119519761
SCALAR FIELD PHASE DYNAMICS IN PREHEATING
We study the model of a massive inflaton field $\phi$ coupled to another scalar filed $\chi$ with interaction term $g^2\phi^2\chi^2$ for the first stage of preheating. We obtain the the behavior of the phase in terms of the iteration of a simple family of circle maps. When expansion of the universe is taken into account the qualitative behavior of the phase and growth number evolution is reminiscent of the behavior found in the case without expansion.
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.
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.
119090338
On the potentials yielding cosmological scaling solutions
In the present work we perform a phase-plane analysis of the complete dynamical system corresponding to a flat FRW cosmological models with a perfect fluid and a self-interacting scalar field and show that every positive and monotonous potential which is asymptotically exponential yields a scaling solution as a global attractor.
119448124
BULK VISCOSITY IMPACT ON THE SCENARIO OF WARM INFLATION
The decay of the inflaton into radiation and particles during the slow-roll suggests that these may interact with each other and that the latter may also decay into subproducts before inflation is completed. As a consequence, the fluid is no longer perfect and a nonnegligible bulk viscosity necessarily sets in. We write the corresponding equations as an autonomous system and study the asymptotic behavior, the conditions for the existence of scaling solutions, and show that the late time effect of fluid dissipation 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.
118504596
Longitudinal double spin asymmetry $A_1^p$ and spin-dependent structure function $g_1^p$ of the proton at low $x$ and low $Q^2$ from COMPASS
The COMPASS experiment at CERN has collected a large sample of events of inelastic scattering of longitudinally polarised muons off longitudinally polarised protons in the non-perturbative region (four-momentum transfer squared $Q^2<1$ GeV$^2$/$c^2$), with a Bjorken scaling variable in the range $4\times 10^{-5}<x<4\times 10^{-2}$. The data set is two orders of magnitude larger than the similar sample collected by the SMC experiment. These data complement our data for polarised deuterons. They allow the accurate determination of the longitudinal double spin asymmetry $A_1^p$ and of the spin-dependent structure function $g_1^p$ of the proton in the region of low $x$ and low $Q^2$. The preliminary results of the analysis of these data yield non zero and positive asymmetries and of the structure function $g_1^p$. This is the first time that spin effects are observed at such low $x$.
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.
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.