1,647 research outputs found
Symmetry of Anomalous Dimension Matrices for Colour Evolution of Hard Scattering Processes
In a recent paper, Dokshitzer and Marchesini rederived the anomalous
dimension matrix for colour evolution of scattering, first derived
by Kidonakis, Oderda and Sterman. They noted a weird symmetry that it possesses
under interchange of internal (colour group) and external (scattering angle)
degrees of freedom and speculated that this may be related to an embedding into
a context that correlates internal and external variables such as string
theory.
In this short note, I point out another symmetry possessed by all the colour
evolution anomalous dimension matrices calculated to date. It is more prosaic,
but equally unexpected, and may also point to the fact that colour evolution
might be understood in some deeper theoretical framework. To my knowledge it
has not been pointed out elsewhere, or anticipated by any of the authors
calculating these matrices. It is simply that, in a suitably chosen colour
basis, they are complex symmetric matrices.Comment: 3 page
The Energetic Implications of Using Deforming Reference Descriptions to Simulate the Motion of Incompressible, Newtonian Fluids
In this work the issue of whether key energetic properties (nonlinear,
exponential-type dissipation in the abscence of forcing and long-term stability
under conditions of time dependent loading) are automatically inherited by
deforming reference descriptions is resolved. These properties are intrinsic to
real flows and the conventional Navier-Stokes equations. A completely general
reference description of an incompressible, Newtonian fluid, which reconciles
the differences between opposing schools of thought in the literature is
derived for the purposes of this investigation.
The work subsequently focusses on establishing a class of time
discretisations which inherit these self-same energetic properties,
irrespective of the time increment employed. The findings of this analysis have
profound consequences for the use of certain classes of finite difference
schemes in the context of deforming references. It is significant that many
algorithms presently in use do not automatically inherit the fundamental
qualitative features of the dynamics. An `updated' approach as a means of
avoiding ever burgeoning deformation gradients and a still further simplified
implementation are further topics explored.Comment: 26 pages, 2 figures, lemma 2 proof correcte
Operationalizing interdisciplinary research-a model of co-production in organizational cognitive neuroscience
Status of major southern California marine sport fish species with management recommendations, based on analyses of catch and size composition data collected on board commercial passenger fishing vessels from 1985 through 1987
This report on the status of major southern California marine sport fish species, together with management recommendations, is based on analyses of catch and size composition data, which were collected on board Commercial Passenger Fishing Vessels (CPFV) from 1985 through
1987. The project was designed to determine the status of those fishes that support the CPFV industry, and to make management recommendations when deemed necessary.
We collected and analyzed data based on random, stratified, on-board sampling of weekday (excluding holidays), open CPFV's on a year-round basis. We sampled 1/2-day, 3/4-day, and full-day type trips at a level of 5%. The survey area extended from below the United States-Mexican
border to Point Arguello. Catch estimates were extrapolated to include weekday as well as weekend and holiday, open and chartered CPFV's.
We sampled 736 CPFV trips in 1985, 650 in 1986, and 631 in 1987. We encountered 180 species of fishes, including 49 species of rockfishes. We performed detailed analyses on 14 non-rockfish species and 12 rockfish species, as well as
all fishes as a group and all rockfishes as a group.
We found a moderate increase in total catch of combined fish species between this study and one in the mid-1970's, due primarily to sizeable increases in catches of Pacific mackerel, kelp bass, barred sand bass,
and barracuda. However, we also found that there has been more than a 50% decline in the CPFV rockfish catches, due primarily to substantial decreases in catches of bocaccio, chilipepper, and olive rockfish. We have recommended that the current 15-rockfish bag limit regulation be reduced to a 10-rockfish bag limit, and that additional and equitable conservation measures also be implemented on the commercial rockfish fishery. (385pp.
Inquiring how a lecturer keeps learning about their teaching:a personal case history on reflective imagination
In order to reverse the use of lecture-based teaching, it is argued that personal reflection can be used as part of the quality assurance process. This paper proposes one response to personal reflection - reflective imagination, which is summarised as an action plan with six activities. It combines two conceptual issues raised in the US, the need to think creatively about learning and the reflective mindset, and one issue raised in the UK, cultivating the entrepreneurial imagination. Reflective imagination is linked to wider social science research, the place of self and reflexivity in scholarship. Finally, a personal history case study is presented which records a visit to Harvard Business School. The visit implements the six activities associated with reflective imagination. This is a method paper exploring reflective imagination
A supersymmetric D-brane Model of Space-Time Foam
We present a supersymmetric model of space-time foam with two stacks of eight
D8-branes with equal string tensions, separated by a single bulk dimension
containing D0-brane particles that represent quantum fluctuations in the
space-time foam. The ground state configuration with static D-branes has zero
vacuum energy. However, gravitons and other closed-string states propagating
through the bulk may interact with the D0-particles, causing them to recoil and
the vacuum energy to become non zero. This provides a possible origin of dark
energy. Recoil also distorts the background metric felt by energetic massless
string states, which travel at less than the usual (low-energy) velocity of
light. On the other hand, the propagation of chiral matter anchored on the D8
branes is not affected by such space-time foam effects.Comment: 33 pages, latex, five figure
The Transformation Project:transferring knowledge to transform project management practice ESRC end of award report
Cache-Oblivious Persistence
Partial persistence is a general transformation that takes a data structure
and allows queries to be executed on any past state of the structure. The
cache-oblivious model is the leading model of a modern multi-level memory
hierarchy.We present the first general transformation for making
cache-oblivious model data structures partially persistent
Commercialization of Genetic Testing Services: The FDA, Market Forces, and Biological Tarot Cards
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