Picture of Steffen Lempp

Office Address

Department of Mathematics
University of Wisconsin
480 Lincoln Drive
Madison, WI 53706-1325


Skype: steffen.lempp
Office phone: +1-608-263-1975 (not being used for now)
Department phone: +1-608-263-3054
Fax: +1-608-263-8891
(Please note that I do not regularly monitor the answering machine of my office phone, so if you want to reach me quickly, email works best.)

Office and office hours during semester

Office: 525 Van Vleck Hall (not being used during the pandemic)
Office hours: by Google meet only.
MWF 10-11am for Math 211, MF 1pm-1:30pm for Math 770, or by appointment.
(Email me ("> to request a Google meet.
You will need only a browser open, and I will send you a code to log in.
No face-to-face meetings for the time being!)

Courses taught in fall 2020

All classes this fall will be taught on line; no face-to-face meetings!

Course taught in spring 2021

This class will be taught on line; no face-to-face meetings!

Logic seminars around the Midwest

Conferences I plan to attend

On-line logic seminars worldwide

Other conferences of interest to logicians

Web pages from past conferences I have co-organized

Travel Information on Madison and the University of Wisconsin

Picture of Van Vleck Hall

Travel information for foreign visitors to the UW math department

IMPORTANT NOTE FOR VISA WAIVER TRAVELERS: You will now need to pre-register at least three days before arrival in the United States at the ESTA web site. ESTA now charges US$14 for this! Be sure to bring along your ESTA receipt as well as a copy of the green form you fill out during your travel to the U.S. if we will pay you for any expenses, we cannot pay you without this receipt and this green form!

NEW: Starting in September 2016, Canada now also has a similar travel authorization system to ESTA called eTA, which is required even if you just have a flight layover in Canada. eTA is valid for five years (or until your passport expires), usually takes only minutes to complete, and costs CAN$ 7.

Since September 11, 2001, visa regulations for foreign visitors have become much stricter. In particular, the "wrong kind" of visa can result in

In particular, a tourist visa B-2 (or tourist visa waiver WT) allows us to pay you for at most nine days of travel expenses; so you should always try to get a business visa B-1 (or business visa waiver WB) whenever you come for shorter visits over nine days. If you are eligible for a visa waiver (check here for the list of eligible countries, note that if you have traveled to Iran, Iraq, Libya, Somalia, Sudan, Syria, or Yemen, you are not eligible for a visa waiver and need to apply for a regular visa), then you should make sure at the border that you show the immigration official an official letter of invitation from us and that the immigration official circles "WB" on your entry stamp in your passport. Do not leave from this official until your passport stamp is correct, since this cannot be changed later on!

Also note that if your travel to and from the U.S. is supported by a federal grant (such as an NSF grant), then you need to abide by the Fly America Act (see Article 14c+d in this document), which generally requires the use of U.S. carriers to the closest foreign airport served by a U.S. airline. However, several Open Skies Agreements have recently been signed (currently with the European Union, Switzerland, Australia and Japan), which allow use of these countries' airlines as well. Note, however, that what matters for the Fly America Act is the airline listed on your ticket and not the airline actually flying the plane, which can become tricky with all the code sharing! Here are some useful links:

State Department web sites on U.S. visas

Related information for visitors

My research interests

My primary research interest is computability in its various aspects, both in classical computability theory, in particular degree structures, and in applications of computability to model theory, algebra, proof theory, and computer science.

Some particular problems I am currently working on include

My curriculum vitae, bibliography, and mathematical genealogy

My publications on line

Lobachevskii Journal of Mathematics

In March 2015, I became one of the editors for this journal established by the Russian Academy of Sciences and Kazan State University and distributed by Springer-Verlag.

Submissions in mathematical logic, especially in computability theory and its applications, can be sent directly to me by email at"> Before submission, be sure to consult the instructions on how to prepare your manuscript.

Professional Organizations

Research databases of interest to logicians

Job openings I happen to hear of

Information on special Ph. D. and Master's Programs in Logic

Summer Schools in Logic for Undergraduate and Graduate Students

ASL Committee on Translations

Our committee invites suggestions for books, monographs, and papers to be translated into and from English. The criteria for translation are high quality of material presented, lack of an equivalent text in the language to be translated into, and marketability of the translated text. We invite especially submissions from authors and from the advisors of theses.

Please send your suggestions to one of the committee members: Alex Berenstein (University of the Andes, Bogotá, Colombia), Zhaokuan Hao (Fudan University, Shanghai, China), Sergei Odintsov (Sobolev Institute of Mathematics and Novosibirsk State University, Russia), Ram Ramanujam (Institute of Mathematical Sciences, Chennai, India), Kazuyuki Tanaka (Tohoku University, Sendai, Japan), or me (">

Information for Russian-speaking Logicians

The ASL Committee on Translations offers a
Russian translation of Bruno Poizat's
"Cours de théorie des modèles" ("A Course in Model Theory")
for free download.

I also administer the program of the Association for Symbolic Logic (ASL) offering

free subscriptions to
the Journal of Symbolic Logic and the Bulletin of Symbolic Logic
to university libraries in the former Warsaw Pact countries
which are on the World Bank List of developing economies.

For more information about this program, click here for information in English or in Russian.

Home pages of some other logicians

(If the last name of a person is ambiguous (in my humbl;e opinion), then it is listed below in all capital letters below.)
Prepared by Steffen Lempp (">