Analysis for Mar Vel Black and acetylene soot low reflectivity surfaces for star tracker sunshade applications

Mar Vel Black is a revolutionary new extremely low reflectivity anodized coating developed by Martin Marietta of Denver. It is of great interest in optics in general, and in star trackers specifically because it can reduce extraneous light reflections. A sample of Mar Vel Black was evaluated. Mar Vel Black looks much like a super black surface with many small peaks and very steep sides so that any light incident upon the surface will tend to reflect many times before exiting that surface. Even a high reflectivity surface would thus appear to have a very low reflectivity under such conditions. Conversely, acetylene soot does not have the magnified surface appearance of a super black surface. Its performance is, however, predictable from the surface structure, considering the known configuration of virtually pure carbon

Large-N Solution of the Heterotic N=(0,2) Two-Dimensional CP(N-1) Model

We continue explorations of non-Abelian strings, focusing on the solution of a heterotic deformation of the CP(N-1) model with an extra right-handed fermion field and N=(0,2) supersymmetry. This model emerges as a low-energy theory on the worldsheet of the BPS-saturated flux tubes (strings) in N=2 supersymmetric QCD deformed by a superpotential of a special type breaking N=2 supersymmetry down to N=1. Using large-N expansion we solve this model to the leading order in 1/N. Our solution exhibits spontaneous supersymmetry breaking for all values of the deformation parameter. We identify the Goldstino field. The discrete Z_{2N} symmetry is shown to be spontaneously broken down to Z_2; therefore, the worldsheet model has N strictly degenerate vacua (with nonvanishing vacuum energy). Thus, the heterotic CP(N-1) model is in the deconfinement phase. We can compare this dynamical pattern, on the one hand, with the N=(2,2) CP(N-1) model which has N degenerate vacua with unbroken supersymmetry, and, on the other hand, with nonsupersymmetric CP(N-1) model with split quasivacua and the Coulomb/confining phase. We determine the mass spectrum of the heterotic CP(N-1) model in the large-N limit.Comment: 23 pages, 6 figures/v.2: 2 expressions corrected, minor textual changes, 1 reference adde

N=(0,2) Deformation of the N=(2,2) Wess-Zumino Model in Two Dimensions

We construct a simple N=(0,2) deformation of the two-dimensional Wess-Zumino model. In addition to superpotential, it includes a "twisted" superpotential. Supersymmetry may or may not be spontaneously broken at the classical level. In the latter case an extra right-handed fermion field \zeta_R involved in the N=(0,2) deformation plays the role of Goldstino.Comment: 6 pages; v2: 3 references added; final version accepted for publication in PR

QCD with Large Number of Quarks: Effects of the Instanton -- Anti-instanton Pairs

We calculate the contribution of the instanton -- anti-instanton ($I\bar I$) pairs to the vacuum energy of QCD-like theories with $N_f$ light fermions using the saddle point method. We find a qualitative change of the behavior: for $N_f \ge 6$ it starts to oscillate with $N_f$. Similar behaviour was known for quantum mechanical systems interacting with fermions. We discuss the possible consequences of this phenomenon, and its relation to the mechanism of chiral symmetry breaking in these theories. We also discuss the asymptotics of the perturbative series associated with the $I\bar I$ contribution, comparing our results with those in literature.Comment: 11 pages, Late

Domain Lines as Fractional Strings

We consider N=2 supersymmetric quantum electrodynamics (SQED) with 2 flavors, the Fayet--Iliopoulos parameter, and a mass term $\beta$ which breaks the extended supersymmetry down to N=1. The bulk theory has two vacua; at $\beta=0$ the BPS-saturated domain wall interpolating between them has a moduli space parameterized by a U(1) phase $\sigma$ which can be promoted to a scalar field in the effective low-energy theory on the wall world-volume. At small nonvanishing $\beta$ this field gets a sine-Gordon potential. As a result, only two discrete degenerate BPS domain walls survive. We find an explicit solitonic solution for domain lines -- string-like objects living on the surface of the domain wall which separate wall I from wall II. The domain line is seen as a BPS kink in the world-volume effective theory. We expect that the wall with the domain line on it saturates both the $\{1,0\}$ and the $\{{1/2},{1/2}\}$b central charges of the bulk theory. The domain line carries the magnetic flux which is exactly 1/2 of the flux carried by the flux tube living in the bulk on each side of the wall. Thus, the domain lines on the wall confine charges living on the wall, resembling Polyakov's three-dimensional confinement.Comment: 28 pages, 13 figure, v2 typos fixed and reference adde

Composite non-Abelian Flux Tubes in N=2 SQCD

Composite non-Abelian vortices in N=2 supersymmetric U(2) SQCD are investigated. The internal moduli space of an elementary non-Abelian vortex is CP^1. In this paper we find a composite state of two coincident non-Abelian vortices explicitly solving the first order BPS equations. Topology of the internal moduli space T is determined in terms of a discrete quotient CP^2/Z_2. The spectrum of physical strings and confined monopoles is discussed. This gives indirect information about the sigma model with target space T.Comment: 37 pages, 7 figures, v3 details added, v4 erratum adde

Tropical mid-tropospheric CO_2 variability driven by the Madden–Julian oscillation

Carbon dioxide (CO_2) is the most important anthropogenic greenhouse gas in the present-day climate. Most of the community focuses on its long-term (decadal to centennial) behaviors that are relevant to climate change, but there are relatively few discussions of its higher-frequency forms of variability, and none regarding its subseasonal distribution. In this work, we report a large-scale intraseasonal variation in the Atmospheric Infrared Sounder CO_2 data in the global tropical region associated with the Madden–Julian oscillation (MJO). The peak-to-peak amplitude of the composite MJO modulation is ~1 ppmv, with a standard error of the composite mean < 0.1 ppmv. The correlation structure between CO2 and rainfall and vertical velocity indicate positive (negative) anomalies in CO_2 arise due to upward (downward) large-scale vertical motions in the lower troposphere associated with the MJO. These findings can help elucidate how faster processes can organize, transport, and mix CO_2 and provide a robustness test for coupled carbon–climate models

Quantum Communication Through a Spin-Ring with Twisted Boundary Conditions

We investigate quantum communication between the sites of a spin-ring with twisted boundary conditions. Such boundary conditions can be achieved by a flux through the ring. We find that a non-zero twist can improve communication through finite odd numbered rings and enable high fidelity multi-party quantum communication through spin rings (working near perfectly for rings of 5 and 7 spins). We show that in certain cases, the twist results in the complete blockage of quantum information flow to a certain site of the ring. This effect can be exploited to interface and entangle a flux qubit and a spin qubit without embedding the latter in a magnetic field.Comment: four pages two figure

Hypotheses for near-surface exchange of methane on Mars

The Curiosity rover recently detected a background of 0.7 ppb and spikes of 7 ppb of methane on Mars. This in situ measurement reorients our understanding of the Martian environment and its potential for life, as the current theories do not entail any geological source or sink of methane that varies sub-annually. In particular, the 10-fold elevation during the southern winter indicates episodic sources of methane that are yet to be discovered. Here we suggest a near-surface reservoir could explain this variability. Using the temperature and humidity measurements from the rover, we find that perchlorate salts in the regolith deliquesce to form liquid solutions, and deliquescence progresses to deeper subsurface in the season of the methane spikes. We therefore formulate the following three testable hypotheses. The first scenario is that the regolith in Gale Crater adsorbs methane when dry and releases this methane to the atmosphere upon deliquescence. The adsorption energy needs to be 36 kJ/mol to explain the magnitude of the methane spikes, higher than existing laboratory measurements. The second scenario is that microorganisms convert organic matter in the soil to methane when they are in liquid solutions. This scenario does not require regolith adsorption, but entails extant life on Mars. The third scenario is that deep subsurface aquifers produce the bursts of methane. Continued in situ measurements of methane and water, as well as laboratory studies of adsorption and deliquescence, will test these hypotheses and inform the existence of the near-surface reservoir and its exchange with the atmosphere.Comment: Accepted for publication on Astrobiolog