Open Inflation Research Articles

Tilted spatially nonflat inflation

We construct nonlinear inflaton potential-energy densities that describe not necessarily very slowly rolling closed and open inflation models, and compute tilted primordial spatial inhomogeneity power spectra that follow from quantum-mechanical fluctuations during inflation in these models. Earlier nonflat inflation model power spectra computations assumed an inflaton potential-energy density with a linear slope that resulted in very slow roll during inflation and untilted power spectra. These new tilted power spectra differ from those that have previously been used to study cosmological data in nonflat cosmological models.

On stringy inflation potentials

We investigate cosmological inflation models from Randall–Sundrum brane physics. In particular, we examine certain cosmological parameters for two potentials, being a logarithmical one and open string tachyonic inflation (OSTI). In the presence of the brane tension, we give scalar field constraints providing inflationary models matching with Planck results. Then, we discuss the reheating phase of such models. Precisely, the reheating temperature depends on the potential forms. Among others, we find that OSTI provides small temperatures, supported by GUT scales.

Bent Hansen’s theory of inflation 19511

Bent Hansen’s analysis of repressed and open inflation was to some extent based on microeconomics, he analysed the interaction between wage and price inflation and discussed economic policy problems when there were goals in addition to that of curbing inflation. Hansen was influenced by Erik Lindahl who, like the other members of the Stockholm School was critical to the quantity theory of money. Hansen’s book contains early analyses of spill-over effects and building blocks of the supply multiplier.

Testing of the Phillips Curve in Indonesia

This study aims to determine how the results of Phillips theory testing in 34 provinces in Indonesia based on the main sectors contributing to the GRDP. The analytical method used in this study is Product Moment correlation analysis to determine the relationship between the inflation rate variable and the unemployment rate variable. The data used in this study are data on open unemployment and inflation rates taken in 34 provinces in Indonesia from 2014-2018. The results of this study indicate there is no Phillips curve pattern in 34 provinces in Indonesia. The inflation rate variable and the unemployment rate variable in 34 provinces in Indonesia based on the main sectors contributing to the GRDP have a positive but very weak relationship with a correlation value of 0.1089. The problem of price volatility (inflation) contributes, although not significantly to the emergence of the unemployment problem. Government policies are needed to control inflation and reduce unemployment rates such as fuel subsidies, corporate tax reductions, export tax reductions, and control of raw material prices considering that the results of this study indicate that rising inflation will be followed by an increase in unemployment.

Exchange rate pass-through & management of inflation expectations in a small open inflation targeting economy

In the context of inflation targeting, this study analyses the exchange rate pass-through (ERPT) to inflation expectations in a small open inflation targeting economy. We also augment the inflation expectations function with GDP, inflation, unemployment, fiscal stance, oil prices and money supply. Drawing on the data from May 1999 to Dec 2018 on the Czech Republic, which was the first developing country to adopt inflation targeting, our key results suggest that ERPT has significant implications for inflation expectations. Inflation expectations are also strongly influenced by actual inflation and past inflation expectations suggesting evidence of adaptive expectations. Economic growth, labour market outlook, money supply, oil price shocks and fiscal stance also showed a considerable impact on inflation expectations, though results varied in the short and long run. Our study contributes to the debate on ERPT and inflation targeting by reflecting on the inflation expectations channel.

An Unconventional Approach to Evaluate the Bank of England’s Asset Purchase Program

Empirical papers analysing the transmission of (unconventional) monetary policy typically rely on a vector autoregressive framework. In this paper, I complement these studies and employ a matching approach to examine the impact of the Bank of England’s asset purchase program on macroeconomic quantities in the UK. My sample covers the period March 2001−December 2015 and five small open inflation targeting economies. Using entropy balancing, I create a synthetic control group comprised of credible counterfactuals for the sample of observations subject to quantitative easing (QE). My key results indicate that a 100 bn GBP increase in QE has a significant and positive effect on GDP growth with a peak effect of 0.66−0.69 percentage points (pp) after 30 months. The same increase leads to a reduction in the inflation gap with a peak effect between −0.77 and −0.94 pp after 30 months. An in-depth analysis reveals that the latter finding is not driven by the choice of the empirical methodology. In contrast, I find that the returns on QE in the UK are decreasing (i) over time and (ii) with the volume of QE. Consequently, monetary policymakers should be aware of the fact that the returns on QE might be non-linear and that QE eventually could have detrimental effects.

Exchange Rate Pass-Through & Management of Inflation Expectation in a Small Open Inflation Targeting Economy

This study analyses the aspect of inflation expectations management in the context of inflation targeting by particularly focusing on the impact of exchange rate pass-through to inflation expectations in a small open economy. We also augment the inflation expectations function with GDP, inflation, unemployment, fiscal stance, oil prices, and money supply. Drawing on the data from May 1999 to Dec 2018 on the Czech Republic which is the first developing country to adopted inflation targeting, our key results suggest that ERPT has significant implications for the inflation expectations. Inflation expectations are strongly influenced by the actual inflation and the past inflation expectations suggesting evidence of adaptive expectation. The economic growth, labour market outlook, money supply, oil price shocks, and fiscal stance also showed a considerable impact on inflation expectations, though results varied in the short and long-run. Our study contributes to the debate on ERPT and inflation targeting by reflecting on the inflation expectations channel.

Reconstruction of primordial tensor power spectra from B -mode polarization of the cosmic microwave background

Given observations of B-mode polarization power spectrum of the cosmic microwave background (CMB), we can reconstruct power spectra of primordial tensor modes from the early Universe without assuming their functional form such as a power-law spectrum. Shape of the reconstructed spectra can then be used to probe the origin of tensor modes in a model-independent manner. We use the Fisher matrix to calculate the covariance matrix of tensor power spectra reconstructed in bins. We find that the power spectra are best reconstructed at wavenumbers in the vicinity of $k\approx 6\times 10^{-4}$ and $5\times 10^{-3}~{\rm Mpc}^{-1}$, which correspond to the "reionization bump" at $\ell\lesssim 6$ and "recombination bump" at $\ell\approx 80$ of the CMB B-mode power spectrum, respectively. The error bar between these two wavenumbers is larger because of lack of the signal between the reionization and recombination bumps. The error bars increase sharply towards smaller (larger) wavenumbers because of the cosmic variance (CMB lensing and instrumental noise). To demonstrate utility of the reconstructed power spectra we investigate whether we can distinguish between various sources of tensor modes including those from the vacuum metric fluctuation and SU(2) gauge fields during single-field slow-roll inflation, open inflation and massive gravity inflation. The results depend on the model parameters, but we find that future CMB experiments are sensitive to differences in these models. We make our calculation tool available on-line.

Strongly scale-dependent CMB dipolar asymmetry from super-curvature fluctuations

We reconsider the observed CMB dipolar asymmetry in the context of open inflation, where a supercurvature mode might survive the bubble nucleation. If such a supercurvature mode modulates the amplitude of the curvature power spectrum, it would easily produce an asymmetry in the power spectrum. We show that current observational data can be accommodated in a three-field model, with simple quadratic potentials and a non-trivial field-space metric. Despite the presence of three fields, we believe this model is so far the simplest that can match current observations. We are able to match the observed strong scale dependence of the dipolar asymmetry, without a fine tuning of initial conditions, breaking slow roll or adding a feature to the evolution of any field.

An Unconventional Approach to Evaluate the Bank of England's Asset Purchase Program

Empirical papers analysing the transmission of (unconventional) monetary policy typically rely on a vector autoregressive framework. In this paper, I complement these studies and employ a matching approach to examine the impact of the Bank of England's asset purchase program on macroeconomic quantities in the UK. My sample covers the period March 2001-December 2015 and five small open inflation targeting economies. Using entropy balancing, I create a synthetic control group comprised of credible counterfactuals for the sample of observations subject to the asset purchase program. My key results are that a 100 bn GBP increase in asset purchases has a significant and positive effect on GDP growth with a peak effect of 0.66-0.69 percentage points (pp) after 30 months. The same increase leads to a reduction in the inflation gap with a peak effect between -0.77 and -0.94 pp after 30 months. An in-depth analysis reveals that the latter finding is not driven by the choice of the empirical methodology. In contrast, I find that the returns on asset purchases are decreasing (i) over time and (ii) with the level of asset purchases. This causes the impact of asset purchases on the inflation gap to eventually become negative.

Study of water salinity effect on geotechnical behavior of soil structure using response surface method (RSM), (Case study: Gotvand Dam)

Specifying the mechanical characteristics of soil is as one of the major steps in designing the foundation for civil projects, particularly hydraulic structures. This study examines the water salinity effect on engineering characteristics of fine-grained soil in clayey core of Gotvand dam which it is located on the Karun River in Khuzestan province, Iran. For this purpose, three types of salt; sodium chloride, magnesium chloride and calcium sulfate is considered that the last one has the highest concentration in the water of reservoir behind the dam, and then their effect on the mechanical characteristics of clay including density, Atterberg limits, angel of internal friction, adhesion and open inflation have examined. Therefore, treatments required for testing were provided by combining the mentioned salts considering the weight percentage of salt in the water behind the dam and designing a test using response surface methodology (RSM). The results were statistically analyzed by RSM. Results showed that type and amount of soil salinity has no significant impact on the compaction characteristics of soil namely optimum moisture content and the maximum dry density. Results of changes in Atterberg limits showed that presence of salt ions reduces the plasticity of the soil and it was seen a certain decrease in the liquid limit and subsequently a dramatic drop in soil plasticity by increasing the percentage of soil; while the plastic limit remained almost unchanged. Eventually, results of open inflation showed that whatever the salt concentration be higher, the rate of sample's open inflation will be lower.

Study of water salinity effect on geotechnical behavior of soil structure using response surface method (RSM), (Case study: Gotvand Dam)

Specifying the mechanical characteristics of soil is as one of the major steps in designing the foundation for civil projects, particularly hydraulic structures. This study examines the water salinity effect on engineering characteristics of fine-grained soil in clayey core of Gotvand dam which it is located on the Karun River in Khuzestan province, Iran. For this purpose, three types of salt; sodium chloride, magnesium chloride and calcium sulfate is considered that the last one has the highest concentration in the water of reservoir behind the dam, and then their effect on the mechanical characteristics of clay including density, Atterberg limits, angel of internal friction, adhesion and open inflation have examined. Therefore, treatments required for testing were provided by combining the mentioned salts considering the weight percentage of salt in the water behind the dam and designing a test using response surface methodology (RSM). The results were statistically analyzed by RSM. Results showed that type and amount of soil salinity has no significant impact on the compaction characteristics of soil namely optimum moisture content and the maximum dry density. Results of changes in Atterberg limits showed that presence of salt ions reduces the plasticity of the soil and it was seen a certain decrease in the liquid limit and subsequently a dramatic drop in soil plasticity by increasing the percentage of soil; while the plastic limit remained almost unchanged. Eventually, results of open inflation showed that whatever the salt concentration be higher, the rate of sample's open inflation will be lower.

Constraints on preinflation fluctuations in a nearly flat openΛCDMcosmology

We analyze constraints on parameters characterizing the pre-inflating universe in an open inflation model with a present slightly open $\Lambda$CDM universe. We employ an analytic model to show that for a broad class of inflation-generating effective potentials, the simple requirement that some fraction of the observed dipole moment represents a pre-inflation isocurvature fluctuation allows one to set upper and lower limits on the magnitude and wavelength scale of pre-inflation fluctuations in the inflaton field, and the curvature of the pre-inflation universe, as a function of the fraction of the total initial energy density in the inflaton field as inflation begins. We estimate that if the pre-inflation contribution to the current CMB dipole is near the upper limit set by the {\it Planck} Collaboration then the current constraints on $\Lambda$CDM cosmological parameters allow for the possibility of a significantly open $\Omega_{i} \le 0.4$ pre-inflating universe for a broad range of the fraction of the total energy in the inflaton field at the onset of inflation. This limit to $\Omega_{i}$ is even smaller if a larger dark-flow tilt is allowed.

Scalar suppression on large scales in open inflation

We consider two toy models of open inflation and investigate their ability to give a suppression of scalar power on large scales whilst also satisfying observational constraints on the spatial curvature of the universe. Qualitatively we find that both models are indeed capable of fulfilling these two requirements, but we also see that effects of the quantum tunnelling must be carefully taken into account if we wish to make quantitative predictions.

CP VIOLATIONS (AND MORE) AFTER THE FIRST TWO YEARS OF LHCB

The most interesting cosmological open problems, baryon asymmetry, dark matter, inflation and dark energy, are not explained by the standard model of particle physics (SM). The final<br />goal of the Large Hadron Collider an experimental verification of the SM in the Higgs sector, and also a search for evidence of new physics beyond it. In this paper we will report some of the results obtained in 2010 and 2011, from the LHCb experiment dedicated to the study of CP violations and rare decays of heavy quarks.

Bispectrum from open inflation

We calculate the bispectrum of primordial curvature perturbations,ζ, generated during ``open inflation.'' Inflation occurs inside abubble nucleated via quantum tunneling from the background false vacuumstate. Our universe lives inside the bubble, which can be described as a Friedmann-Lemaȋtre-Robertson-Walker (FLRW) universe with negative spatial curvature, undergoing slow-roll inflation. We pay special attention to the issue of an initial state for quantum fluctuations. A ``vacuum state'' defined by a positive-frequency mode in de Sitter space charted by open coordinates is different from the Euclidean vacuum (which is equivalent to the so-called ``Bunch-Davies vacuum'' defined by a positive-frequency mode in de Sitter space charted by flat coordinates). Quantum tunneling (bubble nucleation) then modifies the initial state away from the original Euclidean vacuum. While most of the previous study on modifications of the initial quantum state introduces, by hand, an initial time at which the quantum state is modified as well as the form of the modification, an effective initial time naturally emerges and the form is fixed by quantum tunneling in open inflation models. Therefore, open inflation enables a self-consistent computation of the effect of a modified initial state on the bispectrum. We find a term which goes as ⟨ζk1ζk2ζk3⟩∝1/k12k34 in the so-called squeezed configurations, k3 << k1 ≈ k2, in agreement with the previous study on modifications of the initial state. The bispectrum in the exact folded limit, e.g., k1 = k2+k3, is also enhanced and remains finite.However, these terms are exponentially suppressed when the wavelength of ζ is smaller than the curvature radius of the universe. The leading-order bispectrum is equal to the usual one from single-field slow-roll inflation;the terms specific for open inflation arise only in the sub-leadingorder when the wavelength of ζ is smaller than the curvature radius.

Cosmic Microwave Background Anomalies in an Open Universe

We argue that the observed large-scale cosmic microwave anomalies, discovered by WMAP and confirmed by the Planck satellite, are most naturally explained in the context of a marginally open universe. Particular focus is placed on the dipole power asymmetry, via an open universe implementation of the large-scale gradient mechanism of Erickcek etal. Open inflation models, which are motivated by the string landscape and which can excite "supercurvature" perturbation modes, can explain the presence of a very-large-scale perturbation that leads to a dipole modulation of the power spectrum measured by a typical observer. We provide a specific implementation of the scenario which appears compatible with all existing constraints.

Probing two-field open inflation by resonant signals in correlation functions

We derive oscillatory signals in correlation functions in two-field open inflation by means of the in-in formalism; such signatures are caused by resonances between oscillations in the tunnelling field and fluctuations in the inflaton during the curvature dominated, intermediate and subsequent inflationary regime. While amplitudes are model-dependent, we find distinct oscillations in the power and bi-spectrum that can act as a direct probe of the curvature dominated phase and thus, indirectly, strengthen the claim of the string landscape if they were observed. We comment on the prospects of detecting these tell-tale signs in current experiments, which is challenging, but not impossible.At the technical level, we pay special attention to the applicability conditions for truncating fluctuations to the light (inflaton) field and derive upper limits on the oscillation amplitude of the heavy field. A violation of these bounds requires a multi-field analysis at the perturbed level.

Mode spectrum of the electromagnetic field in open universe models

We examine the mode functions of the electromagnetic field on spherically symmetric backgrounds with special attention to the subclass which allows for the foliation as open Friedmann-Lemaitre (FL) spacetime. It is well-known that in certain scalar field theories on open FL background there can exist so-called supercurvature modes, their existence depending on parameters of the theory. Looking at specific open universe models, such as open inflation and the Milne universe, we find that no supercurvature modes are present in the spectrum of the electromagnetic field. This excludes the possibility for superadiabatic evolution of cosmological magnetic fields within these models without relying on new physics or breaking the conformal invariance of electromagnetism.

Multi-field open inflation model and multi-field dynamics in tunneling

We consider a multi-field open inflation model, in which one of the fields dominates quantum tunneling from a false vacuum while the other field governs slow-roll inflation within the bubble nucleated from false vacuum decay. We call the former the tunneling field and the latter the inflaton field. In the limit of a negligible interaction between the two fields, the false vacuum decay is described by a Coleman-De Luccia instanton. Here we take into account the coupling between the two fields and construct explicitly a multi-field instanton for a simple quartic potential model. We also solve the evolution of the scalar fields within the bubble. We find our model realizes open inflation successfully. This is the first concrete, viable model of open inflation realized with a simple potential. We then study the effect of the multi-field dynamics on the false vacuum decay, specifically on the tunneling rate. We find the tunneling rate increases in general provided that the multi-field effect can be treated perturbatively.