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Kumarasamy Sakthivel

Publications and source records attributed to Kumarasamy Sakthivel.

3 recordsLinked to original sources

Strong Solutions for the Stochastic Cahn-Hilliard Convective Brinkman-Forchheimer Model for Tumor Growth

In this work, we analyze a diffuse-interface model for tumor growth, subject to multiplicative white noises, posed on a bounded domain $\mathcal{O} \subset \mathbb{R}^d$, $d=2,3$. The model couples a stochastic incompressible convective Brinkman-Forchheimer (CBF) equation or Navier-Stokes equation with damping $\eta|v|^{r-1}v $ for the averaged velocity field $v$, to a Cahn-Hilliard (CH) equation for the phase field variable $\phi$ and to a stochastic reaction-diffusion equation governing the nutrient concentration $\sigma$. We establish the existence of local strong solutions , for $ r \geq 1 $ in $d=2$ and $ r \in [1,3] $ in $d=3$. We prove the weak-strong uniqueness holds in both $d = 2, 3$. In addition, for $d = 2$, the uniqueness of weak solutions is obtained for all $\eta,\nu > 0$, and $r \geq 1$, while it holds in $d = 3$ for $r \geq 3$ and $\eta \nu \geq 1$ when $r = 3$ under an assumption on $\sigma$. Moreover, for $d=2$ and $r \in [1,3]$, we obtain that the strong solution exists globally in time.

math.AP

Time Optimal Control Problem for the Landau-Lifshitz-Bloch equation

This paper investigates the time-optimal control problem for the Landau-Lifshitz-Bloch (LLB) equation, a macroscopic model that characterizes magnetization dynamics in ferromagnetic materials across a wide temperature range, including near and above the Curie temperature. We analyze the LLB system on bounded domains in one, two, and three dimensions, establishing the existence of optimal controls that drive the magnetization to a desired target state within a minimal time frame. Utilizing a Lagrange multiplier approach and an adjoint-based framework, we derive first-order necessary optimality conditions. Furthermore, we establish second-order sufficient conditions for local optimality, addressing the mathematical challenges posed by the system's inherent nonlinearities and the nonlinear appearance of the control in the effective magnetic field. These results provide a rigorous theoretical basis for the rapid manipulation of magnetic states, offering insights into the fundamental limits of control for nonlinear diffusion-relaxation processes in magnetism. Such findings are essential for advancing high-speed magnetic memory technologies and optimizing thermal magnetic switching in next-generation storage technologies.

math.OC

Magnetization control problem for the 2D and 3D evolutionary Landau-Lifshitz-Bloch equation

In this study, we investigate the optimal control of the Landau-Lifshitz-Bloch equation within confined domains in $\mathbb R^n$ for $n= 2, 3.$ We establish the existence of strong solutions for dimensions $n=1, 2, 3$ under suitable growth conditions on the control, and analyze the existence and uniqueness of regular solutions. We formulate the control problem in which only a fixed set of finite magnetic field coils can constitute the external magnetic field (control). We define a cost functional by aiming at minimizing the energy discrepancy between the evolving magnetic moment and the desired state. We demonstrate the existence of an optimal solution pair and employ the classical adjoint problem approach to derive a first-order necessary optimality condition. Given the non-convex nature of the optimal control problem, we derive a second-order sufficient optimality condition using a cone of critical directions. Finally, we prove two crucial results, namely, a global optimality condition and uniqueness of an optimal control.

math.OC