Elliptic flow of gluon matter in ultrarelativistic heavy-ion collisions

Employing a perturbative QCD based parton cascade we calculate the elliptic flow $v_2$ and its transverse momentum dependence $v_2(p_T)$ for the gluon matter created in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. To make comparisons with the experimental data at the BNL Relativistic Heavy Ion Collider (RHIC), parton-hadron duality is assumed. We find that whereas the integrated $v_2$ matches the experimental data, the gluon (or pion) $v_2(p_T)$ is about 20-50% smaller than the experimental data. Hadronization via gluon fragmentation and quark recombination seems to be the key to explaining the necessary jump of $v_2(p_T)$ from the partonic to the hadronic phase. We also show that the elliptic flow values moderately depend on the chosen freezeout condition, which will thus constrain the shear viscosity to the entropy density ratio of the quark gluon plasma created at RHIC.Comment: 20 pages, 7 figures, minor corrections, published versio

Blind channel identification based on second-order statistics: a frequency-domain approach

In this communication, necessary and sufficient conditions are presented for the unique blind identification of possibly nonminimum phase channels driven by cyclostationary processes. Using a frequency domain formulation, it is first shown that a channel can be identified by the second-order statistics of the observation if and only if the channel transfer function does not have special uniformly spaced zeros. This condition leads to several necessary and sufficient conditions on the observation spectra and the channel impulse response. Based on the frequency-domain formulation, a new identification algorithm is proposed

Essays in microeconomic theory

The thesis first provides an axiomatic characterization of the probability-weighted minimal norm solution for Bayesian social choice problems with reference points. Chapter 2 provides a characterization of feasibility conditions for general social choice problems. The examples include voting, auctions with externalities, package auctions and exchanges with complementary objects. Chapter 3 examines the existence of ex post efficient and monotone solutions for a two-person bargaining problem. Chapters 4 and 5 investigate two specific problems of designing trading mechanisms with monetary transfers to achieve certain welfare objectives

Symmetric reduced form voting

We study a model of voting with two alternatives in a symmetric environment. We characterize the interim allocation probabilities that can be implemented by a symmetric voting rule. We show that every such interim allocation probabilities can be implemented as a convex combination of two families of deterministic voting rules: qualified majority and qualified anti-majority. We also provide analogous results by requiring implementation by a symmetric monotone (strategy-proof) voting rule and by a symmetric unanimous voting rule. We apply our results to show that an ex-ante Rawlsian rule is a convex combination of a pair of qualified majority rules

Revisiting the alerting effect of light: A systematic review

Light plays an essential role in maintaining alertness levels. Like other non-image-forming responses, the alerting effect of light is influenced by its spectral wavelength, duration and intensity. Alertness levels are also dependent on circadian rhythm (Process C) and homeostatic sleep pressure (Process S), consistent with the classic two-process model of sleep regulation. Over the last decade, there has been increasing recognition of an additional process (referred to as the third process) in sleep regulation. This third process seems to receive sensory inputs from body systems such as digestion, and is usually synchronised with Process C and Process S. Previous studies on the alerting effect of light have been mostly conducted in laboratories. Although these studies are helpful in delineating the impact of Process C and Process S, their ability to assist in understanding the third process is limited. This systematic review investigated the factors that influence the alerting effect of light by examining randomized controlled trials and randomized or counterbalanced crossover studies. Factors that influence light’s alerting effect were examined with reference to the three-process model. The post-illuminance alerting effect was examined separately due to its potential to offer flexible workplace-based light interventions to increase or maintain employees’ alertness

Chinese pension fund investment efficiency - evidence from CNCSSF stock holdings

China’s pension system is facing a large gap of more than one trillion RMB. The investment efficiency of the social security fund therefore receives widespread attention in academic circles. We collected data of stocks held by the Chinese National Council for Social Security Fund (CNCSSF) from 2004 to 2012 to research the stocks’ investment efficiency, distinguishing between direct investment by the CNCSSF and entrusted investment by fund companies. The results indicate that both components of the Chinese Social Security Fund investment have efficiency drawbacks. Direct investment by the CNCSSF does not obtain excess returns, while entrusted investment reaches an annual excess return of 4.32 percent because more private information is available to fund companies than to the CNCSSF during asset allocation. Further analyses of this paper find, however, that the Chinese Social Security Fund has a significant market-stabilizing effect, which is almost three times stronger than the market-stabilizing effect of entrusted investment. In general, entrusted investment performs better than direct investment with regard to investment efficiency, while direct investment performs better in terms of market stabilization

Reconsideration on the elastic damage/degradation theory for the modeling of microcrack closure-reopening (MCR) effects

AbstractDespite the substantial and noteworthy contributions, the modeling of damage induced anisotropy remains an unsolved issue, especially when the microcrack closure-reopening (MCR) effects are accounted for. Theoretically speaking, the most challenging problem might be the lack of energy conservation for all the existing models employing the spectral decomposition of the stress or strain tensor and the associated positive/negative projection operators (Carol and Willam, 1996). In this paper this crucial problem is solved by introducing a new definition of thermodynamically consistent projection operators into the classical elastic damage/degradation model. The orthogonality between the rates of the new projection operators and the stress (or strain) automatically guarantees the fulfillment of energy conservation under any arbitrary (proportional or non-proportional) load history. Moreover, with this extra orthogonal property the thermodynamically consistent projection operators can be exclusively determined in a unique form. The above advantages lend to their promising use in the modeling of damage induced anisotropy and MCR effects simultaneously. With the aid of the thermodynamically consistent projection operators, the existing elastic damage/degradation models can be reformulated so that the energy conservation is restored only with minor modifications. As a prototype example, a stress-based elastic damage/degradation model with multiple loading surfaces is developed analogously to the classical multisurface plasticity model. Finally, a simple closed-loop load path accompanied with rotation of principal stress directions is constructed to verify its thermodynamically consistency

Analytical and Monte Carlo results for the surface-brightness diameter relationship in supernova remnants

The surface brightness diameter relationship for supernovae remnants (SNRs) is explained by adopting a model of direct conversion of the flux of kinetic energy into synchrotron luminosity. Two laws of motion are adopted, a power law model for the radius-time relationship, and a model which uses the thin layer approximation. The fluctuations on the log-log surface diameter relationship are modeled by a Monte Carlo simulation. In this model a new probability density function for the density as function of the galactic height is introduced.Comment: 24 pages 8 figure

Submillimeter/millimeter observations of the high-mass star forming region IRAS 22506+5944

The mapping observations of CO $J=2-1$, CO $J=3-2$, $^{13}$CO $J=2-1$ and $^{13}$CO $J=3-2$ lines in the direction of IRAS 22506+5944 have been made. The results show that the cores in the $J=2-1$ transition lines have a similar morphology to those in the $J=3-2$ transition lines. Bipolar molecular outflows are verified. The prior IRAS 22506+5944 observations indicated that two IRAS sources and three H$_{2}$O masers were located close to the peak position of the core. One of the IRAS sources may be the driving source of the outflows. In addition, the H$_{2}$O masers may occur in relatively warm environments. The parameters of the dense core and outflow, obtained by the LTE method, indicate that IRAS 22506+5944 is a high-mass star formation region.Comment: 8 pages, 4 figures, published in RA