Makale 2020-2029 yılları

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https://kurumsalarsiv.tenmak.gov.tr/handle/20.500.12878/1648

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Browsing Makale 2020-2029 yılları by Organisation Author "Bostan, Nilay"

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    First constraints on Non-minimally coupled Natural and Coleman-Weinberg inflation in the light of massive neutrino self-interactions and Planck+BICEP/Keck
    (SISSA, 2024-07-22) Bostan, Nilay; Roy Choudhuryb, Shouvik
    In this work, for the first time in literature, we compare the predictions of nonminimally coupled Natural and Coleman-Weinberg potentials in the ns − r plane against the constraints from the latest cosmological data in an extended ΛCDM model where we include non-standard self-interactions among massive neutrinos, mediated by a heavy scalar or vector boson. For the inflationary potentials, we consider two different formulations in gravity that are non-minimally coupled to the scalar field of the inflaton: Metric and Palatini. We only consider the self-interaction to be present among τ-neutrinos and only at moderate strengths. This is because strong interactions among τ-neutrinos, or any strength self-interaction among electron- and muon-neutrinos, as well as any strength flavor-universal interactions, are strongly disfavoured from particle physics experiments. In terms of cosmological data, we use the latest public CMB datasets from Planck and BICEP/Keck collaborations, along with other data from CMB lensing, BAO, RSD, and SNe Ia luminosity distance measurements. We find that there are some situations where predictions from the inflationary models are ruled out at more than 2σ by the minimal ΛCDM+r model, but they are allowed in the self-interacting neutrino scenario.
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    Inflation and reheating predictions of minimally coupled β-exponential potential with an R2 term in the Palatini formulation
    (T.C. Türkiye Enerji, Nükleer ve Maden Araştırma Kurumu, 2024-08-29) Bostan, Nilay; Dejrah, Rafid H.
    In this work, we focus on the inflationary predictions of β-exponential potential models, where the field delineating the size of extra-dimension is represented as the inflaton. We include an R2 term in the Palatini gravity since it provides a well-motivated starting point for the analysis of physics at very high energies. Furthermore, the inflaton oscillates around the minimum of the inflation potential until the universe is reheated at the end of the inflationary epoch. This occurs during the reheating phase, at which inflaton decays into the Standard Model particles, which filled the universe. Regardingly, we extend our examination by taking into consideration the reheating effects on inflationary observables. Assuming the standard thermal history after inflation, we present the inflationary predictions, ns,r, dns/d ln k of β-exponential potential with minimal coupling in Palatini R2 gravity by considering the reheating cases. We show that this specific kind of model allows one to study a wide range of predictions to have a better analysis for the inflationary era by adjusting the model parameters, α, β, λ. In addition, different kinds of constraints from a variety of observations, such as BICEP/Keck, Planck 2018, the Baryon Acoustic Oscillations (BAO), as well as future possible detectable constraints by CMB-S4 are taken into consideration in this study. We find that our results are in good agreement with the recent data and sensitivity forecast for the future CMB-S4.
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    Inflation in symmergent metric-Palatini gravity
    (Sissa, 2024-02-21) Bostan, Nilay; Karahan, Canan; Sargın, Ozan
    In this paper, we study the cosmological inflation phenomenon in symmergent gravity theory. Symmergent gravity is a novel framework which merges gravity and the standard model (SM) so that the gravity emerges from the matter loops and restores the broken gauge symmetries along the way. Symmergent gravity is capable of inducing the gravitational constant G and the quadratic curvature coefficient cO from the loop corrections of the matter sector in a flat space-time. In the event that all the matter fields, including the beyond the standard model (BSM) sector, are mass degenerate, the vacuum energy can be expressed in terms of G and cO. The parameter which measures the deviation from the mass degeneracy is dubbed ˆ α. The parameters, cO and ˆ α, of symmergent gravity convey the information about the fermion and boson balance in the matter (SM+BSM) sector in number and in mass, respectively. In our analysis, we have investigated the space of the symmergent parameters cO and ˆ α wherein they produce results that comply with the inflationary observables ns, r, and dns/dlnk. Wehaveshownthatthevacuumenergytogetherwiththequadraticcurvaturetermarising in the symmergent gravity prescription are capable of inflating the universe provided that the quadratic curvature coefficient cO is negative (which corresponds to fermion dominance in number in the matter sector) and the deviation from the mass degeneracy in the matter sector is minute for both boson mass dominance and fermion mass dominance cases.
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    Large Field Polynomial Inflation in R2 Gravity with non-minimal coupling: Palatini formalism
    (Türkiye Enerji, Nükleer ve Maden Araştırma Kurumu (TENMAK), 2024-10-11) Bostan,Nilay; Karahan, Canan; Sargın, Ozan
    In this paper, we employ the Palatini formalism to investigate the dynamics of large field inflation using a renormalizable polynomial inflaton potential in the context of quadratic gravity. Assuming instant reheating, we make a comparative analysis of Large Field Polynomial Inflation (LFPI). We first consider inflaton (i) minimally and (ii) nonminimally coupled to R gravity, and then we continue with inflaton (iii) minimally and (iv) non-minimally coupled to R + R2 gravity. We scan the parameter space for the inflationary predictions (ns and r) consistent with the Planck and BICEP/Keck 2018 results as well as the sensitivity forecast of the future CMB-S4 and depict the compliant regions in the ϕ0 −β plane where ϕ0 and β are two parameters of polynomial inflation model which control the saddle point of the potential and the flatness in that region respectively. Furthermore, for the polynomial potential, we display the behavior of the running of the spectral index αs ≡ dns/d ln k with respect to the spectral index ns itself for all the cases.
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    Reheating constraints to Palatini Coleman-Weinberg inflation
    (Tübitak, 2024-02-21) Bostan, Nilay
    In this work, we examine the reheating constraints to symmetry-breaking mechanism, which is associated with Coleman-Weinberg inflation in the early universe. We consider the Coleman-Weinberg inflation potential,wheretheinflatonhasa v ̸= 0 afterinflation. Setting Treh = 105 GeV,wefirstshow wreh dependency on ns, r, and N∗ for AV case. Then, we demonstrate the results of ns, r, N∗, α = dns/dlnk for different reheating temperatures and compare the results with the latest BICEP/Keck data. We also present that ns−r and ns−N∗ planes and the effect of reheating temperature which is in a wide range, on inflationary predictions for both AV and BV cases. Finally, we indicate how N∗ and α change according to the reheating temperature values.