The Glasma and the Hard Ridge

Correlation measurements indicate that excess two particle correlations extend over causally disconnected rapidity ranges. Although, this enhancement is broad in relative rapidity $\eta=\eta_1 - \eta_2$, it is focused in a narrow region in relative azimuthal angle $\phi=\phi_1 - \phi_2$. The resulting structure looks like a ridge centered at $\eta = \phi=0$. Similar ridge structures are observed in correlations of particles associated with a jet trigger (the hard ridge) and in correlations without a trigger (the soft ridge). The long range rapidity behavior requires that the correlation originates in the earliest stage of the collision, and probes properties of the production mechanism. Glasma initial conditions as predicted by the theory of Color Glass Condensate and provide a and early stage correlation that naturally extends far in rapidity. We have previously shown that the soft ridge is a consequence of particles forming from an initial Glasma phase that experience a later stage transverse flow. We extend this work to study the ridge dependence on the $p_t$ of the correlated pairs. We then determine the soft contribution to the hard ridge.Comment: Proceeding of the APS meeting of the Division of Particles and Fields 2009, Detroit, Mi. Also see arXiv:0910.359

Flow Fluctuations from Early-Time Correlations in Nuclear Collisions

We propose that flow fluctuations have the same origin as transverse momentum fluctuations. The common source of these fluctuations is the spatially inhomogeneous initial state that drives hydrodynamic flow. Longitudinal correlations from an early Glasma stage followed by hydrodynamic flow quantitatively account for many features of multiplicity and $p_t$ fluctuation data. We develop a framework for studying flow and its fluctuations in this picture. We then compute elliptic and triangular flow fluctuations, and study their connections to the ridge

Long Range Correlations and the Soft Ridge in Relativistic Nuclear Collisions

Relativistic Heavy Ion Collider experiments exhibit correlations peaked in relative azimuthal angle and extended in rapidity. Called the ridge, this peak occurs both with and without a jet trigger. We argue that the untriggered ridge arises when particles formed by flux tubes in an early glasma stage later manifest transverse flow. Combining a blast wave model of flow fixed by single-particle spectra with a simple description of the glasma, we find excellent agreement with current data.Comment: revised text, results unchange

The APM cluster-galaxy cross-correlation function : Constraints on Omega and galaxy bias

(abridged) We estimate the cluster-galaxy cross-correlation function (Xi_cg), from the APM galaxy and galaxy cluster surveys, both in real space from the inversion of projected statistics and in redshift space using the galaxy and cluster redshift samples. The amplitude of Xi_cg is found to be almost independent of cluster richness. At large separations, r >~5 h^-1 Mpc, Xi_cg has a similar shape to the galaxy-galaxy and cluster-cluster autocorrelation functions. Xi_cg in redshift space can be related to the real space Xi_cg by convolution with an appropriate velocity field model. Here we apply a spherical collapse model, which we have tested against N-body simulations, finding that it provides a surprisingly accurate description of the averaged infall velocity of matter into galaxy clusters. We use this model to estimate beta (Omega^{0.6}/b) and find that it tends to overestimate the true result in simulations by only ~10-30%. Application to the APM results yields beta=0.43 with beta < 0.87 at 95% confidence. We also compare the APM Xi_cg and galaxy autocorrelations to results from popular cosmological models and derive two independent estimates of the galaxy biasing expected as a function of scale. Both low and critical density CDM models require anti-biasing by a factor ~2 on scales r <~ 2 h^-1Mpc and an MDM model is consistent with a constant biasing factor on all scales. We use the velocity fields predicted from the different models to distort the APM real space cross-correlation function. Comparison with the APM redshift space Xi_cg yields an estimate of the value of Omega^0.6 needed in each model. Only the low Omega model is fully consistent with observations, with MDM marginally excluded at the ~2 sigma level.Comment: Latex (mn.sty), 17 pages, 16 ps figs, submitted to MNRA

The Power Spectrum of Rich Clusters of Galaxies on Large Spatial Scales

We present an analysis of the redshift-space power spectrum, $P(k)$, of rich clusters of galaxies based on an automated cluster catalogue selected from the APM Galaxy Survey. We find that $P(k)$ can be approximated by a power law, P(k)\proptok^{n}, with $n\approx-1.6$ over the wavenumber range 0.04\hr. Over this range of wavenumbers, the APM cluster power spectrum has the same shape as the power spectra measured for optical and IRAS galaxies. This is consistent with a simple linear bias model in which different tracers have the same power spectrum as that of the mass distribution but shifted in amplitude by a constant biasing factor. On larger scales, the power spectrum of APM clusters flattens and appears to turn over on a scale k \sim 0.03\hmpcrev. We compare the power spectra estimated from simulated APM cluster catalogues to those estimated directly from cubical N-body simulation volumes and find that the APM cluster survey should give reliable estimates of the true power spectrum at wavenumbers k \simgt 0.02\hmpcrev. These results suggest that the observed turn-over in the power spectrum may be a real feature of the cluster distribution and that we have detected the transition to a near scale-invariant power spectrum implied by observations of anisotropies in the cosmic microwave background radiation. The scale of the turn-over in the cluster power spectrum is in good agreement with the scale of the turn-over observed in the power spectrum of APM galaxies.Comment: 9 pages, 7 ps figures, two style files, submitted to MNRAS. Un-xxx-ed version available at http://www-astro.physics.ox.ac.uk/research/preprints/aug97/cluspaper.ps.g

HIV/AIDS, growth and poverty in KwaZulu-Natal and South Africa: Integrating firm-level surveys with demographic and economywide modeling

"This paper estimates the economic impact of HIV/AIDS on KwaZulu-Natal (KZN) and the rest of South Africa (RSA). We extend previous studies by employing an integrated analytical framework that combines the following: firm-level surveys of workers' HIV prevalence by sector and occupation; a demographic model that produces both population and workforce projections; and a regionalized economywide model linked to a survey-based micro-simulation module. This framework permits a full macro-microeconomic assessment. The results indicate that HIV/AIDS greatly reduces annual economic growth, mainly by lowering the long-term rate of technical change. However, the impacts on income poverty are small, and inequality is reduced by HIV/AIDS. This is because high unemployment among low-income households minimizes the economic costs of increased mortality. In contrast, slower economic growth hurts higher-income households despite the lower prevalence of HIV among these households. We conclude that the increase in economic growth achieved through addressing HIV/AIDS is sufficient to offset the population pressure this move will place on income poverty. Moreover, incentives to mitigate HIV/AIDS lie not only with poorer infected households, but also with uninfected higher-income households. Our findings reveal that HIV/AIDS will place a substantial burden on future economic development in KZN and RSA, confirming the need for policies to curb the economic costs of this pandemic." from authors' abstractHIV/AIDS, Growth, Poverty, Development strategies, KwaZulu-Natal,

Higher Order Statistics from the Apm Galaxy Survey

We apply a new statistics, the factorial moment correlators, to density maps obtained from the APM survey. The resulting correlators are all proportional to the two point correlation function, substantially amplified, with an amplification nearly exponential with the total rank of the correlators. This confirms the validity of the hierarchical clustering assumption on the dynamic range examined, corresponding to 0.5 \hmpc - 50 \hmpc in three dimensional space. The Kirkwood superposition with loop terms is strongly rejected. The structure coefficients of the hierarchy are also fitted. The high quality of the APM catalog enabled us to disentangle the various contributions from the power spectrum, small scale nonlinear clustering, and combinatorial effects, all of which affect the amplification of the correlators. These effects should appear in correlations of clusters in a similar fashion.Comment: 30 pages text, 3 pages tables, 5 figures, uuencoded tarred postscrip

The APM Galaxy Survey:- V. Catalogues of Galaxy Clusters

We describe the construction of catalogues of galaxy clusters from the APM Galaxy survey using an automated algorithm based on Abell-like selection criteria. We investigate the effects of varying several parameters in our selection algorithm, including the magnitude range, and radius from the cluster centre used to estimate the cluster richnesses. We quantify the accuracy of the photometric distance estimates by comparing with measured redshifts, and we investigate the stability and completeness of the resulting catalogues. We find that the angular correlation functions for different cluster catalogues are in good agreement with one another, and are also consistent with the observed amplitude of the spatial correlation function of rich clusters.Comment: 14 pages, PostScript, including 15 figures, submitted to MNRAS. Also available from ftp://ftp-astro.physics.ox.ac.uk/pub/gbd/papers/apm5.ps.g

South Africa's private sector investment in training and its erosion as a result of HIV and AIDS

South Africa’s economic prospects depend on the productivity of its labour, and productivity can only be maximised when the labour force possess the appropriate skills. Business is playing its part by offering training opportunities to employees. Collectively, they are spending more than the government’s mandated level on training. However, the HIV and AIDS epidemic is eroding this investment in southern Africa where the HIV epidemic is at its worst. While there has been empirical work that provides estimates on the cost of HIV and AIDS to business, there is very little data on the actual amounts large companies spend on training, and how much of this investment is eroded as a result of HIV and AIDS deaths. Using an estimate of the HIV and AIDS death rate in the private sector and survey data which identifies training expenditure by sector, the authors estimate the extent to which HIV and AIDS has potentially eroded this investment. The loss for all sectors was estimated at almost R10 million (R9,871,732) during the study year, which equates to USD1,183,661 per annum. This amount represented on average 0.73 per cent of the actual investment in training. The real costs of HIV and AIDS on business, which includes absenteeism, declining productivity and other costs are difficult to quantify, but they are likely to significantly exceed this lost training investment as a result of increasing morbidity and mortality rates due to HIV. It is therefore in a company’s best interest to: (1) ensure that a sound HIV and AIDS policy is in place; (2) invest in effective prevention programmes; and (3) provide the appropriate ARV treatment to infected employees if this treatment is not easily accessible through the public health sector

What Is Hiding in the Bushes - Ebay\u27s Effect on Holdout Behavior in Patent Thickets

Importantly, at least a few relevant patent holders are inevitably left out of an industry organization\u27s collection of patents. These left-out patent holders, known as holdouts, can undermine the collective arrangement with demand letters and infringement suits.[...] The first part of this Note explains why holdouts exist in the first place, given the benefits of joining an organization of collected patents. In the second part of this Note, I explore the lack of legal protections against holdout demands offered by pre-eBay patent law. The third part of this Note introduces the eBay decision as revolutionary addition to list of legal protections against holdouts. To conclude, I speculate on the effects of eBay in areas of technology currently covered by patent thickets