A revisit via slicing method on a quadratic semilinear wave equation in two space dimensions

In this paper, we are focusing on the proof of the blow-up result for a quadratic semilinear wave equation in two space dimensions. There is a logarithmic loss in estimating the lifespan of classical solutions if the 0th moment of the initial speed does not vanish. This result is already known with almost sharp constants. But in order to have a direct application to numerical analysis, we show a simple proof by iteration argument of point-wise estimate of the solution with the slicing technique.