1,986 research outputs found
A-Model Correlators from the Coulomb Branch
We compute the contribution of discrete Coulomb vacua to A-Model correlators
in toric Gauged Linear Sigma Models. For models corresponding to a compact
variety, this determines the correlators at arbitrary genus. For non-compact
examples, our results imply the surprising conclusion that the quantum
cohomology relations break down for a subset of the correlators.Comment: 27 pages, 1 xy-pic figur
Reflectionless measures and the Mattila-Melnikov-Verdera uniform rectifiability theorem
A new proof is given of the Mattila-Melnikov-Verdera theorem on the uniform
rectifiability of an Ahlfors-David regular measure whose associated Cauchy
transform operator is bounded.Comment: 31 pages, 5 figure
Engineering Exchange Coupling in Double Elliptic Quantum Dots
Coupled elliptic quantum dots with different aspect ratios containing up to
two electrons are studied using a model confinement potential in the presence
of magnetic fields. Single and two particle Schroedinger equations are solved
using numerical exact diagonolization to obtain the exchange energy and
chemical potentials. As the ratio between the confinement strengths in
directions perpendicular and parallel to the coupling direction of the double
dots increases, the exchange energy at zero magnetic field increases, while the
magnetic field of the singlet-triplet transition decreases. By investigating
the charge stability diagram, we find that as inter-dot detuning increases, the
absolute value of the exchange energy increases superlinearly followed by
saturation. This behavior is attributed to the electron density differences
between the singlet and triplet states in the assymetric quantum dot systems.Comment: 5 pages, 5 figure
Prospects for the development of advanced grain processing in Russia
Purpose: The article is devoted to the identifying and evaluating promising areas of advanced grain and legumes processing development as a strategically important area for import substitution and food security of the agribusiness complex. Methodology/Approach: To achieve this goal, it is necessary to solve the following tasks: the analysis of advanced grain and legumes processing products; the evaluation of the current Russian market for advanced grain processing products; the identification of promising products and directions of the advanced grain processing industry development. Findings: According to the analysis in this article, this industry is in its infancy, despite the fact that in most developed countries of the world, advanced grain processing is widely elaborated. The key reasons for the Russia's lag there involve the lack of domestic techniques and highly qualified specialists in this field. Processing grain into flour, starches, glucose syrups, biofuels and organic acids makes possible manufacturing plastic and other products. To realize the Russia's potential in manufacturing high-value-added agricultural products, it is necessary to provide state support for investment projects for wheat deep processing through preferential lending and taxation, and co-financing of projects. The strategic goal of the Russian agribusiness in the medium and long term should be changing the structure of manufacturing and export in order to export finished products, but not raw materials. Practical implications: The results of this research could be introduced in the process of strategic planning of the agribusiness development and import substitution policy in Russia. Originality/Value: The key contribution of this study lies in the findings of the advanced grain processing industries’ analysis in Russia with the regional aspects taken into account.peer-reviewe
High-resolution radio imaging of two luminous quasars beyond redshift 4.5
Context. Radio-loud active galactic nuclei in the early Universe are rare.
The quasars J0906+6930 at redshift z=5.47 and J2102+6015 at z=4.57 stand out
from the known sample with their compact emission on milliarcsecond (mas)
angular scale with high (0.1-Jy level) flux densities measured at GHz radio
frequencies. This makes them ideal targets for very long baseline
interferometry (VLBI) observations. Aims. By means of VLBI imaging we can
reveal the inner radio structure of quasars and model their brightness
distribution to better understand the geometry of the jet and the physics of
the sources. Methods. We present sensitive high-resolution VLBI images of
J0906+6930 and J2102+6015 at two observing frequencies, 2.3 and 8.6 GHz. The
data were taken in an astrometric observing programme involving a global
five-element radio telescope array. We combined the data from five different
epochs from 2017 February to August. Results. For one of the highest redshift
blazars known, J0906+6930, we present the first-ever VLBI image obtained at a
frequency below 8 GHz. Based on our images at 2.3 and 8.6 GHz, we confirm that
this source has a sharply bent helical inner jet structure within ~3 mas from
the core. The quasar J2102+6015 shows an elongated radio structure in the
east-west direction within the innermost ~2 mas that can be described with a
symmetric three-component brightness distribution model at 8.6 GHz. Because of
their non-pointlike mas-scale structure, these sources are not ideal as
astrometric reference objects. Our results demonstrate that VLBI observing
programmes conducted primarily with astrometric or geodetic goals can be
utilized for astrophysical purposes as well.Comment: 8 pages, 3 figures, accepted for publication in Astronomy &
Astrophysic
Electroweak gauge boson production at hadron colliders through O(alpha_s^2)
We describe a calculation of the O(alpha_s^2) QCD corrections to the fully
differential cross section for W and Z boson production in hadronic collisions.
The result is fully realistic in that it includes spin correlations, finite
width effects, gamma-Z interference and allows for the application of arbitrary
cuts on the leptonic decay products of the W and Z. We have implemented this
calculation into a numerical program. We demonstrate the use of this code by
presenting phenomenological results for several future LHC analyses and recent
Tevatron measurements, including the W cross section in the forward rapidity
region and the central over forward cross section ratio.Comment: 11 pages, 4 figure
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