Vacuum Ambiguity in de Sitter Space at Strong Coupling

It is well known that in the weak coupling regime, quantum field theories in de Sitter space do not have a unique vacuum, but a class of vacua parametrized by a complex parameter $\alpha$, i.e., the so-called $\alpha$-vacua. In this article, using gauge/gravity duality, we calculate the symmetric two-point function of strongly coupled ${\cal N}=4$ supersymmetric Yang-Mills theory on $dS_3$. We find that there is a class of de Sitter invariant vacua, parametrized by a set of complex parameters $\{\alpha_{\nu}\}$.Comment: 17 pages in JHEP style, references adde

An Infinite-Dimensional Family of Black-Hole Microstate Geometries

We construct the first explicit, smooth, horizonless black-hole microstate geometry whose moduli space is described by an arbitrary function of one variable and is thus infinite-dimensional. This is achieved by constructing the scalar Green function on a simple D6 anti-D6 background, and using this Green function to obtain the fully back-reacted solution for a supertube with varying charge density in this background. We show that this supertube can store parametrically more entropy than in flat space, confirming the entropy enhancement mechanism that was predicted using brane probes. We also show that all the local properties of the fully back-reacted solution can, in fact, be obtained using the DBI action of an appropriate brane probe. In particular, the supergravity and the DBI analysis yield identical functional bubble equations that govern the relative locations of the centers. This indicates that there is a non-renormalization theorem that protects these functional equations as one moves in moduli space. Our construction creates configurations that are beyond the scope of recent arguments that appear to put strong limits on the entropy that can be found in smooth supergravity solutions.Comment: 46 pages, 1 figure, LaTe

Bi-local Construction of Sp(2N)/dS Higher Spin Correspondence

We derive a collective field theory of the singlet sector of the Sp(2N) sigma model. Interestingly the hamiltonian for the bilocal collective field is the same as that of the O(N) model. However, the large-N saddle points of the two models differ by a sign. This leads to a fluctuation hamiltonian with a negative quadratic term and alternating signs in the nonlinear terms which correctly reproduces the correlation functions of the singlet sector. Assuming the validity of the connection between O(N) collective fields and higher spin fields in AdS, we argue that a natural interpretation of this theory is by a double analytic continuation, leading to the dS/CFT correspondence proposed by Anninos, Hartman and Strominger. The bi-local construction gives a map into the bulk of de Sitter space-time. Its geometric pseudospin-representation provides a framework for quantization and definition of the Hilbert space. We argue that this is consistent with finite N grassmanian constraints, establishing the bi-local representation as a nonperturbative framework for quantization of Higher Spin Gravity in de Sitter space.Comment: 1 figur

Rudimentary G-Quadruplex-Based Telomere Capping In Saccharomyces Cerevisiae

Telomere capping conceals chromosome ends from exonucleases and checkpoints, but the full range of capping mechanisms is not well defined. Telomeres have the potential to form G-quadruplex (G4) DNA, although evidence for telomere G4 DNA function in vivo is limited. In budding yeast, capping requires the Cdc13 protein and is lost at nonpermissive temperatures in cdc13-1 mutants. Here, we use several independent G4 DNA-stabilizing treatments to suppress cdc13-1 capping defects. These include overexpression of three different G4 DNA binding proteins, loss of the G4 DNA unwinding helicase Sgs1, or treatment with small molecule G4 DNA ligands. In vitro, we show that protein-bound G4 DNA at a 3\u27 overhang inhibits 5\u27-\u3e 3\u27 resection of a paired strand by exonuclease I. These findings demonstrate that, at least in the absence of full natural capping, G4 DNA can play a positive role at telomeres in vivo

Enhanced Supersymmetry of Nonrelativistic ABJM Theory

We study the supersymmetry enhancement of nonrelativistic limits of the ABJM theory for Chern-Simons level $k=1,2$. The special attention is paid to the nonrelativistic limit (known as `PAAP' case) containing both particles and antiparticles. Using supersymmetry transformations generated by the monopole operators, we find additional 2 kinematical, 2 dynamical, and 2 conformal supercharges for this case. Combining with the original 8 kinematical supercharges, the total number of supercharges becomes maximal: 14 supercharges, like in the well-known PPPP limit. We obtain the corresponding super Schr\"odinger algebra which appears to be isomorphic to the one of the PPPP case. We also discuss the role of monopole operators in supersymmetry enhancement and partial breaking of supersymmetry in nonrelativistic limit of the ABJM theory.Comment: 22 pages, references added, version to appear in JHE

In Vitro Contraction of Cytokinetic Ring Depends on Myosin II but not on Actin Dynamics

10.1038/ncb2781Nature Cell Biology157853-859NCBI

Severe vitamin D deficiency in 6 Canadian First Nation formula-fed infants

Background. Rickets was first described in the 17th century and vitamin D deficiency was recognized as the underlying cause in the early 1900s. Despite this long history, vitamin D deficiency remains a significant health concern. Currently, vitamin D supplementation is recommended in Canada for breast fed infants. There are no recommendations for supplementation in formula-fed infants. Objective. The objective of this report is to bring attention to the risk of severe vitamin D deficiency in high risk, formula fed infants. Design. A retrospective chart review was used to create this clinical case series. Results. Severe vitamin D deficiency was diagnosed in six formula-fed infants over a two-and-a-half year period. All six infants presented with seizures and they resided in First Nation communities located at latitude 54 in the province of Manitoba. While these infants had several risk factors for vitamin D deficiency, they were all receiving cow's milk based formula supplemented with 400 IU/L of vitamin D. Conclusion. This report suggests that current practice with regards to vitamin D supplementation may be inadequate, especially for high-risk infants. Health care professionals providing service to infants in a similar situation should be aware of this preventable condition. Hopefully this would contribute to its prevention, diagnosis and management

A Cyclin-Dependent Kinase that Promotes Cytokinesis through Modulating Phosphorylation of the Carboxy Terminal Domain of the RNA Pol II Rpb1p Sub-Unit

In Schizosaccharomyces pombe, the nuclear-localized kinase, Lsk1p, promotes cytokinesis by positively regulating the Septation Initiation Network (SIN). Although a member of the cyclin-dependent kinase (CDK) family, neither a cyclin partner nor a physiological target has been identified. In this report we identify a cyclin, Lsc1p, that physically interacts and co-localizes with Lsk1p. Furthermore, lsk1Δ, lsc1Δ, as well as kinase-dead lsk1-K306R mutants, display highly similar cytokinesis defects. Lsk1p is related to CDKs that phosphorylate the carboxy-terminal domain (CTD) of the largest sub-unit of RNA polymerase II (Rpb1p). Interestingly, we find that Lsk1p and Lsc1p are required for phosphorylation of Ser-2 residues found in the heptad repeats of the CTD. To determine if Rpb1p could be a physiological target, we replaced the native rpb1 gene with a synthetic gene encoding a Rpb1p protein in which Ser-2 was substituted with the non-phosphorylatable amino-acid alanine in all heptads. Cells carrying this allele were similar to lsk1Δ mutants: They were viable, displayed genetic interactions with the SIN, and were unable to complete cytokinesis upon perturbation of the cell division machinery. We conclude that Ser-2 phosphorylation of the CTD heptads plays a novel physiological role in the regulation of cytokinesis