Inflation Instability Research Articles

New models of d-dimensional black holes without inner horizon and with an integrable singularity

Theoretically, it has been proposed that objects traveling radially along regular black holes (RBHs) would not be destroyed because of finite tidal forces and the absence of a singularity. However, the matter source allows the creation of an inner horizon linked to an unstable de Sitter core due to mass inflation instability. This inner horizon also gives rise to the appearance of a remnant, inhibiting complete evaporation. We introduce here a d-dimensional black hole model with Localized Sources of Matter (LSM), characterized by the absence of an inner horizon and featuring a central integrable singularity instead of an unstable de Sitter core. In our model, any object tracing a radial and timelike world-line would not be crushed by the singularity. This is attributed to finite tidal forces, the extendability of radial geodesics, and the weak nature of the singularity. Our LSM model enables the potential complete evaporation down to r h = 0 without forming a remnant. In higher dimensions, complete evaporation occurs through a phase transition, which could occur at Planck scales and be speculatively driven by the Generalized Uncertainty Principle (GUP). Unlike RBHs, our model satisfies the energy conditions. We demonstrate a linear correction to the conventional area law of entropy, distinct from the RBH's correction. Additionally, we investigate the stability of the solutions through the speed of sound.

Examining the Relationship between Inflation Instability and Ecological Footprint: Evidence from Turkey

Sustainability is a preeminent global issue. This study delves into sustainability with an examination of the effect of inflation instability on ecological footprint per capita through financial development, economic growth, and energy consumption by using the ARDL model for Turkey for the period 1980 through 2015. The results of this study confirmed that financial development and inflation instability improve the environment insignificantly while economic growth does not significantly damage the environment. In addition, energy consumption is found to cause environmental degradation. Results of this study show that the main issue for Turkey is consumption rather than production. Suggested policy-making implications are provided in the conclusion.

Growth volatility in the inflation-targeting regime: Evidence from Indonesia

<abstract> <p>Low and stable inflation and exchange rates are the main objectives of inflation-targeting monetary policy. The internal and external stabilities are prerequisites for promoting economic growth. Using a two-stage GARCH, we investigated the effect of inflation instability and exchange rate unpredictability on the economic growth uncertainty in the case of Indonesia over the period 2000(1)– 2022(12). It was evident that both inflation instability and exchange rate unpredictability hurt output growth. The impact of inflation instability was higher than that of exchange rate unpredictability. While the output growth was higher in the post inflation-targeting regime adoption, the effect of real exchange rate instability was greater than that of nominal exchange rate unpredictability. Those findings suggested that the monetary authority should strengthen their commitment to achieve the inflation target range. The sharper focus on the inflation stability might avoid the monetary authority conducting twofold targets of inflation and exchange rate stability to stimulate economic growth.</p> </abstract>

Türkiye’de Enflasyon İstikrarsızlığı Çevre Kirliliğine Neden Olur mu? Fourier-Wavelet Nedensellik Testinden Kanıtlar

The Turkish economy has faced many macroeconomic problems in terms of GDP stability, inflation stability, growth rate, and exchange rate. This situation has become even more noticeable in recent times, especially with the negative effects of the Covid 19 epidemic and the Russia-Ukraine war. Thus, inflation in Turkiye has increased and has a more unstable outlook. However, environmental problems have also increased. In light of this information, the aim of the study is to examine the causality relationship between inflation instability and environmental pollution for the period 1990-2021 by considering growth, energy consumption, and financial development as control variables in Turkiye. For this purpose, firstly, the series was subjected to wavelet transform. Afterwards, the transformed series were analyzed with the Fourier TY and Fractional Fourier TY causality tests as short, medium, and long term. Findings from the Fourier causality test show that inflation instability promotes environmental pollution in the short, medium, and long term. According to the Fractional Fourier causality test, which I used to test whether the shocks are permanent, there is persistence from inflation instability to environmental pollution only in the medium term. This study is the first to examine the subject in the case of Türkiye.

INFLATION VALUE FORECASTING POST COVID-19 IN DENPASAR USING ARIMA

Forecasting is used to predict something that will happen in the future so that appropriate actions can be taken. ARIMA is a time series forecasting method that was developed where the observation data in a time series data interact. Inflation instability in Denpasar City in the future will make it difficult for the central bank and the government to determine policy. The Covid-19 pandemic has an impact on the value of inflation in Denpasar City. The purpose of this study is to estimate inflation in Denpasar City after Covid using the best ARIMA model. Inflation data was taken from BPS Denpasar City from January 2020 to August 2022. ARIMA analysis was carried out according to the Box-Jenkins procedure, namely searching the data, estimating parameters and significance tests, and determining the best ARIMA model. The results of the analysis show that the best ARIMA model is ARIMA (0,1,1). The results of this study indicate that monthly inflation in Denpasar City is likely to continue to increase. Based on these results, it is hoped that appropriate policies will be made to reduce inflation.

Regularized stable Kerr black hole: cosmic censorships, shadow and quasi-normal modes

Black hole solutions in general relativity come with pathologies such as singularity and mass inflation instability, which are believed to be cured by a yet-to-be-found quantum theory of gravity. Without such consistent description, one may model theory-agnostic phenomenological black holes that bypass the aforesaid issues. These so-called regular black holes are extensively studied in the literature using parameterized modifications over the black hole solutions of general relativity. However, since there exist several ways to model such black holes, it is important to study the consistency and viability of these solutions from both theoretical and observational perspectives. In this work, we consider a recently proposed model of regularized stable rotating black holes having two extra parameters in addition to the mass and spin of a Kerr solution. We start by computing their quasi-normal modes under scalar perturbation and investigate the impact of those additional parameters on black hole stability. In the second part, we study shadows of the central compact objects in M87^* and Sgr, A^* modelled by these regularized black holes and obtain stringent bounds on the parameter space requiring consistency with Event Horizon Telescope observations.

Instability in axion inflation with strong backreaction from gauge modes

We perform an analytical study of the stability of the background solution [1] of the model in which an inflaton, through an axionic coupling to a U(1) gauge field, causes an amplification of the gauge field modes that strongly backreact on its dynamics. To this goal, we study the evolution of the gauge field modes coupled to the inflaton zero mode, treating perturbatively the deviation of the inflaton velocity from its mean-field value. As long as the system is in the strong backreaction regime we find that the inflaton velocity performs oscillations of increasing amplitude about the value it would have in the approximation of constant velocity, confirming an instability that has been observed in numerical studies.

Classical mass inflation versus semiclassical inner horizon inflation

We analyze the geometry of a spherically symmetric black hole with an inner and outer apparent horizon that is perturbed by spherical null shells of matter. On a classical level we observe that the mass inflation instability is triggered, resulting in a growth of curvature and an inward displacement of the inner horizon. We study in detail the inner structure of the mass-inflated region and compare it with previous results obtained for the case in which the perturbing matter content has a continuous distribution. We then perform an approximate calculation of the renormalized stress-energy tensor of a quantum field in the vicinity of the inner horizon, and analyze the semiclassical backreaction on this region of the geometry. We find that the classical tendency for this horizon to move inward due to mass inflation is challenged and potentially overcome by a semiclassical tendency for it to inflate outward.

Regular black holes without mass inflation instability

Generic models of regular black holes have separate outer and inner horizons, both with nonzero surface gravity. It has been shown that a nonzero inner horizon surface gravity results in exponential instability at the inner horizon controlled by this parameter. This phenomenon takes the name of “mass inflation instability”, and its presence has put in question the physical viability of regular black holes as alternatives to their (singular) general relativity counterparts. In this paper, we show that it is possible to make the inner horizon surface gravity vanish, while maintaining the separation between horizons, and a non-zero outer horizon surface gravity. We construct specific geometries satisfying these requirements, and analyze their behavior under different kinds of perturbations, showing that the exponential growth characteristic of mass inflation instability is not present for these geometries. These “inner-extremal” regular black holes are thereby better behaved than singular black holes and generic regular black holes, thus providing a well-motivated alternative of interest for fundamental and phenomenological studies.

A fake instability in string inflation

In type IIB fibre inflation models the inflation is a Kähler modulus which is kinetically coupled to the corresponding axion. In this setup the curvature of the field space induces tachyonic isocurvature perturbations normal to the background inflationary trajectory. However we argue that the associated instability is unphysical since it is due to the use of ill-defined entropy variables. In fact, upon using the correct relative entropy perturbation, we show that in fibre inflation axionic isocurvature perturbations decay during inflation and the dynamics is essentially single-field.

Historical Perspective of External Debt in Pakistan: Identifying Key Determinants / Strategies

The non-developmental use of external debt creates macroeconomic instability which results in massive unemployment, poverty, inflation, and political instability in any country. The present study is focused on historical perspective of external debt in Pakistan. This study found that the leadership of Pakistan has heavily borrowed external debt without considering its sustainability and repayment capacity. On the basis of the systematic literature review of past studies, the key policy variables are highlighted to reduce the burden of external debt. The study indicated that external debt burden of Pakistan can be managed by lowering the consumption oriented imports, focusing targeted inflation, exchange rate and by promoting sustainable inclusive economic growth. The policy mix based on efficient management of macro-economic indicators are helpful in addressing external debt in Pakistan.

Efekti sprovođenja režima za suzbijanje inflacije na ekonomski rast

This research study is focused on the examination of the influence of the introduction and implementation of the monetary Inflation Targeting (IT) regime: the level of the inflation rate and the Gross Domestic Product (GDP) growth rate, as well as inflation and the GDP volatility. Conditional variance is calculated by fitting an empirical Generalized Autoregressive Conditional Heteroskedasticity (GARCH) model to an annualized quarterly date for the period from 1993Q1 to 2020Q3, all in order to assess volatility. The results of the regression model showed that there was a positive statistical significance between the instability of inflation and the instability of the growth rate of the GDP in the three analyzed countries (namely in Albania, Turkey and the Republic of Serbia). The result of introducing the IT regime when the GDP growth rate volatility is concerned is statistically significant in Serbia and Turkey and led to reduction in the GDP volatility and stabilization. However, the applied regression model indicated that, in the case of Albania and Romania, the introduction of the IT regime did not have a statistically significant impact on the GDP growth rate volatility.

Inflation instability in the lung: an analytical model of a thick-walled alveolus with wavy fibres under large deformations.

Inflation of hollow elastic structures can become unstable and exhibit a runaway phenomenon if the tension in their walls does not rise rapidly enough with increasing volume. Biological systems avoid such inflation instability for reasons that remain poorly understood. This is best exemplified by the lung, which inflates over its functional volume range without instability. The goal of this study was to determine how the constituents of lung parenchyma determine tissue stresses that protect alveoli from instability-related overdistension during inflation. We present an analytical model of a thick-walled alveolus composed of wavy elastic fibres, and investigate its pressure-volume behaviour under large deformations. Using second-harmonic generation imaging, we found that collagen waviness follows a beta distribution. Using this distribution to fit human pressure-volume curves, we estimated collagen and elastin effective stiffnesses to be 1247 kPa and 18.3 kPa, respectively. Furthermore, we demonstrate that linearly elastic but wavy collagen fibres are sufficient to achieve inflation stability within the physiological pressure range if the alveolar thickness-to-radius ratio is greater than 0.05. Our model thus identifies the constraints on alveolar geometry and collagen waviness required for inflation stability and provides a multiscale link between alveolar pressure and stresses on fibres in healthy and diseased lungs.

Instabilities in liquid crystal elastomers

Stability is an important and fruitful avenue of research for liquid crystal elastomers. At constant temperature, upon stretching, the homogeneous state of a nematic body becomes unstable, and alternating shear stripes develop at very low stress. Moreover, these materials can experience classical mechanical effects, such as necking, void nucleation and cavitation, and inflation instability, which are inherited from their polymeric network. We investigate the following two problems: First, how do instabilities in nematic bodies change from those found in purely elastic solids? Second, how are these phenomena modified if the material constants fluctuate? To answer these questions, we present a systematic study of instabilities occurring in nematic liquid crystal elastomers, and examine the contribution of the nematic component and of fluctuating model parameters that follow probability laws. This combined analysis may lead to more realistic estimations of subsequent mechanical damage in nematic solid materials. Because of their complex material responses in the presence of external stimuli, liquid crystal elastomers have many potential applications in science, manufacturing, and medical research. The modeling of these materials requires a multiphysics approach, linking traditional continuum mechanics with liquid crystal theory, and has led to the discovery of intriguing mechanical effects. An important problem for both applications and our fundamental understanding of nematic elastomers is their instability under large strains, as this can be harnessed for actuation, sensing, or patterning. The goal is then to identify parameter values at which a bifurcation emerges, and how these values change with external stimuli, such as temperature or loads. However, constitutive parameters of real manufactured materials have an inherent variation that should also be taken into account, thus the need to quantify uncertainties in physical responses, which can be done by combining the classical field theories with stochastic methods that enable the propagation of uncertainties from input data to output quantities of interest. The present study demonstrates how to characterize instabilities found in nematic liquid crystal elastomers with probabilistic material parameters at the macroscopic scale, and paves the way for a systematic theoretical and experimental study of these fascinating materials.

The trade-off between economic growth and environmental quality: does economic freedom asymmetric matter for Pakistan?

This empirical study investigates the dynamic effects of economic freedom on economic growth and air quality for Pakistan over the period 1990-2019. The ARDL results suggest that economic freedom and other variables do not have any visible impact on economic growth and pollution in the short-run. However, in the long-run, economic freedom significantly mitigates air pollution whereas inflation instability increases emissions. The NARDL results show that a partial sum of positive change in economic freedom is negatively linked with economic growth in the short term but has positive effect in the long term. However, the negative change in economic freedom has negative but insignificant impact on growth confirming asymmetric effects. The results for the pollution model show that a partial sum of positive change in economic freedom has positive impact on emissions both in the short and long-runs, whereas a negative change has no significant effect in the short-run and has negative impact in the long-run. Thus, economic freedom supports economic activities that, in turn, escalate emissions in the atmosphere.

The Impact of BI Interest Rate and Amount of Money Supply on Inflation in Indonesia During 2017-2019

The economic progress of a country is surely influenced by its economic indicators. This indicator is an important thing to pay it attention. One of the economic indicators is inflation. Inflation will affect the economy aggregately. Due to the increase in inflation and inflation instability, it will indicate that the level of prices for goods and services in a country is high. In the end, this will have an impact on people's interest in buying these goods or using these services. Of course, the large impact will be sustainable on national income. Therefore, this study aims to analyze the effect of interest rates and the money supply on inflation in Indonesia in 2017-2019. The types of data used in this study are quantitative data and the data sources used are taken from BPS for the 2017-2019 period. .The final result of this study showed that based on the results of the analysis, it could be concluded that interest rates and the amount of money have an impact on inflation with a significance value of 0,000296. Meanwhile, the t-test results indicate that interest rates and the money supply have an impact on inflation, respectively, with values of significance are 0.0371 and 0.0286.

Does inflation instability affect environmental pollution? Fresh evidence from Asian economies

The present study examines the linkage between inflation instability and pollution emissions for the 40 Asian economies over the period of 1990–2018. However, a limited number of researches investigate the linkage between inflation instability and the environment. For empirical analysis, econometric methods namely cross-sectional test statistics for examining the dependency, cross-sectionally augmented Dickey-Fuller (CADF) and cross-sectional Im, Pesaran, and Shin (CIPS) for the panel unit root, Westerlund technique for the long-run relationship, and Fully Modified Ordinary Least Square (FMOLS) to estimate the long-run coefficients have adopted. Additionally, the Dumitrescu and Hurlin panel causality test is applied to investigate the causal nexus among the panel data series. The empirical finding depicts that inflation instability improves environmental performance implying that higher price volatility creates uncertainty that discourages investment projects and consumption, hence improves environmental quality. However, the results indicate that financial development stimulates pollution emissions and degrades environmental condition. Based on these findings, the study opens up innovative intuitions for policymakers to support a robust role of economic stability in attaining targets relevant to pollution reduction.

Asymmetric effects of inflation instability and GDP growth volatility on environmental quality in Pakistan.

This study inspects the empirical association between inflation instability, GDP growth volatility, and the environmental quality in Pakistan, covering the period 1975-2018 by using an asymmetric autoregressive distributed lag (ARDL) methodological approach. The asymmetric ARDL results document that positive and negative shocks of inflation instability have different effects on environmental quality. Negative shocks of inflation instability have a positive influence on carbon dioxide emissions (CO2) and nitrous oxide emissions (N2O), while positive shocks of inflation instability have insignificant effects in the long run. Asymmetric findings also suggest that positive and negative fluctuations in GDP growth volatility affect CO2 and N2O emissions differently, while they have insignificant results on methane emissions (CH4) in the long run. Additionally, in the short run, positive and negative shocks of inflation instability and GDP growth volatility behave differently in terms of their impact on pollution emissions. Based on these findings, the study opens up innovative intuitions for policymakers to support a robust role of economic stability in attaining targets relevant to pollution reduction.

Does the Volatility of Macroeconomic Variables Depress The Profitability of Islamic Banking?

Islamic banking in Indonesia has been growing rapidly since 2010. The profitability of Islamic bank depends on Islamic bank characteristics and macroeconomic condition. As a country with an open economy, macroeconomic conditions are very volatile. Through the theory of exchange rate pass through, the exchange rate fluctuation affects domestic prices so that it affects the profits of Islamic bank. This study analyzes the impact of the instability of the macroeconomic variables, namely the exchange rate and inflation on the profitability of Islamic bank. The instability of inflation and exchange rate are measured using the GARCH (Generalized Autoregressive Conditional Heteroskedasticity). This study applies ARDL (Autoregressive Distributed Lag Model). The data used is monthly data starting from January 2011 to June 2018. The results of the study show that the exchange rate and inflation instability depress the profitability of Islamic banki. More interestingly, instability of inflation has a greater negative impact than the instability of exchange rate on Islamic bank profit. The most Islamic bank characteristics influencing Islamic banking profit was bad financing as known as a non performing financing (NPF).

Primordial black holes from the preheating instability in single-field inflation

After the end of inflation, the inflaton field oscillates around a local minimum of its potential and decays into ordinary matter. These oscillations trigger a resonant instability for cosmological perturbations with wavelengths that exit the Hubble radius close to the end of inflation. In this paper, we study the formation of Primordial Black Holes (PBHs) at these enhanced scales. We find that the production mechanism can be so efficient that PBHs subsequently dominate the content of the universe and reheating proceeds from their evaporation. Observational constraints on the PBH abundance also restrict the duration of the resonant instability phase, leading to tight limits on the reheating temperature that we derive. We conclude that the production of PBHs during reheating is a generic and inevitable property of the simplest inflationary single-field models, and does not require any fine tuning of the inflationary potential.