Search for supersymmetry in events with two leptons including a tau

Searches for new physics in events with hadronic jets, missing transverse energy, and two leptons of which at least one is a hadronically decaying tau are presented. The result is based on a data sample corresponding to an integrated luminosity of 1 \fbi at a center-of-mass energy of 7 TeV collected by the CMS experiment at the LHC. No significant excess with respect to the standard model predictions is found.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 3 pages, 1 figur

Testing a DBI model for the unification of dark matter and dark energy with Gamma-Ray Bursts

We study the range of consistency of a model based on a nonlinear scalar field Dirac-Born-Infeld action for the unification of dark matter and dark energy using Gamma-Ray Bursts at high-redshifts. We use the sample of 59 high-redshift GRBs reported by Wei (2010), calibrated at low redshifts with the Union 2 sample of SNe Ia, thus avoiding the circularity problem. In this analysis, we also include the CMB7-year data and the baryonic acoustic peak BAO. Besides, it is calculated the parameter of the equation of state $w$, the deceleration parameter $q_0$ and the redshift of the transition to the decelerate-accelerated phase $z_t$.Comment: 6 pages, to appear in Proceedings of Spanish Relativity Meeting 2011 (ERE 2011) held in Madrid, Spai

Large Dimensional Analysis and Optimization of Robust Shrinkage Covariance Matrix Estimators

This article studies two regularized robust estimators of scatter matrices proposed (and proved to be well defined) in parallel in (Chen et al., 2011) and (Pascal et al., 2013), based on Tyler's robust M-estimator (Tyler, 1987) and on Ledoit and Wolf's shrinkage covariance matrix estimator (Ledoit and Wolf, 2004). These hybrid estimators have the advantage of conveying (i) robustness to outliers or impulsive samples and (ii) small sample size adequacy to the classical sample covariance matrix estimator. We consider here the case of i.i.d. elliptical zero mean samples in the regime where both sample and population sizes are large. We demonstrate that, under this setting, the estimators under study asymptotically behave similar to well-understood random matrix models. This characterization allows us to derive optimal shrinkage strategies to estimate the population scatter matrix, improving significantly upon the empirical shrinkage method proposed in (Chen et al., 2011).Comment: Journal of Multivariate Analysi

Origin of Extended Star Clusters

We have discovered new extended star clusters (ESCs) in a nearby dIrr galaxy NGC 6822. These clusters are the nearest sample of ESCs available to date. The key characteristic of ESCs is their large size compared to typical globular clusters even though the two cluster populations are rather similar in terms of other parameters, i.e., color and luminosity. Several scenarios have been suggested to explain the formation of ESCs. However, the currently known ESCs may be a mixture of populations with heterogeneous formation histories. Future observational and theoretical studies are expected to better constrain the origins of ESCs as well as to increase their sample size.Comment: 3 pages, 1 figure, conference proceeding (with updated references) for 'Stellar Clusters & Associations: A RIA Workshop on Gaia' held in Granada, Spain, May 23 - 27, 2011; 2011 Stellar Clusters and Associations, Conference..357

Studies of the internal properties of jets and jet substructure with the ATLAS Detector

The internal structure of jets produced in pp collisions at the LHC is measured using the ATLAS detector in an inclusive jet sample corresponding to 35pb-1 of pp collisions at sqrt(s) = 7 TeV. Classical jet shape and energy flow measurements are complemented with measurements of new substructure observables with comparisons made to several leading order parton shower Monte Carlo programs. The jet invariant mass and \kt splitting scale are measured for anti-kt jets with a distance parameter of R=1.0 and Cambridge-Aachen jets with R=1.2. Furthermore, a splitting and filtering procedure is applied to the Cambridge-Aachen jets. These tools are then utilized for the first measurements of the filtered jet mass at the LHC in the inclusive jet sample as well the W+1 jet sample, in which a hadronic W mass peak is observed in the jet invariant mass spectrum. A sample of candidate boosted top quark events is also analyzed in detail for the jet substructure properties of hadronic "top-jets" in the final state.Comment: Proceedings of the EPS-HEP 2011 Conference, 21 - 27 July 2011, Grenoble, Rhone-Alpes, Franc

Energy Prices Jump While Food Prices Show Modest Increases

The Consumer Price Index (CPI) is a measure of the average change over time in the prices paid by urban consumers for a market basket of consumer goods and services. Produced monthly by the Bureau of Labor Statistics (BLS), the CPI uses a “market basket,” or a sample of goods and services that consumers purchase for day-to-day living, and weighs each item on the basis of the amount of spending reported by a sample of families and individuals. Widely used as a measure of inflation, the CPI provides information about price changes in the nation’s economy and can be used by government, business, labor, and private individuals as a guide to making economic decisions. Over the last 12 months, the index for all items less food and energy has slowly accelerated. In contrast, the all-items index has decelerated since a 12-month increase of 3.9 percent in September 2011. The September 2011 increase capped a run of steady acceleration in the all-items index that began in December 2010. Despite the contrast, the all-items index increased at a higher rate than the index for all items less food and energy in the first quarter of 2012. This summary compares price changes in the CPI for detailed categories of goods and services over the first quarter of 2012 with those in 2011

A saturation property of structures obtained by forcing with a compact family of random variables

A method how to construct Boolean-valued models of some fragments of arithmetic was developed in Krajicek (2011), with the intended applications in bounded arithmetic and proof complexity. Such a model is formed by a family of random variables defined on a pseudo-finite sample space. We show that under a fairly natural condition on the family (called compactness in K.(2011)) the resulting structure has a property that is naturally interpreted as saturation for existential types. We also give an example showing that this cannot be extended to universal types.Comment: preprint February 201