1,291 research outputs found
Complementarity in the Bohr-Einstein Photon Box
The photon box thought experiment can be considered a forerunner of the
EPR-experiment: by performing suitable measurements on the box it is possible
to ``prepare'' the photon, long after it has escaped, in either of two
complementary states. Consistency requires that the corresponding box
measurements be complementary as well. At first sight it seems, however, that
these measurements can be jointly performed with arbitrary precision: they
pertain to different systems (the center of mass of the box and an internal
clock, respectively). But this is deceptive. As we show by explicit
calculation, although the relevant quantities are simultaneously measurable,
they develop non-vanishing commutators when calculated back to the time of
escape of the photon. This justifies Bohr's qualitative arguments in a precise
way; and it illustrates how the details of the dynamics conspire to guarantee
the requirements of complementarity. In addition, our calculations exhibit a
``fine structure'' in the distribution of the uncertainties over the
complementary quantities: depending on \textit{when} the box measurement is
performed, the resulting quantum description of the photon differs. This brings
us close to the argumentation of the later EPR thought experiment
Fast kinetic Monte Carlo simulation of strained heteroepitaxy in three dimensions
Accelerated algorithms for simulating the morphological evolution of strained
heteroeptiaxy based on a ball and spring lattice model in three dimensions are
explained. We derive exact Green's function formalisms for boundary values in
the associated lattice elasticity problems. The computational efficiency is
further enhanced by using a superparticle surface coarsening approximation.
Atomic hoppings simulating surface diffusion are sampled using a multi-step
acceptance-rejection algorithm. It utilizes quick estimates of the atomic
elastic energies from extensively tabulated values modulated by the local
strain. A parameter controls the compromise between accuracy and efficiency of
the acceptance-rejection algorithm.Comment: 10 pages, 4 figures, submitted to Proceedings of Barrett Lectures
2007, Journal of Scientific Computin
Competing roughening mechanisms in strained heteroepitaxy: a fast kinetic Monte Carlo study
We study the morphological evolution of strained heteroepitaxial films using
kinetic Monte Carlo simulations in two dimensions. A novel Green's function
approach, analogous to boundary integral methods, is used to calculate elastic
energies efficiently. We observe island formation at low lattice misfit and
high temperature that is consistent with the Asaro-Tiller-Grinfeld instability
theory. At high misfit and low temperature, islands or pits form according to
the nucleation theory of Tersoff and LeGoues.Comment: 4 pages, 4 figures, ReVTe
Complementarity in the Einstein-Bohr Photon Box
The photon box thought experiment can be considered a forerunner of the
EPR-experiment: by performing suitable measurements on the box it is possible
to ``prepare'' the photon, long after it has escaped, in either of two
complementary states. Consistency requires that the corresponding box
measurements be complementary as well. At first sight it seems, however, that
these measurements can be jointly performed with arbitrary precision: they
pertain to different systems (the center of mass of the box and an internal
clock, respectively). But this is deceptive. As we show by explicit
calculation, although the relevant quantities are simultaneously measurable,
they develop non-vanishing commutators when calculated back to the time of
escape of the photon. This justifies Bohr's qualitative arguments in a precise
way; and it illustrates how the details of the dynamics conspire to guarantee
the requirements of complementarity. In addition, our calculations exhibit a
``fine structure'' in the distribution of the uncertainties over the
complementary quantities: depending on when the box measurement is performed,
the resulting quantum description of the photon differs. This brings us close
to the argumentation of the later EPR thought experiment
Island, pit, and groove formation in strained heteroepitaxy
2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Fractals in surface growth with power-law noise
The authors present a microscopic description of interface growth with power-law noise distribution in the form P( eta ) eta 1/ approximately 1+ mu , which exhibits non-universal roughening. For the mu =d+1 case in d+1 dimensions, the existence of a fractal pattern in the bulk of the aggregate is explained, leading trivially to the proof of the identity alpha +z=2 for the roughening and the dynamical scaling exponents alpha and z respectively. Investigations on the distribution of step sizes of the discretized interface and the saturated growth speed further support the arguments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48826/2/ja920309.pd
A Hybrid Monte Carlo Method for Surface Growth Simulations
We introduce an algorithm for treating growth on surfaces which combines
important features of continuum methods (such as the level-set method) and
Kinetic Monte Carlo (KMC) simulations. We treat the motion of adatoms in
continuum theory, but attach them to islands one atom at a time. The technique
is borrowed from the Dielectric Breakdown Model. Our method allows us to give a
realistic account of fluctuations in island shape, which is lacking in
deterministic continuum treatments and which is an important physical effect.
Our method should be most important for problems close to equilibrium where KMC
becomes impractically slow.Comment: 4 pages, 5 figure
Age-Related Macular Degeneration and Smoking Cessation Advice by Eye Care Providers: A Pilot Study
Smoking is a modifiable risk factor for age-related macular degeneration (AMD), the leading cause of irreversible vision loss in the United States. We conducted a pilot study among eye care providers and AMD patients to assess smoking cessation preferences and cessation services offered at a large academic medical center. Most patients who smoke reported never being advised to quit smoking, although most eye care providers reported that they had advised smokers to quit. Two-thirds of providers expressed a desire for additional training and resources to support patient quit attempts, indicating the need for the integration of smoking cessation opportunities in the clinic setting
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