
	Scott C. Noble Associate Research Scientist

Scott C. Noble

Associate Research Scientist


Info.
Affiliation:	Center for Computational Relativity and Gravitation School of Mathematical Sciences College of Science Rochester Institute of Technology
Office:	78-1025
Office Phone:	(585) 475-5879
Fax:	(585) 475-7340
Homepage:	http://ccrg.rit.edu/~scn/
Old Homepage:	http://www.pha.jhu.edu/~scn/
Email:
Mailing Address:	Center for Computational Relativity and Gravitation School of Mathematical Sciences Rochester Institute of Technology 78 Lomb Memorial Drive Rochester, New York 14623, USA

Research:

(Note: topic descriptions are presented in reverse chronological order)

Julian Krolik, John Hawley, and I advanced our work on geometrically thin accretion disk simulation in this paper, where we focus on disks with a variety of thickness, resolutions and field topologies around a non-spinning or Schwarzschild black hole. We find that the time-averaged radial dependence of fluid-frame electromagnetic stress is almost completely independent of both disk thickness and poloidal magnetic topology. It rises smoothly inward at all radii (exhibiting no feature associated with the innermost stable circular orbit, ISCO) until just outside the event horizon, where the stress plummets to zero. Reynolds stress can also be significant near the ISCO and in the plunging region; the magnitude of this stress, however, depends on both disk thickness and magnetic topology. The two stresses combine to make the net angular momentum accreted per unit rest mass 7%-15% less than the angular momentum of the ISCO.
With Julian Krolik at JHU I investigated the temporal variability of coronal emission predicted from our cooling losses of our thin disk run around a black hole with spin parameter a=0.9M (see the following paragraph). We found that GRMHD turbulence can explain the observed power spectrum of fluctuations seen in the X-ray spectra of AGN and the hard state of galactic black holes.
At Johns Hopkins with Julian Krolik and John Hawley, I embarked on a campaign to understand geometrically thin accretion disks. The principle goal is to see what (if any) differences arise from classic theoretical models (such as Novikov & Thorne's) as one tunes the disk thickness to zero. The first task was to develop a 3D GRMHD code using modern high-resolution shock capturing methods that was flux conservative so that all dissipated energy would be captured unlike previous 3D codes at that time. We call this code HARM3D, which---the name suggests---is written based on the 2D HARM code. In addition to adding another dimension to the code, we also implemented piecewise parabolic (or PPM) reconstruction methods for the primitive variables at the cell faces and electric field at the cell edges (for the constraint transport method), improved the stability of the code in the magnetically dominated funnel region. Since we use a flux conservative algorithm that conserves total energy and a cooling function appropriate for relativistic flows, we are able to record in space and time the bolometric luminosity (or emissivity) radiated over the disk necessary to maintain the constant disk scale height. The emissivity then provides us with a means of predicting the luminosity observed at infinity using a new general relativistic ray-tracing code I wrote based on the one I helped write at UIUC. Our first paper on the subject, available here was the first calculation of a (cooled) thin disk's bolometric luminosity at infinity using 3D GRMHD simulations. We found that for our particular configuration (black hole spin of a=0.9M, H/R = 0.1) that there was a 6% increase in radiative efficiency over Novikov & Thorne's model and general shift of the inner radiative edge of the disk by 20%. These changes will likely be important when extracting the black hole spin parameter from observations of thermal spectra.
With Charles Gammie, Po Kin Leung and Laura Book of the Center for Theoretical Astrophysics at UIUC, I developed (nearly) self-consistent models of Sagittarius A* (Sgr A*), which is the supermassive black hole at the center of our galaxy. Please see our paper that is published in a special volume of Classical and Quantum Gravity (CQG) CQG for the New Frontiers in Numerical Relativity Conference at AEI. The picture at the top-left of this page is a plot of the logarithm of the intensity of light at 1mm calculated from our Sgr A* model using a three-dimensional snapshot of magnetohydrodynamic accretion in general relativity.
With Charles Gammie, Jon McKinney, and Luca Del Zanna, I improved the method for calculating the primitive variables from the conserved variables in general relativistic MHD equations. I continue to work on improving the stability and accuracy of HARM, our GRMHD code. Please see this paper about this work. One may obtain copies of these methods under the GPL from Gammie's Code page.
I completed the public release of the code HARM. The code is used to solve the magnetohydrodyanmic (MHD) equations in curved, stationary spacetimes. In other words, the code is used primarily to simulate non-resistive, non-viscous plasmas around black holes. One may obtain a version of this code under the GPL from Gammie's Code page.
In addition, I have also accomplished research in numerical relativity, general relativistic critical phenomena, nuclear physics, high-energy physics and quantum computation. Further information regarding my past and present research activities may be posted here at a future date.
CV : [PS] [PDF] [HTML]
Papers.
Movies.
Presentations.
Posters.

Links:


RIT Info:	Astro Group, Journal Club, Physics, CIS, CIS Computing, XiRel, ET, Campus Map [PDF], RIT Calendar, COS Calendar,
JHU Info (former location):	PHA Weekly Calendar, STScI, Library, JHU Calendar, PHA.JHU Computing, Homewood HPC Cluster,
UIUC Info (former location):	Physics Colloquium, Astronomy Dept., Astronomy Colloquium, Library.
PhD Work	Matt Choptuik (my PhD advisor), his group, UBC Physics,
Journals,Papers,Abstracts,...	ADS Search, ADS Scanned, Arxiv.org, SPIRES, ApJ, PROLA, A&A, MNRAS, CQG,
My Alma Maters:	Caltech (BS, 1997), UT-Austin (PhD 2003), UBC (visiting 2000-3),
Jobs	APS Jobs , AAS Jobs , Physics Today Jobs , Rumor Mill ,
Misc.	GMAIL , APS , AAS , Google Chart ,