Truthful mechanism design via correlated tree rounding

A powerful algorithmic technique for truthful mechanism design is the maximal-in-distributional-range (MIDR) paradigm. Unfortunately, many such algorithms use heavy algorithmic machinery, e.g., the ellipsoid method and (approximate) solution of convex programs. In this paper, we present a correlated rounding technique for designing mechanisms that are truthful in expectation. It is elementary and can be implemented quickly. The main property we rely on is that the domain offers fractional optimum solutions with a tree structure. In auctions based on the generalized assignment problem, each bidder has a publicly known knapsack constraint that captures the subsets of items that are of value to him. He has a private valuation for each item and strives to maximize the value of assigned items minus payment. For this domain we design a truthful 2-approximate MIDR mechanism for social welfare maximization. It avoids using the ellipsoid method or convex programming. In contrast to some previous work, our mechanism achieves exact truthfulness. In restricted-related scheduling with selfish machines, each job comes with a public weight, and it must be assigned to a machine from a public job-specific subset. Each machine has a private speed and strives to maximize payments minus workload of jobs assigned to it. Here we design a mechanism for makespan minimization. This is a single-parameter domain, but the approximation status of the optimization problem is similar to unrelated machine scheduling: The best known algorithm obtains a (non-truthful) 2-approximation for unrelated machines, and there is 1.5-hardness. Our mechanism matches this bound with a truthful 2-approximation.     

Dynamics of a hybrid vibro-impact oscillator: canonical formalism

Nonlinear Dynamics - Hybrid vibro-impact (HVI) oscillations is a strongly nonlinear dynamical regime that involves both linear oscillations and collisions under periodic, impulsive, or stochastic...     

Electron promotion effects in small impact parameter S+q+ rare gas collisions

Approach to equilibrium charge distribution in single, small impact parameter collisions of S projectiles with rare gases has been observed. Average charges generally agree with the dynamic screening model, but in the S + Xe system they are raised by promotion effects.     

A quantitative investigation of the pomeron

A comparative investigation of various pomeron models is carried out through the study of their predicted values of _tot,B, and in high energypp and scattering. Our results strongly support a picture of the pomeron in which we have both moderate blackening and expansion of the amplitude in impact parameter space as a function of energy in the ISR-SSC domain. Our analysis shows the data is compatible with a hybrid eikonal model which combines the hard Lipatovlike QCD pomeron with the old fashioned soft pomeron and Regge terms. We show that the additive quark model, at least in the naive form, is not compatible with the data.Work supported in part by Israel Academy of Sciences and Humanities     

Ultrasound-assisted dispersion of SrFe<Subscript>12</Subscript>O<Subscript>19</Subscript> nanoparticles in organic solvents and the use of the dispersion as magnetic cosmetics

A new method of dispersing the aggregated strontium hexaferrite (SrFe₁₂O₁₉) magnetic nanoparticles in organic solvents such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol (PG), and glycerol, by an ultrasonic bath is reported herein. The particles size of SrFe₁₂O₁₉ after treatment with the PGMEA is in the range 70–100 nm. The structure of dispersed SrFe₁₂O₁₉ was characterized using transmission electron microscopy (TEM), high resolution scanning electron microscopy (HR SEM) and thermo gravimetric analysis (TGA). This dispersed material was used for the preparation of a topical magnetic cosmetic product as follows: The dispersion of SrFe₁₂O₁₉ in PG was mixed with “Dermud-Ahava Body Cream”, an ‘oil in water’ emulsion of a Dead Sea mineral cosmetic, “AHAVA”, and the magnetic properties of the created composite were determined. The ferrimagnetic behavior of the composite has been demonstrated as being very similar to the behavior of strontium hexaferrite itself.     

Absorptive corrections and pion-exchange contributions to inclusive reactions

Pion-exchange contributions to inclusive reactions in the fragmentation domain are discussed and the importance of introducing absorptive corrections is stressed. An explicit model which incorporates the absorptive two-body correction is suggested and its experimental implications are examined.     

A modified Balitsky–Kovchegov equation

We propose a modified version of the Balitsky–Kovchegov (BK) evolution equation, which includes the main NLO corrections. We use the result that the main NLO corrections to the BFKL kernel are the LO DGLAP corrections. We present a numerical solution of the modified non-linear equation, and compare with the solution of the unmodified BK equation. We show that the saturation momentum has a sharp increase in the LHC energy range. Our numerical solution indicates that the influence of the preasymptotic corrections, related to the full anomalous dimensions of the DGLAP equation, are rather large. These corrections moderate the energy behavior of the amplitude, as well as the value of the saturation scale. All our calculations are made with a fixed value of _S.     

Charge transfer in 1.4 MeV/u Ni q+→Kr collisions,q=16−22

Cross sections for the electron transfer from neutral Kr atoms to highly charged Ni ^q+ projectiles were measured at 1.4 MeV/u. Estimates on the contributions of single and double capture into the Ni-L shell and into excited states are extracted from measured cross sections for the Ni-L x-ray emission for incoming projectileL vacancies (q≧19). The role of metastable states produced in the capture process is analysed. We find that most of the capture directly populates the Ni-L shell, and the capture into excited states seems to be dominated by two-electron capture. The electrons involved in double transfer processes seem to be strongly correlated. An increase in the low-probability non-correlated double transfer with increasing number of incomingL-vacancies is indicated by the data.