International School for Advanced Studies

About: International School for Advanced Studies is a education organization based out in Trieste, Friuli-Venezia Giulia, Italy. It is known for research contribution in the topics: Galaxy & Dark matter. The organization has 3751 authors who have published 13433 publications receiving 588454 citations. The organization is also known as: SISSA & Scuola Internazionale Superiore di Studi Avanzati.

Two spin liquid phases in the spatially anisotropic triangular Heisenberg model

Abstract: The quantum spin-$1∕2$ antiferromagnetic Heisenberg model on a two dimensional triangular lattice geometry with spatial anisotropy is relevant to describe materials such as ${\mathrm{Cs}}_{2}\mathrm{Cu}{\mathrm{Cl}}_{4}$ and organic compounds such as $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{ET})}_{2}{\mathrm{Cu}}_{2}{(\mathrm{C}\mathrm{N})}_{3}$ The strength of the spatial anisotropy can increase quantum fluctuations and can destabilize the magnetically ordered state leading to nonconventional spin liquid phases In order to understand these intriguing phenomena, quantum Monte Carlo methods are used to study this model system as a function of the anisotropic strength, represented by the ratio ${J}^{\ensuremath{'}}∕J$ between the intrachain nearest neighbor coupling $J$ and the interchain one ${J}^{\ensuremath{'}}$ We have found evidence of two spin liquid regions The first one is stable for small values of the coupling ${J}^{\ensuremath{'}}∕J\ensuremath{\lesssim}065$, and appears gapless and fractionalized, whereas the second one is a more conventional spin liquid with a small spin gap and is energetically favored in the region $065\ensuremath{\lesssim}{J}^{\ensuremath{'}}∕J\ensuremath{\lesssim}08$ We have also shown that in both spin liquid phases there is no evidence of broken translation symmetry with dimer or spin-Peirls order or any broken spatial reflection symmetry of the lattice The various phases are in good agreement with the experimental findings, thus supporting the existence of spin liquid phases in two dimensional quantum spin-$1∕2$ systems

Search for production of vector-like quark pairs and of four top quarks in the lepton-plus-jets final state in pp collisions at √s = 8 TeV with the ATLAS detector

Abstract: A search for pair production of vector-like quarks, both up-type (T) and down-type (B), as well as for four-top-quark production, is presented. The search is based on pp collisions at TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 20.3 fb(-1). Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon with high transverse momentum, large missing transverse momentum and multiple jets. Dedicated analyses are performed targeting three cases: a T quark with significant branching ratio to a W boson and a b-quark , and both a T quark and a B quark with significant branching ratio to a Higgs boson and a third-generation quark ( respectively). No significant excess of events above the Standard Model expectation is observed, and 95% CL lower limits are derived on the masses of the vector-like T and B quarks under several branching ratio hypotheses assuming contributions from T -> Wb, Zt, Ht and B -> Wt, Zb, Hb decays. The 95% CL observed lower limits on the T quark mass range between 715 GeV and 950 GeV for all possible values of the branching ratios into the three decay modes, and are the most stringent constraints to date. Additionally, the most restrictive upper bounds on four-top-quark production are set in a number of new physics scenarios.

Genome-wide detection and analysis of hippocampus core promoters using DeepCAGE

Abstract: Finding and characterizing mRNAs, their transcription start sites (TSS), and their associated promoters is a major focus in post-genome biology. Mammalian cells have at least 5-10 magnitudes more TSS than previously believed, and deeper sequencing is necessary to detect all active promoters in a given tissue. Here, we present a new method for high-throughput sequencing of 5' cDNA tags-DeepCAGE: merging the Cap Analysis of Gene Expression method with ultra-high-throughput sequence technology. We apply DeepCAGE to characterize 1.4 million sequenced TSS from mouse hippocampus and reveal a wealth of novel core promoters that are preferentially used in hippocampus: This is the most comprehensive promoter data set for any tissue to date. Using these data, we present evidence indicating a key role for the Arnt2 transcription factor in hippocampus gene regulation. DeepCAGE can also detect promoters used only in a small subset of cells within the complex tissue.

Unsupervised Learning Methods for Molecular Simulation Data.

Abstract: Unsupervised learning is becoming an essential tool to analyze the increasingly large amounts of data produced by atomistic and molecular simulations, in material science, solid state physics, biophysics, and biochemistry. In this Review, we provide a comprehensive overview of the methods of unsupervised learning that have been most commonly used to investigate simulation data and indicate likely directions for further developments in the field. In particular, we discuss feature representation of molecular systems and present state-of-the-art algorithms of dimensionality reduction, density estimation, and clustering, and kinetic models. We divide our discussion into self-contained sections, each discussing a specific method. In each section, we briefly touch upon the mathematical and algorithmic foundations of the method, highlight its strengths and limitations, and describe the specific ways in which it has been used-or can be used-to analyze molecular simulation data.

Two-dimensional SCFTs from D3-branes

Abstract: We find a large class of two-dimensional $$ \mathcal{N} $$ = (0, 2) SCFTs obtained by compactifying four-dimensional $$ \mathcal{N} $$ = 1 quiver gauge theories on a Riemann surface. We study these theories using anomalies and c-extremization. The gravitational duals to these fixed points are new AdS3 solutions of IIB supergravity which we exhibit explicitly. Along the way we uncover a universal relation between the conformal anomaly coefficients of fourdimensional and two-dimensional SCFTs connected by an RG flow across dimensions. We also observe an interesting novel phenomenon in which the superconformal R-symmetry mixes with baryonic symmetries along the RG flow.