Cosmological Backgrounds of Gravitational Waves and eLISA
  We review cosmological backgrounds of gravitational waves with a particular
attention to the scientific potential of the eLISA/NGO mission. After an
overview of cosmological backgrounds and detectors, we consider different
cosmological sources that could lead to an observable signal. We then study the
backgrounds produced by first-order phase transitions and networks of cosmic
strings, assessing the prospects for their detection.
