672 research outputs found
Sound modes in holographic hydrodynamics for charged AdS black hole
No full textAbstractIn the previous paper we studied the transport coefficients of quark–gluon plasma in finite temperature and finite density in vector and tensor modes. In this paper, we extend it to the scalar modes. We work out the decoupling problem and hydrodynamic analysis for the sound mode in charged AdS black hole and calculate the sound velocity, the charge susceptibility and the electrical conductivity. We find that Einstein relation among the conductivity, the diffusion constant and the susceptibility holds exactly
Bose–Einstein condensation in the Rindler space
No full textAbstractBased on the Unruh effect, we calculate the critical acceleration of the Bose–Einstein condensation in a free complex scalar field at finite density in the Rindler space. Our model corresponds to an ideal gas performing constantly accelerating motion in a Minkowski space–time at zero-temperature, where the gas is composed of the complex scalar particles and it can be thought to be in a thermal-bath with the Unruh temperature. In the accelerating frame, the model will be in the Bose–Einstein condensation state at low acceleration; on the other hand, there will be no condensation at high acceleration by the thermal excitation brought into by the Unruh effect. Our critical acceleration is the one at which the Bose–Einstein condensation begins to appear in the accelerating frame when we decrease the acceleration gradually. To carry out the calculation, we assume that the critical acceleration is much larger than the mass of the particle
Evaluation of Post-license Advanced Driver Training in Italy
No full textAbstractPost-license advanced driver training addresses different categories of road users such as: novice drivers, professional drivers, company employers and recidivists. These training courses can be carried out on-track or on the road. On-track courses allow participants to gain knowledge on driving physics and experience limits in a safe road environment. On-road courses are more focused on hazard perception and situation awareness.Although extensive research has been done in this field, knowledge of the effects of these courses on road accident risk remains unclear. Previous evaluation of on-track courses did not always show a positive effect on crash rate. For example, post-license training focused on mastery of driving skills can lead to an increase of accident risk, especially on young males.However, research identified several factors that may enhance the effectiveness of driving training. In Europe a new framework for driver education and training has been proposed based on a safe driver hierarchical model (the GADGET model) and the development of a strategy for continuous learning.According to this framework, an evaluation study of on-track post-license advanced driver training has been undertaken in Italy with the main goal of assessing the safety effects of these courses and identifying training aspects to be improved. Besides crash rate, the study aims at assessing also driver behavior, knowledge of risks, self-evaluation and training quality.This paper presents the results of the possible effects of advanced driver training on driving behavior, considering in particular the number and type of violations. For each driver, data on age, gender and driving violations history were extracted from the platform and the national violations database.Three cases were addressed through a before-after analysis with control group. Case 1 considers all drivers who attended an ADT course. Case 2 aimed at understanding the effects of the courses on a specific target group: the traffic violators. Case 3 is similar to Case 2, however the control group was selected in a way that drivers characteristics and the violation rate was similar to the violation rate of the treatment group in the before period.The significance of the differences highlighted was assessed through appropriate statistical tests (i.e. paired t-test and the Wilcoxon signed-rank test).The study showed in general a higher propensity to commit traffic violations after attending an ADT course. These results are in contrast to what expected and show the necessity to diversify the training classes according to the different needs of participants
Coincidence sets in quasilinear problems of logistic type (Nonlinear Evolution Equations and Mathematical Modeling)
No full textA methodology to assess pedestrian crossing safety
No full textPurpose: The safety level of a pedestrian crossing is affected by infrastructure characteristics and vehicular and pedestrian traffic level. This paper presents a methodology that allows assessing the safety level of a pedestrian crossing, regulated or not by traffic light, in an urban area according to the features of the crossing. Methods: A hierarchical structure representing factors influencing crossing safety has been developed and the relative contributions of each factor were calculated using AHP method. A composite index for crossing safety and specific indexes for main aspects included in the assessment have been developed. Results: Main assessment aspects are: Spatial and Temporal Design, Day-time and Night-time Visibility and Accessibility. Night-time Visibility resulted to have the higher weight (about 41%). Conclusion: Developed indexes allow ranking of pedestrian crossings and assigning intervention priorities, highlighting the aspects which are to be enhanced. The methodology has been used for the evaluation of 215 pedestrian crossings in 17 European cities for the Pedestrian Crossing Assessment Project co-financed by FIA Foundation. © 2010 The Author(s)
Coincidence sets in quasilinear elliptic problems of monostable type
No full textAbstractThis paper concerns the formation of a coincidence set for the positive solution of the boundary value problem: −εΔpu=uq−1f(a(x)−u) in Ω with u=0 on ∂Ω, where ε is a positive parameter, Δpu=div(|∇u|p−2∇u), 1<q⩽p<∞, f(s)∼|s|θ−1s (s→0) for some θ>0 and a(x) is a positive smooth function satisfying Δpa=0 in Ω with infΩ|∇a|>0. It is proved in this paper that if 0<θ<1 the coincidence set Oε={x∈Ω:uε(x)=a(x)} has a positive measure for small ε and converges to Ω with order O(ε1/p) as ε→0. Moreover, it is also shown that if θ⩾1, then Oε is empty for any ε>0. The proofs rely on comparison theorems and the energy method for obtaining local comparison functions
Generalized Jacobian elliptic functions and their application to bifurcation problems associated with p-Laplacian
No full textAbstractThe Jacobian elliptic functions are generalized and applied to bifurcation problems associated with p-Laplacian. The values of bifurcation parameter and the corresponding solutions are represented in terms of common parameters, and a complete description of the bifurcation diagram and a closed form representation of the corresponding solutions are obtained. As a by-product of the representation, it turns out that a kind of solution is also a solution of an eigenvalue problem of p/2-Laplacian
Josephson junction formed in the wormhole space time from the analysis for the critical temperature of Bose-Einstein condensate
No full textIn this study, considering some gas in the Morris-Thorne traversable wormhole
space time, we analyze the critical temperature of the Bose-Einstein condensate
in the vicinity of its throat. As a result, we obtain the result that it is
zero. Then, from this result, we point out that an analogous state to the
Josephson junction is always formed at any temperatures in the vicinity of its
throat. This would be interesting as a gravitational phenomenology.Comment: 33 pages; v2: accepted version; v3: description improve
Kerr/CFT correspondence in a 4D extremal rotating regular black hole with a non-linear magnetic monopole
No full textWe carry out the Kerr/CFT correspondence in a four-dimensional extremal
rotating regular black hole with a non-linear magnetic monopole (NLMM). One
problem in this study would be whether our geometry can be a solution or not.
We search for the way making our rotating geometry into a solution based on the
fact that the Schwarzschild regular black hole geometry with a NLMM can be a
solution. However, in the attempt to extend the Schwarzschild case that we can
naturally consider, it turns out that it is impossible to construct a model in
which our geometry can be a exact solution. We manage this problem by making
use of the fact that our geometry can be a solution approximately in the whole
space-time except for the black hole's core region. As a next problem, it turns
out that the equation to obtain the horizon radii is given by a fifth-order
equation due to the regularization effect. We overcome this problem by treating
the regularization effect perturbatively. As a result, we can obtain the
near-horizon extremal Kerr (NHEK) geometry with the correction of the
regularization effect. Once obtaining the NHEK geometry, we can obtain the
central charge and the Frolov-Thorne temperature in the dual CFT. Using these,
we compute its entropy through the Cardy formula, which agrees with the one
computed from the Bekenstein-Hawking entropy.Comment: 23 pages; v5: accepted versio
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