1,974 research outputs found

    Outer planet probe cost estimates: First impressions

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    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

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    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 SU(∞)SU(\infty) 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 Partner with the City of Cleveland

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    A survey of multiple missions using gravity-assisted trajectories

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    Launch opportunities and advantages of gravity- assisted multiple missions to specific solar system target

    Asteroid mission alternatives

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    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

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    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

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    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

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    We investigate whether the 2.6σ2.6\sigma deviation from lepton flavour universality in B+→K+ℓ+ℓ−B^+\to K^+\ell^+\ell^- 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 ZZ-pole observables are avoided by a custodial protection of the muon coupling. The deficit in the invisible ZZ 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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