115768541
How general is inflation in the presence of a non-minimal coupling?
Abstract The qualitative analysis of a Robertson-Walker geometry non-minimally coupled to a scalar field is summarized. It is claimed that a divergenceless effective energy-momentum tensor should be used. In this case, the conformal coupling (ξ= 1 6 ) corresponds to the minimum value of the x -coordinate of a singular line in phase space. To analyse the generality of the occurrence of inflation we calculate the measure of the set of the initial conditions of the solutions leading to a final dust state. We conclude that there is inflation for a wide range of values of ξ.
18454632
Scaling solutions from interacting fluids
We examine the dynamical implications of an interaction between some of the fluid components of the universe. We consider the combination of three matter components, one of which is a perfect fluid and the other two are interacting. The interaction term generalizes the cases found in scalar field cosmologies with an exponential potential. We find that attracting scaling solutions are obtained in several regions of parameter space, that oscillating behaviour is possible, and that new curvature scaling solutions exist. We also discuss the inflationary behaviour of the solutions and present some of the constraints on the strength of the coupling, namely those arising from nucleosynthesis.
118523307
Scaling Behavior in Warm Inflation
We analyze the dynamics of warm inflation models with general viscous effects. We characterize the situations yielding asymptotic scaling behavior.
5580802
Asymptotic behavior of the warm inflation scenario with viscous pressure
We analyze the dynamics of models of warm inflation with general dissipative effects. We consider phenomenological terms both for the inflaton decay rate and for viscous effects within matter. We provide a classification of the asymptotic behavior of these models and show that the existence of a late-time scaling regime depends not only on an asymptotic behavior of the scalar field potential, but also on an appropriate asymptotic behavior of the inflaton decay rate. There are scaling solutions whenever the latter evolves to become proportional to the Hubble rate of expansion regardless of the steepness of the scalar field exponential potential. We show from thermodynamic arguments that the scaling regime is associated to a power-law dependence of the matter-radiation temperature on the scale factor, which allows a mild variation of the temperature of the matter/radiation fluid. We also show that the late time contribution of the dissipative terms alleviates the depletion of matter, and increases the duration of inflation.
121292064
General relativity as a cosmological attractor of scalar-tensor gravity theories
Abstract We investigate the relaxation of general scalar-tensor gravity theories towards general relativity. We extend Damour and Nordtvedt's work [Phys. Rev. Lett. 70 (1993) 2217; Phys. Rev. D 48 (1993) 3436] by including a cosmological potential. We find that Einstein's gravity is indeed a cosmological attractor both for isotropic and anisotropic universes, and that the universe exhibits inflationary expansion during the relaxation process.
119102186
Slow roll inflation without fine tuning
Abstract The slow-roll approximation is the usual starting point to study the constraints imposed on the inflaton potential parameters by the observational data. We show that, for a potential exhibiting at least two extrema and giving rise to a limited inflationary period, slow-roll does not have to be taken as an additional hypothesis and is in fact forced by the constraints on the number of e-foldings.
118474758
Analytic models for the evolution of semilocal string networks
We revisit previously developed analytic models for defect evolution and adapt them appropriately for the study of semilocal string networks. We thus confirm the expectation (based on numerical simulations) that linear scaling evolution is the attractor solution for a broad range of model parameters. We discuss in detail the evolution of individual semilocal segments, focusing on the phenomenology of segment growth, and also provide a preliminary comparison with existing numerical simulations.
121568899
Dispersion relations for polarization operator of a photon in an external non-Abelian field
The thresholds for photoproduction of scalar quarks in an external non-Abelian field are determined. A dispersion relation is obtained for the trace of the photon polarization operator with internal quark loop in this field. The explicit form of the trace is calculated by means of this relation.
56668894
First results on $A_1^p$ and $g_1^p$ at low x and low $Q^2$ from COMPASS
115300255
On the theory of the invisible arion
Models with an ''invisible'' arion, a massless Goldstone particle interacting weakly with quarks and leptons, are considered. The coupling constant with photons, which is needed for the occurrence of arion--photon oscillations in an external magnetic field, is estimated.
8883252
Observation of a New Narrow Axial-Vector Meson a1(1420).
The COMPASS Collaboration at CERN has measured diffractive dissociation of 190  GeV/c pions into the π(-)π(-)π(+) final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of 3π mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow peak is observed in the f0(980)π channel with spin, parity and C-parity quantum numbers J(PC)=1(++). We present a resonance-model study of a subset of the spin-density matrix selecting 3π states with J(PC)=2(++) and 4(++) decaying into ρ(770)π and with J(PC)=1(++) decaying into f0(980)π. We identify a new a1 meson with mass (1414(-13)(+15))  MeV/c2 and width (153(-23)(+8))  MeV/c2. Within the final states investigated in our analysis, we observe the new a1(1420) decaying only into f0(980)π, suggesting its exotic nature.