Direct photon interferometry

We consider recent developments in the theory of the two-photon interferometry in ultrarelativistic heavy ion collisions with emphasis on the difference between photon and hadron interferometry. We review the available experimental results and discuss possibilities of measurement of the photon Bose-Einstein correlations in ongoing and future experiments.Comment: 6 pages, prepared for the Proceedings of Workshop on Particle Correlations and Femtoscopy (WPCF), Kromeriz, Czech Republic, August 15-17, 2005. Ref. adde

Direct Numerical Simulations of Low-RmRm MHD turbulence based on the least dissipative modes

We present a new spectral method for the Direct Numerical Simulation of Magnetohydrodynamic turbulence at low Magnetic Reynolds number. The originality of our approach is that instead of using traditional bases of functions, it relies on the basis of eigenmodes of the dissipation operator, which represents viscous and Joule dissipation. We apply this idea to the simple case of a periodic domain in the three directions of space, with an homogeneous magnetic field in the $\mathbf e_z$ direction. The basis is then still as subset of the Fourier space, but ordered by growing linear decay rate $|\lambda|$ (\emph{i.e} according to the \emph{least dissipative modes}). We show that because the lines of constant energy tend to follow those of constant $|\lambda|$ in the Fourier space, the scaling for the the smallest scales $|\lambda^{\rm max}|$ in a forced flow can be expressed using this single parameter, as a function of the Reynolds number as \sqrt{|\lambda^{\rm max}|}/(2\pi k_f)\simeq 0.5\Rey^{1/2}, where $k_f$ is the forcing wavelength, or as a function of the Grashof number \Gr_f, which gives a non-dimensional measure of the forcing, as |\lambda^{\rm max}|^{1/2}/(2\pi k_f)\simeq 0.47\Gr_f^{0.20}. This scaling is also found consistent with heuristic scalings, and which we are able to numerically quantify as k_\perp^{\rm max}/k_f\simeq 0.5 \Rey^{1/2} and k_z^{\rm max}/k_f\simeq 0.8k_f \Rey/Ha. Finally, we show that the set of least dissipative modes gives a relevant prediction for the scale of the first three-dimensional structure to appear in a forced, initially two-dimensional turbulent flow. This completes our numerical demonstration that the least dissipative modes can be used to simulate both two- and three-dimensional low-Rm MHD flows.Comment: 24 pages. Article accepted for publication in the Journal of Fluid Mechanic

Challenging Direct Democracy

I want to argue today that direct democracy is undesirable and unconstitutional. I want to argue to you that the Supreme Court should find that the Michigan Civil Rights Initiative is unconstitutional, and strike it down. So I want to make two points. First, I am going to argue that direct democracy is undesirable. This is a normative argument; it’s not an argument about constitutional doctrine. Second, I want to argue that direct democracy is unconstitutional, and make a series of different arguments as to why

Direct Cause

An interventionist account of causation characterizes causal relations in terms of changes resulting from particular interventions. We provide an example of a causal relation for which there does not exist an intervention satisfying the common interventionist standard. We consider adaptations that would save this standard and describe their implications for an interventionist account of causation. No adaptation preserves all the aspects that make the interventionist account appealing

Cosmic rays: direct measurements

This paper is based on the rapporteur talk given at the 34$^{th}$ International Cosmic Ray Conference (ICRC), on August 6$^{th}$, 2015. The purpose of the talk and paper is to provide a summary of the most recent results from balloon-borne and space-based experiments presented at the conference, and give an overview of the future missions and developments foreseen in this field.Comment: Write-up of the rapporteur talk given at the 34th International Cosmic Ray Conference, 30 July-6 August, 2015, The Hague, The Netherlands. 24 pages , 11 figure

6Li direct breakup lifetimes

alpha-d coincidence data were studied for the 6Li + 59Co reaction at E(lab) = 29.6 MeV. By using a kinematic analysis, it was possible to identify which process, leading to the same final state, has the major contribution for each of the selected angular regions. Contributions of the 6Li sequential and direct breakup to the incomplete fusion/transfer process were discussed by considering the lifetimes obtained by using a semiclassical approach, for both breakup components.Comment: 5 pages, 4 figures, Invited Talk (Parrallel Sessions) of A. Szanto de Toledo, prepared for the Proccedings of the 10th International Conference on Nucleus-Nucleus Collisions, August 16-21, 2009, Beijing, China; submitted to Nucl. Phys. A (Proceedings of NN2009