Structure Constants of Defect Changing Operators on the 1/2 BPS Wilson Loop

We study three-point functions of operators on the $1/2$ BPS Wilson loop in planar $\mathcal{N}=4$ super Yang-Mills theory. The operators we consider are "defect changing operators", which change the scalar coupled to the Wilson loop. We first perform the computation at two loops in general set-ups, and then study a special scaling limit called the ladders limit, in which the spectrum is known to be described by a quantum mechanics with the SL(2,$\mathbb{R}$) symmetry. In this limit, we resum the Feynman diagrams using the Schwinger-Dyson equation and determine the structure constants at all order in the rescaled coupling constant. Besides providing an interesting solvable example of defect conformal field theories, our result gives invaluable data for the integrability-based approach to the structure constants.Comment: 31 pages + appendices; v2 References adde

Cosmic Microwave Background-Weak Lensing Correlation: Analytical and Numerical Study of Nonlinearity and Implications for Dark Energy

Evolution of density fluctuations yields secondary anisotropies in the cosmic microwave background ( CMB), which are correlated with the same density fluctuations that can be measured by weak lensing (WL) surveys. We study the CMB-WL correlation induced by the integrated Sachs-Wolfe (ISW) effect and its nonlinear extension, the Rees-Sciama (RS) effect, using analytical models as well as N-body simulations. We show that an analytical model based on the time derivative of matter power spectrum agrees with simulations. All-sky cosmic-variance-limited CMB and WL surveys allow us to measure the correlation from the nonlinear RS effect with high significance (50 sigma) for l(max) = 10(4) whereas forthcoming missions such as Planck and LSST are expected to yield 4 l p 10 1.5 sigma detections, on the assumption of that the point-source contributions are negligible. We find that the CMB-WL correlation has a characteristic scale which is sensitive to the nature of dark energy.Alfred P. Sloan FellowshipAstronom

Matter Distribution around Galaxies

We explore the mass distribution of material associated with galaxies from the observation of gravitational weak lensing for the galaxy mass correlation function with the aid of $N$-body simulations of dark matter. The latter is employed to unfold various contributions that contribute to the integrated line of sight mass density. We conclude that galaxies have no definite edges of the matter distribution, extending to the middle to neighbouring galaxies with the density profile roughly $r^{-2.4}$ beyond the virial radius. The mass distributed beyond the virial radius (gravitationally bound radius) explains the gap seen in the mass density estimates, the global value $\Omega_m\sim 0.27$ and typically $\Omega_{\rm gal} \sim 0.15$ from the luminosity density multiplied by the mass to light ratio. We suggest to use a physical method of gravitational lensing to characterise galaxy samples rather than characterise them with photometric means.Comment: 16 pages, 5 figures. ApJ accepte

Density functional theory calculations for investigation of atomic structures of 4H-SiC/SiO2_2 interface after NO annealing

We propose the atomic structures of the 4H-SiC/SiO$_2$ interface for the $a$, $m$, C, and Si faces after NO annealing. Our proposed structures preferentially form at the topmost layers of the SiC side of the interface, which agrees with the experimental finding of secondary-ion mass spectrometry, that is, the N atoms accumulate at the interface. In addition, the areal N-atom density is on the order of 10$^{14}$ atom/cm$^2$ for each plane, which is also consistent with the experimental result. Moreover, the electronic structure of the interface after NO annealing, in which the CO bonds are removed and the nitride layer only at the interface is inserted, is free from gap states, although some interface models before NO annealing include the gap states arising from the CO bonds near the valence band edge of the bandgap. Our results imply that NO annealing can contribute to the reduction in the density of interface defects by forming the nitride layer.Comment: 10 pages and 7 figure

Thorough elucidation of synthesis and structure of poly(glycerol) functionalized nanodiamonds

Poly(glycerol) (PG) is one of the most promising platforms for the surface modification of nanomaterials especially for in vivo applications. Since the “grafting-from” process is facile to functionalize the nanomaterial surface covalently through the ring-opening polymerization of glycidol (GD), it has been applied to a variety of nanomaterials. The resulting numerous hydroxy groups in the hyperbranched structure serve as scaffolds for further functionalization and provide good dispersibility under physiological conditions. On the other hand, nanodiamond (ND) is a nanomaterial most intensely worked with PG because of its prominent properties including fluorescence from color centers. Despite the wide-spread use, the process has not been extended to be scalable and controllable. In addition, the structural details of PG chain on ND surface are yet elusive. In this work, we develop more scalable and safer PG functionalization of NDs by dropwise-addition of GD to ethylene glycol (EG) suspension of ND. The resulting PG amount can be controlled or even estimated by the reaction conditions (weights of GD, ND and EG) and the ND properties (diameter and oxygen content). The structure of PG chain was qualitatively and quantitatively analyzed by ¹³C nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements. Based on these results, the structure of PG is elucidated

Size, polyglycerol grafting, and net surface charge of iron oxide nanoparticles determine their interaction and toxicity in Caenorhabditis elegans

The widespread application of engineered nanoparticles (NPs) in environmental remediation has raised public concerns about their toxicity to aquatic organisms. Although appropriate surface modification can mitigate the ecotoxicity of NPs, the lack of polymer coating to inhibit toxicity completely and the insufficient knowledge about charge effect hinder the development of safe nanomaterials. Herein, we explored the potential of polyglycerol (PG) functionalization in alleviating the environmental risks of NPs. Iron oxide NPs (ION) of 20, 100, and 200 nm sizes (IONS, IONM and IONL, respectively) were grafted with PG to afford ION-PG. We examined the interaction of ION and ION-PG with Caenorhabditis elegans (C. elegans) and found that PG suppressed non-specific interaction of ION with C. elegans to reduce their accumulation and to inhibit their translocation. Particularly, IONS-PG was completely excluded from worms of all developmental stages. By covalently introducing sulfate, carboxyl and amino groups onto IONS-PG, we further demonstrated that positively charged IONS-PG-NH3+ induced high intestinal accumulation, cuticle adhesion and distal translocation, whereas the negatively charged IONS-PG-OSO3– and IONS-PG-COO– were excreted out. Consequently, no apparent deleterious effects on brood size and life span were observed in worms treated by IONS-PG and IONS-PG bearing negatively charged groups. This study presents new surface functionalization approaches for developing ecofriendly nanomaterials