69,285 research outputs found
Evaluating and improving firewalls for ip-telephony environments
Firewalls are a well established security mechanism for providing access control and auditing at the borders between different administrative network domains. Their basic architecture, techniques and operation modes did not change fundamentally during the last years. On the other side new challenges emerge rapidly when new innovative application domains have to be supported. IP-Telephony applications are considered to have a huge economic potential in the near future. For their widespread acceptance and thereby their economic success they must cope with established security policies. Existing firewalls face immense problems here, if they - as it still happens quite often - try to handle the new challenges in a way they did with "traditional applications". As we will show in this paper, IP-Telephony applications differ from those in many aspects, which makes such an approach quite inadequate. After identifying and characterizing the problems we therefore describe and evaluate a more appropriate approach. The feasibility of our architecture will be shown. It forms the basis of a prototype implementation, that we are currently working on
On the anomalous dimension for the transversity distribution
We show that a standard calculation of the splitting function for the
nonsinglet structure function h_1 does not lead to the expected result. The
calculation is compared to the corresponding derivation of the splitting
function for the nonsinglet polarized structure function g_1. We analyze
possible explanations for the unexpected result and discuss its implications.
PACS: 11.10.Hi; 11.40.-q; 11.55.Ds; 13.88.+eComment: 8 pages, 1 figure, 2 references adde
A Parameterised Hierarchy of Argumentation Semantics for Extended Logic Programming and its Application to the Well-founded Semantics
Argumentation has proved a useful tool in defining formal semantics for
assumption-based reasoning by viewing a proof as a process in which proponents
and opponents attack each others arguments by undercuts (attack to an
argument's premise) and rebuts (attack to an argument's conclusion). In this
paper, we formulate a variety of notions of attack for extended logic programs
from combinations of undercuts and rebuts and define a general hierarchy of
argumentation semantics parameterised by the notions of attack chosen by
proponent and opponent. We prove the equivalence and subset relationships
between the semantics and examine some essential properties concerning
consistency and the coherence principle, which relates default negation and
explicit negation. Most significantly, we place existing semantics put forward
in the literature in our hierarchy and identify a particular argumentation
semantics for which we prove equivalence to the paraconsistent well-founded
semantics with explicit negation, WFSX. Finally, we present a general proof
theory, based on dialogue trees, and show that it is sound and complete with
respect to the argumentation semantics.Comment: To appear in Theory and Practice of Logic Programmin
SU(2) and SU(3) Yang-Mills thermodynamics and some implications
We sketch the development of effective theories for SU(2) and SU(3)
Yang-Mills thermodynamics. The most important results are quoted and some
implications for particle physics and cosmology are discussed.Comment: 18 pages, 5 figures, v3: consequences of a change in the evolution
equations for the effective couplings implemented, practically no change in
the physics, erratum to appear in the journal-published versio
Fundamental and effective SU(2) Yang-Mills vertices
Calorons and plane waves within and in between them {\sl collectively} give
rise to a thermal ground state. The latter provides a homgeneous energy density
and a negative pressure, and it induces quasiparticle masses to part of the
propagating spectrum of deconfining SU(2) Yang-Mills thermodynamics (dynamical
gauge-symmetry breaking). In the present talk we discuss the role of a {\sl
single} caloron in inducing effective local vertices, characterized by powers
of , mediating the interaction of plane waves which propagate over large
distances. The constraints on momentum transfers through effective 4-vertices
are revisited.Comment: 4 pages, no figur
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