  In this thesis, we investigate hidden symmetries for the Maldacena-Wilson
loop in N=4 super Yang-Mills theory, mainly focusing on its strong-coupling
description as a minimal surface in $AdS_5$. In the discussion of the symmetry
structure of the underlying string model, we highlight the role of the master
symmetry which can be employed to construct all symmetries of the model. The
algebra of these symmetries is worked out. For the concrete case of minimal
surfaces in $AdS_5$, we discuss the deformation of the four-cusp solution,
which provides the dual description of the four-gluon scattering amplitude.
This marks the first step toward transferring the master symmetry to scattering
amplitudes. Moreover, we compute the master and Yangian symmetry variations of
generic, smooth boundary curves. The discussion clarifies why previous attempts
to transfer the deformations of minimal surfaces in $AdS_3$ to weak coupling
were unsuccessful. We discuss several attempts to transfer the Yangian symmetry
to weak or arbitrary coupling, but ultimately conclude that a Yangian symmetry
of the Maldacena-Wilson loop seems not to be present. This is different for the
natural supersymmetric generalizations of the Maldacena--Wilson loop, Wilson
loops in superspace. Their one-loop expectation value is known to be Yangian
invariant. We discuss the strong-coupling counterpart of this finding by
considering minimal surfaces in the superspace of type IIB superstring theory
in $AdS_5 \times S^5$. The comparison of the strong-coupling invariance derived
here with the weak-coupling generators shows that the local term must depend on
the coupling in a non-trivial way. Additionally, we show that the higher-level
recurrences of the hypercharge generator, the so-called bonus symmetries, are
present in all higher levels of the Yangian.

High Energy Physics - Theory