On monopole operators in supersymmetric Chern-Simons-matter theories

We discuss monopole operators in $U(N_c)$ Chern-Simons-matter theories in three space-time dimensions. We mention an apparent problem in the matching of such operators in dualities between non-supersymmetric theories, and suggest a possible resolution. A similar apparent problem exists in the mapping of chiral monopole operators in theories with ${\cal N}=2$ supersymmetry. We show that in many theories the lowest naive chiral monopole operator is actually not chiral, and we find the lowest monopole operator that is actually chiral in these theories. It turns out that there are several different forms of this operator, depending on the number of colors, the number of flavours, and the Chern-Simons level. Since we use the supersymmetric index to find the lowest chiral monopoles, our results for these monopoles are guaranteed to be invariant under the dualities in supersymmetric theories. The theories we discuss are believed to be dual in the 't~Hooft large $N_c$ limit to classical high-spin gravity theories. We argue that these theories (supersymmetric or not) should not have classical solutions charged under the $U(1)$ gauge field in the high-spin multiplet.Comment: 39 pages. v2: fixed typo

An architecture for intelligent task interruption

In the design of real time systems the capability for task interruption is often considered essential. The problem of task interruption in knowledge-based domains is examined. It is proposed that task interruption can be often avoided by using appropriate functional architectures and knowledge engineering principles. Situations for which task interruption is indispensable, a preliminary architecture based on priority hierarchies is described

Magnetothermal and magnetorotational instabilities in hot accretion flows

In a hot, dilute, magnetized accretion flow, the electron mean-free path can be much greater than the Larmor radius, thus thermal conduction is anisotropic and along magnetic field lines. In this case, if the temperature decreases outward, the flow may be subject to a buoyancy instability (the magnetothermal instability, or MTI). The MTI amplifies the magnetic field, and aligns field lines with the radial direction. If the accretion flow is differentially rotating, the magnetorotational instability (MRI) may also be present. Using two-dimensional, time-dependent magnetohydrodynamic simulations, we investigate the interaction between these two instabilities. We use global simulations that span over two orders of magnitude in radius, centered on the region around the Bondi radius where the infall time of gas is longer than the growth time of both the MTI and MRI. Significant amplification of the magnetic field is produced by both instabilities, although we find that the MTI primarily amplifies the radial component, and the MRI primarily the toroidal component, of the field, respectively. Most importantly, we find that if the MTI can amplify the magnetic energy by a factor $F_t$, and the MRI by a factor $F_r$, then when the MTI and MRI are both present, the magnetic energy can be amplified by a factor of $F_t \cdot F_r$. We therefore conclude that amplification of the magnetic energy by the MTI and MRI operates independently. We also find that the MTI contributes to the transport of angular momentum, because radial motions induced by the MTI increase the Maxwell (by amplifying the magnetic field) and Reynolds stresses. Finally, we find that thermal conduction decreases the slope of the radial temperature profile. The increased temperature near the Bondi radius decreases the mass accretion rate.Comment: 8 pages, 9 figures, accepted by MNRA

Investment and oil price volatility

In this note, we consider the relationship between oil price volatility and firm returns for 560 firms listed on the New York Stock Exchange. Using daily time series data from 2000 to 2008, we find that oil price volatility increases firm returns for the majority of the firms in our sample.Investment, oil price, volatility,

Electrochemical determination of surface area-to-volume ratio for metal nanoparticle analysis.

This dissertation describes an electrochemical approach for measuring the surface area-to-volume ratio (SA/V) of electrode-attached metal nanoparticles (NPs), which was used to analyze their size, aggregation state, and porosity. This dissertation further describes the effect of the metal NP electrode assembly method on the SA/V, which is related to metal NP catalytic activity and stability. Cyclic voltammetry (CV) in acid electrolyte followed by anodic stripping voltammetry (ASV) in KBr electrolyte allows the electrochemical measurement of the SA/V of electrode-attached Au nanospheres (NSs). In CV, the forward scan produces a thin surface Au2O3 layer on the Au NSs. Measuring the Coulombs of charge passed during the reduction of the Au2O3 on the reverse scan allows a measurement of the total surface area (SA) of all NSs on the electrode. Subsequent measurement of the Coulombs of charge passed during oxidative dissolution of all of the Au NSs in KBr electrolyte provides a measurement of the total V of the Au NSs. Since the radius of a sphere is equal to 3/(SA/V), the SA/V provides a direct measure of the Au NS size, which matches very closely to the size of several Au NSs ranging from 4 nm to 70 nm in diameter based on scanning electron microscopy (SEM) size measurements.. Electrochemical SA/V measurements provide information about the aggregation state of electrode-attached Au NSs. The SA/V decreases as 4 nm and 15 nm diameter Au NSs go from isolated NSs to aggregated structures, caused by the neutralization of the citrate stabilizer at low pH. The decreased SA/V for aggregated Au NSs accounts for the positive shift in the peak oxidation potential (Ep) of aggregated NSs compared to isolated ones. The SA/V of distorted, flattened, and porous Au NSs formed by dealloying Ag from AuAg alloy NSs increases with an increasing percentage of Ag in the initial alloy NSs. Greater removal of Ag leads to greater porosity and a higher SA/V. The increased SA/V for porous NSs resulted in a negative shift in Ep relative to similar diameter non-porous Au NSs. The SA/V of similar sized NSs assembled onto indium-tin-oxide-coated glass electrodes (glass/ITO) by different assembly methods, including electrostatic attachment to an amine-functionalized silane linker, electrophoretic deposition (EPD), direct drop-cast deposition, and drop-cast deposition after mixing with carbon black, can be dramatically different. Au NSs with higher SA/V generally exhibit higher electrocatalytic activity, as demonstrated for the oxygen reduction reaction (ORR), but also oxidize at lower potentials (lower Ep). The SA/V follow the order of electrostatic attachment \u3e EPD \u3e drop-cast with carbon black \u3e drop-cast. Since different assembly methods lead to different SA/V for the same size Au NSs, the SA/V is a better predictor of Ep, or the oxidation properties of the NSs, compared to the size (or curvature) of the Au NSs. This is generally true for all of the different variables studied in this dissertation, including NSs of different size, aggregation state, porosity, and assembled by different methods. The SA/V provides important information about both activity and stability of metal NPs