ET Workshop Spring 2011

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Welcome to the Einstein Toolkit Spring workshop

This workshop is focussed on improving the hydrodynamics of the ET: GRHydro.


Tue 04/26

14:00 - 17:00 First Session

- Welcome, introductions (lead: Ott)
- Setting goals for the workshop (lead: Ott)
- Status of the EinsteinToolkit and the EinsteinToolkit paper (lead: Loeffler)
- Status of the CIGR project (discussion, lead: Schnetter, Ott)
- Goals for ET and CIGR in the next 3 months
- Status report: MHD (Faber, Mundim)
- Status report: Microphysics and EOS (Ott)
- Status report: Refluxing (Schnetter)
- Status report: BHNS initial data project (Haas, Loeffler, Mundim, Bode)
- Status of other projects within CIGR/ET (anybody doing anything related)

Wed 04/27

09:00 - 12:00 Hands on coding/testing 1 (TBD)

14:00 - 15:00 An overview of the Caltech-Cornell-CITA-WSU code SpEC (Szylagyi)

15:00 - 17:00 Hands on coding/testing 2 (TBD)

19:00 Workshop dinner (TBD)

Thu 04/28

09:00 - 12:00 Hands on coding/testing 3 (TBD)

14:00 - 15:00 2 30 min Science talks (practice for APS? TBD)

15:00 - 17:00 Hands on coding/testing 4 (TBD)

Fri 04/29

09:00 - 11:00 Hands on coding/testing 5 (TBD)

11:00 - 11:30 Closing discussion (lead: Ott)

Location in Space and Time

The ET Spring workshop will be held from Tue, 04/26/11 (morning; official start 2pm afternoon) - Fri, 04/29/11 (morning) at the Cahill Center for Astronomy and Astrophysics at Caltech and is organized by TAPIR. The meeting will be in room Cahill 273.


Please send an email to for registration.


You are responsible for arranging your accommodation. We recommend the Saga Motor Hotel or the Vagabond Inn, which are both within walking distance to Caltech. Please request the special Caltech rate. This cannot be done online and must be booked by calling.

Saga Motor Hotel
1635 E Colorado Blvd, Pasadena, CA 91106
Phone: 626-795-0431
Caltech rate: $77+tax (single occupancy)
Vagabond Inn
1203 E. Colorado Blvd, Pasadena, CA 91106
Phone: 626-449-3170
Caltech rate: $79+tax (1-2 people)

From LAX to Pasadena

There are many possible ways of getting from the airport to Pasadena:

- Taxi (~$100)
- Super Shuttle (~$40)
- FlyAway Bus + Metro Gold Line (~$9 in total)

At any terminal at LAX, you will find departure platforms for all of the above transportation systems just outside the terminals.

The FlyAway Bus + Metro is usually very convenient. To get on it, just wait by the blue sign that says "FlyAway Busses". Wait until a FlyAway Bus with sign "Union Station" arrives (it departs every ~30min). Jump on it and go until Union Station (its only and final destination). You pay $7 upon arrival (they have change if you don't exactly have $7). At Union Station, go to the platform that says "Metro Gold Line". Pay $1.50 at the ticket machine (one way ticket). Take the Metro Gold Line (direction "Sierra Madre Station") and exit at "Lake Station" or "Allen Station" (best for the Saga Motor Hotel). Check out google maps for further info. Here's a link to Metro Gold Line, including a link to this trip planer (it also knows about FlyAway busses).

Additional Information

There will be coffee & pastries in the morning and afternoon. Unfortunately, we will not be able to provide or pay for lunch/dinner.

Suggested close by restaurants

Bar: Lucky Baldwins

Restaurants: Malbec

List of participants

Frank Loeffler
Roland Haas
Jose Manuel Torres Chavez
Maria C. Babiuc-Hamilton
Erik Schnetter
Bruno Coutinho Mundim
Tanja Bode
Joshua Faber
Evan O'Connor
Christian Ott
Peter Kalmus
Christian Reisswig
Ernazar Abdikamalov
Bela Szilagyi
Peter Diener

Progress reports

-Refluxing and regridding should now work together. The corresponding bug in thorn LSUDevelopment/Refluxing should be corrected.
-We plan to move thorn LSUDevelopment/Refluxing to LSUThorns/Refluxing, where it will be publicly available.
-Christian Reisswig is working on higher-order cell-centred ENO operators that will improve accuracy for hydro evolutions.
-The Mercurial version of Carpet is now (is it?) the default version of Carpet that is available with the development version of the Einstein Toolkit. Frank Löffler configured the Mercurial server to allow public read-only access to the repository.
-Peter Diener designed and implemented an improved load balancing mechanism for Carpet that should be able to provide better load balancing, in particular if the domain is "uneven", i.e. if there are multiple unequal-sized patches, or if the number of processes is not a cube. This mechanism is now attached to Carpet and ready for testing.

- The MHD working group (primarily Bruno, Roland, Tanja, and Josh) worked on the following tasks:
1.) We've added a new gridfunction, "Bcons" to GRHydro, to represent the conserved, densitized magnetic field vector, which is related to the primitive undensitized variable HydroBase::Bvec by the relation Bcons = sqrt(gamma) Bvec. Besides modifying Con2Prim and Prim2Con to account for the change, we also modified the fluxes to use the conserved B-field throughout and modified the /RHS calculation to evolve the conserved version.
2.) We've modified the hyperbolic divergence cleaning formalism to bring it into a proper general relativistic form. The new format represents an explicit d'Alembertian wave equation with a damping term, and diagonal shocktube runs indeed show the numerical divergence shrinking as a wave travels at the speed of light away from the shock front..
3.) We've redone several tests, including Prim->Con->Prim and vice versa, and shocktubes, finding that the code reproduces its prior behavior in flat space simulations, as it should. 4.) Methods for handling completely general equations of state in the Con->Prim conversion were discussed, and the initial coding steps have been written to serve as a template for the eventual production code. The methodology has been completely derived, and it is now a matter of implementing it into the code itself and checking it against non-trivial EOS to ensure that the proper results are generated. This will likely happen in the next month or thereabouts.