4,744 research outputs found
Hydrodynamic Coupling of Particle Inclusions Embedded in Curved Lipid Bilayer Membranes
We develop theory and computational methods to investigate particle
inclusions embedded within curved lipid bilayer membranes. We consider the case
of spherical lipid vesicles where inclusion particles are coupled through (i)
intramembrane hydrodynamics, (ii) traction stresses with the external and
trapped solvent fluid, and (iii) intermonolayer slip between the two leaflets
of the bilayer. We investigate relative to flat membranes how the membrane
curvature and topology augment hydrodynamic responses. We show how both the
translational and rotational mobility of protein inclusions are effected by the
membrane curvature, ratio of intramembrane viscosity to solvent viscosity, and
inter-monolayer slip. For general investigations of many-particle dynamics, we
also discuss how our approaches can be used to treat the collective diffusion
and hydrodynamic coupling within spherical bilayers.Comment: 32 pages, double-column format, 15 figure
What Is a Macrostate? Subjective Observations and Objective Dynamics
We consider the question of whether thermodynamic macrostates are objective
consequences of dynamics, or subjective reflections of our ignorance of a
physical system. We argue that they are both; more specifically, that the set
of macrostates forms the unique maximal partition of phase space which 1) is
consistent with our observations (a subjective fact about our ability to
observe the system) and 2) obeys a Markov process (an objective fact about the
system's dynamics). We review the ideas of computational mechanics, an
information-theoretic method for finding optimal causal models of stochastic
processes, and argue that macrostates coincide with the ``causal states'' of
computational mechanics. Defining a set of macrostates thus consists of an
inductive process where we start with a given set of observables, and then
refine our partition of phase space until we reach a set of states which
predict their own future, i.e. which are Markovian. Macrostates arrived at in
this way are provably optimal statistical predictors of the future values of
our observables.Comment: 15 pages, no figure
Relativistic fluid dynamics and its extensions as an effective field theory
We examine hydrodynamics from the perspective of an effective field theory.
The microscopic scale in this case is the thermalization scale, and the
macroscopic scale is the gradient, with thermal fluctuations playing the role
of . We argue that this method can be applied both, to consistently
include thermal fluctuations in the theory, and to extend hydrodynamics to
systems whose microscopic structure is non-trivial. For the latter, we discuss
the case of spin polarization and gauge theories.Comment: Proceedings for the "Epiphany in Krakow 2019" conference, submitted
to Acta Fisica Polonic
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