61,950 research outputs found
Stabilizing Entangled States with Quasi-Local Quantum Dynamical Semigroups
We provide a solution to the problem of determining whether a target pure
state can be asymptotically prepared using dissipative Markovian dynamics under
fixed locality constraints. Beside recovering existing results for a large
class of physically relevant entangled states, our approach has the advantage
of providing an explicit stabilization test solely based on the input state and
constraints of the problem. Connections with the formalism of frustration-free
parent Hamiltonians are discussed, as well as control implementations in terms
of a switching output-feedback law.Comment: 11 pages, no figure
Non-commutative holonomies in 2+1 LQG and Kauffman's brackets
We investigate the canonical quantization of 2+1 gravity with {\Lambda} > 0
in the canonical framework of LQG. A natural regularization of the constraints
of 2+1 gravity can be defined in terms of the holonomies of A\pm = A \PM
\surd{\Lambda}e, where the SU(2) connection A and the triad field e are the
conjugated variables of the theory. As a first step towards the quantization of
these constraints we study the canonical quantization of the holonomy of the
connection A_{\lambda} = A + {\lambda}e acting on spin network links of the
kinematical Hilbert space of LQG. We provide an explicit construction of the
quantum holonomy operator, exhibiting a close relationship between the action
of the quantum holonomy at a crossing and Kauffman's q-deformed crossing
identity. The crucial difference is that the result is completely described in
terms of standard SU(2) spin network states.Comment: 4 pages; Proceedings of Loops'11, Madrid, to appear in Journal of
Physics: Conference Series (JPCS
Self-optimized construction of transition rate matrices from accelerated atomistic simulations with Bayesian uncertainty quantification
A massively parallel method to build large transition rate matrices from
temperature accelerated molecular dynamics trajectories is presented. Bayesian
Markov model analysis is used to estimate the expected residence time in the
known state space, providing crucial uncertainty quantification for higher
scale simulation schemes such as kinetic Monte Carlo or cluster dynamics. The
estimators are additionally used to optimize where exploration is performed and
the degree of temperature ac- celeration on the fly, giving an autonomous,
optimal procedure to explore the state space of complex systems. The method is
tested against exactly solvable models and used to explore the dynamics of C15
interstitial defects in iron. Our uncertainty quantification scheme allows for
accurate modeling of the evolution of these defects over timescales of several
seconds.Comment: 14 pages, 7 figure
Towards an analytical theory for charged hard spheres
Ion mixtures require an exclusion core to avoid collapse. The Debye Hueckel
theory, where ions are point charges, is accurate only in the limit of infinite
dilution. The MSA is the embedding of hard cores into DH, is valid for higher
densities. In the MSA the properties of any ionic mixture can be represented by
a single screening parameter . For equal ionic size restricted model is
obtained from the Debye parameter . This one parameter representation
(BIMSA) is valid for complex and associating systems, such as the general
n-polyelectrolytes. The BIMSA is the only theory that satisfies the infinite
dilution limit of the DH theory for any chain length. The contact pair
distribution function of hard ions mixture is a functional of and a
small mean field parameter. This yields good agreement with the Monte Carlo
(Bresme et al. Phys. Rev. E {\textbf 51} 289 (1995)) .Comment: 6 pages, 1 figur
Tornadoes in a Microchannel
In non-dilute colloidal suspensions, gradients in particle volume fraction
result in gradients in electrical conductivity and permittivity. An externally
applied electric field couples with gradients in electrical conductivity and
permittivity and, under some conditions, can result in electric body forces
that drive the flow unstable forming vortices. The experiments are conducted in
square 200 micron PDMS microfluidic channels. Colloidal suspensions consisted
of 0.01 volume fraction of 2 or 3 micron diameter polystyrene particles in 0.1
mM Phosphate buffer and 409 mM sucrose to match particle-solution density. AC
electric fields at 20 Hz and strength of 430 to 600 V/cm were used. We present
a fluid dynamics video that shows the evolution of the particle aggregation and
formation of vortical flow. Upon application of the field particles aggregate
forming particle chains and three dimensional structures. These particles form
rotating bands where the axis of rotation varies with time and can collide with
other rotating bands forming increasingly larger bands. Some groups become
vortices with a stable axis of rotation. Other phenomena showed include counter
rotating vortices, colliding vortices, and non-rotating particle bands with
internal waves
Background and principle applications of remote sensing in Mexico
Remote sensing, or the collection of information from objectives at a distance, crystallizes the interest in implementing techniques which assist in the search for solutions to the problems raised by the detection, exploitation, and conservation of the natural resources of the earth. An attempt is made to present an overview of the studies and achievements which have been obtained with remote sensing in Mexico
Measurement of the ΄ (1S) production cross-section in pp collisions at âs = 7 TeV in ATLAS
A measurement of the cross-section for ΄ (1S)âÎŒ^+ÎŒ^â production in protonâproton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the ΄ (1S) transverse momentum in two bins of rapidity, |y^(΄(1S))| 4 GeV and pseudorapidity |η^ÎŒ| < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarisation. The results are based on an integrated luminosity of 1.13 pb^(â1), collected with the ATLAS detector at the
Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees
to within a factor of two with a prediction based on the NRQCD model including colour-singlet and
colour-octet matrix elements as implemented in Pythia while it disagrees by up to a factor of ten with
the next-to-leading order prediction based on the colour-singlet model
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