## New Math Series: Selected Topics in Functional Analysis

This series of study notes is aimed for post-graduate (M.A/M.Sc.) students of Indian & international universities. The study of functional analysis can be started after basic topology and set theory courses. In this introductory article we will start with some elementary yet important definitions and notations from analysis. We will finish this article with the definition of Norm & Normed Linear spaces derivedfrom the notions of linear spaces. An elementary treatise of examples and their completeness of Normed (linear) Spaces will…

## Solving Integral Equations (2) – Square Integrable Functions, Norms, Trial Method

Square Integrable function or quadratically integrable function $\mathfrak{L}_2$ function A function $y(x)$ is said to be square integrable or $\mathfrak{L}_2$ function on the interval $(a,b)$ if $$\displaystyle {\int_a^b} {|y(x)|}^2 dx <\infty$$ or $$\displaystyle {\int_a^b} y(x) \bar{y}(x) dx <\infty$$. For further reading, I suggest this Wikipedia page. $y(x)$ is then also called 'regular function'. The kernel $K(x,t)$ , a function of two variables is an $\mathfrak{L_2}$ - function if atleast one of the following is true: $\int_{x=a}^b \int_{t=a}^b |K(x,t)|^2 dx dt <\infty$ \$\int_{t=a}^b |K(x,t)|^2 dx…