High energy pA collisions in the color glass condensate approach I. Gluon production and the Cronin effect

We study gluon production in high energy proton-nucleus collisions in the semi-classical framework of the Color Glass Condensate. We develop a general formalism to compute gluon fields in covariant gauge to lowest order in the classical field of the proton and to all orders in the classical field of the nucleus. The use of the covariant gauge makes the diagrammatic interpretation of the solution more transparnt. k_t-factorization holds to this order for gluon production -- Our results for the gluon distribution are equivalent to the prior diagrammatic analysis of Kovchegov and Mueller. We also show that these results are equivalent to the computation of gluon production by Dumitru and McLerran in the Fock-Schwinger gauge. We demonstrate how the Cronin effect arises in this approach, and examine its behavior in the two extreme limits of a) no small-x quantum evolution, and b) fully saturated quantum evolution. In both cases, the formalism reduces to Glauber's formalism of multiple scatterings. We comment on the possible implications of this study for the interpretation of the recent results on Deuteron-Gold collisions at the Relativistic Heavy Ion Collider (RHIC).Comment: 46 pages, 12 postscript figure

The Victorian Naturalist

v.113 (1996

Working with single fathers in Western Siberia: a new departure in Russian social provision

No abstract available

Local Government Policy and Planning for Unmanned Aerial Systems

This research identifies key state and local government stakeholders in California for drone policy creation and implementation, and describes their perceptions and understanding of drone policy. The investigation assessed stakeholders’ positions, interests, and influence on issues, with the goal of providing potential policy input to achieve successful drone integration in urban environments and within the national airspace of the United States. The research examined regulatory priorities through the use of a two-tiered Stakeholder Analysis Process. The first tier consisted of a detailed survey sent out to over 450 local agencies and jurisdictions in California. The second tier consisted of an in-person focus group to discuss survey results as well as to gain deeper insights into local policymakers’ current concerns. Results from the two tiers of analysis, as well as recommendations, are provided here

Initial Conditions for Bubble Universes

The "bubble universes" of Coleman and De Luccia play a crucial role in string cosmology. Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions. In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for Inflation were established. We argue that the simplest non-anthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes. Casimir energy is a popular candidate for a quantum effect which can ensure this, but [because it violates energy conditions] there is a danger that it could lead to non-perturbative instabilities in string theory. We make a simple proposal for the initial conditions of a bubble universe, and show that our proposal ensures that the system is non-perturbatively stable. Thus, low-entropy conditions can be established at the beginning of a bubble universe without violating the Second Law of thermodynamics and without leading to instability in string theory. These conditions are inherited from the ambient spacetime.Comment: Further clarifications; 28 pages including three eps files. This is the final [accepted for publication] versio

Evaluation plan and recommendations - ‘Can’t Wait to be Healthy’: A briefing paper on evaluation for Leeds Childhood Obesity Prevention and Weight Management Strategy.

The rise in childhood obesity is a major public health challenge and a national priority for health action. Obesity is associated with many illnesses and is directly related to increased mortality and lower life expectancy. The Children’s Plan recognises child obesity as one of the most serious challenges for children and links it to a number of poor outcomes, physical, social and psychological (Department for Children, Schools and Families 2007). ‘Can’t wait to be healthy’- Leeds Childhood Obesity Prevention and Weight Management Strategy 2006-2016 is a comprehensive, city-wide strategy setting out actions to tackle the problem of childhood obesity for all children and young people 0-19 years. The strategy reviews the evidence around prevalence, causal factors and effective interventions. There is recognition of the complexity of the issue and the need for action on multiple levels and in different sectors, including health, education, environment and leisure services. The guiding principles are based on partnership working and local leadership, the active participation of parents, carers, children and young people, and the prioritisation of prevention and early intervention. ‘Can’t wait to be healthy’ was initiated by Leeds Primary Care Trust (PCT) and Children Leeds and its implementation is being overseen by a multi agency partnership. An initial action plan was agreed that gives an outline of proposed actions (2007-2010) grouped around strands of work. There are seven core objectives that are summarised in Box 1. A robust evaluation plan and reporting framework to measure progress and outcomes resulting from the strategy is required. This is supported by recent guidance for local areas indicating the importance of local evaluation and monitoring in tracking progress and informing commissioning (Cross Government Obesity Unit 2008a).The Centre for Health Promotion Research, Leeds Metropolitan University, was commissioned to work in collaboration with the Leeds Childhood Obesity Partnership to develop a strategic approach to evaluation. A series of workshops were held in Spring 2008 to enable stakeholders to engage with the planning process and to consider how evidence would be generated. The workshops used a ‘Theory of Change’ approach to develop understanding about how and why specific activities or combinations of activities work (Connell and Kubisch 1988). This resulted in a draft evaluation plan and recommendations for ongoing evaluation which are presented here. This briefing paper includes: • Summary of national guidance on indicators for childhood obesity • Evaluation planning process and approach • Theories of change and evaluation plans for each objective and for the overall strategy • Recommendations for evaluation of ‘Can’t wait to be healthy’ and priorities for data collectio

On the gap-opening criterion of migrating planets in protoplanetary disks

We perform two-dimensional hydrodynamical simulations to quantitatively explore the torque balance criterion for gap-opening (as formulated by Crida et al. 2006) in a variety of disks when considering a migrating planet. We find that even when the criterion is satisfied, there are instances when planets still do not open gaps. We stress that gap-opening is not only dependent on whether a planet has the ability to open a gap, but whether it can do so quickly enough. This can be expressed as an additional condition on the gap-opening timescale versus the crossing time, i.e. the time it takes the planet to cross the region which it is carving out. While this point has been briefly made in the previous literature, our results quantify it for a range of protoplanetary disk properties and planetary masses, demonstrating how crucial it is for gap-opening. This additional condition has important implications for the survival of planets formed by core accretion in low mass disks as well as giant planets or brown dwarfs formed by gravitational instability in massive disks. It is particularly important for planets with intermediate masses susceptible to Type III-like migration. For some observed transition disks or disks with gaps, we expect that estimates on the potential planet masses based on the torque balance gap-opening criterion alone may not be sufficient. With consideration of this additional timescale criterion theoretical studies may find a reduced planet survivability or that planets may migrate further inwards before opening a gap.Comment: Accepted by ApJ, 22 pages, 13 figures, 6 table

Trade-off Between Work and Correlations in Quantum Thermodynamics

Quantum thermodynamics and quantum information are two frameworks for employing quantum mechanical systems for practical tasks, exploiting genuine quantum features to obtain advantages with respect to classical implementations. While appearing disconnected at first, the main resources of these frameworks, work and correlations, have a complicated yet interesting relationship that we examine here. We review the role of correlations in quantum thermodynamics, with a particular focus on the conversion of work into correlations. We provide new insights into the fundamental work cost of correlations and the existence of optimally correlating unitaries, and discuss relevant open problems.Comment: 11 pages, 1 figure

Credit assignment in multiple goal embodied visuomotor behavior

The intrinsic complexity of the brain can lead one to set aside issues related to its relationships with the body, but the field of embodied cognition emphasizes that understanding brain function at the system level requires one to address the role of the brain-body interface. It has only recently been appreciated that this interface performs huge amounts of computation that does not have to be repeated by the brain, and thus affords the brain great simplifications in its representations. In effect the brain’s abstract states can refer to coded representations of the world created by the body. But even if the brain can communicate with the world through abstractions, the severe speed limitations in its neural circuitry mean that vast amounts of indexing must be performed during development so that appropriate behavioral responses can be rapidly accessed. One way this could happen would be if the brain used a decomposition whereby behavioral primitives could be quickly accessed and combined. This realization motivates our study of independent sensorimotor task solvers, which we call modules, in directing behavior. The issue we focus on herein is how an embodied agent can learn to calibrate such individual visuomotor modules while pursuing multiple goals. The biologically plausible standard for module programming is that of reinforcement given during exploration of the environment. However this formulation contains a substantial issue when sensorimotor modules are used in combination: The credit for their overall performance must be divided amongst them. We show that this problem can be solved and that diverse task combinations are beneficial in learning and not a complication, as usually assumed. Our simulations show that fast algorithms are available that allot credit correctly and are insensitive to measurement noise

Metric based up-scaling

We consider divergence form elliptic operators in dimension $n\geq 2$ with $L^\infty$ coefficients. Although solutions of these operators are only H\"{o}lder continuous, we show that they are differentiable ($C^{1,\alpha}$) with respect to harmonic coordinates. It follows that numerical homogenization can be extended to situations where the medium has no ergodicity at small scales and is characterized by a continuum of scales by transferring a new metric in addition to traditional averaged (homogenized) quantities from subgrid scales into computational scales and error bounds can be given. This numerical homogenization method can also be used as a compression tool for differential operators.Comment: Final version. Accepted for publication in Communications on Pure and Applied Mathematics. Presented at CIMMS (March 2005), Socams 2005 (April), Oberwolfach, MPI Leipzig (May 2005), CIRM (July 2005). Higher resolution figures are available at http://www.acm.caltech.edu/~owhadi