National Research University – Higher School of Economics

About: National Research University – Higher School of Economics is a education organization based out in Moscow, Russia. It is known for research contribution in the topics: Population & Computer science. The organization has 12873 authors who have published 23376 publications receiving 256396 citations.

Structured Bayesian Pruning via Log-Normal Multiplicative Noise

Abstract: Dropout-based regularization methods can be regarded as injecting random noise with pre-defined magnitude to different parts of the neural network during training. It was recently shown that Bayesian dropout procedure not only improves generalization but also leads to extremely sparse neural architectures by automatically setting the individual noise magnitude per weight. However, this sparsity can hardly be used for acceleration since it is unstructured. In the paper, we propose a new Bayesian model that takes into account the computational structure of neural networks and provides structured sparsity, e.g. removes neurons and/or convolutional channels in CNNs. To do this we inject noise to the neurons outputs while keeping the weights unregularized. We establish the probabilistic model with a proper truncated log-uniform prior over the noise and truncated log-normal variational approximation that ensures that the KL-term in the evidence lower bound is computed in closed-form. The model leads to structured sparsity by removing elements with a low SNR from the computation graph and provides significant acceleration on a number of deep neural architectures. The model is easy to implement as it can be formulated as a separate dropout-like layer.

Evidence of a J/psi Lambda structure and observation of excited Xi(-) states in the Xi(-)(b) -> J/psi Lambda K- decay

Abstract: First evidence of a structure in the $J/\psi{\Lambda}$ invariant mass distribution is obtained from an amplitude analysis of$\Xi_b^-{\rightarrow}J/\psi{\Lambda}K^-$ decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of $3.1\sigma$ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be $4458.8\pm2.9^{+4.7}_{-1.1}$ MeV and $17.3\pm6.5^{+8.0}_{-5.7}$ MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited $\Xi^-$ states, $\Xi(1690)^-$ and $\Xi(1820)^-$, are seen for the first time in a $\Xi^-_b$ decay, and their masses and widths are measured with improved precision. The analysis is performed using $pp$ collision data corresponding to a total integrated luminosity of 9 fb$^{-1}$, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.

Quantitative historical analysis uncovers a single dimension of complexity that structures global variation in human social organization.

Abstract: Do human societies from around the world exhibit similarities in the way that they are structured, and show commonalities in the ways that they have evolved? These are long-standing questions that have proven difficult to answer. To test between competing hypotheses, we constructed a massive repository of historical and archaeological information known as “Seshat: Global History Databank.” We systematically coded data on 414 societies from 30 regions around the world spanning the last 10,000 years. We were able to capture information on 51 variables reflecting nine characteristics of human societies, such as social scale, economy, features of governance, and information systems. Our analyses revealed that these different characteristics show strong relationships with each other and that a single principal component captures around three-quarters of the observed variation. Furthermore, we found that different characteristics of social complexity are highly predictable across different world regions. These results suggest that key aspects of social organization are functionally related and do indeed coevolve in predictable ways. Our findings highlight the power of the sciences and humanities working together to rigorously test hypotheses about general rules that may have shaped human history.

Clustering: A Data Recovery Approach

Abstract: What Is Clustering Key Concepts Case Study Problems Bird's-Eye View What Is Data Key Concepts Feature Characteristics Bivariate Analysis Feature Space and Data Scatter Pre-Processing and Standardizing Mixed Data Similarity Data K-Means Clustering and Related Approaches Key Concepts Conventional K-Means Choice of K and Initialization of K-Means Intelligent K-Means: Iterated Anomalous Pattern Minkowski Metric K-Means and Feature Weighting Extensions of K-Means Clustering Overall Assessment Least-Squares Hierarchical Clustering Key Concepts Hierarchical Cluster Structures Agglomeration: Ward Algorithm Least-Squares Divisive Clustering Conceptual Clustering Extensions of Ward Clustering Overall Assessment Similarity Clustering: Uniform, Modularity, Additive, Spectral, Consensus and Single Linkage Key Concepts Summary Similarity Clustering Normalized Cut and Spectral Clustering Additive Clustering Consensus Clustering Single Linkage, Minimum Spanning Tree and Connected Components Overall Assessment Validation and Interpretation Key Concepts General: Internal and External Validity Testing Internal Validity Interpretation Aids in the Data Recovery Perspective Conceptual Description of Clusters Mapping Clusters to Knowledge Overall Assessment Least-Squares Data Recovery Clustering Models Key Concepts Statistics Modelling as Data Recovery K-Means as a Data Recovery Method Data Recovery Models for Hierarchical Clustering Data Recovery Models for Similarity Clustering Consensus and Ensemble Clustering Overall Assessment References Index

Transition from fireball to Poynting-flux-dominated outflow in the three-episode GRB 160625B

Abstract: The ejecta composition is an open question in gamma-ray burst (GRB) physics 1 . Some GRBs possess a quasi-thermal spectral component in the time-resolved spectral analysis 2 , suggesting a hot fireball origin. Others show a featureless non-thermal spectrum known as the Band function3–5, consistent with a synchrotron radiation origin5,6 and suggesting that the jet is Poynting-flux dominated at the central engine and probably in the emission region as well7,8. There are also bursts showing a sub-dominant thermal component and a dominant synchrotron component 9 , suggesting a probable hybrid jet composition 10 . Here, we report an extraordinarily bright GRB 160625B, simultaneously observed in gamma-ray and optical wavelengths, whose prompt emission consists of three isolated episodes separated by long quiescent intervals, with the durations of each sub-burst being approximately 0.8 s, 35 s and 212 s, respectively. Its high brightness (with isotropic peak luminosity Lp,iso ≈ 4 × 1053 erg s−1) allows us to conduct detailed time-resolved spectral analysis in each episode, from precursor to main burst and to extended emission. The spectral properties of the first two sub-bursts are distinctly different, allowing us to observe the transition from thermal to non-thermal radiation between well-separated emission episodes within a single GRB. Such a transition is a clear indication of the change of jet composition from a fireball to a Poynting-flux-dominated jet. The extremely bright GRB 160625B, consisting of three sub-bursts separated by quiescent intervals, shows a transition from thermal to non-thermal radiation that indicates a change of jet composition from a fireball to a Poynting-flux-dominated jet.