65,287 research outputs found
The number of ramified coverings of the sphere by the double torus, and a general form for higher genera
An explicit expression is obtained for the generating series for the number
of ramified coverings of the sphere by the double torus, with elementary branch
points and prescribed ramification type over infinity. Thus we are able to
prove a conjecture of Graber and Pandharipande, giving a linear recurrence
equation for the number of these coverings with no ramification over infinity.
The general form of the series is conjectured for the number of these coverings
by a surface of arbitrary genus that is at least two.Comment: 14pp.; revised version has two additional results in Section
A proof of a conjecture for the number of ramified coverings of the sphere by the torus
An explicit expression is obtained for the generating series for the number
of ramified coverings of the sphere by the torus, with elementary branch points
and prescribed ramification type over infinity. This proves a conjecture of
Goulden, Jackson and Vainshtein for the explicit number of such coverings.Comment: 10 page
Search for nonpointing photons in the diphoton and ETmiss final state in root s=7 TeV proton-proton collisions using the ATLAS detector
A search has been performed for photons originating in the decay of a neutral long-lived particle, exploiting the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction of photons, as well as the calorimeter's excellent time resolution. The search has been made in the diphoton plus missing transverse energy final state, using the full data sample of 4.8 fb⁻¹ of 7 TeV proton-proton collisions collected in 2011 with the ATLAS detector at the LHC. No excess is observed above the background expected from Standard Model processes. The results are used to set exclusion limits in the context of gauge mediated supersymmetry breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying with a lifetime in excess of 0.25 ns into a photon and a gravitino.G. Aad ... P. Jackson ... N. Soni ... M. J. White ... et al. (ATLAS Collaboration
Transitive factorizations of permutations and geometry
We give an account of our work on transitive factorizations of permutations.
The work has had impact upon other areas of mathematics such as the enumeration
of graph embeddings, random matrices, branched covers, and the moduli spaces of
curves. Aspects of these seemingly unrelated areas are seen to be related in a
unifying view from the perspective of algebraic combinatorics. At several
points this work has intertwined with Richard Stanley's in significant ways.Comment: 12 pages, dedicated to Richard Stanley on the occasion of his 70th
birthda
Simulation of colloidal chain movements under a magnetic field
Short colloidal chains are simulated by the slithering-snake-algorithm on a
simple cubic lattice. The dipole character of the colloidal particles leads to
a long range dipole-dipole interaction. The solvent is simulated by the nearest
neighbor Ising model. The aligning of the dipoles under a magnetic field gives
rise to the chains to align on their part with the field direction.Comment: 3 pages for Int. J. Mod. Phys. C 16, issue
Resolving the structure of TiBe
There has been considerable controversy regarding the structure of
TiBe, which is variously reported as hexagonal and tetragonal. Lattice
dynamics simulations based on density functional theory show the tetragonal
phase space group to be more stable over all temperatures, while the
hexagonal phase exhibits an imaginary phonon mode, which, if followed, would
lead to the cell adopting the tetragonal structure. We then report the
predicted ground state elastic constants and temperature dependence of the bulk
modulus and thermal expansion for the tetragonal phase.Comment: In press at Acta Crystallographica B. Supplementary material appende
- …