17,327 research outputs found
The PDF method for turbulent combustion
Probability Density Function (PDF) methods provide a means of calculating the properties of turbulent reacting flows. They have been successfully applied to many turbulent flames, including some with finite rate kinetic effects. Here the methods are reviewed with an emphasis on computational issues and their application to turbulent combustion
The Complete Spectrum of the String
We obtain the complete physical spectrum of the string, for arbitrary
. The constraints freeze coordinates, while the remaining
coordinates appear in the currents only {\it via} their energy-momentum tensor.
The spectrum is then effectively described by a set of ordinary Virasoro-like
string theories, but with a non-critical value for the central charge and a
discrete set of non-standard values for the spin-2 intercepts. In particular,
the physical spectrum of the string includes the usual massless states of
the Virasoro string. By looking at the norms of low-lying states, we find
strong indications that all the strings are unitary.Comment: 28 page
The Interacting String
We present a procedure for computing gauge-invariant scattering amplitudes in
the string, and use it to calculate three-point and four-point functions.
We show that non-vanishing scattering amplitudes necessarily involve external
physical states with excitations of ghosts as well as matter fields. The
crossing properties of the four-point functions are studied, and it is shown
that the duality of the Virasoro string amplitudes generalises in the
string, with different sets of intermediate states being exchanged in different
channels. We also exhibit a relation between the scattering amplitudes of the
string and the fusion rules of the Ising model.Comment: (Revised version), 26 pages, Plain Tex, CTP TAMU-86/92, KUL-TF-92/4
On Sibling and Exceptional W Strings
We discuss the physical spectrum for strings based on the algebras ,
, , and . For a simply-laced string, we find a
connection with the unitary Virasoro minimal model, where is the
dual Coxeter number of the underlying Lie algebra. For the string based on
, we find a connection with the unitary super-Virasoro
minimal model.Comment: 16 page
Anchoring historical sequences using a new source of astro-chronological tie-points
The discovery of past spikes in atmospheric radiocarbon activity, caused by
major solar energetic particle events, has opened up new possibilities for
high-precision chronometry. The two spikes, or Miyake Events, have now been
widely identified in tree-rings that grew in the years 775 and 994 CE.
Furthermore, all other plant material that grew in these years would also have
incorporated the anomalously high concentrations of radiocarbon. Crucially,
some plant-based artefacts, such as papyrus documents, timber beams and linen
garments, can also be allocated to specific positions within long, currently
unfixed, historical sequences. Thus, Miyake Events represent a new source of
tie-points that could provide the means for anchoring early chronologies to the
absolute timescale. Here, we explore this possibility, outlining the most
expeditious approaches, the current challenges and obstacles, and how they
might best be overcome.Comment: 11 pages, accepted to Royal Society Proc
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