{'fraction_non_alphanumeric': 0.04228624535315985, 'fraction_numerical': 0.011617100371747211, 'mean_word_length': 4.931129476584022, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Indication for Primordial Anisotropies in the Neutrino Background from WMAP and SDSS

Introduction Recent cosmological data coming from measurements of the Cosmic Microwave Background (CMB) anisotropies (see e.g. [1]), on galaxy clustering (see e.g. [2]) and, more recently, on Lymanalpha Forest clouds (see e.g. [3]) are in spectacular agreement with the expectations of the so-called standard model of structure formation, based on primordial, purely adiabatic inflationary perturbations and a cosmological constant (see e.g. [3],[4]). Cosmology is therefore becoming more and more a powerful laboratory where physics not easily accessible on Earth can be tested and verified. An excellent example of this comes from the new cosmological constraints on neutrino physics. According to the standard model, a cosmic Neutrino Background (NB), similar to the CMB, should exist in our universe with a density of approximately nν ∼ 57/cm 3 per flavor. Neutrinos of mass ≪ 10eV would still be relativistic today with a Fermi-Dirac spectrum at a temperature T ∼ 2K, while more massive neutrinos would be non relativistic and clustered around galaxies with a typical velocity of vν ∼ 200km/s. Therefore, despite the high density of cosmological neutrinos a direct detection is virtually impossible due to their extremely low energy and cross sections (see e.g. [5]). However, cosmological neutrinos have a profound impact on cosmology since they change the expansion history of the universe and affect the growth of perturbations (see [6] for a detailed account). As a consequence, recent cosmological data do provide strong – albeit indirect – evidence for the presence of a NB (see e.g. [7]) and have been used to put upper limits on absolute neutrino masses competitive with those from laboratory experiments (see e.g. [3], [8]). In this letter we show that current cosmological data now provide for the first time an interesting indication for primordial anisotropies in the NB. Although inflationary anisotropies in the NB at the level of ∼ 10 are expected in the standard scenario, a direct detection is clearly impossible. However, anisotropies in 10 10