Open Inflationary Universes in the Induced Gravity Theory

The induced gravity theory is a variant of Jordan--Brans--Dicke theory where the `dilaton' field possesses a potential. It has the unusual feature that in the presence of a false vacuum there is a {\em stable} static solution with the dilaton field displaced from the minimum of its potential, giving perfect de Sitter expansion. We demonstrate how this solution can be used to implement the open inflationary universe scenario. The necessary second phase of inflation after false vacuum decay by bubble nucleation is driven by the dilaton rolling from the static point to the minimum of its potential. Because the static solution is stable whilst the false vacuum persists, the required evolution occurs for a wide range of initial conditions. As the exterior of the bubble is perfect de Sitter space, there is no problem with fields rolling outside the bubble, as in one of the related models considered by Linde and Mezhlumian, and the expansion rates before and after tunnelling may be similar which prevents problematic high-amplitude super-curvature modes from being generated. Once normalized to the microwave background anisotropies seen by the COBE satellite, the viable models form a one-parameter family for each possible $\Omega_0$.Comment: 7 pages RevTeX file with three figures incorporated (uses RevTeX and epsf). Also available by e-mailing ARL, or by WWW at http://star-www.maps.susx.ac.uk/papers/early_papers.htm

Symmetric vacuum scalar--tensor cosmology

The existence of point symmetries in the cosmological field equations of generalized vacuum scalar--tensor theories is considered within the context of the spatially homogeneous cosmologies. It is found that such symmetries only occur in the Brans--Dicke theory when the dilaton field self--interacts. Moreover, the interaction potential of the dilaton must take the form of a cosmological constant. For the spatially flat, isotropic model, it is shown how this point symmetry may be employed to generate a discrete scale factor duality in the Brans--Dicke action.Comment: 10 pages, latex, To appear in Class. Quantum Gra

Utilização do adesivo a base de cianoacrilato na síntese do coto brônquico após lobectomia pulmonar em cães (Canis familiaris)

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Galactic periodicity and the oscillating G model

We consider the model involving the oscillation of the effective gravitational constant that has been put forward in an attempt to reconcile the observed periodicity in the galaxy number distribution with the standard cosmological models. This model involves a highly nonlinear dynamics which we analyze numerically. We carry out a detailed study of the bound that nucleosynthesis imposes on this model. The analysis shows that for any assumed value for $\Omega$ (the total energy density) one can fix the value of $\Omega_{\rm bar}$ (the baryonic energy density) in such a way as to accommodate the observational constraints coming from the $^4{\rm He}$ primordial abundance. In particular, if we impose the inflationary value $\Omega=1$ the resulting baryonic energy density turns out to be $\Omega_{\rm bar}\sim 0.021$. This result lies in the very narrow range $0.016 \leq \Omega_{\rm bar} \leq 0.026$ allowed by the observed values of the primordial abundances of the other light elements. The remaining fraction of $\Omega$ corresponds to dark matter represented by a scalar field.Comment: Latex file 29 pages with no figures. Please contact M.Salgado for figures. A more careful study of the model appears in gr-qc/960603

Finite Temperature and Density Effect on Symmetry Breaking by Wilson Loops

A finite temperature and density effect of Wilson loop elements on non-simply connected space is investigated in the model suggested by Hosotani. Using one-loop calculations it is shown that the value of an "order parameter" does not shift as the temperature grows. We find that finite density effect is of much importance for restoration of symmetry.Comment: 11pages, no figur

Bianchi I Quantum cosmology in the Bergmann-Wagoner theory

The Wheeler-DeWitt equation is considered in the context of generalized scalar-tensor theories of gravitation for Bianchi type I cosmology. Exact solutions are found for two selfinteracting potentials and arbitary coupling function. The WKB wavefunctions are obtained and a family of solutions satisfying the Hawking-Page regularity conditions of wormholes are found.Comment: 12 pages, Latex fil

Constraints in the Context of Induced-gravity Inflation

Constraints on the required flatness of the scalar potential $V(\phi)$ for a cousin-model to extended inflation are studied. It is shown that, unlike earlier results, Induced-gravity Inflation can lead to successful inflation with a very simple lagrangian and $\lambda \sim 10^{-6}$, rather than $10^{-15}$ as previously reported. A second order phase transition further enables this model to escape the \lq big bubble' problem of extended inflation, while retaining the latter's motivations based on the low-energy effective lagrangians of supergravity, superstring, and Kaluza-Klein theories.Comment: 19 pp; 3 figures (not included -- available from author). Plain LaTeX. In press in Physical Review

Complete power spectrum for an induced gravity open inflation model

We study the phenomenological constraints on a recently proposed model of open inflation in the context of induced gravity. The main interest of this model is the relatively small number of parameters, which may be constrained by many different types of observation. We evaluate the complete spectrum of density perturbations, which contains continuum sub-curvature modes, a discrete super curvature mode, and a mode associated with fluctuations in the bubble wall. From these, we compute the angular power spectrum of temperature fluctuations in the microwave background, and derive bounds on the parameters of the model so that the predicted spectrum is compatible with the observed anisotropy of the microwave background and with large-scale structure observations. We analyze the matter era and the approach of the model to general relativity. The model passes all existing constraints.Comment: 12 pages RevTeX file with four figures incorporated (uses RevTeX and epsf). Also available by e-mailing ARL, or by WWW at http://star-www.maps.susx.ac.uk/papers/early_papers.html Only change is additional reference