Particle Physics

Massive accretion disks may form from the merger of neutron star (NS)-NS or black hole-NS binaries, or following the accretion-induced collapse (AIC) of a white dwarf. These disks, termed `hyper-accreting' due to their accretion rates up to several solar masses per second, may power the relativistic jets responsible for short duration gamma-ray bursts. Using 1D time-dependent calculations of hyper-accreting disks, I show that a generic consequence of the disk's late-time evolution is the development of a powerful outflow, powered by viscous heating and the recombination of free nuclei into Helium. These outflows - in additional to any material dynamically-ejected during the merger - synthesize heavy radioactive elements as they expand into space. Nuclear heating from the r-process is not yet incorporated in merger simulations, yet has important consequences both for the dynamics of late `fall-back' accretion and in powering a supernova-like transient (`kilonova') 1 day following the merger or AIC.

The energy generated by the r-process can impact the dynamics of neutron star mergers. Solving a full r-process network coupled with the hydrodynamics becomes the necessary but it is computational very expensive. We have developed a simple model that can be implemented into hydrodynamic simulations and gives a very good estimate of the r-process heating.

A stalled core-collapse supernova shock is unstable to non-spherical perturbations, in what is known as the Standing Accretion Shock Instability (SASI). This instability is global and oscillatory, affecting the region between the protoneutron star surface and the shock. I'll discuss several insights into this instability obtained by combining linear stability analysis and time-dependent simulations, using simple prescriptions for the microphysics that capture the essential physics of the problem.

I would like to overview the progress of the EOS tables for core-collapse supernovae and their influence clarified by these EOS developments. Some topics I try to cover include the neutrino signal from the black hole formation as well as the composition in supernova cores. We would to like hear needs and comments from users of the series of Shen EOS tables for further developments. I would like to report also on recent development of our numerical code of the neutrino-transfer calculation in 3D.

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.

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.