- Transitive reduction

by James Clough23 Sep 2014 16:14 - Corbino disk

by Kyrylo Snizhko25 Jul 2014 16:42 - Quantum-size electrostatic potential

by Prof. Michael V. Moskalets06 May 2014 17:44 - Dwyer-Fried invariant

by Prof. Alex Suciu15 Dec 2013 03:22 - General relativity

by Wilson Yu13 Dec 2013 04:40 - Neutrino Minimal Standard Model

by Prof. Mikhail Shaposhnikov10 Jan 2011 23:58 - Leptogenesis

by Dr. Sacha Davidson08 Dec 2010 13:32 - Fermi surface

by Dr. Vadim Cheianov05 Dec 2010 22:11 - Quantum shot noise

by Prof. Carlo Beenakker04 Feb 2014 08:52 - Kaluza-Klein dark matter

by Dr. Geraldine Servant05 Dec 2010 22:13

- We investigate the internal structure and density profiles of halos of mass $10^{10}-10^{14}~M_\odot$ in the Evolution and Assembly of Galaxies and their Environment (EAGLE) simulations. These follow the formation of galaxies in a $\Lambda$CDM Universe and include a treatment of the baryon physics thought to be relevant. The EAGLE simulations reproduce the observed present-day galaxy stellar mass function, as well as many other properties of the galaxy population as a function of time. We find significant differences between the masses of halos in the EAGLE simulations and in simulations that follow only the dark matter component. Nevertheless, halos are well described by the Navarro-Frenk-White (NFW) density profile at radii larger than ~5% of the virial radius but, closer to the centre, the presence of stars can produce cuspier profiles. Central enhancements in the total mass profile are most important in halos of mass $10^{12}-10^{13}M_\odot$, where the stellar fraction peaks. Over the radial range where they are well resolved, the resulting galaxy rotation curves are in very good agreement with observational data for galaxies with stellar mass $M_*<5\times10^{10}M_\odot$. We present an empirical fitting function that describes the total mass profiles and show that its parameters are strongly correlated with halo mass.SimulationsNavarro-Frenk-White profileGalaxyVirial massDark matterStarStellar massAGN feedbackStar formationBlack hole...
- The free decay of non-helical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales. Evolution of the magnetic energy spectrum $P_M(k,t)$ is self-similar in time and well modeled by a broken power law with sub-inertial and inertial range indices very close to $7/2$ and $-2$ respectively. The magnetic coherence scale is found to grow in time as $t^{2/5}$, much too slow to account for optical polarization of gamma-ray burst afterglow emission if magnetic energy is to be supplied only at microphysical length scales. No bursty or explosive energy loss is observed in relativistic MHD turbulence having modest magnetization, which constrains magnetic reconnection models for rapid time variability of GRB prompt emission, blazars and the Crab nebula.Magnetic energyInverse cascadeTurbulenceMagnetohydrodynamic turbulenceSimulationsRelativistic magnetohydrodynamicsSelf-similarityHelicityAfterglow emissionInitial value problem...
- We use high resolution simulations of the formation of the local group post-processed by a radiative transfer code for UV photons, to investigate the reionization of the satellite populations of an isolated Milky Way-M31 galaxy pair in a variety of scenarios. We use an improved version of ATON which includes a simple recipe for radiative feedback. In our baseline models, reionization is initiated by low mass, radiatively regulated haloes at high redshift, until more massive haloes appear, which then dominate and complete the reionization process. We investigate the relation between reionization history and present-day positions of the satellite population. We find that the average reionization redshift (zr) of satellites is higher near galaxy centers (MW and M31). This is due to the inside-out reionization patterns imprinted by massive haloes within the progenitor during the EoR, which end up forming the center of the galaxy. Thanks to incomplete dynamical mixing during galaxy assembly, these early patterns survive down to present day, resulting in a a clear radial gradient in the average satellites reionization redshift, up to the virial radius of MW and M31 and beyond. In the lowest emissivity scenario, the outer satellites are reionized about 180 Myr later than the inner satellites. This delay decreases with increasing source model emissivity, or in the case of external reionization by Virgo or M31, because reionization happens faster overall, and becomes spatially quasi-uniform at the highest emissivity.ReionizationMilky WaySimulationsAndromeda galaxyGalaxyReionization redshiftHistory of the reionizationStar formationStarLocal group...
- We investigate the prior dependence on the inferred spectrum of primordial tensor perturbations, in light of recent results from BICEP2 and taking into account a possible dust contribution to polarized anisotropies. We highlight an optimized parameterization of the tensor power spectrum, and adoption of a logarithmic prior on its amplitude $A_T$, leading to results that transform more evenly under change of pivot scale. In the absence of foregrounds the tension between the results of BICEP2 and Planck drives the tensor spectral index $n_T$ to be blue-tilted in a joint analysis, which would be in contradiction to the standard inflation prediction ($n_T<0$). When foregrounds are accounted for, the BICEP2 results no longer require non-standard inflationary parameter regions. We present limits on primordial $A_T$ and $n_T$, adopting foreground scenarios put forward by Mortonson & Seljak and motivated by Planck 353 GHz observations, and assess what dust contribution leaves a detectable cosmological signal. We find that if there is sufficient dust for the signal to be compatible with standard inflation, then the primordial signal is too weak to be robustly detected by BICEP2 if Planck+WMAP upper limits from temperature and E-mode polarization are correct.BICEP2AmplitudeModel of inflationTensor mode fluctuationsCosmologyB-modesPlanck missionWilkinson Microwave Anisotropy ProbeCosmic microwave backgroundCosmological parameters...
- The polarized thermal emission from Galactic dust is the main foreground present in measurements of the polarization of the cosmic microwave background (CMB) at frequencies above 100GHz. We exploit the Planck HFI polarization data from 100 to 353GHz to measure the dust angular power spectra $C_\ell^{EE,BB}$ over the range $40<\ell<600$. These will bring new insights into interstellar dust physics and a precise determination of the level of contamination for CMB polarization experiments. We show that statistical properties of the emission can be characterized over large fractions of the sky using $C_\ell$. For the dust, they are well described by power laws in $\ell$ with exponents $\alpha^{EE,BB}=-2.42\pm0.02$. The amplitudes of the polarization $C_\ell$ vary with the average brightness in a way similar to the intensity ones. The dust polarization frequency dependence is consistent with modified blackbody emission with $\beta_d=1.59$ and $T_d=19.6$K. We find a systematic ratio between the amplitudes of the Galactic $B$- and $E$-modes of 0.5. We show that even in the faintest dust-emitting regions there are no "clean" windows where primordial CMB $B$-mode polarization could be measured without subtraction of dust emission. Finally, we investigate the level of dust polarization in the BICEP2 experiment field. Extrapolation of the Planck 353GHz data to 150GHz gives a dust power $\ell(\ell+1)C_\ell^{BB}/(2\pi)$ of $1.32\times10^{-2}\mu$K$_{CMB}^2$ over the $40<\ell<120$ range; the statistical uncertainty is $\pm0.29$ and there is an additional uncertainty (+0.28,-0.24) from the extrapolation, both in the same units. This is the same magnitude as reported by BICEP2 over this $\ell$ range, which highlights the need for assessment of the polarized dust signal. The present uncertainties will be reduced through an ongoing, joint analysis of the Planck and BICEP2 data sets.AmplitudeCosmic microwave backgroundIntensityHigh Galactic latitudeDust emissionStatisticsSimulationsSpectral energy distributionStatistical errorCosmic microwave background polarization...
- We investigate the distribution of dark matter in galaxies by solving the equations of equilibrium of a self-gravitating system of massive fermions (`inos') at selected temperatures and degeneracy parameters within general relativity. The most general solutions present, as a function of the radius, a segregation of three physical regimes: 1) an inner core of almost constant density governed by degenerate quantum statistics; 2) an intermediate region with a sharply decreasing density distribution followed by an extended plateau, implying quantum corrections; 3) a decreasing density distribution $\rho\propto r^{-2}$ leading to flat rotation curves fulfilling the classical Boltzmann statistics. The mass of the inos is determined as an eigenfunction of the mass of the inner quantum cores. We compare and contrast this mass value with the lower limit on the particle mass by Tremaine and Gunn (1979), and show that the latter is approached for the less degenerate quantum cores in agreement with the fixed halo observables. Consequences of this alternative approach to the massive core in SgrA* and to dwarf galaxies are outlined.Rotation CurveGalaxyPhase space densityDark matter haloDark matterParticle massStatisticsDwarf galaxyBlack holeSpiral galaxy...
- We map the neutral atomic gas content of M33 using high resolution VLA and GBT observations and fit a tilted ring model to determine the orientation of the extended gaseous disk and its rotation curve. The disk of M33 warps from 8 kpc outwards without substantial change of its inclination with respect to the line of sight. Rotational velocities rise steeply with radius in the inner disk, reaching 100 km/s in 4 kpc, then the rotation curve becomes more perturbed and flatter with velocities as high as 120-130 km/s out to 23 kpc. We derive the stellar mass surface density map of M33's optical disk, via pixel -SED fitting methods based on population synthesis models, which highlights variations in the mass-to-light ratio. The stellar mass surface further out is estimated from deep images of outer disk fields. Stellar and gas maps are then used in the dynamical analysis of the rotation curve to constrain the dark matter distribution which is relevant at all radii. A dark matter halo with a Navarro-Frenk-White density profile in a LCDM cosmology, provides the best fit to the rotation curve for a dark halo concentration C=10 and a total halo mass of 4.3 10^{11}Msun. This imples a baryonic fraction of order 0.02 and the evolutionary history of this galaxy should account for loss of a large fraction of its original baryonic content.Rotation CurveTriangulum GalaxyStellar massGalaxyDark matter haloMass to light ratioDark matterStarHydrogen 21 cm lineSloan Digital Sky Survey...
- Quantum teleportation is a fundamental concept in quantum physics which now finds important applications at the heart of quantum technology including quantum relays, quantum repeaters and linear optics quantum computing (LOQC). Photonic implementations have largely focussed on achieving long distance teleportation due to its suitability for decoherence-free communication. Teleportation also plays a vital role in the scalability of photonic quantum computing, for which large linear optical networks will likely require an integrated architecture. Here we report the first demonstration of quantum teleportation in which all key parts - entanglement preparation, Bell-state analysis and quantum state tomography - are performed on a reconfigurable integrated photonic chip. We also show that a novel element-wise characterisation method is critical to mitigate component errors, a key technique which will become increasingly important as integrated circuits reach higher complexities necessary for quantum enhanced operation.QubitWave guideQuantum teleportationEntanglementSimulationsBell stateInterferometersQuantum computerArchitectureFock state...
- We have studied high temperature thermal behavior of 1H, 1H, 2H, 2H-Perfluorooctyl-trichlorosilane (FOTS) and Octyltrichlorosilane (OTS) molecules self assembled on titanium dioxide (TiO2) nanoparticles using advanced microscopy and spectroscopy technique such as Scanning Electron Microscope (SEM), Dynamic Light Scattering (DLS), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). FOTS SAM and OTS SAM coated TiO2 nanoparticles were heated to different temperature range from room temperature (RT) to 550oC. We characterized nano-microstructure and size distribution of FOTS SAM and OTS SAM coated TiO2 nanoparticles, which were heat-treated to different peak temperatures, using SEM and DLS techniques. The thermal stability and degradation of FOTS SAM and OTS SAM coated TiO2 were carried out using FTIR spectroscopy. We found that FOTS SAM on TiO2 is very stable up to 450oC and OTS on TiO2 is stable up to 250oC. Peak frequency, peak intensity and full width half maxima (FWHM) of symmetric and asymmetric CF2 and CH2 confirms our observation. In this study, we successfully synergized the surface and temperature sensitive characteristics of FOTS/OTS SAM and TiO2 nanoparticles in order to use them for highly demanding surface and temperature sensitive nanotechnology applicationsTiO2NanoparticleThermalisationDynamic light scatteringSelf-assemblyOxideIntensityFull width at half maximumFourier transform infrared spectroscopyTemperature...
- We report generation of electrical energy from nonlinear mechanical noises available in the ambient environment using optimized piezo transduction mechanisms. Obtaining energy from an ambient vibration has been attractive for remotely installed standalone microsystems and devices. The mechanical noises in the ambient environment can be converted to electrical energy by a piezo strip based on the principle of piezoelectric effect. In this work, we have designed and developed a standalone energy harvesting module based on piezo transduction mechanisms. Using this designed module we harvested noise energy and stored electrical energy in a capacitor. Using NI-PXI workstation with a LabVIEW programming, the output voltage of the piezo strip and voltage of the capacitor were measured and monitored. In this paper we discuss about the design, development, implementation, performance and characteristics of the energy harvesting module.Energy harvestingTransductionCapacitorLabVIEWVibrationPiezoelectric effectElectrical energyEnergyMeasurement...
- Precision control of quantum systems is the driving force for both quantum technology and the probing of physics at the quantum and nano-scale. We propose an implementation independent method for in situ quantum control that leverages recent advances in the direct estimation of quantum gate fidelity. Our algorithm takes account of the stochasticity of the problem and is suitable for closed-loop control and requires only a constant number of fidelity estimating experiments per iteration independent of the dimension of the control space. It is efficient and robust to both statistical and technical noise.SimulationsStatisticsHamiltonianQubitQuantum gateStochastic optimizationQuantum computerQuantum technologyQuantum devicesSummarization...
- Achieving individual qubit readout is a major challenge in the development of scalable superconducting quantum processors. We have implemented the multiplexed readout of a four transmon qubit circuit using non-linear resonators operated as Josephson bifurcation amplifiers. We demonstrate the simultaneous measurement of Rabi oscillations of the four transmons. We find that multiplexed Josephson bifurcation is an high-fidelity readout method, the scalability of which is not limited by the need of a large bandwidth nearly quantum-limited amplifier as is the case with linear readout resonators.QubitRelaxationBifurcationSuperconductivityThermalisationExcited stateRelaxation timeQuantum coherenceNumerical simulationSummarization...
- Motivated by empirical data, we develop a statistical description of the queue dynamics for large tick assets based on a two-dimensional Fokker-Planck (diffusion) equation, that explicitly includes state dependence, i.e. the fact that the drift and diffusion depends on the volume present on both sides of the spread. "Jump" events, corresponding to sudden changes of the best limit price, must also be included as birth-death terms in the Fokker-Planck equation. All quantities involved in the equation can be calibrated using high-frequency data on best quotes. One of our central finding is the the dynamical process is approximately scale invariant, i.e., the only relevant variable is the ratio of the current volume in the queue to its average value. While the latter shows intraday seasonalities and strong variability across stocks and time periods, the dynamics of the rescaled volumes is universal. In terms of rescaled volumes, we found that the drift has a complex two-dimensional structure, which is a sum of a gradient contribution and a rotational contribution, both stable across stocks and time. This drift term is entirely responsible for the dynamical correlations between the ask queue and the bid queue.Fokker-Planck equationStatisticsDiffusion coefficientStationary distributionScale invarianceMaster equationLiquidsNumerical simulationStatistical significanceEvolution equation...
- Computers understand very little of the meaning of human language. This profoundly limits our ability to give instructions to computers, the ability of computers to explain their actions to us, and the ability of computers to analyse and process text. Vector space models (VSMs) of semantics are beginning to address these limits. This paper surveys the use of VSMs for semantic processing of text. We organize the literature on VSMs according to the structure of the matrix in a VSM. There are currently three broad classes of VSMs, based on term-document, word-context, and pair-pattern matrices, yielding three classes of applications. We survey a broad range of applications in these three categories and we take a detailed look at a specific open source project in each category. Our goal in this survey is to show the breadth of applications of VSMs for semantics, to provide a new perspective on VSMs for those who are already familiar with the area, and to provide pointers into the literature for those who are less familiar with the field.Vector spaceSurveysLanguageFrequencyFieldAction...
- We report a gas flow driven voltage generation of Octyltrichlorosilane (OTS) molecules self assembled on silicon wafers (Si wafers). OTS Self assembled Monolayer (SAM) has been coated on both p-type and n-type doped silicon wafers (p-Si and n-Si wafers) using dip coating method. We have measured the flow induced voltage generation on OTS SAM coated Si wafers/ Uncoated Si wafers at modest gas flow velocities of subsonic regime (Mach number < 0.2) using national instruments NI-PXI-1044 Workstation. The gas flow driven voltage generation is mainly due to the interplay mechanisms of Bernoulli principle and Seebeck effect. The surface morphology of OTS SAM coated p-Si and n-Si wafers were characterized by SEM analysis. In this study, our results shows that OTS SAM coated p-Si and n-Si wafers shows better sensitivity towards nitrogen gas flow when compared with the uncoated Si wafers. OTS SAM also exhibits high thermal stability and hydrophobicity.DopingThermalisationSelf-assemblySelf-assembled monolayerMach numberBernoulli's principleGasMeasurementVelocity...
- The discovery by the ATLAS and CMS experiments of a new boson with mass around 125 GeV/c2 and properties compatible with those of a Standard-Model Higgs boson, coupled with the absence of discoveries of phenomena beyond the Standard Model up to scales of several hundreds GeV, has triggered interest in ideas for future Higgs factories. A new circular e+e- collider hosted in a 80- to 100-km tunnel, TLEP, is among the most attractive solutions proposed so far. It has a clean experimental environment, produces high luminosity for top-quark, Higgs boson, W and Z studies, accommodates multiple detectors, and can reach energies all the way to the t-tbar threshold and beyond. It will make possible measurements of the Higgs boson properties and of electroweak symmetry-breaking parameters with unequalled precision, offering exploration of physics beyond the Standard Model in the multi-TeV range. Moreover, being the natural precursor of a 100-TeV hadron machine in the same tunnel, it offers a long-term vision for particle physics. This paper presents a first appraisal of the salient features of the TLEP physics potential, to serve as a baseline for a more extensive design study.Higgs bosonLuminosityLarge Hadron ColliderLarge Electron-Positron ColliderStandard ModelSystematic errorHadronizationStatisticsInternational Linear ColliderStatistical error...
- We present the first cosmological simulations of dwarf galaxies, which include dark matter self-interactions and baryons. We study two dwarf galaxies within cold dark matter, and four different elastic self-interacting scenarios with constant and velocity-dependent cross sections, motivated by a new force in the hidden dark matter sector. Our highest resolution simulation has a baryonic mass resolution of $1.8\times 10^2\,{\rm M}_\odot$ and a gravitational softening length of $34\,{\rm pc}$ at $z=0$. In this first study we focus on the regime of mostly isolated dwarf galaxies with halo masses $\sim10^{10}\,{\rm M}_\odot$ where dark matter dynamically dominates even at sub-kpc scales. We find that while the global properties of galaxies of this scale are minimally affected by allowed self-interactions, their internal structures change significantly if the cross section is large enough within the inner sub-kpc region. In these dark-matter-dominated systems, self-scattering ties the shape of the stellar distribution to that of the dark matter distribution. In particular, we find that the stellar core radius is closely related to the dark matter core radius generated by self-interactions. Dark matter collisions lead to dwarf galaxies with larger stellar cores and smaller stellar central densities compared to the cold dark matter case. The central metallicity within $1\,{\rm kpc}$ is also larger by up to $\sim 15\%$ in the former case. We conclude that the mass distribution, and characteristics of the central stars in dwarf galaxies can potentially be used to probe the self-interacting nature of dark matter.Dark matterCold dark matterSelf-interacting dark matterSimulationsA dwarfsGalaxyStar formationDwarf galaxyStellar massDark matter model...
- Although the cosmological paradigm based on cold dark matter and adiabatic, nearly scale-invariant primordial fluctuations is consistent with a wide variety of existing observations, it has yet to be sufficiently tested on scales smaller than those of massive galaxies, and various alternatives have been proposed that differ significantly in the consequent small-scale power spectrum (SSPS) of large-scale structure. Here we show that a powerful probe of the SSPS at $k\gtrsim 10$ Mpc$^{-1}$ can be provided by the 21 cm forest, that is, systems of narrow absorption lines due to intervening, cold neutral hydrogen in the spectra of high-redshift background radio sources in the cosmic reionization epoch. Such features are expected to be caused predominantly by collapsed gas in starless minihalos, whose mass function can be very sensitive to the SSPS. As specific examples, we consider the effects of neutrino mass, running spectral index (RSI) and warm dark matter (WDM) on the SSPS, and evaluate the expected distribution in optical depth of 21 cm absorbers out to different redshifts. Within the current constraints on quantities such as the sum of neutrino masses $\sum m_\nu$, running of the primordial spectral index $d n_s/d \ln k$ and WDM particle mass $m_{\rm WDM}$, the statistics of the 21 cm forest manifest observationally significant differences that become larger at higher redshifts. In particular, it may be possible to probe the range of $m_{\rm WDM} \gtrsim 10$ keV that may otherwise be inaccessible. Future observations of the 21 cm forest by the Square Kilometer Array may offer a unique and valuable probe of the SSPS, as long as radio sources such as quasars or Population III gamma-ray bursts with sufficient brightness and number exist at redshifts of $z \gtrsim$ 10 - 20, and the astrophysical effects of reionization and heating can be discriminated.Hydrogen 21 cm lineWarm dark matterHalo mass functionAbsorption featureMassive neutrinoNeutrino massLine of sightSpectral index of power spectrumGamma ray burstCosmology...
- We report the results of extended high--resolution numerical integrations of the Vlasov--Poisson equation for the collapse of spherically symmetric WDM halos. For thermal relics with mass $m=1\,$keV/$c^2$, we find collapsed halos with cores of size from $0.1$ to $0.6\,$kpc. The typical core is hollow, with the mass density decreasing towards the core center by almost three orders of magnitude from its maximum near the core radius $r_{\rm c}$. The core is in equilibrium with the diffused part of the halo but far from virialization. These properties are rooted in the conservation of the squared angular momentum and in the original excess, proper of WDM initial conditions, of kinetic energy in the core region. In a sample of more than one hundred simulated collapses, the values of $r_{\rm c}$ and of the core density $\rho_{\rm c}$ are in the range typical of dwarf spheroids, while the maximal circular velocities $V_{\rm max}$ are proper of small disk galaxies. The product $\mu_{\rm c}=\rho_{\rm c}r_{\rm c}$ takes values between $116\,M_\odot/$pc$^2$ and $283\,M_\odot/$pc$^2$, while the surface density $\mu_0$, as determined from a Burkert fit, is roughly three times larger. From these data and data obtained at smaller values of $m$, we extrapolate for one particular halo $\mu_{\rm c}=263(308)\,M_\odot/$pc$^2$ and $\mu_0=754(855)\,M_\odot/$pc$^2$ at $m=2(3.3)\,$keV/$c^2$, to be compared with the observed value $140^{+83}_{-52} M_\odot$/pc$^2$. In view of the many improvements and enhancements available, we conclude that WDM is a viable solution for explaining the presence and the size of cores in low mass galaxies.Warm dark matterSimulationsVelocity dispersionDark matterDark matter haloPhase spaceCold dark matterThermalisationCore radiusCircular velocity...
- AGN, powered by accretion onto SMBHs, are thought to be scaled up versions of Galactic black hole X-ray binaries (BH-XRBs). In the past few years evidence of such correspondence include similarities in the broadband shape of the X-ray variability power spectra, with characteristic bend times-scales scaling with mass. We have performed a uniform analysis of the power spectrum densities (PSDs) of 104 nearby (z<0.4) AGN using 209 XMM-Newton/pn observations. The PSDs have been estimated in three energy bands: 0.2-10, 0.2-2, and 2-10 keV. The sample comprises 61 Type-1 AGN, 21 Type-2 AGN, 15 NLSy1, and 7 BLLACS. We have fitted each PSD to two models: (1) a single power-law model and (2) a bending power-law model. Among the entire sample, 72% show significant variability in at least one of the three bands tested. A high percentage of low-luminosity AGN do not show any significant variability. The PSD of the majority of the variable AGN was well described by a simple power-law with a mean index of 2. In 15 sources we found that the bending power law model was preferred with a mean slope of 3 and a mean bend frequency of 2.E-04 Hz. Only KUG1031+398 (REJ1034+396) shows evidence for quasi-periodic oscillations. The `fundamental plane' relating variability timescale, black hole mass, and luminosity is demonstrated using the new X-ray timing results presented here together with a compilation of the previously detected timescales from the literature. Both quantitative (i.e. scaling with BH mass) and qualitative (overall PSD shapes) found in this sample of AGN are in agreement with the expectations for the SMBHs and BH-XRBs being the same phenomenon scaled-up with the size of the BH. The steep PSD slopes above the high frequency bend bear a closer resemblance to those of the `soft/thermal dominated' BH-XRB states than other states.Active Galactic NucleiQuasi-Periodic OscillationsBlack holeLow ionization nuclear emission regionLuminosityAccretionLight curveShot noiseX-ray binaryTime Series...
- We consider a singlet fermion dark matter with PQ symmetry. A singlet complex scalar is introduced to mediate between dark matter and the SM through Higgs portal interaction and electroweak PQ anomalies. We show that dark matter annihilation with axion mediation can explain a monochromatic photon line of the Fermi LAT data at 130 GeV by anomaly interactions while the annihilation cross section with Higgs portal interaction is p-wave suppressed. We discuss the interplay between direct detection of the fermion dark matter and the collider search of Higgs-like scalars. We also present a ultra-violet completion of the dark matter model into the NMSSM with PQ symmetry.Dark matterAxionDark matter annihilationStandard ModelGamma-ray linesBranching ratioFERMI telescopePeccei-Quinn symmetryInvisible axionSupersymmetry breaking...
- Some of direct dark matter searches reported not only positive signals but also annual modulation of the signal event. However, the parameter spaces have been excluded by other experiments. Isospin violating dark matter solves the contradiction by supposing different coupling to proton and neutron. We study the possibility to test the favored parameter region by isospin violating dark matter model with the future detector of dark matter using the nuclear emulsion. Since the nuclear emulsion detector has directional sensitivity, the detector is expected to examine whether the annual modulations observed other experiments is caused by dark matter or background signals.Dark matterEmulsionIsospinAnnual modulation of dark matter signalIsotopeForm factorEarthCharged particleDark matter modelCoGeNT...
- Upper limits on the spin-independent (SI) as well as spin-dependent (SD) elastic scattering cross sections of WIMPs with protons, imposed by the Super-Kamiokande (S-K) upper limit on the neutrino flux from WIMP annihilation in the Sun, and their compatibility with the "DAMA-compatible" regions of the WIMP parameter space within which the annual modulation signal observed by the DAMA/LIBRA experiment is compatible with the null results of other direct detection experiments, are studied within the frame work of a self-consistent model of the finite-size dark matter (DM) halo of the Galaxy, the parameters of which are determined by a fit to the rotation curve data of the Galaxy. We find that the S-K implied upper limits on the WIMP-proton elastic cross section as a function of WIMP mass impose stringent restrictions on the branching fractions of the various WIMP annihilation channels. For SI interaction, while the S-K upper limits are consistent with the DAMA-compatible region of the WIMP parameter space if the WIMPs annihilate dominantly to $\bbarb$\ and/or $\cbarc$, portions of the DAMA-compatible region can be excluded if WIMP annihilations to $\tautau$ and $\nu\anu$ occur at larger than 10% and $10^{-3}$ levels, respectively. For SD interaction, the restrictions on the possible annihilation channels are much more stringent, essentially ruling out the DAMA-compatible region of the WIMP parameter space if the relatively low-mass ($\sim$ 2 -- 20 GeV) WIMPs under consideration annihilate predominantly to any mixture of $\bbarb$, \ $\cbarc$, \ $\tautau$, \ and $\nu\anu$ final states. The upper limits on the branching fractions of the various annihilation channels obtained here are about a factor of 10 more restrictive than those obtained earlier within the context of the Standard Halo Model.Weakly interacting massive particleSunWIMP annihilationNeutrinoGalaxyBranching ratioDark matterStandard Halo modelDAMA/LIBRAHalo model...
- Two centuries of research on phase transitions have repeatedly highlighted the importance of critical fluctuations that abound in the vicinity of a critical point. They are at the origin of scaling laws obeyed by thermodynamic observables close to second-order phase transitions resulting in the concept of universality classes, that is of paramount importance for the study of organizational principles of matter. Strikingly, in case such soft fluctuations are too abundant they may alter the nature of the phase transition profoundly; the system might evade the critical state altogether by undergoing a discontinuous first-order transition into the ordered phase. Fluctuation-induced first-order transitions have been discussed broadly and are germane for superconductors, liquid crystals, or phase transitions in the early universe, but clear experimental confirmations remain scarce. Our results from neutron scattering and thermodynamics on the model Dzyaloshinskii-Moriya (DM) helimagnet (HM) MnSi show that such a fluctuation-induced first-order transition is realized between its paramagnetic and HM state with remarkable agreement between experiment and a theory put forward by Brazovskii. While our study clarifies the nature of the HM phase transition in MnSi that has puzzled scientists for several decades, more importantly, our conclusions entirely based on symmetry arguments are also relevant for other DM-HMs with only weak cubic magnetic anisotropies. This is in particular noteworthy in light of a wide range of recent discoveries that show that DM helimagnetism is at the heart of problems such as topological magnetic order, multiferroics, and spintronics.IntensityPhase transitionsDark matterMomentum spaceEffective potentialRenormalizationSkyrmionMagnetizationMagnetic anisotropyCritical point...
- We discuss the neutrino masses and mixings as the realization of an $S_{3}$ flavour permutational symmetry in two models, namely the Standard Model and an extension of the Standard Model with three Higgs doublets. In the $S_3$ Standard Model, mass matrices of the same generic form are obtained for the neutrino and charged leptons when the $S_{3}$ flavour symmetry is broken sequentially. In the minimal $S_{3}$-symmetric extension of the Standard Model, the $S_3$ symmetry is left unbroken, and the concept of flavour is extended to the Higgs sector by introducing in the theory three Higgs fields which are SU(2) doublets. In both models, the mass matrices of the neutrinos and charged leptons are reparametrized in terms of their eigenvalues, and exact, explicit analytical expressions for the neutrino mixing angles as functions of the masses of neutrino and charged leptons are obtained. In the case of the $S_3$ Standard Model, from a $\chi^2$ fit of the theoretical expressions of the lepton mixing matrix to the values extracted from experiment, the numerical values of the neutrino mixing angles are obtained in excellent agreement with experimental data. In the $S_3$ extension of the Standard Model, if two of the right handed neutrinos masses are degenerate, the reactor and atmospheric mixing angles are determined by the masses of the charged leptons, yielding $\theta_{23}$ in excellent agreement with experimental data, and $\theta_{13}$ different from zero but very small. If the masses of the three right handed neutrinos are assumed to be different, then it is possible to get $\theta_{13}$ also in very good agreement with experimental data. We also show the branching ratios of some selected flavour changing neutral currents (FCNC) process as well as the contribution of the exchange of a neutral flavour changing scalar to the anomaly of the magnetic moment of the muon.Neutrino massFlavourNeutrinoStandard ModelQuarkMajorana neutrinoFlavour symmetryExtensions of the standard modelSterile neutrinoFlavour Changing Neutral Currents...
- Superluminal neutrinos are expected to lose energy due to bremstrauhlung. It is dominated by e+e--pair production if kinematically allowed. The same signature was used in searches for 3-body decays of hypothetical heavy sterile neutrinos. From the absence of these processes in CERN PS191 and CHARM experiments we set upper limits on the neutrino velocity in the energy range from 0.2 GeV to 280 GeV. Our limits are well below the neutrino velocity favored by the recent OPERA results. For energy-independent neutrino velocity the limits obtained in this paper are stronger than those coming from ICARUS experiment and observations of Supernova SN1987a.NeutrinoSterile neutrinoCERNOPERA experimentMuon neutrinoStandard ModelPair productionNeutrino beamSupernova 1987AStatistics...
- Using hydrodynamical zoom simulations in the standard LCDM cosmology, we investigate the evolution of the distribution of baryons (gas and stars) in a local group-type universe. First, with standard star formation and supernova feedback prescriptions, we find that the mean baryonic fraction value estimated at the virial radius of the two main central objects (i.e. the Milky Way and Andromeda) is decreasing over time, and is 10-15% lower than the universal value, 0.166, at z=0. This decrease is mainly due to the fact that the amount of accretion of dissipative gas onto the halo, especially at low redshift, is in general much lower than that of the dissipationless dark matter. Indeed, a significant part of the baryons does not collapse onto the haloes and remains in their outskirts, mainly in the form of warm-hot intergalactic medium (WHIM). Moreover, during the formation of each object, some dark matter and baryons are also be expelled through merger events via tidal disruption. In contrast to baryons, expelled dark matter can be more efficiently re-accreted onto the halo, enhancing both the reduction of fb inside Rv, and the increase of the mass of WHIM outside Rv. Varying the efficiency of supernovae feedback at low redshift does not seem to significantly affect these trends. Alternatively, when a significant fraction of the initial gas in the main objects is released at high redshifts by more powerful sources of feedback, such as AGN from intermediate mass black holes in lower mass galaxies, the baryonic fraction at the virial radius can have a lower value (fb~0.12) at low redshift. Hence physical mechanisms able to slow down the accretion of gas at high redshifts will have a stronger impact on the deficit of baryons in the mass budget of Milky Way type-galaxies at present times than those that expel the gas in the longer, late phases of galaxy formation.AccretionVirial radiusDark matterGalaxySupernovaStellar massStarWarm hot intergalactic mediumActive Galactic NucleiHydrodynamical simulations...
- In this paper we investigate the space and velocity distributions of old neutron stars (aged 109 to 1010 yr) in our Galaxy. Galactic old Neutron Stars (NSs) population fills a torus-like area extending to a few tens kiloparsecs above the galactic plane. The initial velocity distribution of NSs is not well known, in this work we adopt a three component initial distribution, as given by the contribution of kick velocities, circular velocities and Maxwellian velocities. For the spatial initial distribution we use a Gamma function. We then use Monte Carlo simulations to follow the evolution of the NSs under the influence of the Paczy{\P}nski Galactic gravitational potential. Our calculations show that NS orbits have a very large Galactic radial expansion and that their radial distribution peak is quite close to their progenitors' one. We also study the NS vertical distribution and find that it can well be described by a double exponential low. Finally, we investigate the correlation of the vertical and radial distribution and study the radial dependence of scale-heights.Neutron starGamma functionGalaxyScale heightGalactic planeMonte Carlo methodGalactic disksGalactic CenterMilky WayGravitational fields...
- The recent measurement of the reactor angle as $\sin^2 2\theta_{13} = 0.092 \pm 0.016(stat) \pm 0.005(syst)$ come from the Daya Bay collaboration. Evidence of nonzero \theta_{13} was also there at T2K, MINOS and Double Chooz experiments. We study the implication of these recent data on neutrino mass matrix and consequently on leptogenesis in a supersymmetric SO(10) model. To explain the smallness of neutrino mass, in general, we require a heavy Majorana neutrino which is a natural candidate in SO(10) model. In minimal SO(10) model, the symmetry breaking scale or the right-handed neutrino mass scale is close to the GUT scale. It is not only beyond the reach of any present or future collider search but the lepton asymmetry generated from its decay is in conflict with the gravitino constraint as well as unable to fit the neutrino data. We show that addition of an extra fermion singlet can accommodate the observed recent neutrino data in a supersymmetric SO(10) model. This model can generate the desired lepton asymmetry and provide TeV scale doubly-charged Higgs scalars to be detected at LHC.NeutrinoNeutrino massLepton asymmetryGravitinoGrand unification theoryGauge coupling constantVacuum expectation valueSterile neutrinoMajorana neutrinoSupersymmetry...
- We present late-time Hubble Space Telescope imaging of the fields of six Swift GRBs lying at 5.0<z<9.5. Our data includes very deep observations of the field of the most distant spectroscopically confirmed burst, GRB 090423, at z=8.2. Using the precise positions afforded by their afterglows we can place stringent limits on the luminosities of their host galaxies. In one case, that of GRB 060522 at z=5.11, there is a marginal excess of flux close to the GRB position which may be a detection of a host at a magnitude J(AB)=28.5. None of the others are significantly detected meaning that all the hosts lie below L\star at their respective redshifts, with star formation rates SFR<4Mo/yr in all cases. Indeed, stacking the five fields with WFC3-IR data we conclude a mean SFR<0.17Mo/yr per galaxy. These results support the proposition that the bulk of star formation, and hence integrated UV luminosity, at high redshifts arises in galaxies below the detection limits of deep-field observations. Making the reasonable assumption that GRB rate is proportional to UV luminosity at early times allows us to compare our limits with expectations based on galaxy luminosity functions derived from the Hubble Ultra-Deep Field (HUDF) and other deep fields. We infer that a luminosity function which is evolving rapidly towards steeper faint-end slope (alpha) and decreasing characteristic luminosity (L\star), as suggested by some other studies, is consistent with our observations, whereas a non-evolving LF shape is ruled out at >90% confidence. Although it is not yet possible to make stronger statements, in the future, with larger samples and a fuller understanding of the conditions required for GRB production, studies like this hold great potential for probing the nature of star formation, the shape of the galaxy luminosity function, and the supply of ionizing photons in the early universe.Gamma ray burstGalaxyLuminosity functionLuminosityStar formation rateStar formationThe Hubble Space Telescope "Ultra Deep Field" ViewHost galaxyReionizationWide Field Camera 3...
- Locating the centers of dark matter halos is critical for understanding the mass profiles of halos as well as the formation and evolution of the massive galaxies that they host. The task is observationally challenging because we cannot observe halos directly, and tracers such as bright galaxies or X-ray emission from hot plasma are imperfect. In this paper we quantify the consequences of miscentering on the weak lensing signal from a sample of 129 X-ray selected galaxy groups in the COSMOS field with redshifts 0<z<1 and halo masses in the range 10^13 - 10^14 M_sun. By measuring the stacked lensing signal around eight different candidate centers (such as the brightest member galaxy, the mean position of all member galaxies, or the X-ray centroid), we determine which candidates best trace the center of mass in halos. In this sample of groups, we find that massive galaxies near the X-ray centroids trace the center of mass to <~75 kpc, while the X-ray position and centroids based on the mean position of member galaxies have larger offsets primarily due to the statistical uncertainties in their positions (typically ~50-150 kpc). Approximately 30% of groups in our sample have ambiguous centers with multiple bright or massive galaxies, and these groups show disturbed mass profiles that are not well fit by standard models, suggesting that they are merging systems. We find halo mass estimates from stacked weak lensing can be biased low by 5-30% if inaccurate centers are used and the issue of miscentering is not addressed.GalaxyDark matter subhaloStellar massVirial massMassive galaxiesWeak lensingStatisticsDark matter haloPhotometric redshiftCOSMOS survey...
#### Neutrinos and the starsver. 2

The role of neutrinos in stars is introduced for students with little prior astrophysical exposure. We begin with neutrinos as an energy-loss channel in ordinary stars and conversely, how stars provide information on neutrinos and possible other low-mass particles. Next we turn to the Sun as a measurable source of neutrinos and other particles. Finally we discuss supernova (SN) neutrinos, the SN 1987A measurements, and the quest for a high-statistics neutrino measurement from the next nearby SN. We also touch on the subject of neutrino oscillations in the high-density SN context.NeutrinoStarAxionSunSupernovaSolar neutrinoSupernova 1987ACore collapseWhite dwarfShock wave...- Galaxy mass and environment are known to play a key role in galaxy evolution: looking at galaxy colors at different redshifts, fixed galaxy mass and environment, offers a powerful diagnosis to disentangle the role of each. In this work, we study the simulateneous dependence of the fraction of blue galaxies fblue on secular evolution, environment and galaxy mass with a well-controlled cluster sample. We are thus able to study the evolution and respective role of the cessation of star formation history (SFH) in clusters due to galaxy mass ("mass quenching") or to environment ("environmental quenching"). We define an homogenous X-ray selected cluster sample (25 clusters with 0 < z < 1 and one cluster at z \sim 2.2), having similar masses and well-defined sizes. Using multicolor photometry and a large spectroscopic sample to calibrate photometric redshifts, we carefully estimate fblue for each cluster at different galaxy mass and cluster-centric distance bins. We then fit with a simple model the dependence of fblue on redshift (z), environment (r/r200) and galaxy mass (M). fblue increases with cluster-centric distance with a slope $1.2^{+0.4}_{-0.3}$, decreases with galaxy mass with a slope $-3.8^{+0.6}_{-0.5}$, and increases with redshift with a slope $3.2^{+0.7}_{-0.5}$. The data also require for the first time a differential evolution with galaxy mass of fblue with redshift, with lower mass galaxies evolving slower by a factor $-4.1^{+1.1}_{-0.9}$. Our study shows that the processes responsible for the cessation of star formation in clusters are effective at all epochs (z<2.2), and more effective in denser environments and for more massive galaxies. We found that the mass and environmental quenchings are separable, that environmental quenching does not change with epoch, and that mass quenching is a dynamical process, i.e. its evolutionary rate is mass-dependent. [Abridged]GalaxyQuenchingStarCluster samplingBlue galaxiesCanada-France-Hawaii Telescope Legacy SurveyMassive galaxiesStar formationSloan Digital Sky SurveyGalactic evolution...
- We introduce a new photometric estimator of the HI mass fraction (M_HI/M_*) in local galaxies, which is a linear combination of four parameters: stellar mass, stellar surface mass density, NUV-r colour, and g-i colour gradient. It is calibrated using samples of nearby galaxies (0.025<z<0.05) with HI line detections from the GASS and ALFALFA surveys, and it is demonstrated to provide unbiased M_HI/M_* estimates even for HI-rich galaxies. We apply this estimator to a sample of ~24,000 galaxies from the SDSS/DR7 in the same redshift range. We then bin these galaxies by stellar mass and HI mass fraction and compute projected two point cross-correlation functions with respect to a reference galaxy sample. Results are compared with predictions from current semi-analytic models of galaxy formation. The agreement is good for galaxies with stellar masses larger than 10^10 M_sun, but not for lower mass systems. We then extend the analysis by studying the bias of HI-poor or HI-rich galaxies with respect to galaxies with normal HI content on scales between 100 kpc and ~5 Mpc. For the HI-poor population, the strongest bias effects arise when the HI-deficiency is defined in comparison to galaxies of the same stellar mass and size. This is not reproduced by the semi-analytic models, where the quenching of star formation in satellites occurs by "starvation" and does not depend on their internal structure. HI-rich galaxies with masses greater than 10^10 M_sun are found to be anti-biased compared to galaxies with "normal" HI content. Interestingly, no such effect is found for lower mass galaxies.GalaxyStellar massStellar surfacesSloan Digital Sky SurveyDark matter haloAccretionALFALFA surveySatellite galaxyStar formationQuenching...
- Using observations in the COSMOS field, we report an intriguing correlation between the star formation activity of massive (~10^{11.4}\msol) central galaxies, their stellar masses, and the large-scale (~10 Mpc) environments of their group-mass (~10^{13.6}\msol) dark matter halos. Probing the redshift range z=[0.2,1.0], our measurements come from two independent sources: an X-ray detected group catalog and constraints on the stellar-to-halo mass relation derived from a combination of clustering and weak lensing statistics. At z=1, we find that the stellar mass in star-forming centrals is a factor of two less than in passive centrals at the same halo mass. This implies that the presence or lack of star formation in group-scale centrals cannot be a stochastic process. By z=0, the offset reverses, probably as a result of the different growth rates of these objects. A similar but weaker trend is observed when dividing the sample by morphology rather than star formation. Remarkably, we find that star-forming centrals at z~1 live in groups that are significantly more clustered on 10 Mpc scales than similar mass groups hosting passive centrals. We discuss this signal in the context of halo assembly and recent simulations, suggesting that star-forming centrals prefer halos with higher angular momentum and/or formation histories with more recent growth; such halos are known to evolve in denser large-scale environments. If confirmed, this would be evidence of an early established link between the assembly history of halos on large scales and the future properties of the galaxies that form inside them.GalaxyStar formationVirial massStellar massCOSMOS surveyStatisticsDark matter haloCross-correlationHalo Occupation DistributionHalo assembly bias...
- With the aim of achieving a better and more complete understanding of neutrino interactions with nuclear targets, the coherent production of charged kaons induced by neutrinos and antineutrinos is investigated in the energy range of some of the current neutrino experiments. We follow a microscopic approach which, at the nucleon level, incorporates the most important mechanisms allowed by the chiral symmetry breaking pattern of QCD. The distortion of the outgoing (anti)kaon is taken into account by solving the Klein-Gordon equation with realistic optical potentials. Angular and momentum distributions are studied, as well as the energy and nuclear dependence of the total cross section.KaonPionForm factorNeutrinoHyperonStrangeness productionMomentum transferAntineutrinoKinematicsChiral symmetry breaking...
- The first systematic study of the warm gas (T=10^4-5 K) distribution across a galaxy cluster is presented using multiple background QSOs to the Virgo Cluster. We detect 25 Lya absorbers (N_HI = 10^13.1-15.4 cm^-2) in the Virgo velocity range toward 9 of 12 QSO sightlines observed with COS, with a cluster impact parameter range of 0.25-1.15 Mpc (0.23-1.05Rvir). Including 18 previously STIS or GHRS detected Lya absorbers toward 7 of 11 background QSOs in and around the Virgo Cluster, we establish a sample of 43 absorbers towards a total of 23 background probes for studying the incidence of Lya absorbers in and around the Virgo Cluster. With these absorbers, we find: 1) Warm gas is predominantly in the outskirts of the cluster and avoids the X-ray detected hot ICM. Also, Lya absorption strength increases with a cluster impact parameter. 2) Lya absorbing warm gas traces cold HI emitting gas in the substructures of the Virgo Cluster. 3) Including the absorbers associated with the surrounding substructures, the warm gas covering fraction (100% for N_HI > 10^13.1 cm^-2) is in an agreement with cosmological simulations. We speculate that the observed warm gas is part of large-scale gas flows feeding the cluster both the ICM and galaxies.AbsorbanceGalaxyVirgo ClusterVirial radiusCosmic Origins SpectrographQuasarGalaxy filamentIntra-cluster mediumAbsorptivitySpace Telescope Imaging Spectrograph...
- We estimate the dependence of $\nu_{\mu}$ to $\nu_{e}$ conversion on parameters $\theta_{13}$ and $\delta_{CP}$ for several experimental facilities studying neutrino oscillations. We use the S-Matrix theory to estimate $\bar{\nu_e}$ disappearance and compare estimates based on an older theory being used to extract $\theta_{13}$ from the Double Chooz, Daya Bay, and RENO data, to assist in extracting an accurate value for $\theta_{13}$ from these projects. We use values of $\theta_{13}$ within known limits, and estimate the dependence of $\nu_{\mu}$ - $\nu_{e}$ CP violation (CPV) probability on $\delta_{CP}$ in order to suggest new experiments to measure CPV for neutrinos moving in matter.CP violationNeutrinoDouble Chooz experimentNeutrino oscillationsS-matrixReactor Experiment for Neutrino OscillationNeutrino beamMiniBooNE experimentAntineutrinoElectron neutrino...
- Super capacitors are promising energy storage devices due to their capability of delivering high peak current and storing high amount of energy in a short time with very low internal power loss. We fabricated the graphene or graphite oxide super-capacitor using laser Lightscribe technique. We prepared graphite oxide by modified hummers method and used PET film as a flexible substrate on which graphite oxide (GO) was coated. Using Lightscribe drive and software, the super-capacitor configuration was patterned on the GO coated PET film. During the writing process, the laser converts GO into graphene. We characterized the fabricated flexible super-capacitor which exhibits high resistance of 20KOhm with applied voltage of 10V and further increase of voltage (20V) decreases the resistance to 8KOhm. We also analyzed the frequency response of the capacitor using impedance measurement which shows high frequency response and estimated capacitance is 120nF. We optimized the patterns by running the Lightscribe repeatedly on the GO coated PET substrate.CapacitorOxideGraphiteLasersGrapheneFrequencyEnergyResistMeasurementImpedance...
- We report fabrication and characteristics of an organic monolayer based Metal Oxide Semiconductor (MOS) device. In place of SiO2 oxide layer in the MOS configuration, we used 1H, 1H, 2H, 2H- perfluorooctyl trichlorosilane (FOTS) self-assembled monolayer as a substitution. The MOS device was fabricated by simple steps like sputter deposition and dip coating method. The device was heat treated to different temperatures to understand its performance and efficiency for high temperature application. The MOS device was heated to 150{\deg} C, 350{\deg}C and 550{\deg}C and the energy band gap was found to be varied in the order 2.5 eV, 3.0 eV and 3.4eV respectively. For non-heated sample, the energy band gap is 3.4 eV. The results shows that the parameters like charge mobility ({\mu}), energy band gap, and resistance were found to be decreased after the heat treatment. The change in the energy band gap due to heat treatment has significantly influenced the I-V and the impedance characteristics. We observed that the MOS device started to conduct between 1V to 3V, further the device conduct till 20V. Impedance analysis show that device heated to 350 {\deg}C shows the low impedance but the impedance starts to increase for further heating up to 550{\deg}C. Using Multi Dielectric Energy Band Diagram Program (MEBDP) we studied the MOS structure and C-V characteristics and temperature dependent behavior of the devices from 100K to 600K. Our experimental work and simulation studies confirm that the FOTS SAM substituted MOS device could be used for high temperature applications. The experimental observations are well supported by the simulation results. This study shows that the FOTS organic monolayer are promising substitute for SiO2 oxide layer in the MOS and MOSFET which could be used high temperature applications.OxideBand gapSimulationsSemiconductorSelf-assembled monolayerBand diagramMetal-Oxide-Semiconductor Field-Effect TransistorEnergyHigh temperatureImpedance...
- The wide research interest for the potential nanoelectronics applications are attracted by the organic and inorganic monolayer materials. In this work, we have studied the organic monolayer such as trichloro (1H,1H,2H,2H-perfluorooctyl)-silane (FOTS), hexamethyldisilazane (HMDS) and inorganic monolayers such as hexagonal - boron nitride (h-BN) and molybdenum disulfide (MoS2) based MOS devices. The organic monolayer based configurations are Au/FOTS/p-Si and Au/HMDS/p-Si. The inorganic monolayer based configurations are Au/MoS2/SiO2/p-Si and Au/h-BN/SiO2/p-Si. These configurations were examined and compared with Au/SiO2/p-Si MOS configuration using the Multi-dielectric Energy Band Diagram Program (MEBDP) and MOSFeT simulation software. The C-V and I-V characteristics of MOS and MOSFET of FOTS, HMDS, h-BN, MoS2 and SiO2 were reported. The results show that the above configurations are suitable for designing MOSFETs with smaller drain induced barrier lowering (DIBL) and reduced threshold voltage. We noted that the above configurations are better than 2nm thick dielectric SiO2 based MOSFET with a channel length of 10nm.Metal-Oxide-Semiconductor Field-Effect TransistorHexagonal boron nitrideXMM-Newton MOS cameraMoS2SimulationsNanoelectronicsDisulfideBand diagramAtomPotential...
- The recent paper by Jeltema & Profumo(2014) claims that contributions from \ion{K}{18} and \ion{Cl}{17} lines can explain the unidentified emission line found by Bulbul et al 2014 and also by Boyarsky et al, 2014a, 2014b. We show that their analysis relies upon incorrect atomic data and inconsistent spectroscopic modeling. We address these points and summarize in the appendix the correct values for the relevant atomic data from AtomDB.PerseusCluster of galaxiesAtomDBAbundanceCoolingXMM-Newton MOS cameraChemical abundanceGalactic CenterKeV lineCool core galaxy cluster...
- We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 < z < 1.0. We use a novel method to robustly compare a sample of 120 AGN host galaxies, defined to have 10^42 erg/s < L_X < 10^44 erg/s, with inactive control galaxies matched in stellar mass, rest-frame colour, size, Sersic index, and redshift. Using the GZH bar classifications of each sample, we demonstrate that AGN hosts show no statistically significant enhancement in bar fraction or average bar likelihood compared to closely-matched inactive galaxies. In detail, we find that the AGN bar fraction cannot be enhanced above the bar fraction in the control sample by more than a factor of two, at 99.7% confidence. We similarly find no significant difference in the AGN fraction among barred and non-barred galaxies. Thus we find no compelling evidence that large-scale bars directly fuel AGN at 0.2 < z < 1.0. This result, coupled with previous results at z = 0, implies that moderate-luminosity AGN have not been preferentially fed by large-scale bars since z = 1. Furthermore, given the low bar fractions at z > 1, our findings suggest that large-scale bars have likely never directly been a dominant fueling mechanism for supermassive black hole growth.Active Galactic NucleiGalaxyCOSMOS surveyAll-Wavelength Extended Groth Strip International SurveyHost galaxyDisk galaxyGalaxy ZooStellar massSupermassive black holeStatistical significance...
- Interferometry lithography is a maturing technology for patterning sub-micron structures in arrays covering large areas. This paper presents a method for the measurement of nanoscale surface patterns produced by two-beam laser interference lithography (LIL). The objective in this study is to simulate and design periodic and quasi-periodic 1D, 2D and 3D nanostructures using two-beam interference technique. We designed and simulated periodic and quasi-periodic structures by two-beam interference patterning using a MATLAB program by varying angle of incidence, wavelength and geometry. The simulated patterns show that the symmetries of the interference maxima depend mostly on the angles of incidence and perturbations of incidents beams. Using this technique, we can achieve potentially high-volume of uniformity, throughput, process control, and repeatability. By varying different input parameters, we have optimized simulated patterns with controlled periodicity, density and aspect ratio also it can be programmed to obtain images of interference results showing interference intensity distributions.InterferenceSimulationsAngle of incidenceQuasiperiodicityNanostructureMultidimensional ArrayMATLABIntensityLasersInterferometry...
- Dark sectors, consisting of new, light, weakly-coupled particles that do not interact with the known strong, weak, or electromagnetic forces, are a particularly compelling possibility for new physics. Nature may contain numerous dark sectors, each with their own beautiful structure, distinct particles, and forces. This review summarizes the physics motivation for dark sectors and the exciting opportunities for experimental exploration. It is the summary of the Intensity Frontier subgroup "New, Light, Weakly-coupled Particles" of the Community Summer Study 2013 (Snowmass). We discuss axions, which solve the strong CP problem and are an excellent dark matter candidate, and their generalization to axion-like particles. We also review dark photons and other dark-sector particles, including sub-GeV dark matter, which are theoretically natural, provide for dark matter candidates or new dark matter interactions, and could resolve outstanding puzzles in particle and astro-particle physics. In many cases, the exploration of dark sectors can proceed with existing facilities and comparatively modest experiments. A rich, diverse, and low-cost experimental program has been identified that has the potential for one or more game-changing discoveries. These physics opportunities should be vigorously pursued in the US and elsewhere.Dark matterAxionChameleonAxion-like particleStandard ModelMilli-Charged ParticleDark energyBeam dumpFifth forceIntensity frontier experiment...
- On the arcminute angular scales probed by Planck, the CMB anisotropies are gently perturbed by gravitational lensing. Here we present a detailed study of this effect, detecting lensing independently in the 100, 143, and 217GHz frequency bands with an overall significance of greater than 25sigma. We use the temperature-gradient correlations induced by lensing to reconstruct a (noisy) map of the CMB lensing potential, which provides an integrated measure of the mass distribution back to the CMB last-scattering surface. Our lensing potential map is significantly correlated with other tracers of mass, a fact which we demonstrate using several representative tracers of large-scale structure. We estimate the power spectrum of the lensing potential, finding generally good agreement with expectations from the best-fitting LCDM model for the Planck temperature power spectrum, showing that this measurement at z=1100 correctly predicts the properties of the lower-redshift, later-time structures which source the lensing potential. When combined with the temperature power spectrum, our measurement provides degeneracy-breaking power for parameter constraints; it improves CMB-alone constraints on curvature by a factor of two and also partly breaks the degeneracy between the amplitude of the primordial perturbation power spectrum and the optical depth to reionization, allowing a measurement of the optical depth to reionization which is independent of large-scale polarization data. Discarding scale information, our measurement corresponds to a 4% constraint on the amplitude of the lensing potential power spectrum, or a 2% constraint on the RMS amplitude of matter fluctuations at z~2.Cosmic microwave backgroundAmplitudeMean fieldSimulationsPoint sourceWeight functionTrispectrumStatisticsCosmologyCMB lensing...
- It is well known that a system of homogeneous second-order ordinary differential equations (spray) is necessarily isotropic in order to be metrizable by a Finsler function of scalar flag curvature. In Theorem 3.1 we show that the isotropy condition, together with three other conditions on the Jacobi endomorphism, characterize sprays that are metrizable by Finsler functions of scalar flag curvature. The proof of Theorem 3.1 provides an algorithm to construct the Finsler function of scalar flag curvature, in the case when a given spray is metrizable. One condition of Theorem 3.1, regarding the regularity of the sought after Finsler function, can be relaxed. By relaxing this condition, we provide examples of sprays that are metrizable by conic pseudo-Finsler functions as well as degenerate Finsler functions. Hilbert's fourth problem asks to determine the Finsler functions with rectilinear geodesics. A Finsler function that is a solution to Hilbert's fourth problem is necessarily of constant or scalar flag curvature. Therefore, we can use the conditions of [11, Theorem 4.1] and Theorem 3.1 to test when the projective deformations of a flat spray, which are isotropic, are metrizable by Finsler functions of constant or scalar flag curvature. We show how to use the algorithms provided by the proofs of [11, Theorem 4.1] and Theorem 3.1 to construct solutions to Hilbert's fourth problem.CurvatureGeodesicScalar curvatureEndomorphismRegularizationHomogenizationRelaxationSymplectizationManifoldCurvature tensor...
- Consider $L$ a regular Lagrangian, $S$ the canonical semispray, and $h$ the horizontal projector of the canonical nonlinear connection. We prove that if the Lagrangian is constant along the integral curves of the Euler-Lagrange equations then it is constant along the horizontal curves of the canonical nonlinear connection. In other words $S(L)=0$ implies $d_hL=0$. If the Lagrangian $L$ is homogeneous of order $k\neq 1$ then $L$ is a conservation law and hence $d_hL=0$. We give an example of nonhomogeneous Lagrangians for which $d_hL\neq 0$.Vector fieldTangent bundleIntegral curveTwo-formRiemannian metricManifoldEuler-Lagrange equationSubbundleGeodesicEpimorphism...
- The geometry of a Lagrangian mechanical system is determined by its associated evolution semispray. We uniquely determine this semispray using the symplectic structure and the energy of the Lagrange space and the external force field. We study the variation of the energy and Lagrangian functions along the evolution and the horizontal curves and give conditions by which these variations vanish. We provide examples of mechanical systems which are dissipative and for which the evolution nonlinear connection is either metric or symplectic.Vector fieldDissipationCovariant derivativeSubbundleTangent bundleGeodesicTwo-formIntegral curveEuler's theoremEuler-Lagrange equation...
- A dynamical system on the total space of the fibre bundle of second order accelerations, $T^2M$, is defined as a third order vector field $S$ on $T^2M$, called semispray, which is mapped by the second order tangent structure into one of the Liouville vector field. For a regular Lagrangian of second order we prove that this semispray is uniquely determined by two associated Cartan-Poincar\'e one-forms. To study the geometry of this semispray we construct a nonlinear connection, which is a Lagrangian subbundle for the presymplectic structure. Using this semispray and the associated nonlinear connection we define covariant derivatives of first and second order. With respect to this, the second order dynamical derivative of the Lagrangian metric tensor vanishes.Tangent bundleCovariant derivativeTwo-formSubbundleManifoldTensor fieldLie derivativeEuler-Lagrange equationBundleGeodesic...