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Scalar field theory has become the generic playground for building cosmological models related to particle physics, in particular for obtaining inflationary cosmologies. One such class of models involves exponential potentials @exp(A16p/pmPl 2 f)# , which lead to power law inflation, a }t, with p.1, for sufficiently flat potentials @1–3#. A number of… (More)

Tiago Barreiro,* Beatriz de Carlos, Ed Copeland, and Nelson J. Nunes4,x Centro Multidisciplinar de Astrofı́sica (CENTRA), Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QJ, United Kingdom The School of Physics and Astronomy,… (More)

- N. J. Nunes
- 1999

Measurements of the redshift-luminosity distance relation using high redshift type Ia supernovas combined with cosmic microwave background ~CMB! and galaxy clusters data appear to suggest that the present Universe is flat and undergoing a period of L driven inflation, with the energy density split into two main contributions, Vmatter'1/3 and VL'2/3 @1–3#.… (More)

- Alain Coc, Nelson J. Nunes, Keith A. Olive, Jean-Philippe Uzan, Elisabeth Vangioni
- 2006

The effect of variations of the fundamental nuclear parameters on big-bang nucleosynthesis are modeled and discussed in detail taking into account the interrelations between the fundamental parameters arising in unified theories. Considering only He, strong constraints on the variation of the neutron lifetime, neutron-proton mass difference are set. These… (More)

- N. J. Nunes
- 2008

We investigate how inhomogeneous quintessence models may have a specific signature even in the linear regime of large scale structure formation. The dynamics of the collapse of a dark matter halo is governed by the value or the dynamical evolution of the dark energy equation of state, the energy density’s initial conditions and its homogeneity nature in the… (More)

Cosmology of self-interacting three-forms is investigated. The minimally coupled canonical theory can naturally generate a variety of isotropic background dynamics, including scaling, possibly transient acceleration and phantom crossing. An intuitive picture of the cosmological dynamics is presented employing an effective potential. Numerical solutions and… (More)

Several cosmological observations appear to suggest that the present Universe is dominated by an unknown form of energy with negative pressure, acting as an effective cosmological constant Λ. CMB and cluster distribution data, when combined with the measurements of the redshift–luminosity relation using high redshift type Ia supernovae, single out a flat… (More)

Scalar fields play a central role both in particle physics and cosmology. For example, in the Standard Model of particle physics, the Higgs boson generates particle masses through a mechanism of symmetry breaking. Supersymmetric models, believed to solve the hierarchy problem and to suggest a grand unification scale, add a whole new set of scalar (and… (More)

- N. J. Nunes
- 2005

The evolution of a scalar field is explored taking into account the presence of a background fluid in a positively curved Universe in the framework of loop quantum cosmology. Though the mechanism that provides the initial conditions for inflation extensively studied in the literature, is still available in this setup, it demands that the initial kinetic… (More)

In the simple case of a constant equation of state, redshift distribution of collapsed structures may constrain dark energy models. Different dark energy models having the same energy density today but different equations of state give quite different number counts. Moreover, we show that introducing the possibility that dark energy collapses with dark… (More)