BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Aftab Patel ((University of Western Ontario) DTSTART:20200908T130000Z DTEND:20200908T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/1 DESCRIPTION:Title: Equisingular Algebraic Approximation of Real and Complex Analytic Germs\nby Aftab Patel ((University of Western Ontario) as pa rt of Seminario de Singularidades UFC\n\n\nAbstract\nIn this talk we consi der the problem of the approximation of a real or complex analytic set ger m by germs of Nash or even algebraic sets which are equisingular with resp ect to the Hilbert-Samuel function. We show that a Cohen-Macaulay analytic singularity can be arbitrarily closely approximated by germs of Nash sets which are also Cohen-Macaulay and share the same Hilbert-Samuel function. Also\, we obtain a result that states that every analytic singularity is topologically equivalent to a Nash singularity with the same Hilbert-Samue l function. A key ingredient in our results is a generalization of Buchber ger's criterion to standard bases of power series due to T. Becker in 1990 . This talk is based on joint work with Janusz Adamus at the University of Western Ontario\, Canada.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Tomasz Kowalczyk (Jagiellonian University) DTSTART:20200915T130000Z DTEND:20200915T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/2 DESCRIPTION:Title: Real algebraic versions of Cartan's Theorems A and B \nby Tomasz Kowalczyk (Jagiellonian University) as part of Seminario de Si ngularidades UFC\n\n\nAbstract\nIt is known that Cartan's Theorem A does n ot hold in the real algebraic case\, however I will show that it holds aft er a sequence of blowing ups along smooth centers. i.e. for any coherent s heaf on a real algebraic affine variety there exists a multi-blowup such t hat the pullback sheaf is generated by global sections. Also\, an example will be given which shows that this Theorem cannot be generalized to quasi -coherent sheaves.There are similar problems with Cartan's Theorem B\, usu ally Čech cohomology of a coherent sheaf are infinitely dimensional. I wi ll construct blown-up Čech cohomology\, and show that for some sheaves th ese cohomology vanish. Finally\, I will use this theory to show universal solvability of a real algebraic first Cousin problem\, after blowing up.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexey Pokrovskiy (University College London) DTSTART:20200922T130000Z DTEND:20200922T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/3 DESCRIPTION:Title: Rota's Basis Conjecture holds asymptotically\nby Ale xey Pokrovskiy (University College London) as part of Seminario de Singula ridades UFC\n\n\nAbstract\nRota's Basis Conjecture is a well known problem \, that states that for any collection of n bases in a rank n matroid\, it is possible to decompose all the elements into n disjoint rainbow bases. Here an asymptotic version of this is will be discussed - that it is possi ble to find n − o(n) disjoint rainbow independent sets of size n − o(n ).\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Jean-Philippe Monnier (Université d'Angers) DTSTART:20200929T140000Z DTEND:20200929T150000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/4 DESCRIPTION:Title: Some normalizations of real algebraic varieties\nby Jean-Philippe Monnier (Université d'Angers) as part of Seminario de Singu laridades UFC\n\n\nAbstract\nI will introduce the central spectrum of a co mmutative ring and explain what is a rational continuous function and a re gulous function on the central locus of a real algebraic affine variety. A fter that I will show that we can normalize in different ways real algebra ic varieties by replacing the field of rational functions by the ring of r egular functions on the real closed points\, the ring of regulous function s on the central locus and the ring of rational continuous functions on th e central locus. I will provide examples of these normalizations.\nMost of the results of the talk were obtained with G. Fichou and R. Quarez.\n\nPl ease note the irregular time. We start one hour later than usual at 11:00 (GMT-3).\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Nhan Nguyen (Basque Center for Applied Mathematics) DTSTART:20201013T130000Z DTEND:20201013T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/5 DESCRIPTION:Title: Regular projection in O-minimal structures\nby Nhan Nguyen (Basque Center for Applied Mathematics) as part of Seminario de Sin gularidades UFC\n\n\nAbstract\nIn this talk\, we will give a proof for Mos towski's regular projection theorem in o-minimal structures\, which is a p ositive answer to the question of Parusinski about a definable version of the theorem.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Alicia Dickenstein (Universidad de Buenos Aires and CONICET) DTSTART:20201103T130000Z DTEND:20201103T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/7 DESCRIPTION:Title: Iterated sparse discriminants and singular intersections of hypersurfaces\nby Alicia Dickenstein (Universidad de Buenos Aires and CONICET) as part of Seminario de Singularidades UFC\n\n\nAbstract\nIt is well known that two generic quadric surfaces intersect in a nonsingular quartic space curve\, but when the intersection is not transverse this in tersection curve may degenerate to a finite number of different possible t ypes of singular curves. In the nice paper by Farouki et al. (1989)\, the authors formulate a way of computing the condition for a degenerate inter section in this case\, which refines in the real case and with an algorith mic point of view a classical treatise by Bromwich (1906). Independently\ , Schläfli (1953) studied the degenerate intersection of two hypersurface s described by multilinear equations.\n\nIn joint work with S. di Rocco an d R. Morrison\, we present a general framework of iterated sparse discrim inants to characterize the singular intersection of hypersurfaces with a g iven monomial support A\, which generalizes both previous situations. We study the connection of iterated discriminants with the notion of mixed di scriminant and the singularities of the sparse discriminant associated to A.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Jawad Snoussi (Universidad Nacional Autónoma de México) DTSTART:20201027T140000Z DTEND:20201027T150000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/8 DESCRIPTION:Title: On the C_5 cone of complex curves and equisingularity\nby Jawad Snoussi (Universidad Nacional Autónoma de México) as part of Seminario de Singularidades UFC\n\n\nAbstract\nH. Whitney introduced seve ral cones\, candidates to a possible generalization of tangent space at si ngular points. Many of these cones have an important use in the local stud y of a singularity. In particular the cones C_3\, C_4 and C_5\, are extens ively used. The two first ones are quite well understood.\nIn this talk we present a description and a procedure to build the C_5 cone for a complex curve. The tools we use for that purpose happen to be interesting in the Lipschitz behavior of a complex curve.\n\nNote the irregular time. We star t one hour later at 11:00 (Fortaleza time\, GMT-3).\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/8/ END:VEVENT BEGIN:VEVENT SUMMARY:‪Maria Alberich-Carramiñana (Universitat Politècnica de Catalu nya) DTSTART:20201117T130000Z DTEND:20201117T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/10 DESCRIPTION:Title: From local to global properties through plane Cremona m aps\nby ‪Maria Alberich-Carramiñana (Universitat Politècnica de Ca talunya) as part of Seminario de Singularidades UFC\n\n\nAbstract\nBiratio nal transformations\, also known as Cremona maps\, are capable to transfor m a local feature into a global one and viceversa. We will revise some of these phenomena concerning plane algebraic curves and planar polynomial di fferential systems.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Marcelo Escudeiro Hernandes (Universidade Estadual de Maringá) DTSTART:20201110T130000Z DTEND:20201110T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/11 DESCRIPTION:Title: On the Tjurina number of analytic plane branches\nb y Marcelo Escudeiro Hernandes (Universidade Estadual de Maringá) as part of Seminario de Singularidades UFC\n\n\nAbstract\nIn this talk we will add ress relationships between some analytical invariants of irreducible plane curves and their semi-roots. More specifically\, we will explore the Tjur ina number of a curve and the set of Kähler differential values of the lo cal ring associated with the curve.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Octave Curmi (Alfréd Rényi Institute of Mathematics) DTSTART:20201119T130000Z DTEND:20201119T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/12 DESCRIPTION:Title: A proof of A. Gabrielov's rank theorem\nby Octave C urmi (Alfréd Rényi Institute of Mathematics) as part of Seminario de Sin gularidades UFC\n\n\nAbstract\nThis talk is about Gabrielov's rank Theorem \, a fundamental result in local complex and real-analytic geometry\, prov ed in the 1960's. Contrasting with the algebraic case\, it is not in gener al true that the analytic rank of an analytic map (that is\, the dimension of the analytic-Zariski closure of its image) is equal to the generic ran k of the map (that is\, the generic dimension of its image). This phenomen on is involved in several pathological examples in local real-analytic geo metry. Gabrielov's rank Theorem provides a formal condition for the equali ty to hold.\nDespite its importance\, the original proof is considered ver y difficult. There is no alternative proof in the literature\, besides a w ork from Tougeron\, which is itself considered very difficult. I will pres ent a new work in collaboration with André Belotto da Silva and Guillaume Rond\, where we provide a complete proof of Gabrielov's rank Theorem\, fo r which we develop formal-geometric techniques\, inspired by ideas from Ga brielov and Tougeron\, which clarify the proof. \nI will start with some f undamental examples of the phenomenon at hand\, and expose the main ingred ients of the strategy of this difficult proof.\n\nNote that this meeting t akes exceptionally place on Thursday.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Guillaume Rond (Université Aix-Marseille) DTSTART:20201201T140000Z DTEND:20201201T150000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/13 DESCRIPTION:Title: Algebraic Laurent series\nby Guillaume Rond (Univer sité Aix-Marseille) as part of Seminario de Singularidades UFC\n\n\nAbstr act\nI will review several results about the algebraic closure of the fiel d of power series in several indeterminates. This field can be equipped wi th a non-archimedean absolute value\, and considering its completion allow s us to work in a bigger field where we can use Newton's method to find ro ots of polynomials. Therefore one problem is to determine what are the ele ments of this completion that are algebraic over the field of power series . I will present analogies with the algebraic closure of the field of rati onal numbers.\n\nNotice that we start one hour later than usual!\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Maria Aparecida Soares Ruas (ICMC Universidade de São Paulo) DTSTART:20201208T130000Z DTEND:20201208T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/14 DESCRIPTION:Title: Invariants of essentially isolated determinantal singul arities (EIDS) and equisingularity\nby Maria Aparecida Soares Ruas (IC MC Universidade de São Paulo) as part of Seminario de Singularidades UFC\ n\n\nAbstract\nWe introduce invariants that control the Whitney equisingul arity of families of EIDS.\nAs an application of the results\, we give a c haracterization of generic hyperplanes using\nthe invariants.\n\nTHIS TALK IS POSTPONED TO A DIFFERENT DATE\, TO BE ANNOUNCED\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Vincent Grandjean (UFC) DTSTART:20201215T130000Z DTEND:20201215T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/15 DESCRIPTION:Title: Do regular bifurcation values exist?\nby Vincent Gr andjean (UFC) as part of Seminario de Singularidades UFC\n\n\nAbstract\nI will partially report on two works in progress one with N. Dutertre the ot her one with M. Michalska\, dealing with bifurcation values at infinity of tame mappings. This will be the opportunity to review a few definitions a nd results about this topic\, generalize and clarify some of them\, as wel l as pointing out modestly some open questions (old and new).\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Mikhail Zaidenberg (Institut Fourier de Mathematiques\, Grenoble) DTSTART:20201222T130000Z DTEND:20201222T140000Z DTSTAMP:20260422T225920Z UID:seminadiodesingularidades/16 DESCRIPTION:Title: Tits-type alternative for nonlinear automorphism groups \nby Mikhail Zaidenberg (Institut Fourier de Mathematiques\, Grenoble) as part of Seminario de Singularidades UFC\n\n\nAbstract\nThe classical T its alternative asserts that any linear group over a field of zero charact eristic is either virtually solvable\, or contains a nonabelian free sub-g roup. We survey on recent extensions of the Tits alternative to automorphi sm groups of algebraic varieties. In the case of affine varieties\, these automorphism groups are often infinite-dimensional\, hence highly nonlinea r. Sometimes\, they acts highly transitively on the variety\, that is\, m- transitively for any natural number m. According to Borel\, no algebraic g roup acts 4-transitively on an algebraic variety. We show the relations be tween the alternatives of Tits type and multiple transitivity.\n LOCATION:https://researchseminars.org/talk/seminadiodesingularidades/16/ END:VEVENT END:VCALENDAR