Calculating resonance positions and widths using the Siegert approximation method

Here we present complex resonance states (or Siegert states), that describe the tunneling decay of a trapped quantum particle, from an intuitive point of view which naturally leads to the easily applicable Siegert approximation method that can be used for analytical and numerical calculations of complex resonances of both the linear and nonlinear Schr\"odinger equation. Our approach thus complements other treatments of the subject that mostly focus on methods based on continuation in the complex plane or on semiclassical approximations.Comment: 15 pages, 1 figure, contains MATLAB source code; new version with additional illustration

Studying the Solar system with the International Pulsar Timing Array

Pulsar-timing analyses are sensitive to errors in the Solar-system ephemerides (SSEs) that timing models utilize to estimate the location of the Solar-system barycentre, the quasi-inertial reference frame to which all recorded pulse times-of-arrival are referred. Any error in the SSE will affect all pulsars, therefore pulsar timing arrays (PTAs) are a suitable tool to search for such errors and impose independent constraints on relevant physical parameters. We employ the first data release of the International Pulsar Timing Array to constrain the masses of the planet–moons systems and to search for possible unmodelled objects (UMOs) in the Solar system. We employ 10 SSEs from two independent research groups, derive and compare mass constraints of planetary systems, and derive the first PTA mass constraints on asteroid-belt objects. Constraints on planetary-system masses have been improved by factors of up to 20 from the previous relevant study using the same assumptions, with the mass of the Jovian system measured at 9.5479189(3) × 10^(−4) M⊙. The mass of the dwarf planet Ceres is measured at 4.7(4) × 10^(−10) M⊙. We also present the first sensitivity curves using real data that place generic limits on the masses of UMOs, which can also be used as upper limits on the mass of putative exotic objects. For example, upper limits on dark-matter clumps are comparable to published limits using independent methods. While the constraints on planetary masses derived with all employed SSEs are consistent, we note and discuss differences in the associated timing residuals and UMO sensitivity curves

High Spatial Resolution Observations of Two Young Protostars in the R Corona Australis Region

We present multi-wavelength, high spatial resolution imaging of the IRS 7 region in the R Corona Australis molecular cloud. Our observations include 1.1 mm continuum and HCO^+ J = $3 \to 2$ images from the SMA, ^{12}CO J = $3 \to 2$ outflow maps from the DesertStar heterodyne array receiver on the HHT, 450 $\mu$m and 850 $\mu$m continuum images from SCUBA, and archival Spitzer IRAC and MIPS 24 \micron images. The accurate astrometry of the IRAC images allow us to identify IRS 7 with the cm source VLA 10W (IRS 7A) and the X-ray source X_W. The SMA 1.1 mm image reveals two compact continuum sources which are also distinguishable at 450 $\mu$m. SMA 1 coincides with X-ray source CXOU J190156.4-365728 and VLA cm source 10E (IRS 7B) and is seen in the IRAC and MIPS images. SMA 2 has no infrared counterpart but coincides with cm source VLA 9. Spectral energy distributions constructed from SMA, SCUBA and Spitzer data yield bolometric temperatures of 83 K for SMA 1 and $\leq$70 K for SMA 2. These temperatures along with the submillimeter to total luminosity ratios indicate that SMA 2 is a Class 0 protostar, while SMA 1 is a Class 0/Class I transitional object (L=$17\pm6$ \Lsun). The ^{12}CO J = $3 \to 2$ outflow map shows one major and possibly several smaller outflows centered on the IRS 7 region, with masses and energetics consistent with previous work. We identify the Class 0 source SMA 2/VLA 9 as the main driver of this outflow. The complex and clumpy spatial and velocity distribution of the HCO^+ J = $3 \to 2$ emission is not consistent with either bulk rotation, or any known molecular outflow activity.Comment: 31 pages, 8 figures, Accepted to Ap

Some comments about Schwarzschield black holes in Matrix theory

In the present paper we calculate the statistical partition function for any number of extended objects in Matrix theory in the one loop approximation. As an application, we calculate the statistical properties of K clusters of D0 branes and then the statistical properties of K membranes which are wound on a torus.Comment: 15 page

Varieties of vacua in classical supersymmetric gauge theories

We give a simple description of the classical moduli space of vacua for supersymmetric gauge theories with or without a superpotential. The key ingredient in our analysis is the observation that the lagrangian is invariant under the action of the complexified gauge group \Gc. From this point of view the usual $D$-flatness conditions are an artifact of Wess--Zumino gauge. By using a gauge that preserves \Gc invariance we show that every constant matter field configuration that extremizes the superpotential is \Gc gauge-equivalent (in a sense that we make precise) to a unique classical vacuum. This result is used to prove that in the absence of a superpotential the classical moduli space is the algebraic variety described by the set of all holomorphic gauge-invariant polynomials. When a superpotential is present, we show that the classical moduli space is a variety defined by imposing additional relations on the holomorphic polynomials. Many of these points are already contained in the existing literature. The main contribution of the present work is that we give a careful and self-contained treatment of limit points and singularities.Comment: 14 pages, LaTeX (uses revtex.sty

Current driven magnetization dynamics in helical spin density waves

A mechanism is proposed for manipulating the magnetic state of a helical spin density wave using a current. In this paper, we show that a current through a bulk system with a helical spin density wave induces a spin transfer torque, giving rise to a rotation of the order parameter.The use of spin transfer torque to manipulate the magnetization in bulk systems does not suffer from the obstacles seen for magnetization reversal using interface spin transfer torque in multilayered systems. We demonstrate the effect by a quantitative calculation of the current induced magnetization dynamics of Erbium. Finally we propose a setup for experimental verification.Comment: In the previous version of this paper was a small numerical mistake made when evaluating equation 3 and 9. The number of digits given in the calculation of the torque current tensor is reduced to better represent the accuracy of the calculation. A slightly modified paper have been published in Phys. Rev. Lett. 96, 256601 (2006) 4 pages 3 figure

A Research-Based Curriculum for Teaching the Photoelectric Effect

Physics faculty consider the photoelectric effect important, but many erroneously believe it is easy for students to understand. We have developed curriculum on this topic including an interactive computer simulation, interactive lectures with peer instruction, and conceptual and mathematical homework problems. Our curriculum addresses established student difficulties and is designed to achieve two learning goals, for students to be able to (1) correctly predict the results of photoelectric effect experiments, and (2) describe how these results lead to the photon model of light. We designed two exam questions to test these learning goals. Our instruction leads to better student mastery of the first goal than either traditional instruction or previous reformed instruction, with approximately 85% of students correctly predicting the results of changes to the experimental conditions. On the question designed to test the second goal, most students are able to correctly state both the observations made in the photoelectric effect experiment and the inferences that can be made from these observations, but are less successful in drawing a clear logical connection between the observations and inferences. This is likely a symptom of a more general lack of the reasoning skills to logically draw inferences from observations.Comment: submitted to American Journal of Physic

A Hubble Space Telescope Survey of Extended [OIII]5007A Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: Results

We present the results of a Hubble Space Telescope (HST) survey of extended [OIII] emission in a sample of 60 nearby Seyfert galaxies (22 Seyfert 1's and 38 Seyfert 2's), selected by mostly isotropic properties. The comparison between the semi major axis size of their [OIII] emitting regions (R_Maj) shows that Seyfert 1's and Seyfert 2's have similar distributions, which seems to contradict Unified Model predictions. We discuss possible ways to explain this result, which could be due either to observational limitations or the models used for the comparison with our data. We show that Seyfert 1 Narrow Line Regions (NLR's) are more circular and concentrated than Seyfert 2's, which can be attributed to foreshortening in the former. We find a good correlation between the NLR size and luminosity, following the relation R_Maj propto L([OIII])^0.33, which is flatter than a previous one found for QSO's and Seyfert 2's. We discuss possible reasons for the different results, and their implications to photoionization models. We confirm previous results which show that the [OIII] and radio emission are well aligned, and also find no correlation between the orientation of the extended [OIII] emission and the host galaxy major axis. This agrees with results showing that the torus axis and radio jet are not aligned with the host galaxy rotation axis, indicating that the orientation of the gas in the torus, and not the spin of the black hole, determine the orientation of the accretion disk, and consequently the orientation of the radio jet.Comment: 17 pages including 12 figures, to appear in Ap

Impact of in-crop and soil residual herbicides on effective nitrogen fixation in field pea (Pisum sativum L.) and chickpea (Cicer arietinum L.)

Non-Peer ReviewedA three-year project was initiated in 2004 to examine the effects of residual herbicides and registered “in-crop” herbicides, both soil and foliar applied, on N fixation and consequent yield of field peas and chickpeas. Inoculation strategies were examined to determine if inoculant formulation (i.e., peat powder versus granular inoculant) influences the degree to which herbicides can affect N fixation. This research is ongoing and thus all results are considered preliminary. Preliminary results in field pea, suggest that where herbicides had a negative effect on N fixation, the effects occurred at relatively early growth stages (i.e., soon after herbicide application) and were typically overcome at later growth stages. In addition, granular inoculants were associated with increased N fixation as compared to peat powder inoculants, and may have mitigated any negative herbicide effects. Chickpea incurred damage from the herbicides and all treatments had significantly less N fixation than the control. In general, results suggest that N fixation may be compromised if herbicides cause significant plant damage; however, improved weed control associated with herbicide application may counter the negative impact on early N fixation