We discuss applications of nonlinearly realized supersymmetry to string theoretical and cosmological model buildings. One is the effective description of an D3 brane in superstring theory. An D3 brane plays an important role in realizing de Sitter vacuum within superstring models, such as KKLT model. We will show that its effective action including world volume excitations and their couplings to bulk moduli fields is described by nonlinear supergravity. Another application of nonlinear supergravity is Horndeski model in supergravity. Horndeski model, which does not have ghost instability, can describe a broad class of single-field inflation models.
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