277 research outputs found
Stochastic Wave-Function Simulation of Irreversible Emission Processes for Open Quantum Systems in a Non-Markovian Environment
When conducting the numerical simulation of quantum transport, the main
obstacle is a rapid growth of the dimension of entangled Hilbert subspace. The
Quantum Monte Carlo simulation techniques, while being capable of treating the
problems of high dimension, are hindered by the so-called "sign problem". In
the quantum transport, we have fundamental asymmetry between the processes of
emission and absorption of environment excitations: the emitted excitations are
rapidly and irreversibly scattered away. Whereas only a small part of these
excitations is absorbed back by the open subsystem, thus exercising the
non-Markovian self-action of the subsystem onto itself. We were able to devise
a method for the exact simulation of the dominant quantum emission processes,
while taking into account the small backaction effects in an approximate
self-consistent way. Such an approach allows us to efficiently conduct
simulations of real-time dynamics of small quantum subsystems immersed in
non-Markovian bath for large times, reaching the quasistationary regime. As an
example we calculate the spatial quench dynamics of Kondo cloud for a bozonized
Kodno impurity model.Comment: 7 pages, 3 figures, ICQT2017 Conference Proceedings; corrected a few
typos; accepted for publication in the AIP Conference Proceedings journa
Molecular and elemental composition of humic acids isolated from selected soils of the Russian Arctic
Humic substances, isolated from selected soils of the Russian Arctic, were ,+investigated in terms of molecular composition and stabilization rate. The degree of polar soil organic matter stabilization was assessed with the use of modern instrumental spectroscopy methods. The analysis of humic acid (HAs) preparations showed that aliphatic fragments prevail in the organic matter isolated in polar soils. The predominance of aliphatic fragments was revealed in HAs from soils located in the coastal zone, which could be caused by regular refreshment of organic matter during sin-lithogenic process and processes of hydrogenation in HAs. Breaking of the C-C bonds and formation of chains with a high hydrogen content, which leads to the formation of aliphatic fragments in HAs, were noted. Data on the calculated atomic ratios of the elements in HAs are given and graphs show the main regularities in the formation of HAs and their properties. The integrated indicators of the molecular composition of humic acids of soils of the Russian Arctic are presented. The paper contains 4 Tables, 4 Figures and 44 References
2 x 2 Polyethylene Reflected and Moderated Highly Enriched Uranium System with Rhenium
The 2 × 2 array HEU-Re experiment was performed on the Planet universal critical assembly machine on November 4th, 2003 at the Los Alamos Critical Experiments Facility (LACEF) at Los Alamos National Laboratory (LANL). For this experiment, there were 10 ½ units, each full unit containing four HEU foils and two rhenium foils. The top unit contained only two HEU foils and two rhenium foils. A total of 42 HEU foils were used for this experiment. Rhenium is a desirable cladding material for space nuclear power applications. This experiment consisted of HEU foils interleaved with rhenium foils and is moderated and reflected by polyethylene plates. A unit consisted of a polyethylene plate, which has a recess for rhenium foils, and four HEU foils in a single layer in the top recess of each polyethylene plate. The Planet universal criticality assembly machine has been previously used in experiments containing HEU foils interspersed with SiO2 (HEU-MET-THERM-001), Al (HEU-MET-THERM-008), MgO (HEU-MET-THERM-009), Gd foils (HEU-MET-THERM-010), 2 × 2 × 26 Al (HEU-MET-THERM-012), Fe (HEU-MET-THERM-013 and HEU-MET-THERM-015), 2 × 2 × 23 SiO2 (HEU-MET-THERM-014), 2 × 2 × 11 hastalloy plates (HEU-MET-THERM-016), and concrete (HEU-MET-THERM-018). The 2 × 2 array of HEU-Re is considered acceptable for use as a benchmark critical experiment
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2 x 2 Polyethylene Reflected and Moderated Highly Enriched Uranium System with Rhenium
The 2 × 2 array HEU-Re experiment was performed on the Planet universal critical assembly machine on November 4th, 2003 at the Los Alamos Critical Experiments Facility (LACEF) at Los Alamos National Laboratory (LANL). For this experiment, there were 10 ½ units, each full unit containing four HEU foils and two rhenium foils. The top unit contained only two HEU foils and two rhenium foils. A total of 42 HEU foils were used for this experiment. Rhenium is a desirable cladding material for space nuclear power applications. This experiment consisted of HEU foils interleaved with rhenium foils and is moderated and reflected by polyethylene plates. A unit consisted of a polyethylene plate, which has a recess for rhenium foils, and four HEU foils in a single layer in the top recess of each polyethylene plate. The Planet universal criticality assembly machine has been previously used in experiments containing HEU foils interspersed with SiO2 (HEU-MET-THERM-001), Al (HEU-MET-THERM-008), MgO (HEU-MET-THERM-009), Gd foils (HEU-MET-THERM-010), 2 × 2 × 26 Al (HEU-MET-THERM-012), Fe (HEU-MET-THERM-013 and HEU-MET-THERM-015), 2 × 2 × 23 SiO2 (HEU-MET-THERM-014), 2 × 2 × 11 hastalloy plates (HEU-MET-THERM-016), and concrete (HEU-MET-THERM-018). The 2 × 2 array of HEU-Re is considered acceptable for use as a benchmark critical experiment
Energy-Spin Trajectories in AdS_5 x S^5 from Semiclassical Vertex Operators
We study the relation between vertex operators in AdS_5 x S^5 and classical
spinning string solutions. In the limit of large quantum numbers the treatment
of vertex operators becomes semiclassical. In this regime, a given vertex
operator carrying a certain set of quantum numbers defines a singular solution.
We show in a number of examples that this solution coincides with the classical
string solution with the same quantum numbers but written in a different
two-dimensional coordinate system. The marginality condition imposed on an
operator yields a relation between the energy and the other quantum numbers
which is shown to coincide with that of the corresponding classical string
solution. We also argue that in some cases vertex operators in AdS_5 x S^5
cannot be given by expressions similar to the ones in flat space and a more
involved consideration is required.Comment: 23 pages, 1 Figur
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