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<font size="3" class=""><span class="" style="font-family: Arial, Helvetica, sans-serif, serif, EmojiFont;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Dear Colleagues</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">,</span></span><br class="">
<font color="#bf5af2" class="" style="font-family: Calibri, Helvetica, sans-serif, serif, EmojiFont;"><span class=""><br class="">
</span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" class=""><span class=""><span class="" style="font-family: Arial, Helvetica, sans-serif, serif, EmojiFont;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">The
</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">next </span><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">(International) Bayes Club (</span><a href="https://www.math.vu.nl/thebayesclub/" target="_blank" rel="noopener noreferrer" class="x_OWAAutoLink" id="LPlnk987560" previewremoved="true"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">https://www.math.vu.nl/thebayesclub/</span></a><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">) </span></span><span class="" style="font-family: Arial, Helvetica, sans-serif, serif, EmojiFont;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">meeting
</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">will take place on the </span></span></span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" class=""><span class=""><b class=""><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">19th</span><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> of </span><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">March</span></b></span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" class=""><span class=""><b class=""><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> (</span><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Friday</span><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">)</span></b></span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" class=""><span class="" style="font-family: Arial, Helvetica, sans-serif, serif, EmojiFont;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> from
</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">2</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> pm</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">. We
have two speakers: </span></span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" color="#212121" class=""><span class=""><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Joris Bierkens</span><span class="" style="font-family: Arial, Helvetica, sans-serif, serif, EmojiFont;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> (</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Delft</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">)</span></span></span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" class=""><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> and </span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" color="#212121" class=""><span class=""><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Ankur
Moitra</span><span class="" style="font-family: Arial, Helvetica, sans-serif, serif, EmojiFont;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> (</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">MIT</span></span><span class="" style="font-family: Arial, Helvetica, sans-serif, serif, EmojiFont;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">).
This is a special occasion as we celebrate our 10th year anniversary. Therefore we will book a virtual </span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">meeting place at gather.town from 4pm so we can chat and
</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">toast</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> </span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">virtually
(please </span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">prepare with beers/wine/...</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">). Would be great if everyone could arrange to stay for
a while after the talks as well. </span></span></span></font></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" color="#212121" class="" style="font-size: medium;"><span class=""><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">P</span></span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" class="" style="font-size: medium;"><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">lease
find below the titles and the abstracts</span></font><font face="Helvetica,Arial,sans-serif,serif,EmojiFont" class="" style="font-size: medium;"><span class="" style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">. The seminar will be on zoom:</span></font></div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Topic: International Bayes club</span></div>
<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Time: Mar 19, 2021 02:00 PM Amsterdam</span></div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Join Zoom Meeting</span></div>
<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">https://vu-live.zoom.us/j/91629816385?pwd=T1RKLzRxTWw4N2hOcXYrb2ppMUh0UT09</span></div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Meeting ID: 916 2981 6385</span></div>
<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Passcode: 904232</span></div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">2pm lecture by </span><span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Joris Bierkens (TU Delft</span><span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">)</span></div>
<div><span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;"><br>
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<div><span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Title: </span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">The
Boomerang Sampler and Bayesian inference for diffusions</span></span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Abstract: </span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">The
Bayesian estimation of (parameters of) a diffusion process is</span></span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">challenging due to the lack of a closed form expression for the</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">transition densities. A natural approach is employing a Gibbs sampler in</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">which the diffusion process has to be simulated for a fixed choice of</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">parameters as a latent variable.</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">This simulation of a specified diffusion is challenging itself due to</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">its infinite dimensional and nonlinear nature. We discuss a recent</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">approach to this problem involving the Boomerang Sampler, which is an</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">example of a piecewise deterministic Monte Carlo sampler. The Boomerang</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Sampler has important differences as well as similarities with other</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">piecewise deterministic samplers such as the Zig-Zag process and the</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Bouncy Particle Sampler.</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">This talk is based upon joint work with Sebastiano Grazzi, Kengo</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Kamatani, Gareth Roberts, Moritz Schauer and Frank van der Meulen.</span><br>
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<div><span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">----------------</span></div>
<div><span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">3pm lecture by Ankur Moitra (MIT)</span></div>
<div><span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;"><br>
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<div><span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;"><span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Title:
An Invitation to Semi-Random Models for Bayesian Statisticians</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Abstract: The stochastic block model is one of the oldest and most ubiquitous models for studying clustering and community detection. The basic inference problem
is to use the observed graph to estimated the planted community structure that was used to generate it. Exciting recent work has precisely characterized when it is possible to achieve non-trivial accuracy, and what the optimal error behaves like. These works
all revolve around belief propagation which attempts to sample from the posterior distribution using a simple iterative algorithm.</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Here we revisit these thresholds from the perspective of semirandom models where we allow an adversary to make `helpful’ changes that strengthen ties within
each community and break ties between them. We show a surprising result that these `helpful’ changes can shift the information-theoretic threshold, making the community detection problem strictly harder. Conceptually, any algorithm meeting the exact information-theoretic
threshold in the average-case model must exploit the precise structure of the noise. These results point to an interesting new direction: Can semirandom (and related) models help explain why some algorithms are preferred to others in practice, in spite of
gaps in their average-case performance?</span><br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<br style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;">
<span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">This is based on joint work with Amelia Perry and Alex Wein.</span><br>
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<div><span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;"><span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Best
wishes,</span></span></div>
<div><span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 13.3333px;"><span style="color: rgb(33, 33, 33); font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Botond
(on behalf of the organising team)</span></span></div>
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