The production of a non-homogeneous classical pion field and the distribution of the neutral and charged pions

The probability distribution $dw/df$ as a function of the ratio $f=n_0/n_{tot}$ of the neutral to total multiplicities is calculated for the classical pion fields quickly varying in space and time.Comment: 6 pages, 1 .eps figure, using epsfig, submitted to Phys.Let

Barriers to exporting: Firm-Level Evidence from Germany

Recent literature stresses the importance of low productivity as a barrier to the international expansion of firms. But financial frictions or adverse employment conditions at home could matter as well. In this paper, we present new empirical evidence on the importance of these factors. We use a detailed micro-level dataset of German firms which simultaneously provides information on exports, financial frictions, and labor market conditions. Our paper has three main findings. First, in line with earlier literature, we find a positive impact of size and productivity on firms’ export activities. Second, financial constraints affect the entry into foreign market (extensive margin) more than the volume of exports (intensive margin). Third, labor market conditions have a mixed impact on export activities. The most consistent finding is that firms covered by collective bargaining agreements are less likely to be exporters and export less.multinational firms, exports, firm heterogeneity, productivity

Firm-Specific Factor Market Constraints and FDI: Evidence from Germany

Firms that invest abroad are large and more productive than their domestic counterparts. But to what extent are the international activities of firms also driven by differences across firms in terms of their access to external finance and the labor market conditions that there are facing? In this paper, we present new empirical evidence based on a detailed micro-level dataset of German firms. Our paper has three main findings regarding the firm-level determinants of FDI. First, in line with earlier literature, we find a positive impact of size, productivity, and R&D activity on firms’ FDI activity. Second, labor market conditions have a mixed impact on FDI. Personnel shortage tends to have a significantly positive impact on the probability to invest abroad, whereas wage cost problems and the existence of collective bargaining agreements have a negative effect. Third, financial constraints have a mixed impact as well. While self-reported financial constraints do not significantly affect FDI activity, cash flow has a positive impact.multinational firms, firm heterogeneity, productivity, financial constraints, labor market constraints

Non-Central Heavy-Ion Collisions are the Place to Look for DCC

We give two reasons why we believe that non-central ultrarelativistic heavy ion collisions are the place to look for the disoriented chiral condensates (DCC). First, we argue that the most probable quench scenario for the formation of DCC requires non-central collisions. Second, we show by numerical simulations that strong electromagnetic fields of heavy ions can exert a surprisingly large effect on the DCC domain formation through the chiral anomaly. The effect again requires non-central collisions. Interestingly, the result of simulations is consistent with the formation of correlated two domains of the chiral condensate, which are aligned in space, perpendicular to the scattering plane, but misaligned in isospin space.Comment: 4 pages (Latex), 3 embedded ps figures, espcrc1 style, talk given at Quark Matter 97, December 97, Tsukuba, Japa

Lul·lisme a Montserrat al segle XVè

Abstract not availabl

Multiphonon anharmonic decay of a quantum mode

A nonperturbative theory of multiphonon anharmonic transitions between energy levels of a local mode is presented. It is shown that the rate of transitions rearranges near the critical level number $n_{cr}$: at smaller $n$ the process slows down, while at larger $n$ it accelerates in time, causing a jump-like loss of energy followed by the generation of phonon bursts. Depending on parameters, phonons are emitted in pairs, triplets etc.Comment: submitted to Europhys.Let

Driving defect modes of Bose-Einstein condensates in optical lattices

We present an approximate analytical theory and direct numerical computation of defect modes of a Bose-Einstein condensate loaded in an optical lattice and subject to an additional localized (defect) potential. Some of the modes are found to be remarkably stable and can be driven along the lattice by means of a defect moving following a step-like function defined by the period of Josephson oscillations and the macroscopic stability of the atoms.Comment: 4 pages, 5 figure

Multi-lepton Signatures of a Hidden Sector in Rare B Decays

We explore the sensitivity of flavour changing b -> s transitions to a (sub-)GeV hidden sector with generic couplings to the Standard Model through the Higgs, vector and axion portals. The underlying two-body decays of B mesons, B -> X_s S and B0 -> SS, where S denotes a generic new GeV-scale particle, may significantly enhance the yield of monochromatic lepton pairs in the final state via prompt decays of S to a dilepton pair. Existing measurements of the charged lepton spectrum in neutral-current semileptonic B decays provide bounds on the parameters of the light sector that are significantly more stringent than the requirements of naturalness. New search modes, such as B -> X_s + n(l+l-) and B0 -> n(l+l-) with n > 1 can provide additional sensitivity to scenarios in which both the Higgs and vector portals are active, and are accessible to (super-)B factories and hadron colliders.Comment: 12 pages, 2 figures; v2: reference added, minor correction