STABILITY ANALYSIS AND HOPF BIFURCATION OF DENSITY-DEPENDENT PREDATOR-PREY SYSTEMS WITH BEDDINGTON-DEANGELIS FUNCTIONAL RESPONSE

In this article, we study a density-dependent predator-prey system with the Beddington-DeAngelis functional response for stability and Hopf bifurcation under certain parametric conditions. We start with the condition of the existence of the unique positive equilibrium, and provide two sufficient conditions for its local stability by the Lyapunov function method and the Routh-Hurwitz criterion, respectively. Then, we establish sufficient conditions for the global stability of the positive equilibrium by proving the non-existence of closed orbits in the first quadrant R²+. Afterwards, we analyze the Hopf bifurcation geometrically by exploring the monotonic property of the trace of the Jacobean matrix with respect to r and analytically verifying that there is a unique r* such that the trace is equal to 0. We also introduce an auxiliary map by restricting all the five parameters to a special one-dimensional geometrical structure and analyze the Hopf bifurcation with respect to all these five parameters. Finally, some numerical simulations are illustrated which are in agreement with our analytical results

A Note on the Existence of a Smale Horseshoe in the Planar Circular Restricted Three-Body Problem

It has been proved that, in the classical planar circular restricted three-body problem, the degenerate saddle point processes transverse homoclinic orbits. Since the standard Smale-Birkhoff theorem cannot be directly applied to indicate the chaotic dynamics of the Smale horseshoe type, we in this note alternatively apply the Conley-Moser conditions to analytically prove the existence of a Smale horseshoe in this classical restricted three-body problem

A SEMI-ALGEBRAIC APPROACH FOR THE COMPUTATION OF LYAPUNOV FUNCTIONS

In this paper we deal with the problem of computing Lyapunov functions for stability verification of differential systems. We concern on symbolic methods and start the discussion with a classical quantifier elimination model for computing Lyapunov functions in a given polynomial form, especially in quadratic forms. Then we propose a new semi-algebraic method by making advantage of the local property of the Lyapunov function as well as its derivative. This is done by first using real solution classification to construct a semi-algebraic system and then solving this semi-algebraic system. Our semi-algebraic approach is more efficient in practice, especially for low-order systems. This efficiency will be evaluated empirically

Providing a basin of attraction to a target region by computation of Lyapunov-like functions

Abstract — In this paper, we present a method for computing a basin of attraction to a target region for non-linear ordinary differential equations. This basin of attraction is ensured by a Lyapunov-like polynomial function that we compute using an interval based branch-and-relax algorithm. This algorithm relaxes the necessary conditions on the coefficients of the Lyapunov-like function to a system of linear interval inequalities that can then be solved exactly, and iteratively reduces the relaxation error by recursively decomposing the state space into hyper-rectangles. Tests on an implementation are promising. I

A density-dependent predator-prey model of Beddington-DeAngelis type

In this article, we study the dynamics of a density-dependent predator-prey system of Beddington-DeAngelis type. We obtain sufficient and necessary conditions for the existence of a unique positive equilibrium, the global attractiveness of the boundary equilibrium, and the permanence of the system, respectively. Moreover, we derive a sufficient condition for the locally asymptotic stability of the positive equilibrium by the Lyapunov function theory and a sufficient condition for the global attractiveness of the positive equilibrium by the comparison theory

Safety verification of hybrid systems by constraint propagation based abstraction refinement

Abstract. This paper deals with the problem of safety verification of non-linear hybrid systems. We start from a classical method that uses interval arithmetic to check whether trajectories can move over the boundaries in a rectangular grid. We put this method into an abstraction refinement framework and improve it by developing an additional refinement step that employs constraint propagation to add information to the abstraction without introducing new grid elements. Moreover, the resulting method allows switching conditions, initial states and unsafe states to be described by complex constraints instead of sets that correspond to grid elements. Nevertheless, the method can be easily implemented since it is based on a well-defined set of constraints, on which one can run any constraint propagation based solver. First tests of such an implementation are promising.

Recursive and Backward Reasoning in the Verification on Hybrid Systems ⋆

Abstract. In this paper we introduce two improvements to the method of verification of hybrid systems by constraint propagation based abstraction refinement that we introduced earlier. The first improvement improves the recursive propagation of reachability information over the regions constituting the abstraction, and the second improvement reasons backward from the set of unsafe states, instead of forward from the safe of initial states. Detailed computational experiments document the usefulness of these improvements.