International perspectives on the "Great Moderation"

Macroeconomics

Forecasting with mixed frequencies

A dilemma faced by forecasters is that data are not all sampled at the same frequency. Most macroeconomic data are sampled monthly (e.g., employment) or quarterly (e.g., GDP). Most financial variables (e.g., interest rates and asset prices), on the other hand, are sampled daily or even more frequently. The challenge is how to best use available data. To that end, the authors survey some common methods for dealing with mixed-frequency data. They show that, in some cases, simply averaging the higher-frequency data produces no discernible disadvantage. In other cases, however, explicitly modeling the flow of data (e.g., using mixed data sampling as in Ghysels, Santa-Clara, and Valkanov, 2004) may be more beneficial to the forecaster, especially if the forecaster is interested in constructing intra-period forecasts.Economic forecasting ; Econometric models

Hanbury-Brown-Twiss measurements at large rapidity separations, or can we measure the proton radius in p-A collisions?

We point out that current calculations of inclusive two-particle correlations in p-A collisions based on the Color Glass Condensate approach exhibit a contribution from Hanbury-Brown-Twiss correlations. These HBT correlations are quite distinct from the standard ones, in that they are apparent for particles widely separated in rapidity. The transverse size of the emitter which is reflected in these correlations is the gluonic size of the proton. This raises an interesting possibility of measuring the proton size directly by the HBT effect of particle pairs produced in p-A collisions.Comment: 11 pages, 3 eps figures; v2: comments, discussions, references and acknowledgements added, conclusions unchanged, final versio

Diffractive photoproduction of heavy quarks in hadronic collisions

In this letter we study the diffractive photoproduction of heavy quarks in hadronic (pp/pA/AA) interactions for Tevatron and LHC energies. The integrated cross section and rapidity distribution for the process h_1 h_2 --> h_1 h_2 QQBAR (h_i = p,A and Q = c,b) are estimated using the Color Glass Condensate (CGC) formalism. Our results indicate that this production channel has larger cross sections than the competing reactions of double diffractive production and coherent AA reactions initiated by two-photon collisions.Comment: 4 pages, 2 figures, 1 table. Version to be published in Physical Review

Holographic Screening Length in a Hot Plasma of Two Sphere

We study the screening length of a quark-antiquark pair moving in a hot plasma living in two sphere $S^2$ manifold using AdS/CFT correspondence where the background metric is four dimensional Schwarzschild-AdS black hole. The geodesic solution of the string ends at the boundary is given by a stationary motion in the equatorial plane as such the separation length $L$ of quark-antiquark pair is parallel to the angular velocity $\omega$. The screening length and the bound energy are computed numerically using Mathematica. We find that the plots are bounded from below by some functions related to the momentum transfer $P_c$ of the drag force configuration. We compare the result by computing the screening length in the quark-antiquark reference frame where the gravity dual are "Boost-AdS" and Kerr-AdS black holes. Finding relations of the parameters of both black holes, we argue that the relation between mass parameters $M_{Sch}$ of the Schwarzschild-AdS black hole and $M_{Kerr}$ of the Kerr-AdS black hole in high temperature is given by $M_{Kerr}=M_{Sch}(1-a^2l^2)^{3/2}$, where $a$ is the angular momentum parameter.Comment: Major revision: title changed, adding authors, 13 pages, 8 figures, etc. Accepted for publication in European Physical Journal

Nuclear charm and bottom production: a comparison among high energy approaches

We calculate the nucleon and nuclear photoproduction cross sections for heavy quarks within the $k_{\perp}$-factorization formalism, considering the current high energy approaches which include nuclear and saturation effects. Our results demonstrate that a future experimental analysis of this process would allow to constraint the QCD dynamics at high energies.Comment: 10 pages, 2 figures. Version to be published in Eur. Phys. J.

Transverse momentum distributions and their forward- backward correlations in the percolating colour string approach

The forward-backward correlations in the $p_T$ distributions, which present a clear signature of non-linear effects in particle production, are studied in the model of percolating colour strings. Quantitative predictions are given for these correlations at SPS, RHIC and LHC energies. Interaction of strings also naturally explains the flattening of $p_T$ distributions and increase of $$ with energy and atomic number for nuclear collisionsComment: 6 pages in LaTex, 3 figures in Postscrip

Percolation approach to quark gluon plasma in high energy pp collisions

We apply continuum percolation to proton-proton collisions and look for the possible threshold to phase transition from confined nuclear matter to quark gluon plasma. Making the assumption that J/Psi suppression is a good signal to the transition, we discuss this phenomenon for pp collisions, in the framework of a dual model with strings.Comment: 8 pages, 3 figure

The QCD Pomeron in ultraperipheral heavy ion collisions: III. Photonuclear production of heavy quarks

We calculate the photonuclear production of heavy quarks in ultraperipheral heavy ion collisions. The integrated cross section and the rapidity distribution are computed employing sound high energy QCD formalisms as the collinear and semihard approaches as well as the saturation model. In particular, the color glass condensate (CGC) formalism is also considered using a simple phenomenological parameterization for the color field correlator in the medium, which allow us to obtain more reliable estimates for charm and bottom production at LHC energies.Comment: 15 pages, 2 figures. Extended version to be published in Eur. Phys. J.

Adult-Onset Eccrine Angiomatous Hamartoma: A Case Report With Ultrasound Findings

[Abstract] Eccrine angiomatous hamartoma (EAH) is a rare, benign cutaneous tumor composed of vascular and eccrine elements. It is most commonly diagnosed during the first years of life, although there are reports of cases diagnosed in adults. We report the ultrasound findings of a 46-year-old patient with a left plantar lesion, histopathological diagnosis of which confirmed suspicion of EAH