Finite Temperature Simulations from Quantum Field Dynamics?

We describe a Hartree ensemble method to approximately solve the Heisenberg equations for the \phi^4 model in 1+1 dimensions. We compute the energies and number densities of the quantum particles described by the \phi field and find that the particles initially thermalize with a Bose-Einstein distribution for the particle density. Gradually, however, the distribution changes towards classical equipartition. Using suitable initial conditions quantum thermalization is achieved much faster than the onset of this undesirable equipartition. We also show how the numerical efficiency of our method can be significantly improved.Comment: Lattice 2000 (Finite Temperature), 4 pages, 5 figures; title correcte

Staying Thermal with Hartree Ensemble Approximations

We study thermal behavior of a recently introduced Hartree ensemble approximation, which allows for non-perturbative inhomogeneous field configurations as well as for approximate thermalization, in the $\phi^4$ model in 1+1 dimensions. Using ensembles with a free field thermal distribution as out-of-equilibrium initial conditions we determine thermalization time scales. The time scale for which the system stays in approximate quantum thermal equilibrium is an indication of the time scales for which the approximation method stays reasonable. This time scale turns out to be two orders of magnitude larger than the time scale for thermalization, in the range of couplings and temperatures studied. We also discuss simplifications of our method which are numerically more efficient and make a comparison with classical dynamics.Comment: 19 pages latex; extensively rewritten to improve presentation, data essentially unchanged, analysis sharpened and one table adde

The Hartree ensemble approximation revisited: The "symmetric phase"

The Hartree ensemble approximation is studied in the ``symmetric phase'' of 1+1 dimensional lambda phi^4 theory. In comparison with the ``broken phase'' studied previously, it is shown that the dynamical evolution of observables such as the particle distribution, energy exchange and auto-correlation functions, is substantially slower. Approximate thermalization is found only for relatively large energy densities and couplings.Comment: 17 pages RevTeX, 16 figures, 3 tables, uses amsmath and feynmp. Extended some sections, reordered Sec.IV, added 3 refs, numerical typo corrected, published versio

Guidelines for expressing community user identifiers (AARC-G026)

This document provides guidelines for expressing Community User Identifiers (CUIDs) such that the identifier values can be transported in an interoperable way across AARC Blueprint Architecture (BPA) compliant Authentication & Authorisation Infrastructures (AAIs). The CUID is a subject identifier, where the subjects are generally but not exclusively natural persons. The community user identifier is an attribute of the subject’s digital identity which is managed by the Community AAI. The guidelines specify how the CUID is communicated from the Community AAI to its connected services, i.e. infrastructure services (accessible through Infrastructure Proxies), generic and community services

Guidelines for Secure Operation of Attribute Authorities and other issuers of access-granting statements

These guidelines describe the minimum requirements and recommendations for the secure operation of Attribute Authorities and similar services providing statements for the purpose of obtaining access to infrastructure services. Stated compliance with these guidelines may help to establish trust between issuers and Relying Parties. This document does not define an accreditation process

A specification for IdP hinting (AARC-G061)

This document defines a generic browser-based protocol for conveying - to services - hints about the IdPs or SP-IdP-proxies that should be used for authenticating the principal. This protocol, colloquially referred to as Identity Provider (IdP) hinting, can greatly simplify the discovery process for the end-user, by enabling entities to produce and send hints that can be consumed by SP-IdP-proxies for routing the user to the correct upstream SP-IdP-Proxy or authenticating IdP

A specification for providing information about an end service to a Discovery Service (AARC-G063)

This specification defines how SP-IdP Proxies can provide hints about services towards Discovery Services to improve the user experience of the authentication process

Kinks in the Hartree approximation

The topological defects of the lambda phi^4 theory, kink and antikink, are studied in the Hartree approximation. This allows us to discuss quantum effects on the defects in both stationary and dynamical systems. The kink mass is calculated for a number of parameters, and compared to classical, one loop and Monte Carlo results known from the literature. We discuss the thermalization of the system after a kink antikink collision. A classical result, the existence of a critical speed, is rederived and shown for the first time in the quantum theory. We also use kink antikink collisions as a very simple toy model for heavy ion collisions and discuss the differences and similarities, for example in the pressure. Finally, using the Hartree Ensemble Approximation allows us to study kink antikink nucleation starting from a thermal (Bose Einstein) distribution. In general our results indicate that on a qualitative level there are few differences with the classical results, but on a quantitative level there are some import ones.Comment: 20 pages REVTeX 4, 17 Figures. Uses amsmath.sty and subfigure.sty. Final version, fixed typo in published versio

Guidelines for expressing group membership and role information (AARC-G069)

Information about the groups a user is a member of is commonly used by relying parties in order to authorise user access to protected resources. This document provides guidelines for expressing group membership and role information across AARC BPA-compliant AAI services. Specifically, it defines a URN namespace for expressing this information using common identity federation protocols, namely SAML and OpenID Connect/OAuth2

Guidelines for Secure Operation of Attribute Authorities and issuers of statements for entities (G071)

These guidelines describe the minimum requirements and recommendations for the secure operation of attribute authorities and similar services that make statements about an entity based on well-defined attributes. Adherence to these guidelines may help to establish trust between communities, operators of attribute authorities and issuers, and Relying Parties, infrastructures, and service providers. This document does not define an accreditation process