3,156 research outputs found
Higher Spin de Sitter Holography from Functional Determinants
We discuss further aspects of the higher spin dS/CFT correspondence. Using a
recent result of Dunne and Kirsten, it is shown how to numerically compute the
partition function of the free Sp(N) model for a large class of SO(3)
preserving deformations of the flat/round metric on R^3/S^3 and the source of
the spin-zero single-trace operator dual to the bulk scalar. We interpret this
partition function as a Hartle-Hawking wavefunctional. It has a local maximum
about the pure de Sitter vacuum. Restricting to SO(3) preserving deformations,
other local maxima (which exceed the one near the de Sitter vacuum) can peak at
inhomogeneous and anisotropic values of the late time metric and scalar
profile. Numerical experiments suggest the remarkable observation that, upon
fixing a certain average of the bulk scalar profile at I^+, the wavefunction
becomes normalizable in all the other (infinite) directions of the deformation.
We elucidate the meaning of double trace deformations in the context of dS/CFT
as a change of basis and as a convolution. Finally, we discuss possible
extensions of higher spin de Sitter holography by coupling the free theory to a
Chern-Simons term.Comment: 30 pages plus appendices; v2 references adde
Late-time Structure of the Bunch-Davies De Sitter Wavefunction
We examine the late time behavior of the Bunch-Davies wavefunction for
interacting light fields in a de Sitter background. We use perturbative
techniques developed in the framework of AdS/CFT, and analytically continue to
compute tree and loop level contributions to the Bunch-Davies wavefunction. We
consider self-interacting scalars of general mass, but focus especially on the
massless and conformally coupled cases. We show that certain contributions grow
logarithmically in conformal time both at tree and loop level. We also consider
gauge fields and gravitons. The four-dimensional Fefferman-Graham expansion of
classical asymptotically de Sitter solutions is used to show that the
wavefunction contains no logarithmic growth in the pure graviton sector at tree
level. Finally, assuming a holographic relation between the wavefunction and
the partition function of a conformal field theory, we interpret the
logarithmic growths in the language of conformal field theory.Comment: 41 pages, 1 figure, minor typos fixed, journal references adde
The Bag Semantics of Ontology-Based Data Access
Ontology-based data access (OBDA) is a popular approach for integrating and
querying multiple data sources by means of a shared ontology. The ontology is
linked to the sources using mappings, which assign views over the data to
ontology predicates. Motivated by the need for OBDA systems supporting
database-style aggregate queries, we propose a bag semantics for OBDA, where
duplicate tuples in the views defined by the mappings are retained, as is the
case in standard databases. We show that bag semantics makes conjunctive query
answering in OBDA coNP-hard in data complexity. To regain tractability, we
consider a rather general class of queries and show its rewritability to a
generalisation of the relational calculus to bags
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