38,203 research outputs found
Compression-induced failure of electro-active polymeric thin films
The insurgence of compression induces wrinkling in actuation devices based on
EAPs thin films leading to a sudden decrease of performances up to failure.
Based on the classical tension field theory for thin elastic membranes, we
provide a general framework for the analysis of the insurgence of in-plane
compression in membranes of electroactive polymers (EAPs). Our main result is
the deduction of a (voltage-dependent) domain in the stretch space which
represents tensile configurations. Under the assumption of Mooney-Rivlin
materials, we obtain that for growing values of the applied voltage the domain
contracts, vanishing at a critical voltage above which the polymer is wrinkled
for any stretch configuration. Our approach can be easily implemented in
numerical simulations for more complex material behaviors and provides a tool
for the analysis of compression instability as a function of the elastic
moduli.Comment: (15 pages, 7 figures
Algebraic Many-Body Localization and its implications on information propagation
We probe the existence of a many-body localized phase (MBL-phase) in a
spinless fermionic Hubbard chain with algebraically localized single-particle
states, by investigating both static and dynamical properties of the system.
This MBL-phase can be characterized by an extensive number of integrals of
motion which develop algebraically decaying tails, unlike the case of
exponentially localized single-particle states. We focus on the implications
for the quantum information propagation through the system. We provide evidence
that the bipartite entanglement entropy after a quantum quench has an unbounded
algebraic growth in time, while the quantum Fisher information grows
logarithmically
Efficiency gains and mergers
In the theoretical literature, strong arguments have been provided in support of the efficiency defense in antitrust merger policy. One of the most often cited results is due to Williamson (1968) that shows how relatively small reduction in cost could offset the deadweight loss of a large price increase. Furthermore, Salant et al. (1983) demonstrate that (not for monopoly) mergers are unprofitable absent efficiency gains. The general result, drawn in a Cournot framework by Farrell and Shapiro (1990), is that (not too large) mergers that are profitable are always welfare improving. In the present work we challenge the conclusions of this literature in two aspects. First, we show that Williamson's results underestimate the welfare loss due to a price increase and overestimate the effect of efficiency gains. Then, we prove that the conditions for welfare improving mergers defined by Farrell and Shapiro (1990) hold true only when consumers are adversely affected. This seems an argument to disregard their policy prescriptions when antitrust authorities are more "consumers-oriented". In this respect, we provide a necessary and sufficient condition for a consumer surplus improving merger: in a two firm merger, efficiency gains must be larger than the pre-merger average markup
Topological aspects of generalized Harper operators
A generalized version of the TKNN-equations computing Hall conductances for
generalized Dirac-like Harper operators is derived. Geometrically these
equations relate Chern numbers of suitable (dual) bundles naturally associated
to spectral projections of the operators.Comment: 8 pages; needs aipproc.cls and corresponding style files. To appear
in: "The Eight International Conference on Progress in Theoretical Physics",
Mentouri University, Constantine, Algeria, October 2011; Conference
proceedings of the AIP, edited by N. Mebarki and J. Mimoun
Privatization in oligopoly : the impact of the shadow cost of public funds
The aim of this paper is to investigate the welfare eect of privatization in oligopoly when the government takes into account the distortionary eect of rising funds by taxation (shadow cost of public funds). We analyze the impact of the change in ownership not only on the objective function of the rms, but also on the timing of competition by endogenizing the determination of simultaneous (Nash-Cournot) versus sequential (Stackelberg) games. We show that, absent effciency gains, privatization never increases welfare. Moreover, even when large effciency gains are realized, an ineffcient public rm may be preferred
A numerical method to calculate the muon relaxation function in the presence of diffusion
We present an accurate and efficient method to calculate the effect of random
fluctuations of the local field at the muon, for instance in the case muon
diffusion, within the framework of the strong collision approximation. The
method is based on a reformulation of the Markovian process over a discretized
time base, leading to a summation equation for the muon polarization function
which is solved by discrete Fourier transform. The latter is formally
analogous, though not identical, to the integral equation of the original
continuous-time model, solved by Laplace transform. With real-case parameter
values, the solution of the discrete-time strong collision model is found to
approximate the continuous-time solution with excellent accuracy even with a
coarse-grained time sampling. Its calculation by the fast Fourier transform
algorithm is very efficient and suitable for real time fitting of experimental
data even on a slow computer.Comment: 7 pages, 3 figures. Submitted to Journal of Physics: Condensed Matte
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