Top pair production at CMS (includes charge asymmetry and ttbar resonance)

Measurements of top quark pair production are presented based on data recorded with the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) in 2011 and 2012. Inclusive and differential top quark pair production cross section measurements in various channels are described. Inclusive as well as differential measurements of the charge asymmetry in top quark pair events are summarised and a method for the extraction of the strong coupling alpha(s) from the measured top pair production cross section is discussed. All measurements are in agreement with the Standard Model predictions

Fisher Vectors Derived from Hybrid Gaussian-Laplacian Mixture Models for Image Annotation

In the traditional object recognition pipeline, descriptors are densely sampled over an image, pooled into a high dimensional non-linear representation and then passed to a classifier. In recent years, Fisher Vectors have proven empirically to be the leading representation for a large variety of applications. The Fisher Vector is typically taken as the gradients of the log-likelihood of descriptors, with respect to the parameters of a Gaussian Mixture Model (GMM). Motivated by the assumption that different distributions should be applied for different datasets, we present two other Mixture Models and derive their Expectation-Maximization and Fisher Vector expressions. The first is a Laplacian Mixture Model (LMM), which is based on the Laplacian distribution. The second Mixture Model presented is a Hybrid Gaussian-Laplacian Mixture Model (HGLMM) which is based on a weighted geometric mean of the Gaussian and Laplacian distribution. An interesting property of the Expectation-Maximization algorithm for the latter is that in the maximization step, each dimension in each component is chosen to be either a Gaussian or a Laplacian. Finally, by using the new Fisher Vectors derived from HGLMMs, we achieve state-of-the-art results for both the image annotation and the image search by a sentence tasks.Comment: new version includes text synthesis by an RNN and experiments with the COCO benchmar

Collisionless Isotropization of the Solar-Wind Protons by Compressive Fluctuations and Plasma Instabilities

Compressive fluctuations are a minor yet significant component of astrophysical plasma turbulence. In the solar wind, long-wavelength compressive slow-mode fluctuations lead to changes in $\beta_{\parallel \mathrm p}\equiv 8\pi n_{\mathrm p}k_{\mathrm B}T_{\parallel \mathrm p}/B^2$ and in $R_{\mathrm p}\equiv T_{\perp \mathrm p}/T_{\parallel \mathrm p}$, where $T_{\perp \mathrm p}$ and $T_{\parallel \mathrm p}$ are the perpendicular and parallel temperatures of the protons, $B$ is the magnetic field strength, and $n_{\mathrm p}$ is the proton density. If the amplitude of the compressive fluctuations is large enough, $R_{\mathrm p}$ crosses one or more instability thresholds for anisotropy-driven microinstabilities. The enhanced field fluctuations from these microinstabilities scatter the protons so as to reduce the anisotropy of the pressure tensor. We propose that this scattering drives the average value of $R_{\mathrm p}$ away from the marginal stability boundary until the fluctuating value of $R_{\mathrm p}$ stops crossing the boundary. We model this "fluctuating-anisotropy effect" using linear Vlasov--Maxwell theory to describe the large-scale compressive fluctuations. We argue that this effect can explain why, in the nearly collisionless solar wind, the average value of $R_{\mathrm p}$ is close to unity.Comment: 11 pages, published in Ap

Preventive Detention in American Theory and Practice

It is something of an article of faith in public and academic discourse that preventive detention runs counter to American values and law. This meme has become standard fare among human rights groups and in a great deal of legal scholarship. It treats the past nine years of extra-criminal detention of terrorism suspects as an extraordinary aberration from a strong American constitutional norm, under which government locks up citizens pursuant only to criminal punishment, not because of mere fear of their future acts. This argument further asserts that any statutory counterterrorism administrative detention regime would be a radical departure from this norm, an institutionalization of the aberration that the detention practices of the Bush and Obama years have represented. The more careful commentators acknowledge that the rule has exceptions – sometimes even many of them. But they describe these exceptions as narrow and limited, deviations from a generally strong rule that the American system tolerates to accommodate exceptional circumstances. The trouble with such civic mythology is that it is, ultimately, an inaccurate description of past practice, and thus a misleading indicator of the theory on which such practice rested. Our purpose in this paper is to describe just how mythological this particular civic myth is – indeed, to show that nearly every aspect of it is false: Preventive detention is not prohibited by U.S. law or especially frowned upon in tradition or practice. The circumstances in which it arises are not isolated exceptions to a strong rule against it; rather, they are relatively frequent. The federal government and all 50 states together possess a wide range of statutory preventive detention regimes that are frequently used, many of which provoke little social or legal controversy