A Model for the Color Glass Condensate Versus Jet Quenching

A model for the Color Glass Condensate as opposed to jet quenching is proposed for the explanation of the presently available RHIC data. Good fits to these data are presented. A clear way to distinguish between the two possible explanations is also given.Comment: 3 pages, 1 figur

Nonperiodic delay mechanism in time-dependent chaotic scattering

We study the occurence of delay mechanisms other than periodic orbits in systems with time dependent potentials that exhibit chaotic scattering. By using as model system two harmonically oscillating disks on a plane, we have found the existence of a mechanism not related to the periodic orbits of the system, that delays trajectories in the scattering region. This mechanism creates a fractal-like structure in the scattering functions and can possibly occur in several time-dependent scattering systems.Comment: 12 pages, 9 figure

Quantum versus Classical Dynamics in a driven barrier: the role of kinematic effects

We study the dynamics of the classical and quantum mechanical scattering of a wave packet from an oscillating barrier. Our main focus is on the dependence of the transmission coefficient on the initial energy of the wave packet for a wide range of oscillation frequencies. The behavior of the quantum transmission coefficient is affected by tunneling phenomena, resonances and kinematic effects emanating from the time dependence of the potential. We show that when kinematic effects dominate (mainly in intermediate frequencies), classical mechanics provides very good approximation of quantum results. Moreover, in the frequency region of optimal agreement between classical and quantum transmission coefficient, the transmission threshold, i.e. the energy above which the transmission coefficient becomes larger than a specific small threshold value, is found to exhibit a minimum. We also consider the form of the transmitted wave packet and we find that for low values of the frequency the incoming classical and quantum wave packet can be split into a train of well separated coherent pulses, a phenomenon which can admit purely classical kinematic interpretation

Hyperacceleration in a stochastic Fermi-Ulam model

Fermi acceleration in a Fermi-Ulam model, consisting of an ensemble of particles bouncing between two, infinitely heavy, stochastically oscillating hard walls, is investigated. It is shown that the widely used approximation, neglecting the displacement of the walls (static wall approximation), leads to a systematic underestimation of particle acceleration. An improved approximative map is introduced, which takes into account the effect of the wall displacement, and in addition allows the analytical estimation of the long term behavior of the particle mean velocity as well as the corresponding probability distribution, in complete agreement with the numerical results of the exact dynamics. This effect accounting for the increased particle acceleration -Fermi hyperacceleration- is also present in higher dimensional systems, such as the driven Lorentz gas.Comment: 4 pages, 3 figures. To be published in Phys. Rev. Let

A nonlinear classical model for the decay widths of Isoscalar Giant Monopole Resonances

The decay of the Isoscalar Giant Monopole Resonance (ISGMR) in nuclei is studied by means of a nonlinear classical model consisting of several noninteracting nucleons (particles) moving in a potential well with an oscillating nuclear surface (wall). The motion of the nuclear surface is described by means of a collective variable which appears explicitly in the Hamiltonian as an additional degree of freedom. The total energy of the system is therefore conserved. Although the particles do not directly interact with each other, their motions are indirectly coupled by means of their interaction with the moving nuclear surface. We consider as free parameters in this model the degree of collectivity and the fraction of nucleons that participate to the decay of the collective excitation. Specifically, we have calculated the decay width of the ISGMR in the spherical nuclei $^{208}\rm{Pb}$, $^{144}\rm{Sm}$, $^{116}\rm{Sn}$ and $^{90}\rm{Zr}$. Despite its simplicity and its purely classical nature, the model reproduces the trend of the experimental data which show that with increasing mass number the decay width decreases. Moreover the experimental results (with the exception of $^{90}\rm{Zr}$) can be well fitted using appropriate values for the free parameters mentioned above. It is also found that these values allow for a good description of the experimentally measured $^{112}\rm{Sn}$ and $^{124}\rm{Sn}$ decay widths. In addition, we give a prediction for the decay width of the exotic isotope $^{132}Sn$ for which there is experimental interest. The agreement of our results with the corresponding experimental data for medium-heavy nuclei is dictated by the underlying classical mechanics i.e. the behaviour of the maximum Lyapunov exponent as a function of the system size

Human-centered 2D/3D Video Content Analysis and Description

In this paper, we propose a way of using the AudioVisual Description Profile (AVDP) of the MPEG-7 standard for stereo video and multichannel audio content description. Our aim is to provide means of using AVDP in such a way, that 3D video and audio content can be correctly and consistently described. Since AVDP semantics do not include ways for dealing with 3D audiovisual content, a new semantic framework within AVDP is proposed and examples of using AVDP to describe the results of analysis algorithms on stereo video and multichannel audio content are presented

Self-Reported Hearing Impairment and Incident Frailty in English Community-Dwelling Older Adults: A 4-Year Follow-Up Study

OBJECTIVES: To examine the association between hearing impairment and incident frailty in older adults. DESIGN: Cross-sectional and longitudinal analyses with 4-year follow-up using data from the English Longitudinal Study of Ageing. SETTING: Community. PARTICIPANTS: Community-dwelling individuals aged 60 and older with data on hearing and frailty status (N = 2,836). MEASUREMENTS: Hearing impairment was defined as poor self-reported hearing. Having none of the five Fried frailty phenotype components (slow walking, weak grip, self-reported exhaustion, weight loss and low physical activity) was defined as not frail, having one or two as prefrail, and having three or more as frail. Participants who were not frail at baseline were followed for incident prefrailty and frailty. Participants who were prefrail at baseline were followed for incident frailty. RESULTS: One thousand three hundred ninety six (49%) participants were not frail, 1,178 (42%) were prefrail, and 262 (9%) were frail according to the Fried phenotype. At follow-up, there were 367 new cases of prefrailty and frailty among those who were not frail at baseline (n = 1,396) and 133 new cases of frailty among those who were prefrail at baseline (n = 1,178). Cross-sectional analysis showed an association between hearing impairment and frailty (age- and sex-adjusted odds ratio (OR) = 1.66, 95% confidence interval (CI) = 1.37–2.01), which remained after further adjustments for wealth, education, cardiovascular disease, cognition, and depression. In longitudinal analyses, nonfrail participants with hearing impairment were at greater risk of becoming prefrail and frail at follow-up (OR = 1.43, 95% CI = 1.05–1.95), but the association was attenuated after further adjustment. Prefrail participants with hearing impairment had a greater risk of becoming frail at follow-up (OR = 1.64, 95% CI = 1.07–2.51) even after further adjustment. CONCLUSION: Hearing impairment in prefrail older adults was associated with greater risk of becoming frail, independent of covariates, suggesting that hearing impairment may hasten the progression of frailty