Primordial Magnetic Fields from Out of Equilibrium Cosmological Phase Transitions

The universe cools down monotonically following its expansion.This generates a sequence of phase transitions. If a second order phase transition happens during the radiation dominated era with a charged order parameter, spinodal unstabilities generate large numbers of charged particles. These particles hence produce magnetic fields.We use out of equilibrium field theory methods to study the dynamics in a mean field or large N setup.The dynamics after the transition features two distinct stages: a spinodal regime dominated by linear long wave length instabilities, and a scaling stage in which the non-linearities and backreaction of the scalar fields are dominant. This second stage describes the growth of horizon sized domains. We implement a formulation based on the non equilibrium Schwinger-Dyson equations to obtain the spectrum of magnetic fields that includes the dissipative effects of the plasma. We find that large scale magnetogenesis is efficient during the scaling regime. Charged scalar field fluctuations with wavelengths of the order of the Hubble radius induce large scale magnetogenesis via loop effects.The leading processes are:pair production, pair annihilation and low energy bremsstrahlung, these processes while forbidden in equilibrium are allowed strongly out of equilibrium. The ratio between the energy density on scales larger than L and that in the background radiation r(L,T)= rho_B(L,T)/rho_{cmb}(T) is r(L,T) ~ 10^{-34} at the Electroweak scale and r(L,T) ~ 10^{-14} at the QCD scale for L sim 1 Mpc. The resulting spectrum is insensitive to the magnetic diffusion length and equipartition between electric and magnetic fields does not hold. We conjecture that a similar mechanism could be operative after the QCD chiral phase transition.Comment: 11 pages, no figures. Lecture given at the International Conference Magnetic Fields in the Universe, Angra dos Reis, Brazil, November, 200

Web based system architecture for long pulse remote experimentation

Remote experimentation (RE) methods will be essential in next generation fusion devices. Requirements for long pulse RE will be: on-line data visualization, on-line data acquisition processes monitoring and on-line data acquisition systems interactions (start, stop or set-up modifications). Note that these methods are not oriented to real-time control of fusion plant devices. INDRA Sistemas S.A., CIEMAT (Centro de Investigaciones Energéticas Medioambientales y Tecnológicas) and UPM (Universidad Politécnica de Madrid) have designed a specific software architecture for these purposes. The architecture can be supported on the BeansNet platform, whose integration with an application server provides an adequate solution to the requirements. BeansNet is a JINI based framework developed by INDRA, which makes easy the implementation of a remote experimentation model based on a Service Oriented Architecture. The new software architecture has been designed on the basis of the experience acquired in the development of an upgrade of the TJ-II remote experimentation system

Relaxing Near the Critical Point

Critical slowing down of the relaxation of the order parameter is relevant both in early the universe and in ultrarelativistic heavy ion collisions. We study the relaxation rate of the order parameter in an O(N) scalar theory near the critical point to model the non-equilibrium dynamics of critical fluctuations near the chiral phase transition.A lowest order perturbative calculation (two loops in the coupling lambda) reveals the breakdown of perturbation theory for long-wavelength fluctuations in the critical region and the emergence of a hierarchy of scales with hard q>T, semisoft T >> q >> lambda T and soft lambda T>>q loop momenta which are widely separated for weak coupling. The non-perturbative resummation in the large N limit reveals the renormalization of the interaction and the crossover to an effective 3D-theory for soft momenta.The effective 3D coupling goes to the Wilson-Fisher 3D fixed point in the soft limit.The relaxation rate of the order parameter for wave vectors lambda T >>k>> k_{us} or near the critical temperature lambda T>>m_T>>k_{us} with the ultra soft scale k_{us} = [(lambda T)/(4pi)] exp[-(4pi/lambda)] is dominated by classical semisoft loop momentum leading to Gamma(k,T) = lambda T/(2 pi N). For wavectors k<< k_{us} the damping rate is dominated by hard loop momenta and given by Gamma(k,T)=4 pi T/[3N ln(T/k)]. Analogously, for homogeneous fluctuations in the ultracritical region m_T<<k_{us} the damping rate is given by Gamma_0(m_T,T)=4 pi T/[3N ln(T/m_T)]. Thus critical slowing down emerges for ultrasoft fluctuations where the rate is lambda-independent. The strong coupling regime and the shortcomings of the quasiparticle interpretation are discussed.Comment: LaTex, 39 pages, 12 .ps figure

Detection of Spin Correlations in Optical Lattices by Light Scattering

We show that spin correlations of atoms in an optical lattice can be reconstructed by coupling the system to the light, and by measuring correlations between the emitted photons. This principle is the basis for a method to characterize states in quantum computation and simulation with optical lattices. As examples, we study the detection of spin correlations in a quantum magnetic phase, and the characterization of cluster states