Multi-critical multi-field models: a CFT approach to the leading order

We present some general results for the multi-critical multi-field models in d>2 recently obtained using CFT and Schwinger-Dyson methods at perturbative level without assuming any symmetry. Results in the leading non trivial order are derived consistently for several conformal data in full agreement with functional perturbative RG methods. Mechanisms like emergent (possibly approximate) symmetries can be naturally investigated in this framework.Comment: 12 pages, 1 figure, Contribution to the Conference QFT2018, Quantum Fields From Fundamental Concepts to Phenomenological Questions, Mainz 26-28 September 201

Impact dynamics of mud flows against rigid walls

Mud flows represent one of the major causes of natural hazards in mountain regions. Similarly to debris flows, they consist of a hyper-concentrated mixture of water and sediments flowing down a slope and may cause serious damages to people and structures. The present paper investigates the force produced by a dam-break wave of mud impacting against a rigid wall. A power-law shearthinning model is used to describe the rheology of the hyper-concentrated mixture. A onedimensional shallow water model is adopted and a second-order Finite Volume scheme is employed to numerically solve the governing equations. The results indicate that depending on the fluid rheological parameters and on the bottom slope, there exists a minimum value of the wall distance above which the peak force does not exceed the asymptotic value of the hydrostatic final condition. For two different values of the channel slope, the dimensionless value of this lower bound is individuated for several values of the power-law exponent and of a dimensionless Basal Drag coefficient. An estimation of the maximum peak force for wall distance smaller than the minimum value is also provided

Critical models with N≤4 scalars in d=4-ϵ

We adopt a combination of analytical and numerical methods to study the renormalization group flow of the most general field theory with quartic interaction in d=4-ϵ with N=3 and N=4 scalars. For N=3, we find that it admits only three nondecomposable critical points: The Wilson-Fisher with O(3) symmetry, the cubic with H3=(Z2)3â ŠS3 symmetry, and the biconical with O(2)×Z2. For N=4, our analysis reveals the existence of new nontrivial solutions with discrete symmetries and with up to three distinct field anomalous dimensions

A multicritical Landau-Potts field theory

We investigate a perturbatively renormalizable Sq invariant model with N = q − 1 scalar field components below the upper critical dimension dc = 10/3. Our results hint at the existence of multicritical generalizations of the critical models of spanning random clusters and percolations in three dimensions. We also discuss the role of our multicritical model in a conjecture that involves the separation of first and second order phases in the (d, q) diagram of the Potts model

Symmetry and universality of multifield interactions in 6-ϵ dimensions

We outline a general strategy developed for the analysis of critical models, which we apply to obtain a heuristic classification of all universality classes with up to three field-theoretical scalar order parameters in d=6-ϵ dimensions. As expected by the paradigm of universality, each class is uniquely characterized by its symmetry group and by a set of its scaling properties, neither of which are built-in by the formalism but instead emerge nontrivially as outputs of our computations. For three fields, we find several solutions mostly with discrete symmetries. These are nontrivial conformal field theory candidates in less than six dimensions, one of which is a new perturbatively unitary critical model

First science results from SOFIA/FORCAST: The mid-infrared view of the compact HII region W3A

The massive star forming region W3 was observed with the faint object infrared camera for the SOFIA telescope (FORCAST) as part of the Short Science program. The 6.4, 6.6, 7.7, 19.7, 24.2, 31.5 and 37.1 \um bandpasses were used to observe the emission of Polycyclic Aromatic Hydrocarbon (PAH) molecules, Very Small Grains and Big Grains. Optical depth and color temperature maps of W3A show that IRS2 has blown a bubble devoid of gas and dust of $\sim$0.05 pc radius. It is embedded in a dusty shell of ionized gas that contributes 40% of the total 24 \um emission of W3A. This dust component is mostly heated by far ultraviolet, rather than trapped Ly$\alpha$ photons. This shell is itself surrounded by a thin ($\sim$0.01 pc) photodissociation region where PAHs show intense emission. The infrared spectral energy distribution (SED) of three different zones located at 8, 20 and 25\arcsec from IRS2, show that the peak of the SED shifts towards longer wavelengths, when moving away from the star. Adopting the stellar radiation field for these three positions, DUSTEM model fits to these SEDs yield a dust-to-gas mass ratio in the ionized gas similar to that in the diffuse ISM. However, the ratio of the IR-to-UV opacity of the dust in the ionized shell is increased by a factor $\simeq$3 compared to the diffuse ISM.Comment: Accepted for publication in ApJ letters; 13 pages, 3 figures 1 tabl

Aproximación al estudio de la calidad del aire: un modelo matemático

The arisen predictions of patterns are usually used in the industry to control their emission leVels. The entrance data for the models of quality of air are abundant and they include several environmental conditions: speed of the air, turbulence, temperature, density. This article regards the model of the quality of the air, considering advection and diffusion phenomena during the transport of a pollutant.Los modelos de calidad del aire están deinidos para predecir y simular las concentraciones de contaminantes del aire en un cierto periodo de tiempo. Las predicciones surgidas de los modelos suelen ser usadas por las industrias para controlar sus niveles de emisión. Los datos de entrada para los modelos de calidad de aire son abundantes y engloban varias condiciones ambientales: velocidad del aire, turbulencia, temperatura, densidad. Por ello, se utilizan condiciones ideales sobre la atmosfera, así como las reacciones químicas propias que subyacen al contaminante. &nbsp