ISIS: a new<i>N</i>-body cosmological code with scalar fields based on RAMSES

Llinares, Claudio; Mota, David F.; Winther, Hans A.

doi:10.1051/0004-6361/201322412

Cited by 119 publications

(111 citation statements)

References 42 publications

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“…Recent years have seen increased interest in studying the effects of modified gravity on these objects, and the community already owns several independent and highly developed codes for this purpose [e.g. 201,202,203].…”

Section: Gravity In Cosmologymentioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

Self Cite

459

210

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Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.Keywords: cosmology -dark energy -cosmological constant problem -modified gravitydark matter -early universe Cosmology has been both blessed and cursed by the establishment of a standard model: ΛCDM. On the one hand, the model has turned out to be extremely predictive, explanatory, and observationally robust, providing us with a substantial understanding of the formation of large-scale structure, the state of the early Universe, and the cosmic abundance of different types of matter and energy. It has also survived an impressive battery of precision observational tests -anomalies are few and far between, and their significance is contentious where they do arise -and its predictions are continually being vindicated through the discovery of new effects (B-mode polarization [1] and lensing [2,3] of the cosmic microwave background (CMB), and the kinetic Sunyaev-Zel'dovich effect [4] being some recent examples). These are the hallmarks of a good and valuable physical theory.On the other hand, the model suffers from profound theoretical difficulties. The two largest contributions to the energy content at late times -cold dark matter (CDM) and the cosmological constant (Λ) -have entirely mysterious physical origins. CDM has so far evaded direct detection by laboratory experiments, and so the particle field responsible for it -presumably a manifestation of "beyond the standard model" particle physics -is unknown. Curious discrepancies also appear to exist between the predicted clustering properties of CDM on small scales and observations. The cosmological constant is even more puzzling, giving rise to quite simply the biggest problem in all of fundamental physics: the question of why Λ appears to take such an unnatural value [5,6,7]. Inflation, the theory of the very early Universe, has also been criticized for being fine-tuned and under-predictive [8], and appears to leave many problems either unsolved or fundamentally unresolvable. These problems are indicative of a crisis.From January 14th-17th 2015, we held a conference in Oslo, Norway to surve...

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Section: Gravity In Cosmologymentioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

Self Cite

459

210

View full text Add to dashboard Cite

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“…The static simulation was run using the solver that is described in detail in Llinares et al [22]. The background evolution in all the simulations is given by a flat ΛCDM cosmology (Ω m = 0.267, Ω Λ = 0.733 and H 0 = 71.9 km/sec/Mpc).…”

Section: Cosmological Simulationsmentioning

confidence: 99%

Cosmological simulations of screened modified gravity out of the static approximation: Effects on matter distribution

Llinares

Mota

2014

Phys. Rev. D

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In the context of scalar tensor theories for gravity, there is a universally adopted hypothesis when running N-body simulations that time derivatives in the equation of motion for the scalar field are negligible. In this work we propose to test this assumption for one specific scalar-tensor model with a gravity screening mechanism: the symmetron. To this end, we implemented the necessary modifications to include the non-static terms in the N-body code Ramses. We present test cases and results from cosmological simulations. Our main finding when comparing static vs. non-static simulations is that the global power spectrum is only slightly modified when taking into account the inclusion of non-static terms. On the contrary, we find that the calculation of the local power spectrum gives different measurements. Such results imply one must be careful when assuming the quasi-static approximation when investigating the environmental effects of modified gravity and screening mechanisms in structure formation of halos and voids distributions.

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“…In particular, we can set up a more general formalism in which the background expansion data, including SN Ia, BAO, CMB shift parameter, Hubble expansion data, joined with the growth rate data of LSSs in order to put constraints on the parameters of cosmology and DE models (see Cooray et al 2004;Corasaniti et al 2005;Mota et al 2007Mota et al , 2008Basilakos et al 2010;Gannouji et al 2010;Mota et al 2010;Blake et al 2011b;Nesseris et al 2011;Basilakos & Pouri 2012;Chuang et al 2013;Contreras et al 2013;Llinares & Mota 2013;Llinares et al 2014;Li et al 2014;Yang et al 2014;Basilakos 2015;Mehrabi et al 2015aMehrabi et al , 2015bBasilakos 2016;Bonilla Rivera & Farieta 2016;Fay 2016;Malekjani et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Constraints to Dark Energy Using PADE Parameterizations

Rezaei

Malekjani

Basilakos

et al. 2017

ApJ

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We put constraints on dark energy (DE) properties using PADE parameterization, and compare it to the same constraints using Chevalier-Polarski-Linder (CPL) and ΛCDM, at both the background and the perturbation levels. The DE equation of the state parameter of the models is derived following the mathematical treatment of PADE expansion. Unlike CPL parameterization, PADE approximation provides different forms of the equation of state parameter that avoid the divergence in the far future. Initially we perform a likelihood analysis in order to put constraints on the model parameters using solely background expansion data, and we find that all parameterizations are consistent with each other. Then, combining the expansion and the growth rate data, we test the viability of PADE parameterizations and compare them with CPL and ΛCDM models, respectively. Specifically, we find that the growth rate of the current PADE parameterizations is lower than ΛCDM model at low redshifts, while the differences among the models are negligible at high redshifts. In this context, we provide for the first time a growth index of linear matter perturbations in PADE cosmologies. Considering that DE is homogeneous, we recover the well-known asymptotic value of the growth index (namely . Finally, we generalize the growth index analysis in the case where γ is allowed to vary with redshift, and we find that the form of z g ( ) in PADE parameterization extends that of the CPL and ΛCDM cosmologies, respectively.

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ISIS: a newN-body cosmological code with scalar fields based on RAMSES

Cited by 119 publications

References 42 publications

BeyondΛCDM: Problems, solutions, and the road ahead

BeyondΛCDM: Problems, solutions, and the road ahead

Cosmological simulations of screened modified gravity out of the static approximation: Effects on matter distribution

Constraints to Dark Energy Using PADE Parameterizations

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