From Sun to Interplanetary Space: What is the Pathlength of Solar Energetic Particles?

Solar energetic particles (SEPs), accelerated during solar eruptions, propagate in turbulent solar wind before being observed with in situ instruments. In order to interpret their origin through comparison with remote sensing observations of the solar eruption, we thus must deconvolve the transport effects due to the turbulent magnetic fields from the SEP observations. Recent research suggests that the SEP propagation is guided by the turbulent meandering of the magnetic fieldlines across the mean magnetic field. However, the lengthening of the distance the SEPs travel, due to the fieldline meandering, has so far not been included in SEP event analysis. This omission can cause significant errors in estimation of the release times of SEPs at the Sun. We investigate the distance traveled by the SEPs by considering them to propagate along fieldlines that meander around closed magnetic islands that are inherent in turbulent plasma. We introduce a fieldline random walk model which takes into account the physical scales associated to the magnetic islands. Our method remedies the problem of the diffusion equation resulting in unrealistically short pathlengths, and the fractal dependence of the pathlength of random walk on the length of the random-walk step. We find that the pathlength from the Sun to 1au can be below the nominal Parker spiral length for SEP events taking place at solar longitudes 45E to 60W, whereas the western and behind-the-limb particles can experience pathlengths longer than 2au due to fieldline meandering

Stars were born in significantly denser regions in the early Universe

The density of the warm ionized gas in high-redshift galaxies is known to be higher than what is typical in local galaxies on similar scales. At the same time, the mean global properties of the high- and low-redshift galaxies are quite different. Here, we present a detailed differential analysis of the ionization parameters of 14 star-forming galaxies at redshift 2.6-3.4, compiled from the literature. For each of those high-redshift galaxies, we construct a comparison sample of low-redshift galaxies closely matched in specific star formation rate (sSFR) and stellar mass, thus ensuring that their global physical conditions are similar to the high-redshift galaxy. We find that the median log [OIII] 5007/ [OII] 3727 line ratio of the high-redshift galaxies is 0.5 dex higher than their local counterparts. We construct a new calibration between the [OIII] 5007/ [OII] 3727 emission line ratio and ionization parameter to estimate the difference between the ionization parameters in the high and low-redshift samples. Using this, we show that the typical density of the warm ionized gas in star-forming regions decreases by a median factor of $7.1^{+10.2}_{-5.4}$ from z ~ 3.3 to z ~ 0 at fixed mass and sSFR. We show that metallicity differences cannot explain the observed density differences. Because the high- and low-redshift samples are comparable in size, we infer that the relationship between star formation rate density and gas density must have been significantly less efficient at z ~2-3 than what is observed in nearby galaxies with similar levels of star formation activity.Comment: 16 pages, 6 figures, accepted for publication in Ap

Vortex-strings in N=2 quiver X U(1) theories

We study half-BPS vortex-strings in four dimensional N=2 supersymmetric quiver theories with gauge group SU(N)^n X U(1). The matter content of the quiver can be represented by what we call a tetris diagram, which simplifies the analysis of the Higgs vacua and the corresponding strings. We classify the vacua of these theories in the presence of a Fayet-Iliopoulos term, and study strings above fully-Higgsed vacua. The strings are studied using classical zero modes analysis, supersymmetric localization and, in some cases, also S-duality. We analyze the conditions for bulk-string decoupling at low energies. When the conditions are satisfied, the low energy theory living on the string's worldsheet is some 2d N=(2,2) supersymmetric non-linear sigma model. We analyze the conditions for weak to weak 2d-4d map of parameters, and identify the worldsheet theory in all the cases where the map is weak to weak. For some SU(2) quivers, S-duality can be used to map weakly coupled worldsheet theories to strongly coupled ones. In these cases, we are able to identify the worldsheet theories also when the 2d-4d map of parameters is weak to strong.Comment: 61 pages, 10 figure

Merger Policies and Trade Liberalization

This paper is about the interactions between what is traditionally considered trade policy and a narrow but important aspect of competition policy, namely merger policy. We focus on links between merger policies and trade liberalization. We put special emphasis on the topical issue of the role that international agreements such as the GATT play when merger policies are nationally chosen. Of particular concern is the possibility that liberalization of international trade will induce countries to increasingly use competition policies to promote national interests at the expense of others. We examine the incentives for a welfare maximizing government to make such a substitution. Interpreting merger policy as a choice of degree of industrial concentration, we investigate how the merger policy that is optimal from the point of view of an individual country is affected by restrictions on the use of tariffs and export subsidies.

Severity as a Priority Setting Criterion: Setting a Challenging Research Agenda

Priority setting in health care is ubiquitous and health authorities are increasingly recognising the need for priority setting guidelines to ensure efficient, fair, and equitable resource allocation. While cost-effectiveness concerns seem to dominate many policies, the tension between utilitarian and deontological concerns is salient to many, and various severity criteria appear to fill this gap. Severity, then, must be subjected to rigorous ethical and philosophical analysis. Here we first give a brief history of the path to today’s severity criteria in Norway and Sweden. The Scandinavian perspective on severity might be conducive to the international discussion, given its long-standing use as a priority setting criterion, despite having reached rather different conclusions so far. We then argue that severity can be viewed as a multidimensional concept, drawing on accounts of need, urgency, fairness, duty to save lives, and human dignity. Such concerns will often be relative to local mores, and the weighting placed on the various dimensions cannot be expected to be fixed. Thirdly, we present what we think are the most pertinent questions to answer about severity in order to facilitate decision making in the coming years of increased scarcity, and to further the understanding of underlying assumptions and values that go into these decisions. We conclude that severity is poorly understood, and that the topic needs substantial further inquiry; thus we hope this article may set a challenging and important research agenda

Toward the Semiclassical Theory of the High Energy Heavy Ion Collisions

Sudden deposition of energy at the early stage of high energy heavy ion collisions makes virtual gluon fields real. The same is true for virtual vacuum fields $under$ the topological barrier, excited to real states $at$ or $above$ the barrier, gluomagnetic clusters of particular structure related to the $sphalerons$ of the electroweak theory. Semiclassically, these states play the role of the {\em ``turning points''}. After being produced they explode into a spherical shell of coherent field which then turn into several outgoing gluons. Furthermore, this explosions promptly produce quark pairs, as seen from explicit solution of the Dirac equation. The masses of such clusters depend on their size, and are expected to peak at $M\sim 3 GeV$. After we briefly review those consepts in a non-technical manner, we discuss what observable consequences the production of such clusters would make in the context of heavy ion collisions, especially at the RHIC energies. We discuss entropy and especially quark production, event-by-event fluctuations in collective effects like radial and elliptic flows and $J/\psi$ suppression. Coherent fields and their geometry increase the jet quenching, and we also point out the existene of ``explosive edge'' which jump-start collective effects and may affect unusual phenomena seen at RHIC at large $p_t$.Comment: Third version, substantially changed adding new sections and eliminating large part on jet quenching of the paper which brunched into a separate pape

Components of the gravitational force in the field of a gravitational wave

Gravitational waves bring about the relative motion of free test masses. The detailed knowledge of this motion is important conceptually and practically, because the mirrors of laser interferometric detectors of gravitational waves are essentially free test masses. There exists an analogy between the motion of free masses in the field of a gravitational wave and the motion of free charges in the field of an electromagnetic wave. In particular, a gravitational wave drives the masses in the plane of the wave-front and also, to a smaller extent, back and forth in the direction of the wave's propagation. To describe this motion, we introduce the notion of `electric' and `magnetic' components of the gravitational force. This analogy is not perfect, but it reflects some important features of the phenomenon. Using different methods, we demonstrate the presence and importance of what we call the `magnetic' component of motion of free masses. It contributes to the variation of distance between a pair of particles. We explicitely derive the full response function of a 2-arm laser interferometer to a gravitational wave of arbitrary polarization. We give a convenient description of the response function in terms of the spin-weighted spherical harmonics. We show that the previously ignored `magnetic' component may provide a correction of up to 10 %, or so, to the usual `electric' component of the response function. The `magnetic' contribution must be taken into account in the data analysis, if the parameters of the radiating system are not to be mis-estimated.Comment: prints to 29 pages including 9 figures, new title, additional explanations and references in response to referee's comments, to be published in Class. Quant. Gra

Regulation, institutions and commitment : the Jamaican telecommunications sector

The Jamaican telecommunications sector today is much more dynamic than it was before and provides much better service. There is widespread skepticism about the current regulatory framework, which is criticized for encouraging a tight telecommunications monopoly, little administrative discretion, and continous price adjustments to satisfy what many see as a high rate of return requirement. But the authors suggest that the regulatory framework is a"second-best"alternative, a pragmatic response to The Jamaican's institutional realities. The authors analyze why the reforms of the late 1980s took the form they did, and whether they could have been better. They find that the changing nature of regulatory institutions, ownership arrangements, and sector performance in the past 50 years is traceable to intense contracting problems between firms or interest groups and the government. Attempts to resolves these contracting problems have continuously constrained the government's (and firms) ability to implement efficient pricing schemes. In the abstract, The Jamaican's regulatory structure looks inefficient. In the context of The Jamaican's political system, politics, judiciary, bureaucracy, and interest groups, the regulatory framework developed in the late 1980s emerges as a fairly pragmatic, welfare-improving set of policies. Perhaps it could have been better, but its current design reflects basic commitment problems the government has with public utilities.Public Sector Economics&Finance,Economic Theory&Research,National Governance,Environmental Economics&Policies,ICT Policy and Strategies