13,789 research outputs found
Accurate and efficient splitting methods for dissipative particle dynamics
We study numerical methods for dissipative particle dynamics (DPD), which is
a system of stochastic differential equations and a popular stochastic
momentum-conserving thermostat for simulating complex hydrodynamic behavior at
mesoscales. We propose a new splitting method that is able to substantially
improve the accuracy and efficiency of DPD simulations in a wide range of the
friction coefficients, particularly in the extremely large friction limit that
corresponds to a fluid-like Schmidt number, a key issue in DPD. Various
numerical experiments on both equilibrium and transport properties are
performed to demonstrate the superiority of the newly proposed method over
popular alternative schemes in the literature
Efficient numerical integrators for stochastic models
The efficient simulation of models defined in terms of stochastic
differential equations (SDEs) depends critically on an efficient integration
scheme. In this article, we investigate under which conditions the integration
schemes for general SDEs can be derived using the Trotter expansion. It follows
that, in the stochastic case, some care is required in splitting the stochastic
generator. We test the Trotter integrators on an energy-conserving Brownian
model and derive a new numerical scheme for dissipative particle dynamics. We
find that the stochastic Trotter scheme provides a mathematically correct and
easy-to-use method which should find wide applicability.Comment: v
How would you integrate the equations of motion in dissipative particle dynamics simulations?
In this work we assess the quality and performance of several novel
dissipative particle dynamics integration schemes that have not previously been
tested independently. Based on a thorough comparison we identify the respective
methods of Lowe and Shardlow as particularly promising candidates for future
studies of large-scale properties of soft matter systems
Trotter Derivation of Algorithms for Brownian and Dissipative Particle Dynamics
This paper focuses on the temporal discretization of the Langevin dynamics,
and on different resulting numerical integration schemes. Using a method based
on the exponentiation of time dependent operators, we carefully derive a
numerical scheme for the Langevin dynamics, that we found equivalent to the
proposal of Ermak, and not simply to the stochastic version of the
velocity-Verlet algorithm. However, we checked on numerical simulations that
both algorithms give similar results, and share the same ``weak order two''
accuracy. We then apply the same strategy to derive and test two numerical
schemes for the dissipative particle dynamics (DPD). The first one of them was
found to compare well, in terms of speed and accuracy, with the best currently
available algorithms.Comment: to be published in J.Chem.Phy
Warm Inflation in the Adiabatic Regime- a Model, an Existence Proof for Inflationary Dynamics in Quantum Field Theory
Warm inflation is examined in a multi-field model. Solutions are obtained for
expansion e-folds and scalar density perturbations. Nonequilibrium dynamics is
restricted to a regime that is displaced only slightly from thermal equilibrium
and in which all macroscopic motion is adiabatic. In such a regime,
nonequilibrium dynamics is well defined, provided macroscopic motions that
displace the thermal equilibrium state occur sufficiently slow. The solution
has adjustable parameters that permit observational consistency with respect to
expansion e-folds and density perturbations in the full adiabatic regime, thus
insuring a valid solution regime. For particle physics, the model is
nonstandard since it requires a large number of fields, . A particle
physics/string interpretation of the model and solutions is discussed, which
can accommodate the large field number requirement.Comment: 49 pages, 1 figure, Latex, minor corrections, In Press Nuclear
Physics B 200
Decoherence in resonantly driven bistable systems
We study dissipative tunneling in a double well potential that is driven
close to a resonance between the lowest tunnel doublet and a singlet. While the
coherent dynamics can be described well within a three-level approximation,
dissipative transitions to levels outside the singlet and the doublet may play
a crucial role. Moreover, such transitions can enhance the entropy production
significantly.Comment: 12 pages, 7 figures, vch-book.cl
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