About me

Lukas Fleischer

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lfleischer@lfos.de

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Starting in March 2020, I will be working as a software engineer within the Google Cloud AI organization at the Google office in Kitchener-Waterloo.

From August 2015 to April 2019, I was a research assistant in the Institute for Formal Methods in Computer Science at the University of Stuttgart. From May 2019 to December 2019, I was a postdoctoral researcher in the Cheriton School of Computer Science at the University of Waterloo, working with Jeffrey Shallit. My primary research areas are automata theory, formal languages, semigroup theory, algorithms, computational complexity and formal verification. A list of my publications can be found here and on DBLP.

I am an Arch Linux Trusted User and Developer, and I actively contribute to several other open source projects. Please scroll down for a (not necessarily complete) list.

Some random personal facts: I was born on March 6th, 1990 in Bietigheim-Bissingen and I am currently living in Waterloo, ON. Outside computer science, I am interested in investing, entrepreneurship, sustainability, health, and fitness.

Places I have visited in the past include Australia, Austria, Canada (Ontario, Quebec), Cape Verde, Denmark, the Dominican Republic, France, Germany, Hong Kong, Hungary, Indonesia (Bali), Italy, Japan, Mexico, Portugal, Romania, Russia, Singapore, Spain, Switzerland, Thailand, Turkey, the United Arab Emirates (Dubai), the United Kingdom (England), and the United States of America (California, Illinois, Kansas). Click here for a colored map (updated in February 2020).

Short CV

05/2019-12/2019 Postdoctoral Fellow, School of Computer Science, University of Waterloo
02/2019-04/2019 Research Assistant, FMI, University of Stuttgart
08/2015-02/2019 Ph.D. Computer Science, FMI, University of Stuttgart
04/2015-07/2015 Teaching Assistant, University of Stuttgart
10/2013-05/2015 M.Sc. Computer Science, University of Stuttgart
10/2010-11/2013 B.Sc. Computer Science, University of Stuttgart
2000-2009 High School, Gymnasien im Ellental, Bietigheim-Bissingen
1996-2000 Elementary School, Grundschule im Sand, Bietigheim-Bissingen

Publications

Conference Articles

  1. Lukas Fleischer and Manfred Kufleitner. Testing Simon's congruence. MFCS 2018. 
  2. Lukas Fleischer. The Intersection Problem for Finite Semigroups. DLT 2018. 
  3. Lukas Fleischer. On the Complexity of the Cayley Semigroup Membership Problem. CCC 2018. 
  4. Lukas Fleischer and Manfred Kufleitner. The Intersection Problem for Finite Monoids. STACS 2018. 
  5. Volker Diekert and Lukas Fleischer. Church-Rosser Systems, Codes with Bounded Synchronization Delay and Local Rees Extensions. WORDS 2017. 
  6. Lukas Fleischer and Manfred Kufleitner. Green's Relations in Finite Transformation Semigroups. CSR 2017. 
  7. Lukas Fleischer and Manfred Kufleitner. Operations on Weakly Recognizing Morphisms. DCFS 2016. 
  8. Lukas Fleischer and Manfred Kufleitner. Efficient Algorithms for Morphisms over Omega-Regular Languages. FSTTCS 2015. 
  9. Lukas Fleischer, Manfred Kufleitner and Alexander Lauser. Block Products and Nesting Negations in FO2. CSR 2014. 

Journal Articles

  1. Lukas Fleischer and Trevor Jack. The Complexity of Properties of Transformation Semigroups. International Journal of Algebra and Computation. World Scientific, 2019. 
  2. Lukas Fleischer and Manfred Kufleitner. The Complexity of Operations on Weakly Recognizing Morphisms. RAIRO-Theor. Inf. Appl., volume 53, number 1-2, pp 1–17. EDP Sciences, 2018. 
  3. Lukas Fleischer and Manfred Kufleitner. Green's Relations in Deterministic Finite Automata. Theory of Computing Systems, volume 63, issue 4, pp 666–687. Springer, 2018. 
  4. Lukas Fleischer, Manfred Kufleitner and Alexander Lauser. The Half-Levels of the FO2 Alternation Hierarchy. Theory of Computing Systems, volume 61, issue 2, pp 352–370. Springer, 2017. 

Unpublished Papers

  1. Lukas Fleischer and Jeffrey Shallit. The State Complexity of Lexicographically Smallest Words and Computing Successors. Technical report, 2019.
  2. Lukas Fleischer, Samin Riasat, and Jeffrey Shallit. New Bounds on Antipowers in Binary Words. Technical report, 2019. 
  3. Lukas Fleischer and Jeffrey Shallit. Words With Few Palindromes, Revisited. Technical report, 2019. 
  4. Lukas Fleischer and Jeffrey Shallit. Words Avoiding Reversed Factors, Revisited. Technical report, 2019. 
  5. Lukas Fleischer. Algorithms and Complexity Results for Finite Semigroups. PhD thesis, 2019. 
  6. Lukas Fleischer. Efficient Membership Testing for Pseudovarieties of Finite Semigroups. Technical report, 2018. 

Open Source Projects

Arch Linux

As an Arch Linux Trusted User and Developer, I am leading the development of the Arch User Repository web interface and maintaining the Arch Linux projects page as well as roughly 150 packages.

I am the author of aurdupes, a Python script that can be used to find duplicate packages in pacman databases and the Arch User Repository.

calcurse

I am the current maintainer of calcurse, a powerful command-line based calendar program.

jpeg-archive

In late 2017, I started co-maintaining jpeg-archive, a utility to compress JPEG images for long-term storage without sacrificing perceived visual quality.

Deprecated Projects

cdlib-eject was a lightweight C program to control Dacal CD Library II devices.

Open Source Contributions

I occasionally contribute to other projects. Projects I have contributed to in the past include