BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Carlos Shahbazi Alonso (University of Hamburg\, Dept. of Mathemati cs) DTSTART:20201223T150000Z DTEND:20201223T163000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/1 DESCRIPTION:Title: Parallel spinors on globally hyperbolic Lorentzian four-manifolds\nby Carlos Shahbazi Alonso (University of Hamburg\, Dept. of Mathematics ) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI wil l discuss the differential geometry and topology of globally hyperbolic fo ur-manifolds (M\,g) admitting a parallel real spinor ε. Using the theory of parabolic pairs recently introduced in\narXiv:1911.08658 \, I will firs t formulate the parallelicity condition of ε on M as a system of partial differential equations\, the parallel spinor flow equations\, for a family of polyforms on any given Cauchy surface Σ↪M. Existence of a parallel spinor on (M\,g) induces a system of constraint\npartial differential equa tions on Σ\, which we prove to be equivalent to an exterior differential system involving a cohomological condition on the shape operator of the em bedding Σ↪M. Solutions of this differential system are precisely the al lowed initial data for the evolution problem of a\nparallel spinor and def ine the notion of parallel Cauchy pair (e\,Θ)\, where e is a coframe and Θ is a symmetric two-tensor. I will characterize all parallel Cauchy pair s on simply connected Cauchy surfaces\, refining a result of Baum\, Leistn er\, and Lischewski. Furthermore\, I will classify all\ncompact three-mani folds admitting parallel Cauchy pairs\, proving that they are canonically equipped with a locally free action of R2 and are isomorphic to certain to rus bundles over S1. Moreover\, I will classify all left-invariant paralle l Cauchy pairs on simply connected Lie groups\, specifying when they are a llowed initial data for the Ricci flat equations and when the shape operat or is Codazzi. Finally\, I will give a novel geometric interpretation of a class of parallel spinor flows and solve it in several examples\, obtaini ng explicit families of four-dimensional Lorentzian manifolds carrying par allel spinors."\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics) DTSTART:20201125T150000Z DTEND:20201125T163000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/2 DESCRIPTION:Title: The duality-covariant formulation of Abelian gauge theories on Riema nnian four-manifolds\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theore tical Physics) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAb stract\nI describe the manifestly duality-covariant formulation of Abelian gauge theories on Riemannian four-manifolds. This relies on the notion of parataming of a symplectic vector bundle\, a paracomplex analogue of the classical notion of symplectic taming which appropriately encodes all gaug e couplings and theta angles (the so-called "gauge kinetic functions") of the theory when working in Euclidean signature. In this formulation\, the solutions of the theory are polarized anti-selfdual connections on a princ ipal bundle with split weakly Abelian structure group\, which give a manif estly duality-covariant description of Euclidean dyons\, including far-rea ching generalizations of ordinary dyons called\ndyonic U-folds.\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics) DTSTART:20201021T140000Z DTEND:20201021T153000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/3 DESCRIPTION:Title: The classification of principal bundles with weakly Abelian structur e group\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics ) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI bri efly describe the geometry and topological classification of principal bun dles whose structure group is a Lie group with Abelian Lie algebra. Such g roups are generally disconnected and non-Abelian\, but their connected com ponent of the identity is an Abelian Lie group. Such principal bundles app ear in certain physical theories\, such as in "Abelian" gauge theories in 4 dimensions with electro-magnetic duality.\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics) DTSTART:20201028T150000Z DTEND:20201028T163000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/4 DESCRIPTION:Title: Connections on principal bundles with weakly Abelian structure grou p\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics) as p art of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI give a br ief account of the theory of principal and adjoint connections on principa l bundles with weakly Abelian structure group and describe the universal C hern-Weil morphism of such groups. Such\nconnections model gauge potential s in certain physical gauge theories\, such as "Abelian" gauge theories wi th manifest electromagnetic duality.\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics) DTSTART:20201104T150000Z DTEND:20201104T163000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/5 DESCRIPTION:Title: The duality-covariant formulation of classical Abelian gauge theorie s\nby Calin Iuliu Lazaroiu (NIPNE\, Dept. of Theoretical Physics) as p art of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI give a br ief account of the duality-covariant formulation of classical Abelian gaug e theories of rank n defined on a Lorenzian 4-manifold (of which ordinary electromagnetism is a very special example when n=1). At the level of fiel d strengths\, such theories admit a formulation as twisted self-dual theor ies\, which is manifestly covariant with respect to electro-magnetic duali ty. Imposing the appropriate version of the Dirac integrality condition le ads to a description of such theories\nin terms of gauge potentials descri bed by connections on a principal bundle with weakly Abelian structure gro up G\, which in the case at hand is the group of affine transformations of a special symplectic torus. Namely\, G is a semidirect product of a 2n-di mensional torus group A with a\ndiscrete group \\Gamma which is a modified Siegel modular group.\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Carlos Shahbazi Alonso (Univ. of Hamburg\, Dept. of Mathematics) DTSTART:20210120T150000Z DTEND:20210120T163000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/6 DESCRIPTION:Title: Heterotic solitons on four-manifolds\nby Carlos Shahbazi Alonso (Univ. of Hamburg\, Dept. of Mathematics) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI will discuss four-dimensional Heterot ic solitons\, defined as a particular class of solutions of the equations of motion of Heterotic supergravity on a four-manifold $M$. Heterotic soli tons depend on a parameter $\\kappa$ and consist of a Riemannian metric $g $\, a metric connection with skew torsion $H$ on $TM$ and a closed one-for m $\\varphi$ on $M$. In the limit $\\kappa \\to 0$\, Heterotic solitons re duce to a class of generalized Ricci solitons and can be considered as a h igher-order curvature modification of the latter. If the torsion $H$ is id entified with the Hodge dual of $\\varphi$\, Heterotic solitons consist of either flat tori or closed Einstein-Weyl structures on manifolds of type $S^1\\times S^3$ as introduced by P. Gauduchon. More generally\, I will co nstruct several families of Heterotic solitons as suspensions of certain t hree-manifolds with prescribed constant principal Ricci curvatures\, among st which we find hyperbolic manifolds\, manifolds covered by $\\mathrm{Sl} (2\,\\mathbb{R})$ and E$(1\,1)$ or certain Sasakian three-manifolds. These solutions exhibit a topology dependence in the string slope parameter $\\ kappa$ and yield\, to the best of our knowledge\, the first examples of He terotic compactification backgrounds not locally isomorphic to supersymmet ric compactification backgrounds. Work in collaboration with Á. Murcia an d A. Moroianu.\n\nThis is a joint seminar "Geometry & Physics @ NIPNE" and "Geometry @ IMAR"\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Gaetan Borot (Humboldt University of Berlin) DTSTART:20210127T150000Z DTEND:20210127T163000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/7 DESCRIPTION:Title: Double Hurwitz numbers\, topological recursion and ELSV-type formula s\nby Gaetan Borot (Humboldt University of Berlin) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nHurwitz theory is concerne d with the enumeration of branched coverings of P^1 with given topology an d constrained ramification. It can be approached/solved in at least three ways: integrable hierarchies coming from the representation theory of the symmetric (first unveiled by Okounkov and Pandharipande)\, intersection th eory on the moduli space of curves (first seen in the Ekedahl-Lando-Shapir o-Vainshtein formula)\, and topological recursion (taking its roots in Bou chard-Marino conjecture). These three aspects have been established for ma ny different type of Hurwitz problems\, and after a brief review I will fo cus on double Hurwitz numbers where the three structures enrich each other : a joint work with Do\, Karev\, Lewanski and Moskowsky\, we start from kn own representation-theoretic formulas for double Hurwitz numbers to prove a polynomiality result and topological recursion\, which in turn implies a n ELSV-like formula involving Chiodo classes and generalising a formula of Johnson-Pandharipande-Tseng\, and proves along the way new vanishing prop erties of the Chiodo class.\n\nThis is a joint seminar "Geometry & Physics @ NIPNE" and "Geometry @ IMAR".\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Patrick Popescu-Pampu (Lille University) DTSTART:20210209T080000Z DTEND:20210209T093000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/8 DESCRIPTION:Title: The Combinatorics of Plane Curve Singularities\nby Patrick Popes cu-Pampu (Lille University) as part of Geometry and Physics @ NIPNE\, Buch arest\n\n\nAbstract\nEver since Newton introduced the first combinatorial object in the study of singularities of plane curves\, later called the "N ewton polygon"\, several trees -- i.e. connected graphs without cycles -- were introduced in order to completely encode the combinatorial structure of such a singularity. I will explain how\, starting from some Newton poly gons associated to a deeper and deeper "microscopic"\nstudy of the initial singularity\, one can construct a special simplicial bidimensional comple x -- a lotus -- in which all these trees embed. One can thus visualize the relations between all of them simultaneously\, in contrast with the previ ous situation\, in which there existed only algorithms relating two such t rees. My talk will consist of an introduction to the first chapter of "Han dbook of\nGeometry and Topology of Singularities I"\, recently written in collaboration with Evelia Garcia Barroso and Pedro Gonzalez Perez.\n\nThis is a joint seminar "Geometry & Physics @ NIPNE" and "Geometry @ IMAR".\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Adrien Boulanger (Univ. of Pisa) DTSTART:20210216T080000Z DTEND:20210216T093000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/9 DESCRIPTION:Title: A Cheeger like inequality for 1-forms\nby Adrien Boulanger (Univ . of Pisa) as part of Geometry and Physics @ NIPNE\, Bucharest\n\nAbstract : TBA\n\nThis is a joint seminar "Geometry & Physics @ NIPNE" and "Geometr y @ IMAR".\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Carlos Shahbazi Alonso (Univ. of Hamburg) DTSTART:20210324T150000Z DTEND:20210324T160000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/10 DESCRIPTION:Title: Mathematical Supergravity and its applications to differential geom etry\nby Carlos Shahbazi Alonso (Univ. of Hamburg) as part of Geometry and Physics @ NIPNE\, Bucharest\n\n\nAbstract\nI will discuss the recent developments in the mathematical theory of supergravity that lay the mathe matical foundations of the universal bosonic sector of four-dimensional un gauged supergravity and its Killing spinor equations in a differential-geo metric framework. I will provide the necessary context and background. ex plaining the results pedagogically from scratch and highlighting several o pen mathematical problems which arise in the mathematical theory of superg ravity\, as well as some of its potential mathematical applications. Work in collaboration with Vicente Cortés and Calin Lazaroiu.\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Sergiu Moroianu (IMAR\, Bucharest) DTSTART:20210316T080000Z DTEND:20210316T093000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/11 DESCRIPTION:Title: The Gauss-Bonnet formula on polyhedra\nby Sergiu Moroianu (IMAR \, Bucharest) as part of Geometry and Physics @ NIPNE\, Bucharest\n\nAbstr act: TBA\n\nThis is a joint seminar "Geometry & Physics @ NIPNE" and "Geom etry @ IMAR"\n\nMeeting ID: 932 0776 6496\nPasscode: 900082\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Calin Lazaroiu (NIPNE\, Bucharest) DTSTART:20210406T070000Z DTEND:20210406T083000Z DTSTAMP:20260422T225824Z UID:GAP-Bucharest/12 DESCRIPTION:Title: Spinor squares\, G-structures and Fierz potentials\nby Calin La zaroiu (NIPNE\, Bucharest) as part of Geometry and Physics @ NIPNE\, Bucha rest\n\n\nAbstract\nI give a brief summary of the spinor squaring approach to studying solutions of generalized Killing spinor equations and of some of its applications to the study of certain G-structures. I also discuss\ npotential functions which can be used to describe such G-structures as we ll as certain stratified versions thereof.\n\nMeeting ID: 998 2511 0103\n Passcode: 625488\n LOCATION:https://researchseminars.org/talk/GAP-Bucharest/12/ END:VEVENT END:VCALENDAR