15,396 research outputs found
The influence of line shape and band structure on temperatures in planetary atmospheres
Numerical experiments are performed to examine the effects of line shape and band structure on the radiative equilibrium temperature profile in planetary atmospheres. In order to accurately determine these effects, a method for calculating radiative terms is developed which avoids the usual approximations. It differs from the more commonly used methods in that it allows arbitrary dependence of the absorption coefficient on wave number, without requiring tedious line by line integration and without the constraints of band models. The present formulation is restricted to homogeneous atmospheres but the concept can be extended to the more general case. The numerical experiments reveal that the line shape and band structure of the absorbing gases have a large effect on temperatures in the higher layers of the atmosphere (corresponding to the stratosphere and mesosphere). The more nongrey the spectrum (that is, the higher the peaks and the deeper the troughs in the spectrum), the lower the temperature
mixing and transitions in isosinglet down quark model
The recent observation of the mass difference in system seems to be not
in complete agreement with the corresponding standard model value. We consider
the model with an extra vector like down quark to explain this discrepancy and
obtain the constraints on the new physics parameters. Thereafter, we show that
with these new constraints this model can successfully explain other observed
deviations associated with transitions, namely, ,
and .Comment: 19 pages, 6 figure
Controlling the neuronal balancing act: optical coactivation of excitation and inhibition in neuronal subdomains
Point-Defect Optical Transitions and Thermal Ionization Energies from Quantum Monte Carlo Methods: Application to F-center Defect in MgO
We present an approach to calculation of point defect optical and thermal
ionization energies based on the highly accurate quantum Monte Carlo methods.
The use of an inherently many-body theory that directly treats electron
correlation offers many improvements over the typically-employed density
functional theory Kohn-Sham description. In particular, the use of quantum
Monte Carlo methods can help overcome the band gap problem and obviate the need
for ad-hoc corrections. We demonstrate our approach to the calculation of the
optical and thermal ionization energies of the F-center defect in magnesium
oxide, and obtain excellent agreement with experimental and/or other
high-accuracy computational results
Targeted Export Promotion with Several Oligopolistic Industries
In this paper we ask whether a policy of targeted export promotion can raise domestic welfare when several oligopolistic industries all draw on the same scarce factor of production. Our point of departure is one of Cournot duopoly in which a single home firm competes with a single foreign firm in a market outside the horse country. It has been shown previously that when there is only one such industry in an otherwise perfectly competitive world economy, a subsidy policy by the home government transfers profits to the domestic firm, and thereby raises domestic welfare. However,when many such industries (and only these) utilize the same inelastically supplied resource, promotion of one bids up the return to the specific factor, and consequently disadvantages all of the non-targeted industries in their respective duopolistic competitions. Our question then is which industry(s), if any, is worthy of promotion. We find that, when the specific factor is used in fixed proportion to output, and all of the duopolies have similar demand and cost conditions, a policy of free trade is optimal. We identify the conditions for welfare improvement when a single industry is selected for targeting under asymmetric conditions, and also investigate whether a uniform subsidy to all industries in the imperfectly competitive sector will raise domestic welfare.
Quantum Monte Carlo for minimum energy structures
We present an efficient method to find minimum energy structures using energy
estimates from accurate quantum Monte Carlo calculations. This method involves
a stochastic process formed from the stochastic energy estimates from Monte
Carlo that can be averaged to find precise structural minima while using
inexpensive calculations with moderate statistical uncertainty. We demonstrate
the applicability of the algorithm by minimizing the energy of the H2O-OH-
complex and showing that the structural minima from quantum Monte Carlo
calculations affect the qualitative behavior of the potential energy surface
substantially.Comment: 7 pages, 4 figure
Trade and Protection with Multistage Production
This paper analyzes trade in manufactured goods that are produced via a vertical production structure with many stages, where some value is added at each to an intermediate product to yield a good-in-process ready for the next stage. We consider the stage at which a good is traded to be an economically endogenous variable, with comparative advantage determining the pattern of production specialization by stages across countries. We study how endowment changes and policy shifts move the margin of comparative advantage, which thus provides a channel for resource allocation adjustment that is additional to the usual ones of factor substitution and changes in the quantity of output.
Fast CP Violation
flavor tagging will be extensively studied at the asymmetric
factories due to its importance in CP asymmetry measurements. The primary
tagging modes are the semileptonic decays of the (lepton tag), or the
hadronic decays (kaon tag). We suggest that looking for time
dependent CP asymmetries in events where one is tagged leptonically and the
other one is tagged with a kaon could result in an early detection of CP
violation. Although in the Standard Model these asymmetries are expected to be
small, , they could be measured with about the same amount of data as
in the ``gold-plated'' decay . In the presence of physics
beyond the Standard Model, these asymmetries could be as large as ,
and the first CP violation signal in the system may show up in these
events. We give explicit examples of new physics scenarios where this occurs.Comment: 9 pages, revtex, no figures. Discussion of new physics effects on CP
violation with two lepton tags expanded. Factors of 2 correcte
MFV SUSY: A Natural Theory for R-Parity Violation
We present an alternative approach to low-energy supersymmetry. Instead of
imposing R-parity we apply the minimal flavor violation (MFV) hypothesis to the
R-parity violating MSSM. In this framework, which we call MFV SUSY, squarks can
be light and the proton long lived without producing missing energy signals at
the LHC. Our approach differs from that of Nikolidakis and Smith in that we
impose holomorphy on the MFV spurions. The resulting model is highly
constrained and R-parity emerges as an accidental approximate symmetry of the
low-energy Lagrangian. The size of the small R-parity violating terms is
determined by the flavor parameters, and in the absence of neutrino masses
there is only one renormalizable R-parity violating interaction: the
baryon-number violating superpotential term. Low energy
observables (proton decay, dinucleon decay and oscillation) pose
only mild constraints on the parameter space. LHC phenomenology will depend on
whether the LSP is a squark, neutralino, chargino or slepton. If the LSP is a
squark it will have prompt decays, explaining the non-observation of events
with missing transverse energy at the LHC.Comment: 41 pages, 14 figures; v3: minor corrections, matches published
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