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<p class="MsoNormal"><span style="font-size:11.0pt">Dear all,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">The DDT&G will commence again on the 1<sup>st</sup> of april this year in Hybrid form at the VU. After the seminar we will go to the boelebar.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Please also encourage interested masterstudents to attend. The goals is to make these minicourses accessible to anyone with an interest in geometry and/or topology.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">For the PHD students: This is a nice continuation of the H-cobordism seminar you have organized in the past.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Best,<br>
Thomas</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">1-04-2022 Amsterdam/Hybrid: <a href="https://www.math.uni-bielefeld.de/~sbehrens/">Stefan Behrens </a>. Freedman's disk embedding theorem and the topology of 4-manifolds.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Schedule</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">14:00-15:00: First part of the minicourse<br>
14:30-16:30: Second part of the minicourse</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Abstract</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Freedman's disk embedding theorem is a cornerstone of 4-manifold topology. In order to appreciate the result, one has to be aware that manifold topology is divided into low and high dimensions. The border
runs somewhere in dimension 4. The high dimensional world has powerful tools to tackle classification problems for manifolds, known as surgery theory and the s-cobordism theorem. A key feature of high dimensional manifolds is the Whitney trick, which allows
to make certain geometric and algebraic intersection counts match. Unfortunately, the standard Whitney trick is not available in dimension 4 and it is known that the high-dimensional machinery does not apply to smooth 4-manifolds. In contrast, Freedman's theorem
makes the Whitney trick available for a class of topological 4-manifolds (including all simply connected ones), thereby opening the gates for surgery and s-cobordism techniques. The goal of the minicourse is to explain the statement of the disk embedding theorem,
to indicate why it is important, and to give at least a rough idea of the proof.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">See this <a href="https://www.quantamagazine.org/new-math-book-rescues-landmark-topology-proof-20210909/">Quanta magazine article about the book Stefan coauthored about this topic.</a></span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
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<p class="MsoNormal"><b><span style="color:black">From: </span></b><span style="color:black">"Rot, T.O." <t.o.rot@vu.nl><br>
<b>Date: </b>Monday, 7 March 2022 at 09:40<br>
<b>To: </b>Beta Medewerkers Wiskunde <medewerkers.wiskunde.beta@vu.nl><br>
<b>Subject: </b>Mailing list topology and geometry</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Dear all,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I have send some information about seminars etc. to the whole department. This is a bit spammy.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Therefore I have created a mailing list for those of you who are interested in geometry and topology (in a broad sense)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><a href="https://listserver.vu.nl/mailman/listinfo/topology.beta">https://listserver.vu.nl/mailman/listinfo/topology.beta</a></span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">The name of the list refers to topology only, but that is due to the character limit.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">This list is intended to be low maintenance. You should subscribe/unsubscribe yourself and you are free to send emails if you have relevant information. Please make new PhD students/ postdocs etc aware of
this mailing list. </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Best,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thomas</span><o:p></o:p></p>
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