Study of pseudorapidity dependence of the anisotropic flow with ALICE at the LHC

We report on the pseudo-rapidity dependence of the charged particle anisotropic flow in Pb-Pb collisions at 2.76 TeV. The measurement is done over a wide range of pseudo-rapidity, |\eta|<5 using the forward detectors of ALICE at the LHC. Results are obtained from two- and multi-particle correlation techniques with the latter being less sensitive to non-flow effects. Elliptic flow longitudinal scaling, comparison with RHIC data and AMPT model calculations for the LHC are discussed.Comment: 4 pages, 6 figures, Proceedings for Quark Matter 2012, Washington D.C., August 13-18, 201

Causal interpretation of stochastic differential equations

We give a causal interpretation of stochastic differential equations (SDEs) by defining the postintervention SDE resulting from an intervention in an SDE. We show that under Lipschitz conditions, the solution to the postintervention SDE is equal to a uniform limit in probability of postintervention structural equation models based on the Euler scheme of the original SDE, thus relating our definition to mainstream causal concepts. We prove that when the driving noise in the SDE is a L\'evy process, the postintervention distribution is identifiable from the generator of the SDE

Notes on the occupancy problem with infinitely many boxes: general asymptotics and power laws

This paper collects facts about the number of occupied boxes in the classical balls-in-boxes occupancy scheme with infinitely many positive frequencies: equivalently, about the number of species represented in samples from populations with infinitely many species. We present moments of this random variable, discuss asymptotic relations among them and with related random variables, and draw connections with regular variation, which appears in various manifestations.Comment: Published at http://dx.doi.org/10.1214/07-PS092 in the Probability Surveys (http://www.i-journals.org/ps/) by the Institute of Mathematical Statistics (http://www.imstat.org

Triaxial vs. Spherical Dark Matter Halo Profiles

When analysing dark matter halos forming in cosmological N-body simulations it is common practice to obtain the density profile utilizing spherical shells. However, it is also known that the systems under investigation are far from spherical symmetry and rather follow a triaxial mass distribution. In this study we present an estimator for the error introduced by spherically averaging an elliptical mass distribution. We systematically investigate the differences arising when using a triaxial density profile under the assumption of spherical symmetry. We show that the variance in the density can be as large as 50% in the outer parts of dark matter halos for extreme (but still credible) axis ratios of 0.55:0.67:1. The inner parts are less affected but still show a scatter at the 16% level for these prolate systems. For more moderate ellipticities, i.e. axis ratios of 0.73:0.87:1, the error is smaller but still as large as 10-20% depending on distance. We further provide a simple formula that allows to estimate this variance as a function of radius for arbitrary axis ratios. We conclude that highly prolate and/or oblate systems are better fit by analytical profiles that take into account the triaxial nature of cosmological objects.Comment: 4 pages. 3 figures, accepted for publication in PAS

Passage of radiation through wormholes

We investigate numerically the process of the passage of a radiation pulse through a wormhole and the subsequent evolution of the wormhole that is caused by the gravitational action of this pulse. The initial static wormhole is modeled by the spherically symmetrical Armendariz-Picon solution with zero mass. The radiation pulses are modeled by spherically symmetrical shells of self-gravitating massless scalar fields. We demonstrate that the compact signal propagates through the wormhole and investigate the dynamics of the fields in this process for both cases: collapse of the wormhole into the black hole and for the expanding wormhole.Comment: 18 Pages, 13 figures, minor typos corrected, updated reference

Modified Huffman Code for Lossless Compression and Bandwidth Optimization and Applying Genetic Algorithms to Generating Paintings Based on Images

This thesis contains two projects. A modified Huffman code is presented as a lossless method to compress common traffic types. We posit the usage of compression benefits instead of just frequency of occurrence, as is common in Huffman codes, as the priority of each node when constructing the Huffman tree. We show the effectiveness of this method on common data transmission types and describe what would be needed for adoption of this algorithm. We explore genetic algorithms as a method to create paintings based on images. We find a balance between computational work required and visually pleasing results to the algorithm, prioritizing aspects of the parameter space based on their impact on the painting and how they impact computational workload

Small polygons and toric codes

We describe two different approaches to making systematic classifications of plane lattice polygons, and recover the toric codes they generate, over small fields, where these match or exceed the best known minimum distance. This includes a [36,19,12]-code over F_7 whose minimum distance 12 exceeds that of all previously known codes.Comment: 9 pages, 4 tables, 3 figure

Presenting Distributive Laws

Distributive laws of a monad T over a functor F are categorical tools for specifying algebra-coalgebra interaction. They proved to be important for solving systems of corecursive equations, for the specification of well-behaved structural operational semantics and, more recently, also for enhancements of the bisimulation proof method. If T is a free monad, then such distributive laws correspond to simple natural transformations. However, when T is not free it can be rather difficult to prove the defining axioms of a distributive law. In this paper we describe how to obtain a distributive law for a monad with an equational presentation from a distributive law for the underlying free monad. We apply this result to show the equivalence between two different representations of context-free languages