Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Subject: search.filters.subject.Inflation

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  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Modeling Cosmological Perturbations of Thermal Inflation
    (IOP Publishing, 2024) Bae, Jeong-Myeong; Hong, Sungwook E.; Zoe, Heeseung
    We consider a simple system consisting of matter, radiation and vacuum components to model the impact of thermal inflation on the evolution of primordial perturbations. The vacuum energy magnifies the primordial modes entering the horizon before its domination, making them potentially observable, and the resulting transfer function reflects the phase changes and energy contents. To determine the transfer function, we follow the curvature perturbation from well outside the horizon during radiation domination to well outside the horizon during vacuum domination and evaluate it on a constant radiation density hypersurface, as is appropriate for the case of thermal inflation. The shape of the transfer function is determined by the ratio of vacuum energy to radiation at matter-radiation equality, which we denote by upsilon , and has two characteristic scales, ka and kb , corresponding to the horizon sizes at matter radiation equality and the beginning of the inflation, respectively. If upsilon MUCH LESS-THAN1 , the Universe experiences radiation, matter and vacuum domination eras and the transfer function is flat for kMUCH LESS-THANkb , oscillates with amplitude 1/5 for kbMUCH LESS-THANkMUCH LESS-THANka and oscillates with amplitude 1 for k >> ka . For upsilon >> 1 , the matter domination era disappears, and the transfer function reduces to being flat for kMUCH LESS-THANkb and oscillating with amplitude 1 for k >> kb .
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Regional Inflation Persistence in Turkey
    (John Wiley and Sons Inc., 2021) Duran, Hasan Engin; Dindaroğlu, Burak
    The purpose of the current study is to investigate the degree of inflation persistence, its geographical variation, sources of cross-regional variation, and presence of geographical/sectoral aggregation bias in national monetary policy. Our data set covers 26 NUTS-2 level Turkish regions and monthly CPI inflation over the period 2003-2019. We first estimate the degree of regional inflation persistence by autoregressive regressions, check its robustness against the presence of structural breaks (by Bai-Perron's algorithm) and nonlinearities (by Markovian Regime Switching regressions). Second, we examine the possibility of geographical and sectoral aggregation bias. Third, we investigate the cross-regional determinants of inflation persistence by panel data analysis, employing hybrid-effects spatial panel regressions. We analyze the direct and indirect effects of the determinants and test for regional spillover effects. Three main results are obtained. First, estimated persistence degrees are heterogeneous across regions. The geographical pattern is empirically robust against structural breaks and nonlinearities. We find that inflation persistence is distributed in a spatially correlated manner. Second, when sectoral and regional aggregation bias is tested, only sectoral aggregation indicates a considerable level of bias. Third, we find that the presence of large firms in the region and a higher share of agricultural output in GDP leads to lower persistence, while an increased share of industrial output, and increased trade volume leads to higher inflation persistence. Moreover, we find spatial spillovers of price variability evident in regression analysis. From a policy standpoint, it is required that structural policy programs are targeted to maintain flexibility in the regions where persistence is high (i.e., providing market entry/exit, institutional quality, policy credibility, stimulation of SMEs). Moreover, sectors that have high persistence, such as Hotels and Restaurants (persistence degree 0.55) and Health Services (0.39) should be weighted more in CPI calculations.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 11
    Separate Einstein-Eddington Spaces and the Cosmological Constant
    (John Wiley and Sons Inc., 2016) Azri, Hemza
    Based on Eddington affine variational principle on a locally product manifold, we derive the separate Einstein space described by its Ricci tensor. The derived field equations split into two field equations of motion that describe two maximally symmetric spaces with two cosmological constants. We argue that the invariance of the bi-field equations under projections on the separate spaces, may render one of the cosmological constants to zero. We also formulate the model in the presence of a scalar field. The resulted separate Einstein-Eddington spaces maybe considered as two states that describe the universe before and after inflation. A possibly interesting affine action for a general perfect fluid is also proposed. It turns out that the condition which leads to zero cosmological constant in the vacuum case, eliminates here the effects of the gravitational mass density of the perfect fluid, and the dynamic of the universe in its final state is governed by only the inertial mass density of the fluid.