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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Dear all,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Next week there is no CTAAAG, but there is a DDT&G at the VU. Please let your students know as well.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Thomas<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-family:"Calibri",sans-serif;color:black">From:
</span></b><span style="font-family:"Calibri",sans-serif;color:black">Federica Pasquotto <f.pasquotto@math.leidenuniv.nl><br>
<b>Date: </b>Friday, 21 March 2025 at 11:00<br>
<b>To: </b>Federica Pasquotto <f.pasquotto@math.leidenuniv.nl><br>
<b>Subject: </b>DDT&G seminar @Amsterdam on 28 March: Mélanie Theillière <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Dear all, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">You are cordially invited to attend the next Dutch Differential Topology and Geometry seminar, which will take place next week in Amsterdam. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:black">Speaker</span></b><span style="color:black">: Mélanie Theillière (Université du Luxembourg)<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="color:black">Date</span></b><span style="color:black">: Friday 28 March, 14:30-17:00<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="color:black">Location</span></b><span style="color:black">: VU Amsterdam, HG-08A20 (please notice that this is not the usual room, but a lecture room in the main building)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">In this instance, the seminar will consists of two independent talks, of which the second one will be at a slightly more advanced level.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Master students with an interest in geometry and topology are warmly encouraged to participate in both talks!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:black">Schedule:</span></b><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">2:30-3:30 p.m. - F<b>irst talk</b>: "<i>Corrugations and differential constraints"</i><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">3:30-4:00 - coffee break<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">4:00-5:00 p.m. - S<b>econd talk</b>:
<i>"The hyperbolic plane in R^3"</i><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">(see below for the abstracts)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">Please visit the seminar's webpage for additional information and an overview of past and upcoming talks:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><br>
</span><u><span style="color:blue"><a href="https://www.few.vu.nl/~trt800/ddtg.html" target="_blank" title="Original URL: https://www.few.vu.nl/~trt800/ddtg.html. Click or tap if you trust this link.">https://www.few.vu.nl/~trt800/</a></span></u><u><span style="color:#070706"><a href="https://www.few.vu.nl/~trt800/ddtg.html" target="_blank" title="Original URL: https://www.few.vu.nl/~trt800/ddtg.html. Click or tap if you trust this link."><span style="color:#070706">ddt</span></a></span></u><u><span style="color:blue"><a href="https://www.few.vu.nl/~trt800/ddtg.html" target="_blank" title="Original URL: https://www.few.vu.nl/~trt800/ddtg.html. Click or tap if you trust this link.">g.html</a></span></u><o:p></o:p></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">We hope to see many of you next week!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">Alvaro, Federica and Thomas<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="color:black">Abstracts</span></b><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><i><span style="color:black">First talk: Corrugations and differential constraints </span></i><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="line-height:13.5pt"><span style="color:black">We will present a corrugation formula, and we will use it to solve two problems in differential topology/geometry:<br>
(1) Removing singular points of a map.<br>
(2) Building (epsilon)-isometric maps. I.e. maps that are isometries (i.e. preserve lengths) up to a small, prescribed error.<br>
Then we will provide a historical overview of such kinds of formulas.<o:p></o:p></span></p>
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<p class="MsoNormal" style="line-height:13.5pt"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="line-height:13.5pt"><i><span style="color:black">Second talk: The hyperbolic plane in R^3<b> </b></span></i><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="line-height:13.5pt"><span style="color:black">According to theorem of Nash and Kuiper, we know that it is possible to isometrically embed the hyperbolic plane into Euclidean 3-space. However, such an embedding only exists in C^1-regularity.
By a theorem of Hilbert-Efimov, the regularity can not be enhanced to be C^2. In this talk, we will explicitly build such a C^1-embedding and we will explore its geometry.<o:p></o:p></span></p>
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