6,188 research outputs found
Computing derivative-based global sensitivity measures using polynomial chaos expansions
In the field of computer experiments sensitivity analysis aims at quantifying
the relative importance of each input parameter (or combinations thereof) of a
computational model with respect to the model output uncertainty. Variance
decomposition methods leading to the well-known Sobol' indices are recognized
as accurate techniques, at a rather high computational cost though. The use of
polynomial chaos expansions (PCE) to compute Sobol' indices has allowed to
alleviate the computational burden though. However, when dealing with large
dimensional input vectors, it is good practice to first use screening methods
in order to discard unimportant variables. The {\em derivative-based global
sensitivity measures} (DGSM) have been developed recently in this respect. In
this paper we show how polynomial chaos expansions may be used to compute
analytically DGSMs as a mere post-processing. This requires the analytical
derivation of derivatives of the orthonormal polynomials which enter PC
expansions. The efficiency of the approach is illustrated on two well-known
benchmark problems in sensitivity analysis
Phenomenological model for a novel melt-freeze phase of sliding bilayers
Simulations show that sliding bilayers of colloidal particles can exhibit a
new phase, the ``melt-freeze'' phase, where the layers stochastically alternate
between solidlike and liquidlike states. We introduce a mean field
phenomenological model with two order parameters to understand the interplay of
two adjacent layers while the system is in this remarkable phase. Predictions
from our numerical simulations of a system in the melt-freeze phase include the
tendency of two adjacent layers to be in opposite states (solid and liquid) and
the difference between the fluctuation of the order parameter in one layer
while the other layer is in the same phase compared to the fluctuation while
the other layer is in the opposite phase. We expect this behavior to be seen in
future simulations and experiments.Comment: 6 Pages, 6 figure
Photocurrent in a visible-light graphene photodiode
We calculate the photocurrent in a clean graphene sample normally irradiated
by a monochromatic electromagnetic field and subject to a step-like
electrostatic potential. We consider the photon energies that
significantly exceed the height of the potential barrier, as is the case in the
recent experiments with graphene-based photodetectors. The photocurrent comes
from the resonant absorption of photons by electrons and decreases with
increasing ratio . It is weakly affected by the background
gate voltage and depends on the light polarization as ,
being the angle between the potential and the polarization plane.Comment: 5 pages, 3 figure
The t-t'-J model in one dimension using extremely correlated Fermi liquid theory and time dependent density matrix renormalization group
We study the one dimensional t-t'-J model for generic couplings using two
complementary theories, the extremely correlated Fermi liquid theory and
time-dependent density matrix renormalization group over a broad energy scale.
The two methods provide a unique insight into the strong momentum dependence of
the self-energy of this prototypical non-Fermi liquid, described at low
energies as a Tomonaga-Luttinger liquid. We also demonstrate its intimate
relationship to spin-charge separation, i.e. the splitting of Landau
quasiparticles of higher dimensions into two constituents, driven by strong
quantum fluctuations inherent in one dimension. The momentum distribution
function, the spectral function, and the excitation dispersion of these two
methods also compare well
What we know about anticonsumption: An attempt to nail jelly to the wall
Despite burgeoning academic interest in anticonsumption, a lack of definitional clarity
and overlapping constructs beleaguer the pertinent literature, preventing research in
the field from reaching its full potential. This paper aims to strengthen the foundations
for advancing knowledge in this fragmented field by (a) undertaking a thorough
systematic review of literature; (b) charting the scope of anticonsumption literature
based on network analysis and attempting to delineate overlapping areas; (c) providing
an integrated framework of anticonsumption research, including antecedents,
moderators, and consequences; and (d) suggesting a set of specific research
propositions that will enable the field to move forward. Toward these aims, we
analyzed 120 anticonsumption papers revealed in the literature review, identifying a
number of important anticonsumptionârelated topics that warrant further investigation.
Moreover, we suggest a research framework which reveals antecedents, causal
sequences, and consequences of anticonsumption. Finally, a research agenda based on
this integrated framework indicates promising areas for future research
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