22,383 research outputs found
Dark Matter CMB Constraints and Likelihoods for Poor Particle Physicists
The cosmic microwave background provides constraints on the annihilation and
decay of light dark matter at redshifts between 100 and 1000, the strength of
which depends upon the fraction of energy ending up in the form of electrons
and photons. The resulting constraints are usually presented for a limited
selection of annihilation and decay channels. Here we provide constraints on
the annihilation cross section and decay rate, at discrete values of the dark
matter mass, for all the annihilation and decay channels whose secondary
spectra have been computed using PYTHIA in arXiv:1012.4515 ("PPPC4DMID: A Poor
Particle Physicist Cookbook for Dark Matter Indirect Detection"), namely e, mu,
tau, V -> e, V -> mu, V -> tau, u, d, s, c, b, t, gamma, g, W, Z and h. By
interpolating in mass, these can be used to find the CMB constraints and
likelihood functions from WMAP7 and Planck for a wide range of dark matter
models, including those with annihilation or decay into a linear combination of
different channels.Comment: 8 pages, 5 figures, 2 tables. v2: some additional discussion and
references; submitted to PRD v3: some further discussion added in response to
referee's comments. Withdrawn from PRD before refereeing due to disagreement
over the title, matches version accepted by JCAP v4: fixes a textual typo
found in proof, correctly refers to the example channel in Fig 4 (mu, not e),
as per erratum sent to JCA
International Trade Between Consumer and Conservationist Countries
We consider trade between a consumer' country with an open access renewable resource and a conservationist' country that regulates resource harvesting to maximize domestic steady-state utility. In what we call the mild overuse' case, the consumer country exports the resource good and suffers steady-state losses from trade, as suggested by the conventional wisdom' that weak resource management standards confer a competitive advantage on domestic firms in the resource sector but cause welfare losses. Strikingly, however, when the resource stock is most in jeopardy, the conservationist country exports the resource good in steady state and both countries experience gains from trade.
Tectonic setting of Martian volcanoes and deep-seated intrusives
More than 50 volcanoes have been mapped on Mars, and recent geologic studies indicate structural evidence of deep seated intrusive bodies. Most volcanoes in the Tharsis region are volcanotectonic features; they have been associated with large scale tectonic and volcanic processes. They occur along complex systems of faults and grabens having a dominant northwest to southwest trend closely coincident with a great circle, which extends along 90 deg of arc from Tempe Patera to probable volcanic mountains near lat. 40 deg S, long. 150 deg. Deep seated intrusive bodies are also concentrated in the Tharsis region and are recognized mostly where faults have been deflected around their cores. The Elysium Mons-Amphitrites Patera volcanic alignment is subparallel to that of Tharsis but is longer, extending through about 120 deg of arc; it transects the dichotomy boundary and is radial to the Hellas basin. Volcanoes in the Tharsis region have the widest age range of all volcanoes on Mars, as determined by the size-frequency distribution of their craters having diameters of 2, 5, and 16 km
Numerical solution of periodic vortical flows about a thin airfoil
A numerical method is developed for computing periodic, three-dimensional, vortical flows around isolated airfoils. The unsteady velocity is split into a vortical component which is a known function of the upstream flow conditions and the Lagrangian coordinates of the mean flow, and an irrotational field whose potential satisfies a nonconstant-coefficient, inhomogeneous, convective wave equation. Solutions for thin airfoils at zero degrees incidence to the mean flow are presented in this paper. Using an elliptic coordinate transformation, the computational domain is transformed into a rectangle. The Sommerfeld radiation condition is applied to the unsteady pressure on the grid line corresponding to the far field boundary. The results are compared with a Possio solver, and it is shown that for maximum accuracy the grid should depend on both the Mach number and reduced frequency. Finally, in order to assess the range of validity of the classical thin airfoil approximation, results for airfoils with zero thickness are compared with results for airfoils with small thickness
Numerical solutions of the linearized Euler equations for unsteady vortical flows around lifting airfoils
A linearized unsteady aerodynamic analysis is presented for unsteady, subsonic vortical flows around lifting airfoils. The analysis fully accounts for the distortion effects of the nonuniform mean flow on the imposed vortical disturbances. A frequency domain numerical scheme which implements this linearized approach is described, and numerical results are presented for a large variety of flow configurations. The results demonstrate the effects of airfoil thickness, angle of attack, camber, and Mach number on the unsteady lift and moment of airfoils subjected to periodic vortical gusts. The results show that mean flow distortion can have a very strong effect on the airfoil unsteady response, and that the effect depends strongly upon the reduced frequency, Mach number, and gust wave numbers
A finite-difference, frequency-domain numerical scheme for the solution of the linearized unsteady Euler equations
A numerical method is developed for solving periodic, three-dimensional, vortical flows around lifting airfoils in subsonic flow. The first-order method, that is presented, fully accounts for the distortion effects of the nonuniform mean flow on the convected upstream vortical disturbances. The unsteady velocity is split into a vortical component which is a known function of the upstream flow conditions and the Lagrangian coordinates of the mean flow, and an irrotational field whose potential satisfies a nonconstant-coefficient, inhomogeneous, convective wave equation. Using an elliptic coordinate transformation, the unsteady boundary value problem is solved in the frequency domain on grids which are determined as a function of the Mach number and reduced frequency. Extensive comparisons are made with known solutions to unsteady vortical flow problems, and it is seen that the agreement is generally very good for reduced frequencies ranging from 0 up to 4
International Trade and Open Access Renewable Resources: The Small Open Economy Case
This paper develops a two-sector general equilibrium model of an economy with an open access renewable resource. We characterize the autarkic steady state, showing that autarky prices (and 'comparative advantage') are determined by the ratio of intrinsic resource growth to labor. Under free trade, steady state trade and production patterns for a small open economy are determined by whether the resource good's world price exceeds its autarky price. Strikingly, if the small country exports the resource good while remaining diversified, then steady-state utility is lower than in autarky, and increases in the world price of exports are welfare-reducing.
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