Super-Earths in the TW Hya disc

We test the hypothesis that the sub-millimetre thermal emission and scattered light gaps seen in recent observations of TW Hya are caused by planet-disc interactions. We perform global three-dimensional dusty smoothed particle hydrodynamics simulations, comparing synthetic observations of our models with dust thermal emission, CO emission and scattered light observations. We find that the dust gaps observed at 24 au and 41 au can be explained by two super-Earths ($\sim 4 \mathrm{M}_{\oplus}$). A planet of approximately Saturn-mass can explain the CO emission and the depth and width of the gap seen in scattered light at 94 au. Our model produces a prominent spiral arm while there are only hints of this in the data. To avoid runaway growth and migration of the planets we require a disc mass of $\lesssim 10^{-2}\,\mathrm{M}_{\odot}$ in agreement with CO observations but 10$-$100 times lower than the estimate from HD line emission.Comment: 6 pages, 5 figures, accepted for publication in MNRA

Spatial Gibbs random graphs

Many real-world networks of interest are embedded in physical space. We present a new random graph model aiming to reflect the interplay between the geometries of the graph and of the underlying space. The model favors configurations with small average graph distance between vertices, but adding an edge comes at a cost measured according to the geometry of the ambient physical space. In most cases, we identify the order of magnitude of the average graph distance as a function of the parameters of the model. As the proofs reveal, hierarchical structures naturally emerge from our simple modeling assumptions. Moreover, a critical regime exhibits an infinite number of discontinuous phase transitions.Comment: 29 pages, 5 figures. Revised from previous versio

NGC 6302: high-ionization permitted lines. Applying X-SSN synthesis to VLT-UVES spectra

A preliminary VLT-UVES spectrum of NGC 6302 (Casassus et al. 2002, MN), which hosts one of the hottest PN nuclei known (Teff ~ 220000 K; Wright et al. 2011, MN), has been recently analysed by means of X-SSN, a spectrum synthesis code for nebulae (Morisset and P\'equignot). Permitted recombination lines from highly-ionized species are detected/identified for the first time in a PN, and some of them probably for the first time in (Astro)Physics. The need for a homogeneous, high signal-to-noise UVES spectrum for NGC 6302 is advocated.Comment: Poster contribution (2 pages, 1 figure) to IAU Symposium 283: "Planetary Nebulae: An Eye to the Future" held in Puerto de la Cruz, Tenerife, Spain in July 25th-29th 201

Rencontres intellectuelles et changement social: Henri La Fontaine et la Belle Époque

info:eu-repo/semantics/publishe

Modeling Yield-Factor Volatility

The term structure of interest rates is often summarized using a handful of yield factors that capture shifts in the yield curve. Despite their wide application in financial economics, very little is known on the time-series properties of the yield-factor volatilities. We examine three common yield-factors: the level of short-term interest rates, the slope and curvature in the yield curve. We model the volatility dynamics in these yield factors using both GARCH and level effects and find that both are needed to adequately model yield-factor volatility. The level effect is routinely used when modeling volatility in short-term interest rates and we find that the level of the short-rate is useful in modeling the volatility of the slope and curvature too. We also examine the effect of volatility on the dynamics of the yield-factors and find that the GARCH-based volatility of the short-rate is negatively related to future interest rates and positively related to the slope of the yield curve. This volatility-in-mean effect is much weaker when a level effect is introduced. We also examine regime switching models that recognize different economic regimes and find that this dramatically improves the model's fit. Interestingly, the level effect is strengthened and the GARCH effects is weakened somewhat. The Bayesian information criteria suggests that the correct model is a regime-switching model with level effecC32, C51, G12

Slavnov-Taylor identities, non-commutative gauge theories and infrared divergences

In this work we clarify some properties of the one-loop IR divergences in non-Abelian gauge field theories on non-commutative 4-dimensional Moyal space. Additionally, we derive the tree-level Slavnov-Taylor identities relating the two, three and four point functions, and verify their consistency with the divergent one-loop level results. We also discuss the special case of two dimensions.Comment: 21 pages, 3 figures; v2: minor corrections and references adde