Gravitational backreaction of anti-D branes in the warped compactification

We derive a low-energy effective theory for gravity with anti-D branes, which are essential to get de Sitter solutions in the type IIB string warped compactification, by taking account of gravitational backreactions of anti-D branes. In order to see the effects of the self-gravity of anti-D branes, a simplified model is studied where a 5-dimensional anti-de Sitter ({\it AdS}) spacetime is realized by the bulk cosmological constant and the 5-form flux, and anti-D branes are coupled to the 5-form field by Chern-Simon terms. The {\it AdS} spacetime is truncated by introducing UV and IR cut-off branes like the Randall-Sundrum model. We derive an effective theory for gravity on the UV brane and reproduce the familiar result that the tensions of the anti-D branes give potentials suppressed by the forth-power of the warp factor at the location of the anti-D branes. However, in this simplified model, the potential energy never inflates the UV brane, although the anti-D-branes are inflating. The UV brane is dominated by dark radiation coming from the projection of the 5-dimensional Weyl tensor, unless the moduli fields for the anti-D branes are stabilized. We comment on the possibility of avoiding this problem in a realistic string theory compactification.Comment: typos corrected, 11 pages, 3 figure

Numerical tests of AdS/CFT at strong coupling

We study various correlation functions (two and three point functions) in a large $N$ matrix model of six commuting matrices with a numerical Monte Carlo algorithm. This is equivalent to a model of a gas of particles in six dimensions with a confining quadratic potential and logarithmic repulsions at finite temperature, where we are measuring the leading order non-gaussianities in the thermal fluctuations. This is a simplified model of the low energy dynamics of N=4 SYM at strong coupling. We find strong evidence that the simplified matrix model matches with the dual gravitational description of three point functions in the AdS/CFT correspondence.Comment: 23 pages, 7 figures, revtex. v2: minor correction

Enhanced Eshelby twist on thin wurtzite InP nanowires and measurement of local crystal rotation

We have performed a detailed study of the lattice distortions of InP wurtzite nanowires containing an axial screw dislocation. Eshelby predicted that this kind of system should show a crystal rotation due to the dislocation induced torque. We have measured the twisting rate and the dislocation Burgers vector on individual wires, revealing that nanowires with a 10-nm radius have a twist up to 100% larger than estimated from elasticity theory. The strain induced by the deformation has a Mexican-hat-like geometry, which may create a tube-like potential well for carriers

Constraints on the pMSSM from LAT Observations of Dwarf Spheroidal Galaxies

We examine the ability for the Large Area Telescope (LAT) to constrain Minimal Supersymmetric Standard Model (MSSM) dark matter through a combined analysis of Milky Way dwarf spheroidal galaxies. We examine the Lightest Supersymmetric Particles (LSPs) for a set of ~71k experimentally valid supersymmetric models derived from the phenomenological-MSSM (pMSSM). We find that none of these models can be excluded at 95% confidence by the current analysis; nevertheless, many lie within the predicted reach of future LAT analyses. With two years of data, we find that the LAT is currently most sensitive to light LSPs (m_LSP < 50 GeV) annihilating into tau-pairs and heavier LSPs annihilating into b-bbar. Additionally, we find that future LAT analyses will be able to probe some LSPs that form a sub-dominant component of dark matter. We directly compare the LAT results to direct detection experiments and show the complementarity of these search methods.Comment: 24 pages, 9 figures, submitted to JCA

The BF Formalism for QCD and Quark Confinement

Using the BF version of pure Yang-Mills, it is possible to find a covariant representation of the 't Hooft magnetic flux operator. In this framework, 't Hooft's pioneering work on confinement finds an explicit realization in the continuum. Employing the Abelian projection gauge we compute the expectation value of the magnetic variable and find the expected perimeter law. We also check the area law behaviour for the Wilson loop average and compute the string tension which turns out to be of the right order of magnitude.Comment: Various changes, version to appear in Nucl.Phys.

Flow dynamics and mixing past pairs of confined microfluidic cylinders

Placing cylindrical obstacles in a micromixer is a promising means to enhance mass transport. However, there is still a lack of fundamental understanding on the effect of obstacle arrangement on the flow. The present work provides new experimental insights into confined inertia flows past two cylindrical pins, placed either in tandem or staggered arrangement in a Y-type micromixer, and their effect on mixing, through micro Particle Image Velocimetry (μPIV) and Laser Induced Fluorescence (μLIF) measurements. It is found that in such confined microfluidic environments, adding a second pin suppresses vortex-shedding for spacings less than 3.5-pin diameters in a tandem arrangement or 0.25-pin diameters in the staggered configurations. Vortex-shedding is found to enhance mixing in tandem configurations but not in staggered ones. The results highlight the important roles of both pin arrangement and flow instabilities in micromixer performance and can serve as a guide to micromixer design

E 1 Gap Of Wurtzite Inas Single Nanowires Measured By Means Of Resonant Raman Spectroscopy

Indium arsenide nanowires were synthesized with an intermixing of wurtzite and zincblende structure by chemical beam epitaxy with the vapor-liquid-solid mechanism. Resonant Raman spectroscopy of the transverse optical phonon mode at 215cm -1 reveals an E 1 gap of 2.47 eV which is assigned to the electronic band gap at the A point in the indium arsenide wurtzite phase. © 2011 American Institute of Physics.1399473474 Int. Union Pure Appl. Phys. (IUPAP C8 Comm.),Korean Ministry of Education, Science and Technology,Seoul Metropolitan Government,Office of Naval Research Global,Korea Tourism OrganizationDick, K.A., (2008) Prog. Cryst. Growth Charact. Mater., 54, pp. 138-173Milnes, A.G., Polyakov, A.Y., (1993) Mater. Sci. Eng. B, 18, pp. 237-259Dayeh, S.A., Susac, D., Kavanagh, K.L., Yu, E.T., Wang, D., (2009) Adv. Mater., 19, pp. 2102-2108Cardona, M., (1961) J. Appl. Phys., 32 (SUPPL.), pp. 2151-2155Antoci, S., Reguzzoni, E., Samoggia, G., (1970) Phys. Rev. Lett., 24, pp. 1304-1307Arguello, C.A., Rousseau, D.L., Porto, S.P.S., (1969) Phys. Rev., 181, pp. 1351-136

The Donaldson-Witten Invariants in Pure QCD with Order and Disorder 't Hooft-like Operators

We study the first-order formalism of pure four-dimensional ${\rm SU}(2)$ Yang--Mills theory with theta-term. We describe the Green functions associated to electric and magnetic flux operators \`a la 't~Hooft by means of gauge-invariant non-local operators. These Green functions are related to Witten's invariants of four-manifolds.Comment: 12 pages, LaTeX file, no macros used. Revised Versio