Issues in the Taxation of Foreign Source Income

This paper examines some aspects of the tax treatment of U.S. multinational corporations. The emphasis is on problems of coordination of the different tax systems faced by the firms. The U.S. corporate income tax must take account of the fact that the firms' over- seas income is taxed by the host governments, in a variety of ways. Currently, the foreign tax credit is the principle mechanism for making these adjustments; it is examined, along with alternative methods such as territorial treatment and a deduction for foreign taxes. The paper also considers the closely related question of coordinating measures of taxable income. The most common method, the arm's length rule, is examined. Alternatives to it, including allocation by shares and a partial case involving allocation of research and development expenses, are also considered. First, the revenue effects of these tax regimes are simulated, with no behavioral responses considered. Responses in location of investment decisions are then included. The data are taken from the corporations' U.S. tax returns, cross-tabulated into approximately 240 industry and country cells.

A critical analysis of vacancy-induced magnetism in mono and bilayer graphene

The observation of intrinsic magnetic order in graphene and graphene-based materials relies on the formation of magnetic moments and a sufficiently strong mutual interaction. Vacancies are arguably considered the primary source of magnetic moments. Here we present an in-depth density functional theory study of the spin-resolved electronic structure of (monoatomic) vacancies in graphene and bilayer graphene. We use two different methodologies: supercell calculations with the SIESTA code and cluster-embedded calculations with the ALACANT package. Our results are conclusive: The vacancy-induced extended $\pi$ magnetic moments, which present long-range interactions and are capable of magnetic ordering, vanish at any experimentally relevant vacancy concentration. This holds for $\sigma$-bond passivated and un-passivated reconstructed vacancies, although, for the un-passivated ones, the disappearance of the $\pi$ magnetic moments is accompanied by a very large magnetic susceptibility. Only for the unlikely case of a full $\sigma$-bond passivation, preventing the reconstruction of the vacancy, a full value of 1$\mu_B$ for the $\pi$ extended magnetic moment is recovered for both mono and bilayer cases. Our results put on hold claims of vacancy-induced ferromagnetic or antiferromagnetic order in graphene-based systems, while still leaving the door open to $\sigma$-type paramagnetism.Comment: Submitted to Phys. Rev B, 9 page

Complex-space singularities of 2D Euler flow in Lagrangian coordinates

We show that, for two-dimensional space-periodic incompressible flow, the solution can be evaluated numerically in Lagrangian coordinates with the same accuracy achieved in standard Eulerian spectral methods. This allows the determination of complex-space Lagrangian singularities. Lagrangian singularities are found to be closer to the real domain than Eulerian singularities and seem to correspond to fluid particles which escape to (complex) infinity by the current time. Various mathematical conjectures regarding Eulerian/Lagrangian singularities are presented.Comment: 5 pages, 2 figures, submitted to Physica

The Sun's Journey Through the Local Interstellar Medium: The PaleoLISM and Paleoheliosphere

Over the recent past, the galactic environment of the Sun has differed substantially from today. Sometime within the past ~130,000 years, and possibly as recent as ~56,000 years ago, the Sun entered the tenuous tepid partially ionized interstellar material now flowing past the Sun. Prior to that, the Sun was in the low density interior of the Local Bubble. As the Sun entered the local ISM flow, we passed briefly through an interface region of some type. The low column densities of the cloud now surrounding the solar system indicate that heliosphere boundary conditions will vary from opacity considerations alone as the Sun moves through the cloud. These variations in the interstellar material surrounding the Sun affected the paleoheliosphere.Comment: To be published in Astrophysics and Space Sciences Transactions (ASTRA), for the proceedings of the workshop "Future Perspectives in Heliospheric Research: Unsolved Problems, New Missions - New Sciences" Bad Honnef, Germany, April 6-8, 2005, held in honor of Prof. Hans Fahr's 65th birthda

Kicked Burgers Turbulence

Burgers turbulence subject to a force $f(x,t)=\sum_jf_j(x)\delta(t-t_j)$, where the $t_j$'s are ``kicking times'' and the ``impulses'' $f_j(x)$ have arbitrary space dependence, combines features of the purely decaying and the continuously forced cases. With large-scale forcing this ``kicked'' Burgers turbulence presents many of the regimes proposed by E, Khanin, Mazel and Sinai (1997) for the case of random white-in-time forcing. It is also amenable to efficient numerical simulations in the inviscid limit, using a modification of the Fast Legendre Transform method developed for decaying Burgers turbulence by Noullez and Vergassola (1994). For the kicked case, concepts such as ``minimizers'' and ``main shock'', which play crucial roles in recent developments for forced Burgers turbulence, become elementary since everything can be constructed from simple two-dimensional area-preserving Euler--Lagrange maps. One key result is for the case of identical deterministic kicks which are periodic and analytic in space and are applied periodically in time: the probability densities of large negative velocity gradients and of (not-too-large) negative velocity increments follow the power law with -7/2 exponent proposed by E {\it et al}. (1997) in the inviscid limit, whose existence is still controversial in the case of white-in-time forcing. (More in the full-length abstract at the beginning of the paper.)Comment: LATEX 30 pages, 11 figures, J. Fluid Mech, in pres

Clinical and Procedural Effects of Transitioning to Contact Force Guided Ablation for Atrial Fibrillation.

Background: A major innovation in atrial fibrillation (AF) ablation has been the introduction of contact force (CF) sensing catheters. Objective: To evaluate procedural and clinical effects of transitioning to CF-guided AF ablation. Methods: Consecutive AF ablation patients were studiedduring the period of time of transitioning from a non-CF to CF sensing catheter. Procedural data recorded was total radiofrequency time, time to isolate the left pulmonary veins (LPVs), and time to isolate the right pulmonary veins (RPVs). Clinically, the 3 and 12-month maintenance of sinus rhythm was noted and compared by: paroxysmal vs. persistent AF; CT scan LA volume more or less than 150 cc; CHA2DS2VASC more or less than 2; and LVEF more or less than 55%. Safety data was recorded as well. Results: Total ablation times were shorter (113 vs.146 min, p=0.011)when using the CF catheters compared to non-CF ablations. This was driven by a decrease in both LPV (46 vs.72 min, p\u3c0.001) and RPV time (54 vs. 75 min, p=0.002).The use of CF catheter did not change the overall percentage of patients in sinus rhythm at 3 and 12-months of follow up. However, sinus rhythm was more frequent at 12 months with CF ablation inpatients with an LA volume of more than 150 cc when compared to non-CF ablation (84.6% and 52.4%, p=0.03). There was no difference in outcomes with stratification by CHA2DS2VASC score or LVEF. No significant difference in complications was noted. Conclusions: For AF ablation, the initial use of CF-sensing technology reduced procedure times with similar overall sinus rhythm maintenance at 3 and 12 months. CF improved 12-month outcomes in patients with an enlarged LA

Singularities of Euler flow? Not out of the blue!

Does three-dimensional incompressible Euler flow with smooth initial conditions develop a singularity with infinite vorticity after a finite time? This blowup problem is still open. After briefly reviewing what is known and pointing out some of the difficulties, we propose to tackle this issue for the class of flows having analytic initial data for which hypothetical real singularities are preceded by singularities at complex locations. We present some results concerning the nature of complex space singularities in two dimensions and propose a new strategy for the numerical investigation of blowup.(A version of the paper with higher-quality figures is available at http://www.obs-nice.fr/etc7/complex.pdf)Comment: RevTeX4, 10 pages, 9 figures. J.Stat.Phys. in press (updated version