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Posts by Colin Rice

1) Message boards : News : New Nbody Run (Message 54259)
Posted 30 Apr 2012 by Colin Rice
Sorry for not paying a lot of attention to this thread. I didn't realize people could comment on the news items.

John Black:
A Couple of these runs have been bad due to me messing up parameters etc... I test them once they get on the server and pull the run if I messed up and need to republish it.

Robert Gammon:
These runs are unpredictable. Its a very hard problem to predict the run times so we are very generous so they don't time out. We also are using 100,000 particles to deal with the chaotic motion.

We had a nbody generation bug with the nbody runs. It should be fixed.
2) Message boards : News : New Nbody Run (Message 53981)
Posted 11 Apr 2012 by Colin Rice
A new NBody run has been posted. We are trying to determine the initial dark matter distribution of some test data. There have been some improvements to our model which should hopefully result in faster convergence times. The run is titled nbody_100K_Plum_EMD. All previous Nbody runs have been taken down.
3) Message boards : MilkyWay@home Science : Nbody Science (Message 51309)
Posted 6 Oct 2011 by Colin Rice

I'm Colin Rice an undergraduate at RPI who has been working with mw@home for about a semester now. I'm posting to give a little insight into the nbody simulations which I recently took over.

A N-Body simulation is a simulation where you are using multiple small bodies and applying forces between them to simulate some sort of physical system. In our case we are simulating a dwarf galaxy orbiting the milkyway.

We are currently investigating the makeup of dark matter within dwarf galaxies. Due to inconsistent angular velocities we think there may be dark matter inside of dwarf galaxies. However it is not conclusively proven.

Our goal is to determine if dark matter inside of a dwarf galaxy causes a distinctive orbit when the galaxy is then pulled into an orbit about the milkyway. We are doing this in two steps.

1)We are currently running simulations to see if the N-Body system can recover the initial parameters of a dwarf galaxy which we generated with dark and light matter, and then evolved in time.

Specifically, when an nbody runs the server has generated a trial set of parameters and is evolving them to see if they match the observed histogram. It then evaluates how well they worked and creates new runs based on the current runs fitness. It only evaluates the fitness based on the light matter. However, it used both light and dark matter when running the simulation. This is done because we can only see the light matter in real world data and that is what this system is designed to process.

2) The next step after we confirm that the technique works via test runs is to put real world data into the simulation and see if we can figure out the initial parameters for the dark matter inside the dwarf galaxies. We can't just plug in the initial data because we are unsure as to whether the system works.

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