Higher rank Wilson loops from a matrix model

We compute the circular Wilson loop of N=4 SYM theory at large N in the rank k symmetric and antisymmetric tensor representations. Using a quadratic Hermitian matrix model we obtain expressions for all values of the 't Hooft coupling. At large and small couplings we give explicit formulae and reproduce supergravity results from both D3 and D5 branes within a systematic framework.Comment: 1+18 pages. 1 figure. Typos correcte

Is orbital angular momentum always conserved in spontaneous parametric down-conversion?

In the non-linear optical process of type-II spontaneous parametric down-conversion, we present on an experiment showing that the two-photon detection amplitude of the down-converted beams does not generally reproduce the transverse profile of the pump beam that carries non-zero orbital angular momentum. We explain this observation by that orbital angular momentum is not conserved in the type-II non-linear process due to the broken rotational symmetry of the Hamiltonian.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. Revise

Ultrafast switching of photonic entanglement

To deploy and operate a quantum network which utilizes existing telecommunications infrastructure, it is necessary to be able to route entangled photons at high speeds, with minimal loss and signal-band noise, and---most importantly---without disturbing the photons' quantum state. Here we present a switch which fulfills these requirements and characterize its performance at the single photon level; it exhibits a 200-ps switching window, a 120:1 contrast ratio, 1.5 dB loss, and induces no measurable degradation in the switched photons' entangled-state fidelity (< 0.002). Furthermore, because this type of switch couples the temporal and spatial degrees of freedom, it provides an important new tool with which to encode multiple-qubit states in a single photon. As a proof-of-principle demonstration of this capability, we demultiplex a single quantum channel from a dual-channel, time-division-multiplexed entangled photon stream, effectively performing a controlled-bit-flip on a two-qubit subspace of a five-qubit, two-photon state

Optical Characterization of Anodically Grown Silicon Dioxide Thin Films

In silicon-based fabrication processes, silicon dioxide (SiO2) thin film is most widely used insulating film in the manufacture of integrated/discrete devices and microelectro-mechanical systems (MEMS). Various techniques have been established for the synthesis of silicon dioxide thin films. However, anodic oxidation method offers key advantages over the high temperature processes such as low cost, simple experimental set-up, low temperature, etc. In the present work SiO2 thin films are developed on silicon using anodic oxidation technique at room temperature. Constant voltage mode is employed in order to investigate the effect of applied voltage and the electrolyte stirring on thickness, refractive index and chemical bonds of the as-grown oxide films. Spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR) are employed to characterize various properties of the as-grown oxide films. At the applied voltage of 250 V, the highest thickness of 134 nm is obtained. The oxides developed at higher voltages are slightly silicon rich. The present study is aimed to explore the applications of silicon anodic oxidation in MEMS/Microelectronics fabrication

Towards a New Spatial Representation of Bone Remodeling

Irregular bone remodeling is associated with a number of bone diseases such as osteoporosis and multiple myeloma. Computational and mathematical modeling can aid in therapy and treatment as well as understanding fundamental biology. Different approaches to modeling give insight into different aspects of a phenomena so it is useful to have an arsenal of various computational and mathematical models. Here we develop a mathematical representation of bone remodeling that can effectively describe many aspects of the complicated geometries and spatial behavior observed. There is a sharp interface between bone and marrow regions. Also the surface of bone moves in and out, i.e. in the normal direction, due to remodeling. Based on these observations we employ the use of a level-set function to represent the spatial behavior of remodeling. We elaborate on a temporal model for osteoclast and osteoblast population dynamics to determine the change in bone mass which influences how the interface between bone and marrow changes. We exhibit simulations based on our computational model that show the motion of the interface between bone and marrow as a consequence of bone remodeling. The simulations show that it is possible to capture spatial behavior of bone remodeling in complicated geometries as they occur \emph{in vitro} and \emph{in vivo}. By employing the level set approach it is possible to develop computational and mathematical representations of the spatial behavior of bone remodeling. By including in this formalism further details, such as more complex cytokine interactions and accurate parameter values, it is possible to obtain simulations of phenomena related to bone remodeling with spatial behavior much as \emph{in vitro} and \emph{in vivo}. This makes it possible to perform \emph{in silica} experiments more closely resembling experimental observations.Comment: Math. Biosci. Eng., 9(2), 201

Growth and etch rate study of low temperature anodic silicon dioxide thin films

Silicon dioxide (SiO2) thin films are most commonly used insulating films in the fabrication of silicon-based integrated circuits (ICs) and microelectromechanical systems (MEMS). Several techniques with different processing environments have been investigated to deposit silicon dioxide films at temperatures down to room temperature. Anodic oxidation of silicon is one of the low temperature processes to grow oxide films even below room temperature. In the present work, uniform silicon dioxide thin films are grown at room temperature by using anodic oxidation technique. Oxide films are synthesized in potentiostatic and potentiodynamic regimes at large applied voltages in order to investigate the effect of voltage, mechanical stirring of electrolyte, current density and the water percentage on growth rate, and the different properties of as-grown oxide films. Ellipsometry, FTIR, and SEM are employed to investigate various properties of the oxide films. A 5.25 Å/V growth rate is achieved in potentiostatic mode. In the case of potentiodynamic mode, 160 nm thickness is attained at 300 V. The oxide films developed in both modes are slightly silicon rich, uniform, and less porous. The present study is intended to inspect various properties which are considered for applications in MEMS and Microelectronic

Composition, productivity and impact of grazing on the biodiversity of a grazing land in Almora District

Biodiversity of Almora district is heavily affected in the areas with heavy grazing pressure, although moderate grazing enhanced the biodiversity of the area. In the present study site a total of 45 herbaceous species were present and therophytes were dominant among them. Live shoot biomass of plants varied from 175.0±3.5 to 1862.0±5.75 kg/ha and 87.0±3.25 to 1303.0±7.50 kg/ha in ungrazed and grazed plots respectively. Aboveground primary productivity was significantly higher on control plot (3082.2 kg/ha) over grazed plot (2644.0 kg/ha). The average bite frequency per hour was recorded maximum for goats (1106.5 bite/hr) and least for buffalos (920 bites/hr). The monthly dry matter consumption per animal was amounted to 157.15, 154.51, 68.66 and 61.34 kg for cow, buffalo, sheep and goat respectively under nomadic open grazing. The percent herbage exploitation was observed maximum by sheep (9.82%) and minimum by buffalo (8.75%)

All-optical switching of photonic entanglement

Future quantum optical networks will require the ability to route entangled photons at high speeds, with minimal loss and added in-band noise, and---most importantly---without disturbing the photons' quantum state. Here we present an all-optical switch which fulfills these requirements and characterize its performance at the single photon level. It exhibits a 200-ps switching window, 120:1 contrast, 1.5-dB loss, and induces no measurable degradation in the switched photons' entangled-state fidelity (< 0.002). As a proof-of-principle demonstration of its capability, we use the switch to demultiplex a single quantum channel from a dual-channel, time-division-multiplexed entangled photon stream. Furthermore, because this type of switch couples the temporal and spatial degrees of freedom, it provides an important new tool with which to encode multiple-qubit quantum states on a single photon