Cosmology and Fundamental Physics with the Euclid Satellite

Euclid is a European Space Agency medium-class mission selected for launch in 2020 within the cosmic vision 2015-2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid's Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission.

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References

Miranda V, Joras S, Waga I, Quartin M . Viable singularity-free f(R) gravity without a cosmological constant. Phys Rev Lett. 2009; 102(22):221101. DOI: 10.1103/PhysRevLett.102.221101. View

Sakstein J, Jain B . Implications of the Neutron Star Merger GW170817 for Cosmological Scalar-Tensor Theories. Phys Rev Lett. 2018; 119(25):251303. DOI: 10.1103/PhysRevLett.119.251303. View

Frieman , Hill , Stebbins , Waga I . Cosmology with ultralight pseudo Nambu-Goldstone bosons. Phys Rev Lett. 1995; 75(11):2077-2080. DOI: 10.1103/PhysRevLett.75.2077. View

Walsh D, Carswell R, Weymann R . 0957 + 561 A, B: twin quasistellar objects or gravitational lens?. Nature. 1979; 279(5712):381-4. DOI: 10.1038/279381a0. View

Bekenstein . Relation between physical and gravitational geometry. Phys Rev D Part Fields. 1993; 48(8):3641-3647. DOI: 10.1103/physrevd.48.3641. View

Brookfield A, van de Bruck C, Mota D, Tocchini-Valentini D . Cosmology with massive neutrinos coupled to dark energy. Phys Rev Lett. 2006; 96(6):061301. DOI: 10.1103/PhysRevLett.96.061301. View

Hui L . Unitarity bounds and the cuspy halo problem. Phys Rev Lett. 2001; 86(16):3467-70. DOI: 10.1103/PhysRevLett.86.3467. View

Andrews M, Goon G, Hinterbichler K, Stokes J, Trodden M . Massive gravity coupled to Galileons is ghost-free. Phys Rev Lett. 2013; 111(6):061107. DOI: 10.1103/PhysRevLett.111.061107. View

Guzzo L, Pierleoni M, Meneux B, Branchini E, Fevre O, Marinoni C . A test of the nature of cosmic acceleration using galaxy redshift distortions. Nature. 2008; 451(7178):541-4. DOI: 10.1038/nature06555. View

10.

Spergel , STEINHARDT . Observational evidence for self-interacting cold dark matter. Phys Rev Lett. 2000; 84(17):3760-3. DOI: 10.1103/PhysRevLett.84.3760. View

11.

Uzan J . Varying Constants, Gravitation and Cosmology. Living Rev Relativ. 2017; 14(1):2. PMC: 5256069. DOI: 10.12942/lrr-2011-2. View

12.

Seljak U, Hamaus N, Desjacques V . How to suppress the shot noise in galaxy surveys. Phys Rev Lett. 2009; 103(9):091303. DOI: 10.1103/PhysRevLett.103.091303. View

13.

Geller M, Huchra J . Mapping the universe. Science. 1989; 246(4932):897-903. DOI: 10.1126/science.246.4932.897. View

14.

Damour , Gibbons , Gundlach . Dark matter, time-varying G, and a dilaton field. Phys Rev Lett. 1990; 64(2):123-126. DOI: 10.1103/PhysRevLett.64.123. View

15.

Hu W, Barkana R, Gruzinov A . Fuzzy cold dark matter: the wave properties of ultralight particles. Phys Rev Lett. 2000; 85(6):1158-61. DOI: 10.1103/PhysRevLett.85.1158. View

16.

de Rham C, Gabadadze G, Tolley A . Resummation of massive gravity. Phys Rev Lett. 2011; 106(23):231101. DOI: 10.1103/PhysRevLett.106.231101. View

17.

Csaki C, Kaloper N, Terning J . Dimming supernovae without cosmic acceleration. Phys Rev Lett. 2002; 88(16):161302. DOI: 10.1103/PhysRevLett.88.161302. View

18.

Langlois D, Renaux-Petel S, Steer D, Tanaka T . Primordial fluctuations and non-Gaussianities in multifield Dirac-Born-Infeld inflation. Phys Rev Lett. 2008; 101(6):061301. DOI: 10.1103/PhysRevLett.101.061301. View

19.

Himmetoglu B, Contaldi C, Peloso M . Instability of anisotropic cosmological solutions supported by vector fields. Phys Rev Lett. 2009; 102(11):111301. DOI: 10.1103/PhysRevLett.102.111301. View

20.

Dunkley J, Bucher M, Ferreira P, Moodley K, Skordis C . Measuring the geometry of the universe in the presence of isocurvature modes. Phys Rev Lett. 2006; 95(26):261303. DOI: 10.1103/PhysRevLett.95.261303. View