International Journal of Modern Physics A

Electroweak data from the high energy electron–positron and proton–antiproton colliders are reviewed. On the whole the data is consistent with and supports the predictions of the electroweak theory. However, a crucial prediction of the theory remains to be verified: the existence of the Higgs boson and its light mass, less than 193 GeV, obtained from a fit to all the data within the electroweak framework. The lower limit on its mass from direct searches being 114 GeV, the mass of the Higgs is fixed within a narrow range which is expected to be explored at the Fermilab Tevatron experiments or later at the Large Hadron Collider at CERN.

The effects of charge independence breaking of nucleon–nucleon interaction on the bulk properties of nuclear matter are investigated. Our results indicate that at high densities, the inclusion of charge dependence in the nucleon–nucleon potential affects the bulk properties of nuclear matter. However, at low densities, this effect is not considerable. It is seen that the change of our results for the nuclear matter calculations due to the breaking of the charge independence increases by increasing density. It is shown that the energy contribution of the ¹S₀ channel is sensitive to considering the charge dependence in the nucleon–nucleon interaction. It is indicated that the effects of charge independence breaking on the calculated equation of state of nuclear matter can be ignored.

We derive and generalize the RR twisted tadpole cancellation conditions necessary to obtain consistent D=4, Z_N orbifold compactifications of Type IIB string theory. At least two different types of branes (or antibranes with opposite RR charges) are introduced into the construction. The matter spectra and their contribution to the non-Abelian gauge anomalies are computed. Their relation with the tadpole cancellation conditions is also reviewed. The presence of tachyons is a common feature for some of the nonsupersymmetric systems of branes.

We consider the renormalization of theories with many scalar fields. We discuss at the one-loop level some simple, non-gauge models with an arbitrary number of scalars and fermions both in mass-shell and MS schemes. In the MS scheme we give a detailed qualitative analysis of the RG flow of dimensionless couplings in flavor space.

Acoustic analogues of black holes (dumb holes) are generated when a supersonic fluid flow entrains sound waves and forms a trapped region from which sound cannot escape. The surface of no return, the acoustic horizon, is qualitatively very similar to the event horizon of a general relativity black hole. In particular Hawking radiation (a thermal bath of phonons with temperature proportional to the "surface gravity") is expected to occur. In this note we consider quasi-one-dimensional supersonic flow of a Bose–Einstein condensate (BEC) in a Laval nozzle (converging-diverging nozzle), with a view to finding which experimental settings could magnify this effect and provide an observable signal. We discuss constraints and problems for our model and identify the issues that should be addressed in the near future in order to set up an experiment. In particular we identify an experimentally plausible configuration with a Hawking temperature of order 70 n K; to be contrasted with a condensation temperature of the order of 90 n K.