Comment on "Feynman Effective Classical Potential in the Schrodinger Formulation"

We comment on the paper "Feynman Effective Classical Potential in the Schrodinger Formulation"[Phys. Rev. Lett. 81, 3303 (1998)]. We show that the results in this paper about the time evolution of a wave packet in a double well potential can be properly explained by resorting to a variational principle for the effective action. A way to improve on these results is also discussed.Comment: 1 page, 2eps figures, Revte

Leachate analyses of volcanic ashes from Stromboli volcano: A proxy for the volcanic gas plume composition?

Many volcanoes show a change in chemical composition of the gas phase prior to periods of eruptive activity. Fine‐grained tephra erupted from active vents and transported through volcanic plumes can adsorb, and therefore rapidly scavenge, volatile elements such as sulfur, halogens, and metal species in the form of soluble salts adhering to ash surfaces. Analysis of such water‐soluble surface materials is a suitable supplement for remote monitoring of volcanic gases at inaccessible volcanoes. In this work, ash samples of the 2004 to 2009 eruptive activity of Stromboli volcano were sampled, leached, and analyzed for major and trace elements. Data analysis and interpretation was focused on determining the relationship between chemical composition of water‐soluble components adhering to volcanic ash and the volcano’s activity state. First results show significant temporal variations in ash leachate compositions, reflecting changes in the eruptive style of the volcano. In particular, we reveal that ash leachates S/F and Mg/Na ratios showed marked increases prior to a large‐scale explosion on 15 March 2007.PublishedD172041.2. TTC - Sorveglianza geochimica delle aree vulcaniche attiveJCR Journalreserve

Effective action and the quantum equation of motion

We carefully analyse the use of the effective action in dynamical problems, in particular the conditions under which the equation \frac{\delta \Ga} {\delta \phi}=0 can be used as a quantum equation of motion, and the relation between the asymptotic states involved in the definition of \Ga and the initial state of the system. By considering the quantum mechanical example of a double-well potential, where we can get exact results for the time evolution of the system, we show that an approximation to the effective potential in the quantum equation of motion that correctly describes the dynamical evolution of the system is obtained with the help of the wilsonian RG equation (already at the lowest order of the derivative expansion), while the commonly used one-loop effective potential fails to reproduce the exact results.Comment: 28 pages, 13 figures. Revised version to appear in The European Physical Journal