Personal data

• Address:
  Iv.Mihailov-Str.66
  Faculty of Mathematics and Natural Sciences
  Neofit Rilsky South-West University
  2700 Blagoewgrad, Bulgaria
• phone: (+359)(+73) 88 91 31(office)
• e-mail: shtrakov@swu.bg
• URL: http://home.swu.bg/shtrakov/

Education, scientific degrees

• Doctor of Science (Math), Sofia, 2008
• Ph.D. on Discrete Mathematics, University of Sofia, 1984-1987
• M.Sc. on Algebra, University of Sofia, 1977-1978
• B.Sc. on Mathematics, University of Sofia, 1973-1977
• Secondary school, Dupnica, 1968-1971

Membership

• Union of Bulgarian Mathematicians (UBM)
• American Mathematical Society (AMS)

Research interests

• Discrete Functions - Complexity, Essential Variables, Dominating and Annulling Sets;
• Algorithms for Classifying in Algebras;
• Essential Arity Gap of Finite Valued Functions;
• Tree Automata Techniques and Applications;
• Hypersubstitutions and Colored Trees;
• Universal Algebra, Identities and Varieties;
• Groups Acting on Algebras of Functions;
• Combinatorial Problems in Finite Algebras.

Teaching and administrative experience

• Dean of the Faculty of Natural Sciences and Mathematics, 1991-2003,
  Neofit Rilsky South-West University, Blagoevgrad
• Head of the Department of Computer Science, 1990-1999,
  Neofit Rilsky South-West University, Blagoevgrad
• Associate Professor of Computer Science, since 1988
  Neofit Rilsky South-West University, Blagoevgrad
• Assistant Professor of Mathematics, 1979-1988
  Neofit Rilsky South-West University, Blagoevgrad
• Teacher of Mathematics in Secondary School, 1978-1979
  Dolna Dikania

Courses of Lectures

• In Neofit Rilsky South-West University, Blagoevgrad
• Discrete Mathematics (for students in Mathematics and Computer Science) since 1990
• Linear Algebra and Geometry (for students in Physics) 1987-1989
• Mathematical Analysis (for students in Physics) 1987-1989
• Applied Mathematics (for students in Physics) 1988-1991
• Statistics (for students in Economics) 1993-1997
• Algebra (Groups, Rings, Fields, Polynomials) (for students in Math.)1991-1998
• Informatics (for students in Economics) since 1987
• Programming (in PASCAL and C++) (for students in Mathematics) 1989-2000
• In Burgas Free University, Burgas.
  • Discrete Mathematics and Probability (for students in Mathematics) 1995-1999
• In Greenwich University- London, UK
  • Numerical Methods - spring semester, 1999
  • Coding and Cryptography - spring semester, 1999
• In New Bulgarian University, Sofia.
  • Discrete and Algorithmic Mathematics (for students in Computer Science) 2005-2006
  • Discrete Mathematics (for students in Computer Science) 2005-2006

Publications
Monographs, Dissertation, Thesis

1. Sl.Shtrakov, On the Dominating and Annuling Sets of Variables for Functions, Sofia, SNS in Mathematics, 24.06. 1986 (in Bulgarian), (Ph.D. Thesis), p.156 .
2. Sl.Shtrakov, Dominating and Annulling Sets of Variables for the Functions, Neofit Rilsky South-West University, Blagoevgrad, 1987, p.179.
3. R.Pavlov, Sl.Radev and Sl.Shtrakov, Mathematical Foundations of Informatics, Neofit Rilsky South-West University, 1997 (in Bulgarian), p.265.
4. Sl.Shtrakov, Separability in Algebras of Functions, Terms and Tree Automata, Sofia, SNS in Informatics and Math. Modeling, 17.12. 2007 (in Bulgarian), (Dissertation for Dr.Sc.) Summary (Contents) (in Bulgarian), p.244.

Text-books

1. K.Chimev, D. Ananieva, Al. Todorov, I. Giudzhenov, M. Aslancky and Sl.Shtrakov, Exercises in Mathematics ,Neofit Rilsky South-West University, 1980, (in Bulgarian), p.483.
2. K.Chimev, Sl Shtrakov and M. Aslancky, Mathematics ,Neofit Rilsky South-West University, 1985, (in Bulgarian), p.208.
3. K. Chimev and Sl.Shtrakov, Mathematics with Informatics , Neofit Rilsky South-West University, 1988, (in Bulgarian), p.325.
4. D. Dureva, St. Jordanova and Sl.Shtrakov, Exercises in Informatics , Neofit Rilsky South-West University, 1992, (in Bulgarian), p.207.
5. J. Denev and Sl.Shtrakov, Discrete Mathematics, Neofit Rilsky South-West University, 1995, (in Bulgarian), p.279.
6. Sl.Shtrakov, K. Yordjev, M. Todorova, Exercises in Discrete Mathematics Neofit Rilsky South-West University, 2005, (in Bulgarian), p.180.

Actual research articles

1. Shtrakov, Sl., Koppitz, J., Symmetric functions with non-trivial arity gap, Journal of Algebra and Discrete Mathematics, 2010, preprint (submitted), (arXiv:1009.4828)
2. Shtrakov, Sl., Koppitz, J., On finite functions with non-trivial arity gap, Discussiones Mathematicae - General Algebra and Applications, vol.30, (2010), pp. 217-245 (arxiv:0810.2279).
3. Shtrakov, Sl., Essential variables and positions in terms, Algebra Universalis, Vol. 61, No. 3-4, (2009), pp. 381-397, DOI 10.1007/s00012-009-0023-1, Zbl 05652295, (arxiv:0802.2385).
4. Shtrakov, Sl., On the number of functions in a class of k-valued logic, (pdf) Proc. of III-rd International Conference, South-West University, Faculty of Mathematics and Natural Sciences, Blagoevgrad, Bulgaria, 3 - 7 June, 2009, pp. 22-26.
5. Shtrakov, Sl., On a class of functions in finite algebras, (pdf) Proc. of Sixth International Workshop on Optimal Codes and Related Topics, (OC-2009), June 16 - 22, 2009, Varna, BULGARIA , pp. 168-172.
6. Shtrakov, Sl., Essential arity gap of Boolean functions, (Abstract, pdf) , Journal of Computing, Serdica vol.2, No. 3, 2008, pp. 249-266, Zbl 1170.06005, MR2489631 (2010c:06023) (arXiv:0808.3892).
7. Shtrakov, Sl., Multi-Solid Varieties and Mh-transducers, Journal of Algebra and Discrete Mathematics, (Abstract, pdf), No 3 (2007) , pp. 113-137, Zbl 1164.08310, MR2423702, (2009b:08009) (arXiv:math/0702454).
8. Denecke, K., Koppitz, J., Shtrakov, Sl., Multi-Hypersubstitutions and Colored Solid Varieties, (Abstract, pdf), Journal of Algebra and Computation, Vol. 16, No. 4 (2006), pp. 797-815 Zbl 1106.08003, MR 2258839 (2007f:08003), (arXiv:0811.4764).
9. Koppitz, J., Shtrakov, Sl., On mappings of terms determined by hypersubstitutions, (Abstract, pdf) , Journal of Algebra and Discrete Mathematics, No 3, Jul./Sep. (2005), pp. 18-29, Zbl 1093.20030, MR 2237892 (2007i:20094), (arXiv:0811.3325).
10. Shtrakov, Sl., Denecke, K., Essential Variables and Separable Sets in Universal Algebra, ( Abstract, pdf ), Multiple-Valued Logic, An International Journal, 2002, vol. 8(2), pp. 165-181, Zbl 1022.08002, MR1957651 (2003k:08005), (arXiv:0812.1979).
11. Damyanov, I., Shtrakov, Sl., Essential inputs and minimal tree automata, (Abstract, pdf), Discrete mathematics and applications (Bansko, 2001), pp. 77-85, Res. Math. Comput. Sci., 6, South-West Univ., Blagoevgrad, 2002, Zbl 1024.68069, MR 1 928 414 (2003h:68089), (arXiv:cs/0702136).
12. Shtrakov, Sl., Tree automata and essential subtrees, (Abstract, pdf), Discrete mathematics and applications (Bansko, 2001), pp. 51-59, Res. Math. Comput. Sci., 6, South-West Univ., Blagoevgrad, 2002, Zbl 1021.68059, MR 1 928 411 (2003i:68092), (arXiv:cs/0702137).
13. Denecke, K., Koppitz, J., Shtrakov, Sl., The depth of a hypersubstitution, (Abstract, pdf), Journal of Automata, Languages and Combinatorics, 6 (2001), No. 3, pp. 253-262, MR1879769 (2003b:08001), (arXiv:0811.4762).
14. Shtrakov, Sl., Tree automata and essential input variables, (Abstract, pdf), Contributions to general algebra, 13 (Velké Karlovice, 1999/Dresden, 2000), pp. 309-319, Heyn, Klagenfurt, 2001, MR1854595 (2002j:68058), Zbl 0986.68071, (arXiv:cs/0702129).
15. Shtrakov, Sl., Shtrakov, Vl., Tree Automata and Separable Sets of Input Variables, ( Abstract, pdf), IC, FILOMAT 2001, University of Nis, Yugoslavia , 2001, pp. 61-69, Zbl 1053.68062, MR 2105097 (2005g:68106), (arXiv:cs/0702123).
16. Shtrakov, Sl., Separable sets of variables and $s$-systems, Discrete mathematics and applications (Blagoevgrad, 1994), ed. Sl.Shtrakov and I. Mirchev, pp. 61-67, Res. Math., 5, Neofit Rilsky South-West University, Blagoevgrad, 1995, MR1331850 (96c:04002).
17. Shtrakov, Sl., On the Mutually Dominating and Connected Sets of Variables, Discrete mathematics and applications, (1993), ed. K.Chimev and Sl.Shtrakov, Neofit Rilsky South-West University, Blagoevgrad, pp.64-72.
18. Shtrakov, Sl., On some transformation groups in $k$-valued logic, General algebra and applications (Potsdam, 1992), pp. 225-237, Res. Exp. Math., 20, Heldermann, Berlin, 1993, MR1209902 (94b:03048), Zbl 0793.03023.
19. Shtrakov, Sl., Separability and Dominance of Sets of Variables for the Functions, Neofit Rilsky South-West University, Year-book (Math.), Blagoevgrad, vol. 7, book 2, 1990, pp.63-72.
20. Mirtchev, Iv., Shtrakov, Sl., Strongly dominating sets of variables, Közl. MTA Számitástech. Automat. Kutató Int. Budapest, 1988, no. 39, pp. 121-129, MR0987344 (90a:26022), Zbl 0698.04004.
21. Shtrakov, Sl., Extremal subsets and coverings of the sets of variables for the functions, Közl. MTA Számitástech. Automat. Kutató Int. Budapest, 1988, no. 38, pp. 27-35, MR0963402 (89g:04003), Zbl 0651.04002.
22. Chimev, K. N., Giudjenov, I. D., Shtrakov, Sl. Vl., Aslanski, M. S., Separable and dominating sets of variables for the functions, Mathematics and mathematical education (in Bulgarian) (Sunny Beach, 1987), pp. 61-71, Bulgar. Acad. Sci., Sofia, 1987, MR 949 933,   Zbl 0641.94024.
23. Shtrakov, Sl., Inseparable Sets and Their s-Subsets of Variables, Neofit Rilsky South-West University, Year-book (Math.), Blagoevgrad, vol. 5, book 1, 1988, pp.25-49.
24. Shtrakov, Sl., On the dominating sets of variables for the functions, Mathematics and mathematical education (in Bulgarian), (Sunny Beach, 1987), pp. 563-568, Bulgar. Acad. Sci., Sofia, 1987, MR0949977 (89e:04007).
25. Shtrakov, Sl., Dominant sets of variables of functions and algorithms for obtaining them. (in Bulgarian) University Annual, Applied Mathematics, Sofia, 22 no. 1, pp. 173-180 (1987), MR0948553 (89e:04006).
26. Chimev, K. N., Shtrakov, Sl., Generalized orders of variables and $\epsilon$-equivalence in some algebras of functions, (in Bulgarian), University Annual, Applied Mathematics, Sofia, 22 no. 1, pp. 151-158 (1987), MR0948550 (89e:04003).
27. Shtrakov, Sl., On the separable and annuling sets of variables for the functions, Közl. MTA Számitástech. Automat. Kutató Int. Budapest, 35, pp. 147-168 (1986), MR0882311 (88e:04002), Zbl 0611.04001.
28. Shtrakov, Sl., On the C-separable and dominant sets of variables of functions, Mathematics and education in mathematics, Proc. 15th Spring Conf., Sunny Beach/Bulg. 1986, pp. 345-350 (1986), Zbl 0604.94010.
29. Chimev, K., Shtrakov, Sl., On the dominant sets and separable pairs of essential variables of functions, University Annual, Applied Mathematics, Sofia, 21, no. 3, 145-151 (1986), (in Bulgarian). MR0906951 (88h:04003).
30. Shtrakov, Sl., On the Annulator Sets of Variables for the Functions, MTA SzTAKI Tanulmanyok, Budapest, 182(1986), pp. 43-50, MR0929889 (89c:26025).
31. Shtrakov, Sl., On the Dominant Sets of Variables for the Functions, MTA SzTAKI Tanulmanyok, Budapest, 182(1986), pp. 37-42, MR0929888 (89c:26024).
32. Shtrakov, Sl., Mutually Dominating Sets of Variables for the Functions, MTA SzTAKI Tanulmanyok, Budapest, 182(1986), pp. 51-76, MR 0929890 (89b:26019).
33. Shtrakov, Sl., On the $c$-separable and dominant sets of variables for the functions, Közl. MTA Számitástech. Automat. Kutató Int. Budapest, No. 32, (1985), pp. 155-161, MR0810747 (87e:06032).
34. Shtrakov, Sl., On some transformations in the $K$-valued logic, Mathematics and mathematical education (Sunny Beach, 1985), pp. 305-309, Bulgarian Academy of Science, Sofia, 1985, MR0805369 (87c:03045), Zbl 0592.03012.
35. Shtrakov, Sl., The Annulling Sets of Essential Variables of the Functions, Neofit Rilsky South-West University, Year-book (Math.), vol. 1, book 1, 1984, pp. 91-97.

Conferences Organizing or Editing of the Proceedings

1. 7th International Conference on Discrete mathematics and applications (ICDMA 7) held in Bansko, June 17- 20, 2004, Edited by Sl. Shtrakov and K. Denecke. Research in Mathematics and Computer Sciences, 7. South-West University, Blagoevgrad, 2005, Abstracts ISBN: 954-680-363-4, MR2181448.
   
2. Invited session "Universal Algebra, Tree Automata and XML-Data" at the 7th World Multi Conference on Systemics, Cybernetics and Informatics (SCI 2003). July 27 - 30, 2003, Orlando, Florida, USA Sheraton World
3. 6th International Conference on Discrete mathematics and applications (ICDMA 6) held in Bansko, August 31-September 2, 2001. Edited by Sl. Shtrakov and K. Denecke. Research in Mathematics and Computer Sciences, 6. South-West University, Blagoevgrad, 2002. viii+218 pp. ISBN: 954-680-219-0 Abstracts
   MR 1928405,
4. International Conference on Discrete mathematics and applications (ICDMA 5) held in Blagoevgrad, September 12-16, 1994. Edited by Sl. Shtrakov and Iv. Mirchev . Research in Mathematics, 5. Neofit Rilsky South-West University, Blagoevgrad, 1995. 256 pp. ISBN: 954-680-001-5
   MR 95m:00019,
5. International Conference on Discrete mathematics and applications (ICDMA 3) held in Blagoevgrad, September 08-11, 1992. Edited by K. Chimev and Sl. Shtrakov . Research in Mathematics, 3. Neofit Rilsky South-West University, Blagoevgrad, 1993. 151 pp.
6. International Conference on Discrete mathematics and applications (ICDMA 2) held in Predela, June 05-10, 1990. Edited by Sl. Shtrakov. Research in Mathematics, 2. Neofit Rilsky South-West University, Blagoevgrad, 1990. 105 pp.

Participating in Conferences with Presentations

1. Sixth International Workshop on Optimal Codes and Related Topics, (OC-2009), June 16 - 22, 2009, Varna, BULGARIA , Paper's title: On a class of functions in finite algebras, Abstract.
2. Third International Scientific Conference (FMNS-2009), 03 - 07.06.2009, Blagoevgrad, BULGARIA, Paper's title: On the number of functions in a class of $k$-valued logic, Abstract.
3. Arbeitstagung Allgemeine Algebra (AAA77), University of Potsdam, March 20-22, 2009, Paper's title: On the essential arity gap of finite valued functions, Abstract.
4. IV Congress of the Mathematicians of Republic Macedonia (SMMK08) Struga, 19-22.10.2008, Paper's title: Essential Arity Gap of Boolean Functions, Abstract.
5. 11-th International Workshop on Algebraic and Combinatorial Coding Theory ACCT08, June 16-22, 2008, Pamporovo, Paper's title: Essential Arity Gap of Finite Valued Functions.
6. Arbeitstagung Allgemeine Algebra (AAA75), Darmstadt University of Technology, November 2–4, 2007, Paper's title: Multi-solid varieties, Abstract
7. Arbeitstagung Allgemeine Algebra (AAA69), University of Potsdam, Germany, March 18-20, 2005, Paper's title: Coloured Terms and Multihyper-substitutions , Abstract
8. Arbeitstagung Allgemeine Algebra (AAA68), University of Dresden, Germany, June, 10-13,2004, Paper's title: Recursive Coloration of Trees, Abstract
9. Arbeitstagung Allgemeine Algebra (AAA67), University of Potsdam, Germany, March 26-28, 2004, Paper's title: On the colouration of terms, Abstract
10. Arbeitstagung Allgemeine Algebra (AAA65) Potsdam ,Germany,  20-23.03.2003   Paper's title: All Input Variables Are Essential for Almost All Trees and Logical Tree Automata (Abstract)
11. Arbeitstagung Allgemeine Algebra (AAA63) Kaiserslautern ,Germany,  22-24.02.2002   Paper's title: Sequences of Hypersubstitutions and Coloring (Abstract)
12. International Conference on Galois Connections (ICGC2001) , Potsdam, Germany,  15-18.03.2001 Paper's title:  Tree Automata and Essential Subtrees(Abstract)
13. Arbeitstagung Allgemeine Algebra (AAA61) Darmstadt,Germany,  02-04.02.2001.  Paper's title: Algorithms for Depth and Size of Hypersubstitutions
14. International Conference Filomat 2001, Nis, Yugoslavia , 26.08-30.08.2001 Paper's title:  Tree Automata and Computational Complexity.
15. Arbeitstagung Allgemeine Algebra (AAA60) Dresden,Germany  22-25.06.2000  Paper's title: Tree Automata and Essential Input Variables (Abstract)
16. Arbeitstagung Allgemeine Algebra (on occasion of the 70th birthday of H.-J.Hoehnke) (AAA 52) University of Potsdam, Campus Am Neuen Palais, Germany 03-06.06.1996.  Paper's title: Dominating and Connected Sets of Variables
17. Arbeitstagung Allgemeine Algebra (AAA43) University of Potsdam,Campus Golm,Germany,  31.01.1993-02.02.1993 Paper's title: On Some Transformation Groups in k-Valued Logic.

Coordinator from the South-West University of Projects and Cooperation

University Study Projects

1. TEMPUS JEP 1728 "University Network for Cooperation and Development of Artificial Intelligence and Modern Information Technologies Education" , 1992-1994
2. TEMPUS SJEP 7272 "University Network for Information Technologies Education in Economic, Social and Political Sciences, Business and Humanities", 1994-1997
3. TEMPUS CME 01006 "Intra- and Inter-university Services Support", 1995
4. TEMPUS SJEP 11087 " Modular Education in Mathematics and Informatics" , 1996-1999

Scientific Projects

1. Centre of Excellence for Applications of Mathematics, Stability pact (via DAAD) project with Universities of Duisburg, Skopie, Cluj, Novi Sad, Nish, Plovdiv and Sofia, 2001-2009
2. Annual projects for co-operation with DAAD (Germany) and University of Potsdam- since 1993
3. Moscow State University (3 month-specialization) 1984
4. Bulgarian Academy of Science- 1991-1999
5. Computer Science Department of Hungarian Academy of Science, (specialization) 1993
6. International Training Center at Jerusalem,Israel "Education for Science and Technology", (seminar, 1 month) 1998
7. "Discrete Mathematics and Applications", part of Stability pact, founded by Alexander von Humboltd foundation, 2001,2004

Hobby

• Reading
• History
• Sport - Chess, Football
• Tourism

Legend

• MR - Mathematical Reviews
• Zbl - Zentralblatt MATH