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- ItemOn the construction of a class of generalized Kukles systems having at most one limit cycle(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2013) Schneider, Klaus R.; Grin, AlexanderConsider the class of planar systems fracdxdt=y,quadfracdydt=−x+musumj=03hj(x,mu)yj depending on the real parameter $mu$. We are concerned with the inverse problem: How to construct the functions $h_j$ such that the system has not more than a given number of limit cycles for $mu$ belonging to some (global) interval. Our approach to treat this problem is based on the construction of suitable Dulac-Cherkas functions $Psi(x,y,mu)$ and exploiting the fact that in a simply connected region the number of limit cycles is not greater than the number of ovals contained in the set defined by $Psi(x,y,mu)=0.$
- ItemA new approach to study limit cycles on a cylinder(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2010) Cherkas, Leonid; Grin, Alexander; Schneider, Klaus R.We present a new approach to study limit cycles of planar systems of autonomous differential equations with a cylindrical phase space $Z$. It is based on an extension of the Dulac function which we call Dulac-Cherkas function $Psi$. The level set $W:=vf,y) in Z: Psi(vf,y)=0$ plays a key role in this approach, its topological structure influences existence, location and number of limit cycles. We present two procedures to construct Dulac-Cherkas functions. For the general case we describe a numerical approach based on the reduction to a linear programming problem and which is implemented by means of the computer algebra system Mathematica. For the class of generalized Liénard systems we present an analytical approach associated with solving linear differential equations and algebraic equations
- ItemStudy of the bifurcation of a multiple limit cycle of the second kind by means of a Dulac-Cherkas function: A case study(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2016) Schneider, Klaus R.; Grin, AlexanderWe consider a generalized pendulum equation depending on the scalar parameter having for = 0 a limit cycle Gamma of the second kind and of multiplicity three. We study the bifurcation behavior of Gamma for -1 ≤ ≤ (√5 + 3)/2 by means of a Dulac-Cherkas function.
- ItemConstruction of generalized pendulum equations with prescribed maximum number of limit cycles of the second kind(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2016) Schneider, Klaus R.; Grin, AlexanderConsider a class of planar autonomous differential systems with cylindric phase space which represent generalized pendulum equations. We describe a method to construct such systems with prescribed maximum number of limit cycles which are not contractible to a point (limit cycles of the second kind). The underlying idea consists in employing Dulac-Cherkas functions. We also show how this approach can be used to control the bifurcation of multiple limit cycles.
- ItemGlobal bifurcation analysis of a class of planar systems(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2017) Grin, Alexander; Schneider, Klaus R.We consider planar autonomous systems dx/dt =P(x,y,λ), dy/dt =Q(x,y,λ) depending on a scalar parameter λ. We present conditions on the functions P and Q which imply that there is a parameter value λ0 such that for &lambda > λ0 this system has a unique limit cycle which is hyperbolic and stable. Dulac-Cherkas functions, rotated vector fields and singularly perturbed systems play an important role in the proof.