12,889 research outputs found
Masses of Open-Flavour Heavy-Light Hybrids from QCD Sum-Rules
We use QCD Laplace sum-rules to predict masses of open-flavour heavy-light
hybrids where one of the hybrid's constituent quarks is a charm or bottom and
the other is an up, down, or strange. We compute leading-order, diagonal
correlation functions of several hybrid interpolating currents, taking into
account QCD condensates up to dimension-six, and extract hybrid mass
predictions for all , as well as explore possible
mixing effects with conventional quark-antiquark mesons. Within theoretical
uncertainties, our results are consistent with a degeneracy between the
heavy-nonstrange and heavy-strange hybrids in all channels. We find a
similar mass hierarchy of , , and states (a state
lighter than essentially degenerate and states) in both the
charm and bottom sectors, and discuss an interpretation for the states.
If conventional meson mixing is present the effect is an increase in the hybrid
mass prediction, and we estimate an upper bound on this effect.Comment: 24 pages, 8 figures. Mass predictions updated from previous version
to reflect corrected sign error in sum rule analysis. Mixing analysis and
examination of higher weight sum-rules added. To be published in JHE
Calculating the inherent visual structure of a landscape (inherent viewshed) using high-throughput computing
This paper describes a method of calculating the inherent visibility at all locations in a landscape (‘total viewshed’) by making use of redundant computer cycles. This approach uses a simplified viewshed program that is suitable for use within a distributed environment, in this case managed by the Condor system. Distributing the calculation in this way reduced the calculation time of our example from an estimated 34 days to slightly over 25 hours using a cluster of 43 workstations. Finally, we discuss the example ‘total viewshed’ raster for the Avebury region, and briefly highlight some of its implications
Polarization modes for strong-field gravitational waves
Strong-field gravitational plane waves are often represented in either the
Rosen or Brinkmann forms. These forms are related by a coordinate
transformation, so they should describe essentially the same physics, but the
two forms treat polarization states quite differently. Both deal well with
linear polarizations, but there is a qualitative difference in the way they
deal with circular, elliptic, and more general polarization states. In this
article we will describe a general algorithm for constructing arbitrary
polarization states in the Rosen form.Comment: 4 pages. Prepared for the proceedings of ERE2010 (Granada, Spain
General polarization modes for the Rosen gravitational wave
Strong-field gravitational plane waves are often represented in either the
Rosen or Brinkmann forms. While these two metric ansatze are related by a
coordinate transformation, so that they should describe essentially the same
physics, they rather puzzlingly seem to treat polarization states quite
differently. Both ansatze deal equally well with + and X linear polarizations,
but there is a qualitative difference in they way they deal with circular,
elliptic, and more general polarization states. In this article we will develop
a general formalism for dealing with arbitrary polarization states in the Rosen
form of the gravitational wave metric, representing an arbitrary polarization
by a trajectory in a suitably defined two dimensional hyperbolic plane.Comment: V1: 12 pages, no figures. V2: still 12 pages, reformatted. Minor
technical edits, discussion of Riemann tensor added, two references added, no
significant physics changes. This version accepted for publication in
Classical and Quantum Gravit
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