in Lorentzian manifolds satisfying the spacetime dominant energy condition, one obtains a relation between the energy and momentum densities associated with the induced Riemannian metric $g$ and the second fundamental form $q$ on $M$. This is called the dominant energy condition for the initial data set $(M,g,q)$. For $q = 0$, it specializes to the non-negativity of the scalar curvature of $g$. I will study criteria under which compact initial data sets $(M,g,q)$ with boundary and satisfying the dominant energy condition arise as spacelike hypersurfaces in Minkowski space. Our approach is based on spinor geometry. This talk is based on joint work with Christian Baer, Simon Brendle and Aaron Chow. View Details
Wednesday, September 18th, 2024

Program: Lucas Sa

Time: 10:00 AM - 11:00 AM

Location:

**Title:**Emergent Non-Hermitian Topology in Dissipative Quantum Chaos**Speaker:**Lucas Sa
Program: Andreas Fring

Time: 11:00 AM - 12:00 PM

Location:

**Title:**Mending the Spontaneously Broken PT-Regime**Speaker:**Andreas Fring
Physics Seminar: Thomas Waddleton

Time: 2:00 PM - 3:00 PM

Location: 313

**Title:**The Fate of Topological Operators in Gravity**Abstract:**Recent years have taught us many things about global symmetries in QFTs, stemming from an understanding of them through topological operators embedded into the theory's spacetime. When coupled to gravity, in greater than three spacetime dimensions, it is well-established lore that no global symmetries can survive and must be absent in the resulting theory. It is then natural to wonder as to the fates of these topological operators when embedded into a gravitational theory. In this Â talk I will propose a new way to construct symmetry operators in a given theory and analyze their behavior in the presence of small metric fluctuations, ultimately finding an obstruction to making them topological. I will motivate the construction through three examples before giving a more general argument using physical motivations that we expect to see in any quantum theory of gravity. Finally, I will conclude with some justifications for the constructions from both bottom-up and top-down points of view, as wellÂ as some possible future directions.**Math Event:**Algebraic Geometry Seminar: Lena Ji - Rationality problems for linear spaces on pencils of quadrics

Time: 4:00 PM - 5:00 PM

Location:

**Title:**Rationality problems for linear spaces on pencils of quadrics**Speaker:**Lena Ji [UIUC]**Abstract:**Linear spaces contained in the base locus of a pencil of quadrics encode a lot of interesting geometry. For example, for pencils of even-dimensional quadrics, there is a deep relationship between these linear spaces and hyperelliptic curves, dating back to Weil. This has found numerous applications, e.g. to rational points and to moduli theory. In this talk, we study rationality questions for the Fano schemes of these linear spaces, especially over non-closed fields. Our main focus is the case of second maximal linear subspaces, and we generalize results of Hassettâ€“Tschinkel, Benoistâ€“Wittenberg, and Hassettâ€“KollÃ¡râ€“Tschinkel. This work is joint with Fumiaki Suzuki. View Details
Thursday, September 19th, 2024

**YITP Event:**YITP Seminar Speaker: Sagar Airen

Time: 3:30 PM - 4:30 PM

Location: YITP Common Room 6-125

**Abstract:**Dark portals like the gauge, higgs, and neutrino portals are well-motivated extensions of the standard model (SM). These portals may lead to interactions between dark matter and the SM. In some scenarios, the mediator predominantly decays invisibly, making it challenging to constrain them. A relatively clean environment and high luminosity at a lepton collider make them the best experiments to probe these models. The prospect of future lepton colliders, namely FCC-ee and high-energy muon colliders, has triggered a growing interest in the particle physics community. We explore the discovery potential of the two proposals for dark portal models.