on 17-09-2014
Networks 2014 will focus on the challenges of planning and design networks to deliver on the promise of convergence of the information and communication technologies (ICT) and next generation networks (NGN). The challenges are many: how to build high performance networks for converged services where every step is cost justified and drives profitable growth, where difficult issues of scalability, end-to-end network performance, network management, network and service control, reliability, security and interoperability are planned and then
realized, and where flexibility is maintained to allow experimentation with new applications that can foster new and compelling revenue streams for operators. Unleashing the core value of convergence requires innovation in network planning methods, scalable architectures, new optimization algorithms, and understanding the tradeoffs between different technology choices and migration paths. Networks 2014 is the 16th of such symposia, held every two years, and attracting participants from all over the world: network operators, software companies, system integrators, researchers from universities and industry, marketers and policy-makers, regulators. At Networks 2014 we will continue the tradition of state-of-the art papers, invited presentations, and panel sessions, as international experts present their latest findings and share experiences in network strategy, planning, operations, management, control and design. May we invite you to participate in Networks 2014.
More Information..
on 11-09-2014
Stefano Iubini, CBM-CNRS Orléans
11/09/2014, 14:00
Room P8, Mathematics Building, IST
* * * Please note exceptional day and place. * * *
Since the pioneering work of Onsager and Ramsey in the 1940s and '50s, physical states at negative (absolute) temperatures have attracted the curiosity of researchers and shown how science can challenge common sense. In negative-temperature regimes, the temperature is above infinity and high-energy states are more populated than low-energy ones.
After many years elapsed since the first experimental evidences of negative temperatures in quantum nuclear-spin systems, recent experiments have realized a negative temperature state in a system of ultracold bosons trapped in optical lattice, modeled by a Bose-Hubbard Hamiltonian.
I will discuss the statistical behavior of a semi-classical limit of the Bose-Hubbard model, namely the Discrete Nonlinear Schroedinger Equation. By monitoring the microcanonical temperature, it is possible to show that there exists a parameter region where the system evolves towards a state characterized by a finite density of spatially localized nonlinear excitations (discrete breathers) and a negative temperature. Such a state persists over very long (astronomical) times since the convergence to equilibrium becomes increasingly slower as a consequence of a coarsening process.
I will also discuss possible mechanisms for the generation of negative-temperature states in experimental setups.
Quantum Computation and Information Seminar
http://math.ist.utl.pt/seminars/qci/?action=next
Support: Phys-Info (IT), SQIG (IT), CFIF and CAMGSD, with support from FCT, FEDER and EU FP7, namely via projects PEst-OE/EEI/LA0008/2013, CQVibes, Landauer (GA 318287) and PAPETS (323901).
More Information..