BEGIN:VCALENDAR
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BEGIN:VEVENT
SUMMARY:Ilia Itenberg (imj-prg)
DTSTART;VALUE=DATE-TIME:20220304T124000Z
DTEND;VALUE=DATE-TIME:20220304T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/1
DESCRIPTION:Title: Re
al enumerative invariants and their refinement\nby Ilia Itenberg (imj-
prg) as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstract\nTh
e talk is devoted to several real and tropical enumerative problems. We su
ggest new invariants of the projective plane (and\, more generally\, of to
ric surfaces) that arise as results of an appropriate enumeration of real
elliptic curves.\nThese invariants admit a refinement (according to the qu
antum index) similar to the one introduced by Grigory Mikhalkin in the rat
ional case. We discuss tropical counterparts of the elliptic invariants un
der consideration and establish a tropical algorithm allowing one to compu
te them.\nThis is a joint work with Eugenii Shustin.\n
LOCATION:https://researchseminars.org/talk/OBAGS/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexander Degtyarev (Bilkent)
DTSTART;VALUE=DATE-TIME:20220311T124000Z
DTEND;VALUE=DATE-TIME:20220311T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/2
DESCRIPTION:Title: To
wards 800 conics on a smooth quartic surfaces\nby Alexander Degtyarev
(Bilkent) as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstrac
t\nThis will be a technical talk where I will discuss a few computational
aspects of my work in progress towards the following conjecture.\n\nConjec
ture: A smooth quartic surface in P3 may contain at most 800 conics.\n\nI
will suggest and compare several arithmetical reductions of the problem. T
hen\, for the chosen one\, I will discuss a few preliminary combinatorial
bounds and some techniques used to handle the few cases where those bounds
are not sufficient.\n\nAt the moment\, I am quite confident that the conj
ecture holds. However\, I am trying to find all smooth quartics containing
720 or more conics\, in the hope to find the real quartic maximizing the
number of real lines and to settle yet another conjecture (recall that we
count all conics\, both irreducible and reducible).\n\nConjecture: If a s
mooth quartic X⊂P3 contains more than 720 conics\, then X has no lines\;
in particular\, all conics are irreducible.\n\nCurrently\, similar bounds
are known only for sextic K3-surfaces in P4.\n\nAs a by-product\, I have
found a few examples of large configurations of conics that are not Barth-
-Bauer\, i.e.\, do not contain\na 16-tuple of pairwise disjoint conics or\
, equivalently\, are not Kummer surfaces with all 16 Kummer divisors conic
s.\n
LOCATION:https://researchseminars.org/talk/OBAGS/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matthias Schütt (Hannover)
DTSTART;VALUE=DATE-TIME:20220318T124000Z
DTEND;VALUE=DATE-TIME:20220318T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/3
DESCRIPTION:Title: Fi
nite symplectic automorphism groups of supersingular K3 surfaces\nby M
atthias Schütt (Hannover) as part of ODTU-Bilkent Algebraic Geometry Semi
nars\n\n\nAbstract\nAutomorphism groups form a classical object of study i
n algebraic geometry. In recent years\, a special focus has been put on au
tomorphisms of K3 surface\, the most famous example being Mukai’s classi
fication of finite symplectic automorphism groups on complex K3 surfaces.
Building on work of Dolgachev-Keum\, I will discuss a joint project with H
isanori Ohashi (Tokyo) extending Mukai’s results to fields positive char
acteristic. Notably\, we will retain the close connection to the Mathieu g
roup M23 while realizing many larger groups compared to the complex settin
g.\n
LOCATION:https://researchseminars.org/talk/OBAGS/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emre Can Sertöz (Hannover)
DTSTART;VALUE=DATE-TIME:20220325T124000Z
DTEND;VALUE=DATE-TIME:20220325T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/4
DESCRIPTION:Title: He
ights\, periods\, and arithmetic on curves\nby Emre Can Sertöz (Hanno
ver) as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstract\nTh
e size of an explicit representation of a given rational point on an algeb
raic curve is captured by its canonical height. However\, the canonical he
ight is defined through the dynamics on the Jacobian and is not particular
ly accessible to computation. In 1984\, Faltings related the canonical hei
ght to the transcendental "self-intersection" number of the point\, which
was recently used by van Bommel-- Holmes--Müller (2020) to give a general
algorithm to compute heights. The corresponding notion for heights in hig
her dimensions is inaccessible to computation. We present a new method for
computing heights that promises to generalize well to higher dimensions.
This is joint work with Spencer Bloch and Robin de Jong.\n
LOCATION:https://researchseminars.org/talk/OBAGS/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Halil İbrahim Karakaş (Başkent)
DTSTART;VALUE=DATE-TIME:20220401T124000Z
DTEND;VALUE=DATE-TIME:20220401T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/5
DESCRIPTION:Title: Ar
f Partitions of Integers\nby Halil İbrahim Karakaş (Başkent) as par
t of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstract\nThe colection
of partitions of positive integers\, the collection of Young diagrams and
the collection of numerical sets are in one to one correspondance with ea
ch other. Therefore any concept in one of these collections has its counte
rpart in the other collections. For example the concept of Arf numerical s
emigroup in the collection of numerical sets\, gives rise to the concept o
f Arf partition of a positive integer in the collection of partitions. Sev
eral characterizations of Arf partitions have been given in recent works.
In this talk we wil characterize Arf partitions of maximal length of posit
ive integers.\nThis is a joint work with Nesrin Tutaş and Nihal Gümüşb
aş from Akdeniz University.\n
LOCATION:https://researchseminars.org/talk/OBAGS/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yıldıray Ozan (ODTÜ)
DTSTART;VALUE=DATE-TIME:20220408T124000Z
DTEND;VALUE=DATE-TIME:20220408T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/6
DESCRIPTION:Title: Pi
card Groups of the Moduli Spaces of Riemann Surfaces with Certain Finite A
belian Symmetry Groups\nby Yıldıray Ozan (ODTÜ) as part of ODTU-Bil
kent Algebraic Geometry Seminars\n\n\nAbstract\nIn 2021\, H. Chen determin
ed all finite abelian regular branched covers of the 2-sphere with the pro
perty that all homeomorphisms of the base preserving the branch set lift t
o the cover\, extending the previous works of Ghaswala-Winarski and Atalan
-Medettoğulları-Ozan. In this talk\, we will present a consequence of th
is classification to the computation of Picard groups of moduli spaces of
complex projective curves with certain symmetries. Indeed\, we will use th
e work by K. Kordek already used by him for similar computations. During t
he talk we will try to explain the necessary concepts and tools following
Kordek's work.\n
LOCATION:https://researchseminars.org/talk/OBAGS/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ali Ulaş Özgür Kişisel (ODTÜ)
DTSTART;VALUE=DATE-TIME:20220415T124000Z
DTEND;VALUE=DATE-TIME:20220415T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/7
DESCRIPTION:Title: An
upper bound on the expected areas of amoebas of plane algebraic curves\nby Ali Ulaş Özgür Kişisel (ODTÜ) as part of ODTU-Bilkent Algebraic
Geometry Seminars\n\n\nAbstract\nThe amoeba of a complex plane algebraic
curve has an area bounded above by $\\pi^2 d^2/2$. This is a deterministic
upper bound due to Passare and Rullgard. In this talk I will argue that i
f the plane curve is chosen randomly with respect to the Kostlan distribut
ion\, then the expected area cannot be more than $\\mathcal{O}(d)$. The re
sults in the talk will be based on our joint work in progress with Turgay
Bayraktar.\n
LOCATION:https://researchseminars.org/talk/OBAGS/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Muhammed Uludağ (Galatasaray)
DTSTART;VALUE=DATE-TIME:20220422T124000Z
DTEND;VALUE=DATE-TIME:20220422T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/8
DESCRIPTION:Title: He
yula\nby Muhammed Uludağ (Galatasaray) as part of ODTU-Bilkent Algebr
aic Geometry Seminars\n\n\nAbstract\nThis talk is about the construction o
f a space H and its boundary on which the group PGL(2\,Q) acts. The ultima
te aim is to recover the action of PSL(2\,Z) on the hyperbolic plane as a
kind of boundary action.\n
LOCATION:https://researchseminars.org/talk/OBAGS/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Melih Üçer (Yıldırım Beyazıt)
DTSTART;VALUE=DATE-TIME:20220429T124000Z
DTEND;VALUE=DATE-TIME:20220429T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/9
DESCRIPTION:Title: Bu
rau Monodromy Groups of Trigonal Curves\nby Melih Üçer (Yıldırım
Beyazıt) as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstrac
t\nFor a trigonal curve on a Hirzebruch surface\, there are several notion
s of monodromy ranging from a very coarse one in S_3 to a very fine one in
a certain subgroup of Aut(F_3)\, and one group in this range is PSL(2\,Z)
. Except for the special case of isotrivial curves\, the monodromy group (
the subgroup generated by all monodromy actions) in PSL(2\,Z) is a subgrou
p of genus-zero and conversely any genus-zero subgroup is the monodromy gr
oup of a trigonal curve (This is a result of Degtyarev).\n\nA slightly fin
er notion in the same range is the monodromy in the Burau group Bu_3. The
aforementioned result of Degtyarev imposes obvious restrictions on the mon
odromy group in this case but without a converse result. Here we show that
there are additional non-obvious restrictions as well and\, with these re
strictions\, we show the converse as well.\n
LOCATION:https://researchseminars.org/talk/OBAGS/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Andrew Sutherland (MIT)
DTSTART;VALUE=DATE-TIME:20221014T124000Z
DTEND;VALUE=DATE-TIME:20221014T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/10
DESCRIPTION:Title: S
ato-Tate groups of abelian varieties\nby Andrew Sutherland (MIT) as pa
rt of ODTU-Bilkent Algebraic Geometry Seminars\n\nLecture held in ODTÜ Ma
thematics department Room M-203.\n\nAbstract\nLet A be an abelian variety
of dimension g defined over a number field K. As defined by Serre\, the S
ato-Tate group ST(A) is a compact subgroup of the unitary symplectic group
USp(2g) equipped with a map that sends each Frobenius element of the abso
lute Galois group of K at primes p of good reduction for A to a conjugacy
class of ST(A) whose characteristic polynomial is determined by the zeta f
unction of the reduction of A at p. Under a set of axioms proposed by Ser
re that are known to hold for g <= 3\, up to conjugacy in Usp(2g) there is
a finite list of possible Sato-Tate groups that can arise for abelian var
ieties of dimension g over number fields. Under the Sato-Tate conjecture
(which is known for g=1 when K has degree 1 or 2)\, the asymptotic distrib
ution of normalized Frobenius elements is controlled by the Haar measure o
f the Sato-Tate group.\n\nIn this talk I will present a complete classific
ation of the Sato-Tate groups that can and do arise for g <= 3.\n\nThis is
joint work with Francesc Fite and Kiran Kedlaya.\n\nThis is a hybrid talk
. To request Zoom link please write to sertoz@bilkent.edu.tr\n
LOCATION:https://researchseminars.org/talk/OBAGS/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emre Coşkun (METU)
DTSTART;VALUE=DATE-TIME:20221021T124000Z
DTEND;VALUE=DATE-TIME:20221021T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/11
DESCRIPTION:Title: M
cKay correspondence I\nby Emre Coşkun (METU) as part of ODTU-Bilkent
Algebraic Geometry Seminars\n\nLecture held in ODTÜ Mathematics departmen
t Room M-203.\n\nAbstract\nJohn McKay observed\, in 1980\, that there is a
one-to-one correspondence between the nontrivial finite subgroups of SU(2
) (up to conjugation) and connected Euclidean graphs (other than the Jorda
n graph) up to isomorphism. In these talk\, we shall first examine the fin
ite subgroups of SU(2) and then establish this one-to-one correspondence\,
using the representation theory of finite groups.\n\nThis is a hybrid tal
k. To request a Zoom link please write to sertoz@bilkent.edu.tr\n
LOCATION:https://researchseminars.org/talk/OBAGS/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emre Coşkun (METU)
DTSTART;VALUE=DATE-TIME:20221104T124000Z
DTEND;VALUE=DATE-TIME:20221104T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/12
DESCRIPTION:Title: M
cKay correspondence II\nby Emre Coşkun (METU) as part of ODTU-Bilkent
Algebraic Geometry Seminars\n\nLecture held in ODTÜ Mathematics Departme
nt Room M-203.\n\nAbstract\nLet $G \\subset SU(2)$ be a finite subgroup co
ntaining $-I$\, and let \n$Q$ be the corresponding Euclidean graph. Given
an orientation on $Q$\, \none can define the (bounded) derived category of
the representations \nof the resulting quiver. Let $\\bar{G} = G / {\\pm
I}$. Then one can \nalso define the category $Coh_{\\bar{G}}(\\mathbb{P}^1
)$ of \n$\\bar{G}$-equivariant coherent sheaves on the projective line\; t
his \nabelian category also has a (bounded) derived category. In the secon
d \nof these talks dedicated to the McKay correspondence\, we establish an
\nequivalence between the two derived categories mentioned above.\n\nThis
is a hybrid talk. To request Zoom link please write to sertoz@bilkent.edu
.tr.\n
LOCATION:https://researchseminars.org/talk/OBAGS/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Emre Can Sertöz (Hannover)
DTSTART;VALUE=DATE-TIME:20221111T124000Z
DTEND;VALUE=DATE-TIME:20221111T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/13
DESCRIPTION:Title: C
omputing limit mixed Hodge structures\nby Emre Can Sertöz (Hannover)
as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstract\nConside
r a smooth family of varieties over a punctured disk that is extended to a
flat family over the whole disk\, e.g.\, consider a 1-parameter family of
hypersurfaces with a central singular fiber. The Hodge structures (i.e. p
eriods) of smooth fibers exhibit a divergent behavior as you approach the
singular fiber. However\, Schmid's nilpotent orbit theorem states that thi
s divergence can be "regularized" to construct a limit mixed Hodge structu
re. This limit mixed Hodge structure contains detailed information about t
he geometry and arithmetic of the singular fiber. I will explain how one c
an compute such limit mixed Hodge structures in practice and give a demons
tration of my code.\n
LOCATION:https://researchseminars.org/talk/OBAGS/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Müfit Sezer (Bilkent)
DTSTART;VALUE=DATE-TIME:20221118T124000Z
DTEND;VALUE=DATE-TIME:20221118T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/14
DESCRIPTION:Title: V
ector invariants of a permutation group over characteristic zero\nby M
üfit Sezer (Bilkent) as part of ODTU-Bilkent Algebraic Geometry Seminars\
n\n\nAbstract\nWe consider a finite permutation group acting naturally on
a vector space V over a field k. A well known theorem of Göbe
l asserts that the corresponding ring of invariants k[V]^G is genera
ted by invariants of degree at most dim V choose 2. We point out th
at if the characteristic of k is zero then the top degree of the vec
tor coinvariants k[mV]_G is also bounded above by n choose 2 i
mplying that Göbel's bound almost holds for vector invariants as well in
characteristic zero.\nThis work is joint with F. Reimers.\n
LOCATION:https://researchseminars.org/talk/OBAGS/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Davide Cesare Veniani (Stuttgart)
DTSTART;VALUE=DATE-TIME:20221125T124000Z
DTEND;VALUE=DATE-TIME:20221125T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/15
DESCRIPTION:Title: N
on-degeneracy of Enriques surfaces\nby Davide Cesare Veniani (Stuttgar
t) as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstract\nEnri
ques' original construction of Enriques surfaces involves a 10-dimensional
family of sextic surfaces in the projective space which are non-normal al
ong the edges of a tetrahedron. The question whether all Enriques surfaces
arise through Enriques' construction has remained open for more than a ce
ntury.\n\nIn two joint works with G. Martin (Bonn) and G. Mezzedimi (Hanno
ver)\, we have now settled this question in all characteristics by studyin
g particular configurations of genus one fibrations\, and two invariants c
alled maximal and minimal non-degeneracy. The proof involves so-called `tr
iangle graphs' and the distinction between special and non-special 3-seque
nces of half-fibers.\n\nIn this talk\, I will present the problem and expl
ain its solution\, illustrating further possible developments and applicat
ions.\n
LOCATION:https://researchseminars.org/talk/OBAGS/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Fatma Karaoğlu (Gebze Teknik)
DTSTART;VALUE=DATE-TIME:20221202T124000Z
DTEND;VALUE=DATE-TIME:20221202T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/16
DESCRIPTION:Title: S
mooth cubic surfaces with 15 lines\nby Fatma Karaoğlu (Gebze Teknik)
as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstract\nIt is w
ell-known that a smooth cubic surface has 27 lines over an algebraically c
losed field. If the field is not closed\, however\, fewer lines are possib
le. The next possible case is that of smooth cubic surfaces with 15 lines.
This work is a contribution to the problem of classifying smooth cubic su
rfaces with 15 lines over fields of positive characteristic. We present an
algorithm to classify such surfaces over small finite fields. Our classif
ication algorithm is based on a new normal form of the equation of a cubic
surface with 15 lines and less than 10 Eckardt points. The case of cubic
surfaces with more than 10 Eckardt points is dealt with separately. Classi
fication results for fields of order at most 13 are presented and a verifi
cation using an enumerative formula of Das is performed. Our work is based
on a generalization of the old result due to Cayley and Salmon that there
are 27 lines if the field is algebraically closed.\n\n Smooth cubic surfa
ces with 15 lines\n
LOCATION:https://researchseminars.org/talk/OBAGS/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Meral Tosun (Galatasaray)
DTSTART;VALUE=DATE-TIME:20221209T124000Z
DTEND;VALUE=DATE-TIME:20221209T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/17
DESCRIPTION:Title: J
ets schemes and toric embedded resolution of rational triple points\nb
y Meral Tosun (Galatasaray) as part of ODTU-Bilkent Algebraic Geometry Sem
inars\n\n\nAbstract\nOne of the aims of J.Nash in an article on the arcs s
paces (1968) was to understand resolutions of singularities via the arcs l
iving on the singular variety. He conjectured that there is a one-to-one
relation between a family of the irreducible components of the jet schemes
of an hypersurface centered at the singular point and the essential divis
ors on every resolution. J.Fernandez de Bobadilla and M.Pe Pereira (2011)
have shown his conjecture\, but the proof is not constructive to get the r
esolution from the arc space. We will construct an embedded toric resoluti
on of singularities of type rtp from the irreducible components of the jet
schemes.\n\nThis is a joint work with B.Karadeniz\, H. Mourtada and C.Ple
nat.\n
LOCATION:https://researchseminars.org/talk/OBAGS/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Özhan Genç (Jagiellonian)
DTSTART;VALUE=DATE-TIME:20221216T124000Z
DTEND;VALUE=DATE-TIME:20221216T134000Z
DTSTAMP;VALUE=DATE-TIME:20221209T130608Z
UID:OBAGS/18
DESCRIPTION:Title: F
inite Length Koszul Modules and Vector Bundles\nby Özhan Genç (Jagie
llonian) as part of ODTU-Bilkent Algebraic Geometry Seminars\n\n\nAbstract
\nLet $V$ be a complex vector space of dimension $n\\ge 2$ and $K$ be a s
ubset of $\\bigwedge^2V$ of dimension $m$. Denote the Koszul module by $W(
V\,K)$ and its corresponding resonance variety by $\\mathcal R(V\,K)$. Pap
adima and Suciu showed that there exists a uniform bound $q(n\,m)$ such th
at the graded component of the Koszul module $W_q(V\,K)=0$ for all $q\\ge
q(n\,m)$ and for all $(V\,K)$ satisfying $\\mathcal R(V\,K)=\\{0\\}$. In t
his talk\, we will determine this bound $q(n\,m)$ precisely\, and find an
upper bound for the Hilbert series of these Koszul modules. Then we will c
onsider a class of Koszul modules associated to vector bundles.\n
LOCATION:https://researchseminars.org/talk/OBAGS/18/
END:VEVENT
END:VCALENDAR