# Do joint CMB and HST data support a scale invariant spectrum?

## Abstract

We combine current measurements of the local expansion rate, H {sub 0}, and Big Bang Nucleosynthesis (BBN) estimates of helium abundance with the latest cosmic microwave background (CMB) data from the Planck Collaboration to discuss the observational viability of the scale invariant Harrison-Zeldovch-Peebles (HZP) spectrum. We also analyze some of its extensions, namely, HZP + Y {sub P} and HZP + N {sub eff}, where Y {sub P} is the primordial helium mass fraction and N {sub eff} is the effective number of relativistic degrees of freedom. We perform a Bayesian analysis and show that the latter model is favored with respect to the standard cosmology for values of N {sub eff} lying in the interval 3.70 ± 0.13 (1σ), which is currently allowed by some independent analyses.

- Authors:

- Departamento de Astronomia, Observatório Nacional, 20921-400, Rio de Janeiro, RJ (Brazil)

- Publication Date:

- OSTI Identifier:
- 22679938

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 04; Other Information: Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; COSMOLOGY; DEGREES OF FREEDOM; EXPANSION; MASS; NUCLEOSYNTHESIS; RELATIVISTIC RANGE; RELICT RADIATION; SPECTRA

### Citation Formats

```
Benetti, Micol, Graef, Leila L., and Alcaniz, Jailson S., E-mail: micolbenetti@on.br, E-mail: leilagraef@on.br, E-mail: alcaniz@on.br.
```*Do joint CMB and HST data support a scale invariant spectrum?*. United States: N. p., 2017.
Web. doi:10.1088/1475-7516/2017/04/003.

```
Benetti, Micol, Graef, Leila L., & Alcaniz, Jailson S., E-mail: micolbenetti@on.br, E-mail: leilagraef@on.br, E-mail: alcaniz@on.br.
```*Do joint CMB and HST data support a scale invariant spectrum?*. United States. doi:10.1088/1475-7516/2017/04/003.

```
Benetti, Micol, Graef, Leila L., and Alcaniz, Jailson S., E-mail: micolbenetti@on.br, E-mail: leilagraef@on.br, E-mail: alcaniz@on.br. Sat .
"Do joint CMB and HST data support a scale invariant spectrum?". United States.
doi:10.1088/1475-7516/2017/04/003.
```

```
@article{osti_22679938,
```

title = {Do joint CMB and HST data support a scale invariant spectrum?},

author = {Benetti, Micol and Graef, Leila L. and Alcaniz, Jailson S., E-mail: micolbenetti@on.br, E-mail: leilagraef@on.br, E-mail: alcaniz@on.br},

abstractNote = {We combine current measurements of the local expansion rate, H {sub 0}, and Big Bang Nucleosynthesis (BBN) estimates of helium abundance with the latest cosmic microwave background (CMB) data from the Planck Collaboration to discuss the observational viability of the scale invariant Harrison-Zeldovch-Peebles (HZP) spectrum. We also analyze some of its extensions, namely, HZP + Y {sub P} and HZP + N {sub eff}, where Y {sub P} is the primordial helium mass fraction and N {sub eff} is the effective number of relativistic degrees of freedom. We perform a Bayesian analysis and show that the latter model is favored with respect to the standard cosmology for values of N {sub eff} lying in the interval 3.70 ± 0.13 (1σ), which is currently allowed by some independent analyses.},

doi = {10.1088/1475-7516/2017/04/003},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 04,

volume = 2017,

place = {United States},

year = {Sat Apr 01 00:00:00 EDT 2017},

month = {Sat Apr 01 00:00:00 EDT 2017}

}