100,873 research outputs found
Mapping of dissipative particle dynamics in fluctuating hydrodynamics simulations
Dissipative particle dynamics (DPD) is a novel particle method for mesoscale
modeling of complex fluids. DPD particles are often thought to represent
packets of real atoms, and the physical scale probed in DPD models are
determined by the mapping of DPD variables to the corresponding physical
quantities. However, the non-uniqueness of such mapping has led to difficulties
in setting up simulations to mimic real systems and in interpreting results.
For modeling transport phenomena where thermal fluctuations are important
(e.g., fluctuating hydrodynamics), an area particularly suited for DPD method,
we propose that DPD fluid particles should be viewed as only 1) to provide a
medium in which the momentum and energy are transferred according to the
hydrodynamic laws and 2) to provide objects immersed in the DPD fluids the
proper random "kicks" such that these objects exhibit correct fluctuation
behaviors at the macroscopic scale. We show that, in such a case, the choice of
system temperature and mapping of DPD scales to physical scales are uniquely
determined by the level of coarse-graining and properties of DPD fluids. We
also verified that DPD simulation can reproduce the macroscopic effects of
thermal fluctuation in particulate suspension by showing that the Brownian
diffusion of solid particles can be computed in DPD simulations with good
accuracy
Covariant entropy conjecture and concordance cosmological models
Recently a covariant entropy conjecture has been proposed for dynamical
horizons. We apply this conjecture to concordance cosmological models, namely,
those cosmological models filled with perfect fluids, in the presence of a
positive cosmological constant. As a result, we find this conjecture has a
severe constraint power. Not only does this conjecture rule out those
cosmological models disfavored by the anthropic principle, but also it imposes
an upper bound on the cosmological constant for our own universe,
which thus provides an alternative macroscopic perspective for understanding
the long-standing cosmological constant problem.Comment: 10 pages, 1 figure, JHEP style, references added, published versio
A Possible Way of Connecting the Grassmann Variables and the Number of Generation
We construct a Left-Right symmetric model in which the number of generation
is related to Grassmann variables. We introduce two sets of complex Grassmann
variables (,), (, ) and
associate each variable with left- and right-handed quark and lepton fields,
respectively. Expanding quark and lepton fields in powers of the Grassmann
variables, we find that there are exactly three generations of quarks and
leptons. Integrating out the Grassmann variables, we obtain phenomenologically
acceptable fermion mass matrices.Comment: 7 pages, Revtex, UM-P-93/40, OZ-93/1
Relay Backpropagation for Effective Learning of Deep Convolutional Neural Networks
Learning deeper convolutional neural networks becomes a tendency in recent
years. However, many empirical evidences suggest that performance improvement
cannot be gained by simply stacking more layers. In this paper, we consider the
issue from an information theoretical perspective, and propose a novel method
Relay Backpropagation, that encourages the propagation of effective information
through the network in training stage. By virtue of the method, we achieved the
first place in ILSVRC 2015 Scene Classification Challenge. Extensive
experiments on two challenging large scale datasets demonstrate the
effectiveness of our method is not restricted to a specific dataset or network
architecture. Our models will be available to the research community later.Comment: Technical report for our submissions to the ILSVRC 2015 Scene
Classification Challenge, where we won the first plac
Model for a Light Z' Boson
A model of a light boson is constructed and phenomenological bounds are
derived. This boson arises from a very simple extension to the Standard
Model, and it is constrained to be light because the vacuum expectation values
which generate its mass also break the electroweak gauge group. It is difficult
to detect experimentally because it couples exclusively or primarily (depending
on symmetry breaking details) to second and third generation leptons. However,
if the boson is sufficiently light, then there exists the possibility of
the two-body decay occuring. This will provide a
striking signature to test the model.Comment: 20 pages + 5 pages of figures (appended as postscipt files), LaTeX,
OITS-53
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