2,050 research outputs found
Analytical and Numerical Flash-Algorithms for Track Fits
Flash-algorithm track-reconstruction routines with speed factors 3000-4000 in
excess those of traditional iterative routines are presented.
The methods were successfully tested in the alignment of the Test Beam setup
for the ATLAS Pixel Detector
MCM-D modules yielding a
60 fold increase in alignment resolution over iterative routines, for the
same amount of alocated CPU time.Comment: 6 pages, 3 figure
Freed by interaction kinetic states in the Harper model
We study the problem of two interacting particles in a one-dimensional
quasiperiodic lattice of the Harper model. We show that a short or long range
interaction between particles leads to emergence of delocalized pairs in the
non-interacting localized phase. The properties of these Freed by Interaction
Kinetic States (FIKS) are analyzed numerically including the advanced Arnoldi
method. We find that the number of sites populated by FIKS pairs grows
algebraically with the system size with the maximal exponent , up to a
largest lattice size reached in our numerical simulations, thus
corresponding to a complete delocalization of pairs. For delocalized FIKS pairs
the spectral properties of such quasiperiodic operators represent a deep
mathematical problem. We argue that FIKS pairs can be detected in the framework
of recent cold atom experiments [M.~Schreiber {\it et al.} Science {\bf 349},
842 (2015)] by a simple setup modification. We also discuss possible
implications of FIKS pairs for electron transport in the regime of
charge-density wave and high superconductivity.Comment: 26 pages, 21 pdf and png figures, additional data and high quality
figures are available at http://www.quantware.ups-tlse.fr/QWLIB/fikspairs/ ,
parts of sections 2 and 3 moved to appendices, manuscript accepted for EPJ
Dynamical decoherence of a qubit coupled to a quantum dot or the SYK black hole
We study the dynamical decoherence of a qubit weakly coupled to a two-body
random interaction model (TBRIM) describing a quantum dot of interacting
fermions or the Sachdev-Ye-Kitaev (SYK) black hole model. We determine the
rates of qubit relaxation and dephasing for regimes of dynamical thermalization
of the quantum dot or of quantum chaos in the SYK model. These rates are found
to correspond to the Fermi golden rule and quantum Zeno regimes depending on
the qubit-fermion coupling strength. An unusual regime is found where these
rates are practically independent of TBRIM parameters. We push forward an
analogy between TBRIM and quantum small-world networks with an explosive
spreading over exponentially large number of states in a finite time being
similar to six degrees of separation in small-world social networks. We find
that the SYK model has approximately two-three degrees of separation.Comment: 17 pages, 15 pdf-figure
Poincar\'e recurrences and Ulam method for the Chirikov standard map
We study numerically the statistics of Poincar\'e recurrences for the
Chirikov standard map and the separatrix map at parameters with a critical
golden invariant curve. The properties of recurrences are analyzed with the
help of a generalized Ulam method. This method allows to construct the
corresponding Ulam matrix whose spectrum and eigenstates are analyzed by the
powerful Arnoldi method. We also develop a new survival Monte Carlo method
which allows us to study recurrences on times changing by ten orders of
magnitude. We show that the recurrences at long times are determined by
trajectory sticking in a vicinity of the critical golden curve and secondary
resonance structures. The values of Poincar\'e exponents of recurrences are
determined for the two maps studied. We also discuss the localization
properties of eigenstates of the Ulam matrix and their relation with the
Poincar\'e recurrences.Comment: 11 pages, 14 figures, high resolution figures and video mpeg files
available at: http://www.quantware.ups-tlse.fr/QWLIB/ulammethod
Hackathons: Why Co-Location?
This research was supported by the Arts and Humanities Research Council [grant Number AH/J005142/1].This research was supported by the Arts and Humanities Research Council [grant Number AH/J005142/1].This research was supported by the Arts and Humanities Research Council [grant Number AH/J005142/1].This research was supported by the Arts and Humanities Research Council [grant Number AH/J005142/1].In this position paper we outline and discuss co-location as a significant catalyst to knowledge exchange between participants for innovation at hackathon events. We draw on surveys and empirical evidence from participation in such events to conclude that the main incentives for participants are peer-to-peer learning and meaningful networking. We then consider why co-location provides an appropriate framework for these processes to occur, and emphasize the needs for future research in this area
Spectral properties of Google matrix of Wikipedia and other networks
We study the properties of eigenvalues and eigenvectors of the Google matrix
of the Wikipedia articles hyperlink network and other real networks. With the
help of the Arnoldi method we analyze the distribution of eigenvalues in the
complex plane and show that eigenstates with significant eigenvalue modulus are
located on well defined network communities. We also show that the correlator
between PageRank and CheiRank vectors distinguishes different organizations of
information flow on BBC and Le Monde web sites.Comment: 10 pages, 9 figure
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