13,199 research outputs found
Conformal field theories and compact curves in moduli spaces
We show that there are many compact subsets of the moduli space of
Riemann surfaces of genus that do not intersect any symmetry locus. This
has interesting implications for supersymmetric conformal field
theories in four dimensions.Comment: Update acknowledging recent development
Single-channel fits and K-matrix constraints
A K-matrix formalism is used to relate single-channel and multi-channel fits.
We show how the single-channel formalism changes as new hadronic channels
become accessible. These relations are compared to those commonly used to fit
pseudoscalar meson photoproduction data.Comment: 9 pages, 2 figures. A numerical example has been adde
Renormalization group maps for Ising models in lattice gas variables
Real space renormalization group maps, e.g., the majority rule
transformation, map Ising type models to Ising type models on a coarser
lattice. We show that each coefficient of the renormalized Hamiltonian in the
lattice gas variables depends on only a finite number of values of the
renormalized Hamiltonian. We introduce a method which computes the values of
the renormalized Hamiltonian with high accuracy and so computes the
coefficients in the lattice gas variables with high accuracy. For the critical
nearest neighbor Ising model on the square lattice with the majority rule
transformation, we compute over 1,000 different coefficients in the lattice gas
variable representation of the renormalized Hamiltonian and study the decay of
these coefficients. We find that they decay exponentially in some sense but
with a slow decay rate. We also show that the coefficients in the spin
variables are sensitive to the truncation method used to compute them.Comment: 22 pages, 9 color postscript figures; minor revisions in version
Some reports of snowfall from fog during the UK winter of 2008/09
Snowfall during anticyclonic, non-frontal, and foggy conditions is surprising. Because it is often not forecast, it can present a hazard to transport and modify the surface albedo. In this report, we present some observations of snowfall during conditions of freezing fog in the UK during the winter of 2008/09
How does Labour Mobility affect the Performance of Plants? The importance of relatedness and geographical proximity
This paper analyses the impact of skill portfolios and labour mobility on plant performance by means of a unique database that connects attributes of individuals to features of plants for the whole Swedish economy. We found that a portfolio of related competences at the plant level increases significantly productivity growth of plants, in contrast to plant portfolios consisting of either similar or unrelated competences. Based on the analysis of 101,093 job moves, we found that inflows of skills that are related to the existing knowledge base of the plant had a positive effect on plant performance, while the inflow of new employees with skills that are already present in the plant had a negative impact. Our analyses also show that geographical proximity influences the effect of different skill inflows. Inflows of unrelated skills only contribute positively to plant performance when these are recruited in the same region. Labour mobility across regions only has a positive effect on productivity growth of plants when this concerns new employees with related skills.Labour mobility; related variety; skill portfolio; plant performance; geographical proximi
Time-delay in a multi-channel formalism
We reexamine the time-delay formalism of Wigner, Eisenbud and Smith, which
was developed to analyze both elastic and inelastic resonances. An error in the
paper of Smith has propagated through the literature. We correct this error and
show how the results of Eisenbud and Smith are related. We also comment on some
recent time-delay studies, based on Smith's erroneous interpretation of the
Eisenbud result.Comment: 4 pages, no figure
The motif problem
Fix a choice and ordering of four pairwise non-adjacent vertices of a
parallelepiped, and call a motif a sequence of four points in R^3 that coincide
with these vertices for some, possibly degenerate, parallelepiped whose edges
are parallel to the axes. We show that a set of r points can contain at most
r^2 motifs. Generalizing the notion of motif to a sequence of L points in R^p,
we show that the maximum number of motifs that can occur in a point set of a
given size is related to a linear programming problem arising from hypergraph
theory, and discuss some related questions.Comment: 17 pages, 1 figur
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