The most promising astrophysical sources of kHz gravitational waves (GWs) are the inspiral and merger of binary neutron star(NS)/black hole systems. Maximizing the scientific return of a GW detection will require identifying a coincident electromagnetic (EM) counterpart. One of the most likely sources of isotropic EM emission from compact object mergers is a supernova‐like transient powered by the radioactive decay of heavy elements synthesized in ejecta from the merger. We present the first calculations of the optical transients from compact object mergers that self‐consistently determine the radioactive heating by means of a nuclear reaction network; using this heating rate, we model the light curve with a one‐dimensional Monte Carlo radiation transfer calculation. For an ejecta mass ∼10−2 M⊙ (10−3 M⊙) the resulting light‐curve peaks on a time‐scale ∼1 d at a V‐band luminosity νLν∼ 3 × 1041 (1041) erg s−1[MV=−15(−14)]; this corresponds to an effective ‘f’ parameter ∼3 × 10−6 in the Li–Paczynski toy model. We argue that these results are relatively insensitive to uncertainties in the relevant nuclear physics and to the precise early‐time dynamics and ejecta composition. Since NS merger transients peak at a luminosity that is a factor of ∼103 higher than a typical nova, we propose naming these events ‘kilo‐novae’. Because of the rapid evolution and low luminosity of NS merger transients, EM counterpart searches triggered by GW detections will require close collaboration between the GW and astronomical communities. NS merger transients may also be detectable following a short‐duration gamma‐ray burst or ‘blindly’ with present or upcoming optical transient surveys. Because the emission produced by NS merger ejecta is powered by the formation of rare r‐process elements, current optical transient surveys can directly constrain the unknown origin of the heaviest elements in the Universe.

We present a new nucleosynthesis process that we denote as the nu p process, which occurs in supernovae (and possibly gamma-ray bursts) when strong neutrino fluxes create proton-rich ejecta. In this process, antineutrino absorptions in the proton-rich environment produce neutrons that are immediately captured by neutron-deficient nuclei. This allows for the nucleosynthesis of nuclei with mass numbers A>64, , making this process a possible candidate to explain the origin of the solar abundances of (92,94)Mo and (96,98)Ru. This process also offers a natural explanation for the large abundance of Sr seen in a hyper-metal-poor star.

In one dimension, the study of magnetism dates back to the dawn of quantum mechanics when Bethe solved the famous Heisenberg model that describes quantum behaviour in magnetic systems. In the last decade, one-dimensional (1D) systems have become a forefront area of research driven by the realization of the Tonks-Girardeau gas using cold atomic gases. Here we prove that 1D fermionic and bosonic systems with strong short-range interactions are solvable in arbitrary confining geometries by introducing a new energy-functional technique and obtaining the full spectrum of energies and eigenstates. As a first application, we calculate spatial correlations and show how both ferro-and antiferromagnetic states are present already for small system sizes that are prepared and studied in current experiments. Our work demonstrates the enormous potential for quantum manipulation of magnetic correlations at the microscopic scale.

With presently known input physics and computer simulations in 1D, a self-consistent treatment of core collapse supernovae does not yet lead to successful explosions, while 2D models show some promise. Thus, there are strong indications that the delayed neutrino mechanism works combined with a multi-D convection treatment for unstable layers (possibly with the aid of rotation, magnetic fields and/or still existent uncertainties in neutrino opacities). On the other hand there is a need to provide correct nucleosynthesis abundances for the progressing field of galactic evolution and observations of low metallicity stars. The innermost ejecta is directly affected by the explosion mechanism, i.e. most strongly the yields of Fe-group nuclei for which an induced piston or thermal bomb treatment will not provide the correct yields because the effect of neutrino interactions is not included. We apply parameterized variations to the neutrino scattering cross sections in order to mimic in 1D the possible increase of neutrino luminosities caused by uncertainties in proto-neutron star convection. Alternatively, parameterized variations are applied to the neutrino absorption cross sections on nucleons in the "gain region" to mimic the increase in neutrino energy deposition enabled by convective turnover. We find that both measures lead to similar results, causing explosions and a Y e > 0.5 in the innermost ejected layers, due to the combined effect of a short weak interaction time scale and a negligible electron degeneracy, unveiling the proton-neutron mass difference. We include all weak interactions (electron and positron capture, beta-decay, neutrino and antineutrino capture on nuclei, and neutrino and antineutrino capture on nucleons) and present first nucleosynthesis results for these innermost ejected layers to discuss how they improve predictions for Fe-group nuclei. The proton-rich environment results in enhanced abundances of 45 Sc, 49 Ti, and 64 Zn as requested by chemical evolution studies and observations of low metallicity stars as well as appreciable production of nuclei in the mass range up to A = 80.

We study the quench dynamics of a two-component ultracold Fermi gas from the weak into the strong interaction regime, where the short time dynamics are governed by the exponential growth rate of unstable collective modes. We obtain an effective interaction that takes into account both Pauli blocking and the energy dependence of the scattering amplitude near a Feshbach resonance. Using this interaction we analyze the competing instabilities towards Stoner ferromagnetism and pairing.Ferromagnetism in itinerant Fermions is a prime example of a strongly interacting system. Most theoretical treatments rely on a mean-field Stoner criterion [1], but whether this argument applies beyond mean-field remains an open problem. It is known that the existence of the Stoner instability is very sensitive to the details of band structure and interactions [2][3][4], however how to account for these details in realistic systems remains poorly understood. Exploring the Stoner instability with ultracold atoms has recently attracted considerable attention. Following theoretical proposals [5], the MIT group made use of the tunability [6] and slow time scales [7-10] of ultracold atom systems to study the Stoner instability [11]. Signatures compatible with ferromagnetism, as understood from mean-field theory [12], were observed in experiments: a maximum in cloud size, a minimum in kinetic energy and a maximum in atomic losses at the transition. However, no magnetic domains were resolved.An important aspect of the MIT experiments is that they were done dynamically: the Fermi gas was originally prepared with weak interactions and then the interactions were ramped to the strongly (repulsive) regime. Dynamic rather than adiabatic preparation was used in order to avoid production of molecules. This raises the question of what are the dominant instabilities of the Fermi gas in the vicinity of a Feshbach resonance.Naively, one would expect that on the BEC-side, molecule production is slow, as it requires a three-body process. Therefore, instability towards Stoner ferromagnetism would dominate over the instability toward molecule production. In this picture, one would expect that quenches to the attractive (BCS) regime always yield an instability towards pairing, whereas quenches to the repulsive (BEC) regime an instability towards ferromagnetism for sufficiently strong interactions.In this Letter, we argue that this picture, which was used to interpret the MIT experiments, is incomplete. Near the Feshbach resonance, even on the BEC side, pair production remains a fast two-body process as long as the Fermi sea can absorb the molecular binding energy. As a result, near the Feshbach resonance, both on the BEC and the BCS side, the pairing and the Stoner instabilities compete directly. We now