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1
GERMÁN, G., e A. DE LA MACORRA. "INFLATION AT THE MAXIMA OF SYMMETRIC POTENTIALS". International Journal of Modern Physics A 20, n. 28 (10 novembre 2005): 6451–59. http://dx.doi.org/10.1142/s0217751x05025541.
Testo completoAbstract (sommario):
We construct a two-stage inflationary model which can accommodate early inflation at a scale Λ1 as well as a second stage of inflation at Λ2 with a single scalar field ϕ. We use a symmetric potential, valid in a frictionless world, in which the two inflationary periods have exactly the same scale, i.e. Λ1 = Λ2. However, we see today Λ1 ≫ Λ2 due to the friction terms (expansion of the universe and interaction with matter). These type of models can be motivated from supergravity. Inflation occurs close to the maxima of the potential. As a consequence both inflations are necessarily finite. This opens the interesting possibility that the second inflation has already or is about to end. A first inflation is produced when fluctuations displace the inflaton field from its higher maximum rolling down the potential as in new inflation. Instead of rolling towards a global minimum the inflaton approaches a lower maximum where a second inflation takes place.
2
Salvio, Alberto. "Natural-scalaron inflation". Journal of Cosmology and Astroparticle Physics 2021, n. 10 (1 ottobre 2021): 011. http://dx.doi.org/10.1088/1475-7516/2021/10/011.
Testo completoAbstract (sommario):
Abstract A pseudo Nambu-Goldstone boson (such as an axion-like particle) is a theoretically well-motivated inflaton as it features a naturally flat potential (natural inflation). This is because Goldstone's theorem protects its potential from sizable quantum corrections. Such corrections, however, generically generates an R 2 term in the action, which leads to another inflaton candidate because of the equivalence between the R 2 term and a scalar field, the scalaron, with a quasi flat potential (Starobinsky inflation). Here it is investigated a new multifield scenario in which both the scalaron and a pseudo Nambu-Goldstone boson are active (natural-scalaron inflation). For generality, also a non-minimal coupling is included, which is shown to emerge from microscopic theories. It is demonstrated that a robust inflationary attractor is present even when the masses of the two inflatons are comparable. Moreover, the presence of the scalaron allows to satisfy all observational bounds in a large region of the parameter space, unlike what happens in pure-natural inflation.
3
Watson, Scott, Malcolm J. Perry, Gordon L. Kane e Fred C. Adams. "Inflation without inflaton(s)". Journal of Cosmology and Astroparticle Physics 2007, n. 11 (21 novembre 2007): 017. http://dx.doi.org/10.1088/1475-7516/2007/11/017.
Testo completo
4
Arciniega, Gustavo, Pablo Bueno, Pablo A. Cano, José D. Edelstein, Robie A. Hennigar e Luisa G. Jaime. "Cosmic inflation without inflaton". International Journal of Modern Physics D 28, n. 14 (ottobre 2019): 1944008. http://dx.doi.org/10.1142/s0218271819440085.
Testo completoAbstract (sommario):
We propose a novel explanation for universe’s inflationary period. We argue that when the Einstein–Hilbert action is supplemented by an infinite tower of higher-curvature terms — selected order by order by the criterium that they give rise to a well-posed cosmological evolution — the usual Big Bang characteristic of Einstein gravity is replaced by a singularity-free period of exponential growth of the scale factor, which is gracefully connected with standard late-time [Formula: see text]CDM cosmology. No inflaton or any additional fields besides the metric are required.
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LEE, LU-YUN, KINGMAN CHEUNG e CHIA-MIN LIN. "COMMENTS ON SUSY INFLATION MODELS ON THE BRANE". Modern Physics Letters A 25, n. 24 (10 agosto 2010): 2105–10. http://dx.doi.org/10.1142/s0217732310033487.
Testo completoAbstract (sommario):
In this paper we consider a class of inflation models on the brane where the dominant part of the inflaton scalar potential does not depend on the inflaton field value during inflation. In particular, we consider supernatural inflation, its hilltop version, A-term inflation, and supersymmetric (SUSY) D- and F-term hybrid inflation on the brane. We show that the parameter space can be broadened, the inflation scale generally can be lowered, and still possible to have the spectral index ns = 0.96.
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CHOU, CHUNG-HSIEN, e HOI-LAI YU. "DIGITAL ORIGIN OF COSMIC INFLATION". Modern Physics Letters A 25, n. 18 (14 giugno 2010): 1483–89. http://dx.doi.org/10.1142/s0217732310033219.
Testo completoAbstract (sommario):
Assuming our physical universe processes and registers information to determine its dynamical evolution, one can put serious constraints on the cosmology that our universe can bear, in particular, the origin of cosmic inflation. The universe evolves to gain her computation capacity which is linear in time t. On the other hand, the growth in content of degrees of freedom (i.e. by integrating in more galaxies) is as t3/2 through expansion. When the in flux of degrees of freedom of the universe grows beyond some value, the computation capacity of the universe becomes insufficient to determine its evolution, the universe fixes its Hubble radius and inflates away its degrees of freedom within its horizon to regain dynamical evolution. The length of inflation is determined by the communication time required by the universe to become aware of the dropping in the degrees of freedom below some critical value by inflation and is proportional to its Hubble radius. We predict that there can be multiple cosmic inflations. The next inflation era will stop after inflating for a period of 1019 sec if the past inflation period of our universe was 10-33 sec.
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Narita, Yuma, Fuminobu Takahashi e Wen Yin. "QCD axion hybrid inflation". Journal of Cosmology and Astroparticle Physics 2023, n. 12 (1 dicembre 2023): 039. http://dx.doi.org/10.1088/1475-7516/2023/12/039.
Testo completoAbstract (sommario):
Abstract When the inflaton is coupled to the gluon Chern-Simons term for successful reheating, mixing between the inflaton and the QCD axion is generally expected given the solution of the strong CP problem by the QCD axion. This is particularly natural if the inflaton is a different, heavier axion. We propose a scenario in which the QCD axion plays the role of the inflaton by mixing with heavy axions. In particular, if the energy scale of inflation is lower than the QCD scale, a hybrid inflation is realized where the QCD axion plays the role of the inflaton in early stages. We perform detailed numerical calculations to take account of the mixing effects. Interestingly, the initial misalignment angle of the QCD axion, which is usually a free parameter, is determined by the inflaton dynamics. It is found to be close to π in simple models. This is the realization of the pi-shift inflation proposed in previous literature, and it shows that QCD axion dark matter and inflation can be closely related. The heavy axion may be probed by future accelerator experiments.
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Morishita, Yukiyoshi, Tomo Takahashi e Shuichiro Yokoyama. "Multi-chaotic inflation with and without spectator field". Journal of Cosmology and Astroparticle Physics 2022, n. 07 (1 luglio 2022): 042. http://dx.doi.org/10.1088/1475-7516/2022/07/042.
Testo completoAbstract (sommario):
Abstract Motivated by the result of Planck+BICEP/Keck recently released, we investigate the consistency of the multi-field inflation models in terms of the spectral index ns and the tensor-to-scalar ratio r. In this study, we focus on double-inflaton models with and without a spectator field. We find that inflaton with a quadratic potential can become viable when three fields with a specific hierarchical mass spectrum are realized such that two fields act as inflatons and the other one is the spectator. We also discuss the conditions to avoid the fine-tuning, by careful study of how the prediction depends on the background trajectory in the inflaton-field space.
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Salunkhe, Bhavesh, e Anuradha Patnaik. "Inflation Dynamics and Monetary Policy in India: A New Keynesian Phillips Curve Perspective". South Asian Journal of Macroeconomics and Public Finance 8, n. 2 (28 agosto 2019): 144–79. http://dx.doi.org/10.1177/2277978719861186.
Testo completoAbstract (sommario):
The present study estimates various specifications of the New Keynesian Phillips Curve (NKPC) models for India over 1996Q2 to 2017Q2 using Consumer Price Index (CPI) and Wholesale Price Index (WPI) inflation, separately. The empirical results suggest that the data support all the specifications of the Phillips curve models based on both the CPI and WPI inflations. However, the backward looking and hybrid models provide robust results for both the inflation indices. While the forward-looking behaviour dominates the CPI inflation trajectory, the backward-looking behaviour greatly influences the trajectory of WPI inflation. Also, a small-to-moderate degree of persistence is evident in both the CPI and WPI inflation. The output gap, which mainly represents the demand side pressures, turns up the major force determining both the CPI and WPI inflations. Besides the output gap, real effective exchange rate (reer), international crude oil price inflation, global non-fuel commodity price inflation and rainfall have a modest impact on the CPI and WPI inflations. JEL Classification: E12, E52, C36, C14
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Aliraqi, Ali. "Inflation’s Impact on Sudan Exports 1990-2020: An ARDL Approach". World Journal of Entrepreneurship, Management and Sustainable Development 18, n. 6 (10 gennaio 2023): 707–27. http://dx.doi.org/10.47556/j.wjemsd.18.6.2022.2.
Testo completoAbstract (sommario):
Purpose: This study investigates the inflation-export nexus in Sudan over the period 1990- 2020. Design/methodology: The study is based on quantitative and qualitative methods, estimating the export function and measuring the impact of its determinants over a prolonged period of time; the Autoregressive Distributed Lag (ARDL) methodology was used to analyse the co-integration. Findings: Findings have undoubtedly shown inflation’s negative impact on exports over the period 1990-2020. Broadly speaking, the long-term results indicated that the most important variable affecting exports is the gross domestic product (GDP), followed by inflation. Interestingly, the results indicated that the exchange rate was not significant, neither in the short nor in the long term. Implications: The study recommends inflation's control policy as a perquisite for an export development strategy; this overcomes barriers and paves the road for shifting Sudan's economy to productive agendas. Therefore, targeting inflation will contribute to export diversification and strengthening the product's value chain. The research findings reconsider the weight of export’s determinants and will reposition focusing to inflation control rather than exchange rate policy. Originality/value: The paper introduces a new approach in modelling the inflation-export nexus: (1) elaborate on export's determinants and their weights; and (2) recommending guidelines to adapt inflation policy with export development strategy.
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Hossain, Wali. "Quintessential inflation: A unified scenario of inflation and dark energy". EPJ Web of Conferences 168 (2018): 04007. http://dx.doi.org/10.1051/epjconf/201816804007.
Testo completoAbstract (sommario):
Quintessential inflation unifies inflation and late time acceleration by a single scalar field. Such a scenario, with canonical and non-canonical scalar fields, has been discussed. The scalar field behaves as an inflaton field during inflation and as a quintessence field during late time. Also the predictions of the models has been compared with the recent Planck data.
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Richardson, C. A. "Power spectra of inspiratory nerve activity with lung inflations in cats". Journal of Applied Physiology 64, n. 4 (1 aprile 1988): 1709–20. http://dx.doi.org/10.1152/jappl.1988.64.4.1709.
Testo completoAbstract (sommario):
To investigate the effect of lung inflations on the high-frequency synchrony (70-122 Hz) observed in the inspiratory activity of respiratory motor nerves of decerebrate cats, I applied a step increase in lung inflation pressure at fixed delays into the inspiratory phase and computed power spectra of phrenic neurograms before and during inflation. In 25 decerebrate paralyzed cats the frequency of the high spectral peak was 92.3 +/- 11.1 Hz before and 105.3 +/- 12.1 Hz during the step in inflation pressure, shifting upward by 13.0 +/- 6.0 Hz. For 8 of the 25 cats, the recurrent laryngeal and phrenic neurograms were recorded simultaneously. The high spectral peak was present during inspiration in the recurrent laryngeal power spectra and coherent with the high peak in the phrenic power spectra. In response to lung inflation, the high peak disappeared from the power spectra of the recurrent laryngeal nerve as the inspiratory activity was inhibited; a shift upward in frequency was not detectable. Comparing inspiratory times (TI, based on the phrenic neurograms) for breaths with no lung inflations to those for breaths with lung inflations, I found that lung inflations early in inspiration caused a decrease in TI, lung inflations at intermediates times had no effect on TI, and lung inflations late in inspiration caused an increase in TI. Despite lung inflation decreasing, not affecting, or increasing inspiratory duration and amplitude of the phrenic neurogram, lung inflation always caused a shift upward in the high-frequency peak of the phrenic power density. The fact that lung inflation, a powerful respiratory stimulus, affected the frequency of the high peak in a consistent manner suggests that the high-frequency synchrony is an important and robust feature of the central respiratory pattern generator.
13
Drewes, Marco, Lei Ming e Isabel Oldengott. "LiteBIRD and CMB-S4 sensitivities to reheating in plateau models of inflation". Journal of Cosmology and Astroparticle Physics 2024, n. 05 (1 maggio 2024): 081. http://dx.doi.org/10.1088/1475-7516/2024/05/081.
Testo completoAbstract (sommario):
Abstract We study the sensitivity of LiteBIRD and CMB-S4 to the reheating temperature and the inflaton coupling in three types of plateau-potential models of inflation, namely mutated hilltop inflation, radion gauge inflation, and α-attractor T models. We first find relations between model parameters and CMB observables in all models. We then perform Monte Carlo Markov Chain based forecasts to quantify the information gain on the reheating temperature, the inflaton coupling, and the scale of inflation that can be achieved with LiteBIRD and CMB-S4, assuming a fiducial tensor-to-scalar ratio r̅ ∼ 0.02 and neglecting foreground contamination of the B-mode polarization spectrum. We compare the results of the forecasts to those obtained from a recently proposed simple analytic method. We find that both LiteBIRD and CMB-S4 can simultaneously constrain the scale of inflation and the reheating temperature in all three types of models. They can for the first time obtain both an upper and lower bound on the latter, comprising the first ever measurement of the big bang temperature. In the mutated hilltop inflation and radion gauge inflation models this can be translated into a measurement of the inflaton coupling in parts of the parameter space. Constraining this microphysical parameter will help to understand how these models of inflation may be embedded into a more fundamental theory of particle physics.
14
Yang, Hyun Seok. "Emergent Spacetime and Cosmic Inflation". Universe 10, n. 3 (21 marzo 2024): 150. http://dx.doi.org/10.3390/universe10030150.
Testo completoAbstract (sommario):
We present a novel background-independent framework for cosmic inflation, starting with a matrix model. In this framework, inflation is portrayed as a dynamic process responsible for the generation of both space and time. This stands in contrast to conventional inflation, which is characterized as a mere (exponential) expansion of an already existing spacetime, driven by the vacuum energy associated with an inflaton field. We observe that the cosmic inflation is triggered by the condensate of Planck energy into a vacuum and responsible for the dynamical emergence of spacetime. The emergent spacetime picture admits a background-independent formulation so that the inflation is described by a conformal Hamiltonian system which requires neither an inflaton field nor an ad hoc inflation potential. This implies that the emergent spacetime may incapacitate all the rationales to introduce the multiverse hypothesis.
15
Kaplan, David E., e Neal Weiner. "Little inflatons and gauge inflation". Journal of Cosmology and Astroparticle Physics 2004, n. 02 (4 febbraio 2004): 005. http://dx.doi.org/10.1088/1475-7516/2004/02/005.
Testo completo
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ALLAHVERDI, ROUZBEH. "INFLATION AND THE MINIMAL SUPERSYMMETRIC STANDARD MODEL". Modern Physics Letters A 23, n. 33 (30 ottobre 2008): 2799–809. http://dx.doi.org/10.1142/s0217732308028557.
Testo completoAbstract (sommario):
There is strong evidence from cosmological data that the universe underwent an epoch of superluminal expansion called inflation. A satisfactory embedding of inflation in fundamental physics has been an outstanding problem at the interface of cosmology and high energy physics. We show how inflation can be realized within the Minimal Supersymmetric Standard Model (MSSM). The inflaton candidates are two specific combinations of supersymmetric partners of quarks and leptons. MSSM inflation occurs at a low scale and generates perturbations in the range experimentally allowed by the latest data from Wilkinson Microwave Anisotropy Probe (WMAP). The parameter space for inflation is compatible with supersymmetric dark matter, and the Large Hadron Collider (LHC) is capable of discovering the inflaton candidates in the allowed regions of parameter space.
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Barnaby, Neil. "Non-Gaussianity from Particle Production during Inflation". Advances in Astronomy 2010 (2010): 1–40. http://dx.doi.org/10.1155/2010/156180.
Testo completoAbstract (sommario):
In a variety of models the motion of the inflaton may trigger the production of some non-inflaton particles during inflation, for example via parametric resonance or a phase transition. Such models have attracted interest recently for a variety of reasons, including the possibility of slowing the motion of the inflaton on a steep potential. In this review we show that interactions between the produced particles and the inflaton condensate can lead to a qualitatively new mechanism for generating cosmological fluctuations from inflation. We illustrate this effect using a simple prototype modelg2(ϕ−ϕ0)2χ2for the interaction between the inflaton,ϕ, and iso-inflaton,χ. Such interactions are quite natural in a variety of inflation models from supersymmetry and string theory. Using both lattice field theory and analytical calculations, we study the production ofχparticles and their subsequent rescatterings off the condensateϕ(t), which generates bremsstrahlung radiation of light inflaton fluctuationsδϕ. This mechanism leads to observable features in the primordial power spectrum. We derive observational constraints on such features and discuss their implications for popular models of inflation. Inflationary particle production also leads to a very novel kind of nongaussian signature which may be observable in future missions.
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Anisimov, Alexey, Yannick Bartocci e Fedor L. Bezrukov. "Inflaton mass in the νMSM inflation". Physics Letters B 671, n. 2 (gennaio 2009): 211–15. http://dx.doi.org/10.1016/j.physletb.2008.12.028.
Testo completo
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Nakayama, Kazunori, e Fuminobu Takahashi. "Alchemical inflation: inflaton turns into Higgs". Journal of Cosmology and Astroparticle Physics 2012, n. 11 (5 novembre 2012): 007. http://dx.doi.org/10.1088/1475-7516/2012/11/007.
Testo completo
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Thio, Marta, Jennifer A. Dawson, Kelly J. Crossley, Timothy J. Moss, Charles C. Roehr, Graeme R. Polglase, Peter G. Davis e Stuart B. Hooper. "Delivery of positive end-expiratory pressure to preterm lambs using common resuscitation devices". Archives of Disease in Childhood - Fetal and Neonatal Edition 104, n. 1 (2 marzo 2018): F83—F88. http://dx.doi.org/10.1136/archdischild-2017-314064.
Testo completoAbstract (sommario):
BackgroundIn neonatal resuscitation, a ventilation device providing positive end-expiratory pressure (PEEP) is recommended. There is limited information about PEEP delivery in vivo, using different models of self-inflating bag (SIB) at different inflation rates and PEEP settings.MethodsWe compared PEEP delivery to intubated preterm lambs using four commonly available models of paired SIBs and PEEP valves, with a T-piece, with gas flow of 8 L/min. Peak inspiratory pressure inflations of 30 cmH2O, combined with set PEEP of 5, 7 and 10 cmH2O, were delivered at rates of 20, 40 and 60/min. These combinations were repeated without gas flow. We measured mean PEEP, maximum and minimum PEEP, and its difference (PEEP reduction).ResultsA total of 3288 inflations were analysed. The mean PEEP delivered by all SIBs was lower than set PEEP (P<0.001), although some differences were <0.5 cmH2O. In 55% of combinations, the presence of gas flow resulted in increased PEEP delivery (range difference 0.3–2 cmH2O). The mean PEEP was closer to set PEEP with faster inflation rates and higher set PEEPs. The mean (SD) PEEP reduction was 3.9 (1.6), 8.2 (1.8), 2 (0.6) and 1.1 (0.6) cmH2O with the four SIBs, whereas it was 0.5 (0.2) cmH2O with the T-piece.ConclusionsPEEP delivery with SIBs depends on the set PEEP, inflation rate, device model and gas flow. At recommended inflation rates of 60/min, some devices can deliver PEEP close to the set level, although the reduction in PEEP makes some SIBs potentially less effective for lung recruitment than a T-piece.
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LAZARIDES, GEORGE. "HYBRID INFLATION FOLLOWED BY MODULAR INFLATION". International Journal of Modern Physics A 22, n. 31 (20 dicembre 2007): 5747–59. http://dx.doi.org/10.1142/s0217751x07038980.
Testo completoAbstract (sommario):
Inflationary models with a superheavy scale F-term hybrid inflation followed by an intermediate scale modular inflation are considered. The restrictions on the power spectrum [Formula: see text] of curvature perturbation and the spectral index ns from the recent data within the power-law cosmological model with cold dark matter and a cosmological constant can be met provided that the number of e-foldings N HI * suffered by the pivot scale k* = 0.002/ Mpc during hybrid inflation is suitably restricted. The additional e-foldings needed for solving the horizon and flatness problems are generated by modular inflation with a string axion as inflaton. For central values of [Formula: see text] and ns, the grand unification scale comes out, in the case of standard hybrid inflation, close to its supersymmetric value M GUT ≃ 2.86 × 1016 GeV , the relevant coupling constant is relatively large (≈ 0.005 – 0.14), and 10 ≲ N HI * ≲ 21.7. In the shifted [smooth] hybrid inflation case, the grand unification scale can be identified with M GUT for N HI * ≃ 21 [N HI * ≃ 18].
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Antoniadis, Ignatios. "Inflation from supersymmetry breaking". International Journal of Modern Physics A 33, n. 31 (10 novembre 2018): 1844021. http://dx.doi.org/10.1142/s0217751x18440219.
Testo completoAbstract (sommario):
I discuss a general class of models where the inflation is driven by supersymmetry breaking with the superpartner of the goldstino (sgoldstino) playing the role of the inflaton. Imposing an R-symmetry allows to satisfy easily the slow-roll conditions, avoiding the so-called [Formula: see text]-problem, and leads to two different classes of small field inflation models; they are characterized by an inflationary plateau around the maximum of the scalar potential, where R-symmetry is either restored or spontaneously broken, with the inflaton rolling down to a minimum describing the present phase of our Universe. Inflation can be driven by either an F- or a D-term, while the minimum has a positive tunable vacuum energy. The models agree with cosmological observations and in the simplest case predict a tensor-to-scalar ratio of primordial perturbations [Formula: see text] and an inflation scale [Formula: see text].
23
Lin, Chia-Min. "Uniform rate inflation". Journal of Cosmology and Astroparticle Physics 2023, n. 04 (1 aprile 2023): 037. http://dx.doi.org/10.1088/1475-7516/2023/04/037.
Testo completoAbstract (sommario):
Abstract In this work, I consider an inflation model with a quadratic potential and a negative cosmological constant. An analytical solution of the equation of motion for the inflaton field is found without slow-roll approximation. The result is that the inflation field is rolling at a constant speed. The prediction for cosmological perturbation is calculated.
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Yamaguchi, Masahide, Kenji Kadota e Teruhiko Kawano. "D-term chaotic inflation in supergravity and leptogenesisThis paper was prsented at the Theory CANADA 4 conference, held at the Centre de Recherches Mathématiques at the Université de Montréal, Québec, Canada on 4–7 June 2008." Canadian Journal of Physics 87, n. 3 (marzo 2009): 195–99. http://dx.doi.org/10.1139/p08-100.
Testo completoAbstract (sommario):
We review a model of D-term dominated chaotic inflation in supergravity. The F-flat direction present in this model is lifted by the dominant D-term, which leads to chaotic inflation and subsequent reheating. The leptogenesis scenario via the inflaton decay in this D-term chaotic inflation scenario is also discussed.
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Davis, Anne-Christine, Philippe Brax e Carsten van de Bruck. "Brane inflation and defect formation". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, n. 1877 (5 giugno 2008): 2833–42. http://dx.doi.org/10.1098/rsta.2008.0065.
Testo completoAbstract (sommario):
Brane inflation and the production of topological defects at the end of the inflationary phase are discussed. After a description of the inflationary set-up, we discuss the properties of the cosmic strings produced at the end of inflation. Specific examples of brane inflation are described, such as D − , D 3/ D 7 and modular inflations.
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AGARWAL, NIKITA. "Inflation of strongly connected networks". Mathematical Proceedings of the Cambridge Philosophical Society 150, n. 2 (12 gennaio 2011): 367–84. http://dx.doi.org/10.1017/s0305004110000654.
Testo completoAbstract (sommario):
AbstractA coupled cell network is an inflation of if the dynamics of is embedded in as a quotient network. We give necessary and sufficient conditions for the existence of a strongly connected inflation of a strongly connected network. We provide a simple algorithm for the construction of a strongly connected inflation as a sequence of simple inflations.
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Okano, So, e Tomohiro Fujita. "When does the Schwinger preheating occur?" Journal of Cosmology and Astroparticle Physics 2022, n. 03 (1 marzo 2022): 040. http://dx.doi.org/10.1088/1475-7516/2022/03/040.
Testo completoAbstract (sommario):
Abstract When the inflaton couples to photons and amplifies electric fields, charged particles produced via the Schwinger effect can dominate the universe after inflation, which is dubbed as the Schwinger preheating. Using the hydrodynamic approach for the Boltzmann equation, we numerically study two cases, the Starobinsky inflation model with the kinetic coupling and the Watanabe-Kanno-Soda inflation model. The Schwinger preheating is not observed in the latter model but occurs for a sufficiently large inflaton-photon coupling in the first model. We analytically address its condition and derive a general attractor solution of the electric fields. The occurrence of the Schwinger preheating in the first model is determined by whether the electric fields enter the attractor solution during inflation or not.
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Berera, Arjun. "The Warm Inflation Story". Universe 9, n. 6 (6 giugno 2023): 272. http://dx.doi.org/10.3390/universe9060272.
Testo completoAbstract (sommario):
Warm inflation has normalized two ideas in cosmology, that in the early universe the initial primordial density perturbations generally could be of classical rather than quantum origin and that during inflation, particle production from interactions amongst quantum field, and its backreaction effects, can occur concurrent with inflationary expansion. When we first introduced these ideas, both were met with resistance, but today they are widely accepted as possibilities with many models and applications based on them, which is an indication of the widespread influence of warm inflation. Open quantum field theory, which has been utilized in studies of warm inflation, is by now a relevant subject in cosmology, in part due to this early work. In this review I first discuss the basic warm inflation dynamics. I then outline how to compute warm inflation dynamics from first-principles quantum field theory (QFT) and in particular how a dissipative term arises. Warm inflation models can have an inflaton mass bigger than the Hubble scale and the inflaton field excursion can remain sub-Planckian, thus overcoming the most prohibitive problems of inflation model building. I discuss the early period of my work in developing warm inflation that helped me arrive at these important features of its dynamics. Inflationary cosmology today is immersed in hypothetical models, which by now are acting as a diversion from reaching any endgame in this field. I discuss better ways to approach model selection and give necessary requirements for a well constrained and predictive inflation model. A few warm inflation models are pointed out that could be developed to this extent. I discuss how, at this stage, more progress would be made in this subject by taking a broader view on the possible early universe solutions that include not just inflation but the diverse range of options.
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Kobayashi, Tatsuo, e Osamu Seto. "Beginning of Universe through large field hybrid inflation". Modern Physics Letters A 30, n. 21 (18 giugno 2015): 1550106. http://dx.doi.org/10.1142/s0217732315501060.
Testo completoAbstract (sommario):
Recent detection of B-mode polarization induced from tensor perturbations by the BICEP2 experiment implies the so-called large field inflation, where an inflaton field takes super-Planckian expectation value during inflation, at a high energy scale. We show however, if another inflation follows hybrid inflation, the hybrid inflation can generate a large tensor perturbation with not super-Planckian but Planckian field value. This scenario would relax the tension between BICEP2 and Planck concerning the tensor-to-scalar ratio, because a negative large running can also be obtained for a certain number of e-fold of the hybrid inflation. A natural interpretation of a large gravitational wave mode with or without the scalar spectral running might be multiple inflation in the early Universe.
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Montefalcone, Gabriele, Rudnei O. Ramos, Gustavo S. Vicente e Katherine Freese. "Defying eternal inflation in warm inflation with a negative running". Journal of Cosmology and Astroparticle Physics 2024, n. 02 (1 febbraio 2024): 006. http://dx.doi.org/10.1088/1475-7516/2024/02/006.
Testo completoAbstract (sommario):
Abstract It was pointed out previously [1] that a sufficiently negative running of the spectral index of curvature perturbations from (ordinary i.e. cold) inflation is able to prevent eternal inflation from ever occurring. Here, we reevaluate those original results, but in the context of warm inflation, in which a substantial radiation component (produced by the inflaton) exists throughout the inflationary period. We demonstrate that the same general requirements found in the context of ordinary (cold) inflation also hold true in warm inflation; indeed an even tinier amount of negative running is sufficient to prevent eternal inflation. This is particularly pertinent, as models featuring negative running are more generic in warm inflation scenarios. Finally, the condition for the existence of eternal inflation in cold inflation — that the curvature perturbation amplitude exceed unity on superhorizon scales — becomes more restrictive in the case of warm inflation. The curvature perturbations must be even larger, i.e. even farther out on the potential, away from the part of the potential where observables, e.g. in the Cosmic Microwave Background, are produced.
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Antoniadis, Ignatios. "Inflation from Supersymmetry Breaking". Universe 5, n. 1 (16 gennaio 2019): 30. http://dx.doi.org/10.3390/universe5010030.
Testo completoAbstract (sommario):
I discuss the possibility that inflation is driven by supersymmetry breaking, with the superpartner of the goldstino (sgoldstino) playing the role of the inflaton. Imposing an R-symmetry to satisfy the slow-roll conditions, avoiding the so-called η -problem, leads to an interesting class of small field inflation models, characterised by an inflationary plateau around the maximum of scalar potential near the origin, where R-symmetry is restored with the inflaton rolling down to a minimum, describing the present phase of the Universe. Inflation can be driven by either an F- or a D-term, while the minimum has a positive tuneable vacuum energy. The models agree with cosmological observations and, in the simplest case, predict a rather small tensor-to-scalar ratio of primordial perturbations. This talk is an extended version of an earlier review (Antoniadis, 2018).
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BASTERO-GIL, MAR, e ARJUN BERERA. "WARM INFLATION MODEL BUILDING". International Journal of Modern Physics A 24, n. 12 (10 maggio 2009): 2207–40. http://dx.doi.org/10.1142/s0217751x09044206.
Testo completoAbstract (sommario):
We review the main aspects of the warm inflation scenario, focusing on the inflationary dynamics and the predictions related to the primordial spectrum of perturbations, to be compared with the recent cosmological observations. We study in detail three different classes of inflationary models, chaotic, hybrid models and hilltop models, and discuss their embedding into supersymmetric models and the consequences for model building of the warm inflationary dynamics based on first principles calculations. Due to the extra friction term introduced in the inflaton background evolution generated by the dissipative dynamics, inflation can take place generically for smaller values of the field, and larger values of couplings and masses. When the dissipative dynamics dominates over the expansion, in the so-called strong dissipative regime, inflation proceeds with sub-Planckian inflaton values. Models can be naturally embedded into a supergravity framework, with SUGRA corrections suppressed by the Planck mass now under control, for a larger class of Kähler potentials. In particular, this provides a simpler solution to the "eta" problem in supersymmetric hybrid inflation, without restricting the Kähler potentials compatible with inflation. For chaotic models dissipation leads to a smaller prediction for the tensor-to-scalar ratio and a less tilted spectrum when compared to the cold inflation scenario. We find in particular that a small component of dissipation renders the quartic model now consistent with the current CMB data.
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BOYANOVSKY, D., C. DESTRI, H. J. DE VEGA e N. G. SANCHEZ. "THE EFFECTIVE THEORY OF INFLATION IN THE STANDARD MODEL OF THE UNIVERSE AND THE CMB+LSS DATA ANALYSIS". International Journal of Modern Physics A 24, n. 20n21 (20 agosto 2009): 3669–864. http://dx.doi.org/10.1142/s0217751x09044553.
Testo completoAbstract (sommario):
Inflation is today a part of the Standard Model of the Universe supported by the cosmic microwave background (CMB) and large scale structure (LSS) datasets. Inflation solves the horizon and flatness problems and naturally generates density fluctuations that seed LSS and CMB anisotropies, and tensor perturbations (primordial gravitational waves). Inflation theory is based on a scalar field φ (the inflaton) whose potential is fairly flat, leading to a slow-roll evolution. This review focuses on the following new aspects of inflation. We present the effective theory of inflation à la Ginsburg and Landau, in which the inflaton potential is a polynomial in the field φ and has the universal form [Formula: see text], where [Formula: see text], M ≪ M Pl is the scale of inflation and N ~ 60 is the number of e-folds since the cosmologically relevant modes exit the horizon till inflation ends. The slow-roll expansion becomes a systematic 1/N expansion and the inflaton couplings become naturally small as powers of the ratio (M/M Pl )2. The spectral index and the ratio of tensor/scalar fluctuations are [Formula: see text], [Formula: see text], while the running index turns out to be [Formula: see text] and therefore can be neglected. The energy scale of inflation M ~ 0.7 × 1016 GeV is completely determined by the amplitude of the scalar adiabatic fluctuations. A complete analytic study plus the Monte Carlo Markov chain (MCMC) analysis of the available CMB+LSS data (including WMAP5) with fourth degree trinomial potentials showed: (a) the spontaneous breaking of the φ → - φ symmetry of the inflaton potential; (b) a lower bound for r in new inflation: r > 0.023 (95% CL) and r > 0.046 (68 CL); (c) the preferred inflation potential is a double-well, even function of the field with a moderate quartic coupling yielding as the most probable values ns ≃ 0.964, r ≃ 0.051. This value for r is within reach of forthcoming CMB observations. The present data in the effective theory of inflation clearly prefer new inflation. Study of higher degree inflaton potentials shows that terms of degree higher than 4 do not affect the fit in a significant way. In addition, a horizon exit happens for [Formula: see text], making higher order terms in the potential w negligible. We summarize the physical effects of generic initial conditions (different from Bunch–Davies) on the scalar and tensor perturbations during slow roll and introduce the transfer function D(k), which encodes the observable initial condition effects on the power spectra. These effects are more prominent in the low CMB multipoles: a change in the initial conditions during slow roll can account for the observed CMB quadrupole suppression. Slow-roll inflation is generically preceded by a short, fast-roll stage. Bunch–Davies initial conditions are the natural initial conditions for the fast-roll perturbations. During fast roll, the potential in the wave equations of curvature and tensor perturbations is purely attractive and leads to a suppression of the curvature and tensor CMB quadrupoles. An MCMC analysis of the WMAP+SDSS data including fast roll shows that the quadrupole mode exits the horizon about 0.2 e-fold before fast roll ends and its amplitude gets suppressed. In addition, fast roll fixes the initial inflation redshift to be z init = 0.9 × 1056 and the total number of e-folds of inflation to be N tot ≃ 64. Fast roll fits the TT, the TE and the EE modes well, reproducing the quadrupole suppression. A thorough study of the quantum loop corrections reveals that they are very small and are controlled by powers of (H/M Pl )2 ~ 10-9, a conclusion that validates the reliability of the effective theory of inflation. The present review shows how powerful the Ginsburg–Landau effective theory of inflation is in predicting observables that are being or will soon be contrasted with observations.
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Drewes, Marco. "Measuring the inflaton coupling in the CMB". Journal of Cosmology and Astroparticle Physics 2022, n. 09 (1 settembre 2022): 069. http://dx.doi.org/10.1088/1475-7516/2022/09/069.
Testo completoAbstract (sommario):
Abstract We study the perspectives to extract information about the microphysical parameters that governed the reheating process after cosmic inflation from CMB data. We identify conditions under which the inflaton coupling to other fields can be constrained for a given model of inflation without having to specify the details of the particle physics theory within which this model is realised. This is possible when the effective potential during reheating is approximately parabolic, and when the coupling constants are smaller than an upper bound that is determined by the ratios between the inflaton mass and the Planck mass or the scale of inflation. We consider scalar, Yukawa, and axion-like interactions and estimate that these conditions can be fulfilled if the inflaton coupling is comparable to the electron Yukawa coupling or smaller, and if the inflaton mass is larger than 105 GeV. Constraining the order of magnitude of the coupling constant requires measuring the scalar-to-tensor ratio at the level of 10-3, which is possible with future CMB observatories. Such a measurement would provide an important clue to understand how a given model of inflation may be embedded into a more fundamental theory of nature.
35
Chowdhry, Bhagwan, Richard Roll e Yihong Xia. "Extracting Inflation from Stock Returns to Test Purchasing Power Parity". American Economic Review 95, n. 1 (1 febbraio 2005): 255–76. http://dx.doi.org/10.1257/0002828053828554.
Testo completoAbstract (sommario):
Relative purchasing power parity (PPP) holds for pure price inflations, which affect prices of all goods and services by the same proportion, while leaving relative prices unchanged. Pure price inflations also affect nominal returns of all traded financial assets by exactly the same amount. Recognizing that relative PPP may not hold for the official inflation data constructed from commodity price indices because of relative price changes and other frictions that cause prices to be “sticky,” we provide a novel method for extracting a proxy for realized pure price inflation from stock returns. We find strong support for relative PPP in the short run using the extracted inflation measures.
36
Stein, Nina K., e William H. Kinney. "Simple single-field inflation models with arbitrarily small tensor/scalar ratio". Journal of Cosmology and Astroparticle Physics 2023, n. 03 (1 marzo 2023): 027. http://dx.doi.org/10.1088/1475-7516/2023/03/027.
Testo completoAbstract (sommario):
Abstract We construct a family of simple single-field inflation models consistent with Planck / BICEP Keck bounds which have a parametrically small tensor amplitude and no running of the scalar spectral index. The construction consists of a constant-roll hilltop inflaton potential with the end of inflation left as a free parameter induced by higher-order operators which become dominant late in inflation. This construction directly demonstrates that there is no lower bound on the tensor/scalar ratio for simple single-field inflation models.
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Tomberg, Eemeli, e Hardi Veermäe. "Tachyonic preheating in plateau inflation". Journal of Cosmology and Astroparticle Physics 2021, n. 12 (1 dicembre 2021): 035. http://dx.doi.org/10.1088/1475-7516/2021/12/035.
Testo completoAbstract (sommario):
Abstract Plateau inflation is an experimentally consistent framework in which the scale of inflation can be kept relatively low. Close to the edge of the plateau, scalar perturbations are subject to a strong tachyonic instability. Tachyonic preheating is realized when, after inflation, the oscillating inflaton repeatedly re-enters the plateau. We develop the analytic theory of this process and expand the linear approach by including backreaction between the coherent background and growing perturbations. For a family of plateau models, the analytic predictions are confronted with numerical estimates. Our analysis shows that the inflaton fragments in a fraction of an e-fold in all examples supporting tachyonic preheating, generalizing the results of previous similar studies. In these scenarios, the scalar-to-tensor ratio is tiny, r < 10-7.
38
Qi, XinXin, e Hao Sun. "Inflation and dark matter in the Z 5 model". Journal of Cosmology and Astroparticle Physics 2023, n. 05 (1 maggio 2023): 051. http://dx.doi.org/10.1088/1475-7516/2023/05/051.
Testo completoAbstract (sommario):
Abstract We discuss the possibility of unifying dark matter physics and inflation in the Z 5 model of the two-component dark matter. Inflation driven by the two-component dark matter fields can be divided into two cases, singlet dark matter inflation and mixed dark matter inflation, where both two-component play the role of inflaton in the latter case. For dark matter, we focus on the mixed dark matter inflation case. We show a viable parameter space that satisfies the theoretical and dark matter relic density constraint in the case of successful inflation. It turns out that the dark matter density is dominated by the light component, which is consistent with the feature of the Z 5 model of the two-component dark matter.
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Wilkins, A., e A. Cable. "Spectators no more! How even unimportant fields can ruin your Primordial Black Hole model". Journal of Cosmology and Astroparticle Physics 2024, n. 02 (1 febbraio 2024): 026. http://dx.doi.org/10.1088/1475-7516/2024/02/026.
Testo completoAbstract (sommario):
Abstract In this work we terminate inflation during a phase of Constant Roll by means of a waterfall field coupled to the inflaton and a spectator field. The presence of a spectator field means that inflation does not end at a single point, ϕ e, but instead has some uncertainty resulting in a stochastic end of inflation. We find that even modestly coupled spectator fields can drastically increase the abundance of Primordial Black Holes (PBHs) formed by many orders of magnitude. The power spectrum created by the inflaton can be as little as 10-4 during a phase of Ultra Slow-Roll and still form a cosmologically relevant number of PBHs. We conclude that the presence of spectator fields, which very generically will alter the end of inflation, is an effect that cannot be ignored in realistic models of PBH formation.
40
Muders, Thomas, Benjamin Hentze, Stefan Kreyer, Karin Henriette Wodack, Steffen Leonhardt, Göran Hedenstierna, Hermann Wrigge e Christian Putensen. "Measurement of Electrical Impedance Tomography-Based Regional Ventilation Delay for Individualized Titration of End-Expiratory Pressure". Journal of Clinical Medicine 10, n. 13 (30 giugno 2021): 2933. http://dx.doi.org/10.3390/jcm10132933.
Testo completoAbstract (sommario):
Rationale: Individualized positive end-expiratory pressure (PEEP) titration might be beneficial in preventing tidal recruitment. To detect tidal recruitment by electrical impedance tomography (EIT), the time disparity between the regional ventilation curves (regional ventilation delay inhomogeneity [RVDI]) can be measured during controlled mechanical ventilation when applying a slow inflation of 12 mL/kg of body weight (BW). However, repeated large slow inflations may result in high end-inspiratory pressure (PEI), which might limit the clinical applicability of this method. We hypothesized that PEEP levels that minimize tidal recruitment can also be derived from EIT-based RVDI through the use of reduced slow inflation volumes. Methods: Decremental PEEP trials were performed in 15 lung-injured pigs. The PEEP level that minimized tidal recruitment was estimated from EIT-based RVDI measurement during slow inflations of 12, 9, 7.5, or 6 mL/kg BW. We compared RVDI and PEI values resulting from different slow inflation volumes and estimated individualized PEEP levels. Results: RVDI values from slow inflations of 12 and 9 mL/kg BW showed excellent linear correlation (R2 = 0.87, p < 0.001). Correlations decreased for RVDI values from inflations of 7.5 (R2 = 0.68, p < 0.001) and 6 (R2 = 0.42, p < 0.001) mL/kg BW. Individualized PEEP levels estimated from 12 and 9 mL/kg BW were comparable (bias −0.3 cm H2O ± 1.2 cm H2O). Bias and scatter increased with further reduction in slow inflation volumes (for 7.5 mL/kg BW, bias 0 ± 3.2 cm H2O; for 6 mL/kg BW, bias 1.2 ± 4.0 cm H2O). PEI resulting from 9 mL/kg BW inflations were comparable with PEI during regular tidal volumes. Conclusions: PEEP titration to minimize tidal recruitment can be individualized according to EIT-based measurement of the time disparity of regional ventilation courses during slow inflations with low inflation volumes. This sufficiently decreases PEI and may reduce potential clinical risks.
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Caravano, Angelo, Eiichiro Komatsu, Kaloian D. Lozanov e Jochen Weller. "Lattice simulations of inflation". Journal of Cosmology and Astroparticle Physics 2021, n. 12 (1 dicembre 2021): 010. http://dx.doi.org/10.1088/1475-7516/2021/12/010.
Testo completoAbstract (sommario):
Abstract The scalar field theory of cosmological inflation constitutes nowadays one of the preferred scenarios for the physics of the early universe. In this paper we aim at studying the inflationary universe making use of a numerical lattice simulation. Various lattice codes have been written in the last decades and have been extensively used for understating the reheating phase of the universe, but they have never been used to study the inflationary phase itself far from the end of inflation (i.e. about 50 e-folds before the end of inflation). In this paper we use a lattice simulation to reproduce the well-known results of some simple models of single-field inflation, particularly for the scalar field perturbation. The main model that we consider is the standard slow-roll inflation with an harmonic potential for the inflaton field. We explore the technical aspects that need to be accounted for in order to reproduce with precision the nearly scale invariant power spectrum of inflaton perturbations. We also consider the case of a step potential, and show that the simulation is able to correctly reproduce the oscillatory features in the power spectrum of this model. Even if a lattice simulation is not needed in these cases, that are well within the regime of validity of linear perturbation theory, this sets the basis to future work on using lattice simulations to study more complicated models of inflation.
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King, Stephen F., e Xin Wang. "Modular invariant hilltop inflation". Journal of Cosmology and Astroparticle Physics 2024, n. 07 (1 luglio 2024): 073. http://dx.doi.org/10.1088/1475-7516/2024/07/073.
Testo completoAbstract (sommario):
Abstract In this paper we show that it is possible to achieve successful hilltop inflation in which the inflaton is identified as the modulus field in a modular invariant theory. The dilaton plays a crucial role in shaping the potential. Modular invariant gaugino condensation provides the mechanism for the modulus stabilisation after inflation. The inflationary trajectory lies on the lower boundary of the fundamental domain of the modulus field τ. Inflation starts near the fixed point τ = i, and ends at a point near τ = ω, which is the global de Sitter vacuum. We investigate the allowed parameter space for successful modular invariant hilltop inflation.
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Ema, Yohei, e Sarunas Verner. "Cosmological collider signatures of Higgs-R2 inflation". Journal of Cosmology and Astroparticle Physics 2024, n. 04 (1 aprile 2024): 039. http://dx.doi.org/10.1088/1475-7516/2024/04/039.
Testo completoAbstract (sommario):
Abstract We study the cosmological collider signatures in the Higgs-R 2 inflation model. We consider two distinct types of signals: one originating from the inflaton coupling to Standard Model fermions and gauge bosons, and another arising from the isocurvature mode interaction with the inflaton. In the former case, we determine that the signal magnitude is likely too small for detection by upcoming probes, primarily due to suppression by both the Planck scale and slow-roll parameters. However, we provide a detailed computation of the signal which could be potentially applicable to various Higgs inflation variants. For the isocurvature mode signals, we observe that the associated couplings remain unsuppressed when the isocurvature mode is relatively light or comparable to the inflationary scale. In this case, we study the Higgs-R 2 inflation parameter space that corresponds to the quasi-single-field inflation regime and find that the signal strength could be as large as |f NL| > 1, making Higgs-R 2 inflation a viable candidate for observation by future 21-cm surveys.
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Walsh, M. C., e W. A. Carlo. "Sustained inflation during HFOV improves pulmonary mechanics and oxygenation". Journal of Applied Physiology 65, n. 1 (1 luglio 1988): 368–72. http://dx.doi.org/10.1152/jappl.1988.65.1.368.
Testo completoAbstract (sommario):
Effective use of high-frequency oscillatory ventilation (HFOV) may require maintenance of adequate lung volume to optimize gas exchange. To determine the impact of inflation during HFOV, sustained inflation was applied at pressures of 5, 10, and 15 cmH2O above mean airway pressure for 3, 10, and 30 s to 15 intubated, paralyzed, anesthetized rabbits after saline lavage to induce surfactant deficiency. Arterial blood gases were recorded in all rabbits while static compliance, resistance, time constant, and changes in functional residual capacity were recorded using the interrupter technique and plethysmograph in seven rabbits. Parameters were recorded before and 2 min after sustained inflation. Arterial PO2, compliance of the respiratory system, and functional residual capacity increased after sustained inflation at pressure levels of at least 10 cmH2O and 10-s duration. As the presence or duration of a sustained inflation was increased, oxygenation improved (P less than or equal to 0.01), but arterial PCO2 increased as longer sustained inflations were used (P less than or equal to 0.005). Sustained inflations of 5 cmH2O above mean airway pressure or of 3-s duration were ineffective. We conclude that either a critical pressure or duration of sustained inflation is needed to improve oxygenation and pulmonary mechanics during HFOV.
45
PANCHAPAKESAN, N., e SHIV K. SETHI. "EXTENDED INFLATION WITH NONMINIMALLY COUPLED INFLATON FIELD". International Journal of Modern Physics A 07, n. 26 (20 ottobre 1992): 6665–78. http://dx.doi.org/10.1142/s0217751x92003069.
Testo completoAbstract (sommario):
An extended inflation model, in which the inflaton field is nonminimally coupled to the gravity, is discussed. It is shown that the nucleation rate of bubbles, during a phase transition in the inflaton field, can increase as the transition proceeds for a wide range of parameters of the inflaton potential. The bounce action for three possible cases—the strong gravity regime, the thick-walled Coleman-De Luccia bubbles and the thin-walled bubbles—is evaluated. The resulting bubble distribution for all the cases is shown to be in conformity with cosmological constraints for ω<500.
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Bellini, Mauricio. "Fresh Inflation with Nonminimally Coupled Inflaton Field". General Relativity and Gravitation 34, n. 11 (novembre 2002): 1953–61. http://dx.doi.org/10.1023/a:1020784628833.
Testo completo
47
Laycock, Andrew M., e Andrew R. Liddle. "Extended inflation with a curvature-coupled inflaton". Physical Review D 49, n. 4 (15 febbraio 1994): 1827–39. http://dx.doi.org/10.1103/physrevd.49.1827.
Testo completo
48
Juhro, Solikin M., e Bernard Njindan Iyke. "FORECASTING INDONESIAN INFLATION WITHIN AN INFLATION-TARGETING FRAMEWORK: DO LARGE-SCALE MODELS PAY OFF?" Buletin Ekonomi Moneter dan Perbankan 22, n. 4 (31 dicembre 2019): 423–36. http://dx.doi.org/10.21098/bemp.v22i4.1235.
Testo completoAbstract (sommario):
We examine the usefulness of large-scale inflation forecasting models in Indonesiawithin an inflation-targeting framework. Using a dynamic model averaging approachto address three issues the policymaker faces when forecasting inflation, namely,parameter, predictor, and model uncertainties, we show that large-scale modelshave significant payoffs. Our in-sample forecasts suggest that 60% of 15 exogenouspredictors significantly forecast inflation, given a posterior inclusion probability cut-offof approximately 50%. We show that nearly 87% of the predictors can forecast inflationif we lower the cut-off to approximately 40%. Our out-of-sample forecasts suggest thatlarge-scale inflation forecasting models have substantial forecasting power relative tosimple models of inflation persistence at longer horizons.
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Nautz, Dieter, e Juliane Scharff. "Inflation and Relative Price Variability in a Low Inflation Country: Empirical Evidence for Germany". German Economic Review 6, n. 4 (1 dicembre 2005): 507–23. http://dx.doi.org/10.1111/j.1468-0475.2005.00144.x.
Testo completoAbstract (sommario):
Abstract The recent literature on the welfare cost of inflation emphasizes inflation’s effect on the variability of relative prices. Expected and unexpected inflation have both been proposed to increase relative price variability (RPV) and, thereby, to distort the information content of nominal prices. This paper presents new evidence on the impact of inflation on RPV in Germany. Our results indicate that the influence of expected inflation disappears if a credible monetary policy stabilizes inflationary expectations on a low level. Yet the significant impact of unexpected inflation suggests that even low inflation rates can lead to welfare losses by raising RPV above its efficient level.
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Gorbar, E. V., A. I. Momot, I. V. Rudenok, O. O. Sobol, S. I. Vilchinskii e I. V. Oleinikova. "Chirality Production during Axion Inflation". Ukrainian Journal of Physics 68, n. 11 (18 dicembre 2023): 717. http://dx.doi.org/10.15407/ujpe68.11.717.
Testo completoAbstract (sommario):
We study the generation of a chiral charge during the axion inflation, where the pseudoscalar inflaton field φ couples axially to the electromagnetic field via the term (β/Mp)φ E · B with the dimensionless coupling constant β. To describe the evolution of the electromagnetic field and to determine ⟨E·B⟩ sourcing the chiral asymmetry during the inflation due to the chiral anomaly, we employ the gradient-expansion formalism. It operates with a set of vacuum expectation values of the bilinear electromagnetic functions and allows us to consider the backreaction of generated fields on the inflaton evolution, as well as the Schwinger production of charged fermions. In addition, we assume that the produced fermions thermalize and include the chiral magnetic effect contribution to the electric current given by jCME = e2/(2π2)μ5B, where μ5 is the chiral chemical potential which quantifies the produced chiral asymmetry. Solving a set of equations for the inflaton field, scale factor, quadratic functions of the electromagnetic field, and the chiral charge density (chiral chemical potential), we find that the chirality production is quite efficient leading to the generation of a large chiral chemical potential at the end of the axion inflation.