Discrete Convex Functions on Graphs and Their Algorithmic Applications

The present article is an exposition of a theory of discrete convex functions on certain graph structures, developed by the author in recent years. This theory is a spin-off of discrete convex analysis by Murota, and is motivated by combinatorial dualities in multiflow problems and the complexity classification of facility location problems on graphs. We outline the theory and algorithmic applications in combinatorial optimization problems

Initial condition of scalar perturbation in inflation

A formula for the power spectrum of curvature perturbations having any initial conditions in inflation is obtained. Based on the physical conditions before inflation, the possibility exists that the initial state of scalar perturbations is not only the Bunch-Davies state, but also a more general state (a squeezed state). For example, the derived formula for the power spectrum is calculated using simple toy cosmological models. When there exists a radiation-dominated period before inflation, the behavior of the scalar perturbation is revealed not to vary greatly; however, from large scales to small scales the power spectrum of the curvature perturbations oscillates around the normal value. In addition, when inflation has a large break and the breaking time is a radiation- dominated period, a large enhancement is revealed to occur which depends on the length of the breaking time.Comment: 24 pages,3 figue

Parametrization of nuclear parton distributions

Optimum nuclear parton distributions are obtained by analyzing available experimental data on electron and muon deep inelastic scattering (DIS). The distributions are given at Q^2=1 GeV^2 with a number of parameters, which are determined by a chi^2 analysis of the data. Valence-quark distributions are relatively well determined at medium x, but they are slightly dependent on the assumed parametrization form particularly at small x. Although antiquark distributions are shadowed at small x, their behavior is not obvious at medium x from the F_2 data. The gluon distributions could not be restricted well by the inclusive DIS data; however, the analysis tends to support the gluon shadowing at small x. We provide analytical expressions and computer subroutines for calculating the nuclear parton distributions, so that other researchers could use them for applications to other high-energy nuclear reactions.Comment: 1+11 pages, LaTeX, amsmath.sty, wrapfig.sty, graphicx.sty, ias.cls, ias.sty, pramana.sty, pmana10.sty, pbib.sty, times.sty, 9 eps figures. Invited talk given at the International Symposium on Nuclear Physics, Mumbai, India, Dec. 18-22, 2000, to be published in proceedings. Complete postscript file is available at http://www-hs.phys.saga-u.ac.jp Email: [email protected], [email protected], [email protected]

Comportamento populacional de cupiúba (Goupia glabra Aubl.) em floresta de terra firme na fazenda Rio Capim, Paragominas (PA).

Goupia glabra Aublet, popularmente conhecida como cupiúba, é uma espécie arbórea da família Celastraceae. Possui árvores de grande porte, podendo muitas vezes ocupar a posição de dossel superior em florestas primárias. É uma espécie de grande importância econômica para a região onde ocorre e para o país, sendo comercializada, inclusive, no mercado internacional, devido seus diversos usos e características peculiares. O presente estudo cruza conhecimentos de botânica, ecologia e importância comercial da espécie com informações do comportamento estrutural da cupiúba, a fim de facilitar ações de bom manejo silvicultural, inclusive juntamente com outras espécies que compõe a comunidade na área estudada e na região. Em 84 ha de floresta natural densa de terra firme, na Fazenda Rio Capim, de propriedade da Cikel Brasil Verde S. A., no município de Paragominas (PA), Goupia glabra foi uma das espécies mais representativas quanto ao seu grupo na estrutura florestal, sendo de grande importância ecológica naquela área. Considerando as árvores com diâmetro acima de 45 cm, a espécie apresenta abundância de 0,81 árvore/ha, freqüência de 100%, com área basal de 0,41 m2/ha, volume de 2,58 m3/ha, distribuição diamétrica em todas as classes de árvores, de 45 cm até 144 cm, e qualidade de fuste bem representativa para comercialização.Publicado também on-line

Coexistence of Superconductivity and Charge Density Wave in SrPt2As2

SrPt2As2 is a novel arsenide superconductor, which crystallizes in the CaBe2Ge2-type structure as a different polymorphic form of the ThCr2Si2-type structure. SrPt2As2 exhibits a charge-density-wave (CDW) ordering at about 470 K and enters into a superconducting state at Tc = 5.2 K. The coexistence of superconductivity and CDW refers to Peierls instability with a moderately strong electron-phonon interaction. Thus SrPt2As2 can be viewed as a nonmagnetic analog of iron-based superconductors, such as doped BaFe2As2, in which superconductivity emerges in close proximity to spin-density-wave ordering.Comment: 4 pages, 5 figure

Impact-parameter dependent nuclear parton distribution functions: EPS09s and EKS98s and their applications in nuclear hard processes

We determine the spatial (impact parameter) dependence of nuclear parton distribution functions (nPDFs) using the $A$-dependence of the spatially independent (averaged) global fits EPS09 and EKS98. We work under the assumption that the spatial dependence can be formulated as a power series of the nuclear thickness functions $T_A$. To reproduce the $A$-dependence over the entire $x$ range we need terms up to $[T_A]^4$. As an outcome, we release two sets, EPS09s (LO, NLO, error sets) and EKS98s, of spatially dependent nPDFs for public use. We also discuss the implementation of these into the existing calculations. With our results, the centrality dependence of nuclear hard-process observables can be studied consistently with the globally fitted nPDFs for the first time. As an application, we first calculate the LO nuclear modification factor $R^{1jet}_{AA}$ for primary partonic-jet production in different centrality classes in Au+Au collisions at RHIC and Pb+Pb collisions at LHC. Also the corresponding central-to-peripheral ratios $R_{CP}^{1jet}$ are studied. We also calculate the LO and NLO nuclear modification factors for single inclusive neutral pion production, $R_{dAu}^{\pi^0}$, at mid- and forward rapidities in different centrality classes in d+Au collisions at RHIC. In particular, we show that our results are compatible with the PHENIX mid-rapidity data within the overall normalization uncertainties given by the experiment. Finally, we show our predictions for the corresponding modifications $R_{pPb}^{\pi^0}$ in the forthcoming p+Pb collisions at LHC.Comment: 36 page

Nuclear Effects on Heavy Boson Production at RHIC and LHC

We predict W and Z transverse momentum distributions from proton-proton and nuclear collisions at RHIC and LHC. A resummation formalism with power corrections to the renormalization group equations is used. The dependence of the resummed QCD results on the non-perturbative input is very weak for the systems considered. Shadowing effects are discussed and found to be unimportant at RHIC, but important for LHC. We study the enhancement of power corrections due to multiple scattering in nuclear collisions and numerically illustrate the weak effects of the dependence on the nuclear mass.Comment: 21 pages, 11 figure

Medium-induced gluon radiation and jet quenching in heavy ion collisions

In this brief review, I summarize the new developments on the description of gluon radiation by energetic quarks traversing a medium as well as the observable consequences in high-energy heavy ion collisions. Information about the initial state is essential for a reliable interpretation of the experimental results and will also be reviewed. Comparison with experimental data from RHIC and expectation for the future LHC will be given.Comment: 16 pages, 9 postscript figures. Invited brief review for Modern Physics Letters