Resonance and Multiplicity in Periodic Boundary Value Problems with
Singularity
Irena Rachunkova, Milan Tvrdy, Ivo Vrkoc
Irena Rachunkova, Department of Math., Palacky University,
779 00 OLOMOUC, Tomkova 40, Czech Republic, e-mail: rachunko@risc.upol.cz; Milan Tvrdy, Mathematical Institute, Acad. Sci.of the Czech Republic,
115 67 PRAHA 1, Zitna 25, Czech Republic, e-mail: tvrdy@math.cas.cz,
http://www.math.cas.cz/~tvrdy/;
Ivo Vrkoc, Mathematical Institute, Acad. Sci.of the Czech Republic,
115 67 PRAHA 1, Zitna 25, Czech Republic, e-mail: vrkoc@matsrv.math.cas.cz
Summary: The paper deals with the boundary value problem $u''+k
u=g(u)+e(t), u(0)=u(2\pi), u'(0)=u'(2\pi),$ where $k\in R,$ $g: (0,\infty)\to\R$
is ontinuous, $e\in\L[0,2\pi]$ and $\lim_{x\to 0+}\int_x^1 g(s) ds=\infty.$
In particular, the existence and multiplicity results are obtained using
the method of lower and upper functions which are constructed as solutions
of related auxiliary linear problems.
Keywords: Second order nonlinear ordinary differential
equation, periodic problem, lower and upper functions.
