68 research outputs found
Weighing the Dark Matter Halo
The dark matter problem will be solved only when all of the dark matter is
accounted for. Although wimps may be discovered in direct detection experiments
soon, we will not know what fraction of the dark matter halo they compose until
we measure their local density. In this talk, I will offer a novel method to
determine the mass of a wimp from direct detection experiments alone using
kinematical consistency constraints. I will then describe a general method to
estimate the local density of wimps using both dark matter detection and hadron
collider data when it becomes available. These results were obtained in
collaboration with Gordon Kane at the University of Michigan.Comment: 6 pages, 2 figures. To appear in "IDM2004: The 5th International
Workshop on the Identification of Dark Matter", eds. N. Spooner and V.
Kudryavtse
Amplitudes at Infinity
We investigate the asymptotically large loop-momentum behavior of multi-loop
amplitudes in maximally supersymmetric quantum field theories in four
dimensions. We check residue-theorem identities among color-dressed leading
singularities in supersymmetric Yang-Mills theory to
demonstrate the absence of poles at infinity of all MHV amplitudes through
three loops. Considering the same test for supergravity leads
us to discover that this theory does support non-vanishing residues at infinity
starting at two loops, and the degree of these poles grow arbitrarily with
multiplicity. This causes a tension between simultaneously manifesting
ultraviolet finiteness---which would be automatic in a representation obtained
by color-kinematic duality---and gauge invariance---which would follow from
unitarity-based methods.Comment: 4+1+1 pages; 15 figures; details provided in ancillary Mathematica
file
Stratifying On-Shell Cluster Varieties: the Geometry of Non-Planar On-Shell Diagrams
The correspondence between on-shell diagrams in maximally supersymmetric
Yang-Mills theory and cluster varieties in the Grassmannian remains largely
unexplored beyond the planar limit. In this article, we describe a systematic
program to survey such 'on-shell varieties', and use this to provide a complete
classification in the case of . In particular, we find exactly 24
top-dimensional varieties and 10 co-dimension one varieties in ---up to
parity and relabeling of the external legs. We use this case to illustrate some
of the novelties found for non-planar varieties relative to the case of
positroids, and describe some of the features that we expect to hold more
generally.Comment: 35 pages, 70 figures, and 1 table; also included is a file with
explicit details for our classification. Signs corrected in two residue
theorems, and a new interpretation (and formula) given for the las
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