129,119 research outputs found
Candidate Members and Age Estimate of the Family of Kuiper Belt Object 2003 EL61
The collisional family of Kuiper belt object (KBO) 2003 EL61 opens the
possibility for many interesting new studies of processes important in the
formation and evolution of the outer solar system. As the first family in the
Kuiper belt, it can be studied using techniques developed for studying asteroid
families, although some modifications are necessary. Applying these modified
techniques allows for a dynamical study of the 2003 EL61 family. The velocity
required to change orbits is used to quantitatively identify objects near the
collision. A method for identifying family members that have potentially
diffused in resonances (like 2003 EL61) is also developed. Known family members
are among the very closest KBOs to the collision and two new likely family
members are identified: 2003 UZ117 and 1999 OY3. We also give tables of
candidate family members which require future observations to confirm
membership. We estimate that a minimum of ~1 GYr is needed for resonance
diffusion to produce the current position of 2003 EL61, implying that the
family is likely primordial. Future refinement of the age estimate is possible
once (many) more resonant objects are identified. The ancient nature of the
collision contrasts with the seemingly fresh surfaces of known family members,
suggesting that our understanding of outer solar system surfaces is incomplete.Comment: 22 pages, 5 figures, accepted to AJ, author's cv available at
http://www.gps.caltech.edu/~dari
Heat-transfer and pressure distributions for laminar separated flows downstream of rearward-facing steps with and without mass suction
Heat-transfer and pressure distributions were measured for laminar separated flows downstream of rearward-facing steps with and without mass suction. The flow conditions were such that the boundary-layer thickness was comparable to or larger than the step height. For both suction and no-suction cases, an increase in the step height resulted in a sharp decrease in the initial heat-transfer rates behind the step. Downstream, however, the heat transfer gradually recovered back to less than or near attached-flow values. Mass suction from the step base area increased the local heat-transfer rates; however, this effect was relatively weak for the laminar flows considered. Even removal of the entire approaching boundary layer raised the post-step heat-transfer rates only about 10 percent above the flatplate values. Post-step pressure distributions were found to depend on the entrainment conditions at separation. In the case of the solid-faced step, a sharp pressure drop behind the step was followed by a very short plateau and relatively fast recompression. For the slotted-step connected to a large plenum but without suction, the pressure drop at the base was much smaller and the downstream recompression more gradual than that for solid-faced step
Putting an Edge to the Poisson Bracket
We consider a general formalism for treating a Hamiltonian (canonical) field
theory with a spatial boundary. In this formalism essentially all functionals
are differentiable from the very beginning and hence no improvement terms are
needed. We introduce a new Poisson bracket which differs from the usual
``bulk'' Poisson bracket with a boundary term and show that the Jacobi identity
is satisfied. The result is geometrized on an abstract world volume manifold.
The method is suitable for studying systems with a spatial edge like the ones
often considered in Chern-Simons theory and General Relativity. Finally, we
discuss how the boundary terms may be related to the time ordering when
quantizing.Comment: 36 pages, LaTeX. v2: A manifest formulation of the Poisson bracket
and some examples are added, corrected a claim in Appendix C, added an
Appendix F and a reference. v3: Some comments and references adde
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