pdgLive

COSM

$2.84$ $\pm0.15$

COSM

BBN

$2.88$ $\pm0.17$

⁴

IVANOV

COSM

Planck and BOSS

$\text{2.3 - 3.2}$

⁵

VERDE

2017

COSM

$2.88$ $\pm0.16$

⁶

2016

COSM

BBN

$2.88$ $\pm0.20$

⁷

ROSSI

2015

COSM

$3.3$ $\pm0.5$

⁸

ADE

COSM

Planck

$3.78$ ${}^{+0.31}_{-0.30}$

⁹

COSTANZI

COSM

$3.29$ $\pm0.31$

¹⁰

HOU

COSM

$<3.80$

¹¹

LEISTEDT

COSM

$<4.10$

¹²

MORESCO

COSM

$<5.79$

¹³

XIA

COSM

$<4.08$

MANGANO

2011

COSM

BBN

$\text{0.9 - 8.2}$

¹⁴

ICHIKAWA

2007

COSM

$\text{3 - 7}$

¹⁵

CIRELLI

COSM

$\text{2.7 - 4.6}$

¹⁶

HANNESTAD

COSM

$\text{3.6 - 7.4}$

¹⁵

SELJAK

COSM

$<4.4$

¹⁷

2005

COSM

$<3.3$

¹⁸

BARGER

COSM

$\text{1.4 - 6.8}$

¹⁹

CROTTY

COSM

$\text{1.9 - 6.6}$

¹⁹

PIERPAOLI

COSM

$\text{2 - 4}$

LISI

COSM

BBN

$<4.3$

COSM

BBN

$<4.9$

COPI

Cosmology

$<3.6$

HATA

High D/H quasar abs.

$<4.0$

BBN; high ${}^{4}\mathrm {He}$ and ${}^{7}\mathrm {Li}$

$<4.7$

CARDALL

COSM

High D/H quasar abs.

$<3.9$

COSM

BBN; high ${}^{4}\mathrm {He}$ and ${}^{7}\mathrm {Li}$

$<4.5$

KERNAN

COSM

High D/H quasar abs.

$<3.6$

1995

BBN; ${}\geq{}3$ massless ${{\mathit \nu}}$

$<3.3$

WALKER

1991

Cosmology

$<3.4$

1990

Cosmology

$<4$

1984

Cosmology

$<4$

1979

Cosmology

$<7$

Cosmology

Cosmology

$<16$

²⁰

Cosmology

Cosmology

¹	YEH 2022 combines Planck 2018 CMB data with BBN and observations of deuterium and ${}^{}\mathrm {Helium}$-4. Supersedes FIELDS 2020 .

²	AGHANIM 2020 best fit on number of neutrino types is based on Planck data combined with lensing and baryon acoustic oscillations (BAO). Without BAO, they find $2.89$ ${}^{+0.18}_{-0.19}$. Several other values are quoted using different combinations of data.

³	FIELDS 2020 combines Planck 2018 CMB data with BBN and observations of deuterium and Helium-4.

⁴	IVANOV 2020 combines 2018 Planck CMB data with baryon acoustic oscillation data from BOSS. This study is based on a full-shape likelhood for the redshift-space galaxy power spectrum of the BOSS data.

⁵	Uses Planck Data combined with an independent standard measure of distance to the sound horizon to set a limit on the total number of neutrinos. Only CMB and early-time information are used.

⁶	CYBURT 2016 combines Planck 2015 CMB data with BBN and observations of deuterium and Helium-4.

⁷	ROSSI 2015 sets limits on the number of neutrino types using BOSS Lyman alpha forest data combined with Planck CMB data and baryon acoustic oscillations.

⁸	Fit to the number of neutrino degrees of freedom from Planck CMB data along with WMAP polarization, high L, and BAO data.

⁹	Fit to the number of neutrinos degrees of freedom from Planck CMB data along with BAO, shear and cluster data.

¹⁰	Fit based on the SPT-SZ survey combined with CMB, BAO, and ${{\mathit H}_{{0}}}$ data.

¹¹	Constrains the number of neutrino degrees of freedom (marginalizing over the total mass) from CMB, CMB lensing, BAO, and galaxy clustering data.

¹²	Limit on the number of light neutrino types from observational Hubble parameter data with seven-year WMAP data, SPT, and the most recent estimate of ${{\mathit H}_{{0}}}$. Best fit is $3.45$ $\pm0.65$.

¹³	Limit on the number of light neutrino types from the CFHTLS combined with seven-year WMAP data and a prior on the Hubble parameter. Best fit is $4.17$ ${}^{+1.62}_{-1.26}$. Limit is relaxed to $3.98$ ${}^{+2.02}_{-1.20}$ when small scales affected by non-linearities are removed.

¹⁴	Constrains the number of neutrino types from recent CMB and large scale structure data. No priors on other cosmological parameters are used.

¹⁵	Constrains the number of neutrino types from recent CMB, large scale structure, Lyman-alpha forest, and SN1a data. The slight preference for $\mathit N_{{{\mathit \nu}}}$ $>$ 3 comes mostly from the Lyman-alpha forest data.

¹⁶	Constrains the number of neutrino types from recent CMB and large scale structure data. See also HAMANN 2007 .

¹⁷	Limit on the number of neutrino types based on ${}^{4}\mathrm {He}$ and D/H abundance assuming a baryon density fixed to the WMAP data. Limit relaxes to 4.6 if D/H is not used or to 5.8 if only D/H and the CMB are used. See also CYBURT 2001 and CYBURT 2003 .

¹⁸	Limit on the number of neutrino types based on combination of WMAP data and big-bang nucleosynthesis. The limit from WMAP data alone is 8.3. See also KNELLER 2001 . $\mathit N_{{{\mathit \nu}}}{}\geq{}$3 is assumed to compute the limit.

¹⁹	95$\%$ confidence level range on the number of neutrino flavors from WMAP data combined with other CMB measurements, the 2dfGRS data, and HST data.

²⁰	SHVARTSMAN 1969 limit inferred from his equations.

References:

YEH

2022

JCAP 2210 046

Probing physics beyond the standard model: limits from BBN and the CMB independently and combined

AGHANIM

AA 641 A6

Planck 2018 results. VI. Cosmological parameters

JCAP 2003 010

Big-Bang Nucleosynthesis after Planck

Also

JCAP 2011 E02 (errat.)

Big-Bang Nucleosynthesis after Planck

IVANOV

PR D101 083504

Cosmological Parameters and Neutrino Masses from the Final Planck and Full-Shape BOSS Data

VERDE

2017

JCAP 1704 023

Early Cosmology Constrained

2016

RMP 88 015004

Big Bang Nucleosynthesis: 2015

ROSSI

2015

PR D92 063505

Constraints on Dark Radiation from Cosmological Probes

ADE

AA 571 A16

Planck 2013 Results. XVI. Cosmological Parameters

COSTANZI

JCAP 1410 081

Neutrino Constraints: what Large-Scale Structure and CMB Data are Telling Us?

HOU

APJ 782 74

Constraints on Cosmology from the Cosmic Microwave Background Power Spectrum of the 2500 deg${}^{2}$ SPT-SZ Survey

LEISTEDT

PRL 113 041301

No New Cosmological Concordance with Massive Sterile Neutrinos

MORESCO

JCAP 1207 053

New Constraints on Cosmological Parameters and Neutrino Properties using the Expansion Rate of the Universe to z ~ 1.75

XIA

JCAP 1206 010

Constraints on Massive Neutrinos from the CFHTLS Angular Power Spectrum

MANGANO

2011

PL B701 296

A Robust Upper Limit on ${{\mathit N}_{{eff}}}$ from BBN, circa 2011

ICHIKAWA

2007

JCAP 0705 007

Constraint on the Effective Number of Neutrino Species from the WMAP and SDSS LRG Power Spectra

CIRELLI

JCAP 0612 013

Cosmology of Neutrinos and Extra-Light Particles after WMAP3

HANNESTAD

JCAP 0611 016

Neutrino Masses and Cosmic Radiation Density: Combined Analysis

SELJAK

JCAP 0610 014

Cosmological Parameters from Combining the Lyman-$\alpha $ Forest with CMB, Galaxy Clustering and SN Constraints

2005

ASP 23 313

New BBN Limits on Physics Beyond the Standard Model from ${}^{4}\mathrm {He}$

BARGER

2003C

PL B566 8

Effective Number of Neutrinos and Baryon Asymmetry from BBN and WMAP

CROTTY

PR D67 123005

Measuring the Cosmological Background of Relativistic Particles with the Wilkinson Microwave Anisotropy Probe

PIERPAOLI

MNRAS 342 L63

Constraints on the Cosmic Neutrino Background

LISI

PR D59 123520

The Big Bang Nucleosynthesis Limit on N$_{{{\mathit \nu}}}$

ASP 11 403

Generalized Limits to the Number of Light Particle Degrees of Freedom from Big Bang Nucleosynthesis

COPI

PR D55 3389

The Big Bang Nucleosynthesis Limit to the Number of Neutrino Species

HATA

1997B

PR D55 540

Cosmological Implications of Two Conflicting Deuterium Abundances

ASP 7 27

A Big Bang Nucleosynthesis Likelihood Analysis of the Baryon to Photon Ratio and the Number of Light Particle Degrees of Freedom

CARDALL

1996B

APJ 472 435

Big Bang Nucleosynthesis in Light of Discordant Deuterium Measurements

New Ast 1 77

Model Independent Predictions of Big Bang Nucleosinthesis from ${}^{4}\mathrm {He}$ and ${}^{7}\mathrm {Li}$: Consistency and Implications

KERNAN

PR D54 3681

No Crisis for Big Bang Nucleosynthesis

1995

PL B354 357

A New Look at Neutrino Limits from Big Bang Nucleosynthesis

WALKER

1991

APJ 376 51

Primordial Nucleosynthesis Redux

1990

PL B236 454

Big Bang Nucleosynthesis Revisited

1984

APJ 281 493

Primordial Nucleosynthesis: a Critical Comparison of Theory and Observation