• Few-body physics
• Nuclear physics
• Numerical solutions
• Universality

Universality in physics refers to the particular case in which systems with completely different internal structure exhibit the same behavior under some simplifying assumptions. The unitary limit is completely defined by looking at the scattering behavior of the two-body system. The most important parameter governing the low-energy scattering behavior of the system is the S-wave scattering length, which diverges at the unitary limit. Around the unitary limit different systems show universal features independently of their short-distance structure. The most strikingly evidence of universality comes in three-body spinless systems at the unitary limit, these systems have an infinite number of bound states with binding energies showing a geometrical spectrum with an accumulation point at zero energy, these features are known as the Efimov effect. In this thesis we studied the universality in general few-body systems, even though this concept can be studied in different field of physics we focalized on applications to nuclear and atomic physics. Accordingly we solved the Schrodinger equation for the lowest hypespherical harmonic channel for general few-bosons systems using Gaussian two-body interactions. We introduced Gaussian interactions as effective potentials able to capture accurately the low-energy behavior of all the systems around the unitary limit. We studied in detail the three-body problem using both a Gaussian and a zero-range interaction. In the latter case we managed to show the appearance of the Thomas and Efimov effect and by regularizing the interaction at short-distances we studied how different regularization schemes influence the universal Efimov behavior.