10,745 research outputs found
Commissioning of the ATLAS Pixel Detector
The ATLAS pixel detector is a high precision silicon tracking device located
closest to the LHC interaction point. It belongs to the first generation of its
kind in a hadron collider experiment. It will provide crucial pattern
recognition information and will largely determine the ability of ATLAS to
precisely track particle trajectories and find secondary vertices. It was the
last detector to be installed in ATLAS in June 2007, has been fully connected
and tested in-situ during spring and summer 2008. It is currently in a
commissioning phase using cosmic-ray events. We present the highlights of the
past and future commissioning activities of the ATLAS pixel system.Comment: Poster at ICHEP08, Philadelphia, USA, July 2008. 3 pages, LaTeX, 2
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Poisson-Dirichlet statistics for the extremes of a log-correlated Gaussian field
We study the statistics of the extremes of a discrete Gaussian field with
logarithmic correlations at the level of the Gibbs measure. The model is
defined on the periodic interval , and its correlation structure is
nonhierarchical. It is based on a model introduced by Bacry and Muzy [Comm.
Math. Phys. 236 (2003) 449-475] (see also Barral and Mandelbrot [Probab. Theory
Related Fields 124 (2002) 409-430]), and is similar to the logarithmic Random
Energy Model studied by Carpentier and Le Doussal [Phys. Rev. E (3) 63 (2001)
026110] and more recently by Fyodorov and Bouchaud [J. Phys. A 41 (2008)
372001]. At low temperature, it is shown that the normalized covariance of two
points sampled from the Gibbs measure is either or . This is used to
prove that the joint distribution of the Gibbs weights converges in a suitable
sense to that of a Poisson-Dirichlet variable. In particular, this proves a
conjecture of Carpentier and Le Doussal that the statistics of the extremes of
the log-correlated field behave as those of i.i.d. Gaussian variables and of
branching Brownian motion at the level of the Gibbs measure. The method of
proof is robust and is adaptable to other log-correlated Gaussian fields.Comment: Published in at http://dx.doi.org/10.1214/13-AAP952 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
The branching Brownian motion seen from its tip
It has been conjectured since the work of Lalley and Sellke (1987) that the
branching Brownian motion seen from its tip (e.g. from its rightmost particle)
converges to an invariant point process. Very recently, it emerged that this
can be proved in several different ways (see e.g. Brunet and Derrida, 2010,
Arguin et al., 2010, 2011). The structure of this extremal point process turns
out to be a Poisson point process with exponential intensity in which each atom
has been decorated by an independent copy of an auxiliary point process. The
main goal of the present work is to give a complete description of the limit
object via an explicit construction of this decoration point process. Another
proof and description has been obtained independently by Arguin et al. (2011).Comment: 47 pages, 3 figure
Uniqueness of Ground States for Short-Range Spin Glasses in the Half-Plane
We consider the Edwards-Anderson Ising spin glass model on the half-plane with zero external field and a wide range of choices, including
mean zero Gaussian, for the common distribution of the collection J of i.i.d.
nearest neighbor couplings. The infinite-volume joint distribution
of couplings J and ground state pairs with periodic
(respectively, free) boundary conditions in the horizontal (respectively,
vertical) coordinate is shown to exist without need for subsequence limits. Our
main result is that for almost every J, the conditional distribution
is supported on a single ground state pair.Comment: 20 pages, 3 figure
Using the Schramm-Loewner evolution to explain certain non-local observables in the 2d critical Ising model
We present a mathematical proof of theoretical predictions made by Arguin and
Saint-Aubin, as well as by Bauer, Bernard, and Kytola, about certain non-local
observables for the two-dimensional Ising model at criticality by combining
Smirnov's recent proof of the fact that the scaling limit of critical Ising
interfaces can be described by chordal SLE(3) with Kozdron and Lawler's
configurational measure on mutually avoiding chordal SLE paths. As an extension
of this result, we also compute the probability that an SLE(k) path, k in
(0,4], and a Brownian motion excursion do not intersect.Comment: v1: 17 pages, 4 figures, to appear in J. Phys. A: Math. Theor
Spin Glass Computations and Ruelle's Probability Cascades
We study the Parisi functional, appearing in the Parisi formula for the
pressure of the SK model, as a functional on Ruelle's Probability Cascades
(RPC). Computation techniques for the RPC formulation of the functional are
developed. They are used to derive continuity and monotonicity properties of
the functional retrieving a theorem of Guerra. We also detail the connection
between the Aizenman-Sims-Starr variational principle and the Parisi formula.
As a final application of the techniques, we rederive the Almeida-Thouless line
in the spirit of Toninelli but relying on the RPC structure.Comment: 20 page
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