86,181 research outputs found
Kinetics of the reaction OH (v equals 0) plus O3 yields HO2 plus O2
The rate constant (kl) of the reaction OH(v=o) + O3 yields HO2 + O2 measured over the temperature range 220 to 450 K at total pressures between 2 and 5 torr using ultraviolet fluorescent scattering for the detection of OH radicals. An Arrhenius expression was obtained, and the rate constant for the reaction HO2 + O3 yields OH + 2O2 was inferred to be less than 0.1 kl over the entire temperature interval
Capturing the Shape of Business Cycles with Nonlinear Autoregressive Leading Indicator Models.
This paper studies linear and linear autoregressive leading indicator models of business cycles in OECD countries. The models use the spread between short-term and long-term interest rates as leading indicators for GDP, and their success in capturing business cycles gauged by the non-parametric procedures developed by Harding and Pagan (2001). Our preliminary findings indicate that bivariate nonlinear models of output and the interest rate spread can successfully capture the shape of the business cycle. In particular, they can capture the features of recession and the deviation of the actual path of the cycles from a triangular approximation to this path, both characteristics that other models of GDP fail to reproduce.Business Cycles; Leading Indicators; Nonlinear Models; Yield Spread
Finite time distributions of stochastically modeled chemical systems with absolute concentration robustness
Recent research in both the experimental and mathematical communities has
focused on biochemical interaction systems that satisfy an "absolute
concentration robustness" (ACR) property. The ACR property was first discovered
experimentally when, in a number of different systems, the concentrations of
key system components at equilibrium were observed to be robust to the total
concentration levels of the system. Followup mathematical work focused on
deterministic models of biochemical systems and demonstrated how chemical
reaction network theory can be utilized to explain this robustness. Later
mathematical work focused on the behavior of this same class of reaction
networks, though under the assumption that the dynamics were stochastic. Under
the stochastic assumption, it was proven that the system will undergo an
extinction event with a probability of one so long as the system is
conservative, showing starkly different long-time behavior than in the
deterministic setting. Here we consider a general class of stochastic models
that intersects with the class of ACR systems studied previously. We consider a
specific system scaling over compact time intervals and prove that in a limit
of this scaling the distribution of the abundances of the ACR species converges
to a certain product-form Poisson distribution whose mean is the ACR value of
the deterministic model. This result is in agreement with recent conjectures
pertaining to the behavior of ACR networks endowed with stochastic kinetics,
and helps to resolve the conflicting theoretical results pertaining to
deterministic and stochastic models in this setting
Expansion of a Fermi gas interacting with a Bose-Einstein condensate
We study the expansion of an atomic Fermi gas interacting attractively with a
Bose-Einstein condensate. We find that the interspecies interaction affects
dramatically both the expansion of the Fermi gas and the spatial distribution
of the cloud in trap. We observe indeed a slower evolution of the
radial-to-axial aspect ratio which reveals the importance of the mutual
attraction between the two samples during the first phase of the expansion. For
large atom numbers, we also observe a bimodal momentum distribution of the
Fermi gas, which reflects directly the distribution of the mixture in trap.
This effect allows us to extract information on the dynamics of the system at
the collapse.Comment: 4 pages, 4 figure
Spontaneous superconductivity and optical properties of high-Tc cuprates
We suggest that the high temperature superconductivity in cuprate compounds
may emerge due to interaction between copper-oxygen layers mediated by in-plane
plasmons. The strength of the interaction is determined by the c-axis geometry
and by the ab-plane optical properties. Without making reference to any
particular in-plane mechanism of superconductivity, we show that the interlayer
interaction favors spontaneous appearance of the superconductivity in the
layers. At a qualitative level the model describes correctly the dependence of
the transition temperature on the interlayer distance, and on the number of
adjacent layers in multilayered homologous compounds. Moreover, the model has a
potential to explain (i) a mismatch between the optimal doping levels for
critical temperature and superconducting density and (ii) a universal scaling
relation between the dc-conductivity, the superfluid density, and the
superconducting transition temperature.Comment: 4.4 pages, 2 figures; v2 matches the published version (clarifying
remarks and references are added
Mapping Kitaev's quantum double lattice models to Levin and Wen's string-net models
We exhibit a mapping identifying Kitaev's quantum double lattice models
explicitly as a subclass of Levin and Wen's string net models via a completion
of the local Hilbert spaces with auxiliary degrees of freedom. This
identification allows to carry over to these string net models the
representation-theoretic classification of the excitations in quantum double
models, as well as define them in arbitrary lattices, and provides an
illustration of the abstract notion of Morita equivalence. The possibility of
generalising the map to broader classes of string nets is considered.Comment: 8 pages, 6 eps figures; v2: matches published versio
Quantum Monte Carlo study of confined fermions in one-dimensional optical lattices
Using quantum Monte Carlo (QMC) simulations we study the ground-state
properties of the one-dimensional fermionic Hubbard model in traps with an
underlying lattice. Since due to the confining potential the density is space
dependent, Mott-insulating domains always coexist with metallic regions, such
that global quantities are not appropriate to describe the system. We define a
local compressibility that characterizes the Mott-insulating regions and
analyze other local quantities. It is shown that the momentum distribution
function, a quantity that is commonly considered in experiments, fails in
giving a clear signal of the Mott-insulator transition. Furthermore, we analyze
a mean-field approach to these systems and compare it with the numerically
exact QMC results. Finally, we determine a generic form for the phase diagram
that allows us to predict the phases to be observed in the experiments.Comment: RevTex file, 13 pages, 19 figures, published versio
YF-12 cooperative airframe/propulsion control system program, volume 1
Several YF-12C airplane analog control systems were converted to a digital system. Included were the air data computer, autopilot, inlet control system, and autothrottle systems. This conversion was performed to allow assessment of digital technology applications to supersonic cruise aircraft. The digital system was composed of a digital computer and specialized interface unit. A large scale mathematical simulation of the airplane was used for integration testing and software checkout
Charge-Spin Separation in 2D Fermi Systems: Singular Interactions as Modified Commutators, and Solution of 2D Hubbard Model in Bosonized Approximation
The general 2-dimensional fermion system with repulsive interactions
(typified by the Hubbard Model) is bosonized, taking into account the finite
on-shell forward scattering phase shift derived in earlier papers. By taking
this phase shift into account in the bosonic commutation relations a consistent
picture emerges showing the charge-spin separation and anomalous exponents of
the Luttinger liquid.Comment: Latex file 14 pages. email: [email protected]
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