Long-range magnetic fields in the ground state of the Standard Model plasma

In thermal equilibrium the ground state of the plasma of Standard Model particles is determined by temperature and exactly conserved combinations of baryon and lepton numbers. We show that at non-zero values of the global charges a translation invariant and homogeneous state of the plasma becomes unstable and the system transits into a new state, containing a large-scale magnetic field. The origin of this effect is the parity-breaking character of weak interactions and chiral anomaly. This situation can occur in the early Universe and may play an important role in its subsequent evolution.Comment: 6 pages. Comments are welcom

Topological Field Theory Interpretation of String Topology

The string bracket introduced by Chas and Sullivan [math.GT/9911159] is reinterpreted from the point of view of topological field theories in the Batalin-Vilkovisky or BRST formalisms. Namely, topological action functionals for gauge fields (generalizing Chern-Simons and BF theories) are considered together with generalized Wilson loops. The latter generate a (Poisson or Gerstenhaber) algebra of functionals with values in the $S^1$-equivariant cohomology of the loop space of the manifold on which the theory is defined. It is proved that, in the case of $GL_n$ with standard representation, the (Poisson or BV) bracket of two generalized Wilson loops applied to two cycles is the same as the generalized Wilson loop applied to the string bracket of the cycles. Generalizations to other groups are briefly described.Comment: 27 pages, 2 figure

Modelling DNA Response to THz Radiation

Collective response of DNA to THz electric fields is studied in a simple pair bond model. We confirm, with some caveats, a previous observation of destabilising DNA breather modes and explore the parameter-dependence of these modes. It is shown that breather modes are eliminated under reasonable physical conditions and that thermal effects are significant.Comment: 6 pages, 3 figures. version to appear in Phys. Rev.

Sympathetic cooling of 4^4He+^+ ions in a radiofrequency trap

We have generated Coulomb crystals of ultracold $^4$He$^+$ ions in a linear radiofrequency trap, by sympathetic cooling via laser--cooled $^9$Be$^+$. Stable crystals containing up to 150 localized He$^+$ ions at $\sim$20 mK were obtained. Ensembles or single ultracold He$^+$ ions open up interesting perspectives for performing precision tests of QED and measurements of nuclear radii. The present work also indicates the feasibility of cooling and crystallizing highly charged atomic ions using $^9$Be$^+$ as coolant.Comment: 4 pages, 2 figure

Spin - or, actually: Spin and Quantum Statistics

The history of the discovery of electron spin and the Pauli principle and the mathematics of spin and quantum statistics are reviewed. Pauli's theory of the spinning electron and some of its many applications in mathematics and physics are considered in more detail. The role of the fact that the tree-level gyromagnetic factor of the electron has the value g = 2 in an analysis of stability (and instability) of matter in arbitrary external magnetic fields is highlighted. Radiative corrections and precision measurements of g are reviewed. The general connection between spin and statistics, the CPT theorem and the theory of braid statistics are described.Comment: 50 pages, no figures, seminar on "spin

Adaiabtic theorems and reversible isothermal processes

Isothermal processes of a finitely extended, driven quantum system in contact with an infinite heat bath are studied from the point of view of quantum statistical mechanics. Notions like heat flux, work and entropy are defined for trajectories of states close to, but distinct from states of joint thermal equilibrium. A theorem characterizing reversible isothermal processes as quasi-static processes (''isothermal theorem'') is described. Corollaries concerning the changes of entropy and free energy in reversible isothermal processes and on the 0th law of thermodynamics are outlined

Stochastically positive structures on Weyl algebras. The case of quasi-free states

We consider quasi-free stochastically positive ground and thermal states on Weyl algebras in Euclidean time formulation. In particular, we obtain a new derivation of a general form of thermal quasi-free state and give conditions when such state is stochastically positive i.e. when it defines periodic stochastic process with respect to Euclidean time, so called thermal process. Then we show that thermal process completely determines modular structure canonically associated with quasi-free state on Weyl algebra. We discuss a variety of examples connected with free field theories on globally hyperbolic stationary space-times and models of quantum statistical mechanics.Comment: 46 pages, amste