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SUMMARY:Fast Reactive Brownian Dynamics - Aleksandar Donev (New York Unive
 rsity)
DTSTART:20160621T080000Z
DTEND:20160621T084500Z
UID:TALK66529@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:I will describe a particle-based algorithm for reaction-diffus
 ion problems  that combines Brownian dynamics with a Markov reaction proce
 ss. The microscopic  model simulated by our Split Reactive Brownian Dynami
 cs (SRBD) algorithm is  based on the Doi or volume-reactivity model. This 
 model applies only to  reactions with at most two reactants\, which is phy
 sically realistic. Let us  consider the simple reaction A+B->product. In t
 he Doi model\, particles are  independent spherical Brownian walkers (this
  can be relaxed to account for  hydrodynamic interactions)\, and while an 
 A and a B particle overlap\, there is a  Poisson process with a given micr
 oscopic reaction rate for the two particles to  react and give a product. 
 Our goal is to simulate this complex Markov process in  dense systems of m
 any particles\, in the presence of multiple reaction channels.  <br> <br>O
 ur algorithm is inspired by the Isotropic Direct Simulation Monte Carlo  (
 I-DSMC) method and the next subvolume method. Strang splitting is used to 
  separate diffusion and reaction\; this is the only approximation made in 
 our  method. In order to process reactions without approximations\, with t
 he particles  frozen in place\, we use an event-driven algorithm. We divid
 e the system into a  grid of cells such that only particles in neighboring
  cells can react. Each cell  schedules the next potential reaction to happ
 en involving a particle in that  cell and a particle in one of the neighbo
 ring cells\, and an event queue is used  to select the next cell in which 
 a reaction may happen. <br> <span><br>Note that\, while a grid of cells is
  used to make the algorithm efficient\, the  results obtained by the SRBD 
 method are grid-independent and thus free of grid  artifacts\, such as los
 s of Galilean invariance and sensitivity of the results to  the grid spaci
 ng. I will compare our SRBD method with grid-based methods\, such  as (C)R
 DME and a variant of RDME that we call Split Brownian Dynamics with  React
 ion Master Equation (S-BD-RME)\, on a problem involving the spontaneous  f
 </span>
LOCATION:Seminar Room 1\, Newton Institute
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