Nuclear Isospin Diffusivity

The isospin diffusion and other irreversible phenomena are discussed for a two-component nuclear Fermi system. The set of Boltzmann transport equations, such as employed for reactions, are linearized, for weak deviations of a system from uniformity, in order to arrive at nonreversible fluxes linear in the nonuniformities. Besides the diffusion driven by a concentration gradient, also the diffusion driven by temperature and pressure gradients is considered. Diffusivity, conductivity, heat conduction and shear viscosity coefficients are formally expressed in terms of the responses of distribution functions to the nonuniformities. The linearized Boltzmann-equation set is solved, under the approximation of constant form-factors in the distribution-function responses, to find concrete expressions for the transport coefficients in terms of weighted collision integrals. The coefficients are calculated numerically for nuclear matter, using experimental nucleon-nucleon cross sections. The isospin diffusivity is inversely proportional to the neutron-proton cross section and is also sensitive to the symmetry energy. At low temperatures in symmetric matter, the diffusivity is directly proportional to the symmetry energy.Comment: 35 pages, 1 table, 5 figures, accepted by PRC, (v3) changes in response to the referee's comments, discussion for isospin diffusion process in heavy-ion reactions, fig. 5 shows results from a two different isospin depndent uclear equation of state, and a new reference adde

Temporal behavior and quantum Zeno time of an excited state of the hydrogen atom

The quantum "Zeno" time of the 2P-1S transition of the hydrogen atom is computed and found to be approximately 3.59 10^{-15}s (the lifetime is approximately 1.595 10^{-9}s). The temporal behavior of this system is analyzed in a purely quantum field theoretical framework and is compared to the exponential decay law.Comment: 11 page

Snyder space revisited

We examine basis functions on momentum space for the three dimensional Euclidean Snyder algebra. We argue that the momentum space is isomorphic to the SO(3) group manifold, and that the basis functions span either one of two Hilbert spaces. This implies the existence of two distinct lattice structures of space, on which continuous rotations and translations are unitarily implementable.Comment: 22 page

Sustainability motivations and practices in small tourism enterprises in European protected areas

A survey of around 900 tourism enterprises in 57 European protected areas shows that small firms are more involved in taking responsibility for being sustainable than previously expected, including eco-savings related operational practices but also reporting a wide range of social and economic responsibility actions. Two-step cluster analysis was used to group the firms in three groups based on their motivations to be sustainable. Business driven firms implement primarily eco-savings activities and are commercially oriented. Legitimization driven firms respond to perceived stakeholder pressure and report a broad spectrum of activities. Lifestyle and value driven firms report the greatest number of environmental, social and economic activities. No profile has a higher business performance than average. The study has implications for policy programmes promoting sustainability behaviour change based primarily on a business case argument

Van Hove's "\lambda^2 t" limit in nonrelativistic and relativistic field-theoretical models

Van Hove's "\lambda^2 t" limiting procedure is analyzed in some interesting quantum field theoretical cases, both in nonrelativistic and relativistic models. We look at the deviations from a purely exponential behavior in a decay process and discuss the subtle issues of state preparation and initial time.Comment: 18 pages, 4 figure

Emergence of a Wiener process as a result of the quantum mechanical interaction with a macroscopic medium

We analyze a modified version of the Coleman-Hepp model, that is able to take into account energy-exchange processes between the incoming particle and the linear array made up of $N$ spin-1/2 systems. We bring to light the presence of a Wiener dissipative process in the weak-coupling, macroscopic ($N \rightarrow \infty$) limit. In such a limit and in a restricted portion of the total Hilbert space, the particle undergoes a sort of Brownian motion, while the free Hamiltonian of the spin array serves as a Wiener process. No assumptions are made on the spectrum of the Hamiltonian of the spin system, and no partial trace is computed over its states. The mechanism of appearance of the stochastic process is discussed and contrasted to other noteworthy examples in the literature. The links with van Hove's ``$\lambda^2 T$ limits are emphasized.Comment: 20 pages, LaTeX, no figure

Deviations from exponential law and Van Hove's "\lambda^2 t" limit

The deviations from a purely exponential behavior in a decay process are analyzed in relation to Van Hove's "\lambda^2 t" limiting procedure. Our attention is focused on the effects that arise when the coupling constant is small but nonvanishing. We first consider a simple model (two-level atom in interaction with the electromagnetic field), then gradually extend our analysis to a more general framework. We estimate all deviations from exponential behavior at leading orders in the coupling constant.Comment: 18 pages, 3 figure

Spontaneous emission and lifetime modification caused by an intense electromagnetic field

We study the temporal evolution of a three-level system (such as an atom or a molecule), initially prepared in an excited state, bathed in a laser field tuned at the transition frequency of the other level. The features of the spontaneous emission are investigated and the lifetime of the initial state is evaluated: a Fermi "golden rule" still applies, but the on-shell matrix elements depend on the intensity of the laser field. In general, the lifetime is a decreasing function of the laser intensity. The phenomenon we discuss can be viewed as an "inverse" quantum Zeno effect and can be analyzed in terms of dressed states.Comment: 25 pages, 6 figure

Glas som konstruktionsmaterial: en genomgång av glaskonstruktioners användningsmöjligheter och dess brandsäkerhet

Detta arbete har gjorts kring glas som material och de vanligaste profilsystemen. Syftet var att få en bättre översikt över glas som byggmaterial och vad man ska tänka på vid konstruktionsplanering. Detta examensarbete utfördes åt IdeaStructura i Karleby. Det var även företagets önskan att en handbokslikande text skulle tas fram. Metodval har varit litteraturstudier om bestämmelser och anvisningar samt undersökning av vad företag har för glasprodukter att erbjuda. I examensarbetet presenteras fakta om glas som byggmaterial, glasets egenskaper, samt de vanligaste glas- och ramsystemen. I slutet av arbetet beskrivs även hur man brandsäkrar byggnader.Tämä työ on tehty lasin materiaalin ja yleisimpien profiilijärjestelmien ympärille. Tavoitteena oli saada parempi käsitys lasista rakennusmateriaalina ja mitä tulee ottaa huomioon rakentamisen suunnittelussa. Tämä opinnäytetyö tehtiin IdeaStructuralle Kokkolassa. Yrityksen toive oli myös saada käsikirjamainen teksti. Menetelmänä on valittu kirjallisuustutkimuksia määräyksistä ja ohjeista sekä tutkimus siitä, millaisia lasituotteita yrityksillä on tarjota. Opinnäytetyössä esitellään faktoja lasista rakennusmateriaalina, lasin ominaisuuksista sekä yleisimmistä lasi- ja runkojärjestelmistä. Työn lopussa kuvataan myös rakennusten tulenkestämistä.This work has been done around glass as a material and the most common profile systems. The aim was to get a better overview of glass as a building material and what to consider when planning construction. This thesis was carried out for IdeaStructura in Kokkola. It was also the company's wish that a manual would be produced. The choice of method has been literature studies on regulations and instructions as well as research into what kind of glass products companies have to offer. The thesis presents facts about glass as a building material, the properties of glass, as well as the most common glass and frame systems. At the end of the work, how to fireproof buildings is also described