# Constraints on the interacting vacuum - geodesic CDM scenario

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**Constraints on the interacting vacuum - geodesic CDM scenario.** / Martinelli, Matteo; Hogg, Natalie; Peirone, Simone; Bruni, Marco; Wands, David.

Research output: Contribution to journal › Article › peer-review

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*Monthly Notices of the Royal Astronomical Society*, vol. 488, no. 3, pp. 3423-3438. https://doi.org/10.1093/mnras/stz1915

### APA

*Monthly Notices of the Royal Astronomical Society*,

*488*(3), 3423-3438. https://doi.org/10.1093/mnras/stz1915

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### RIS

TY - JOUR

T1 - Constraints on the interacting vacuum - geodesic CDM scenario

AU - Martinelli, Matteo

AU - Hogg, Natalie

AU - Peirone, Simone

AU - Bruni, Marco

AU - Wands, David

PY - 2019/9

Y1 - 2019/9

N2 - We investigate an interacting dark sector scenario in which the vacuum energy is free to interact with cold dark matter (CDM), which itself is assumed to cluster under the sole action of gravity, i.e. it is in freefall (geodesic), as in ΛCDM. The interaction is characterized by a dimensionless coupling qV(z), in general a function of redshift. Aiming to reconstruct the evolution of the coupling, we use cosmic microwave background data from Planck 2015, along with baryon acoustic oscillation, redshift space distortion, and Type Ia supernova measurements to constrain various parametrizations of qV(z). We present the full linear perturbation theory of this interacting scenario and use Monte Carlo Markov Chains (MCMC) sampling to study five different cases: two cases in which we have ΛCDM evolution in the distant past, until a set redshift ztrans, below which the interaction switches on and qV is the single-sampled parameter, with ztrans fixed at ztrans = 3000 and 0.9, respectively; a case where we allow this transition redshift to vary along with qV; a case in which the vacuum energy is zero for z > ztrans and then begins to grow once the interaction switches on; and the final case in which we bin qV(z) in four redshift bins to investigate the possibility of a dynamical interaction, reconstructing the redshift evolution of the function using Gaussian processes. We find that, in all cases where the high-redshift evolution is not modified, the results are compatible with a vanishing coupling, thus finding no significant deviation from ΛCDM.

AB - We investigate an interacting dark sector scenario in which the vacuum energy is free to interact with cold dark matter (CDM), which itself is assumed to cluster under the sole action of gravity, i.e. it is in freefall (geodesic), as in ΛCDM. The interaction is characterized by a dimensionless coupling qV(z), in general a function of redshift. Aiming to reconstruct the evolution of the coupling, we use cosmic microwave background data from Planck 2015, along with baryon acoustic oscillation, redshift space distortion, and Type Ia supernova measurements to constrain various parametrizations of qV(z). We present the full linear perturbation theory of this interacting scenario and use Monte Carlo Markov Chains (MCMC) sampling to study five different cases: two cases in which we have ΛCDM evolution in the distant past, until a set redshift ztrans, below which the interaction switches on and qV is the single-sampled parameter, with ztrans fixed at ztrans = 3000 and 0.9, respectively; a case where we allow this transition redshift to vary along with qV; a case in which the vacuum energy is zero for z > ztrans and then begins to grow once the interaction switches on; and the final case in which we bin qV(z) in four redshift bins to investigate the possibility of a dynamical interaction, reconstructing the redshift evolution of the function using Gaussian processes. We find that, in all cases where the high-redshift evolution is not modified, the results are compatible with a vanishing coupling, thus finding no significant deviation from ΛCDM.

KW - RCUK

KW - STFC

KW - ST/N000668/1

KW - ST/N504245/1

U2 - 10.1093/mnras/stz1915

DO - 10.1093/mnras/stz1915

M3 - Article

VL - 488

SP - 3423

EP - 3438

JO - MNRAS

JF - MNRAS

SN - 0035-8711

IS - 3

ER -

ID: 15072899