Quantum intersection rings

We examine a few problems of enumerative geometry and present their solutions in the framework of deformed (quantum) cohomology rings.Comment: 73 p, uuencoded, uses harvmac in b mode, 6 figures include

Anti-transpirant effects on vine physiology, berry and wine composition of cv. Aglianico (Vitis vinifera L.) Grown in South Italy

In viticulture, global warming requires reconsideration of current production models. At the base of this need there are some emerging phenomena: modification of phenological phases; acceleration of the maturation process of grapes, with significant increases in the concentration of sugar musts; decoupling between technological grape maturity and phenolic maturity. The aim of our study was to evaluate the effect of a natural anti-transpirant on grapevine physiology, berry, and wine composition of Aglianico cultivar. For two years, Aglianico vines were treated at veraison with the anti-transpirant Vapor Gard and compared with a control sprayed with only water. A bunch thinning was also applied to both treatments. The effectiveness of Vapor Gard were assessed through measurements of net photosynthesis and transpiration and analyzing the vegetative, productive and qualitative parameters. The results demonstrate that the application of antitranspirant reduced assimilation and transpiration rate, stomatal conductance, berry sugar accumulation, and wine alcohol content. No significant differences between treatments were observed for other berry and wine compositional parameters. This method may be a useful tool to reduce berry sugar content and to produce wines with a lower alcohol content

Luttinger liquid, singular interaction and quantum criticality in cuprate materials

With particular reference to the role of the renormalization group approach and Ward identities, we start by recalling some old features of the one-dimensional Luttinger liquid as the prototype of non-Fermi-liquid behavior. Its dimensional crossover to the Landau normal Fermi liquid implies that a non-Fermi liquid, as, e.g., the normal phase of the cuprate high temperature superconductors, can be maintained in d>1, only in the presence of a sufficiently singular effective interaction among the charge carriers. This is the case when, nearby an instability, the interaction is mediated by fluctuations. We are then led to introduce the specific case of superconductivity in cuprates as an example of avoided quantum criticality. We will disentangle the fluctuations which act as mediators of singular electron-electron interaction, enlightening the possible order competing with superconductivity and a mechanism for the non-Fermi-liquid behavior of the metallic phase. This paper is not meant to be a comprehensive review. Many important contributions will not be considered. We will also avoid using extensive technicalities and making full calculations for which we refer to the original papers and to the many good available reviews. We will here only follow one line of reasoning which guided our research activity in this field.Comment: 23 pages, 10 figure

A Generating Function for Fatgraphs

We study a generating function for the sum over fatgraphs with specified valences of vertices and faces, inversely weighted by the order of their symmetry group. A compact expression is found for general (i.e. non necessarily connected) fatgraphs. This expression admits a matrix integral representation which enables to perform semi--classical computations, leading in particular to a closed formula corresponding to (genus zero, connected) trees.Comment: 24 pages, uses harvmac macro, 1 figure not included, Saclay preprint SPhT/92-16

Ion-supported tori: a thermal bremsstrahlung model for the X-ray Background

We discuss the possibility that a significant contribution of the hard X-ray Background is the integrated emission from a population of galaxies undergoing advection-dominated accretion in their nuclei. Owing to poor coupling between ions and electrons and to efficient radiative cooling of the electrons, the accreting plasma is two-temperature, with the ions being generally much hotter than the electrons and forming an ion-supported torus. We show that the electron te mperature then saturates at approximately 100keV independent of model parameters. At this temperature the hard X-ray emission is dominated by bremsstrahlung radiation. We find that this physical model gives an excellent fit to the spectrum of the XRB in the 3-60 keV range, provided that there is some evolution associated with the spectral emissivity which must peak at a redshift of about 2. We estimate that such galaxies contribute only to a small fraction of the local X-ray volume emissivity. The model implies a higher mean black hole mass than is obtained from the evolution of quasars alone.Comment: 7 pages, 7 ps figures, uses mn.sty (included). Submitted for publication to MNRA

Expected sensitivity of ARGO-YBJ to detect point gamma-ray sources

ARGO-YBJ is a full coverage air shower detector currently under construction at the Yangbajing Laboratory (4300 m a.s.l., Tibet, China). First data obtained with a subset of the apparatus will be available in summer 2003 while the full detector operation is expected in 2005. One of the main aims of ARGO-YBJ is the observation of gamma-ray sources, at an energy threshold of a few hundreds GeV. In this paper we present the expected sensitivity to detect point gamma ray sources, with particular attention to the Crab Nebula. According to our simulations a Crab-like signal could be detected in one year of operation with a statistical significance of 10 standard deviations, without any gamma/hadron discrimination.Comment: 4 pages, 2 Postscript figure