A prediction of the standard ΛCDM cosmological model, also confirmed by N-body simulations, is that dark matter (DM) halos are teeming with numerous self-bound substructure, or subhalos. The precise properties of these subhalos represent important probes of the underlying cosmological model. In this work, we use data from the N-body Via Lactea II and ELVIS Milky Way-size simulations to learn about the structure of subhalos with masses 10 6 − 10 11 h −1 M . Thanks to a superb subhalo statistics, by taking a profileindependent approach, we study subhalo properties as a function of the distance to the host halo center and subhalo mass, and provide a set of fits that, including both dependences, accurately describe the subhalo structure. With this at hand, we also investigate the role of subhalos on the search for DM via its annihilation products. Indeed, previous work has shown that subhalos are expected to boost the DM signal of their host halos significantly. Yet, these works have traditionally assumed that subhalos exhibit similar structural properties than those of field halos of the same mass, while it is well known from simulations that subhalos are more concentrated. Building upon the results from our N-body data analysis, we refine the substructure boost model of Sánchez-Conde & Prada (2014). We find boost values that are a factor 2 − 3 higher than previous ones. We further refine our boost model to include unavoidable tidal stripping effects on the subhalo population. For field halos, this only introduces a moderate (∼ 20% − 30%) suppression of the boost. Yet, for subhalos like those hosting the dwarf satellite galaxies of the Milky Way, tidal stripping does play a critical role, the total boost for these objects being only at the level of a few tens of percent in the most optimistic cases. Finally, we provide a parametrization of the boost factor for field halos that can be safely applied over a wide halo mass range.

We present here a scenario, based on a low reheating temperature T(R)<<100 MeV at the end of (the last episode of) inflation, in which the coupling of sterile neutrinos to active neutrinos can be as large as experimental bounds permit (thus making this neutrino "visible" in future experiments). In previous models this coupling was forced to be very small to prevent a cosmological overabundance of sterile neutrinos. Here the abundance depends on how low the reheating temperature is. For example, the sterile neutrino required by the Liquid Scintillator Neutrino Detector result may not have any cosmological problem within our scenario.

2As part of the European LAGUNA design study on a next-generation neutrino detector, we propose the liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) as a multipurpose neutrino observatory. The outstanding successes of the Borexino and KamLAND experiments demonstrate the large potential of liquid-scintillator detectors in low-energy neutrino physics. Low energy threshold, good energy resolution and efficient background discrimination are inherent to the liquidscintillator technique. A target mass of 50 kt will offer a substantial increase in detection sensitivity.At low energies, the variety of detection channels available in liquid scintillator will allow for an energy-and flavor-resolved analysis of the neutrino burst emitted by a galactic Supernova. Due to target mass and background conditions, LENA will also be sensitive to the faint signal of the Diffuse Supernova Neutrino Background. Solar metallicity, time-variation in the solar neutrino flux and deviations from MSW-LMA survival probabilities can be investigated based on unprecedented statistics. Low background conditions allow to search for dark matter by observing rare annihilation neutrinos. The large number of events expected for geoneutrinos will give valuable information on the abundances of Uranium and Thorium and their relative ratio in the Earth's crust and mantle. Reactor neutrinos enable a high-precision measurement of solar mixing parameters. A strong radioactive or pion decay-at-rest neutrino source can be placed close to the detector to investigate neutrino oscillations for short distances and sub-MeV to MeV energies.At high energies, LENA will provide a new lifetime limit for the SUSY-favored proton decay mode into kaon and antineutrino, surpassing current experimental limits by about one order of magnitude. Recent studies have demonstrated that a reconstruction of momentum and energy of GeV particles is well feasible in liquid scintillator. Monte Carlo studies on the reconstruction of the complex event topologies found for neutrino interactions at multi-GeV energies have shown promising results. If this is confirmed, LENA might serve as far detector in a long-baseline neutrino oscillation experiment currently investigated in LAGUNA-LBNO.3