[en] In the field of Grand Unified Theories the SU-5 remains an attractive model. Important experimental test-points of the GUT are the Weinberg angle and the existence of proton decay. Reliable predictions of the Weinberg angle and the proton lifetime are important goals of the present work. The full symmetry of GUTs are attained at about 10¹⁵ GeV whereas presently energies of 100-1000 GeV are available experimentally. In bridging these many orders-of-magnitude in energy renormalization group equations are an important tool. Here the treatment of mass treshold is important: in the transition of low-energy limits of a broken symmetry to effective low-energy theories the results depend on the particular renormalization schemes (RS). In 1981 a gauge independent RS has been proposed by W. Kummer: it is generalized in the present work for broken gauge symmetry. In this way the unification mass, the Weinberg angle and the proton lifetime are calculated in the SU-5 to be: sin²Θ_n = 0,215±0,04, Mx = 6,72xe^±0,8centredot10¹⁴ GeV and τp = 2,3centredot10^31±2 years. Although the minimal SU-5 model could not be modified to an amount sufficient to bring agreement with the experimental proton lifetime upper limits, the present work shows that the treshold corrections are important in corresponding calculations in more realistic models. 70 refs., 6 figs. (qui)

[en] The combined analysis of the individual data from 13 European studies includes 7, 148 lung cancer patients and 14,208 controls. The database is currently the world wide largest database to investigate the association of lung cancer with residential radon. After detailed stratification for smoking, risk analyses showed an approximately linear exposure-response relationship with no evidence of a threshold dose. The excess relative risk was 16% per increase of radon exposure by 100 Bq/m³. There was a significant linear exposure-response relationship even for radon concentrations of less than 200 Bq/m³. (orig.)

[en] To evaluate the risk of cancer associated with low and high levels of radon exposure one of the largest single cohort studies on uranium miners is being conducted in Germany. It includes 58.940 men who were employed for at least 6 months between 1946 and 1989 at the former. Wismut uranium company in Eastern Germany. Information on job histories was collected from the original pay rolls. Exposures to radon and its progeny, long-lived radionuclides and gamma radiation was estimated by using a detailed job-exposure matrix. For 94% of the cohort members the vital status has been ascertained from the date of entry to 31 December 1998. For 87% of the deceased cohort members causes of death were identified. The different causes of death were compared with the age and calendar-year specific national death rates of Eastern Germany, formerly GDR. Standardized mortality ratios (SMR) with 95% confidence limits (CI) were calculated. The total number of person-years under observation was 1,795, 195, with a mean duration of follow-up of 30 years. In this period a total of 4,692 malignant cancer deaths including 2,335 lung cancer deaths occurred. The observed overall mortality in the cohort was significantly lower than that expected from national rates (SMR=0.93, 95% CI: 0.91-0.94), demonstrating a possible healthy worker effect. The SMR for lung cancer was 1.83 (95% CI: 1.76-1.91), showing a clear increase with increasing cumulative radon exposure. When other sites of cancer were considered, a non-significant excess was observed for cancers of larynx and liver. These results were consistent to the results of the joint analyses of the 11 miner cohort studies. A potential limitation of this first analysis concerns the comparison group. Therefore internal risk analyses will be performed in a next step. (Author) 26 refs

[en] Full text: I discuss the current status of string theory including applications to phenomenology and cosmology, as well as recent theoretical developments. In particular I mention the applications of holographic methods to the quark gluon plasma, the logic behind the 'Landscape' prediction and the contribution of our group to the latter. I also comment on recent discussions in the media on alternative attempts to cope with quantum gravity. (author)

[en] We give a complete classification of all simple current modular invariants, extending previous results for (Z_p)^k to arbitrary centers. We obtain a simple explicit formula for the most general case. Using orbifold techniques to this end, we find a one-to-one correspondence between simple current invariants and subgroups of the center with discrete torsions. As a by-product, we prove the conjectured monodromy independence of the total number of such invariants. The orbifold approach works in a straightforward way for symmetries of odd order, but some modifications are required to deal with symmetries of even order. With these modifications the orbifold construction with discrete torsion is complete within the class of simple current invariants. Surprisingly, there are cases where discrete torsion is a necessity rather than a possibility. (orig.)

[en] In epidemiologic studies on lung cancer risk due to indoor radon the quantification of individual radon exposure over a long time period is one of the main issues. Therefore, radon measurements in one or more dwellings, which in total have been inhabited by the participants for a sufficient time-period, are necessary as well as consideration of changes of building characteristics and ventilation habits, which influence radon concentration. Given data on 1-y alpha-track measurements and personal information from 6,000 participants of case-control studies in West and East Germany, and improved method is developed to assess individual radon exposure histories. Times spent in different rooms of the dwelling, which are known from a personal questionnaire, are taken into account. The time spent outside the house varies substantially among the participants. Therefore, assuming a substantially lower radon exposure outside the dwelling, the residence time constitutes an important aspect of total radon exposure. By means of an analysis of variance, important determinants of indoor radon are identified, namely constant conditions such as type of house, type of construction, year of construction, floor and type of basement, and changeable conditions such as heating system, window insulation, and airing habits. A correction of measurements in former dwellings by factors derived from the analysis is applied if current living conditions differ from those of the participants at the time when they were living in the particular dwellings. In rare cases the adjustment for changes leads to a correction of the measurements with a factor of about 1.4, but a reduction of 5% on average only. Exposure assessment can be improved by considering time at home and changes of building and ventilation conditions that affect radon concentration. The major concern that changes in ventilation habits and building conditions lead to substantial errors in exposure assessment cannot be confirmed in the data analyzed

[en] Background independence of noncommutative Yang-Mills theory on R-circumflex n is discussed. The quantity theta vertical bar hatF vertical bar theta- vertical bar theta is found to be background dependent at subleading order, and it becomes background independent only when the ordinary gauge field strength F is constant. It is shown that, at small values of B, the noncommutative Dirac-Born-Infeld action possesses Lambda-symmetry at least to subleading order in theta if F damps fast enough at infinity. (author)

[en] We calculate the cohomology of the BRS operator s modulo an auxiliary differential operator t where both operators act on invariant polynomials in anticommuting variables Cⁱ and commuting variables Xⁱ. Cⁱ and Xⁱ transform according to the adjoint representation of the Lie algebra of a compact Lie group. The cohomology classes of s modulo t are related to the solutions of the consistency equations which have to be satisfied by anomalies of Yang-Mills theories. The present investigation completes the proof of the completeness and nontriviality of these solutions and, as a by-product, determines the cohomology of the underlying Lie algebra. (orig.)

[en] Short communication

[en] The non-commutative product of deformation quantization can be derived from string theory in a topological limit where the space-time metric is small as compared to the anti-symmetric B-field (the ancestor of the Poisson bi-vector). In terms of string physics the non-commutative product thus amounts to a summation of the leading B-field contributions to the effective action. In the (non-symplectic) Poisson case this interpretation is spoiled, however, by the absence of a canonical measure. For general string backgrounds associativity is lost, but the Born-Infeld action provides a canonical measure. We show that the concept of effective actions does not require associativity, but rather cyclicity, i.e. commutativity and associativity up to surface terms. Cyclicity thus implies a compatibility condition between the star product and the measure, which for Born-Infeld turns out to be equivalent to the generalized Maxwell equation for the gauge field on the D-brane. We show that cyclicity requires a gauge modification of the Kontsevich product at second derivative order in a derivative expansion and we discuss the physics related to these mathematical structures. (author)