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 $\hbar\Omega$ 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 $\hbar\Omega/U_0$. It is weakly affected by the background gate voltage and depends on the light polarization as $\propto\sin^2\gamma$, $\gamma$ 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 anticonsumption‐related 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