Worldline Green Functions for Multiloop Diagrams

We propose a multiloop generalization of the Bern-Kosower formalism, based on Strassler's approach of evaluating worldline path integrals by worldline Green functions. Those Green functions are explicitly constructed for the basic two-loop graph, and for a loop with an arbitrary number of propagator insertions. For scalar and abelian gauge theories, the resulting integral representations allow to combine whole classes of Feynman diagrams into compact expressions.Comment: 12 pages, uuencoded compressed ps-file, HD-THEP-94-

Large N limit of orbifold field theories

We consider certain orbifoldization of the ${\cal N}=4$ field theories that leads to ${\cal N}=2,1,0$ field theories in 4 dimensions. These theories were recently analyzed using the string theory perturbation technique. It was found that in the large $N$ limit all correlation functions of the orbifold theories coincide with those of ${\cal N}=4$, modulo the rescaling of the gauge coupling constant. In this paper we repeat the same analysis using the field theoretical language.Comment: 12 pages, 3 figures, harvmac. Minor change

Exact Combinatorics of Bern-Kosower-type Amplitudes for Two-Loop Φ3\Phi^3 Theory

Counting the contribution rate of a world-line formula to Feynman diagrams in $\phi^3$ theory, we explain the idea how to determine precise combinatorics of Bern-Kosower-like amplitudes derived from a bosonic string theory for $N$-point two-loop Feynman amplitudes. In this connection we also present a method to derive simple and compact world-line forms for the effective action.Comment: 26 pages, two figures by picte

On the Calculation of Effective Actions by String Methods

Strassler's formulation of the string-derived Bern-Kosower formalism is reconsidered with particular emphasis on effective actions and form factors. Two- and three point form factors in the nonabelian effective action are calculated and compared with those obtained in the heat kernel approach of Barvinsky, Vilkovisky et al. We discuss the Fock-Schwinger gauge and propose a manifestly covariant calculational scheme for one-loop effective actions in gauge theory.Comment: 12 pages, Plain TEX, HD-THEP-93-2

Fixed-term employment, work organization and job satisfaction: Evidence from German individual-level data

The present paper examines the joint effect of fixed-term employment and work organization on job satisfaction using individual-level data from the German Socio-Economic Panel (GSOEP). Specifically, we analyze whether workers who are heterogeneous in terms of the type of working contract (fixed-term vs. permanent) do also differ with regard to job satisfaction, when they perform under comparable work organizational conditions. Such information would be quite valuable for employers, because they can learn about the responsiveness of heterogeneous workers to innovative work organizational practices. For this purpose, we at first estimate a linear fixed effects model, thereby controlling for unobserved time-constant characteristics. In a second step, we account for potential remaining endogeneity by combining the fixed effects approach with a two-stage estimation strategy. Our empirical results show that in terms of job satisfaction fixed-term workers and their permanent counterparts respond differently to a number of organizational practices including task diversity, employee involvement, social relations at work, general working conditions, and career prospects. The results may be used by employers to improve their concept of diversity management and specifically the job design of heterogeneous workers.Fixed-term employment, permanent employment, job satisfaction, work organization, selectivity bias, unobserved heterogeneity

Manifesting enhanced cancellations in supergravity: integrands versus integrals

Examples of "enhanced ultraviolet cancellations" with no known standard-symmetry explanation have been found in a variety of supergravity theories. By examining one- and two-loop examples in four- and five-dimensional half-maximal supergravity, we argue that enhanced cancellations in general cannot be exhibited prior to integration. In light of this, we explore reorganizations of integrands into parts that are manifestly finite and parts that have poor power counting but integrate to zero due to integral identities. At two loops we find that in the large loop-momentum limit the required integral identities follow from Lorentz and SL(2) relabeling symmetry. We carry out a nontrivial check at four loops showing that the identities generated in this way are a complete set. We propose that at $L$ loops the combination of Lorentz and SL($L$) symmetry is sufficient for displaying enhanced cancellations when they happen, whenever the theory is known to be ultraviolet finite up to $(L-1)$ loops.Comment: 28 pages, 5 figure

World-line approach to the Bern-Kosower formalism in two-loop Yang-Mills theory

Based on the world-line formalism with a sewing method, we derive the Yang-Mills effective action in a form useful to generate the Bern-Kosower-type master formulae for gluon scattering amplitudes at the two-loop level. It is shown that four-gluon ($\Phi^4$ type sewing) contributions can be encapsulated in the action with three-gluon ($\Phi^3$ type) vertices only, the total action thus becoming a simple expression. We then derive a general formula for a two-loop Euler-Heisenberg type action in a pseudo-abelian $su(2)$ background. The ghost loop and fermion loop cases are also studied.Comment: 37(+1) pages, details added for section