1,733 research outputs found
Equivariant configuration spaces
The compression theorem is used to prove results for equivariant configuration spaces that are analogous to the well-known non-equivariant results of May, Milgram and Segal
James bundles
We study cubical sets without degeneracies, which we call {square}-sets. These sets arise naturally in a number of settings and they have a beautiful intrinsic geometry; in particular a {square}-set C has an infinite family of associated {square}-sets Ji(C), for i = 1, 2, ..., which we call James complexes. There are mock bundle projections pi: |Ji(C)| -> |C| (which we call James bundles) defining classes in unstable cohomotopy which generalise the classical James–Hopf invariants of {Omega}(S2). The algebra of these classes mimics the algebra of the cohomotopy of {Omega}(S2) and the reduction to cohomology defines a sequence of natural characteristic classes for a {square}-set. An associated map to BO leads to a generalised cohomology theory with geometric interpretation similar to that for Mahowald orientation
Selective Recovery of Corrugated Clippings
Selective recovery of waste corrugated into the kraft and NSSC fractions is gaining in popularity. This selective reuse of fibers enables the papermaker to use more recycled fiber in the linerboard portion of corrugated boxes. It is well documented that 100% recycled paper can be used in the medium while the highest percentage of secondary fibers in the linerboard is 30%. Greater than 30% recycled fiber in the linerboard results in poor runnability. Since reuse of secondary fibers in the medium is already at a maximum, this paper will place more emphasis on the reuse in the linerboard
Affine actions on non-archimedean trees
We initiate the study of affine actions of groups on -trees for a
general ordered abelian group ; these are actions by dilations rather
than isometries. This gives a common generalisation of isometric action on a
-tree, and affine action on an -tree as studied by I. Liousse. The
duality between based length functions and actions on -trees is
generalised to this setting. We are led to consider a new class of groups:
those that admit a free affine action on a -tree for some .
Examples of such groups are presented, including soluble Baumslag-Solitar
groups and the discrete Heisenberg group.Comment: 27 pages. Section 1.4 expanded, typos corrected from previous versio
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On the Expansions in Spin Foam Cosmology
We discuss the expansions used in spin foam cosmology. We point out that
already at the one vertex level arbitrarily complicated amplitudes contribute,
and discuss the geometric asymptotics of the five simplest ones. We discuss
what type of consistency conditions would be required to control the expansion.
We show that the factorisation of the amplitude originally considered is best
interpreted in topological terms. We then consider the next higher term in the
graph expansion. We demonstrate the tension between the truncation to small
graphs and going to the homogeneous sector, and conclude that it is necessary
to truncate the dynamics as well.Comment: 17 pages, 4 figures, published versio
Classical Knot Theory
This paper is a very brief introduction to knot theory. It describes knot
coloring by quandles, the fundamental group of a knot complement, and
handle-decompositions of knot complements.Comment: manuscript of paper in the journal Symmetry. There are some nice
pictures her
Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion Superconductor CeCoIn_5
Point-contact spectroscopy was performed on single crystals of the
heavy-fermion superconductor CeCoIn_5 between 150 mK and 2.5 K. A pulsed
measurement technique ensured minimal Joule heating over a wide voltage range.
The spectra show Andreev-reflection characteristics with multiple structures
which depend on junction impedance. Spectral analysis using the generalized
Blonder-Tinkham-Klapwijk formalism for d-wave pairing revealed two coexisting
order parameter components, with amplitudes Delta_1 = 0.95 +/- 0.15 meV and
Delta_2 = 2.4 +/- 0.3 meV, which evolve differently with temperature. Our
observations indicate a highly unconventional pairing mechanism, possibly
involving multiple bands.Comment: 4 pages, 3 figure
Topological Modes in Dual Lattice Models
Lattice gauge theory with gauge group is reconsidered in four
dimensions on a simplicial complex . One finds that the dual theory,
formulated on the dual block complex , contains topological modes
which are in correspondence with the cohomology group ,
in addition to the usual dynamical link variables. This is a general phenomenon
in all models with single plaquette based actions; the action of the dual
theory becomes twisted with a field representing the above cohomology class. A
similar observation is made about the dual version of the three dimensional
Ising model. The importance of distinct topological sectors is confirmed
numerically in the two dimensional Ising model where they are parameterized by
.Comment: 10 pages, DIAS 94-3
Some mixed Hodge structure on l^2-cohomology of covering of K\"ahler manifolds
We give methods to compute l^2-cohomology groups of a covering manifolds
obtained by removing pullback of a (normal crossing) divisor to a covering of a
compact K\"ahler manifold. We prove that in suitable quotient categories, these
groups admit natural mixed Hodge structure whose graded pieces are given by
expected Gysin maps.Comment: 40 pages. This revised version will be published in Mathematische
Annale
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