Neutrino footprint in large scale structure

Abstract

Recent constrains on the sum of neutrino masses inferred by analyzing cosmological data, show that detecting a non-zero neutrino mass is within reach of forthcoming cosmological surveys, implying a direct determination of the absolute neutrino mass scale. The measurement relies on constraining the shape of the matter power spectrum below the neutrino free streaming scale: massive neutrinos erase power at these scales. Detection of a lack of small-scale power, however, could also be due to a host of other effects. It is therefore of paramount importance to validate neutrinos as the source of power suppression at small scales. We show that, independent on hierarchy, neutrinos always show a footprint on large, linear scales; the exact location and properties can be related to the measured power suppression (an astrophysical measurement) and atmospheric neutrinos mass splitting (a neutrino oscillation experiment measurement). This feature can not be easily mimicked by systematic uncertainties or modifications in the cosmological model. The measurement of such a feature, up to 1% relative change in the power spectrum, is a smoking gun for confirming the determination of the absolute neutrino mass scale from cosmological observations. It also demonstrates the synergy of astrophysics and particle physics experiments. PACS numbers:In the past few years, there has been an amazing progress in cosmology. An accurate cosmic microwave background (CMB) spectrum, both in temperature and polarization has been measured by Planck [1] and WMAP [2]. The expansion history of the Universe has been mapped in several ways: with measurements of the Baryon Acoustic Oscillation (BAO) scale by the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS) [3] and others [4,5]; by the luminosity distance relation as given by Type 1A supernova data e.g., [6]; via the direct measurement of the Hubble parameter with cosmic chronometers [7,8].Finally, large scale structure (LSS) has been probed by a variety of surveys (galaxies e.g., [9][10][11][12], weak lensing e.g., [13][14][15][16][17], Lyα [18]) with increased sensitivity to the scale and redshift dependences of the matter power spectrum, thanks also to redshift space distortion measurements e.g., [19,20].All this wealth of cosmological data show a consistent ΛCDM model with improved precision on parameters and better control of systematics. If included as a parameter in the model, total neutrino mass bounds have significantly improved in a variety of analysis, yielding an upper bound slightly higher than 100 meV [18,21]. Massive neutrinos free stream out of potential wells, erasing fluctuations and thus suppressing power on small scales e.g., [22,23]; the measured small scale power is consistent with the standard (massless neutrino) ΛCDM model and inconsistent with large neutrino masses. These bounds are very close to the limit that separates inverted and normal ordering and is within a factor of two of the lower limit of the sum of neutrino masses set by oscill...

Efficient computation of galaxy bias with neutrinos and other relics

“…10 show a bump at scales k = 10 −3 − 10 −2 h Mpc −1 , when including neutrinos. This result was expected for the matter power spectrum [74,103], but we see that the scale-dependence of the linear bias enhances the bump in the halo power spectrum to the half-percent level. This enhancement is also present in the rest of the relics we have studied, although it is too small to warrant any further consideration.…”

The Higgs boson can delay reheating after inflation

“…Adiabatic fluctuations at smaller scales are somewhat less constrained and they can be masked by other effects. For example, massive neutrinos are known to suppress power at small scales [68][69][70][71][72], hence disentangling the extra contributions from Higgs-delayed reheating from possible suppression factors can be challenging.…”

“…Adiabatic fluctuations at smaller scales are somewhat less constrained and they can be masked by other effects. For example, massive neutrinos are known to suppress power at small scales [68][69][70][71][72], hence disentangling the extra contributions from Higgs-delayed reheating from possible suppression factors can be challenging. Furthermore, if the above mentioned inhomogeneity of the reheat temperature is applied to the case of inflationary leptogenesis, it can lead to a space-dependent baryon number.…”