5. Theoretical Physics (CSN4)
# An effective theory of quintessence perturbations (by Jorge Norena)

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by

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Europe/Rome

Aula Seminari (Laboratori Nazionali di Frascati)
### Aula Seminari

#### Laboratori Nazionali di Frascati

Description

An appealing alternative to the cosmological constant to explain the
accelerated expansion of the universe is quintessence, in which the
expansion of the universe becomes dominated at late times by a scalar
field. We perform a general analysis in the spirit of effective theories of
the
perturbations of a quintessence field, thus studying the theoretical
constraints on the parameter space. In particular, we argue that an
equation of state of the form $p = w\rho$ (where $p$ and $\rho$ are,
respectively, the effective pressure and energy density of quintessence)
with $w < -1$ can be attained by a single scalar field without the
theoretical inconsistencies of the models involving a ghost, and show that
it is possible to formulate models that evolve through $w = -1$,
differently with what is usually stated in the literature.