The anomaly-induced effective action and natural inflation

The anomaly-induced inflation (modified Starobinsky model) is based on the application of the effective quantum field theory approach to the Early Universe. We present a brief general review of the model and show that it does not require a fine-tuning for the parameters of the theory or initial data, gives a real chance to meet a graceful exit to the FRW phase and also has positive features with respect to the metric perturbations.Comment: Invited talk at the International Workshop on Astroparticle and High Energy Physics, October 14 - 18, 2003, Valencia, Spai

Dark energy perturbations and cosmic coincidence

While there is plentiful evidence in all fronts of experimental cosmology for the existence of a non-vanishing dark energy (DE) density \rho_D in the Universe, we are still far away from having a fundamental understanding of its ultimate nature and of its current value, not even of the puzzling fact that \rho_D is so close to the matter energy density \rho_M at the present time (i.e. the so-called "cosmic coincidence" problem). The resolution of some of these cosmic conundrums suggests that the DE must have some (mild) dynamical behavior at the present time. In this paper, we examine some general properties of the simultaneous set of matter and DE perturbations (\delta\rho_M, \delta\rho_D) for a multicomponent DE fluid. Next we put these properties to the test within the context of a non-trivial model of dynamical DE (the LXCDM model) which has been previously studied in the literature. By requiring that the coupled system of perturbation equations for \delta\rho_M and \delta\rho_D has a smooth solution throughout the entire cosmological evolution, that the matter power spectrum is consistent with the data on structure formation and that the "coincidence ratio" r=\rho_D/\rho_M stays bounded and not unnaturally high, we are able to determine a well-defined region of the parameter space where the model can solve the cosmic coincidence problem in full compatibility with all known cosmological data.Comment: Typos correcte

Inflation without inflatons

(abridged)We present a model which predicts inflation without the presence of inflaton fields, based on the \epsilon R^2 and Starobinsky models. It links the above models to the observable universe, in particular, to the ratio r of tensor to scalar fluctuations. In our model, we assume the existence of particles with the mass M that have a long decay time. These particles which were gravitationally produced \sim 60e-folds before the end of inflation produced the nearly scale invariant scalar density fluctuations which are observed. Gravitational waves (tensor fluctuations) were also produced at this epoch. The ratio of tensor to scalar fluctuations r (which are to be measured in the near future to good accuracy) determines M, which together with H_0, determine the time at the end of inflation, t_end. At t_end, the Hubble parameter begins to oscillate rapidly, gravitationally producing the bulk of the M particles, which we identify with the matter content of the universe today. The time required for the universe to dissipate its vacuum energy into M particles is found to be t_dis \simeq 6M_Pl^2/M^3. We assume that the time t_RH, (called the reheating time) needed for the M particles to decay into relativistic particles, is very much greater than that necessary to create the M particles, t_dis. From the ratio f\equiv t_dis/t_RH and g_\ast (the total number of degrees of freedom of the relativistic particles) we can, then, evaluate the maximum temperature of the universe, T_max, and the reheat temperature, T_RH, at t_RH. Our model, thus, predicts M, t_dis, t_end, T_max, T_RH, t_max, and t_RH as a function of r, f, and g_\ast (and to a weaker extent the particle content of the vacuum near the Planck epoch).Comment: 11 pages, 2 figures. Revised version, accepted for publication in Phys. Rev.

Renormalization Group and Decoupling in Curved Space: II. The Standard Model and Beyond

We continue the study of the renormalization group and decoupling of massive fields in curved space, started in the previous article and analyse the higher derivative sector of the vacuum metric-dependent action of the Standard Model. The QCD sector at low-energies is described in terms of the composite effective fields. For fermions and scalars the massless limit shows perfect correspondence with the conformal anomaly, but similar limit in a massive vector case requires an extra compensating scalar. In all three cases the decoupling goes smoothly and monotonic. A particularly interesting case is the renormalization group flow in the theory with broken supersymmetry, where the sign of one of the beta-functions changes on the way from the UV to IR.Comment: 27 pages, 8 figure

Evolução da maturação e características físicoquímicas da videira "BRS Vitória" em diferentes épocas de poda.

Na região noroeste paulista são realizadas duas podas no mesmo ano, a primeira de produção, realizada de fevereiro a junho, e a segunda para formação, realizada entre junho a novembro. O período de colheita se estende de julho a novembro, diferentemente de outras regiões produtoras, o que beneficia os produtores na comercialização da uva

Cosmic perturbations with running G and Lambda

Cosmologies with running cosmological term (Lambda) and gravitational Newton's coupling (G) may naturally be expected if the evolution of the universe can ultimately be derived from the first principles of Quantum Field Theory or String Theory. In this paper, we derive the general cosmological perturbation equations for models with variable G and Lambda in which the fluctuations in both variables are explicitly included. We demonstrate that, if matter is covariantly conserved, the late growth of matter density perturbations is independent of the wavenumber. Furthermore, if Lambda is negligible at high redshifts and G varies slowly, we find that these cosmologies produce a matter power spectrum with the same shape as that of the concordance LCDM model, thus predicting the same basic features on structure formation. Despite this shape indistinguishability, the free parameters of the variable G and Lambda models can still be effectively constrained from the observational bounds on the spectrum amplitude.Comment: Accepted in Classical and Quantum Gravity. One appendix on perturbations in the Newtonian gauge added. Extended discussion and new references

Adoção de sistemas de integração lavoura-pecuária-floresta (ILPF) em São Paulo.

Este estudo objetivou caracterizar a adoção dos sistemas de integração no Estado de São Paulo e identificar demandas. Uma amostra de 175 propriedades rurais, sendo 66 adotantes de sistemas de Integração Lavoura-Pecuária (ILP), 24 adotantes de sistemas de Integração PecuáriaFloresta (IPF) e 85 não adotantes de sistemas integrados, compôs a base de dados analisados por meio de estatística descritiva e teste qui-quadrado (x2) de Pearson. Os resultados indicam que os adotantes de sistemas ILP possuem maior experiência com atividades agrícolas, participação mais frequente em cooperativas agrícolas, palestras e dias de campo, bem como recebem mais orientação técnica. O acesso ao crédito rural e o uso mais frequente de mecanismos para gestão do risco climático e econômico estão associados ao componente agrícola do ILP. O fator escala de produção explica propriedades rurais mais extensas e estrutura mais robusta de máquinas agrícolas. A adoção dos sistemas IPF encontra-se em fase experimental nas propriedades rurais. Esses adotantes contam com outra fonte de renda, o que os confere maior flexibilidade para testar o sistema, em sua maioria, implantado de forma escalonada na área de pastagem e com recursos próprios. Predominam propriedades rurais menores, com relevo mais ondulado, solos arenosos, rebanhos menores e concentrados nas fases de cria/recria, além de maior diversificação da produção.bitstream/item/214315/1/AdocaoSistemasIntegracao.pd