Constraining Interactions in Cosmology's Dark Sector

Bean, Rachel; Flanagan, Eanna E.; Laszlo, Istvan; Trodden, Mark

doi:10.48550/arxiv.0808.1105

Cited by 29 publications

(41 citation statements)

References 59 publications

(96 reference statements)

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“…Even though the actual value of the upper limit depends on the form of the quintessence potential and that of the coupling, the obtained limits for other potentials and couplings are of the same order as shown in Ref. [7]. Furthermore, Eqs.…”

supporting

confidence: 69%

Effects on the two-point correlation function from the coupling of quintessence to dark matter

Lee

Liu

2010

Phys. Rev. D

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We investigate the effects of the nonminimal coupling between the scalar field dark energy (quintessence) and the dark matter on the two-point correlation function. It is well known that this coupling shifts the turnover scale as well as suppresses the amplitude of the matter power spectrum. However, these effects are too small to be observed when we limit the coupling strength to be consistent with observations. Since the coupling of quintessence to baryons is strongly constrained, species-dependent coupling may arise. This results in a baryon bias that is different from unity. Thus, we investigate the correlation function in this coupled model. We are able to observe the enhancement of the baryon acoustic oscillation (BAO) peak due to the increasing bias factor of baryon from this species-dependent coupling. In order to avoid the damping effect of the BAO signature in the matter power spectrum due to nonlinear clustering, we consider the coupling effect on the BAO bump in the linear regime. This provides an alternative method to constrain the coupling of dark energy to dark matter. PACS numbers: 95.36.+x, 95.35.+d, 98.80.Cq Because of the strong constraint on the coupling of the scalar field dark energy (quintessence) to baryons from the local gravity, we investigate the effect of the speciesdependent coupling [1,2] by considering a model in which the quintessence Q is only coupled to the cold dark matter (CDM). We assume a Yukawa-type coupling, m c ¼ e ncQ m Ã c , where m Ã c is the bare mass of the CDM [3,4]. This specific choice of coupling requires that the present value of the scalar field vanishes in order to satisfy m c ¼ m Ã c at present. Then, we are able to write the general action including this interaction asis the reduced Planck mass, VðQÞ is the potential of Q, and L r anddenote the Lagrangian of radiation, CDM, and baryons, respectively. We adopt VðQÞ ¼ V 0 expðQ 2 =2Þ with ¼ 5 in the following [4,5]. However, the main conclusions are independent of the form of the scalar field potential (see below). Because of the coupling, the scalings of the CDM and the quintessence energy densities are changed, respectively, to [5] c ðaÞ ¼ 0 c a À3þ ; where lnðaÞ ¼ n c ½QðaÞ À Qð1Þ;where H ðda=dÞ=a, ! Q is the equation of state of the quintessential dark energy (DE), 0 c denotes the present value of the CDM energy density, the present value of scale factor a 0 ¼ 1, and primes mean the differentiation with respect to the conformal time . Generally, the sign of depends on both the model and the form of the coupling. The linear perturbation equations for the CDM and the scalar field Q in the synchronous gauge are [6] 0 c ¼ À c À 1 2 h 0 þ n c Q 0 ; (4) 0 c ¼ ÀH c þ n c ðk 2 Q À Q 0 c Þ;Q 00 þ 2H Q 0 þ k 2 Q þ a 2 " M 2

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confidence: 69%

Effects on the two-point correlation function from the coupling of quintessence to dark matter

Lee

Liu

2010

Phys. Rev. D

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“…Equivalence principle violations of both types discussed above, Newtonian or post-Newtonian, should be clearly distinguished from yet another type of violation, which is most commonly discussed in the cosmology literature -where there is explicit breaking of equivalence principle at the level of the microscopic action, e.g. elementary baryons and dark matter particles are coupled to the scalar with different strengths [39,40,41,42,43,44]. In this paper, we are interested in theories where this breaking is not put in 'by hand' i.e.…”

Section: Introductionmentioning

confidence: 99%

Equivalence principle implications of modified gravity models

2009

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Theories that attempt to explain the observed cosmic acceleration by modifying general relativity all introduce a new scalar degree of freedom that is active on large scales, but is screened on small scales to match experiments. We demonstrate that if such screening occurs via the chameleon mechanism, such as in f (R) theory, it is possible to have order unity violation of the equivalence principle, despite the absence of explicit violation in the microscopic action. Namely, extended objects such as galaxies or constituents thereof do not all fall at the same rate. The chameleon mechanism can screen the scalar charge for large objects but not for small ones (large/small is defined by the depth of the gravitational potential, and is controlled by the scalar coupling). This leads to order one fluctuations in the ratio of the inertial mass to gravitational mass. We provide derivations in both Einstein and Jordan frames. In Jordan frame, it is no longer true that all objects move on geodesics; only unscreened ones, such as test particles, do. In contrast, if the scalar screening occurs via strong coupling, such as in the DGP braneworld model, equivalence principle violation occurs at a much reduced level. We propose several observational tests of the chameleon mechanism: 1. small galaxies should accelerate faster than large galaxies, even in environments where dynamical friction is negligible; 2. voids defined by small galaxies would appear larger compared to standard expectations; 3. stars and diffuse gas in small galaxies should have different velocities, even if they are on the same orbits; 4. lensing and dynamical mass estimates should agree for large galaxies but disagree for small ones. We discuss possible pitfalls in some of these tests. The cleanest is the third one where mass estimate from HI rotational velocity could exceed that from stars by 30% or more. To avoid blanket screening of all objects, the most promising place to look is in voids.

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“…As discussed by Bovy and Farrar [16], the existence of such a force could alleviate some tensions in the ΛCDM fit to astrophysical and cosmological observations. Recently, Kesden and Kamionkowski have derived approximate bounds on the strength of a long range dark force from tidal streams in the Sagitarius galaxy [17], while Bean et al have arrived at limits analyses of the CMB [18]. Additional constraints can be obtained from terrestrial experiments if the dark matter is not sterile [19,20,16].…”

Section: Precision Testsmentioning

confidence: 99%

Fundamental Symmetries of the Early Universe and the Precision Frontier

Ramsey-Musolf¹

2009

AIP Conference Proceedings

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Abstract. The search for the next Standard Model of fundamental interactions is being carried out at two frontiers: the high energy frontier involving the Tevatron and Large Hadron Collider, and the high precision frontier where the focus is largely on low energy experiments. I discuss the unique and powerful window on new physics provided by the precision frontier and its complementarity to the information we hope to gain from present and future colliders.

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Constraining Interactions in Cosmology's Dark Sector

Cited by 29 publications

References 59 publications

Effects on the two-point correlation function from the coupling of quintessence to dark matter

Effects on the two-point correlation function from the coupling of quintessence to dark matter

Equivalence principle implications of modified gravity models

Fundamental Symmetries of the Early Universe and the Precision Frontier

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