# Presentation: 161407

## F. Douglas Swesty & Eric S. Myra

Terascale Supernova Initiative
&
Department of Physics & Astronomy
STATE UNIVERSITY OF NY @ STONY BROOK

- TERASCALE SUPERNOVA INITIATIVE

- F. Douglas Swesty & Eric S. Myra
- Terascale Supernova Initiative
- &
- Department of Physics & Astronomy
- STATE UNIVERSITY OF NY @ STONY BROOK

## Stellar Core Collapse

_***Stellar Core Collapse***_
**  ****-****Massive stars evolve by burning lighter **
**Elements, by thermonuclear fusion, **
**into heavier elements**
**-High mass stars will produce elements**
**Up to Silicon & Sulfur , which then **
**burn into Iron**
**-Star has an Onionskin-like structure**
**With layers of successively heavier**
**elements**
**-Each burning stage progresses**
**More rapidly **
**-When the Iron core mass becomes**
**about 1.2-1.4 solar masses the core**
**can no longer sustain itself against **
**the  pull of gravity & it collapses**

## Core Collapse & Bounce

_***Core Collapse & Bounce***_
**  ****-Iron core collapses in 1/100****th**** of a second**
**Neutrinos are produced: e****-**** + p ******** n + ********e**
**-Neutrinos escape from the collapsing**
**core until the material becomes too**
**dense**
**-The core collapses until densities**
**of about 2.5 x 10****14**** g/cm****3**** is reached**
**-Nuclear forces cause the collapse**
**to halt and the core rebounds outward**
**-Outward moving core forms a shock wave**
**when it hits the exterior regions where**
**matter is still falling inward **

## Convection in Core-Collapse Supernovae:How convection complicates the picture

*****e, *************

## Neutrino Radiation-Hydrodynamic Model

## Parallel Implementation

**Global Problem Domain**

**Problem split up into**
**one spatial sub-domain **
**per processor**

**Adjacent **
**processes in**
**Cartesian **
**topology must**
**exchange **
**ghost zones**
**when needed**
** ****by algorithms**

- Code (V2D) written in F95
- Continuous process of Verification & Validation
- Componentized architecture
- Message passing done in MPI
- Parallel I/O done with parallel HDF5
- Scalable to at least 1024-2048 processors for “medium sized” problems

## Implicit Neutrino Transport  w/ Newton-Krylov Iteration

**via Newton-BiCGSTAB **
**Currently using sparse parallel **
**approximate inverse preconditioning **
**(physics based) -- highly parallel**
**MATVECS can be carried out**
**asynchronously to hide **
**communication **
**BiCGSTAB can be restructured**
**to reduce global reductions**
**Typically 10-20 Bicgstab iterations**
** ****per Newton iteration; 2-3 Newton**
**iterations**
**Implicit solvers have to be ultra-fast**
**    ****-- few x 10****5 ****timesteps to complete**
**        ****simulation!**
**Currently Incorporating TOPS **
**SUNDIALS solvers into V2D for fully **
**implicit radiation-hydro**

_***Implicit Neutrino Transport  w/ Newton-Krylov Iteration***_

## Data Management & Networking Challenges

_***NERSC***_

_***Stony Brook***_

_***Chicago***_

_***32AoA***_

_***Sunnyvale***_

***75 msec***

- Couldn’t handle the data with LBONE Depots & LORS Tools!
- Scientific Process Automation (SPA) systems is easing workflow management tremendously!

## Models of the Convective Epoch

** ****-S15S7B progenitor model of**
**Woosley & Weaver**
**-Neutrino Physics at the level**
**of Bruenn (1985) w/ NES turned off**
**EOS is LS K=180 MeV model **
**-Collapse run to ********=10****14 ****g/cm****3 ****w/**
**1-D Lagrangean code**
**-Baseline model does not**
**explode on timescales of 35 msec**

_***Models of the Convective Epoch***_

- Prior to SciDAC state of the art was:
- 2-D models with gray transport approximation  (produced explosions; assumed distribution function;  approximated rates & opacities; no dynamic diffusion in Eulerian models)
- Uncoupled radial-ray multi-group models (saw no explosions; lacked full coupling; no lateral movement of neutrinos; no dynamic diffusion)
- SciDAC has enabled:
- Fully coupled 2-D radiation-hydrodynamic MGFLD models
- Fully coupled 2-D Boltzmann transport models (coming soon!)

##  Behavior of Baseline Model

** **_**Behavior of Baseline Model**_
** ****Shock stagnates on timescales of 30 msec**
** ****Shock is strong; flow into it  @ Mach 4 **
**  **
** ****Shock initially shows large scale SASI mode which **
**      ****dies out & shock circularizes**
** ****Could this reinitialize at later times?**
** ****We see convection in both:**
** ****The proto-neutron star (in optically thick regions **
**      ****below the neutrinosphere)**
** ****Between stalled shock & neutrinosphere**
** ****Vigorous Proto-Neutron Star convection is entropy **
**     ****driven and is short-lived**
** ****Convection above the neutrinosphere maintains**
**     ****and is fueled by neutrino heating of base of **
**     ****the layer**

##  PNS convection

** ****PNS convection gives rise to a **
**    ****fast burst of  deleptonization **
** ****PNS instability is initiated and **
**    ****driven by an unstable entropy **
**    ****gradient around neutrinosphere **
**  **
** ****Higher Ye (~0.3) material gets **
**    ****advected  upward allowing it to **
**    ****deleptonize around neutrinosphere**
** ****PNS convection enhances **
**    ****neutrino luminosity in a burst **
**    ****but does not maintain this **
**    ****enhancement**
** ****Dynamic diffusion term ****r¢****(E******** v)  **
**    ****(which has  always been neglected) **
**      ****is the leading order term of **
**      ****neutrino transport equation **
**      ****inside of  30 Km!**

_***The Future***_

- We now have a computational laboratory to explore effects
-           on nuclear and particle physics in convective epoch of supernovae
- Currently starting to look at effects of nuclear force parameters such as the nuclear symmetry energy, nuclear specific heat & effective masses
- Effects of neutrino electron scattering and other neutrino physics
- NES models are coming very soon!
- Will be looking at neutrino flavor mixing
- Other progenitor models
- Will be extending simulations to later times
-  Can the SASI occur in baseline model at later times?
- Fully implicit hydro is in development and testing
- Will allow us to solve technical limitations in looking at PNS convection
- Will enable us to calculate neutrino signal
- Fully implicit radiation-hydro
- Eliminate operator splitting and allow higher-order time integration
- 3-D Models with AMR
- Accurately characterize convection
- Will be able to deal with rotation
- Additional goal: estimate gravitational wave signal

## The Stony Brook TSI web site:http://nuclear.astro.sunysb.edu

_***Thanks to those who have contributed! ***_

- TSI Team members:
- Ed Bachta, Polly Baker (Indiana Univ. @ Indianapolis)
- Dennis Smolarski (Santa Clara Univ.)
- Jim Lattimer (Stony Brook)
- TOPS ISIC Team members:
- Dan Reynolds, Carol Woodward (LLNL)
- SDM ISIC Team members:
- Terrence Critchlow, Xiaowen Xin (LLNL)
- LBONE/LORS SAPP Team members:
- Micah Beck, Scott Atchley, Hunter Hagwood (Univ. of Tenn.)
- CCA ISIC Team Members:
- Rob Armstrong (SNL), Gary Kumfert (LLNL), David Bernholdt (ORNL)
- APDEC ISIC Team Members:
- Donna Calhoun (Univ. of Washington)
- NERSC Staff:
- Francesca Verdier, Wes Bethel, Richard Gerber, David Skinner, John Shalf, Eli Dart, Brent Draney