4D-XY quantum criticality in a doped Mott insulator

A new phenomenology is proposed for the superfluid density of strongly underdoped cuprate superconductors based on recent data for ultra-clean single crystals of YBCO. The data feature a puzzling departure from Uemura scaling and a decline of the slope as the T_c = 0 quantum critical point is approached. We show that this behavior can be understood in terms of the renormalization of quasiparticle effective charge by quantum fluctuations of the superconducting phase as described by a (3+1)-dimensional XY model. We calculate the renormalization of the superfluid density and its slope, explain the new phenomenology, and predict its eventual demise close to the QCP.Comment: Version published in PRL. For additional info and related work visit http://www.physics.ubc.ca/~fran

Emergence of the stochastic resonance in glow discharge plasma

stochastic resonance, glow discharge plasma, excitable medium, absolute mean differenceComment: St

Finiteness in derived categories of local rings

New homotopy invariant finiteness conditions on modules over commutative rings are introduced, and their properties are studied systematically. A number of finiteness results for classical homological invariants like flat dimension, injective dimension, and Gorenstein dimension, are established. It is proved that these specialize to give results concerning modules over complete intersection local rings. A noteworthy feature is the use of techniques based on thick subcategories of derived categories.Comment: 40 pages. Minor revisions. To appear in Commentarii Math. Helvetic

Accurate implementation of leaping in space: The spatial partitioned-leaping algorithm

There is a great need for accurate and efficient computational approaches that can account for both the discrete and stochastic nature of chemical interactions as well as spatial inhomogeneities and diffusion. This is particularly true in biology and nanoscale materials science, where the common assumptions of deterministic dynamics and well-mixed reaction volumes often break down. In this article, we present a spatial version of the partitioned-leaping algorithm (PLA), a multiscale accelerated-stochastic simulation approach built upon the tau-leaping framework of Gillespie. We pay special attention to the details of the implementation, particularly as it pertains to the time step calculation procedure. We point out conceptual errors that have been made in this regard in prior implementations of spatial tau-leaping and illustrate the manifestation of these errors through practical examples. Finally, we discuss the fundamental difficulties associated with incorporating efficient exact-stochastic techniques, such as the next-subvolume method, into a spatial-leaping framework and suggest possible solutions.Comment: 15 pages, 9 figures, 2 table

DG algebras with exterior homology

We study differential graded algebras whose homology is an exterior algebra over a commutative ring R on a generator of degree n, and also certain types of differential modules over these DGAs. We obtain a complete classification when R is the integers, or the prime field of characteristic p>0, and n is greater than or equal to -1. The examples are unexpectedly interesting.Comment: 15 page

Magnetic field effects on TcT_c and the pseudogap onset temperature in cuprate superconductors

We study the sensitivity of $T_c$ and the pseudogap onset temperature, $T^*$, to low fields, $H$, for cuprate superconductors, using a BCS-based approach extended to arbitrary coupling. We find that $T^*$ and $T_c$, which are of the same superconducting origin, have very different $H$ dependences. The small coherence length makes $T^*$ rather insensitive to the field. However, the presence of the pseudogap at $T_c$ makes $T_c$ more sensitive to $H$. Our results for the coherence length $\xi$ fit well with existing experiments. We predict that very near the insulator $\xi$ will rapidly increase.Comment: 4 pages, 1 figure, contribution to the PPHMF-IV conference, Oct. 200

Information Diffusion Power of Political Party Twitter Accounts During Japan's 2017 Election

In modern election campaigns, political parties utilize social media to advertise their policies and candidates and to communicate to electorates. In Japan's latest general election in 2017, the 48th general election for the Lower House, social media, especially Twitter, was actively used. In this paper, we perform a detailed analysis of social graphs and users who retweeted tweets of political parties during the election. Our aim is to obtain accurate information regarding the diffusion power for each party rather than just the number of followers. The results indicate that a user following a user who follows a political party account tended to also follow the account. This means that it does not increase diversity because users who follow each other tend to share similar values. We also find that followers of a specific party frequently retweeted the tweets. However, since users following the user who follow a political party account are not diverse, political parties delivered the information only to a few political detachment users.Comment: The 10th International Conference on Social Informatics (SocInfo 2018

Coherence resonance in an unijunction transistor relaxation oscillator

The phenomenon of coherence resonance (CR) is investigated in an unijunction transistor relaxation oscillator (UJT-RO) and quantified by estimating the normal variance (NV). Depending upon the measuring points two types of NV curves have been obtained. We have observed that the degradations in coherency at higher noise amplitudes in our system is probably the result of direct interference of coherent oscillations and the stochastic perturbation. Degradation of coherency may be minimal if this direct interference of noise and coherent oscillations is eliminated.Comment: 4 pages, Coherence resonace, Uni junction relaxation oscillato

Esterification of succinic anhydride to di-(p-cresyl) succinate over M n+-montmorillonite clay catalysts

Esterification of succinic anhydride to di-(p-cresyl) succinate over heterogeneous acid clay catalysts is reported. Montmorillonite clay samples exchanged with different cations were prepared and catalytic activity of the resulting materials was investigated in the synthesis of di-(p-cresyl) succinate esters. Among the exchanged clay catalysts, Al3+ and H +-mont were found to be more active for the esterification of succinic anhydride with p-cresol. The activity of Mn+-mont was found to be directly related to the charge to radius ratio of Mn+-ions. The influence of molar ratio of reactants, reaction time, and catalyst amount on the esterification reaction was investigated. The esterification was found to follow the second order rate kinetics and the kinetic parameters such as rate constant (k), equilibrium constant (K) and Gibbs free energy (ÎG°) for the reaction have been determined. The activity of Al3+-mont clay catalyst for the esterification of succinic anhydride with phenol, m-cresol, o-cresol, p-nitrophenol and resorcinol have been studied. Regeneration and reusability of the clay catalyst has also been investigated. © 2004 Elsevier B.V. All rights reserved

Magnetic Field Effects in the Pseudogap Phase: A Precursor Superconductivity Scenario

We demonstrate that the observed dependences of $T_c$ and $T^*$ on small magnetic fields can be readily understood in a precursor superconductivity approach to the pseudogap phase. In this approach, the presence of a pseudogap at $T_c$ (but not at $T^*$) and the associated suppression of the density of states lead to very different sensitivities to pair-breaking perturbations for the two temperatures. Our semi-quantitative results address the puzzling experimental observation that the coherence length $\xi$ is weakly dependent on hole concentration $x$ throughout most of the phase diagram. We present our results in a form which can be compared with the recent experiments of Shibauchi et al, and argue that orbital effects contribute in an important way to the $H$ dependence of $T^*$.Comment: 6 pages, 1 figure, elsart.cls included. Submitted to the proceeding of SNS 2001, Chicag