Electronic Journal of Differential Equations, Vol. 2024 (2024), No. 56, pp. 1-16. Title: Existence of global weak solution to tumor chemotaxis competition systems with loop and signal dependent sensitivity Authors: Shanmugasundaram Gnanasekaran (Easwari Engineeering College, Chennai, TN, India) Nagarajan Nithyadevi (Easwari Engineeering College, Chennai, TN, India) Abstract: This article examines the weak solution of a fully parabolic chemotaxis-competition system with loop and signal-dependent sensitivity. The system is subject to homogeneous Neumann boundary conditions within an open, bounded domain $\Omega\subset\mathbb{R}^n$, where $n\geq 1$ and $\partial\Omega$ is smooth. We assume that the parameters in the system are positive constants. Additionally, the initial data $(u_{10}, u_{20}, v_{10}, v_{20})\in L^2(\Omega)\times L^2(\Omega) \times W^{1,2}(\Omega)\times W^{1,2}(\Omega)$ are non-negative. The existence of a weak solution to the problem is established using energy inequality method. Submitted April 29, 2024. Published September 27, 2024. Math Subject Classifications: 35A01, 35D30, 92C17, 35Q92. Key Words: Chemotaxis system; two species and two stimuli; weak solution; Lotka-Volterra competition.