On Topological Defects and Cosmological Constant

Einstein introduced Cosmological Constant in his field equations in an ad hoc manner. Cosmological constant plays the role of vacuum energy of the universe which is responsible for the accelerating expansion of the universe. To give theoretical support it remains an elusive goal to modern physicists. We provide a prescription to obtain cosmological constant from the phase transitions of the early universe when topological defects, namely monopole might have existed.