62,937 research outputs found
Coherent adiabatic theory of two-electron quantum dot molecules in external spin baths
We derive an accurate molecular orbital based expression for the coherent
time evolution of a two-electron wave function in a quantum dot molecule where
the electrons interact with each other, with external time dependent
electromagnetic fields and with a surrounding nuclear spin reservoir. The
theory allows for direct numerical modeling of the decoherence in quantum dots
due to hyperfine interactions. Calculations result in good agreement with
recent singlet-triplet dephasing experiments by Laird et. al. [Phys. Rev. Lett.
97, 056801 (2006)], as well as analytical model calculations. Furthermore, it
is shown that using a much faster electric switch than applied in these
experiments will transfer the initial state to excited states where the
hyperfine singlet-triplet mixing is negligible.Comment: 4 pages, 3 figure
The application of the global isomorphism to the study of liquid-vapor equilibrium in two and three dimensional Lenard-Jones fluids
We analyze the interrelation between the coexistence curve of the
Lennard-Jones fluid and the Ising model in two and three dimensions within the
global isomorphism approach proposed earlier [V. L. Kulinskii, J. Phys. Chem. B
\textbf{114} 2852 (2010)]. In case of two dimensions we use the exact Onsager
result to construct the binodal of the corresponding Lennard-Jones fluid and
compare it with the results of the simulations. In the three dimensional case
we use available numerical results for the Ising model for the corresponding
mapping. The possibility to observe the singularity of the binodal diameter is
discussed.Comment: 9 pages, 2 figure
A global protocol for monitoring of coral bleaching
Coral bleaching and subsequent mortality represent a major threat to the future health and productivity of coral reefs. However a lack of reliable data on occurrence, severity and other characteristics of bleaching events hampers research on the causes and consequences of this important phenomenon. This article describes a global protocol for monitoring coral bleaching events, which addresses this problem and can be used by people with different levels of expertise and resources
Thermodynamics and phase behavior of the lamellar Zwanzig model
Binary mixtures of lamellar colloids represented by hard platelets are
studied within a generalization of the Zwanzig model for rods, whereby the
square cuboids can take only three orientations along the , or axes.
The free energy is calculated within Rosenfeld's ''Fundamental Measure Theory''
(FMT) adapted to the present model. In the one-component limit, the model
exhibits the expected isotropic to nematic phase transition, which narrows as
the aspect ratio ( is the width and the thickness of the
platelets) increases. In the binary case the competition between nematic
ordering and depletion-induced segregation leads to rich phase behaviour.Comment: 9 pages, 6 figure
Macroion adsorption: The crucial role of excluded volume and coions
The adsorption of charged colloids (macroions) onto an oppositely charged
planar substrate is investigated theoretically. Taking properly into account
the finite size of the macroions, unusual behaviors are reported. It is found
that the role of the coions (the little salt-ions carrying the same sign of
charge as that of the substrate) is crucial to understand the mechanisms
involved in the process of macroion adsorption. In particular, the coions can
accumulate near the substrate's surface and lead to a counter-intuitive {\it
surface charge amplification}.Comment: 11 pages - 4 figures. To appear in JC
Conditional quantum state engineering in repeated 2-photon down conversion
The U(1,1) and U(2) transformations realized by three-mode interaction in the
respective parametric approximations are studied in conditional measurement,
and the corresponding non-unitary transformation operators are derived. As an
application, the preparation of single-mode quantum states using an optical
feedback loop is discussed, with special emphasis of Fock state preparation.
For that example, the influence of non-perfect detection and feedback is also
considered.Comment: 17 pages, 4 figures, using a4.st
Temperature equilibration in a fully ionized plasma: electron-ion mass ratio effects
Brown, Preston, and Singleton (BPS) produced an analytic calculation for
energy exchange processes for a weakly to moderately coupled plasma: the
electron-ion temperature equilibration rate and the charged particle stopping
power. These precise calculations are accurate to leading and next-to-leading
order in the plasma coupling parameter, and to all orders for two-body quantum
scattering within the plasma. Classical molecular dynamics can provide another
approach that can be rigorously implemented. It is therefore useful to compare
the predictions from these two methods, particularly since the former is
theoretically based and the latter numerically. An agreement would provide both
confidence in our theoretical machinery and in the reliability of the computer
simulations. The comparisons can be made cleanly in the purely classical
regime, thereby avoiding the arbitrariness associated with constructing
effective potentials to mock up quantum effects. We present here the classical
limit of the general result for the temperature equilibration rate presented in
BPS. We examine the validity of the m_electron/m_ion --> 0 limit used in BPS to
obtain a very simple analytic evaluation of the long-distance, collective
effects in the background plasma.Comment: 14 pages, 4 figures, small change in titl
An exact formalism to study the thermodynamic properties of hard-sphere systems under spherical confinement
This paper presents a modified grand canonical ensemble which provides a new
simple and efficient scheme to study few-body fluid-like inhomogeneous systems
under confinement. The new formalism is implemented to investigate the exact
thermodynamic properties of a hard sphere (HS) fluid-like system with up to
three particles confined in a spherical cavity. In addition, the partition
function of this system was used to analyze the surface thermodynamic
properties of the many-HS system and to derive the exact curvature dependence
of both the surface tension and adsorption in powers of the density. The
expressions for the surface tension and the adsorption were also obtained for
the many- HS system outside of a fixed hard spherical object. We used these
results to derive the dependence of the fluid-substrate Tolman length up to
first order in density.Comment: 6 figures. The paper includes new exact results about hard spheres
fluid-like system
A global protocol for monitoring of coral bleaching
Coral bleaching and subsequent mortality represent a major threat to the future health and productivity of coral reefs. However a lack of reliable data on occurrence, severity and other characteristics of bleaching events hampers research on the causes and consequences of this important phenomenon. This article describes a global protocol for monitoring coral bleaching events, which addresses this problem and can be used by people with different levels of expertise and resources.Coral reefs, Bleaching, Mortality, Monitoring
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