17217154
Reheating induced by competing decay modes
We address the problem of studying the decay of the inflaton field $\ensuremath{\phi}$ to another scalar field $\ensuremath{\chi}$ through parametric resonance in the case of a coupling that involves several decay modes. This amounts to the presence of extra harmonic terms in the perturbation of the $\ensuremath{\chi}$ field dynamics. For the case of two frequencies we compute the geometry of the resonance regions, which is significantly altered due to the presence of noncuspidal resonance regions associated to higher harmonics and to the emergence of instability ``pockets.'' We discuss the effect of this change in the efficiency of the energy transfer process for the simplest case of a coupling given by a combination of the two interaction terms of homogeneous degree usually considered in the literature. We find that the presence of higher harmonics has limited cosmological implications.
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.
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.
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.
119384671
Phase dynamics and particle production in preheating
We study a simple model of a massive inflaton field {phi} coupled to another scalar field {chi} with interaction term g{sup 2}{phi}{sup 2}{chi}{sup 2}. We use the theory developed by Kofman et al. [L. Kofman, A. D. Linde, and A. A. Starobinsky, Phys. Rev. D 56, 3258 (1997).] for the first stage of preheating to give a full description of the dynamics of the {chi} field modes, including the behavior of the phase, in terms of the iteration of a simple family of circle maps. The parameters of this family of maps are a function of time when expansion of the Universe is taken into account. With this more detailed description, we obtain a systematic study of the efficiency of particle production as a function of the inflaton field and coupling parameters, and we find that for g < or approx. 3x10{sup -4} the broad resonance ceases during the first stage of preheating.
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.
16429069
Control systems: An application to a high energy physics experiment (COMPASS)
The Detector Control System (DCS) of the COMPASS experiment at CERN is presented. The experiment has a high level of complexity and flexibility and a long time of operation, that constitute a challenge for its full monitorisation and control. A strategy to use a limited number of standardised, cost-effective, industrial solutions of hardware and software was pursued. When such solutions were not available or could not be used, customised solutions were developed.
55417521
Evolution of semilocal string networks: large-scale properties
We report on a detailed numerical study of the evolution of semilocal string networks, based on the largest and most accurate field theory simulations of these objects to date. We focus on the large-scale network properties, confirming earlier indications (coming from smaller simulations) that linear scaling is the attractor solution for the entire parameter space of initial conditions that we are able to probe. We also provide a brief comparison of our numerical results with the predictions of a previously developed one-scale model for the overall evolution of these networks. Two subsequent papers will discuss in more detail the analytic modeling of the semilocal segment populations as well as optimized numerical diagnostics.
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.
56668894
First results on $A_1^p$ and $g_1^p$ at low x and low $Q^2$ from COMPASS