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Articoli di riviste sul tema "Cosmological analysis"

Autore: Grafiati

Pubblicato: 14 dicembre 2024

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1

Brout, Dillon, Dan Scolnic, Brodie Popovic, Adam G. Riess, Anthony Carr, Joe Zuntz, Rick Kessler et al. "The Pantheon+ Analysis: Cosmological Constraints". Astrophysical Journal 938, n. 2 (1 ottobre 2022): 110. http://dx.doi.org/10.3847/1538-4357/ac8e04.

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Abstract We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω M = 0.334 ± 0.018 from SNe Ia alone. For a flat w 0CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s−1 Mpc−1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 0.978 − 0.031 + 0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 73.3 ± 1.1 km s−1 Mpc−1 when including SH0ES Cepheid distances, and w a = − 0.65 − 0.32 + 0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.

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2

Nagasawa, Michiyasu. "Numerical Analysis of Cosmological Defects". Progress of Theoretical Physics Supplement 138 (2000): 644–45. http://dx.doi.org/10.1143/ptps.138.644.

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3

NOUTCHEGUEME, NORBERT, e ALEXIS NANGUE. "GLOBAL EXISTENCE TO THE EINSTEIN-SCALAR FIELD SYSTEM ON THE ROBERTSON–WALKER SPACE-TIMES WITH HYPERBOLIC AND SPHERICAL SYMMETRIES". Journal of Hyperbolic Differential Equations 07, n. 01 (marzo 2010): 69–83. http://dx.doi.org/10.1142/s0219891610002074.

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4

ELLIS, GEORGE F. R. "DYNAMICAL PROPERTIES OF COSMOLOGICAL SOLUTIONS". Journal of Hyperbolic Differential Equations 02, n. 02 (giugno 2005): 381–95. http://dx.doi.org/10.1142/s0219891605000464.

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I will consider how there are FOSH formulations and associated results in relativistic cosmology expressed in 1+3 tetrad form. The characteristics of scalar and vector perturbations are timelike, hence the real domains of dependence in cosmology are much smaller than implied by the light cone, associated with gravitational wave perturbations.

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ALLEN, PAUL T., e ALAN D. RENDALL. "ASYMPTOTICS OF LINEARIZED COSMOLOGICAL PERTURBATIONS". Journal of Hyperbolic Differential Equations 07, n. 02 (giugno 2010): 255–77. http://dx.doi.org/10.1142/s0219891610002141.

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In cosmology an important role is played by homogeneous and isotropic solutions of the Einstein–Euler equations and linearized perturbations of these. This paper proves results on the asymptotic behavior of scalar perturbations both in the approach to the initial singularity of the background model and at late times. The main equation of interest is a linear hyperbolic equation whose coefficients depend only on time. Expansions for the solutions are obtained in both asymptotic regimes. In both cases, it is shown how general solutions with a linear equation of state can be parametrized by certain functions which are coefficients in the asymptotic expansion. For some nonlinear equations of state, it is found that the late-time asymptotic behavior is qualitatively different from that in the linear case.

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6

Tiwari, L. K. "MATHEMATICAL ANALYSIS OF COSMOLOGICAL MODELS WITH LINEARLY VARYING DECELERATION PARAMETER". South East Asian J. of Mathematics and Mathematical Sciences 19, n. 03 (30 dicembre 2023): 449–58. http://dx.doi.org/10.56827/seajmms.2023.1903.34.

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Bianchi type-V is investigated using a decaying cosmological constant with perfect fluid. The study solves Einstein field equations by assuming that the deceleration parameter q is functionally connected to the Hubble parameter H, which yields the scale factor a. As cosmic time t increases, the cosmological model experiences exponential inflation. The physical characteristics and behavior of the cosmological model are also covered.

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7

Ove, R. "Analysis of cosmological gravitational wave residue". Classical and Quantum Gravity 7, n. 12 (1 dicembre 1990): 2225–36. http://dx.doi.org/10.1088/0264-9381/7/12/007.

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8

Akbar, M., Tayeb Brahimi e S. M. Qaisar. "Thermodynamic Analysis of Cosmological Black Hole". Communications in Theoretical Physics 67, n. 1 (gennaio 2017): 47. http://dx.doi.org/10.1088/0253-6102/67/1/47.

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9

Méndez, Vicenç, e Josep Triginer. "Qualitative analysis of causal cosmological models". Journal of Mathematical Physics 37, n. 6 (giugno 1996): 2906–19. http://dx.doi.org/10.1063/1.531546.

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10

Abramo, L. Raul, Lucas F. Secco e Arthur Loureiro. "Fourier analysis of multitracer cosmological surveys". Monthly Notices of the Royal Astronomical Society 455, n. 4 (3 dicembre 2015): 3871–89. http://dx.doi.org/10.1093/mnras/stv2588.

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11

Cui, Yanou, Soubhik Kumar, Raman Sundrum e Yuhsin Tsai. "Unraveling cosmological anisotropies within stochastic gravitational wave backgrounds". Journal of Cosmology and Astroparticle Physics 2023, n. 10 (1 ottobre 2023): 064. http://dx.doi.org/10.1088/1475-7516/2023/10/064.

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Abstract Identifying the anisotropies in a cosmologically sourced stochastic gravitational wave background (SGWB) would be of significance in shedding light on the nature of primordial inhomogeneities. For example, if SGWB carries isocurvature fluctuations, it would provide evidence for a multi-field inflationary origin of these inhomogeneities. However, this is challenging in practice due to finite detector sensitivity and also the presence of the astrophysical foregrounds that can compete with the cosmological signal. In this work, we explore the prospects for measuring cosmological SGWB anisotropies in the presence of an astrophysical counterpart and detector noise. To illustrate the main idea, we perform a Fisher analysis using a well-motivated cosmological SGWB template corresponding to a first order phase transition, and an astrophysical SGWB template corresponding to extra-galactic binary mergers, and compute the uncertainty with which various parameters characterizing the isotropic and anisotropic components can be extracted. We also discuss some subtleties and caveats involving shot noise in the astrophysical foreground. Overall, we show that upcoming experiments, e.g., LISA, Taiji, Einstein Telescope, Cosmic Explorer, and BBO, can all be effective in discovering plausible anisotropic cosmological SGWBs.

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12

ELLIS, GEORGE F. R. "THE SPACE OF COSMOLOGICAL SPACE–TIMES". Journal of Hyperbolic Differential Equations 02, n. 02 (giugno 2005): 331–79. http://dx.doi.org/10.1142/s0219891605000476.

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I first focus on how to best describe the space of cosmological space–times and what its essential properties are and some comments on the dynamical behavior revealed by studies that will be described in more detail by John Wainwright. I will then relate this both to observations and to anthropic issues (i.e. the possible existence of observers). This space includes some viable singularity free solutions which will be briefly described, thus posing the issue of the tension between very special initial conditions and the existence of initial singularities. I will conclude with remarks on the issue of realized infinities in this context and the concept of multiverses.

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13

Espriu, Domènec, e Marc Rodoreda. "Effect of the cosmological parameters on gravitational waves: general analysis". Classical and Quantum Gravity 39, n. 1 (7 dicembre 2021): 015012. http://dx.doi.org/10.1088/1361-6382/ac33bc.

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Abstract Some time ago it was pointed out that the presence of cosmological components could affect the propagation of gravitational waves (GW) beyond the usual cosmological redshift and that such effects might be observable in pulsar timing arrays (PTA). These analyses were done at leading order in the Hubble constant H 0, which is proportional to Λ 1 2 and ρ i 1 2 (ρ i being the various cosmological fluid densities). In this work, we study in detail the propagation of metric perturbations on a Schwarzschild–de Sitter (SdS) background, close to the place where GW are produced, and obtain solutions that incorporate corrections linear in ρ i and Λ. At the next-to-leading order the corrections do not appear in the form of H 0 thus lifting the degeneracy among the various cosmological components. We also determine the leading corrections proportional to the mass of the final object; they are very small for the distances considered in PTA but may be of relevance in other cases. When transformed into comoving coordinates, the ones used in cosmological measurements, this SdS solution does satisfy the perturbation equations in a Friedmann–Lemaître–Robertson–Walker metric up to and including Λ 3 2 terms. This analysis is then extended to the other cosmological fluids, allowing us to consider GW sources in the Gpc range. Finally, we investigate the influence of these corrections in PTA observations.

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14

Ignat’ev, Yu G. "Similarity of cosmological models and its application to the analysis of cosmological evolution". Theoretical and Mathematical Physics 219, n. 1 (aprile 2024): 688–703. http://dx.doi.org/10.1134/s0040577924040123.

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15

Ignatev, Yuriy Gennadievich. "Similarity of cosmological models and its application to the analysis of cosmological evolution". Teoreticheskaya i Matematicheskaya Fizika 219, n. 1 (28 marzo 2024): 181–98. http://dx.doi.org/10.4213/tmf10583.

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Исследованы масштабные преобразования космологических моделей, основанных на статистической системе вырожденных фермионов со скалярным взаимодействием Хиггса. Выявлены свойства подобия космологических моделей при масштабном преобразовании их фундаментальных параметров. Установлены законы преобразования координат особых точек и собственных чисел характеристической матрицы динамической системы космологической модели при ее масштабных преобразованиях. С помощью преобразования к новым переменным исследуемая ранее динамическая система скалярно заряженных фермионов модифицирована к динамической системе с невырожденной характеристической матрицей и для невырожденной ее ветви найдены особые точки и собственные числа характеристической матрицы, совпадающие с соответствующими значениями для вакуумно-полевой модели. Приведены примеры численного моделирования подобных космологических моделей.

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16

Salvati, L. "Planck and SPT cluster catalogs: A combined analysis". EPJ Web of Conferences 293 (2024): 00045. http://dx.doi.org/10.1051/epjconf/202429300045.

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We show the results for the first combined analysis of clusters detected by the Planck satellite and the South Pole Telescope. The combination of these two experiments, with different resolution, mass and redshift range, allows to track the full cosmological evolution of galaxy clusters and the interplay between astrophysics and cosmology. In particular, we exploit the cosmological constraining power of SPT-SZ clusters to provide an independent calibration of Planck scaling relations, and therefore a new estimation of Planck cluster masses. Combining the two cluster catalogs we are thus able to test the hypotheses of self-similarity and hydrostatic equilibrium. We show therefore the huge potentiality of combining catalogs from different experiments, in improving the cosmological analysis and the treatment of different astrophysical and systematic uncertainties.

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17

Khan, Zoya, Shamaila Rani, Abdul Jawad e G. Mustafa. "Analysis of cubic gravity through cosmic aspects". International Journal of Geometric Methods in Modern Physics 17, n. 09 (7 luglio 2020): 2050134. http://dx.doi.org/10.1142/s0219887820501340.

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In the context of cubic gravity for flat FRW metric we discuss the behavior of cosmological parameters (equation of state (EoS) parameter and square speed of sound) at Hubble horizon with the four different models of Hubble parameter. We observe the validity of generalized second law of thermodynamics (GSLT) and thermal equilibrium condition. It is found that cosmological parameters lie within the observational constraints. Also, GSLT and thermal equilibrium condition holds in almost all cases of Hubble parameter.

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18

Kuzmichev, V. E., e V. V. Kuzmichev. "Comparative Analysis of Standard ΛCDM and ΛCS Models". Ukrainian Journal of Physics 57, n. 10 (3 dicembre 2021): 1169. http://dx.doi.org/10.15407/ujpe57.11.1169.

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We draw a comparison of time-dependent cosmological parameters calculated in the standard ΛCDM model with those of the model of a homogeneous and isotropic Universe with non-zero cosmological constant filled with a perfect gas of low-velocity cosmic strings (ΛCS model). It is shown that pressure-free matter can obtain the properties of a gas of low-velocity cosmic strings in the epoch, when the global geometry and the total amount of matter in the Universe as a whole obey an additional constraint. This constraint follows from the quantum geometrodynamical approach in the semiclassical approximation. In terms of general relativity, its effective contribution to the field equations can be linked to the time evolution of the equation of state of matter caused by the processes of redistribution of the energy between matter components. In the present article, the exact solutions of the Einstein equations for the ΛCS model are found. It is demonstrated that this model is equivalent to the open de Sitter model. After the scale transformation of the time variable of the ΛCS model, the standard ΛCDM and ΛCS models provide the equivalent descriptions of cosmological parameters as functions of time at equal values of the cosmological constant. The exception is the behavior of the deceleration parameter in the early Universe.

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19

Muir, J., G. M. Bernstein, D. Huterer, F. Elsner, E. Krause, A. Roodman, S. Allam et al. "Blinding multiprobe cosmological experiments". Monthly Notices of the Royal Astronomical Society 494, n. 3 (15 aprile 2020): 4454–70. http://dx.doi.org/10.1093/mnras/staa965.

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ABSTRACT The goal of blinding is to hide an experiment’s critical results – here the inferred cosmological parameters – until all decisions affecting its analysis have been finalized. This is especially important in the current era of precision cosmology, when the results of any new experiment are closely scrutinized for consistency or tension with previous results. In analyses that combine multiple observational probes, like the combination of galaxy clustering and weak lensing in the Dark Energy Survey (DES), it is challenging to blind the results while retaining the ability to check for (in)consistency between different parts of the data. We propose a simple new blinding transformation, which works by modifying the summary statistics that are input to parameter estimation, such as two-point correlation functions. The transformation shifts the measured statistics to new values that are consistent with (blindly) shifted cosmological parameters while preserving internal (in)consistency. We apply the blinding transformation to simulated data for the projected DES Year 3 galaxy clustering and weak lensing analysis, demonstrating that practical blinding is achieved without significant perturbation of internal-consistency checks, as measured here by degradation of the χ2 between the data and best-fitting model. Our blinding method’s performance is expected to improve as experiments evolve to higher precision and accuracy.

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20

Costa, João L., José Natário e Pedro F. C. Oliveira. "Decay of solutions of the wave equation in expanding cosmological spacetimes". Journal of Hyperbolic Differential Equations 16, n. 01 (marzo 2019): 35–58. http://dx.doi.org/10.1142/s0219891619500024.

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We study the decay of solutions of the wave equation in some expanding cosmological spacetimes, namely flat Friedmann–Lemaître–Robertson–Walker (FLRW) models and the cosmological region of the Reissner–Nordström–de Sitter (RNdS) solution. By introducing a partial energy and using an iteration scheme, we find that, for initial data with finite higher order energies, the decay rate of the time derivative is faster than previously existing estimates. For models undergoing accelerated expansion, our decay rate appears to be (almost) sharp.

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21

WAINWRIGHT, J., e W. C. LIM. "COSMOLOGICAL MODELS FROM A DYNAMICAL SYSTEMS PERSPECTIVE". Journal of Hyperbolic Differential Equations 02, n. 02 (giugno 2005): 437–69. http://dx.doi.org/10.1142/s0219891605000531.

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It is useful to study the space of all cosmological models from a dynamical systems perspective, that is, by formulating the Einstein field equations as a dynamical system using appropriately normalized variables. We will discuss various aspects of this work, the choices of normalization factor, multiple representations of models, the past attractor, nonlinear dynamics in close-to-Friedmann–Lemaître models, Weyl curvature dominance, and numerical simulations.

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22

CHIN, C. H., e C. L. CHUNG. "ANALYSIS AND PROBABILITY LAWS". Modern Physics Letters A 17, n. 28 (14 settembre 2002): 1825–34. http://dx.doi.org/10.1142/s021773230200837x.

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23

Qi, Ziyao. "Analysis of the Hubble Tension and Modifications to the Standard Cosmological Model". Highlights in Science, Engineering and Technology 104 (11 giugno 2024): 60–71. http://dx.doi.org/10.54097/vsj05b75.

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The Hubble constant is crucial to the knowledge of the universe’s nature and expansion, remaining as an active area for research in the recent decades. Cosmological microwave background observations revealed a lower value of 67–69 km-1s-1Mpc for the Hubble constant, but local data showed a higher value of 73–75 km-1s-1Mpc. This study focuses on the Hubble constant and its measurement, systematic uncertainties, observed tension, and potential modifications to the standard cosmological model. To be specific, this paper aims to address the tension between different measurement methods, which are Cepheid variables and supernovae, Baryon Acoustic Oscillations, and Gravitational waves, and understand systematic uncertainties. Results show discrepancies in Hubble constant values, indicating potential modifications to the standard cosmological model. Prospects include exploring alternative cosmological components and enhanced detection and computation methods. The study's implications lie in advancing the understanding of the expanding universe and guiding future research directions regarding to Hubble tension measurement.

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24

Winter, Dale. "Analysis of the cosmological Oppenheimer-Volkoff equations". Journal of Mathematical Physics 41, n. 8 (agosto 2000): 5582–97. http://dx.doi.org/10.1063/1.533427.

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25

Hwang, Jai-chan. "Cosmological quasilinear analysis including the rotation mode". Physical Review D 48, n. 8 (15 ottobre 1993): 3557–61. http://dx.doi.org/10.1103/physrevd.48.3557.

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26

Melia, F., J. J. Wei, R. S. Maier e X. F. Wu. "Cosmological tests with the joint lightcurve analysis". EPL (Europhysics Letters) 123, n. 5 (5 ottobre 2018): 59002. http://dx.doi.org/10.1209/0295-5075/123/59002.

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27

LI, Hong. "Determining cosmological parameters with global fitting analysis". SCIENTIA SINICA Physica, Mechanica & Astronomica 41, n. 12 (1 novembre 2011): 1385–88. http://dx.doi.org/10.1360/132011-978.

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Gironés, Z., A. Marchetti, O. Mena, C. Peña-Garay e N. Rius. "Cosmological data analysis off(R) gravity models". Journal of Cosmology and Astroparticle Physics 2010, n. 11 (4 novembre 2010): 004. http://dx.doi.org/10.1088/1475-7516/2010/11/004.

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Jawad, Abdul, e Shamaila Rani. "Cosmological Analysis of Dynamical Chern-Simons Modified Gravity via Dark Energy Scenario". Advances in High Energy Physics 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/259578.

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The purpose of this paper is to study the cosmological evolution of the universe in the framework of dynamical Chern-Simons modified gravity. We take pilgrim dark energy model with Hubble and event horizons in interacting scenario with cold dark matter. For this scenario, we discuss cosmological parameters such as Hubble and equation of state and cosmological plane likeωϑ-ωϑ′and squared speed of sound. It is found that Hubble parameter approaches the ranges75-0.5+0.5(foru=2) and (74, 74.30) (foru=1,-1,-2) for Hubble horizon pilgrim dark energy. It implies the ranges74.80-0.005+0.005(foru=2) and (73.4, 74) (foru=-2) for event horizon pilgrim dark energy. The equation of state parameter provides consistent ranges with different observational schemes. Also,ωϑ-ωϑ′planes lie in the range (ωϑ=-1.13-0.25+0.24,ωϑ′<1.32). The squared speed of sound shows stability for all present models in the present scenario. We would like to mention here that our results of various cosmological parameters show consistency with different observational data like Planck, WP, BAO,H0, SNLS, and WMAP.

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Sharif, M., e M. Zubair. "Analysis off(R)Theory Corresponding to NADE and NHDE". Advances in High Energy Physics 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/790967.

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We develop the connection off(R)theory with new agegraphic and holographic dark energy models. The functionf(R)is reconstructed regarding thef(R)theory as an effective description for these dark energy models. We show the future evolution offand conclude that these functions represent distinct pictures of cosmological eras. The cosmological parameters such as equation of state parameter, deceleration parameter, statefinder diagnostic, andw−w′analysis are investigated which assure the evolutionary paradigm off.

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CIANFRANI, FRANCESCO, e GIOVANNI MONTANI. "A CRITICAL ANALYSIS OF THE COSMOLOGICAL IMPLEMENTATION OF LOOP QUANTUM GRAVITY". Modern Physics Letters A 27, n. 07 (7 marzo 2012): 1250032. http://dx.doi.org/10.1142/s0217732312500320.

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This papers offers a critical discussion on the procedure by which Loop Quantum Cosmology (LQC) is constructed from the full Loop Quantum Gravity (LQG) theory. Revising recent issues in preserving SU(2) symmetry when quantizing the isotropic Universe, we trace a new perspective in approaching the cosmological problem within quantum geometry. The cosmological sector of LQG is reviewed and a critical point of view on LQC is presented. It is outlined how a polymer-like scale for quantum cosmology can be predicted from a proper fundamental graph underlying the homogeneous and isotropic continuous picture. However, such a minimum scale does not coincide with the choice made in LQC. Finally, the perspectives towards a consistent cosmological LQG model based on such a graph structure are discussed.

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Tiwari, Ram Bharosha Ahmad, e Sudhir Kumar Srivastava. "CERTAIN COSMOLOGICAL MODELS WITH VARIATION OF HUBBLE PARAMETER". South East Asian J. of Mathematics and Mathematical Sciences 19, n. 01 (30 aprile 2023): 323–34. http://dx.doi.org/10.56827/seajmms.2023.1901.26.

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The present paper deals with the FRW-Cosmological Model of universe for W2 flat perfect fluid space time. Einstein field equations with variable cosmological constant (Λ) has been obtained for such spacetime and in order to get the complete cosmological solution the law of variation for Hubble’s parameter is considered. A new class of solution have been discussed for the Einstein field equations with variable cosmological constant in which the pressure, energy density, and cosmological constant Λ are found to be decreasing function of cosmic time. The physical and kinematical properties of models are also discussed.

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Cao, Shulei, e Bharat Ratra. "Testing the standardizability of, and deriving cosmological constraints from, a new Amati-correlated gamma-ray burst data compilation". Journal of Cosmology and Astroparticle Physics 2024, n. 10 (1 ottobre 2024): 093. http://dx.doi.org/10.1088/1475-7516/2024/10/093.

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Abstract By using gamma-ray burst (GRB) data to simultaneously constrain Amati correlation parameters and cosmological parameters in six spatially flat and nonflat dark energy cosmological models, we show that an updated 220 GRB version of the Jia et al. [1] GRB data compilation are standardizable through the Amati correlation and so can be used for cosmological analyses. However, the resulting GRB data constraints on the current value of the nonrelativistic matter density parameter, Ω m 0, are in > 2σ tension with those from a joint analysis of better-established Hubble parameter [H(z)] and baryon acoustic oscillation (BAO) data for most of the cosmological models we consider, indicating that these GRB data cannot be jointly used with better-established H(z) + BAO data to constrain cosmological parameters.

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GARKUN, A. S., V. I. KUDIN e A. V. MINKEVICH. "ANALYSIS OF REGULAR INFLATIONARY COSMOLOGICAL MODELS WITH TWO TORSION FUNCTIONS IN POINCARÉ GAUGE THEORY OF GRAVITY". International Journal of Modern Physics A 25, n. 10 (20 aprile 2010): 2005–22. http://dx.doi.org/10.1142/s0217751x10048433.

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Regular inflationary Big Bang scenario with accelerating stage of cosmological expansion at asymptotics proposed earlier in the framework of the Poincaré gauge theory of gravity is investigated. Analysis of regular inflationary cosmological models with two torsion functions filled with scalar field with quadratic potential and ultrarelativistic matter is carried out numerically. Properties of different stages of regular inflationary cosmological solutions are studied, restrictions on admissible values of parameters and initial conditions at a bounce are found. The structure of extremum surface in space of physical variables is investigated.

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Khadka, Narayan, Zhefu Yu, Michal Zajaček, Mary Loli Martinez-Aldama, Bożena Czerny e Bharat Ratra. "Standardizing reverberation-measured Mg II time-lag quasars, by using the radius–luminosity relation, and constraining cosmological model parameters". Monthly Notices of the Royal Astronomical Society 508, n. 4 (2 ottobre 2021): 4722–37. http://dx.doi.org/10.1093/mnras/stab2807.

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ABSTRACT We use 78 reverberation-measured Mg II time-lag quasars (QSOs) in the redshift range 0.0033 ≤ z ≤ 1.89 to constrain cosmological parameters in six different cosmological models. The basis of our method is the use of the radius–luminosity or R−L relation to standardize these 78 Mg II QSOs. In each cosmological model, we simultaneously determine R−L relation and cosmological model parameters, thus avoiding the circularity problem. We find that the R−L relation parameter values are independent of the cosmological model used in the analysis, thus, establishing that current Mg II QSOs are standardizable candles. Cosmological constraints obtained using these QSOs are significantly weaker than, but consistent with, those obtained from a joint analysis of baryon acoustic oscillation (BAO) observations and Hubble parameter [H(z)] measurements. So, we also analyse these QSOs in conjunction with the BAO + H(z) data and find cosmological constraints consistent with the standard spatially flat ΛCDM model as well as with mild dark energy dynamics and a little spatial curvature. A larger sample of higher quality reverberation-measured QSOs should have a smaller intrinsic dispersion and so should provide tighter constraints on cosmological parameters.

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36

Douspis, Marian, Laura Salvati, Adélie Gorce e Nabila Aghanim. "Retrieving cosmological information from small-scale CMB foregrounds". Astronomy & Astrophysics 659 (marzo 2022): A99. http://dx.doi.org/10.1051/0004-6361/202142004.

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We propose a new analysis of small-scale cosmic microwave background (CMB) data by introducing the cosmological dependency of the foreground signals, focussing first on the thermal Sunyaev-Zel’dovich (tSZ) power spectrum, derived from the halo model. We analyse the latest observations by the South Pole Telescope (SPT) of the high-ℓ power (cross) spectra at 95, 150, and 220 GHz, as the sum of CMB and tSZ signals, both depending on cosmological parameters and remaining contaminants. In order to perform faster analyses, we propose a new tSZ modelling based on machine learning algorithms (namely Random Forest). We show that the additional information contained in the tSZ power spectrum tightens constraints on cosmological and tSZ scaling relation parameters. We combined for the first time the Planck tSZ data with SPT high-ℓ to derive new constraints. Finally, we show how the amplitude of the remaining kinetic SZ power spectrum varies depending on the assumptions made on both tSZ and cosmological parameters. These results show the importance of a thorough modelling of foregrounds in the cosmological analysis of small-scale CMB data. Reliable constraints on cosmological parameters can only be achieved once other significant foregrounds, such as the kinetic SZ and the cosmic infrared background (CIB), are also properly accounted for.

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37

Cao, Shulei, Joseph Ryan, Narayan Khadka e Bharat Ratra. "Cosmological constraints from higher redshift gamma-ray burst, H ii starburst galaxy, and quasar (and other) data". Monthly Notices of the Royal Astronomical Society 501, n. 1 (3 dicembre 2020): 1520–38. http://dx.doi.org/10.1093/mnras/staa3748.

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ABSTRACT We use higher redshift gamma-ray burst (GRB), H ii starburst galaxy (H iiG), and quasar angular size (QSO-AS) measurements to constrain six spatially flat and non-flat cosmological models. These three sets of cosmological constraints are mutually consistent. Cosmological constraints from a joint analysis of these data sets are largely consistent with currently accelerating cosmological expansion and with cosmological constraints derived from a combined analysis of Hubble parameter (H(z)) and baryon acoustic oscillation (BAO, with Planck-determined baryonic matter density) measurements. A joint analysis of the H(z) + BAO + QSO-AS + H iiG + GRB data provides fairly model-independent determinations of the non-relativistic matter density parameter $\Omega _{\rm m_0}=0.313\pm 0.013$ and the Hubble constant $H_0=69.3\pm 1.2\, \rm {km \, s^{-1} \, Mpc^{-1}}$. These data are consistent with the dark energy being a cosmological constant and with spatial hypersurfaces being flat, but they do not rule out mild dark energy dynamics or a little spatial curvature. We also investigate the effect of including quasar flux measurements in the mix and find no novel conclusions.

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38

Douspis, Marian, Laura Salvati, Adélie Gorce e Nabila Aghanim. "CMB at small scales: Cosmology from tSZ power spectrum". EPJ Web of Conferences 257 (2022): 00014. http://dx.doi.org/10.1051/epjconf/202225700014.

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Small scale CMB angular power spectrum contains not only primordial CMB information but also many contaminants coming from secondary anisotropies. Most of the latter depend on the cosmological model but are often marginalised over. We propose a new analysis of the SPT data focusing on the cosmological contribution of the thermal Sunyaev Zel’dovich (tSZ) effect. We model the tSZ angular spectrum with the halo model and train a random forest algorithm to speed up its computation. We show that using the cosmological information of the tSZ on top of the primordial CMB one contained in SPT data bring more constraints on cosmological parameters. We also combine for the first time Planck tSZ angular power spectrum with SPT ones to put further constraints. This proof of concept study shows how much a proper modelling of the foregrounds in the cosmological analyses is needed.

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39

Pan, Jiaming, Dragan Huterer, Felipe Andrade-Oliveira e Camille Avestruz. "Compressed baryon acoustic oscillation analysis is robust to modified-gravity models". Journal of Cosmology and Astroparticle Physics 2024, n. 06 (1 giugno 2024): 051. http://dx.doi.org/10.1088/1475-7516/2024/06/051.

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Abstract We study the robustness of the baryon acoustic oscillation (BAO) analysis to the underlying cosmological model. We focus on testing the standard BAO analysis that relies on the use of a template. These templates are constructed assuming a fixed fiducial cosmological model and used to extract the location of the acoustic peaks. Such “compressed analysis” had been shown to be unbiased when applied to the ΛCDM model and some of its extensions. However, it has not been known whether this type of analysis introduces biases in a wider range of cosmological models where the template may not fully capture relevant features in the BAO signal. In this study, we apply the compressed analysis to noiseless mock power spectra that are based on Horndeski models, a broad class of modified-gravity theories specified with eight additional free parameters. We study the precision and accuracy of the BAO peak-location extraction assuming DESI, DESI II, and MegaMapper survey specifications. We find that the bias in the extracted peak locations is negligible; for example, it is less than 10% of the statistical error for even the proposed future MegaMapper survey. Our findings indicate that the compressed BAO analysis is remarkably robust to the underlying cosmological model.

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40

Levin, S. F. "Cosmological distances scale. Pt. 12. Confluence analysis, rang inversion and tests for inadequacy". Izmeritel`naya Tekhnika, n. 12 (2020): 13–21. http://dx.doi.org/10.32446/0368-1025it.2020-12-13-21.

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The measurement problem of calibration of the cosmological distance scale is considered from the point of view of the conditions of applicability of the regression analysis. It is shown that the rank inversion and statistical heterogeneity of data on supernovae SN Ia, which were used in 1998–1999 to detect the “acceleration of the expansion of the Universe”, and in 2004–2007 – as “extraordinary evidence” of its existence, is the reason for the discrepancy and inconsistency of the obtained estimates of the parameters of the Friedman-Robertson-Walker model. Although the use of tests for inadequacy for models of the cosmological distance scale reduces these negative effects, the fact remains that the cosmological distance scale based on redshift has neither the status of metric nor ordinal.

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41

Bhatia, Arshdeep Singh, e Sourav Sur. "Dynamical system analysis of dark energy models in scalar coupled Metric-Torsion theories". International Journal of Modern Physics D 26, n. 13 (22 ottobre 2017): 1750149. http://dx.doi.org/10.1142/s0218271817501498.

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We study the phase-space dynamics of cosmological models in the theoretical formulations of nonminimal metric-torsion couplings with a scalar field, and investigate in particular the critical points (CPs) which yield stable solutions exhibiting cosmic acceleration driven by the dark energy (DE). The latter is so defined that it effectively has no direct interaction with the cosmological fluid, although in an equivalent scalar–tensor cosmological setup, the scalar field interacts with the fluid (which we consider to be the pressureless dust). Determining the conditions for the existence of the stable CPs, we check their physical viability in both Einstein and Jordan frames. We also verify that in either of these frames, the evolution of the universe at the corresponding stable points matches with that given by the respective exact solutions we have found in an earlier work [S. Sur and A. S. Bhatia, arXiv:1611.00654 [gr-qc]]. We not only examine the regions of physical relevance in the phase-space when the coupling parameter is varied, but also demonstrate the evolution profiles of the cosmological parameters of interest along fiducial trajectories in the effectively noninteracting scenarios, in both Einstein and Jordan frames.

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42

Huang, Hai, Qihong Huang e Ruanjing Zhang. "Phase Space Analysis of Barrow Agegraphic Dark Energy". Universe 8, n. 9 (7 settembre 2022): 467. http://dx.doi.org/10.3390/universe8090467.

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Using the Barrow entropy and considering the timescale as IR cutoff, a new holographic dark energy model named Barrow agegraphic dark energy (BADE) was proposed. We use phase space analysis method to discuss the evolution of the universe in three different mode of BADE (Q=0; Q=3αH(ρm+ρD); Q=H(αρm+βρD)). We find the attractor which represents the dark energy-dominated era exists in all cases. In the case Q=0 and Q=H(αρm+βρD) with β=0, the attractor can behave as the cosmological constant, and these models can used to mimic the cosmological constant.

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43

Liu, Yuchen, e Yi Ren. "Analysis of the Principle and Simulations for Galaxy Formation". Highlights in Science, Engineering and Technology 88 (29 marzo 2024): 620–26. http://dx.doi.org/10.54097/yj4gba81.

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As a matter of fact, the limit to technological advancements seems endless. With the recent launch of the James Webb Space Telescope, cosmological observation has become clearer than ever, allowing us to look deeper into the past. To aid these investigations, simulations have been designed as a way to test the theories and predictions. Despite the fact that simulations have become remarkably precise and accuracy, certain limitations must not be overlooked. We explain the key principles of galaxy formation including dark matter, host halos, and subhalos in this paper. Additionally, the main ideas and models of galaxy evolution including star formation and feedback, along with a deeper analysis into cosmological models especially the IllustrisTNG project. It will help get a better grasp and understanding of potential limitations mainly consisting of large physical calculations. Solutions can be derived from such problems especially with the recent explosion of AI and machine learning related works. By understanding the physical processes, a multilayered perspective can probe and build on the existing methods of cosmological simulations, facilitating for even more detailed and precise data.

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44

Douspis, Marian, Adélie Gorce e Laura Salvati. "Small-scale CMB cosmological information". EPJ Web of Conferences 293 (2024): 00015. http://dx.doi.org/10.1051/epjconf/202429300015.

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The small-scale CMB angular power spectrum contains many contaminants from secondary anisotropies created by large-scale structures. Although their contribution is taken into account in the analyses, their cosmological dependence is often ignored. We propose a new analysis of SPT data focusing on the cosmological contributions of the Sunyaev Zel’dovich effects (tSZ and kSZ). After modelling these two effects and building a power spectrum emulator, we show that using the cosmological information of the tSZ and kSZ in addition to that of the primordial CMB contained in the small-scale SPT data provides comparable constraints on the reionisation history to those of the large-scale data of Planck.

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45

Mohanty, Sujata, e Rajesh Gopal. "Analysis of cosmological bias within spherical collapse model". EUREKA: Physics and Engineering, n. 5 (30 settembre 2022): 3–11. http://dx.doi.org/10.21303/2461-4262.2022.002429.

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The goal of our research work is to analyze cosmological bias parameter. Parametric equations of spherical collapse model are used to calculate the values of spherical collapse over density and mass variance, which is further used in bias formulae to find the values of cosmological bias. Spherical collapse over density has been calculated in the range of redshift 0 to 1. Also, it is compared with the value according to the spherical collapse model. Bias is one of the parameters which are utilized to infer cosmological parameters. Extracting the cosmological parameters is very much useful to know and understand about the birth and evolution of our universe. As there is no direct probe to get the idea about the existence of dark matter. Bias factor helps to analyze about dark matter. The bias coefficient of higher order terms in Taylor series expansion are found to be in ascending order. Increasing values of bias indicate the large-scale structure formation at current epoch is more and more clustered. Values of bias are discussed in result. Also, bias values have been analyzed for redshift in the range 2 to 0. The graph has been plotted bias versus redshift. Let’s found bias decreases with decrease of redshift. That means bias evolves with redshift. Bias value less than one and negative value of bias implies that structure formation is in linear region and higher values of bias indicates the structure formation occurs in nonlinear region. Negative value of bias is also called as antibias. That means the structure formation has not started yet. It is still in linear region. The bias value nearly equal to one indicates that the structure formation has been transformed from linear region to nonlinear region. So, the result showing bias values greater than one indicates that evolution of structure formation occurs in nonlinear region.

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46

Costanzi, M., E. Rozo, M. Simet, Y. Zhang, A. E. Evrard, A. Mantz, E. S. Rykoff et al. "Methods for cluster cosmology and application to the SDSS in preparation for DES Year 1 release". Monthly Notices of the Royal Astronomical Society 488, n. 4 (17 luglio 2019): 4779–800. http://dx.doi.org/10.1093/mnras/stz1949.

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ABSTRACT We implement the first blind analysis of cluster abundance data to derive cosmological constraints from the abundance and weak lensing signal of redMaPPer clusters in the Sloan Digital Sky Survey (SDSS). We simultaneously fit for cosmological parameters and the richness–mass relation of the clusters. For a flat Λ cold dark matter cosmological model with massive neutrinos, we find $S_8 \equiv \sigma _{8}(\Omega _\mathrm{ m}/0.3)^{0.5}=0.79^{+0.05}_{-0.04}$. This value is both consistent and competitive with that derived from cluster catalogues selected in different wavelengths. Our result is also consistent with the combined probes analyses by the Dark Energy Survey (DES), the Kilo-Degree Survey (KiDS), and with the cosmic microwave background (CMB) anisotropies as measured by Planck. We demonstrate that the cosmological posteriors are robust against variation of the richness–mass relation model and to systematics associated with the calibration of the selection function. In combination with baryon acoustic oscillation data and big bang nucleosynthesis data (Cooke et al.), we constrain the Hubble rate to be h = 0.66 ± 0.02, independent of the CMB. Future work aimed at improving our understanding of the scatter of the richness–mass relation has the potential to significantly improve the precision of our cosmological posteriors. The methods described in this work were developed for use in the forthcoming analysis of cluster abundances in the DES. Our SDSS analysis constitutes the first part of a staged-unblinding analysis of the full DES data set.

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47

Duary, Tanima, e Narayan Banerjee. "Cosmological models reconstructed from jerk: A thermodynamic analysis". New Astronomy 92 (aprile 2022): 101726. http://dx.doi.org/10.1016/j.newast.2021.101726.

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48

Pasqua, Antonio, Surajit Chattopadhyay, Davood Momeni, Muhammad Raza, Ratbay Myrzakulov e Mir Faizal. "Cosmological reconstruction andOmdiagnostic analysis of Einstein-Aether theory". Journal of Cosmology and Astroparticle Physics 2017, n. 04 (10 aprile 2017): 015. http://dx.doi.org/10.1088/1475-7516/2017/04/015.

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49

Fujiwara, Y., e J. Soda. "Wavelet Analysis of One-Dimensional Cosmological Density Fluctuations". Progress of Theoretical Physics 95, n. 6 (1 giugno 1996): 1059–77. http://dx.doi.org/10.1143/ptp.95.1059.

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50

Charters, Tiago C., Ana Nunes e José P. Mimoso. "Stability analysis of cosmological models through Lyapunov's method". Classical and Quantum Gravity 18, n. 9 (10 aprile 2001): 1703–13. http://dx.doi.org/10.1088/0264-9381/18/9/307.

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