### Open Problems:

### C^m and Sobolev functions on subsets of R^n.

Whitney Extension Problems

Many of the problems posed on this webpage were initially formulated at one of the nine workshops dealing with Whitney Extension Problems and related topics:

Whitney Problems Workshops 2008 – 2016

For brief descriptions of this field of research and indications of the importance of its applications we refer to:

http://www.math.technion.ac.il/Site/events/EvntOffices/files/view/cms/104-108-96.pdf

All visitors to this page are warmly invited to submit new problems, and to inform us of any comments or updates that they may have regarding problems which already appear here.

Please send all such material to **Pavel Shvartsman** **<pshv@technion.ac.il>**

It would be very helpful if you can use latex (or some other tex format) and also include your pdf output generated by your (la)tex files.

We hope that the collection of problems and discussions about them that will appear here will significantly stimulate research in the above mentioned topics.

**Open Problems: the First Whitney Problems Workshop**

August 11-16, 2008, College of William and Mary, Williamsburg, VA, USA

The first Whitney Problems Workshop 2008- open problems

**Open Problems: the Second Whitney Problems Workshop**

August 3-8, 2009, College of William and Mary, Williamsburg, VA, USA

The second Whitney Problems Workshop 2009- open problems

**Open Problems: the Ninth Whitney Problems Workshop**

May 29 – June 2, 2016, Technion – Israel Institute of Technology, Haifa, Israel

Charles Fefferman -A few unsolved problems, June 30, 2016

**Open Problems: the Eleventh Whitney Problems Workshop**

August 13-17, 2018, Trinity College Dublin, Dublin, Ireland

Charles Fefferman – Unsolved problems