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<div align="center"><big><b><big>Welcome to the 2025 Fall
talks of ODTÜ-Bilkent Algebraic Geometry Seminars</big></b></big><b><br>
</b></div>
<div align="center"><i>since 2000</i><br>
</div>
<div align="center"><b><b>=================================================================</b></b><br>
<br>
This week the <a
href="http://www.bilkent.edu.tr/~sertoz/agseminar.htm"
target="_blank" moz-do-not-send="true">ODTÜ-Bilkent
Algebraic Geometry Seminar</a> is <b>online</b><br>
<br>
<i><font color="#ff00ff">This talk will begin at <u><b>15:40</b></u><u> (GMT+3)</u></font></i><br>
<a
href="https://www.timeanddate.com/worldclock/fixedtime.html?msg=ODT%C3%9C-Bilkent+Algebraic+Geometry+Seminar&iso=20251024T1540&p1=19&ah=1"
target="_blank" moz-do-not-send="true">Please check
your time difference between Ankara and your city here</a><br>
<b>=================================================================<br>
<br>
</b></div>
<div align="center">
<div align="center"><img
src="cid:part1.yZYTyaOT.Lg8guACR@bilkent.edu.tr"
alt="" width="549" height="462" class=""></div>
</div>
<div align="center"><br>
</div>
<div align="center"><i>Jean-Leon Gerome (1824-1904)<br>
</i></div>
<div align="center"><i><br>
</i></div>
<div align="center"><i><br>
</i>
<div align="left">
<div align="left"><b><b><font color="#ff0000">Speaker:
</font><a moz-do-not-send="true"
href="https://sites.google.com/view/tocj/home">Türkü
Özlüm Çelik</a></b></b></div>
<b><b><font color="#ff0000"><font color="#000000"> </font></font></b></b><b><b><font
color="#ff0000">Affiliation:<i> </i></font></b></b><i><b>Max
Planck</b></i></div>
<div align="left"><b><b><i><br>
</i></b></b></div>
<div align="left"><b><b><font color="#ff0000"> Title: <font
color="#000000">Interaction Networks via
Grassmannians<br>
</font></font></b><b><font color="#ff0000"><font
color="#000000"><br>
</font></font></b></b></div>
</div>
<div align="justify"><b><b><font color="#ff0000">Abstract:
</font></b></b>When can a network of mutually
reinforcing N components remain stable? To approach such
questions, we describe the interactions through
generalized Lotka–Volterra equations—a broad class of
dynamical systems modeling how components influence one
another over time. This formulation leads to a family of
semi-algebraic sets determined by the sign pattern of
the parameters. These sets encode positivity conditions
defining regions of potential coexistence, with
polynomial degrees growing exponentially in N. Embedding
the parameter space into the real Grassmannian Gr(N,2N)
transforms these conditions into sign relations governed
by the Grassmann–Plücker equations and oriented
matroids. This geometric reformulation yields a
realization problem through which we detect impossible
interaction networks and study the algebraic structure
underlying stability. If time permits, we will also
touch on how these structures connect to algebraic
curves. This talk is based on our recent work <a
moz-do-not-send="true"
href="https://arxiv.org/abs/2509.00165">arXiv:2509.00165</a>.<b><b><font
color="#ff0000"> </font></b></b></div>
<div align="left"><br>
</div>
<div align="left"><font color="#ff0000"><font
color="#000000"><b><font color="#ff0000">Date:<font
color="#000000"> 24 October 2025, Friday</font></font></b></font></font></div>
<div align="left"><font color="#ff0000"><font
color="#000000"><b><font color="#ff0000">Time: </font>15:40 <i>(GMT+3)</i></b><br>
<b><font color="#ff0000">Place: </font></b><font
color="#ff0000"><font color="#000000"><b>Zoom</b></font></font></font></font></div>
<blockquote>
<p><i><b>Participants who have registered will receive
the Zoom link via email one day before the
seminar.</b></i></p>
<p><i><b>If you registered for a previous talk in this
series, there's no need to register again—you'll
automatically receive the link for this session.</b></i></p>
<p><i><b moz-do-not-send="true"
href="mailto:sertoz@bilkent.edu.tr">If you haven't
registered yet, please contact <a
href="mailto:sertoz@bilkent.edu.tr"
class="moz-txt-link-freetext"
moz-do-not-send="true">sertoz@bilkent.edu.tr</a>
to be added to the mailing list.</b></i></p>
</blockquote>
<div align="left">You are most cordially invited to
attend.</div>
<div align="left"><br>
</div>
<div align="left">Ali Sinan Sertöz</div>
<div align="left"><br>
</div>
<div align="center">
<div align="center"><b><font color="#0080c0"><i><b><font
color="#0080c0"><i>This seminar series is
organized by a joint team from ODTÜ and
Bilkent<br>
<br>
Alexander Degtyarev (Bilkent)<br>
Ali Sinan Sertöz (Bilkent) contact person<br>
Ali Ulaş Özgür Kişisel (ODTÜ)<br>
Yıldıray Ozan (ODTÜ)<br>
</i></font></b></i></font></b></div>
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</div>
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<hr>
<pre cols="72">----------------------------------------------------------------------------
Ali Sinan Sertöz
Bilkent University, Department of Mathematics, 06800 Ankara, Türkiye
Office: (90)-(312) - 290 1490
Department: (90)-(312) - 266 4377
e-mail: <a href="mailto:sertoz@bilkent.edu.tr" target="_blank"
class="gmail-moz-txt-link-freetext moz-txt-link-freetext"
moz-do-not-send="true">sertoz@bilkent.edu.tr</a>
Web: <a href="http://sertoz.bilkent.edu.tr" target="_blank"
moz-do-not-send="true">sertoz.bilkent.edu.tr</a>
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