###### Corona update

All physical activity is suspended until further notice, due to Covid19. Some activites may take place virtually, please be in touch with organisers.

Some older events may be found on the pages of the Center for Advanced Studies.

### Past Events

• Online Special seminar: The Day after COVID-19 Lockdown May 12, 15:10—16:00, 2020.

Speaker: Shai Shalev-Shwartz (CS- HUJI)

Title: The Day after COVID-19 Lockdown

Abstract: Given the latest statistics, we predict that with a proper differential social distancing placing different guidelines on the low-risk group compared to the high-risk group one could maintain a working economy without quarantine and save a factor of 5 on mortality while not flooding the health system. The talk will highlight some of the computational tools used to reach these conclusions.

Based on joint work with Amnon Shashua

Here are some relevant articles:

https://medium.com/@amnon.shashua/the-day-after-covid-19-lockdown-need-to-focus-on-the-vulnerable-42c0a360a27

https://medium.com/@amnon.shashua/the-path-for-economic-revival-4d60d652b381

https://medium.com/amnon-shashua/can-we-contain-covid-19-without-locking-down-the-economy-2a134a71873f

• Special Lecture Feb 27, 12:00—13:00, 2020.

Speaker: Yves de Cornulier (CNRS, University Lyon 1)

Place: Room -101, Math building (58)

Title: near actions

Abstract A near permutation of a set $X$ is a permutations “up to finite subset”. It can be formally defined as the germ at infinity of a homeomorphism of the one-point compactification of $X$. A near action of a group is a homomorphism into the group of near permutations of a set. We notably study realizability of near actions, namely understanding obstructions to being induced by a genuine action. These concepts can be applied to the study of the class $(M)$ of maximal abelian subgroups of $S_\omega/fin$, where $S_\omega$ is the group of permutations of the countable set $\omega$ and $fin$ is its normal subgroup of finitely supported permutations. Uncountable groups in the class $(M)$ have been studied by Shelah and Steprans (2007). We characterize countable abelian groups that occur in the class $(M)$.

• 2020 המדרשה המתמטית השנייה בנגב(*) Feb 24, 10:00—Feb 26, 16:00, 2020, שדה בוקר.

המדרשה היא כנס מתמטי המיועד לתלמידי מתמטיקה משנה ג’ והלאה, והיא תכלול ארבע סדרות של הרצאות על ידי חברי סגל מהמחלקה למתמטיקה באוניברסיטת בן-גוריון בנגב. זוהי הזדמנות להכיר חוקרים פעילים במתמטיקה, לשמוע הרצאות על תחום מחקרם באווירה ידידותית, לשוחח עימם ולשאול שאלות על מחקר מתמטי.

• Derived Categories Feb 15—16, 2020, Charles University in Prague.

A conference in celebration of the 60th Birthday of Amnon Yekutieli (Ben Gurion University) and the publication of his new book Derived Categories

• The HUJI-BGU Workshop in Arithmetic Jan 13, 10:30—16:15, 2020.

10.30 - 11.00 Welcome

11.00 - 11:50 Francesco Saettone (BGU), Analytic continuation of L-functions of characters: Tate’s thesis.

12.05 - 12.55 Zev Rosengarten (HUJI), L-functions of characters and regulators: Beilinson’s conjecture.

14.15 - 15.05 Amnon Besser (BGU), The p-adic Beilinson conjectures for number fields.

15.20 -16.00 Yotam Svoray (BGU), Polylogarithms and their geometry.

16.00 -16.15 (bonus content): Ishai Dan-Cohen (BGU) Regulators are polylogarithms.

All talks in room -101.

• האריה המתמטי: יום עיון לקהל מתמטי רחב Oct 24, 09:30—18:00, 2019, אוניברסיטת בן-גוריון בנגב (קמפוס ע"ש משפחת מרקוס), בניין 26, אולם 5.

הנכם מוזמנים ליום עיון “האריה המתמטי” באוניברסיטת בן-גוריון בנגב. יום העיון יכיל 6 הרצאות בנושאים שונים במתמטיקה, המיועדות לקהל מתמטי רחב. תכנית מפורטת של יום העיון, כולל תקצירי הרצאות ודרישות קדם לכל הרצאה, תופיע באתר האירוע. מחכים לכם!

המרצים:

• דור אלימלך

• גילי גולן

• איליה טיומקין

• אריאל ידין

• מנחם קוג’מן

• לירן רון

• Department picnic Oct 20, 11:00—16:00, 2019, Amphitheater, Ashkelon National Park.

You are cordially invited to a “beginning-of-the-year” informal picnic/potluck for the math department.
We will meet in the Amphitheater in Ashkelon National Park on Sunday, October 20th, 2019, at 11:00, take a walk and have a picnic.

A potluck is a party or a picnic where each guest brings some food to share with the others. It is recommended that every family with $N$ members brings a dish (choice of dish entirely up to you), which should be enough for at least $(N+4)$ people.

If you are interested in attending, please register here.

Here is some information about the park.

Remark: one needs to buy a ticket at the entrance to enter the park (the prices appear in the website above).

• Award ceremony in honor of Noriko Sakurai, Hillel Gauchman and Yossi Friedman(*) May 21, 12:30—16:15, 2019, Seminar room -101, Deichmann bldg. 58.

• Geometry in the Spring: a mini-conference on geometry(*) May 21, 11:00—18:00, 2019, Seminar room -101, Deichmann bldg. 58.

## Geometry in the Spring

Program:

11:00-11:30 Gathering and light refreshements

11:30-12:30 Ran Tessler (Weizmann Institute of Science), “The open arf invariant and stratifications of moduli spaces of surfaces with boundary”.

12:30-14:00 Lunch

14:00-16:15 Award ceremony in honor of Noriko Sakurai, Hillel Gauchman and Yossi Friedman.

• Honorary speaker: Sergey Fomin (University of Michigan, Ann Arbor), “Cluster Transformations”.

16:40-17:40 Eugenii Shustin (Tel Aviv University), TBA

Organizers:

• Prof. Miriam Cohen (Ben Gurion University),
• Prof. Daniel Sternheimer (Rikkyo University, Institut de Mathematiques de Bourgogne),
• Dr. Inna Entova-Aizenbud (Ben Gurion University).

The award ceremony will be held in the presence of Prof. Daniel Sternheimer and Ms. Julia Gauchman.

• School on Polish Groups(*) May 22—27, 2016, Midreshet Sde-Boker.

The School will focus on Polish Groups. General theory, examples, representations of discrete groups with Polish targets, and applications to discrete groups, geometry and dynamics. The three main courses will be:

### Mini-Courses

1. General theory of Polish groups Jullien Melleray, Christian Rosendal and Todor Tsankov.
2. Algebraic groups over Polish fields. Jean Lécureux and Bertrand Rémy.
3. Infinite dimensional Lie groups and their symmetric spaces Bruno Duchesne.
• ערב חשיפה לתארים מתקדמים Apr 12, 17:00—18:30, 2016, חדר סמינרים (101-), בניין 58.

• Algebraic Combinatorics day(*) Mar 29, 2016, Room -101, Math building (58), BGU.

In honor of Prof. Mikhail Klin, on the occasion of his retirement

• Special Seminar Jun 16, 10:00—11:00, 2015, Room -101, BGU.

Speaker: Antoine Ducros (Paris 6)

Title: Stability of Gauss valuations

Abstract:

A valued field $(k,|.|)$ is said to be stable (this terminology has no link with model-theoretic stability theory) if every finite extension $L$ of $k$ is defectless, i.e., satisfies the equality $\sum e_vf_v=[L:k]$, where $v$ goes through the set of extensions of $|.|$ to $L$, and where $e_v$ and $f_v$ are the ramification and inertia indexes of $v$. The purpose of my talk is to present a new proof (which is part of current joint reflexions with E. Hrushovski and F. Loeser) of the following classical fact (Grauert, Kuhlmann, Temkin,…) : let $(k,|.|)$ be a stable valued field, and let $(r_1,\dots,r_n)$ be elements of an ordered abelian group $G$ containing $|k^*|$. Let $|.|’$ be the $G$-valued valuation on $k(T_1,\dots,T_n)$ that sends $\sum a_I T^I$ to $\max_I |a_I|\cdot r^I$. Then $(k(T_1,\dots,T_n),|.|’)$ is stable too.

Our general strategy is purely geometric, but the proof is based upon model-theoretic tools coming from model theory (which I will first present; no knowledge of model theory will be assumed). In particular, it uses in a crucial way a geometric object defined in model-theoretic terms that Hrushovski and Loeser attach to a given $k$-variety $X$, which is called its stable completion; the only case we will have to consider is that of a curve, in which the stable completion has a very nice model-theoretic property, namely the definability, which makes it very easy to work with.

• Operator algebras and operator theory May 13, 11:10—15:30, 2015, BGU.

Joint Operator Algebras and Operator Theory Seminar, bringing together people from Ben-Gurion University, the Technion, Tel Aviv University and the University of Haifa

• Award of the Noriko Sakurai Postdoctoral Fellowship(*) May 12, 2015, BGU.

• Distinguished Lecture Series: Prof. Ilijas Farah, York University, Canada May 7—18, 2015, BGU.

• Ergodic Theorems and Applications in Probability(*) May 3—8, 2015, Eilat.

• Action NOW(*) Mar 24, 2015, BGU.

• The Moshe Flato Lecture Series 2015 Mar 12, 2015, BGU.

• Workshop on Generalized Cohomology(*) Feb 8—12, 2015, Sde Boker.

• TRATC2014 - Tropicalization, Realization, and Algebraic-Tropical Correspondence(*) Sep 28—Oct 3, 2014, Eilat.

• Award of the Noriko Sakurai Postdoctoral Fellowship(*) May 20, 2014, BGU.

• 30th European Workshop on Computational Geometry (EuroCG 2014)(*) Mar 3—5, 2014, Ein Gedi.

• Workshop on the Central Limit Theorem(*) Jul 2, 2013, Ben-Gurion University, math. dept. building.

• Interactions between Logic, Topological structures and Banach spaces theory(*) May 19—24, 2013, Eilat.

• Action Now Seminar: Mostow and Rigidity(*) May 7, 2013, Ben-Gurion University Math dept. building.

• Workshop on Algebraic, Analytic, and Tropical Geometry (AATG2013)(*) Apr 28—May 3, 2013, Kibbutz Ein Gedi.

• Mini conference in operator algebras(*) Apr 9—10, 2013, BGU.

• Spring School on Group C*-algebras(*) Mar 17—21, 2013, Sde Boker.

• Workshop on C*-algebras and Noncommutative Dynamics(*) Mar 11—14, 2013, Sde Boker.

• Dynamics on parameter spaces 2013 Jan 27—Feb 1, 2013, Sde Boker.

• Award of the Noriko Sakurai Postdoctoral Fellowship for 2013(*) Dec 25, 2012, BGU.

• The Moshe Flato Lecture Series 2011 Mar 10, 2011, BGU.

• The Moshe Flato Lecture Series 2008 Nov 27, 2008, BGU.

• The Moshe Flato Lecture Series 2007 Mar 20, 2007, BGU.

• The Moshe Flato Lecture Series 2004 Nov 25, 2004, BGU.

• The Moshe Flato Lecture Series 2002 Nov 28, 2002, BGU.

(Star) marks events partly supported by the Center for Advanced Studies in Mathematics at Ben-Gurion University