

Felix Sadyrbaev 


Leading
researcher, professor, Dr.habil.math. 
Leading
researcher, Dr.habil.math. 
Mathematical
Research Center, Department of Technology 
Laboratory
of Ordinary Differential Equations 
Institute of
Life Sciences and Technology 
Institute of Mathematics and Computer Science 
Daugavpils
University 
University of Latvia 
Parades street 1 
Raina bulvaris 29 
LV5400,
Daugavpils, Latvia 
LV1459, Riga, Latvia 
felix@latnet.lv 
felix@latnet.lv 


Research interests 


Research in
the theory of nonlinear boundary problems for ordinary differential
equations, theory of oscillations, asymmetric problems, qualitative
behavior of solutions of nonlinear differential equations, approximation
of solutions, calculus of variations, problems from applications, spectral
problems, analysis of three dimensional systems 
Education 



Dr.habil.math., University of Latvia, Riga, Latvia
Dissertation: Estimations of the number of solutions of nonlinear
boundary value problems.



Ph.D.
(Candidate of Science), Differential Equations, Belourussian State
University, Minsk
Dissertation: On some class of boundary value problems for a system of
the first order ordinary differential equations.
Advisor: Prof. Yurii
Klokov



Graduated
from Latvian State University, Faculty of Physics and Mathematics, Riga,
Latvia
Thesis: Properties of Operators in Hilbert Spaces.
Advised by Gennadiy Laptev

Teaching 


 Professor at the
Daugavpils University from 1999.


 Courses taught:
Basics of Optimization, Mathematical Modelling and Differential
Equations


 Coordinator of
Doctoral studies in Mathematics (Daugavpils University) from 2002

Research projects 



Latvian
Council of Science, Project Nr. 09.1220 Contemporary Methods of
Analyzing Dynamical Systems, Head of the project, 2009



Latvian
Council of Science, Project Nr. 05.1531 Nonlinear Boundary Value
Problems for Ordinary Differential Equations, Head of the project,
20052008.



Latvian
Council of Science, Project Nr. 01.0356 Nonlinear Boundary Value
Problems for Ordinary Differential Equations, Head of the project,
20012004.

Selected publications 



A. Kirichuka and
F. Sadyrbaev.
On boundary value
problem for equations with cubic nonlinearity and stepwise coefficient,
Differential Equations & Applications, Vol. 10, No. 4, 2018, pp.
433447.







N. Sveikate and F.
Sadyrbaev. On conversion of resonant problem to nonresonant one, Miskolc
Mathematical Notes, V. 18, N. 2, 2017, 10591071.
Miskolc Mathematical Notes



E. Brokan and F. Sadyrbaev.
Attraction in network describing systems, Proceedings of the 17th
International Conference on Computational and Mathematical Methods in
Science and Engineering (Costa Ballena, Rota, Cadiz, Spain, 48 July,
2017), 2017, 415418.
CMMSE 2017



F. Sadyrbaev.
Note on resonant problems, Proceedings of the 17th International
Conference on Computational and Mathematical Methods in Science and
Engineering (Costa Ballena, Rota, Cadiz, Spain, 48 July, 2017), 2017,
18621864.
CMMSE 2017



E. Brokan and F. Sadyrbaev.
On attractors in gene regulatory
systems. American
Institute of Physics Conference Proceedings, 2017,
V. 1809, 020010.
American Institute of Physics



A. Gritsans,
F. Sadyrbaev
and I. Yermachenko.
Dirichlet
boundary value problem for the second order asymptotically linear system. International
Journal of Differential Equations, V. 2016
(2016), Article ID 5676217, 12
pages http://dx.doi.org/10.1155/2016/5676217.
Hindawi



D. Finaskins, E. Brokan and F. Sadyrbaev.
Attracting sets in network regulatory theory. 2016 Advances in Wireless
and Optical Communications (RTUWO), 2016, 211  215.
IEEE Xplore



E. Brokan and F. Sadyrbaev.
On a differential system arising in the network control theory. Nonlinear Analysis: Modelling and Control, V.
21, N. 5,
2016, 687–701.
LANA



M. Dobkevich
and F. Sadyrbaev.
On different type solutions of boundary value problems.
Math. Modelling and Analysis,
V. 21, N. 5, 2016, 659667.
Taylor & Francis



S. Atslega, D. Finaskins
and F. Sadyrbaev.
On a planar dynamical system arising in the network control theory.
Math. Modelling and Analysis,
V. 21, N. 3, 2016, 385398.
Taylor & Francis



S. Atslega
and F. Sadyrbaev. Solutions of twopoint boundary value problems via
phaseplane analysis. E. J. Qualitative Theory of
Diff. Equ., Proc. 10'th Coll. Qualitative Theory of Diff. Equ., N. 4,
2016,
110.
EJQTDE



F. Sadyrbaev.
Oscillatory solutions of boundary value problems.
In:
Springer Proceedings in Mathematics & Statistics,
V. 164,
S. Pinelas, Z. Dosla, O. Dosly, P.E. Kloeden (Eds.),
Differential &
Difference Equations and Applications,
2016,
109117.
Springer



A. Gritsans
and F. Sadyrbaev.
The Nehari solutions and asymmetric minimizers, Proceedings
of the 10th AIMS Conference on
Dynamical Systems, Differential Equations and Applications
(Madrid, Spain, July 711, 2014),
2015,
562568.
American Institute of Mathematical Sciences.



M. Dobkevich
and F. Sadyrbaev.
Types and multiplicity
of solutions to Sturm–Liouville boundary value problem. Math. Modelling and Analysis,
V. 20, N. 1, 2015, 18.
Taylor & Francis



A. Kirichuka
and F. Sadyrbaev.
Multiple positive
solutions for the Dirichlet boundary value problems by phase plane
analysis. Abstract
and Applied Analysis,
V. 2015 (2015), Article ID 302185, 6
pages doi:10.1155/2015/302185.
Hindawi





E. Brokan and F. Sadyrbaev. Attracting Sets
in Gene Regulatory Systems. In Proceedings of International Conference on
Simulation, Modelling and Mathematical Statistics (SMMS 2015), 2015,
135138.
Link



I. Yermachenko
and F. Sadyrbaev.
On a problem for a system of two the second
order differential equations via the theory of vector fields.
Nonlinear Analysis. Modelling and Control, V. 20, N. 2, 2015,
175189.
LANA



M. Dobkevich, F.
Sadyrbaev, N. Sveikate
and
I. Yermachenko. On types of solutions of the
second order nonlinear boundary value problems. Abstract
and Applied Analysis, V. 2014 (2014), Article ID 594931,
9 pages, http://dx.doi.org/10.1155/2014/594931.
Hindawi



A. Gritsans
and F. Sadyrbaev.
Unexpected solutions of the Nehari problem. International
Journal of Analysis,
V. 2014 (2014), Article ID 467831, 5
pages doi:10.1155/2014/467831.
Hindawi
pdf



N. Sveikate
and
F. Sadyrbaev.
Quasilinearization for resonant boundaryvalue problems with mixed
boundary conditions, Nonlinear Oscillations,
Vol. 17, N. 1, 2014, 112126.
Nonlinear Oscillations
N. Sveikate
and
F. Sadyrbaev.
Quasilinearization for resonant boundaryvalue problems with mixed
boundary conditions, Journal of Mathematical Sciences, V. 205, N. 6,
2015, 832847.
Springer



I. Yermachenko
and
F. Sadyrbaev.
Quasilinearization and multiple solutions of the second order nonlinear
boundary value problem, Journal of Control Engineering and Technology,
Vol. 4, N. 1, 2014, 18.
EBSCO pdf



S. Atslega
and F. Sadyrbaev.
On periodic
solutions of Liénard type equations.
Math. Modelling and Analysis,
V. 18, N. 5, 2013, 708716.
Taylor & Francis



F. Sadyrbaev.
Twodimensional systems with
asymmetric principal part. In:
Springer Proceedings in Mathematics & Statistics,
V. 47,
S. Pinelas, M. Chipot, Z. Dosla (Eds.),
Contributions from the International Conference on Differential &
Difference Equations and Applications,
2013,
99111.
Springer





A. Gritsans
and F. Sadyrbaev.
Boundary value
problems for a supersublinear asymmetric oscillator: exact number of
solutions. International
Journal of Mathematics and Mathematical Sciences,
V. 2013 (2013), Article ID 705984, 9
pages doi:10.1155/2013/705984.
Hindawi
pdf



I. Yermachenko
and
F. Sadyrbaev.
Quasilinearization technique for ΦLaplacian type equations. International
Journal of Mathematics and Mathematical Sciences,
V. 2012 (2012), Article ID 975760, 11 pages
doi:10.1155/2012/975760.
Hindawi




 Y.
Kozmina and
F.
Sadyrbaev.
On a
maximal
number
of period
annuli,
Abstract and Applied Analysis, V. 2011 (2011), Article ID 393875,
8 pages, doi:10.1155/2011/393875.
Hindawi





F. Sadyrbaev
and
N. Sergejeva.
On a
Fučik type spectral problem for the second order nonlinear differential
equation with the integral boundary condition.
Communications in Applied Analysis,
V. 15, N.
24, 2011,
557567.
Dynamic Publishers
pdf



S. Atslega, F. Sadyrbaev. Multiple period annuli in Lienard
type equations. Applied Mathematics Letters, V. 23, N. 2, 2010,
165–169.
Elsevier


 F. Sadyrbaev. Multiplicity in
parameterdependent problems for ordinary differential equations.
Mathematical Modelling and Analysis, V. 14, N. 4, 2009, 503514.
Taylor & Francis


 M. Dobkevich and F. Sadyrbaev. Types
of solutions and approximation of solutions of second order nonlinear
boundary value problems. In: Amer. Inst. Phys. Conference Proceedings
Volume 1168, 260 – 263. Numerical Analysis and applied mathematics: International
Conference on Numerical Analysis and Applied Mathematics 2009:
Part 2, Rethymno, Crete (Greece), 18 – 22 September 2009.
American Institute of Physics



S. Atslega and F. Sadyrbaev. Multiple
positive solutions in the second order autonomous nonlinear boundary
value problems. In: American Institute of Physics Conference Proceedings
Vol. 1168, 873876. Numerical Analysis and Applied Mathematics: International
Conference on Numerical Analysis and Applied Mathematics 2009,
Part 1, Rethymno, Crete (Greece), 18 – 22 September 2009.
American Institute of Physics


 S. Atslega and F. Sadyrbaev. Multiple
solutions of the second order nonlinear Neumann BVP. Dynamics of
Continuous, Discrete and Impulsive Systems (Series A). DCDIS A
Supplement dedicated to the 6th International Conference on Differential
Equations and Dynamical Systems held in Baltimore, U.S.A., May 22  26 
Watam Press, 2009, 100–103.



A. Gritsans, F. Sadyrbaev
and N. Sergejeva. Two parameter nonlinear eigenvalue problems.
Mathematical Models in Engineering, Biology, and Medicine, Proceedings of
the International Conference on Boundary Value Problems,
American Institute of Physics Conference Proceedings, 2009,
V. 1124, 185194.
American Institute of Physics



S. Atslega and F. Sadyrbaev. Period
annuli and multiple solutions for twopoint BVP. Tatra Mountains
Mathematical Publications, V. 43, 2009, 11–23.
Link



A. Gritsans
and
F. Sadyrbaev.
Nonlinear spectra: the Neumann problem.
Mathematical Modelling and Analysis, V. 14, N. 1, 2009, 3342.
Taylor & Francis
pdf



I. Yermachenko and F. Sadyrbaev.
Multiple solutions of nonlinear boundary value problems for
twodimensional differential systems. Dynamical Systems and Differential
Equations. Proc. of the 7th AIMS International Conference (Arlington,
TX, USA, 2008), DCDS Supplement 2009, 659  668.
American Institute of Mathematical Sciences


 F. Sadyrbaev and
I. Yermachenko.
Multiple solutions of twopoint nonlinear boundary value problems.
Nonlinear Analysis: TMA, V. 71, N. 12, 2009, e176 – e185, Proc.
WCNA 2008, Orlando FL, USA, 2008.
Elsevier





A. Gritsans
and F. Sadyrbaev.
Twoparametric nonlinear eigenvalue problems. E. J. Qualitative Theory of
Diff. Equ., Proc. 8'th Coll. Qualitative Theory of Diff. Equ., N. 10, 2008,
114.
EJQTDE



F. Sadyrbaev and
I. Yermachenko. Types
of solutions and multiplicity results for twopoint nonlinear boundary
value problems. Proceedings of AIMS' Sixth International Conference on
Dyn. Systems, Diff. Equations and Applications
University of Poitiers, Poitiers,
France, June 25  28, 2006, Discrete and Continuous Dynamical Systems 
Supplement 2007, American Institute of Mathematical Sciences,
10611069.
American Institute of Mathematical Sciences


 F. Sadyrbaev
and
A. Gritsans.
Nonlinear spectra for parameter dependent ordinary differential
equations. Nonlinear Analysis: Modelling and Control, V. 12, N. 2,
2007, 253–267.
LANA
pdf


 F. Sadyrbaev.
Multiplicity of solutions for second order twopoint boundary value
problems with asymptotically asymmetric nonlinearities at resonance.
Georgian Mathematical Journal, V. 14, N. 2,
2007, 351–360.
De Gruyter



A. Gritsans
and F. Sadyrbaev. On the Nehari solutions. Proceedings of Equadiff 11, International Conference on Differential Equations. CzechoSlovak
series, Bratislava, July 2529, 2005. [Part 2] Minisymposia and
contributed talks. Comenius University Press, Bratislava, 2007, pp.
437446.
Czech
Digital Mathematics Library



A. Gritsans and F. Sadyrbaev.
Characteristic numbers of nonautonomous EmdenFowler type
equations. Mathematical Modelling and Analysis, V. 11, N. 3, 2006, p.243252.
Taylor & Francis
pdf


 F. Sadyrbaev and
I. Yermachenko.
Quasilinearization and multiple solutions of the EmdenFowler type
equation. Mathematical Modelling Analysis, V. 10, N. 1, 2005, 4150.
Taylor & Francis


 F. Sadyrbaev and
I. Yermachenko. Types
of solutions and multiplicity results for twopoint nonlinear boundary
value problems. Nonlinear Analysis: TMA, V. 63, N. 57, 2005,
e1725 – e1735.
Elsevier



A. Gritsans
and F. Sadyrbaev.
Remarks on lemniscatic functions. Acta
Universitatis Latviensis, V. 688. Mathematics, 2005, 3950.
pdf
dspace.lu.lv



A. Gritsans
and F. Sadyrbaev. The
Taylor series expansion coefficients for solutions of the EmdenFowler
type equations. Mathematical Modelling and Analysis,
V. 10, N. 1, 2005, 247256.
Taylor & Francis
pdf


 F. Sadyrbaev. Nonlinear boundary value
problems of the calculus of variations. Discrete and Continuous
Dynamical Systems  Supplement Volume, American Institute of
Mathematical Sciences, 2003, 770779.
American Institute of Mathematical Sciences


 Yu. Klokov and F. Sadyrbaev. Sharp
conditions for rapid nonlinear oscillations. Nonlinear Analysis: TMA, V.
39, N. 39, 2000, 519–533.
Elsevier


 Yu. Klokov and F. Sadyrbaev. Rapid
oscillations in sublinear problems. Funkcialaj Ekvacioj, V. 42, N. 3,
1999, 339–353.
Link


 M. Henrard and F. Sadyrbaev.
Multiplicity results for fourthorder twopoint boundary value problems
with asymmetric nonlinearities. Nonlinear Analysis: TMA, V. 33, N. 3,
1998, 281–302.
Elsevier


 F. Sadyrbaev. Multiplicity of
solutions for twopoint boundary value problems with asymptotically
asymmetric nonlinearities, Nonlinear Analysis: TMA, V. 27, N. 9, 1996,
9991012.
Elsevier


 F. Sadyrbaev. Nonlinear twopoint
fourth order boundary value problems. Rocky Mountain Journal of
Mathematics, V. 25, N. 2, 1995, 757–781.
Link

Recent Conferences and Invited Talks 



International conference of numerical analysis and applied
mathematics (ICNAAM2016), Rhodes, Greece, 2016 http://icnaam.org/







The 2015 International Conference on Simulation, Modelling and
Mathematical Statistics, Chiang Mai,
Thailand
http://www.smms2015.org/







The international
conference "Actual problems of mathematics and mathematical modeling",
dedicated to the 50th anniversary of the foundation of the Institute of
Mathematics and Mathematical Modeling of Education and Science Ministry
of the Republic of Kazakhstan, in Almaty, 2015
http://www.math.kz/conf/index.php/en/









Symposium on Differential Equations and Difference Equations,
Homburg/Saar, Germany,
2014





F. Sadyrbaev, A. Gritsans. On extension of NehariMoore
example//Book of abstracts of Conference on Differential and Difference
Equations and Applications, Jasná, Slovak Republic, June 2327, 2014, P.
49.
http://fpv.uniza.sk/cddea2014/



Symposium on Differential Equations and Difference Equations SDEDE 2013,
Bayrischzell, Germany,
2013




 International Conference on the
Theory, Methods and Applications of Nonlinear Equations,
Kingsville,
USA, 2012
Link


 Symposium on differential equations
and difference equations,
Novacella,
Italy, 2012
Link


 The Fifth International Workshop
Constructive methods for nonlinear boundary value problems,
Tokaj,
Hungary, 2012
Link


 7th European Conference on Elliptic
and Parabolic Problems,
Gaeta,
Italy, 2012
Link


 Equadiff,
Loughborough University, GB,
2011
Link


 International Conference on
Differential & Difference Equations,Ponta
Delgada, Portugal, 2011
Link


 General Assembly of International
Mathematical Union, Bangalore, India, 2010
Link


 The 8th AIMS Conference on Dynamical
Systems, Differential Equations and Applications, Dresden, Germany, 2010
Link


 Emerging Problems in Nonlinear
Analysis and Differential Equations: Advances in Theory and
Applications, Glasgow, 2010
Link


 Conference on Differential and
Difference Equations and Applications 2010 (CDDEA 2010), Rajecke Teplice,
Slovakia (invited lecturer and member of program committee)
Link


 7th ISAAC Congress, Imperial College,
London, 2009
Link


 World Congress of Nonlinear Analysts
2008, FL, USA, July 2008, Orlando, FL, USA (invited lecturer in two
special sessions)
Link


 Conference on Boundary Value Problems
Mathematical Models In Engineering, Biology And Medicine, September
1619, 2008, Santiago de Compostela, Spain (invited lecturer)
Link


 Conference on Differential and
Difference Equations and Applications, Strečno, Slovak
Republik, 2008 (invited lecturer and member of
program committee)
Link


 The 6th International Conference On
Differential Equations and Dynamical Systems, May 2226, 2008,
Baltimore,
Maryland, USA
Link


 Amer. Inst. Math. Stud. 7th
International Conference on Dyn. Systems, Diff. Equations and
Applications, University of Texas at Arlington, Texas, USA May 18
 21, 2008
Link


 Equadiff07, Vienna, Austria, 2007
Link


 Amer. Inst. Math. Stud. 6th
International Conference on Dyn. Systems, Diff. Equations and
Applications, University of Poitiers, Poitiers, France, June 25 
28, 2006
Link



The World Congress of Nonlinear Analysts
2004, FL, USA, July 2004, Orlando, FL, USA (invited lecturer in two
special sessions)
Link


 Equadiff2003, July 2226, 2003,
Hasselt, Belgium
Link


 International Congress of
Mathematicians, Bejing, China, 2002
Link


 Fourth International Conference on
Dynamical Systems and Differential Equations, May 24  27, 2002,
Wilmington, NC, USA (invited lecture)

Activities 


 Member of the Latvian
Mathematical Society


 Member of the American Mathematical
Society


