Search results for "inflation"

Impact of general reionization scenarios on extraction of inflationary parameters

2010

Determination of whether the Harrison-Zel'dovich spectrum for primordial scalar perturbations is consistent with observations is sensitive to assumptions about the reionization scenario. In light of this result, we revisit constraints on inflationary models using more general reionization scenarios. While the bounds on the tensor-to-scalar ratio are largely unmodified, when different reionization schemes are addressed, hybrid models are back into the inflationary game. In the general reionization picture, we reconstruct both the shape and amplitude of the inflaton potential. We discuss how relaxing the simple reionization restriction affects the reconstruction of the potential through the c…

Minimal noncanonical cosmologies

2006

We demonstrate how much it is possible to deviate from the standard cosmological paradigm of inflation-assisted LambdaCDM, keeping within current observational constraints, and without adding to or modifying any theoretical assumptions. We show that within a minimal framework there are many new possibilities, some of them wildly different from the standard picture. We present three illustrative examples of new models, described phenomenologically by a noncanonical scalar field coupled to radiation and matter. These models have interesting implications for inflation, quintessence, reheating, electroweak baryogenesis, and the relic densities of WIMPs and other exotics.

Inflation might be caused by the right

2009

15 pages, 4 figures.-- ISI article identifier: 000265600800102.-- ArXiv pre-print avaible at: http://arxiv.org/abs/0811.2998

Upper bound on the tensor-to-scalar ratio in GUT-scale supersymmetric hybrid inflation

2014

We explore the upper bound on the tensor-to-scalar ratio r in supersymmetric (F-term) hybrid inflation models with the gauge symmetry breaking scale set equal to the value 2.86⋅1016 GeV2.86⋅1016 GeV, as dictated by the unification of the MSSM gauge couplings. We employ a unique renormalizable superpotential and a quasi-canonical Kähler potential, and the scalar spectral index nsns is required to lie within the two-sigma interval from the central value found by the Planck satellite. In a sizable region of the parameter space the potential along the inflationary trajectory is a monotonically increasing function of the inflaton, and for this case, r≲2.9⋅10−4r≲2.9⋅10−4, while the spectral index…

2017

We show that the dynamics of the Higgs field during inflation is not affected by metric fluctuations if the Higgs is an energetically subdominant light spectator. For Standard Model parameters we find that couplings between Higgs and metric fluctuations are suppressed by $\mathcal{O}(10^{-7})$. They are negligible compared to both pure Higgs terms in the effective potential and the unavoidable non-minimal Higgs coupling to background scalar curvature. The question of the electroweak vacuum instability during high energy scale inflation can therefore be studied consistently using the Jordan frame action in a Friedmann--Lemaitre--Robertson--Walker metric, where the Higgs-curvature coupling en…

Primordial power spectrum features in phenomenological descriptions of inflation

2016

We extend an alternative, phenomenological approach to inflation by means of an equation of state and a sound speed, both of them functions of the number of $e$-folds and four phenomenological parameters. This approach captures a number of possible inflationary models, including those with non-canonical kinetic terms or scale-dependent non-gaussianities. We perform Markov Chain Monte Carlo analyses using the latest cosmological publicly available measurements, which include Cosmic Microwave Background (CMB) data from the Planck satellite. Within this parametrization, we discard scale invariance with a significance of about $10\sigma$, and the running of the spectral index is constrained as …

Isocurvature Constraints on Portal Couplings

2016

We consider portal models which are ultraweakly coupled with the Standard Model, and confront them with observational constraints on dark matter abundance and isocurvature perturbations. We assume the hidden sector to contain a real singlet scalar $s$ and a sterile neutrino $\psi$ coupled to $s$ via a pseudoscalar Yukawa term. During inflation, a primordial condensate consisting of the singlet scalar $s$ is generated, and its contribution to the isocurvature perturbations is imprinted onto the dark matter abundance. We compute the total dark matter abundance including the contributions from condensate decay and nonthermal production from the Standard Model sector. We then use the Planck lim…

L'ouverture de la Chine et ses impacts sur l'économie chinoise

2012

In the early 1980s, Chinese government has adopted an opening up policy in order to attract capital, skills and modern advanced technology that are necessary for the economic development of China. Indeed, this policy has already borne fruit. China, that was almost self-sufficient until the 1980s, has now become the largest exporter and the second largest recipient of foreign direct investment in the world. Until now, most of the research on the economic opening up policy of China, however, has concentrated on the demonstration of the positive effects of exports and FDI inflows on the domestic economy of China. In this thesis, based on the analysis of economics of production, we study the re…

Shipping Costs and Inflation

2023

The Covid-19 pandemic has disrupted global supply chains, leading to shipment delays and soaring shipping costs. We study the impact of global shipping costs-measured by the Baltic Dry Index (BDI)-on domestic prices for a large panel of countries during the period 1992-2021. We find that spikes in the BDI are followed by sizable and statistically signif-icant increases in import prices, PPI, headline, and core inflation, as well as inflation expec-tations. The impact is similar in magnitude but more persistent than for shocks to global oil and food prices. The effects are more muted in countries where imports make up a smaller share of domestic consumption, and those with inflation targetin…

Oil prices and inflation dynamics: Evidence from advanced and developing economies

2018

Abstract We study the impact of fluctuations in global oil prices on domestic inflation using an unbalanced panel of 72 advanced and developing economies over the period from 1970 to 2015. We find that a 10% increase in global oil inflation increases, on average, domestic inflation by about 0.4 percentage points on impact, with the effect vanishing after two years and being similar between advanced and developing economies. We also find that the effect is asymmetric, with positive oil price shocks having a larger effect than negative ones. The impact of oil price shocks, however, has declined over time due in large part to a more credible monetary policy and less reliance on energy imports.…