Attracting Random Walks

This paper introduces the Attracting Random Walks model, which describes the dynamics of a system of particles on a graph with $n$ vertices. At each step, a single particle moves to an adjacent vertex (or stays at the current one) with probability proportional to the exponent of the number of other particles at a vertex. From an applied standpoint, the model captures the rich get richer phenomenon. We show that the Markov chain exhibits a phase transition in mixing time, as the parameter governing the attraction is varied. Namely, mixing time is $O(n\log n)$ when the temperature is sufficiently high and $\exp(\Omega(n))$ when temperature is sufficiently low. When $\mathcal{G}$ is the complete graph, the model is a projection of the Potts model, whose mixing properties and the critical temperature have been known previously. However, for any other graph our model is non-reversible and does not seem to admit a simple Gibbsian description of a stationary distribution. Notably, we demonstrate existence of the dynamic phase transition without decomposing the stationary distribution into phases.Comment: 32 pages, 7 figure

Many body exchange effects close to the s-wave Feshbach resonance in two-component Fermi systems: Is a triplet superfluid possible?

We suggest that the exchange fluctuations close to a Feshbach resonance in a two-component Fermi gas can result in an effective p-wave attractive interaction. On the BCS side of a Feshbach resonance, the magnitude of this effective interaction is comparable to the s-wave interaction, therefore leading to a possible spin-triplet superfluid in the range of temperatures of actual experiments. We also show that the particle-hole exchange fluctuations introduce an effective scattering length which does not diverge, as the standard mean-field one does. Finally, using the effective interaction quantities we are able to model the molecular binding energy on the BEC side of the resonance.Comment: 5 pages, 5 figures,revised text version. Replaced with published versio

A small satellite mission devoted to mid-low latitude earth observation

This paper aims at assessing the feasibility of a small mission devoted to observe the mid-low latitude regions. The satellite will be equipped with three optical sensors: a medium-high spatial resolution VIS-NIR multi-spectral sensor, allowing the surface monitoring and land-use and land-cover studies; a medium spatial-resolution 3-bands thermal (MIR-TIR) sensor allowing the surface temperature (LST, SST) estimate and hot-spots (fires, volcanic eruption, etc.) detection; a panchromatic VIS-NIR camera for night-time observation able to reveal artificial and natural lights. The selected orbit, called multi-sun-synchronous (MSS), represents an innovation with respect to the classical sun-synchronous orbit much suitable for observing tropical regions, allowing an enhanced revisit frequency. Further, such an orbit allows the observation of the same region of the Earth at different local-time. In this way, the diurnal cycle of surface temperatures can be reconstructed with a 2-hours local-time step. An analysis of the capability of the selected ground stations to acquire the data gathered by the remote sensing sensors has been carried out. Orbital perturbations have been taken into account and an estimate of the propellant required for ground track control has been performed in order to verify its compatibility with a small mission requirements

Finite size Berezinski-Kosterlitz-Thouless transition at grain boundaries in solid 4^4He and role of 3^3He impurities

We analyze the complex phenomenology of the Non-Classical Rotational Inertia (NCRI) observed at low temperature in solid $^4$He within the context of a two dimensional Berezinski-Kosterlitz-Thouless transition in a premelted $^4$He film at the grain boundaries. We show that both the temperature and $^3$He doping dependence of the NCRI fraction (NCRIF) can be ascribed to finite size effects induced by the finite grain size. We give an estimate of the average size of the grains which we argue to be limited by the isotopic $^3$He impurities and we provide a simple power-law relation between the NCRIF and the $^3$He concentration.Comment: Final version, as appearing on prin

Target Advertising Effects on Campaign Success

Nearly every company and organization advertises to increase awareness, reach sales goals, and build brand loyalty. However, due to the pervasive nature of advertising, reaching an audience has become more difficult and less successful. An increasing number of marketers are relying on detailed, targeted advertising to reach the most likely consumer of a particular brand, service or idea. First, past research and marketing information is analyzed and explained. Next, a study was conducted to determine how marketers utilize targeting methods and practices. Ten advertising professionals were asked open-ended questions regarding budget, direct marketing, technology and social media. The results showed that, while each account will use different methods to varying extents, targeted and direct advertising is vital to a successful campaign. As technology continues to develop and new targeting practices are made available, future research will determine the full extent of using specific strategies and tactics to reach the most promising consumer