Functional Methods in Stochastic Systems

Field-theoretic construction of functional representations of solutions of stochastic differential equations and master equations is reviewed. A generic expression for the generating function of Green functions of stochastic systems is put forward. Relation of ambiguities in stochastic differential equations and in the functional representations is discussed. Ordinary differential equations for expectation values and correlation functions are inferred with the aid of a variational approach.Comment: Plenary talk presented at Mathematical Modeling and Computational Science. International Conference, MMCP 2011, Star\'a Lesn\'a, Slovakia, July 4-8, 201

Stochastic magnetohydrodynamic turbulence in space dimensions d≥2d\ge 2

Interplay of kinematic and magnetic forcing in a model of a conducting fluid with randomly driven magnetohydrodynamic equations has been studied in space dimensions $d\ge 2$ by means of the renormalization group. A perturbative expansion scheme, parameters of which are the deviation of the spatial dimension from two and the deviation of the exponent of the powerlike correlation function of random forcing from its critical value, has been used in one-loop approximation. Additional divergences have been taken into account which arise at two dimensions and have been inconsistently treated in earlier investigations of the model. It is shown that in spite of the additional divergences the kinetic fixed point associated with the Kolmogorov scaling regime remains stable for all space dimensions $d\ge 2$ for rapidly enough falling off correlations of the magnetic forcing. A scaling regime driven by thermal fluctuations of the velocity field has been identified and analyzed. The absence of a scaling regime near two dimensions driven by the fluctuations of the magnetic field has been confirmed. A new renormalization scheme has been put forward and numerically investigated to interpolate between the $\epsilon$ expansion and the double expansion.Comment: 12 pages, 4 figure

Reaction, Levy Flights, and Quenched Disorder

We consider the A + A --> emptyset reaction, where the transport of the particles is given by Levy flights in a quenched random potential. With a common literature model of the disorder, the random potential can only increase the rate of reaction. With a model of the disorder that obeys detailed balance, however, the rate of reaction initially increases and then decreases as a function of the disorder strength. The physical behavior obtained with this second model is in accord with that for reactive turbulent flow, indicating that Levy flight statistics can model aspects of turbulent fluid transport.Comment: 6 pages, 5 pages. Phys. Rev. E. 65 (2002) 011109--1-

Work ability meetings-a survey of Finnish occupational physicians

Background Work ability meetings (WAMs) are planned discussions between an employee, a manager and an occupational physician (OP) to support work ability and return to work (RTW). During the last decade, WAMs become a popular intervention in Finnish occupational healthcare, although research on their content is lacking. Aims To describe the practice of WAMs in Finland. Methods We sent an internet survey by e-mail to members of the Finnish Society of Occupational Health Physicians in August 2014. We asked them to describe the last WAM they had attended, the employee the meeting concerned, the reason why it was convened, the content of the meeting and the action plan developed. Results A total of 303 of 1304 OPs responded (24%) to the survey. The meetings were most often arranged for employees in manual or clerical work (71%). There were several overlapping reasons for convening a WAM, including a worker's reduced work ability (57%), functional ability (42%) or long-term sickness absence (38%). The meetings consisted of RTW planning, clarification of the situation and a dialogue between the three parties. In half of the cases, the action plans dealt with modifications of work tasks. A third of cases were forwarded to vocational rehabilitation, while permanent disability pension was considered in 6% of cases. Conclusions The focus of WAMs was on workplace adjustments to support workers to remain at work. The WAMs dealt mostly with early interventions for RTW: work modifications, adjustments and vocational rehabilitation.Peer reviewe