Գրիգոր Բարսեղյան
Current position
Առաջատար գիտաշխատող, ՀՀ ԳԱԱ Մաթեմատիկայի ինստիտուտ
Հասցե
24/5 Բաղրամյան պող., 0019 Երևան, Հայաստան
Ծննդյան օր
1 մայիս, 1949
Հեռ․
00374 94 488353
Հետաքրքրությունների ոլորտ:
- Complex Analysis (particularly Nevanlinna value distribution theory and Geometric functions theory
- Differential geometry particularly Minimal surfaces
- Algebraic Geometry
- Bio and econ.mathematics
- real and complex differential equations.
Education and Degrees
University/Institute:
Yerevan State University
1966 to 1971
Degree:
Doctor Phys-Math sciences (1984)
For achievements, see the "Other" section below.
Professional Experience
Company Name:
Institute of Mathematics
Title:
Main researcher (since 2021)
Memberships
Fellowships, Membership of Professional Societies:
Real Member (academician) of the Russian Academy of Natural Sciences, since 1999.
Member of the ISAAC (International Society for Analysis its Application and Computation); was Board Member in 2000-2002.
Member of Advisory Board of All-Armenian (International ) Science and Educational Council, since 1999 ;
Chair of Phys.-Math. Commission of the Council, since 1999.
Supervisory
Three PhD theses
Visits
Visited nearly 40 institutions, among them was visiting professor in HKUST, Hong Kong (1997, 2001); in UNED Madrid, Spain (2005); Research Fellow in ICTP, Italy (2002-2009); Research in Pairs in Oberwolfach, Germany (2009); Marie Curie Fellow in University Colledge London (2013-2015); Leading visiting professor in Guangzhow universuty, China (2017).
Grants, appointments, invitations:
1. Grant of Technische Universitat (West) Berlin, 1990.
2. Grant "in the highest category" of International Congress of Mathematicians Zurich, 1994.
3. Grant of Hokkaido University, 1995.
4. Award of German Acad. Program DAAD (Deutsche Academische Austauschdienst), 1995.
5. Grant of Joensuu University (Finland), 1995.
6. Gustafson grant (Sweden), 1998.
7. Appointment on visiting professor position, Honk Kong University of Science and Technology, spring semester, 1998.
8. INTAS (grant n. 99-00089), 1999.
9. Award of German Acad. Program DAAD (Deutsche Academische Austauschdienst), 2000.
10. Appointment on visiting professor position, Honk Kong University of Science and Technology, winter semester, 2000.
11. Hong Kong Government grant for Science-"UGC grant of Hong Kong, Project No. HKUST 6134/01P", 2001.
12. Grant of ISAAC, 2001.
13. Grant for attending Nevanlinna conference in Romania, 2001.
14. Grant of the Academy of Finland, 2001.
15. Grant ANSEF, 2002.
16. INTAS 2002-2004.
17. 6 months Research Fellowship in Mathematics in the Abdus Salam Centre for Theoretical Physics, Italy, 2002.
18. NATO grant for Advanced Research Workshop in Yerevan, Armenia, (Codirector jointly with Prof. H. Begehr from Germany). 2002.
19. Grant of International Mathematical Union for organizing conference "Topics in Analysis and its Applications" in Yerevan Armenia, 2002.
20. Research Fellowship in Mathematics in the Abdus Salam Centre for Theoretical Physics, Italy, 2002, (6 months).
21. Visiting Scientist in the Abdus Salam Centre for Theoretical Physics, Italy, 2002, (1 months).
22. Visiting Scientist, University UNED at Madrid, 2003.
23. Visiting Scientist in the Abdus Salam Centre for Theoretical Physics, Italy, 2002, (1 months).
24. Grant ANSEF, 2004.
25. Visiting Scientist, ICTP (Trieste, Italy), 2004, (3 months).
26. Visiting Scientist, ICTP (Trieste, Italy), 2005, (3 months).
27. Visiting Professor in UNED in UNED at Madrid, 2005-2006 (1 year).
28. INTAS 2006-2007.
29. Visiting Scientist, ICTP (Trieste, Italy), 2006, (1 month).
30. Visiting Scientist, ICTP (Trieste, Italy), 2006, (2 months).
31. Visiting Scientist, ICTP (Trieste, Italy), 2007, (3 months).
32. Grant of the 6th ISAAC Congress (Ankara, METU), 2007.
33. Visiting Scientist, ICTP (Trieste, Italy), 2008, (2 months).
34. Visiting Scientist, ICTP (Trieste, Italy), 2009, (2 months).
35. Grant of the 6th ISAAC Congress (London, Imperial College), 2009.
36. Grant RiP (Germany, Oberwolbach) 2009, (3 weeks).
37. Grant of University College London (joint research), 2009, (3 weeks).
38. Grant of University College London (joint research), 2010, (two years).
39. Grant of the Georgian Institute of Applied Mathematics (joint research), 2011, (two years).
40. "International Marie Curie Award" given by Euro Union in 2012 (two years)-2013-2015.
41. Leading visiting professor in Guangzhow University (China), 3-months, 2017.
42. Invitation to deliver lectures in Tbilisi State University and Georgian Academy of Sciences, 2017, (2 weeks).
Participation in Conferences
Plenary lectures and invited addresses (14):
1. Plenary lecture at 17th Nevanlinna (Finnish-Romanian) Conference, Brashov 2000.
2. Plenary lecture at 6th Congress of International Society for Analysis its Applications and Computation, Ankara 2007.
3. Plenary lecture at Conference on Singularity theory and complex analysis, 2008, Tbilisi.
4. Plenary lecture at the first International Conference of the Georgian Math. Union, Batumi 2010.
5. Plenary lecture at the second International Conference of the Georgian Math. Union, Batumi 2011.
6. Plenary lecture at the International Conference of generalized analytic functions and their applications, Tbilisi, 2011.
7. Plenary lecture at 6th INTERNATIONAL CONFERENCE "Analytical Methods of Analysis and Differential Equations (AMADE-2011)",
dedicated to the memory of A.A. Kilbas, Minsk, Belarus, 2011.
8. One hour lecture on workshops "Frontiers of Nevanlinna Theory", University College London, 2012.
9. One hour lecture on workshops "Frontiers of Nevanlinna Theory", University College London, 2015.
10. Plenary lecture ar Guangzhow conference in complex analysis, 2017.
11.Plenary lecture at the 9th International Conference of the Georgian Math. Union, Batumi 201 9.
12. Plenary lecture at the 14th International Conference of the Georgian Math. Union, Batumi 2024.
13..Plenary lecture at the GMG international conference, Yerevan 2024.
14. Plenary lecture at the international conferece devoted to Y. Movsisyan, Yerevan, 2024.
Special sessions organized at the ISAAC Congresses.
Organizer of special session "Zeros and Gamma Lines -- Value distributions of real and complex functions and Mappings" at 8th ISAAC CONGRESS, Moscow, July 21-28, 2011.
Organizer of special session "Zeros and Gamma Lines -- Value distributions of real and complex functions and Mappings" at 7th ISAAC CONGRESS, Imperial College, London, July 13-18; 2009.
Organizer of special session "Value Distribution Theory of complex functions, Generalizations and related topics" at 5th ISAAC CONGRESS, Catania, Italy, June 26-30, 2005.
Organizer of special session "Value Distribution Theory of complex functions, Generalizations and related topics" at 4th ISAAC CONGRESS, York University, Toronto, Canada, August 16-21, 2003.
Conferences, workshops organized.
Member of scientific committee of the International conference on generalized analytic functions and their applications, Tbilisi, September 19--24, 2011.
Member of organizing committee of the second International Conference of the Georgian Math. Union, Batumi, September 14--19, 2011.
Member of organizing committee of the First International Conference of the Georgian Math. Union, Batumi, September 12 --19, 2010.
Codirector of the NATO Advanced research Workshop "Analysis and applications", Yerevan, September 22 --25, 2002.
Chair of local organizing committee of the "ISAAC Conference on Complex Analysis, Differential Equations and Related Topics", Yerevan, September 17 --21, 2002.
Member of organizing committee of "Mathematical Analysis and Economics", Sumy (Ukraine), April 1-4, 2003.
Member of organizing committee of "Mathematical Analysis", Lviv (Ukraine), October, 2000.
Member of organizing committee of conference "Mathematical Analysis", (dedicated to the memory of Professor Belyi), Donetzk, May, 1999
Research Grants
Foundation Title:
Obtained more than 40 grants, among them 2 DAAD , 3 INTAS, 2 ANSEF, 2 fellowships, 4 visiting professorship, ~ 20 for visits and collaboration.
Other
Content of this item.
Part 1. Tree groups of results that may have a significant impact on mathematics.
Part 2. Shortly about five trends.
Part 3. BOOKS, EDITED VOLUMES, LIST OF RESEARCH PAPERS.
PART 1. Tree groups of results that may have a significant impact on mathematics.
PART 1, Item 1. On a big gap in mathematics and studies of Gamma-lines and level sets.
Studies of zeros of real and complex functions f(z) of one variable constitute an essential part of real and complex analysis. In the complex analysis, these notions are studied in classical Nevanlinna-Ahlfors theories <cite>Nev</cite> as well as for a huge number of particular classes of functions. It is quite explainable: zeros, more generally a-points of f(x), play an important role in mathematics and admit some important physical interpretations.
Taking this into account, we have a completely inexplicable situation for functions u(x,y) of two real variables.
The zeros of u(x,y), that is, the solutions u(x,y)=0, are levels of functions u(x,y) that denote important concepts in many applied sciences, so one might expect that they should have been studied in detail. Meanwhile, the real situation is almost the opposite. Level sets in mathematics have been studied very little. Since level sets are mainly curves, their investigation must primarily involve consideration of length, curvature, and the number of connecting components.
The length of level sets was first studied in the frame of Gamma-lines <cite>Bars2002Book</cite> for imaginary parts of meromorphic functions. At present this topic is counted usually as a theory of Gamma-lines, see, for instance, «MathSciNet» , review MR2002433 (2005f:30001) related to my book [BarsBook2002] published in 2002.
Solutions of equations u(x,y)=0 (more generally u(x,y)=const) arise very often in pure and applied mathematics. Remember that the level sets of u-A admit a lot of interpretations (streaming line, potential line, isobar, isoterm) in different applied fields of engineering, physics, environmental problems etc. Notice that in "non degenerating cases" these solutions are some curves. In the case u(x,y) is a polynomial in two variables P(x,y) the solutions P(x,y)=const were studied very largely in the frame of Hilbert's problem 16, part 1; namely problem was to give bounds for the number of connected components of the solutions As to other geometric aspects of the solutions P(x,y)=const they were almost non touched. Also, till end of 1970s, we have no any study related to level sets of any large class of real functions u(x,y), even harmonic functions or more generally functions Rew or |w|. This was a big gap since solutions of Rew=A∈(-∞,∞), or of |w|=R∈(0,∞), have important interpretations in different applied sciences.
At present, we obtain similar results for arbitrary smooth enough real functions of two variables, see in <cite>BarsSuk2004</cite> and <cite>Bars2008</cite>.
Thus, studies of Gamma-lines enlarge the applicability of complex analysis (where, just a-points of functions w(z), i.e. solutions of w(z)=a, were studied before). Respectively studies of level sets of real functions open perspectives for considerations of numerous physical and other processes in many applied sciences.
PART 1, Item 2. The idea of complex conjugation allows us to transfer many studies of complex analysis to differential geometry.
In short, the idea is to establish relationships between the surfaces M in R³ and some complex functions w(z) associated with M; accordingly, the idea is to apply complex functions w(z) in studying surfaces M. In particular, real functions u(x,y) also constitute a surface; thus the idea also applies to real functions.
In some ways, this idea is similar to the idea of Riemann surfaces; in fact, this is an analog of the idea of Riemann surfaces which works in differential geometry and real analysis.
Application of this idea leads to some results in differential geometry. In particular, analogs of the main theorems of classical Nevanlinna theory (in complex analysis) are obtained that are valid for generalized minimal surfaces (in geometry).
We also pose some problems that, in my opinion, can lead to a new crossroads between complex analysis, differential geometry, and real analysis.
Part 1, item 3. Some (more than 20) new principles related to the basic concepts in mathematics.
The results of a general nature related to basic concepts in mathematics (usually referred as principles) were established mostly before 20th century and quite few in 20th century. We mean here primarily such basic concepts as arbitrary enough smooth real functions of one and two variables, plane curves and surfaces in R³, and arbitrary meromorphic (particularly analytic) functions in a given domain.
Some (more than 20) new principles concerning the mentioned concepts were established in my works. All these results are novel, i.e. have no predecessors. The results have led to some new trends (for which I got an "International Marie Curie Award" in 2012).
Among them, we mention:
1. two generalities related to arbitrary smooth real functions of one variable, see [BarsBook2002], chapter.4, [Bars2009], item 2;
2. a generality related to arbitrary smooth real functions of two variables, see [Bars2010b];
3. a generality related to arbitrary smooth curve in the plane - principle of angles, see [Bars2009] (plenary lecture at the 6th ISAAC Congress;
4. a generality related to arbitrary smooth surface in R³, see [Bars2017];
5. more than 15 generalities related to arbitrary analytic or meromorphic functions in a given domain and even more generalities related to functions in the complex plane, see [Bars1978], [Bars1981], [Bars1981a], [Bars1983], [Bars1986], [Bars1999], [Bars2010], [Bars2013, [Bars2017], [Bars2018], especially see my book [BarsBook2002] and survey [Bars2019]. Among them principle of logarithmic derivatives and principle of simple a-points, see the first section in [Bars2019].
We can add here also some results related to arbitrary complex polynomials, see, for instant, [Bars2018b].
Shortly about five trends.
The above mentioned generalities arose in my attempts to create some new trends in real and complex analysis, however they concerns also other areas such as, for instant, differential geometry, as well as real and complex differential equations.
In this subsections we present shortly five trends and describe shortly their novelty and applicability. The old three trends (3, 4 and 5) relate to analytic meromorphic functions and published during 1978-2007. Two trends (1 and 2) established quite recently. They relate respectively to real and complex differential equations.
Trend 1: relates to studies of oscillations, i.e. zeros, of solutions of systems of real differential equations.
Novelty and applicability. The zeros of similar solutions weren't considered before. This is an essential gap in the field since the zeros admit a lot of interpretations in different applied fields.
We start studies of zeros of similar solutions.
Trend 2: relates to studies of analytic or meromorphic solutions in a given domain of complex differential equations.
Novelty and applicability. Complex differential equations admitting solutions in the complex plane were widely studied. The main attention was paid to the zeros of similar solutions, more widely to value distribution of the solutions. As to the zeros of solutions in a given domain, they weren't considered before. This is an essential gap in the field since many applied scientists are, obviously, interested namely in the solution in a given domain.
We start studies of similar solutions in a given domain.
For several well known equations we consider as classical problems (for instance zeros, more generally a-points of solutions), as well as some new problems.
The key results of this trend are in process of publication; issued only one paper [BarsYuan].
The next three trends relate to some new developments closely connected with the classical Nevanlinna value distribution theory [Nev] and Ahlfors theory of covering surfaces [Ahlfors]. The trends discover several new phenomena related to meromorphic functions. It is interesting that they give also wide generalizations of the first and the second fundamental theorems in the mentioned theories, see [Bars1985].
Trend 3: relates to Gamma-lines of meromorphic functions w(z) particularly level sets of functions Rew(z).
Solutions of equations u(x,y)=0 (more generally u(x,y)=const) arise very often in pure and applied mathematics. Remember that the level sets u-A admit a lot of interpretations (streaming line, potential line, isobar, isoterm) in different applied fields of engineering, physics, environmental problems etc. Notice that in "non degenerating cases" these solutions are some curves. In the case u(x,y) is a polynomial in two variables P(x,y) the solutions P(x,y)=const were studied very largely in the frame of Hilbert's problem 16, part 1; namely problem was to give bounds for the number of connected components of the solutions As to other geometric aspects of the solutions P(x,y)=const they were almost non touched. Also, till end of 1970s, we have no any study related to level sets of any large class of real functions u(x,y), even harmonic functions or more generally functions Rew or |w|. Definitely this was a big gap since solutions of Rew=A∈(-∞,∞), or of |w|=R∈(0,∞), have important interpretations in different applied sciences.
Thus studies of these (very important in applications) solutions Rew=A may affect largely on the complex analysis
(where just a-points of functions w(z), i.e. solutions of w(z)=a, were studied before).
We consider now much larger concept. Let w(z) be a meromorphic function in a domain D and Γ be a curve in w-plane; for simplicity we assume that Γ is an analytic curves. Denoting by w⁻¹ the inverse functions we consider the set w⁻¹(Γ) lying in D (that is preimages of Γ under mapping by w). We call this set w⁻¹(Γ) as Gamma-lines of the curve Γ of the function w. Now we see that the solutions of Rew=A and of |w|=R are particular cases of Gamma-lines which we obtain by taking respectively Γ=γ(A):={w:Imw=A} and Γ=Γ(R):={w:|w|=R}. It is easy to see that in this case the γ(A)-lines are curves for any A and Γ(R)-lines are curves for any R≠0.
The concept of Gamma-lines (which is the set w⁻¹(Γ)) is quite similar to the concept of set a-points (which is the set w⁻¹(a), for a given point a∈C). This similarity raises a question: can theory of Gamma-lines developed in analogy with Nevanlinna-Ahlfors theories describing a-points?
At the end of 1970s we initiated studies in this directions and obtained an analog of the second fundamental theorems in Nevanlinna-Ahlfors theories. The topic was started in [Bars1978]; the results, later on, were enlarged in [Bars1981], [Bars1992] and summarized in the book [BarsBook2002].
Notice that the Gamma-lines are the sets of curves. Respectively the key aspects in their study should be their length or cardinality (like in the mentioned above Hilbert problem).
In this trend we present various estimates for the length L(D,Γ) of Γ-lines of w lying in D and give some integrated formulas for the length. This permits to get bounds for cardinalities of Γ-lines for w in D. This means particularly that we consider the Hilbert problem for harmonic functions (instead of polynomials in Hilbert's case).
At present this topic counted usually as theory of Gamma-lines, see, for instants, «MathSciNet» , review MR2002433 (2005f:30001) related to my book [BarsBook2002] published in 2002.
Trend 4: relates to studies of the geometry of a-points of meromorphic functions w(z).
Fundamental results of the classical Nevanlinna-Ahlfors theories deal with the numbers of a-points of meromorphic functions w(z).
A new "proximity phenomenon" for meromorphic functions
(as in the complex plane as well as in a given domain)
deals with the geometric locations of the a-points
and strengthen the mentioned fundamental results of Nevanlinna-Ahlfors theories related to the number of a-points.
To describe the "proximity phenomenon' or "proximity property" of a-points of meromorphic functions w(z) in the complex plane we consider two generic values a and b and for the set of a-points and the set of b-points define a distance between these sets and give upper bounds for this distance. Thus we estimate the closeness between these two sets and come to the proximity (or closeness) phenomenon, which, speaking qualitatively, says that for the generic a and b the sets of a-points and b-points should be close to each other to some extend. Different versions of this property were established in 1978-85, see [Bars1978], [Bars1981], [Bars1983], [Bars1985].
A similar phenomenon can be traced also in the case of an arbitrary function in a given domain, [Bars1997]
It is interesting that for the basic functions the proximity phenomenon implies also the main conclusions of preceding theories related to the numbers of a-points; see [Bars1983], [Bars1985].
This topic also counted as a theory in some reviews: see «Zentralblatt» , review 060230037 and «MathSciNet» , review MR1680525, (2000d:30041).
Trend 5: Universal version of value distribution for meromorphic functions in a given domain.
The Nevanlinna-Ahlfors theories reveal value distribution type phenomena of meromorphic functions w which describe interrelations between the numbers n(r,a_{ν}) of a-points for different values a₁,...,a_{q}, q≥2. Typical examples are the second fundamental theorems in these theories. The theories work well for the functions w in the complex plane while for the functions in a given disk they work only when w has "sufficiently large" growth.
Meantime, there are numerous, well known classes of functions defined in the unit disk (H^{p}, Dirichlet, Blaschke product etc.) for which the value distribution was not studied at all.
Can there be a general value distribution type result which is valid for an arbitrary meromorphic function in an arbitrary domain D? Since the main result in Nevanlinna-Ahlfors theories are the second fundamental theorems in both these theories the most ambitious task is as follows: can there be some analogs of these classical results are valid also for function in an arbitrary domain D? In other words the question is is there a generality for any analytic and meromorphic function analogous to these fundamental theorems?
It is easy to show that the mentioned classical theories do not contain enough characteristics to describe the numbers of zeros (or a-points) in general case.
We introduce corresponding new characteristic
and obtain a universal version of value distribution
which is valid for any meromorphic function in a given domain.
This leads to brand new type phenomena for functions in a given domain and in addition, for functions in the complex plane we get conclusions quite similar to those established earlier in Nevanlinna-Ahlfors theories.
The results were published in [Bars2010]; see also [Bars2019], Section 5.
REFERENCES
Ahlfors : Ahlfors L., Zur Theorie der Überlagerungsflächen, Acta mathematica, v. 65, 1935, 157--194.
Bars1978 : Barsegian G., New results in the theory of meromorphic functions, Dokl. Acad. Nauk SSSR, v. 238, n. 4, 1978, 777--780 (in Russian, translated in Soviet Math. Dokl.).
Bars1981 : Barsegian G., On the geometry of meromorphic functions, Mathem. sbornic, v. 114(156), n. 2, 1981, 179--226 (in Russian, translated in Math. USSR Sbornic).
Bars1981a : Barsegian G., Exceptional values associated with logarithmic derivatives of meromorphic functions, Izvestia Acad. Nauk Armenii, v. 16, n. 5, 1981, 408-423.
Bars1983 : Barsegian G., Proximity property of a-points of meromorphic functions, Math. Sbornic, v. 120(162), (1), 1983, 42-63, (in Russian); Transl. In "Math. USSR Sbornik ".
Bars1985 : Barsegian G., Proximity property of meromorphic functions and the structure of the univalent domains on Riemann surfaces, Izvestia Acad. Nauk Armenii, Matematika, v. 20, n. 5, 1985, 375--400; v. 20, n. 6, (1985), 407--425, (in Russian); Transl. in "Journal of Contemporary Math. Analysis ", Armenian Acad. of Sci., Allerton Press.
Bars1986 : Barsegian G., Estimates of derivative of meromorphic functions oh sets of a-points, Journal of London Math. Soc., (2), 34, 1986, 534-540.
Bars1992 : Barsegian G., Tangent variation principle in complex analysis, Izvestia Acad. Nauk Armenii, v.27, n.3, 1992, p.37-60. (in Russian); Transl. In "Journal of contemporary math. Analysis" (Armenian Acad. of Sci.), Allerton Press.
Bars1997 : Barsegian G., Principle of closeness of sufficiently large sets of a-points of meromorphic functions, Hokkaido Math. Journal, v.26, n.2, 1997, p. 451-456.
Bars1998 : Barsegian G., On a method of the study of algebraic differential equations of higher orders, Bulletin of Honk Kong Math. Soc., 2, 1, 1998, 159-164.
Bars1999 : Barsegian G., Estimates of higher derivatives of meromorphic functions on sets of its a-points, Bulletin of Honk Kong Math. Soc., v. 2, n. 2, 1999, 341-346.
Bars2004 : Barsegian G., A new program of investigations in Analysis: Gamma-lines approaches, pp. 1-73; in book: Value distribution and related topics, editors G. Barsegian, I. Laine and C.C. Yang; Kluwer, Series: Advances in Complex Analysis and its Applications, 2004.
Bars2008 : Barsegian G., Turbulence of real functions, Georgian Mathematical Journal, 15, n.2, 2008, p. 225--240.
Bars2009 : Barsegian G., Some interrelated results in different branches of geometry and analysis, Further progress in analysis, 3--32, World Sci. Publ., Hackensack, NJ, 2009.
Bars2010 : Barsegian G., A universal value distribution for arbitrary meromorphic functions in a given domain, Progress in analysis and its applications, 123--128, World Sci. Publ., Hackensack, NJ, 2010.
Bars2010b : Barsegian G., Miscellanea in integral geometry, algebraic geometry and real analysis, Reports of the National Academy of Sciences of Armenia, v. 103, n. 3, 2010, p. 210-219.
Bars2013 : Barsegian G., Revisiting a general property of meromorphic functions, Contemporary Mathematics, 591, 2013, 45-49.
Bars2017 : Barsegian G., A triple principle (for curves, surfaces and complex functions) and universal version of value distribution theory, pp.67-86, In book: Complex Analysis and Dynamical Systems VII, Contemporary Mathematics (USA), 699, 2017.
Bars2017b : Barsegian G., Initiating a new trend in complex equations studying solutions in a given domain: problems, results, approaches. Preprint.
Bars2018 : Barsegian G. A new principle for arbitrary meromorphic functions in a given domain, Georgian Math. Journal, 25, 2, 2018, p. 181-186.
Bars2018b : Barsegian G., Sergeev A. and Montes-Rodrigues A., A new sharp inequality for arbitrary complex polynomials related to Gamma-lines, Complex variables and elliptic equations, 2018.
Bars2018c : Barsegian G. and Yuan W., On some generalized Painlevé and Hayman type equations with meromorphic solutions in a bounded domain, Georgian Math. Journal, 25, 2, 2018, p. 187-194.
Bars2019 : Barsegian G., Survey of Some General Properties of Meromorphic Functions in a Given Domain, p. 47-67, in book "Analysis as a Life. Dedicated to Heinrich Begehr on the Occasion of his 80th Birthday, " Editors: Rogosin S., Çelebi, O., Birkhauser, 2019.
Bars2018 1 : Barsegian G., On solutions of Riccati equation in a given domain, Preprint.
BarsBook2002 : Barsegian G., Gamma-lines: on the geometry of real and complex functions, Taylor and Francis, London, New York, 2002.
BarsSuk2004 : Barsegian G. and Sukiasyan G., Methods for study level sets of enough smooth functions, Analysis and applications. In book "Topics in Analysis and Applications": the NATO Advanced Research Workshop, August 2002, Yerevan", editors G. Barsegian, H. Begehr, Kluwer, Series: NATO Science Publications, 2004.
BarsLe : Barsegian G. and Lê D. T., On a topological property of multi-valued solutions of some general classes of complex differential equations, Complex Variables Theory Appl., v. 50, n. 5, 2005, 307-318.
BarsLaineLe : Barsegian G., Laine I. and Lê D. T., On topological behavior of solutions of some algebraic differential equations, Complex Variables and Elliptic Equations, v. 53 (2008), 411 - 421.
BarsMeng : Barsegian G. and Meng F., On complex equations w^{(k)}=gw with solutions in a given domain, Submitted to Complex Variables.
BarsYuan : Barsegian G. and Yuan W., On some generalized Painlevé and Hayman type equations with meromorphic solutions in a bounded domain, Georgian Math. Journal, 25, 2, 2018, p. 187-194.
BarsYuan 1 : Barsegian G. and Yuan W., Some estimates for the solutions of the first order non-algebraic classes of equations, Preprint.
Hilbert : Hilbert D., Mathematical problems, Archif fur Math. und Phys., series III, 11, 1901, 44-63, 213-237.
Laine : Laine I., Nevanlinna Theory and Complex Di¤erential Equations, W. de Gruyter, Berlin-New York, 1993.
Nev : Nevanlinna R., Eindentige analitische Funktionen, Berlin. Springer. 1936.
BOOKS, EDITED VOLUMES.
1. Barsegian G.A. (quest editor), Value Distribution Theory and Geometric complex functions theory, In the journal "Izvestia Acad. Nauk Armenii", vol. 3, 1997; Translation in Journal of Contemporary Math. Analysis, Allerton Press.
2. Barsegian G.A. (quest editor), Value Distribution Theory and Geometric complex functions theory, In the journal "Izvestia Acad. Nauk Armenii", vol. 4, 1997; Translation in Journal of Contemporary Math. Analysis, Allerton Press.
3. Barsegian G.A., Gamma-lines: on the geometry of real and complex functions, Taylor and Francis, London, New York, 2002.
4. Barsegian, I. Laine and C.C. Yang (editors), Value distribution and related topics, Kluwer, series "Advances in complex analysis and related topics", 2004.
5. G. Barsegian, H. Begehr (editors), Topics in Analysis and its Applications, (the NATO Advanced Research Workshop, September 2002, Yerevan), Kluwer, series NATO Science Publications, 2004.
6. Barsegian G., Begehr H., Nersessyan A. and Ghazaryan H. (editors), Complex Analysis, Differential Equations and Related Topics, (ISAAC Conference, September 2002, Yerevan), Nat. Acad. Sci. Armenia, 2004.
RESEARCH PAPERS.
1. Barsegian G., Deficient values and the structure of covering surfaces, Izvestia Acad. Nauk Armenii, v.12, 1977, p.46-53.
2. Barsegian G., Distribution of sums of a-points of meromorphic functions, Dokl. Acad. Nauk SSSR, v. 234, n. 4, 1977, p. 761-763.
3. Barsegian G., A Geometric approach to the problem of ramifications of Riemann surfaces, Dokl. Acad. Nauk SSSR, v.237, n. 4, 1977, p.
4. Barsegian G., To the distribution of distortions under mapping by meromorphic functions, Dokl. Acad. Nauk SSSR, v.237, n. 5, 1977, p. 1009-1011. (in Russian, translated in Soviet Math. Dokl.)
5. Barsegian G., A Geometric approach to the problem of ramifications of Riemann surfaces, Dokl. Acad. Nauk Armenii, v.65, n. 4, 1977, p.216-220.
6. Barsegian G., On distribution of zeros of imaginary parts of meromorphic functions, Math. Zametki, v.24, n. 2, 1978, p.183-194.
7. Barsegian G. New results in the theory of meromorphic functions, Dokl. Acad. Nauk SSSR, v.238, n.4, 1978, p.777-780.
8. Barsegian G. On geometric structure of image of disks under mappings by meromorphic functions, Math. Sbornic, v. 106(148), n. 1, 1978, p.35-43.
9. Barsegian G. On deficient values and growth of meromorphic functions with finite lower orders, Dokl. Acad. Nauk Armenii, v.67, 1978, p.291-294.
10. Barsegian G., Distribution of sums of a-points and Riemann surfaces of the class F-g, Math. Zametki, v.25, n. 1, 1979, p.51-59.
11. Barsegian G., On the geometry of meromorphic functions, Math. Sbornic, v.114(156), n.2, 1981, p.179-226. (in Russian); Trans. in "Math. USSR Sbornic.
12. Barsegian G., Exceptional values associated with logarithmic derivatives of meromorphic functions, Izvestia Acad. Nauk Armenii, v. 16, n. 5, 1981, p.408-423.
13. Barsegian G., Proximity property of a-points of meromorphic functions, Math. Sbornic, Vol. 120(162), n. 1, 1983, p.42-63, (in Russian); Transl. In "Math. USSR Sbornik ".
14. Barsegian G., On a necessary condition of existence of solutions of the general interpolation problem of R. Nevanlinna, Izvestia Acad. Nauk Armenii, v. 18, n.2, 1983, p.442-447.
15. Barsegian G. United approach to the study of deficient values, Borel's rays and cercle de remplicages, Dokl. Acad. Nauk SSSR, v.271, n. 1, 1983, p.11-14.
16. Barsegian G., On mutual arrangement of asymptotic paths and a-points of meromorphic functions, Izvestia Acad. Nauk Armenii, v. 18, n. 2, 1983, p.124-133.
17. Barsegian G., Proximity property of meromorphic functions and the structure of the univalent domains on Riemann surfaces, Izvestia Acad. Nauk Armenii, Matematika, v. 20, n. 5, (1985), 375--400; v. 20, n. 6, (1985), 407--425, (in Russian); Transl. in "Journal of Contemporary Math. Analysis ", Armenian Acad. of Sci., Allerton Press.
18. Barsegian G., On a method for estimations of orders of meromorphic solutions of algebraic differential equations based on proximity property of a-points, Dokl. Acad. Nauk Armenii, v. 82, n. 5, 1986, p.495-598.
19. Barsegian G., Estimates of derivative of meromorphic functions oh sets of a-points, Journal of London Math. Soc., (2), 34, 1986, p.534-540.
20. Barsegian G., On locations of a-points of meromorphic functions, Review Romaine de mathematiques Pures at Appliquess, v.32, n. 10, p. 865-873.
21. Barsegian G., Applications of L.Ahlfors theory of covering surfaces to the study of algebraic differential equations of the second orders, Differentsialnye Uravnenija, v.23, n. 2, 1987, p. 341-344.
22. Barsegian G. and Masrtirosian K., On the values accepted by analytical functions on the set of a-points of the meromorphic function in given domain, Izvestia Acad. Nauk Armenii, v.24, n.3, 1989, p.248-258.
23. Barsegian G. and Sukiasian G., Proximity property of a-points for meromorphic functions with simple zeros and poles on rays, ARMNIINTI, n.16, 1989, p.1-46.
24. Barsegian G. and Sukiasian G., Proximity property of a-points for meromorphic functions with close zeros and poles, Izvestia Acad. Nauk Armenii, v. 25, n.1, 1990, p.21-33.
25. Barsegian G. and Sukiasian G., Distributions of values and proximity of a-points for quotients of Blaschke products with nearly zeros. Studio Sci. Math. Hungarica, v. 25, 1990, p. 419-428.
26. Barsegian G. and Petrosian V., Cartan's identity for some magnitudes associated with logatithmic derivatives of meromorphic function, Izvestia Acad. Nauk Armenii, v 25, n.6, 1990.
27. Barsegian G., Property of comparability of derivatives, and property of comparability of distances between a-points of meromorphic functions, Izvestia Acad. Nauk Armenii, v. 26, n.1, 1991, p. 52-70.
28. Barsegian G. and Sukiasian G., Meromorphic functions with nearly zeros and poles lying on rays, Izvestia Acad. Nauk Armenii, v. 26, n.2, 1991, p.
29. Barsegian G. and Belyi V., On polynomial approximations of function on Riemann surface which are inverse to the given meromorphic functions, Izvestia Acad. Nauk Armenii, v. 26, n.5, 1991, p.
30. Barsegian G., Two new principles concerning presenting derivatives and distances between the a-points of meromorphic functions, Review Romaine de mathematiques Pures at Appliquess, v.34, n. 7-8, 1991, p. 420-424.
31. Barsegian G., Tangent variation principle in complex analysis, Izvestia Acad. Nauk Armenii, v.27, n.3, 1992, p.37-60. (in Russian); Transl. In "Journal of contemporary math. Analysis" (Armenian Acad. of Sci.), Allerton Press.
32. Barsegian G. and Avakian V. and Karachanian M., Space generalized quasiconformal mappings, ARMNIINTI, n.5, 1993, p. 1-35.
33. Barsegian G.A., Principle of partitioning of meromorphic functions, Math. Montisnigri, v. 5, 1995, p. 18-26.
34. Barsegian G., Some remarks on links between mutual arrangements of a-points of meromorphic functions and ramifications, Math. Montisnigri, v. 4, 1996, p.1-7.
35. Barsegian G. and Petrosian V., Exeptional values defined by means of logarithmic derivatives of higher orders , v.31, 1996,
36. Barsegian G., Principle of closeness of sufficiently large sets of a-points of meromorphic functions, Hokkaido Math. Journal, v.26, n.2, 1997, p. 451-456.
37. Barsegian G.A., Some applications of principle of partitioning of meromorphic functions, Part 1. Comparability property. Izvestia Acad. Nauk Armenii, v. 31, n. 3-4, 1997, p. 5-50.
38. Barsegian G.A. and Sikiasian G.A., Some applications of principle of particioning of meromorphic functions, Part 2. Accumulations of a-points and Littlewood property. Izvestia Acad. Nauk Armenii, v. 32, n. 3-4, 1997, p. 5-10.
39. Barsegian G.A. (quest editor), Value Distribution Theory and Geometric complex functions theory, In the journal "Izvestia Acad. Nauk Armenii", vol. 3, 1997; Translation in Journal of Contemporary Math. Analysis, Allerton Press.
40. Barsegian G.A. (quest editor), Value Distribution Theory and Geometric complex functions theory, In the journal "Izvestia Acad. Nauk Armenii", vol. 4, 1997; Translation in Journal of Contemporary Math. Analysis, Allerton Press.
41. Barsegian G., On a method of the study of algebraic differential equations of higher orders, Bulletin of Honk Kong Math. Soc., vol. 2, n. 1, (1998), p. 159-164.
42. Barsegian G., Estimates of higher derivatives of meromorphic functions on sets of its a-points, Bulletin of Honk Kong Math. Soc., vol. 2, n. 2, (1999), p. 341-346
43. Barsegian G., Additions to Ahlfors theory of covering surfaces, Review Romaine de mathematiques Pures at Appliquess, v. 44, n.2, 1999. p. 503-519.
44. Barsegian G.A. and Yang C.C., Some new generalizations in the theory of meromorphic functions and their applications. Part 1. On the magnitudes of functions on the sets of a-points of derivatives. Complex Variables, v. 41, 2000, p. 293-313.
45. Barsegian G.A., Laine I. and Yang C.C., Stability phenomenon and problems for complex differential equations with relations to sharing values, Mathematichni Studii, v. 13, 2000, p. 224-228.
46. Barsegian G.A. and Yang C.C., Some new generalizations in the theory of meromorphic functions and their applications. Part 2. On the derivatives of meromorphic and inverse functions, Complex Variables, v. 44, 2001, p.13-27.
47. G. A. Barsegian, I. Laine and C. C. Yang, Locations of values of meromorphic solutions of algebraic differential equations, Complex Variables, v. 46, 2001, p. 323 - 336.
48. Barsegian G.A. and Walker P., On the mutual arrangement of a-points of a meromorphic functions and its derivatives, 2000,Southeast Asian Bulletin of Mathematics, v. 26, 2002, p.1--6.
49. Barsegian G., Laine I. and Yang C. C., On a method of estimating derivatives in complex differential equations, Journal Math. Soc. Japan, v. 54, n. 4, 2002, p. 923-935.
50. Barsegian G., Begehr H. and Laine I., Stability phenomenon for generalizations of algebraic differential equations, Zeitshirft fur Analysis und ihre Anwendungen, 21, n. 2, 2002, pp. 495 -503.
51. Barsegian G., Gamma-lines: on the geometry of real and complex functions, Taylor and Francis, London, New York, 2002.
52. Barsegian G. and Yang C. C., A new property of meromorphic functions and its applications. Analysis and applications---ISAAC 2001 (Berlin), 109--120, Int. Soc. Anal. Appl. Comput., 10, Kluwer Acad. Publ., Dordrecht, 2003.
53. Barsegian, I. Laine and C.C. Yang (editors), Value distribution and related topics, Kluwer, series "Advances in complex analysis and its Applications", 2004.
54. G. Barsegian, H. Begehr (editors), Topics in Analysis and its Applications, (the NATO Advanced Research Workshop, September 2002, Yerevan), Kluwer, series NATO Science Publications, 2004.
55. Barsegian G., Begehr H., Nersessyan A. and Ghazaryan H. (editors), Complex Analysis, Differential Equations and Related Topics, (ISAAC Conference, September 2002, Yerevan), Nat. Acad. Sci. Armenia, 2004.
56. Barsegian G. and Yang C.C., On some new concept of exceptional values of meromorphic functions and its applications. In book: Value distribution and related topics, editors G. Barsegian, I. Laine and C.C. Yang; Kluwer, Series: Advances in Complex Analysis and its Applications, 2004.
57. Barsegian G. and Sukiasyan G., Methods for study level sets of enough smooth functions, Analysis and applications. In book "Topics in Analysis and Applications": the NATO Advanced Research Workshop, August 2002, Yerevan", editors G. Barsegian, H. Begehr, Kluwer, Series: NATO Science Publications, 2004.
58. Barsegian G., A new program of investigations in Analysis: Gamma-lines approaches, pp. 1-73; in book: Value distribution and related topics, editors G. Barsegian, I. Laine and C.C. Yang; Kluwer, Series: Advances in Complex Analysis and its Applications, 2004.
59. Barsegian G., Sarkisian A., and Yang C.C., On quasimeromorphic solutions of complex differential equations. In book: Value distribution and related topics, editors G. Barsegian, I. Laine and C.C. Yang, Kluwer, Series: Advances in Complex Analysis and its Applications, 2004.
60. Barsegian G. and Begehr H., Lines of catastrophe: problems, examples of solutions, connections with Nevanlinna theory and Gamma-lines, Third ISAAC Congress, Freie Universitat Berlin, August 20-25, 2001, Plenary and selected lectures, World Scientific, 2003.
61. Barseghyan K. and Barsegian G., A method for study oscillations of ordinary differential equations with an application to population dynamics, In book "Topics in Analysis and Applications": the NATO Advanced Research Workshop, August 2002, Yerevan", editors G. Barsegian, H. Begehr, Kluwer, Series: NATO Science Publications, 2004.
62. Barsegian G., Gamma-lines of polynomials and a problem by Erdosh-Herzog-Piranian, In book "Topics in Analysis and Applications": the NATO Advanced Research Workshop, August 2002, Yerevan", editors G. Barsegian, H. Begehr, Kluwer, Series: NATO Science Publications, 2004.
63. Barseghyan K. G. and Barsegian G., On a Nevanlinna type result for solutions of some nonlinear first order differential equations, in book: Barsegian G., Begehr H., Ghazaryan H. and Nersessyan A. (editors), Complex Analysis, Differential Equations and Related Topics, ISAAC Conference, September 17 -21, 2002, Yerevan, Armenia, Nat. Acad. Sci. Armenia, 2004.
64. Barsegian G. and Lê D. T., On a topological property of multi-valued solutions of some general classes of complex differential equations, Complex Variables Theory Appl., v. 50, n. 5, 2005, p. 307-318.
65. Barseghyan K. and Barsegian G., Oscillations of Solutions of ODE and Nevanlinna Theory, Global Journal of Mathematics & Mathematical Science (GJMMS), 2005.
66. Barseghyan K. and Barsegian G., On a Nevanlinna type result for solutions of nonautonomous equations y′=F₁(x,y), x′=F₂(x,y), Complex Variables Theory Appl., v. 50, n. 7-11, 2005, p. 469-477.
67. Barsegian G., An analog of Nevanlinna fundamental theorem for real functions. Complex Variables Theory Appl., v. 50, n. 7-11, 2005, p. 535-541.
68. Barsegian G., Some new inequalities in geometry and analysis, "Izvestia Acad. Nauk Armenii", v. 42, n. 2, 2007, (in Russian); Translation in Journal of Contemporary Math. Analysis, Allerton Press.
69. Barsegian G., Fernandez A. and and Lê D. T., On closeness of a- and b-points of arbitrary polynomials, J. Appl. Funct. Anal. 2 (2007), no. 1, 13-20.
70. Barsegian G., Laine I. and Lê D. T., On topological behavior of solutions of some algebraic differential equations, Complex Variables and Elliptic Equations, v. 53 (2008), p. 411 - 421.
71. Barsegian G., Turbulence of real functions, Georgian Mathematical Journal, 15, n.2, 2008, p. 225--240.
72. Barsegian G, Some interrelated results in different branches of geometry and analysis, p.3-33, in book "Further progress in analysis. Proceedings of the 6th International ISAAC Congress, Ankara, Turkey, 13 -- 18 August 2007", editors Begehr H., Celebi O. and Gilbert R., World Scientific, 2009.
73. Barsegian G. and Lê D. T., On the length of level sets of real functions, Analysis, 30, 2010, p. 135-146.
74. Barsegian G., A purely geometric inequality for analytic functions admitting no zeros, Complex Variables and Elliptic Equations, v. 55, n. 1, 2010, p. 249 - 251.
75. Barsegian G., Universal value distribution for arbitrary meromorphic functions in a given domain, p. 123-128, in book "Progress in Analysis and its Applications, Proceedings of the 7th International ISAAC Congress, Imperial College London, UK, 13-18 July 2009", editors Ruzhansky M.and Wirth J.,World Scientific, 2010.
76. Barsegian G. and Sargsyan A., A method of counting the zeros of the Riccati equation and its application to biological and economical prognoses, p. 129-135, in book "Progress in Analysis and its Applications, Proceedings of the 7th International ISAAC Congress, Imperial College London, UK, 13-18 July 2009", editors Ruzhansky M.and Wirth J.,World Scientific, 2010.
77. Barsegian G., Miscellanea in integral geometry, algebraic geometry and real analysis, Reports of the National Academy of Sciences of Armenia, v. 103, n. 3, 2010, p. 210-219.
78. Alonso A., Barsegian G. and Fernandez A., Gamma-lines approach in the study of global behavior of solutions of complex differential equations, Complex Variables and Elliptic Equations, v 56, Issue 1-4, 2011, p. 119-135.
79. Barsegian G., On a principle in the theory of complex polynomials implying Gauss-Lucas Theorem, p. 14-20, in "Recent Developments in Generalized Analytic Functions and Their Applications", edited by G.Giorgadze, Tbilisi State University, 2011.
80. Barsegian G., On the proximity property of meromorphic functions initiating some novel studies in the complex analysisp, p. 20-25, in "Recent Developments in Generalized Analytic Functions and Their Applications", edited by G.Giorgadze, Tbilisi State University, 2011.
81. Barsegian G., Revisiting a general property of meromorphic functions, Contemporary Mathematics (USA), v. 591, 2013, p. 45-49.
82. Barsegian G., Idea of complex conjugacy and counterparts of some complex analytic principles in differential geometry, Reports and Studies in Forestry and Natural Sciences (Finland), n. 14, p. 27-44.
83. Barsegian G., A triple principle (for curves, surfaces and complex functions) and universal version of value distribution theory, 699, 2017, pp.67-86, In book: Complex Analysis and Dynamical Systems VII, Contemporary Mathematics (USA), 2017.
84. Barsegian G., Sergeev A. and Montes-Rodrigues A., A new sharp inequality for arbitrary complex polynomials related to Gamma-lines, Complex variables and elliptic equations, 2018.
85. Barsegian G., A new principle for arbitrary meromorphic functions in a given domain, Georgian Math. Journal, 25, 2, 2018, p. 181-186.
86. Barsegian G. and Yuan W., On some generalized Painlevé and Hayman type equations with meromorphic solutions in a bounded domain, Georgian Math. Journal, 25, 2, 2018, p. 187-194.
87. Barsegian G., Survey of Some General Properties of Meromorphic Functions in a Given Domain, p. 47-67, in book "Analysis as a Life. Dedicated to Heinrich Begehr on the Occasion of his 80th Birthday, " Editors: Rogosin S., Çelebi, O., Birkhauser, 2019.
Barsegian G. and Meng F., On some higher order equations admitting meromorphic solutions in a given domain, Georgian Math Journal, 2021, 28(4): 529-532.
89. Barsegian G., Meng F. Yuan W., Some Estimates for the Solutions of the First Order Non-Algebraic Classes of Equations, Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences), 2020, Vol. 55, No. 2, pp. 96--104. (translated from Russian in Izvestiya Natsional'noi Akademii Nauk Armenii, Matematika, Vol. 55, No. 2, pp. 35--45.)
90. Barsegian G., A principle related to real functions, Izvetiya Akademii Nauk Armenii, v. 56, n. 3, 2021, pp. 10 -- 16.
91. Barsegian G., Knots of plane curves. Applications to ODE. Izvetiya Akademii Nauk Armenii, v. 58, 3, 2023, pp. 14-20.
92. Barsegian G., On the rotations and limit cycles of solutions to the basic system of equations, Georgian Mathematical Journal, 2024, pp. ???
93. Barsegian G., Universal Version of Value Distribution Theory for Functions in a Given Domain, Lobachevskii Journal of Mathematics, 2024, Vol. 45, No. 8, pp. 3478--3486.
(ISSN 1995-0802, DOI: 10.1134/S1995080224604648).
94. Barsegian G., On the Zeros of First-Order Differential Equations, Lobachevskii Journal of Mathematics, 2024, Vol. 45, No. 8, pp. 3474--3477.
(ISSN 1995-0802, ///DOI: 10.1134/S1995080224604247)
95. Barsegian G., On the Zeros of Some Well-Known Equations, Lobachevskii Journal of Mathematics, 2024, Vol. 45, No. 8, pp. 3463--3473.
(ISSN 1995-0802, /// DOI: 10.1134/S1995080224604211)
96. Barsegian G., A new property of arbitrary complex polynomials, COMPLEX VARIABLES AND ELLIPTIC EQUATIONS, 2024, ???