1,974 research outputs found
Outer planet probe cost estimates: First impressions
An examination was made of early estimates of outer planetary atmospheric probe cost by comparing the estimates with past planetary projects. Of particular interest is identification of project elements which are likely cost drivers for future probe missions. Data are divided into two parts: first, the description of a cost model developed by SAI for the Planetary Programs Office of NASA, and second, use of this model and its data base to evaluate estimates of probe costs. Several observations are offered in conclusion regarding the credibility of current estimates and specific areas of the outer planet probe concept most vulnerable to cost escalation
Non-Supersymmetric, Multi-Center Solutions with Topological Flux
We find an infinite class of non-supersymmetric multi-center solutions to the
STU model in five-dimensional ungauged supergravity coupled to two vector
multiplets. The solutions are obtained by solving a system of linear equations
on a class of Ricci-scalar-flat K\"ahler manifolds studied by LeBrun. After
imposing an additional U(1) isometry in the base, we solve the axisymmetric
Toda equation and obtain explicit supergravity solutions
containing arbitrary numbers of 2-cycles with cohomological fluxes of all three
flavors. This improves upon a previous result where only two of the three
fluxes were topologically non-trivial. Imposing regularity and absence of
closed timelike curves, we obtain "bubble equations" highly reminiscent of
those known in the supersymmetric case. Thus we extend much of the analysis
done for BPS bubbling solutions to this new family of non-supersymmetric
bubbling solutions.Comment: 51 pages, 8 figures, substantial changes made to improve analysis of
orbifold groups in sections 4,
A survey of multiple missions using gravity-assisted trajectories
Launch opportunities and advantages of gravity- assisted multiple missions to specific solar system target
Asteroid mission alternatives
The options for asteroid missions are evaluated within the constraints of existing or planned launch vehicles and low-thrust propulsion systems. A wide variety of missions is possible, including flyby, rendezvous, and even sample return. The multi-asteroid rendezvous concept requires an ion drive low-thrust propulsion system of the type being developed for a comet rendezvous. It is indicated that there are plentiful opportunities for such missions to visit four asteroids with stay times of 60-90 days each and with transit times between rendezvous of the order of a year
Hair-brane Ideas on the Horizon
We continue an examination of the microstate geometries program begun in
arXiv:1409.6017, focussing on the role of branes that wrap the cycles which
degenerate when a throat in the geometry deepens and a horizon forms. An
associated quiver quantum mechanical model of minimally wrapped branes exhibits
a non-negligible fraction of the gravitational entropy, which scales correctly
as a function of the charges. The results suggest a picture of AdS_3/CFT_2
duality wherein the long string that accounts for BTZ black hole entropy in the
CFT description, can also be seen to inhabit the horizon of BPS black holes on
the gravity side.Comment: 50 pages, 4 figures. v2: minor corrections, reference adde
Doubly-Fluctuating BPS Solutions in Six Dimensions
We analyze the BPS solutions of minimal supergravity coupled to an
anti-self-dual tensor multiplet in six dimensions and find solutions that
fluctuate non-trivially as a function of two variables. We consider families of
solutions coming from KKM monopoles fibered over Gibbons-Hawking metrics or,
equivalently, non-trivial T^2 fibrations over an R3 base. We find smooth
microstate geometries that depend upon many functions of one variable, but each
such function depends upon a different direction inside the T^2 so that the
complete solution depends non-trivially upon the whole T^2 . We comment on the
implications of our results for the construction of a general superstratum.Comment: 24 page
Violation of lepton flavour universality in composite Higgs models
We investigate whether the deviation from lepton flavour
universality in decays recently observed at the LHCb
experiment can be explained in minimal composite Higgs models. We show that a
visible departure from universality is indeed possible if left-handed muons
have a sizable degree of compositeness. Constraints from -pole observables
are avoided by a custodial protection of the muon coupling. The deficit in the
invisible width at LEP is explained in the same region of parameters.Comment: 5 pages, 2 figures. v4: discussion of invisible Z width adde
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