SciPost Astronomy最新文献

{"title":"Model-independent determination of the cosmic growth factor","authors":"S. Haude, Shabnam Salehi, Sof'ia Vidal, M. Maturi, Matthias Bartelmann Theoretical Astrophysics, Zah, H. University, T. Physics","doi":"10.21468/scipostastro.2.1.001","DOIUrl":"https://doi.org/10.21468/scipostastro.2.1.001","url":null,"abstract":"The two most important functions describing the evolution of the\u0000universe and its structures are the expansion function\u0000E(a)E(a)\u0000and the linear growth factor D_+(a)D+(a).\u0000It is desirable to constrain them based on a minimum of assumptions in\u0000order to avoid biases from assumed cosmological models. The expansion\u0000function has been determined in previous papers in a model-independent\u0000way using distance moduli to type-Ia supernovae and assuming only a\u0000metric theory of gravity, spatial isotropy and homogeneity. Here, we\u0000extend this analysis in three ways: (1) We enlarge the data sample by\u0000combining measurements of type-Ia supernovae with measurements of\u0000baryonic acoustic oscillations; (2) we substantially simplify and\u0000generalise our method for reconstructing the expansion function; and (3)\u0000we use the reconstructed expansion function to determine the linear\u0000growth factor of cosmic structures, equally independent of specific\u0000assumptions on an underlying cosmological model other than the usual\u0000spatial symmetries. In this approach, the present-day matter-density\u0000parameter Omega_mathrm{m0}Ωm0\u0000is the only relevant parameter for an otherwise purely empirical and\u0000accurate determination of the growth factor. We further show how our\u0000method can be used to derive a possible time evolution of the dark\u0000energy as well as the growth index directly from distance measurements.\u0000Deviations from LambdaΛCDM\u0000that we see in some of our results may be due to possibly insufficient\u0000flexibility of our method that could be cured by larger data samples, a\u0000real departure from LambdaΛCDM\u0000at alesssim0.3a≲0.3,\u0000or hidden systematics in the data. The latter could be a matter of\u0000concern for all type-Ia supernovae analyses based on\u0000LambdaΛCDM\u0000fitting approaches, especially in view of the current dispute on the\u0000value of H_0H0.\u0000These results illustrate the applicability of our approach as a\u0000diagnostic tool.","PeriodicalId":194640,"journal":{"name":"SciPost Astronomy","volume":"156 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122298828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}