Using the Hubble parameter as new ‘inverse time’ coordinate (H-formalism), a new method of reconstructing the inflaton potential is developed also using older results which, in principle, is applicable to any order of the slow-roll approximation. In first and second order, we need three observational data as inputs: the scalar spectral index ns and the amplitudes of the scalar and the tensor sp...

We investigate cosmological evolutions of the bulk scalar field φ(t) and the radion d(t) in five-dimensional dilatonic two branes model. The bulk potential for the scalar field is taken as the exponential function Vbulk ∝ exp(−2 √ 2bφ), where b is the parameter of the theory. This model includes Randall-Sundrum model (with b = 0) and fivedimensional Hořava-Witten theory (with b = 1). We conside...

The most general combination of couplings of fermions with external potentials in 1+1 dimensions, must include vector, scalar and pseudoscalar potentials. We consider such a mixing of potentials in a PT-symmetric time-independent Dirac equation. The Dirac equation is mapped into an effective PT-symmetric Schrödinger equation. Despite the non-hermiticity of the effective potential, we find real ...

The cosmological evolution in Nonlinear Born-Infeld(hereafter NLBI) scalar field theory with negative potentials was investigated. The cosmological solutions in some important evolutive epoches were obtained. The different evolutional behaviors between NLBI and linear scalar field theory have been presented. A notable characteristic is that NLBI scalar field behaves as ordinary matter nearly th...

The cosmological evolution in Nonlinear Born-Infeld(hereafter NLBI) scalar field theory with negative potentials was investigated. The cosmological solutions in some important evolutive epoches were obtained. The different evolutional behaviors between NLBI and linear scalar field theory have been presented. A notable characteristic is that NLBI scalar field behaves as ordinary matter nearly th...

The cosmological evolution in Nonlinear Born-Infeld(hereafter NLBI) scalar field theory with negative potentials was investigated. The cosmological solutions in some important evolutive epoches were obtained. The different evolutional behaviors between NLBI and linear scalar field theory have been presented. A notable characteristic is that NLBI scalar field behaves as ordinary matter nearly th...

The cosmological evolution in Nonlinear Born-Infeld(hereafter NLBI) scalar field theory with negative potentials was investigated. The cosmological solutions in some important evolutive epoches were obtained. The different evolutional behaviors between NLBI and linear(canonical) scalar field theory have been presented. A notable characteristic is that NLBI scalar field behaves as ordinary matte...

We study the eigenvectors of the renormalization-group matrix for scalar fields at the Gaussian fixed point, and find that that there exist “relevant” directions in parameter space. They correspond to theories with exponential potentials that are nontrivial and asymptotically free. All other potentials, including polynomial potentials, are “irrelevant,” and lead to trivial theories. Away from t...

We consider Friedmann cosmologies with minimally coupled scalar field. Exact solutions are found, many of them elementary, for which the scalar field energy density, ρf , and pressure, pf , obey the equation of state (EOS) pf = wfρf . For any constant |wf | < 1 there exists a two-parameter family of potentials allowing for such solutions; the range includes, in particular, the quintessence (−1 ...

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 related features have also been discovered f...