Spinning Witten Diagrams

We develop a systematic framework to compute the conformal partial wave expansions (CPWEs) of tree-level four-point Witten diagrams with totally symmetric external fields of arbitrary mass and integer spin in AdS$_{d+1}$. Employing this framework, we determine the CPWE of a generic exchange Witten diagram with spinning exchanged field. As an intermediate step, we diagonalise the linear map between spinning three-point conformal structures and spinning cubic couplings in AdS. As a concrete application, we compute all exchange diagrams in the type A higher-spin gauge theory on AdS$_{d+1}$, which is conjectured to be dual to the free scalar $O\left(N\right)$ model. Given a CFT$_d$, our results provide the complete holographic reconstruction of all cubic couplings involving totally symmetric fields in the putative dual theory on AdS$_{d+1}$.Comment: 41 pages, many figures. v2: Three self-contained pages removed from section 4, to be restored elsewhere. Main results unaffected. Refs added and typos fixe

Higher-Spin Gauge Theories and Bulk Locality

We present a no-go result on consistent Noether interactions among higher-spin gauge fields on anti-de Sitter space-times. We show that there is a non-local obstruction at the classical level to consistent interacting field theory descriptions of massless higher-spin particles that are described in the free limit by the free Fronsdal action, under the assumption that such theories arise from the gauging of a global higher-spin symmetry. Our result suggests that the Fronsdal programme for introducing interactions among higher-spin gauge fields cannot be completed without introducing new guiding principles, which could lie beyond the framework of classical field theory.Comment: 10 pages + refs. v2: Improved presentation, clarifications and references added. Some parts removed which just reviewed previous published work. To appear in Physical Review Letter

Feynman rules for higher-spin gauge fields on AdSd+1_{d+1}

We determine the Feynman rules for the minimal type A higher-spin gauge theory on AdS$_{d+1}$ at cubic order. In particular, we establish the quantum action at cubic order in de Donder gauge, including ghosts. We also give the full de Donder gauge propagators of higher-spin gauge fields and their ghosts. This provides all ingredients needed to quantise the theory at cubic order.Comment: v2: 32 pages, typos fixed, refs adde

Spinning AdS Loop Diagrams: Two Point Functions

We develop a systematic approach to evaluating AdS loop amplitudes based on the spectral (or "split") representation of bulk-to-bulk propagators, which re-expresses loop diagrams in terms of spectral integrals and higher-point tree diagrams. In this work we focus on 2pt one-loop Witten diagrams involving totally symmetric fields of arbitrary mass and integer spin. As an application of this framework, we study the contribution to the anomalous dimension of higher-spin currents generated by bubble diagrams in higher-spin gauge theories on AdS.Comment: 54+23 pages, 15 figures. v2: Section 2.2 added with more details on the analytic evaluation of anomalous dimensions from bubble diagrams. References added, matches published versio

Quartic AdS Interactions in Higher-Spin Gravity from Conformal Field Theory

Clarifying the locality properties of higher-spin gravity is a pressing task, but notoriously difficult due to the absence of a weakly-coupled flat regime. The simplest non-trivial case where this question can be addressed is the quartic self-interaction of the AdS scalar field present in the higher-spin multiplet. We investigate this issue in the context of the holographic duality between the minimal bosonic higher-spin theory on AdS$_4$ and the free $O\left(N\right)$ vector model in three dimensions. In particular, we determine the exact explicit form of the derivative expansion of the bulk scalar quartic vertex. The quartic vertex is obtained from the field theory four-point function of the operator dual to the bulk scalar, by making use of our previous results for the Witten diagrams of higher-spin exchanges. This is facilitated by establishing the conformal block expansions of both the boundary four-point function and the dual bulk Witten diagram amplitudes. We show that the vertex we find satisfies a generalised notion of locality.Comment: 40 pages plus appendices, 8 figure

Bulk quartic vertices from boundary four-point correlators

We present arguments which suggest that the bulk higher-spin gravity duals of weakly-coupled conformal field theories obey some refined notion of locality. In particular, we discuss the Mellin amplitude programme in this context. We focus on the $O(N)$ vector model and minimal higher-spin gravity as a paradigmatic example of such holographic dual pairs. We restrict ourselves to three- and four-point functions of scalar primary operators, but the qualitative conclusions are expected to hold for the generic case.Comment: 13 pages. Contribution to the proceedings of the "International Workshop on Higher Spin Gauge Theories" (4-6 November 2015, Singapore

New high-pressure phase and equation of state of Ce2Zr2O8

In this paper we report a new high-pressure rhombohedral phase of Ce2Zr2O8 observed from high-pressure angle-dispersive x-ray diffraction and Raman spectroscopy studies up to nearly 12 GPa. The ambient-pressure cubic phase of Ce2Zr2O8 transforms to a rhombohedral structure beyond 5 GPa with a feeble distortion in the lattice. Pressure evolution of unit-cell volume showed a change in compressibility above 5 GPa. The unit-cell parameters of the high-pressure rhombohedral phase at 12.1 GPa are ah = 14.6791(3) {\AA}, ch = 17.9421(5) {\AA}, V = 3348.1(1) {\AA}3. The structure relation between the parent cubic (P2_13) and rhombohedral (P3_2) phases were obtained by group-subgroup relations. All the Raman modes of the cubic phase showed linear evolution with pressure with the hardest one at 197 cm-1. Some Raman modes of the high-pressure phase have a non-linear evolution with pressure and softening of one low-frequency mode with pressure is found. The compressibility, equation of state, and pressure coefficients of Raman modes of Ce2Zr2O8 are also reported.Comment: 33 pages, 8 figures, 6 table

Creating Online Lessons: A Faculty Development Seminar Series

The World Wide Web is being used increasingly to deliver instruction in medical education. Consequently, there is a need to train faculty in developing and implementing online instruction. We developed and implemented a seminar series to teach faculty to create educationally sound, well designed online instruction. Instruction was delivered to 15 participants via a six session seminar on developing web based lessons, supplemented with web-based instruction. First, the participants learned the basics of instructional design via a web based module. They then completed content outlines for their online lessons prior to the first seminar. Lesson development, web site development and the use of a web based instructional shell to implement the online lessons were each taught in two two hour sessions. Eight participants developed online lessons and four actually implemented them. Feedback was mostly positive, with suggestions for improvement. All eight participants who completed the series said they would recommend it to their colleagues. Because a longitudinal workshop type of seminar series requires a large amount of participant time outside of class, a six month seminar series may be too long. It is important at the beginning of the series to help participants select topics suitable for online instruction and to help them narrow their topics. We may change the attendance guidelines so faculty would attend only the session on instructional design and have their staff attend the technical sessions on web site design, HTML editing and online course delivery systems. This would better match the actual practice of faculty designing the instruction and staff developing it

Testing and Analysis Correlation of Composite Sandwich Longitudinal Bonded Joints for Space Launch Vehicle Structures

The NASA Composite Technology for Exploration (CTE) Project has been developing and demonstrating critical composite technologies with a focus on joints; incorporating materials, design/analysis, manufacturing, and tests that utilize NASA expertise and capabilities. The CTE project has focused on the development of composite longitudinal bonded joint technologies for conical structures such as the SLS Payload Attach Fitting (PAF) due to challenging joint geometries and loads compared to cylindrical jointed structures. The CTE team selected and designed a double-lap composite bonded joint as the most advantageous longitudinal joint to advance for the CTE project. This paper reports on the longitudinal bonded joint sub-element test articles that were fabricated and tested for several loading conditions to test the capability of the bonded joint design. Test and analysis correlation to the sub-element test articles are presented in the paper

On-orbit structural dynamic performance of a 15-meter microwave radiometer antenna

The on-orbit structural dynamic performance of a microwave radiometer antenna for Earth science applications is addressed. The radiometer is one of the Earth-observing instruments aboard a proposed geostationary platform as part of the Mission to the Planet Earth. A sequential approach is presented for assessing the ability of an antenna structure to retain its geometric shape subject to a representative onboard disturbance. This approach includes establishing the structural requirements of the antenna, developing the structural and disturbance models, performing modal and forced response analyses, and evaluating the resulting distortions in terms of the antenna's ability to meet stringent structural performance requirements. Two antenna configurations are discussed: free-flying and platform-mounted. These configurations are analyzed for a representative disturbance function which simulates rotation of the subreflector in order to perform a raster-type scan of the Earth disk. Results show that the scanning maneuver modeled would not induce antenna structural errors outside the specified limits