Observations have shown that solar-like oscillations can be excited in red giant stars. Nevertheless, these stars are very different from main sequence stars. For instance, they present a great density contrast between a dense core and an extended envelope, they have a hydrogen-burning shell, and they are brighter which implies that they are expected to have larger amplitudes. Thus, they have proven to be worthy of asteroseismic investigation and, indeed, space missions as CoRoT have proposed to observe them. Therefore, being able to model red giants is important. When modelling red giants, one faces some extra difficulties which are not present or are not so prominent in main sequence stars modelling, such as the free parameters in the convection and in the semi-convection treatments. The non radial modes in red giants also behave differently from the non radial modes in main sequence stars. We will describe their main oscillatory properties and analyze their stability for the case of a 3M{sub}⊙ model in central He-burning phase. We conclude that the inertia of the modes plays the most important role in their stability.
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