Conference

We compute the partition function of quantum Einstein gravity in three dimensional de Sitter space. The Euclidean path integral is formulated as a sum over geometries, including both perturbative loop and non-perturbative instanton corrections coming from geometries with non-trivial topology. These non-trivial geometries have a natural physical interpretation and lead to deviations from the standard thermal behaviour of the de Sitter horizon; this is the de Sitter analog of the celebrated "black hole Farey tail." Perturbative quantum corrections are computed to all orders in perturbation theory and the vacuum partition function, including all instanton and perturbative corrections, is shown to diverge in a way which can not be regulated using standard field theory techniques. Thus the Hartle-Hawking state is not normalizable.

For approximately half a century, core-collapse supernovae have posed a vexing puzzle for theorists despite being a major ingredient (and uncertainty) in fields ranging from stellar and galaxy evolution to the interstellar medium. Historically, advances in core-collapse theory have been linked to advances in computing power and software. Supernovae are inherently multi-dimensional objects in which neutrino transport, gravity, hydrodynamic instabilities and convection play important roles. Three-dimensional simulations incorporating sufficient physical fidelity require extensive high-performance computing resources and codes efficient enough to use the associated architecture. In this talk, I will highlight recent advances in the field. In particular, I will discuss the dependence of spatial dimension on the viability of the neutrino mechanism and the origin of pulsar kicks.

Recent multidimensional supernova simulations seem to support an assumption that the neutrino-driven mechanism might work to blow up massive stars. However the explosion energies obtained in those simulations are usually not enough to account for the canonical explosion energy of 10^51 ergs. In this contribution we'd like to address whether some new physical elements so far ignored in the supernova simulations would or would not have an impact on the neutrino-heating mechanism such as the effects of neutrino self-interactions nuclear burning and the turbulent heatingdue to the magneto-rotational instability. These effects are included in our 2D simulations with the spectral neutrino transport (Suwa et al. (2010)).In addition we will report our 3D results based on the 3D version of the code and discuss their potential impacts on the explosion mechanism. Based on these results we will compute the gravitational radiation and neutrinoemission and then discuss some prospects towards multi-messenger astronomyof supernova explosions.

We explore the duality, conjectured in earlier work, between the wave function of the multiverse and a 3D Euclidean field theory on the future boundary of spacetime. We propose that a measure for the multiverse, which is needed in order to extract quantitative probabilistic predictions, can be derived in terms of the boundary theory by imposing a UV cutoff. In the inflationary bulk, this measure corresponds to a cutoff at surfaces of constant comoving apparent horizon.

The inner crust of neutron stars has a remarkable property that it is crystalline as well as superfluid. I will describe the low energy theory of systems with this property in general, and describe how to relate the low energy constants of the theory to derivatives of the free energy with respect to lattice shape and chemical potentials. As an application, I will discuss the mixing of lattice and superfluid modes in the neutron star inner crust.