The aim of this special issue is to focus on recent developments and achievements in the theory of function spaces, sequences spaces and their geometry, and compact operators and their applications in various fields of applied mathematics, engineering, and other sciences. The theory of sequence spaces is powerful tool for obtaining positive results concerning Schauder basis and plays a fundamental role in creating the basis of several investigations conducted in nonlinear analysis. The compactness is very often used in fixed point theory and its applications to the theories of differential, functional differential, integral, and integrodifferential equations.

We invite authors to submit original research and review articles describing the new methods and insights with some applications on the topics which are directly or indirectly related to function spaces, sequence spaces, operator theory, and approximation theory and applications. Potential topics include, but are not limited to:

• Longstanding open problems in geometry of Banach spaces
• Schauder basis and dual spaces
• Approximation of positive linear operators by matrix and nonmatrix methods
• Measures of noncompactness and their applications in characterizing compact matrix operators
• Applications in fixed point, differential, and integrodifferential equations on sequence spaces and function spaces
• Solvability of infinite system of differential equations in sequence spaces via measures of noncompactness

Before submission authors should carefully read over the journal’s Author Guidelines, which are located at http://www.hindawi.com/journals/tswj/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/submit/journals/tswj/mathematical.analysis/ssco/ according to the following timetable: