Phase Portrait of the Riccati Quadratic Polynomial Differential Systems

Abstract: In this paper we characterize the phase portrait of the Riccati quadratic polynomial differential systems $$\dot{x}= \alpha_2(x),\quad\dot{y} = ky^2+\beta_1(x) y + \gamma_2(x), $$ with $(x,y)\in\mathbb{R}^2$, $\gamma_2(x)$ non-zero (otherwise the system is a Bernoulli differential system), $k\neq0$ (otherwise the system is a Lienard differential system), $\beta_ 1(x)$ a polynomial of degree at most $1$, $\alpha_ 2(x)$ and $\gamma_ 2(x)$ polynomials of degree at most 2, and the maximum of the degrees of $ \alpha_2(x)$ and $k y^2+\beta_1(x) y + \gamma_2(x)$ is 2. We give the complete description of their phase portraits in the Poincare disk