L^p estimates for Riesz transforms on forms in the Poincare space H^n

Using hyperbolic form convolution with doubly isometry-invariant kernels, the explicit expression of the inverse of the de Rham laplacian acting on m-forms in the Poincar\'{e} space is found. Also, by means of some estimates for hyperbolic singular integrals, we obtain L^p-estimates for the Riesz transforms passing from the Laplacian to other covariant derivatives, in a range of p depending on m,n. Finally, using these, it is shown that the Laplacian defines topological isomorphisms in the scale of form Sobolev spaces, for m different from n/2,(n+1)/2,(n-1)/2.Comment: To appear in Indiana Univ. Math.

Talk 1: Convolutional neural networks against the curse of dimensionality

Convolutional Neural Networks are a powerful class of non-linear representations that have shown through numerous supervised learning tasks their ability to extract rich information from images, speech and text, with excellent statistical generalization. These are examples of truly high-dimensional signals, in which classical statistical models suffer from the curse of dimensionality, referring to their inability to generalize well unless provided with exponentially large amounts of training data. In this talk we will start by studying statistical models defined from wavelet scattering networks, a class of CNNs where the convolutional filter banks are given by complex, multi-resolution wavelet families. The reasons for such success lie on their ability to preserve discriminative information while being stable with respect to high-dimensional deformations, providing a framework that partially extends to trained CNNs. We will give conditions under which signals can be recovered from their scattering coefficients, and will discuss a family of Gibbs processes defined by CNN sufficient statistics, from which one can sample image and auditory textures. Although the scattering recovery is non-convex and corresponds to a generalized phase recovery problem, gradient descent algorithms show good empirical performance and enjoy weak convergence properties. We will discuss connections with non-linear compressed sensing, applications to texture synthesis, inverse problems such as super-resolution, as well as an application to sentence modeling, where convolutions are generalized using associative trees to generate robust sentence representations

Di-jet measurements in heavy-ion collisions at STAR

Jets are produced from hard scatterings in the early stages of heavy-ion collisions. It is expected that these high-$p_T$ partons travel through the hot and dense medium before fragmenting. Therefore they are expected to suffer energy loss in the QGP via gluon radiation and elastic collisions along their path. Measurements of fully reconstructed jets help understand the effect of the energy loss on the jet structure and energy profile. A data-driven characterization of the background in Au+Au is needed in order to compare the results to p+p. The full azimuthal coverage of STAR Time Projection Chamber and Electromagnetic Calorimeter allows measurements of fully reconstructed di-jets, defined by jets that match the online trigger and recoil jets on the away side. A tight selection of the trigger jets allows for a selection of those coming from the surface. Hence, the population of jets on the recoil side is biased towards a maximal energy loss because of the extreme in-medium pathlength. We present measurements of di-jets, exploring their structure and properties in Au+Au and p+p at $\sqrt s_{NN}=$200 GeV in the STAR experiment.Comment: Proceedings for the Jets in Proton-Proton and Heavy-Ion Collisions worksho

Heavy-flavour production and multiplicity dependence in pp and p--Pb collisions with ALICE

The production of heavy quarks in pp collisions provides a precision test of perturbative QCD calculations at the LHC energies. More complex collision systems like p--Pb collisions allow studies of cold nuclear matter effects, such as modifications of the parton distribution functions at small x and of the \kt broadening effect. We present the ALICE results of prompt D-meson production as a function of the charged-particle multiplicity, in pp and p--Pb collisions at $\sqrt{s}=7$ TeV and $\sqrt{s_{NN}}=5.02$ TeV respectively. The per-event yield of D mesons in different multiplicity and \pt intervals are compared for pp and p--Pb collisions to study the contribution of multi-parton interactions to open-charm production. Angular correlations of prompt D mesons and heavy-flavour decay electrons with charged hadrons in pp and p-Pb collisions are also shown in different kinematic ranges and compared to pQCD models. These measurements provide information on the charm fragmentation processes, on cold nuclear matter effects on charm production, and on the participation of charm in the collective motion arising in small collision systems like p-Pb.Comment: Proceedings for the LHCP Conference, 201

D-meson nuclear modification factor and v2_2 in Pb-Pb collisions at the LHC

We present the ALICE results on open heavy flavour, focusing on the exclusive reconstruction of charmed mesons via displaced decay topologies. These measurements benefit from the large Pb-Pb statistics collected in 2011. The results on the nuclear modification factor Raa for D mesons indicate a suppression of their yield in central collisions relative to binary-scaled pp collisions in a large momentum range. The comparison to the Raa of non-prompt J/psi (measured with CMS) indicates a difference in the suppression of charm and beauty, as expected according to the predicted mass hierarchy in energy loss models. The measurement of the azimuthal anisotropy of charmed mesons is also discussed. The observed positive second Fourier harmonic v2 for transverse momentum 2<pT<6 GeV/c in semi-peripheral events is a hint for collective motion of charm quarks. The results discussed above are also compared to theoretical models.Comment: Proceedings for the conference Strangeness in Quark Matter, 201

The ‘anti-social’ nature of prosocial research; a psychosocial critique

This article provides a critical review of recent psychological articles on prosocial behaviour. Even though it focuses on a specific section of this literature – giving to charities and prosocial responses to humanitarian disasters – the paper aims to offer a wider critique as it interrogates the epistemological and methodological underpinnings of the prosocial literature as a whole. It aims to illustrate how the problematic aspects of traditional quantitative, deductive, experimental research in prosocial behaviour in general, when applied to giving to charities, preclude a deeper and more complex understanding of a phenomenon quintessentially social and altruistic. I identify three specific issues that make mainstream approaches to prosocial behaviour problematic and limited in scope. The first relates to the insularity of mainstream psychology and the lack of contextualisation of its findings, in particular the problematic neglect of ideological and socio-historical factors in prosocial behaviour. The second relates to mainstream psychology's disregard for the role played by conflict, contradiction and ambivalence, in attitudes and decision making as well as in the emotional aspects of prosocial behaviour. The third looks at the constraints imposed by scientifically inspired methods, how they predetermine the range of participants' responses and make it hard to apply the findings to real life situations. I claim that these epistemological and methodological constraints severely limit the applicability and comprehensiveness of current research. The discussion of these issues is woven through the review and uses some specific studies to illustrate the limitations imposed by these constraints. Throughout the paper I also argue for the need to incorporate a psychosocial approach to research into prosocial behaviour

Rewarding my Self. Self Esteem, Self Determination and Motivations

The paper presents a model where the self esteem and the self determination mechanisms are explicitly modelled in order to explain how they affect the intrinsic motivation and its impact on individual choices. The aim is to reconcile different explanations (and consequences) of the motivation crowding theory in a unique theoretical framework where the locus of control is introduced in a one period maximisation problem and the intrinsic motivation is assumed as an exogenous psychological attitude. The analysis is based on the different effect of the self esteem mechanism on intrinsic motivation input oriented or output oriented. Results show that crowding out of intrinsic motivation depends on the self determination sensitivity and the individual belief about one’s own self.intrinsic motivation; crowding out; self-esteem; self-determination.

Observation of Raman G-band splitting in top-doped few-layer graphene

An experimental study of Raman scattering in N-layer graphene as a function of the top layer doping is reported. At high doping level, achieved by a CHF_3 plasma treatment, we observe a splitting of the $G$ band in the spectra of bilayer and 4-layer graphene (N even), whereas the splitting is not visible in case of monolayer and trilayer graphene (N odd). The different behaviors are related to distinct electron-phonon interactions, which are affected by symmetry breaking and Fermi level position in different ways in the various N-layer graphenes. In trilayer graphene, a weakening of the electron-phonon coupling as a function of the Fermi energy induces a hardening of all zone-center in-plane optical phonon modes, like in monolayer graphene. On the other hand, in 4-layer graphene two distinct trends are observed in the G band as a function of doping, suggesting the presence of two different groups of electron-phonon interactions, like in bilayer graphene.Comment: 7 pages, 6 figures, to be published in PR