Discrete Functions - Complexity, Essential Variables, Dominating and Distributive 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
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 .
Sl.Shtrakov,
Dominating and Annulling Sets of Variables for the Functions, Neofit Rilsky South-West University, Blagoevgrad, 1987, p.179.
R.Pavlov, Sl.Radev and Sl.Shtrakov, Mathematical Foundations of Informatics, Neofit Rilsky South-West University, 1997 (in Bulgarian), p.265.
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.
K.Chimev, Sl Shtrakov and M. Aslancky,
Mathematics ,Neofit Rilsky South-West University, 1985, (in Bulgarian), p.208.
K. Chimev and Sl.Shtrakov,
Mathematics with Informatics , Neofit Rilsky South-West University, 1988, (in Bulgarian), p.325.
D. Dureva, St. Jordanova and Sl.Shtrakov,
Exercises in Informatics , Neofit Rilsky South-West University, 1992, (in Bulgarian), p.207.
J. Denev and Sl.Shtrakov, Discrete Mathematics,
Neofit Rilsky South-West University, 1995, (in Bulgarian), p.279.
Shtrakov, Sl., Damyanov,
I., On the Classification of Boolean Functions,
Proc. of the Sixth Int. Sci. Conf. – FMNS2015,
(2015), Vol. 1, 125-130. (pdf) .
Shtrakov, Sl.,Symmetric Boolean functions with non-trivial arity gap,
Conf. Proc. 4th ICEPU,ESI , pp. 245-248, (2014).
Shtrakov, Sl., Koppitz, J.,
Congruences and reduction systems in stable varieties,
Proc. of V-th Int. Conf.
FMNS, 12-16 June 2013 , vol.1, pp. 121-128.
Shtrakov, Sl., Koppitz, J., Kovachev, D.,
On separable sets in finite functions with nontrivial
arity gap,
Proc. of IV-th Int. Conf.
FMNS, 8 - 11 June, vol.1,
2011, pp. 91-96, MR2868540.
Kovachev, D., Shtrakov, Sl.,
On Some Algebraic Structures,
Proc. of IV-th Int. Conf.
FMNS, 8 - 11 June, vol.1,
2011, pp. 44-49, MR2868533.
Shtrakov, Sl.,
Essential variables and positions in terms,
Algebra Universalis, Vol. 61, Issue 3-4, (2009), pp. 381-397, DOI 10.1007/s00012-009-0023-1, Zbl 05652295,
MR2565860 (2011a:08008),
Shtrakov, Sl.,
On the number of functions in a class of k-valued logic, (pdf)
Proc. of III-th Int. Conf.
FMNS, 3 - 7 June, 2009, pp. 22-26, MR2838710.
Shtrakov, Sl.,
On a class of functions in finite algebras, (pdf) Proc. of VI Int. Workshop on
Optimal Codes and Related Topics,
(OC-2009), June 16 - 22, 2009, Varna, BULGARIA , pp. 168-172.
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).
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).
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).
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.
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.
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.
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.
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.
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.
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.
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).
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).
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).
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.
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.
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).
Shtrakov, Sl., On the Annulator
Sets of Variables for the Functions, MTA SzTAKI
Tanulmanyok, Budapest, 182(1986), pp. 43-50, MR0929889 (89c:26025).
Shtrakov, Sl., On the
Dominant Sets of Variables for the Functions, MTA SzTAKI
Tanulmanyok, Budapest, 182(1986), pp. 37-42, MR0929888 (89c:26024).
Shtrakov, Sl., Mutually
Dominating Sets of Variables for the Functions, MTA SzTAKI
Tanulmanyok, Budapest, 182(1986), pp. 51-76, MR 0929890 (89b:26019).
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).
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.
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
VII-th Int. Conf.
FMNS,
(FMNS-2017), 14 – 18 June 2017,
Blagoevgrad, BULGARIA, Paper's title:
Minors of finite operations.
VI-th Int. Conf.
FMNS,
(FMNS-2015), 10 – 14 June 2015,
Blagoevgrad, BULGARIA, Paper's title:
On the classification of Boolean functions.
V-th Int. Conf.
FMNS,
(FMNS-2013), 12 - 16 June 2013,
Blagoevgrad, BULGARIA, Paper's title:
Congruences and reduction systems in stable varieties.
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.
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,
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,
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.
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
Seminar Coding theory , 20-23 November, 2014, V. Tarnovo, Paper's title: On the Complexity of Finite Valued Functions( Abstract, pdf )
Arbeitstagung Allgemeine Algebra
(AAA89), Institute of Algebra at Technische Universitat Dresden, February 26 - March 01, 2015, Dresden, Germany, Paper's title:
Separable sets and ODDs of finite functions,
Abstract
Conf. 125 Years of Math. and Natural Sciences at Sofia Uni. "St. Kliment Ohridski", 5-7 December, 2014, Paper's title: On the Complexity of Finite Valued FunctionsAbstract
Seminar Coding theory , 20-23 November, 2014, V. Tarnovo, Paper's title: On the Complexity of Finite Valued Functions( Abstract, pdf )
Arbeitstagung Allgemeine Algebra
( AAA87 & CYA28), Linz, Feb 7-9, 2014, Paper's title:
Stable Varieties of Semigroups,
Abstract
Arbeitstagung Allgemeine Algebra
(AAA84), Institute of Algebra at Technische Universitat Dresden, June 8-10, 2012, Paper's title:
Stable varieties of semigroups,
Abstract
IV-th Int. Conf.
FMNS,
(FMNS-2011), 8 - 11 June,
2011, Blagoevgrad, BULGARIA, Paper's title:
On separable sets in finite functions with nontrivial
arity gap.
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.
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.
Arbeitstagung Allgemeine Algebra
(AAA77), University of Potsdam, March 20-22, 2009, Paper's title:
On the essential arity gap of finite valued functions,
Abstract.
IV Congress of the Mathematicians of Republic Macedonia
(SMMK08) Struga,
19-22.10.2008, Paper's title: Essential Arity Gap of Boolean
Functions, Abstract.
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.
Arbeitstagung Allgemeine Algebra
(AAA75), Darmstadt University of Technology, November 24, 2007, Paper's title:
Multi-solid varieties,
Abstract
Arbeitstagung Allgemeine Algebra
(AAA69), University of Potsdam,
Germany,
March 18-20, 2005, Paper's title:
Coloured Terms and Multihyper-substitutions ,
Abstract
Arbeitstagung Allgemeine Algebra
(AAA68), University of Dresden,
Germany,
June, 10-13,2004, Paper's title:
Recursive Coloration of Trees,
Abstract
Arbeitstagung Allgemeine Algebra
(AAA67), University of Potsdam,
Germany,
March 26-28, 2004, Paper's title:
On the colouration of terms,
Abstract
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)
Arbeitstagung Allgemeine Algebra
(AAA63)
Kaiserslautern ,Germany, 22-24.02.2002
Paper's title: Sequences of
Hypersubstitutions and Coloring
(Abstract)
International Conference on Galois Connections
(ICGC2001)
,
Potsdam, Germany, 15-18.03.2001 Paper's title:
Tree Automata and Essential
Subtrees(Abstract)
Arbeitstagung Allgemeine Algebra
(AAA61)
Darmstadt,Germany, 02-04.02.2001.
Paper's title: Algorithms for Depth and Size of Hypersubstitutions
Arbeitstagung Allgemeine Algebra
(AAA60)
Dresden,Germany 22-25.06.2000
Paper's title: Tree Automata and Essential Input Variables
(Abstract)
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
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
TEMPUS JEP 1728 "University Network for Cooperation and Development of Artificial Intelligence
and Modern Information Technologies Education" , 1992-1994
TEMPUS SJEP 7272 "University Network for Information Technologies Education in Economic, Social
and Political Sciences, Business and Humanities", 1994-1997
TEMPUS CME 01006 "Intra- and Inter-university Services Support", 1995
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
Annual projects for co-operation with DAAD (Germany) and University of Potsdam- since 1993
Moscow State University (3 month-specialization) 1984
Bulgarian Academy of Science- 1991-1999
Computer Science Department of Hungarian Academy of Science, (specialization) 1993
International Training Center at Jerusalem,Israel "Education for Science and Technology",
(seminar, 1 month) 1998
"Discrete Mathematics and Applications", part
of Stability pact, founded by Alexander von Humboltd foundation, 2001,2004