Browsing by Author "Gasull Embid, Armengol"

Rational periodic sequences for the Lyness recurrence
Gasull Embid, Armengol; Mañosa Fernández, Víctor; Xarles Ribas, Xavier (20100430)
Other
Open AccessConsider the celebrated Lyness recurrence $x_{n+2}=(a+x_{n+1})/x_{n}$ with $a\in\Q$. First we prove that there exist initial conditions and values of $a$ for which it generates periodic sequences of rational numbers with ... 
The period function for Hamiltonian systems with homogeneous nonlinearities
Gasull Embid, Armengol; Guillamon Grabolosa, Antoni; Mañosa Fernández, Víctor; Mañosas Capellades, Francesc (1996)
Article
Open AccessThe paper deals with Hamiltonian systems with homogeneous nonlinearities. We prove that such systems have no isochronous centers, that the period annulus of any of its centres is either bounded or the whole plane and that ... 
The period function for secondorder quadratic ODEs is monotone
Gasull Embid, Armengol; Guillamon Grabolosa, Antoni; Villadelprat Yagüe, Jordi (2003)
Article
Open AccessVery little is known about the period function for large families of centers. In one of the pioneering works on this problem, Chicone [?] conjectured that all the centers encountered in the family of secondorder diﬀerential ... 
Upper bounds for the number of zeroes for some Abelian integrals
Gasull Embid, Armengol; Lázaro Ochoa, José Tomás; Torregrosa, Joan (201209)
Article
Restricted access  publisher's policyConsider the vector field x′=−yG(x,y),y′=xG(x,y), where the set of critical points {G(x,y)=0} is formed by K straight lines, not passing through the origin and parallel to one or two orthogonal directions. We perturb it ... 
Upper bounds for the number of zeroes for some Abelian Integrals
Lázaro Ochoa, José Tomás; Gasull Embid, Armengol; Torregrosa, Joan (20120112)
External research report
Open AccessAbstract. Consider the vector field x0 = yG(x, y), y0 = xG(x, y), where the set of critical points {G(x, y) = 0} is formed by K straight lines, not passing through the origin and parallel to one or two orthogonal ...