Parameterized Distributed Algorithms

In this work, we initiate a thorough study of graph optimization problems parameterized by the output size in the distributed setting. In such a problem, an algorithm decides whether a solution of size bounded by k exists and if so, it finds one. We study fundamental problems, including Minimum Vertex Cover (MVC), Maximum Independent Set (MaxIS), Maximum Matching (MaxM), and many others, in both the LOCAL and CONGEST distributed computation models. We present lower bounds for the round complexity of solving parameterized problems in both models, together with optimal and near-optimal upper bounds. Our results extend beyond the scope of parameterized problems. We show that any LOCAL (1+epsilon)-approximation algorithm for the above problems must take Omega(epsilon^{-1}) rounds. Joined with the (epsilon^{-1}log n)^{O(1)} rounds algorithm of [Ghaffari et al., 2017] and the Omega (sqrt{(log n)/(log log n)}) lower bound of [Fabian Kuhn et al., 2016], the lower bounds match the upper bound up to polynomial factors in both parameters. We also show that our parameterized approach reduces the runtime of exact and approximate CONGEST algorithms for MVC and MaxM if the optimal solution is small, without knowing its size beforehand. Finally, we propose the first o(n^2) rounds CONGEST algorithms that approximate MVC within a factor strictly smaller than 2

Optimal Distributed Covering Algorithms

We present a time-optimal deterministic distributed algorithm for approximating a minimum weight vertex cover in hypergraphs of rank f. This problem is equivalent to the Minimum Weight Set Cover problem in which the frequency of every element is bounded by f. The approximation factor of our algorithm is (f+epsilon). Let Delta denote the maximum degree in the hypergraph. Our algorithm runs in the congest model and requires O(log{Delta} / log log Delta) rounds, for constants epsilon in (0,1] and f in N^+. This is the first distributed algorithm for this problem whose running time does not depend on the vertex weights nor the number of vertices. Thus adding another member to the exclusive family of provably optimal distributed algorithms. For constant values of f and epsilon, our algorithm improves over the (f+epsilon)-approximation algorithm of [Fabian Kuhn et al., 2006] whose running time is O(log Delta + log W), where W is the ratio between the largest and smallest vertex weights in the graph. Our algorithm also achieves an f-approximation for the problem in O(f log n) rounds, improving over the classical result of [Samir Khuller et al., 1994] that achieves a running time of O(f log^2 n). Finally, for weighted vertex cover (f=2) our algorithm achieves a deterministic running time of O(log n), matching the randomized previously best result of [Koufogiannakis and Young, 2011]. We also show that integer covering-programs can be reduced to the Minimum Weight Set Cover problem in the distributed setting. This allows us to achieve an (f+epsilon)-approximate integral solution in O((1+f/log n)* ((log Delta)/(log log Delta) + (f * log M)^{1.01}* log epsilon^{-1}* (log Delta)^{0.01})) rounds, where f bounds the number of variables in a constraint, Delta bounds the number of constraints a variable appears in, and M=max {1, ceil[1/a_{min}]}, where a_{min} is the smallest normalized constraint coefficient. This improves over the results of [Fabian Kuhn et al., 2006] for the integral case, which combined with rounding achieves the same guarantees in O(epsilon^{-4}* f^4 * log f * log(M * Delta)) rounds

Optimal distributed covering algorithms

We present a time-optimal deterministic distributed algorithm for approximating a minimum weight vertex cover in hypergraphs of rank f. This problem is equivalent to the Minimum Weight Set Cover problem in which the frequency of every element is bounded by f. The approximation factor of our algorithm is (f+ε). Let Δ denote the maximum degree in the hypergraph. Our algorithm runs in the CONGEST model and requires O(logΔ/loglogΔ) rounds, for constants ε∈(0,1] and f∈N+. This is the first distributed algorithm for this problem whose running time does not depend on the vertex weights nor the number of vertices. Thus adding another member to the exclusive family of provably optimal distributed algorithms. For constant values of f and ε, our algorithm improves over the (f+ε)-approximation algorithm of Kuhn et al. (SODA, 2006)whose running time is O(logΔ+logW), where W is the ratio between the largest and smallest vertex weights in the graph. Our algorithm also achieves an f-approximation for the problem in O(flogn) rounds, improving over the classical result of Khuller et al. (J Algorithms, 1994) that achieves a running time of O(flog2n). Finally, for weighted vertex cover (f=2) our algorithm achieves a deterministic running time of O(logn), matching the randomized previously best result of Koufogiannakis and Young (Distrib Comput, 2011). We also show that integer covering-programs can be reduced to the Minimum Weight Set Cover problem in the distributed setting. This allows us to achieve an (f⌈log2(M)+1⌉+ε)-approximate integral solution in O((1+f/logn)⋅(logΔloglogΔ+(f⋅logM)1.01⋅logε−1⋅(logΔ)0.01)) rounds, where f bounds the number of variables in a constraint, Δ bounds the number of constraints a variable appears in, and M=max{1,⌈1/amin⌉}, where amin is the smallest normalized constraint coefficient

De l’agressivité à la maternité. Étude longitudinale sur 30 ans auprès de filles agressives devenues mères : trajectoires de leur agressivité durant l’enfance, indicateurs de leurs caractéristiques parentales et développement de leurs enfants

L’agressivité chez les filles tend à ne pas se manifester de la même façon que chez les garçons ; de plus, elle suit une trajectoire longitudinale particulière. Les filles agressives envers leurs pairs ne se caractérisent pas tant par leurs manifestations de délinquance et de criminalité ; elles s’orientent plutôt vers une trajectoire de troubles sociaux et de santé mentale qui, à terme, compromet leur avenir scolaire, social et professionnel, de même que leur état de santé physique. Les compétences parentales des filles agressives, de même que le fonctionnement de leur famille, peuvent aussi être affectées ; dans ce cas, c’est la socialisation, la santé et le développement de toute une nouvelle génération d’enfants qui sont menacés. La Concordia Longitudinal Risk Project (Enquête longitudinale sur les risques, Université Concordia) suit un échantillon intergénérationnel de 1 770 sujets vivant à Montréal, dont un sous-échantillon de plus de 200 filles dites très agressives, et le compare avec un échantillon de garçons agressifs et un groupe témoin composé d’enfants des deux sexes. Les participants sont suivis de l’enfance à l’âge adulte sur une période de 30 ans. Le présent article décrit les trajectoires à long terme des filles agressives et les conséquences de cette agressivité sur une large variété d’éléments psychosociaux et de santé comme la maternité et la transmission des risques à la prochaine génération. Plus particulièrement, nous souhaitons : (1) établir les trajectoires des filles qui mènent de l’agressivité dans l’enfance au développement négatif à l’âge adulte, (2) établir les indicateurs de santé et les facteurs physiologiques connexes qui comportent des risques pour les filles agressives et leurs enfants et (3) évaluer comment l’agressivité à l’enfance se répercute sur le rôle maternel et le développement de la prochaine génération. Enfin, les retombées de nos conclusions seront discutées.Childhood aggression in girls may take different forms and follow different longitudinal trajectories from those typical of aggressive boys. Even when overt delinquency and criminality are avoided, girls who are aggressive towards their peers may follow a life course involving continuing social and mental health problems. From a longterm perspective, academic, social, health, and occupational achievement are likely to be negatively affected. Family functioning and parenting abilities may also be compromised, placing the offspring of these girls, a subsequent generation, at risk for social, health, and developmental problems. The Concordia Longitudinal Risk Project, which follows an intergenerational sample of 1770 inner-city Montrealers, includes a sub-sample of over 200 highly aggressive girls, with comparison groups of aggressive boys and normative children of both genders. Participants have been followed over a 30-year period, from childhood into adulthood. The present paper describes the long-term trajectories and sequelae of girlhood aggression in the context of a broad range of negative psychosocial and health outcomes, including parenting and the inter generational transfer of risk to offspring. More specifically, (1) trajectories by which childhood aggression places girls at risk for negative developmental outcomes are outlined, (2) health behaviours and physiological correlates that signify risk to aggressive girls and their offspring are delineated, and (3) pathways through which girlhood aggression influences parenting and offspring development are elucidated. Implications of these findings are discussed

Whose Expertise Is It? Evidence for Autistic Adults as Critical Autism Experts

Autistic and non-autistic adults’ agreement with scientific knowledge about autism, how they define autism, and their endorsement of stigmatizing conceptions of autism has not previously been examined. Using an online survey, we assessed autism knowledge and stigma among 636 adults with varied relationships to autism, including autistic people and nuclear family members. Autistic participants exhibited more scientifically based knowledge than others. They were more likely to describe autism experientially or as a neutral difference, and more often opposed the medical model. Autistic participants and family members reported lower stigma. Greater endorsement of the importance of normalizing autistic people was associated with heightened stigma. Findings suggest that autistic adults should be considered autism experts and involved as partners in autism research

Frictional drag between quantum wells mediated by phonon exchange

We use the Kubo formalism to evaluate the contribution of acoustic phonon exchange to the frictional drag between nearby two-dimensional electron systems. In the case of free phonons, we find a divergent drag rate ($\tau_{D}^{-1}$). However, $\tau_{D}^{-1}$ becomes finite when phonon scattering from either lattice imperfections or electronic excitations is accounted for. In the case of GaAs quantum wells, we find that for a phonon mean free path $\ell_{ph}$ smaller than a critical value, imperfection scattering dominates and the drag rate varies as $ln (\ell_{ph}/d)$ over many orders of magnitude of the layer separation $d$. When $\ell_{ph}$ exceeds the critical value, the drag rate is dominated by coupling through an electron-phonon collective mode localized in the vicinity of the electron layers. We argue that the coupled electron-phonon mode may be observable for realistic parameters. Our theory is in good agreement with experimental results for the temperature, density, and $d$-dependence of the drag rate.Comment: 45 pages, LaTeX, 8 postscript file figure

Human Exposure following Mycobacterium tuberculosis Infection of Multiple Animal Species in a Metropolitan Zoo

From 1997 to 2000, Mycobacterium tuberculosis was diagnosed in two Asian elephants (Elephas maximus), three Rocky Mountain goats (Oreamnos americanus), and one black rhinoceros (Diceros bicornis) in the Los Angeles Zoo. DNA fingerprint patterns suggested recent transmission. An investigation found no active cases of tuberculosis in humans; however, tuberculin skin-test conversions in humans were associated with training elephants and attending an elephant necropsy

Simplified Models for LHC New Physics Searches

This document proposes a collection of simplified models relevant to the design of new-physics searches at the LHC and the characterization of their results. Both ATLAS and CMS have already presented some results in terms of simplified models, and we encourage them to continue and expand this effort, which supplements both signature-based results and benchmark model interpretations. A simplified model is defined by an effective Lagrangian describing the interactions of a small number of new particles. Simplified models can equally well be described by a small number of masses and cross-sections. These parameters are directly related to collider physics observables, making simplified models a particularly effective framework for evaluating searches and a useful starting point for characterizing positive signals of new physics. This document serves as an official summary of the results from the "Topologies for Early LHC Searches" workshop, held at SLAC in September of 2010, the purpose of which was to develop a set of representative models that can be used to cover all relevant phase space in experimental searches. Particular emphasis is placed on searches relevant for the first ~50-500 pb-1 of data and those motivated by supersymmetric models. This note largely summarizes material posted at http://lhcnewphysics.org/, which includes simplified model definitions, Monte Carlo material, and supporting contacts within the theory community. We also comment on future developments that may be useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results from "Topologies for Early LHC Searches" workshop (SLAC, September 2010). Supplementary material can be found at http://lhcnewphysics.or

Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration