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BEGIN:VEVENT
SUMMARY:Simon Felten (JGU Mainz)
DTSTART:20210412T141500Z
DTEND:20210412T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/1
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/1/">The logarithmic Bogomolov-Tian-Todorov theorem</a>\nb
 y Simon Felten (JGU Mainz) as part of Algebraic geometry Freie Universitä
 t Berlin\n\n\nAbstract\nA variety V with only normal crossing singularitie
 s does only admit a semistable smoothing if it is d-semistable\, but this 
 condition is not sufficient. However\, d-semistability is sufficient to en
 dow V with the structure of a logarithmically smooth log morphism to the s
 tandard log point\; then constructing a semistable smoothing becomes essen
 tially equivalent to constructing an infinitesimal log smooth deformation 
 of V up to any order. Morally\, but not in practice\, this is achieved by 
 a logarithmic Bogomolov--Tian--Todorov Theorem---the unobstructedness of t
 he log smooth deformation functor---in case that V is Calabi--Yau. In view
  of Iacono--Manetti's algebraic proof of the classical BTT theorem\, we ne
 ed a dgla which controls the log smooth deformation functor. However\, the
  straightforward approach fails for rather obvious reasons. Instead\, we s
 tudy deformations of the Gerstenhaber algebra of log polyvector fields. On
  the one hand\, this yields the sought-after replacement of the dgla. On t
 he other hand\, this yields by results of Chan--Leung--Ma a weaker unobstr
 uctedness result\; nonetheless\, it is sufficient to construct semistable 
 smoothings and implies---by local algebra---the full logarithmic Bogomolov
 --Tian--Todorov Theorem.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Mattia Talpo (University of Pisa)
DTSTART:20210419T141500Z
DTEND:20210419T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/2
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/2/">Topological realization over C((t)) via Kato-Nakayama
  spaces</a>\nby Mattia Talpo (University of Pisa) as part of Algebraic geo
 metry Freie Universität Berlin\n\n\nAbstract\nI will talk about some join
 t work with Piotr Achinger\, about a “Betti realization” functor for v
 arieties over the formal punctured disk Spec C((t))\, i.e. defined by poly
 nomials with coefficients in the field of formal Laurent series in one var
 iable over the complex numbers. We give two constructions producing the sa
 me result\, one of them (the one that I'll actually talk about) via “goo
 d models” over the power series ring C[[t]] and the “Kato-Nakayama” 
 construction in logarithmic geometry\, that I will review during the talk.
 \n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonathan Lai (Imperial College London)
DTSTART:20210503T141500Z
DTEND:20210503T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/3
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/3/">Compactified Mirror Families for Log Calabi-Yau Surfa
 ces</a>\nby Jonathan Lai (Imperial College London) as part of Algebraic ge
 ometry Freie Universität Berlin\n\n\nAbstract\nWe present a compactificat
 ion of mirror families for positive pairs (Y\,D) where Y is a smooth proje
 ctive surface and D is an anti-canonical cycle of rational curves. It ends
  up that this compactified family can be realized as the moduli space of c
 ertain marked pairs deformation equivalent to the original pair (Y\,D). To
  obtain this identification\, the period associated to each fiber is compu
 ted using techniques from tropical geometry. This is ongoing joint work wi
 th Yan Zhou.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lara Bossinger (UNAM Oaxaca)
DTSTART:20210517T141500Z
DTEND:20210517T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/4
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/4/">Toric Degenerations: Embeddings and Projections</a>\n
 by Lara Bossinger (UNAM Oaxaca) as part of Algebraic geometry Freie Univer
 sität Berlin\n\n\nAbstract\nI will report on joint work in progress with 
 Takuya Murata. We study toric degenerations\, i.e. flat families over the 
 affine line whose special fibre is a projective toric variety. They can be
  given abstractly\, with an embedding or even have the property that there
  is a projection from the generic to the special fiber. Algebraically the 
 latter corresponds to an embedding of the toric algebra into the homogeneo
 us coordinate ring of the generic fibre. Using valuations and Gröbner the
 ory to give equations for embedded toric degenerations\, standard monomial
  theory provides a useful tool to construct such projections.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marian Aprodu (University of Bucharest)
DTSTART:20210531T141500Z
DTEND:20210531T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/5
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/5/">Green's conjecture and vanishing of Koszul modules</a
 >\nby Marian Aprodu (University of Bucharest) as part of Algebraic geometr
 y Freie Universität Berlin\n\n\nAbstract\nI report on a joint work with G
 . Farkas\, S. Papadima\, C. Raicu and J. Weyman. Koszul modules are multi-
 linear algebra objects associated to an arbitrary subspace in a second ext
 erior power. They are naturally presented as graded pieces of some Tor-s o
 ver the dual exterior algebra. Koszul modules appear in Geometric Group Th
 eory\, in relations with Alexander invariants of groups. We prove an optim
 al vanishing result for the Koszul modules\, and we use representation the
 ory to connect the syzygies of rational cuspidal curves to some particular
  Koszul modules. We apply our vanishing result to Algebraic Geometry exhib
 iting a new proof of Green’s conjecture on syzygies of canonical general
  curves\, and to Geometric Group Theory.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Milena Wrobel (Universität Oldenburg)
DTSTART:20210426T141500Z
DTEND:20210426T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/6
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/6/">Intrinsic Grassmannians</a>\nby Milena Wrobel (Univer
 sität Oldenburg) as part of Algebraic geometry Freie Universität Berlin\
 n\n\nAbstract\nGeneralizing the well-known weighted Grassmanians introduce
 d by Corti and Reid\, we introduce the notion of intrinsic Grassmannians\,
  i.e. normal projective varieties whose Cox ring is defined by the Plücke
 r ideal $I_{k\,n}$. For $k = 2$\, we classify the smooth Fano ones having 
 Picard number two and give a concrete formula to compute their number for 
 arbitrary $n$.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aniket Shah (Ohio State University)
DTSTART:20210614T141500Z
DTEND:20210614T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/7
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/7/">A q-analogue of Brion's identity from quasimap spaces
 </a>\nby Aniket Shah (Ohio State University) as part of Algebraic geometry
  Freie Universität Berlin\n\n\nAbstract\nFor a polytope P\, Brion's ident
 ity is a useful formula for the lattice point generating function of P\, w
 hich was originally proved via equivariant K-theory on the associated tori
 c variety X.\n\nWe prove a q-analogue of this identity via equivariant K-t
 heory on certain compactifications of the space of maps from P^1 to X call
 ed quasimap spaces\, which were introduced by Givental in the context of G
 romov-Witten theory. In the special case of P a standard simplex\, we obta
 in an identity for the multivariate Rogers-Szego orthogonal polynomials as
  a sum involving specializations of the quantum K-theoretic J-function.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Enrica Mazzon (MPI Bonn)
DTSTART:20210607T141500Z
DTEND:20210607T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/8
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/8/">Toric geometry and integral affine structures in non-
 archimedean mirror symmetry</a>\nby Enrica Mazzon (MPI Bonn) as part of Al
 gebraic geometry Freie Universität Berlin\n\n\nAbstract\nThe SYZ conjectu
 re is a conjectural geometric explanation of mirror symmetry. Based on thi
 s\, Kontsevich and Soibelman proposed a non-archimedean approach to mirror
  symmetry. This led to the notion of essential skeleton and the constructi
 on of non-archimedean SYZ fibrations by Nicaise-Xu-Yu.\n\nIn this talk\, I
  will introduce these objects and report on recent results extending the a
 pproach of Nicaise-Xu-Yu. This yields new types of non-archimedean retract
 ions. For families of quartic K3 surfaces and quintic 3-folds\, the new re
 tractions relate nicely with the results on the dual complex of toric dege
 nerations and on the Gromov-Hausdorff limit of the family.\n\nThis is base
 d on a work in progress with Léonard Pille-Schneider.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Thomas Krämer (Humboldt-Universität zu Berlin)
DTSTART:20210628T141500Z
DTEND:20210628T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/9
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/9/">Big monodromy theorems on abelian varieties</a>\nby T
 homas Krämer (Humboldt-Universität zu Berlin) as part of Algebraic geome
 try Freie Universität Berlin\n\n\nAbstract\nLawrence and Sawin have shown
  that up to translation\, any abelian variety over a number field contains
  at most finitely many smooth ample hypersurfaces with given class in the 
 Néron-Severi group and with good reduction outside a given finite set of 
 primes. A key ingredient in their proof is a big monodromy theorem for hyp
 ersurfaces\, which amounts to a statement about the Tannaka group of certa
 in D-modules on abelian varieties. In the talk I will give a motivated int
 roduction to the geometry of such Tannaka groups and discuss recent progre
 ss towards big monodromy theorems for subvarieties of higher codimension (
 this is ongoing work with Ariyan Javanpeykar\, Christian Lehn and Marco Ma
 culan).\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rita Pardini (University of Pisa)
DTSTART:20210705T134500Z
DTEND:20210705T144500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/10
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/10/">Deformations of semi-smooth varieties</a>\nby Rita P
 ardini (University of Pisa) as part of Algebraic geometry Freie Universit
 ät Berlin\n\n\nAbstract\nA variety X is semi-smooth if locally in the e't
 ale topology its singularities are either double crossing points (xy=0) or
  pinch points (x^2-y^2z=0). Alternatively\, X is semi-smooth if it can be 
 obtained from a smooth variety X' by gluing it along a smooth divisor D' v
 ia an involution g of D'. We describe explicitly in terms of the triple (X
 '\,D'\, g) the two sheaves on X that control its deformation theory\, that
  is\, the tangent sheaf T_X and the sheaf T^1_X:=ext^1(\\Omega_X\,O_X). As
  an application\, we show  the smoothability of the semi-smooth Godeaux su
 rfaces (K^2=1\, p_g=q=0).\nThis is joint work with Barbara Fantechi and Ma
 rco Franciosi.\n\nPlease note the unusual time! This talk starts at 15:45 
 (Germany/France/Italy times) on Monday the 5th of July.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/10
 /
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matteo Varbaro (University of Genova)
DTSTART:20210621T141500Z
DTEND:20210621T154500Z
DTSTAMP:20260404T111111Z
UID:algebraic_geometry_FU/11
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/algeb
 raic_geometry_FU/11/">Singularities\, Serre conditions and h-vectors</a>\n
 by Matteo Varbaro (University of Genova) as part of Algebraic geometry Fre
 ie Universität Berlin\n\n\nAbstract\nLet R be a standard graded algebra o
 ver a field\, and denote by H_R(t) its Hilbert series. As it turns out\, m
 ultiplying H_R(t) by (1-t)^{dim R} yields a polynomial h((t)=h_0+h_1t+h_2t
 ^2+…+h_st^s\, known as the h-polynomial of R. It is well known and easy 
 to prove that if R is Cohen-Macaulay h_i is nonnegative for all i.\nSince 
 being Cohen-Macaulay is equivalent to satisfying Serre condition (S_i) for
  all i\, it is licit to ask if h_i is nonnegative for all i<=r whenever R 
 satisfies (S_r).\nAs it turns out\, this is false in general\, but true pu
 tting some additional assumptions on the singularities of R. In characteri
 stic 0\, it is enough that X= Proj R is Du Bois (in particular\, if X is s
 mooth we have the desired nonnegativity). In positive characteristic\, ass
 uming R is F-split (equivalently\, if X=Proj R globally F-split)\, things 
 work well. In this talk I will speak of the above results and some of thei
 r consequences. This is a joint work with Hailong Dao and Linquan Ma.\n
LOCATION:https://stable.researchseminars.org/talk/algebraic_geometry_FU/11
 /
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