14,292 research outputs found
Bootstraping the QCD Critical Point
It is shown that hadronic matter formed at high temperatures, according to
the prescription of the statistical bootstrap principle, develops a critical
point at nonzero baryon chemical potential. The location of the critical point
in the phase diagram, however, depends on the detailed knowledge of the
partition function of the deconfined phase, near the critical line. In a
simplified version of the quark-gluon partition function, the resulting
location of the critical point is compared with the solutions of other
approaches and in particular with the results of lattice QCD. The proximity of
our solution to the freeze-out area in heavy-ion experiments is also discussed.Comment: 10 pages, 3 figures in 4 file
A flexible framework for defeasible logics
Logics for knowledge representation suffer from over-specialization: while
each logic may provide an ideal representation formalism for some problems, it
is less than optimal for others. A solution to this problem is to choose from
several logics and, when necessary, combine the representations. In general,
such an approach results in a very difficult problem of combination. However,
if we can choose the logics from a uniform framework then the problem of
combining them is greatly simplified. In this paper, we develop such a
framework for defeasible logics. It supports all defeasible logics that satisfy
a strong negation principle. We use logic meta-programs as the basis for the
framework.Comment: Proceedings of 8th International Workshop on Non-Monotonic Reasoning,
April 9-11, 2000, Breckenridge, Colorad
Pion production from a critical QCD phase
A theoretical scheme which relates multiparticle states generated in
ultrarelativistic nuclear collisions to a QCD phase transition is considered in
the framework of the universality class provided by the 3-D Ising model. Two
different evolution scenarios for the QGP system are examined. The statistical
mechanics of the critical state is accounted for in terms of (critical) cluster
formation consistent with suitably cast effective action functionals, one for
each considered type of expansion. Fractal properties associated with these
clusters, characterizing the density fluctuations near the QCD critical point,
are determined. Monte-Carlo simulations are employed to generate events,
pertaining to the total system, which correspond to signals associated with
unconventional sources of pion production
Urban Environmental Planning in Greek Cities - The response of medium sized Greek cities, the case of Volos
The city is a vital sum of functions, of human actions, of resources and of a built and physical environment. The sustainability of cities is relatively a new area of interest, especially for the Greek cities. Only in the last decade was sustainability introduced to the Greek planning process. Unfortunately, the Greek cities do not follow the Local Agenda 21, an instrument that is trying to promote sustainability issues for the built environment. The city of Volos in Greece seems to be more sensitive in the environmental and sustainable development issues than other Greek cities due to its proximity to vital natural resources and to a unique position between sea and mountain. Further more Volos is one of the few medium sized cities in Greece that have a local agenda 21 and numerous Life and EMAS smaller more focused projects. Even if the city of Volos is not the leader city in the cases of sustainability nevertheless the city has undertaken lots of initiatives, projects and programmes to promote the sustainability issues. Therefore, it is worthwhile to study the way in which the city faces the sustainability and could act as a useful example for the sustainable urban planning in Greece.
Supersymmetric V-systems
We construct superconformal quantum
mechanical system for any configuration of vectors forming a V-system. In the
case of a Coxeter root system the bosonic potential of the supersymmetric
Hamiltonian is the corresponding generalised Calogero-Moser potential. We also
construct supersymmetric generalised trigonometric Calogero-Moser-Sutherland
Hamiltonians for some root systems including .Comment: 31 pages; minor change
Analytical considerations for linear and nonlinear optimization of the TME cells. Application to the CLIC pre-damping rings
The theoretical minimum emittance cells are the optimal configurations for
achieving the absolute minimum emittance, if specific optics constraints are
satisfied at the middle of the cell's dipole. Linear lattice design options
based on an analytical approach for the theoretical minimum emittance cells are
presented in this paper. In particular the parametrization of the quadrupole
strengths and optics functions with respect to the emittance and drift lengths
is derived. A multi-parametric space can be then created with all the cell
parameters, from which one can chose any of them to be optimized. An
application of this approach are finally presented for the linear and
non-linear optimization of the CLIC Pre-damping rings.Comment: Submitted for publication in Physical Review Special Topics -
Accelerators and Beam
Technical considerations towards mobile user QoE enhancement via Cloud interaction
This paper discusses technical considerations of a Cloud infrastructure which interacts with mobile devices in order to migrate part of the computational overhead from the mobile device to the Cloud. The aim of the interaction between the mobile device and the Cloud is the enhancement of parameters that affect the Quality of Experience (QoE) of the mobile end user through the offloading of computational aspects of demanding applications. This paper shows that mobile user’s QoE can be potentially enhanced by offloading computational tasks to the Cloud which incorporates a predictive context-aware mechanism to schedule delivery of content to the mobile end-user using a low-cost interaction model between the Cloud and the mobile user. With respect to the proposed enhancements, both the technical considerations of the cloud infrastructure are examined, as well as the interaction between the mobile device and the Cloud
Extending Topological Surgery to Natural Processes and Dynamical Systems
Topological surgery is a mathematical technique used for creating new
manifolds out of known ones. We observe that it occurs in natural phenomena
where a sphere of dimension 0 or 1 is selected, forces are applied and the
manifold in which they occur changes type. For example, 1-dimensional surgery
happens during chromosomal crossover, DNA recombination and when cosmic
magnetic lines reconnect, while 2-dimensional surgery happens in the formation
of tornadoes, in the phenomenon of Falaco solitons, in drop coalescence and in
the cell mitosis. Inspired by such phenomena, we introduce new theoretical
concepts which enhance topological surgery with the observed forces and
dynamics. To do this, we first extend the formal definition to a continuous
process caused by local forces. Next, for modeling phenomena which do not
happen on arcs or surfaces but are 2-dimensional or 3-dimensional, we fill in
the interior space by defining the notion of solid topological surgery. We
further introduce the notion of embedded surgery in for modeling
phenomena which involve more intrinsically the ambient space, such as the
appearance of knotting in DNA and phenomena where the causes and effect of the
process lies beyond the initial manifold, such as the formation of black holes.
Finally, we connect these new theoretical concepts with a dynamical system and
we present it as a model for both 2-dimensional 0-surgery and natural phenomena
exhibiting a `hole drilling' behavior. We hope that through this study,
topology and dynamics of many natural phenomena, as well as topological surgery
itself, will be better understood.Comment: 54 pages, 34 figure
Dynamical Systems and Topological Surgery
In this paper we try to establish a connection between a three-dimensional
Lotka--Volterra dynamical system and two-dimensional topological surgery. There
are many physical phenomena exhibiting two-dimensional topological surgery
through a `hole drilling' process. By our connection, such phenomena may be
modelled mathematically by the above dynamical system.Comment: 16 pages, 14 figure
- …