Useless information

Workshops and conferences

Diamant symposium (Arnhem, June 2014)

Arizona Winter School (Tucson, March 2014)

Winter School: Frobenius distributions on curves (Luminy, February 2014)

Diamant Symposium (Lunteren, November 2013)

Sage days: Algorithms in Arithmetic Geometry (Leiden, 22-26 July, 2013, organizer together with Peter Bruin and Maarten Derickx)

Rational Points - Geometric, Analytic and Explicit Approaches (Warwick, 27-31 May 2013)

Mathematics of Information-Theoretic Cryptography (Leiden, 13-25 May 2013)

Nederlands Mathematisch Congres (Nijmegen, 5 April 2013)

Diamant Symposium (Doorn, November 2012)

Algorithms for Complex Multiplication over Finite Fields (Oberwolfach, November 2012) (Files)

The Sardinian Summer School in Iwasawa Theory (Alghero, August 2012)

Diamant Symposium (Nunspeet, May 2012)

Nederlands Mathematisch Congres (Eindhoven, April 2012)

Arizona Winter School (Tucson, March 2012)

Winter School on Galois Theory (Luxembourg, February 2012)

Number Theory and its applications (Luminy, January 2012)

Sage Flint Days (Warwick, December 2011)

Diamant symposium (Nunspeet, November 2011)

Explicit Methods in Number Theory (Oberwolfach, July 2011)

ACAGM summer school (Leuven, July 2011)

Diamant symposium (Heeze, May 2011)

Conference on the Birch and Swinnerton-Dyer conjecture (Cambridge, May 2011)

Diamant/Eida Symposium November 2010 (Lunteren, November 2010)

Arithmetic Surfaces (Leiden, October 2010)

formal power series & algebraic combinatorics 2010 (San Francisco, August 2010)

Informal workshop on the integral closure (invited speaker, MSRI, Berkeley, July 2010)

Sage Days 23: Number Theory and Computer Algebra (Leiden, July 2010)

Obstructions (Leiden, June 2010)

Counting points on varieties (Leiden, April 2009)

Seminars

Algebra, geometry and number theory seminar (Spring 2013-, Leiden)

Intercity Seminar (Fall 2010- Netherlands)

Staff colloquium (Fall 2010-, Leiden)

Deligne's proof of the Weil conjecture for K3 surfaces (Fall 2012, Leiden)

Topics in Algebraic Geometry (Organiser, Spring 2012, Leiden)

Fourier analysis on number fields (Organiser, Fall 2011, Leiden)

Advanced Algebraic Geometry (Fall 2011, Leiden, WONDER course)

Local class field theory (Fall 2011, Leiden)

Algebra, geometry, and number theory seminar (Fall 2010-Fall 2012, Leiden)

Local fields seminar (Spring 2011, Leiden)

Topics in arithmetic geometry (Spring 2011, Leiden)

Etale cohomology seminar (Spring 2011, Leiden)

Class field theory (Fall 2010, Leiden)

Other useful files

Challenges

Here is a challenge. Consider the multiplicative function sigma: Z_{>=1} -> Z_{>=1} be defined by sigma(n)=sum_{d|n, d>=1} d. We have sigma(6)=1+2+3+6=12 for example. Challenge: find x, y in Z_{>=2} such that sigma(x^3)=y^3, where x is as large as possible.

Another challenge: find n in Z_{>=2} as large as possible and an x, y in Z_{>=2} such that sigma(x^2)=y^n.