%0 Journal Article %T On the Number of Real Roots of the Yablonskii-Vorob'ev Polynomials %A Pieter Roffelsen %J Symmetry, Integrability and Geometry : Methods and Applications %D 2012 %I National Academy of Science of Ukraine %X We study the real roots of the Yablonskii-Vorob'ev polynomials, which are special polynomials used to represent rational solutions of the second Painlev¨¦ equation. It has been conjectured that the number of real roots of the nth Yablonskii-Vorob'ev polynomial equals [(n+1)/2]. We prove this conjecture using an interlacing property between the roots of the Yablonskii-Vorob'ev polynomials. Furthermore we determine precisely the number of negative and the number of positive real roots of the nth Yablonskii-Vorob'ev polynomial. %K second Painlev¨¦ equation %K rational solutions %K real roots %K interlacing of roots %K Yablonskii-Vorob'ev polynomials %U http://dx.doi.org/10.3842/SIGMA.2012.099