10,160 research outputs found
Delivery of Functionality in Complex Food Systems: Physically Inspired Approaches from Nanoscale to Microscale, Wageningen 18-21 October 2009
The Wageningen Delivery of Functionality symposium covered all aspects involved with food structural design to arrive at high-quality foods which meet demanding customer expectations and regulatory requirements. The symposium integrated aspects from the structural organization of foods at molecular and supramolecular scales to dedicated techniques required to describe and visualize such structures, the gastro-intestinal events and how to model these in a laboratory setting, and finally the impact those food structures and ingredients have on the consumer’s physiology and on the human perception. As an interdisciplinary platform, bringing together more than 160 researchers from academia and industry, the symposium meanwhile fulfills an important role in the food science communit
Why the Tsirelson bound?
Wheeler's question 'why the quantum' has two aspects: why is the world
quantum and not classical, and why is it quantum rather than superquantum,
i.e., why the Tsirelson bound for quantum correlations? I discuss a remarkable
answer to this question proposed by Pawlowski et al (2009), who provide an
information-theoretic derivation of the Tsirelson bound from a principle they
call 'information causality.'Comment: 17 page
The smallest refrigerators can reach maximal efficiency
We investigate whether size imposes a fundamental constraint on the
efficiency of small thermal machines. We analyse in detail a model of a small
self-contained refrigerator consisting of three qubits. We show analytically
that this system can reach the Carnot efficiency, thus demonstrating that there
exists no complementarity between size and efficiency.Comment: 9 pages, 1 figure. v2: published versio
Recommended from our members
The distribution of value in the mobile phone supply chain
The supply chains of the mobile phone industry span national and firm boundaries. To analyze how value is distributed among the participants, a framework based on theories of firm strategy is applied, and a novel methodology is used to measure value capture in three phone models introduced from 2004 to 2008. The research shows that carriers capture the greatest value (in terms of gross profit) from each handset, followed closely by handset makers, with suppliers a distant third. However, the situation is reversed in terms of operating profit. Carriers shoulder the burden of network installation, maintenance, and upgrading, which absorbs much of the value from their subscription fees. Handset maker nationality, which may also influence supplier choice, is a key determinant of the geographic distribution of value capture. The results are also used to estimate the relationship of handset subsidies to carrier profits, which has been an issue of concern for antitrust authorities in several countries. The analysis shows how the framework can be used to calculate how much service charges might be inflated to cover the subsidies. © 2011 Elsevier Ltd. All rights reserved
Quasi-Particle Degrees of Freedom versus the Perfect Fluid as Descriptors of the Quark-Gluon Plasma
The hot nuclear matter created at the Relativistic Heavy Ion Collider (RHIC)
has been characterized by near-perfect fluid behavior. We demonstrate that this
stands in contradiction to the identification of QCD quasi-particles with the
thermodynamic degrees of freedom in the early (fluid) stage of heavy ion
collisions. The empirical observation of constituent quark ``'' scaling of
elliptic flow is juxtaposed with the lack of such scaling behavior in
hydrodynamic fluid calculations followed by Cooper-Frye freeze-out to hadrons.
A ``quasi-particle transport'' time stage after viscous effects break down the
hydrodynamic fluid stage, but prior to hadronization, is proposed to reconcile
these apparent contradictions. However, without a detailed understanding of the
transitions between these stages, the ``'' scaling is not a necessary
consequence of this prescription. Also, if the duration of this stage is too
short, it may not support well defined quasi-particles. By comparing and
contrasting the coalescence of quarks into hadrons with the similar process of
producing light nuclei from nucleons, it is shown that the observation of
``'' scaling in the final state does not necessarily imply that the
constituent degrees of freedom were the relevant ones in the initial state.Comment: 9 pages, 7 figures, Updated text and figure
Photoemission spectra of many-polaron systems
The cross over from low to high carrier densities in a many-polaron system is
studied in the framework of the one-dimensional spinless Holstein model, using
unbiased numerical methods. Combining a novel quantum Monte Carlo approach and
exact diagonalization, accurate results for the single-particle spectrum and
the electronic kinetic energy on fairly large systems are obtained. A detailed
investigation of the quality of the Monte Carlo data is presented. In the
physically most important adiabatic intermediate electron-phonon coupling
regime, for which no analytical results are available, we observe a
dissociation of polarons with increasing band filling, leading to normal
metallic behavior, while for parameters favoring small polarons, no such
density-driven changes occur. The present work points towards the inadequacy of
single-polaron theories for a number of polaronic materials such as the
manganites.Comment: 15 pages, 13 figures; final version, accepted for publication in
Phys. Rev.
Entanglement capabilities of non-local Hamiltonians
We quantify the capability of creating entanglement for a general physical
interaction acting on two qubits. We give a procedure for optimizing the
generation of entanglement. We also show that a Hamiltonian can create more
entanglement if one uses auxiliary systems.Comment: replaced with published version, 4 pages, no figure
Optimal simulation of two-qubit Hamiltonians using general local operations
We consider the simulation of the dynamics of one nonlocal Hamiltonian by
another, allowing arbitrary local resources but no entanglement nor classical
communication. We characterize notions of simulation, and proceed to focus on
deterministic simulation involving one copy of the system. More specifically,
two otherwise isolated systems and interact by a nonlocal Hamiltonian
. We consider the achievable space of Hamiltonians such
that the evolution can be simulated by the interaction
interspersed with local operations. For any dimensions of and , and any
nonlocal Hamiltonians and , there exists a scale factor such that
for all times the evolution can be simulated by acting for
time interspersed with local operations. For 2-qubit Hamiltonians and
, we calculate the optimal and give protocols achieving it. The optimal
protocols do not require local ancillas, and can be understood geometrically in
terms of a polyhedron defined by a partial order on the set of 2-qubit
Hamiltonians.Comment: (1) References to related work, (2) protocol to simulate one
two-qudit Hamiltonian with another, and (3) other related results added. Some
proofs are simplifie
Cut-wire pairs and plate pairs as magnetic atoms for optical metamaterials
We study the optical properties of metamaterials made from cut-wire pairs or
plate pairs. We obtain a more pronounced optical response for arrays of plate
pairs -- a geometry which also eliminates the undesired polarization anisotropy
of the cut-wire pairs. The measured optical spectra agree with simulations,
revealing negative magnetic permeability in the range of telecommunications
wavelengths. Thus, nanoscopic plate pairs might serve as an alternative to the
established split-ring resonator design.Comment: 3 pages, 4 figures, submitted to Opt. Let
Consistent Application of Maximum Entropy to Quantum-Monte-Carlo Data
Bayesian statistics in the frame of the maximum entropy concept has widely
been used for inferential problems, particularly, to infer dynamic properties
of strongly correlated fermion systems from Quantum-Monte-Carlo (QMC) imaginary
time data. In current applications, however, a consistent treatment of the
error-covariance of the QMC data is missing. Here we present a closed Bayesian
approach to account consistently for the QMC-data.Comment: 13 pages, RevTeX, 2 uuencoded PostScript figure
- …