On supersymmetry breaking and the Dijkgraaf-Vafa conjecture

We investigate the Dijkgraaf-Vafa proposal when supersymmetry is broken. We consider U(N) SYM with chiral adjoint matter where the coupling constants in the tree-level superpotential are promoted to chiral spurions. The holomorphic part of the low-energy glueball superpotential can still be analyzed. We compute the holomorphic supersymmetry breaking contributions using methods of the geometry underlying the N=1 effective gauge theory viewed as a Whitham system. We also study the change in the effective glueball superpotential using perturbative supergraph techniques in the presence of spurions.Comment: 24 pages, LaTeX; minor changes, one reference added, version to appear in JHE

Laser driven self-assembly of shape-controlled potassium nanoparticles in porous glass

We observe growth of shape-controlled potassium nanoparticles inside a random network of glass nanopores, exposed to low-power laser radiation. Visible laser light plays a dual role: it increases the desorption probability of potassium atoms from the inner glass walls and induces the self-assembly of metastable metallic nanoparticles along the nanopores. By probing the sample transparency and the atomic light-induced desorption flux into the vapour phase, the dynamics of both cluster formation/evaporation and atomic photo-desorption processes are characterized. Results indicate that laser light not only increases the number of nanoparticles embedded in the glass matrix but also influences their structural properties. By properly choosing the laser frequency and the illumination time, we demonstrate that it is possible to tailor the nanoparticles'shape distribution. Furthermore, a deep connection between the macroscopic behaviour of atomic desorption and light-assisted cluster formation is observed. Our results suggest new perspectives for the study of atom/surface interaction as well as an effective tool for the light-controlled reversible growth of nanostructures.Comment: 14 pages,6 figures, http://iopscience.iop.org/1612-202X/11/8/085902

First results of the two square meters multilayer glass composite mirror design proposed for the Cherenkov Telescope Array developed at INFN

The Cherenkov Telescope Array (CTA) is a future ground-based gamma-ray astronomy detector that will consist of more than 100 Imaging Atmospheric Cherenkov Telescopes of different sizes. The total reflective surface of roughly 10 000 m$^2$ requires unprecedented technological efforts towards a cost-efficient production of light-weight and reliable mirror substrates at high production rate. We report on a new mirror concept proposed for CTA developed by INFN, which is based on the replication from a spherical convex mold under low pressure. The mirror substrate is an open structure design made by thin glass layers at the mirror's front and rear interspaced by steel cylinders. A first series of nominal size mirrors has been produced, for which we discuss the optical properties in terms of radius of curvature and focusing power

The divestment-reinvestment sequence in foreign countries: The role of relational vs. transactional ownership

In this paper, we claim that ownership is a key determinant of the firms' divestment-reinvestment sequence in a foreign country. Building on the notion of ‘relational vs. transactional ownership’, we distinguish between relational-type firms (namely, family-owned and state-owned firms), and transactional-type firms (privately non-family-owned firms). We argue that relational-type firms are less likely to both divest from, and reinvest in, a given foreign country. In fact, relational owners set a lower performance threshold of intervention than transactional ones; additionally, in order to turn the tide, the former often increase resource injection when subsidiary performance falls below the threshold. Such an escalation of commitment increases sunk costs and further decreases the likelihood of divesting the subsidiary. Moreover, when a divestment occurs, the memory of high sunk costs incurred reduces the propensity to reinvest in the same host country. We test our conceptual framework on a large sample of investments, divestments and subsequent re-entries undertaken in the period 2000–2015 by 602 Italian firms. Our econometric findings corroborate our hypotheses, thus contributing to the literature on the interdependencies between divestment and reinvestment choices, and their relationships with corporate ownership

A possible solution for dinamically managing virtual environments

In modern distributed computer systems (clusters and computing GRIDs) a new class of problems, due to the increasing heterogeneity of users’ needs, have to be tackled by the administrators. One possible solution is to create ondemand virtual working environments tailored on the user’s requirements. Hence the need for an architecture to manage dynamically such environments. In this work we propose a possible solution based on the use of Virtual Machines (Xen), the implementation of a Virtual Machine Manager, capable of creation, destruction and migration of the virtualized working environments. The information will be collected using a client-server mechanism, to allow the manager to deploy preconfigured Virtual Machines on the available hardware resources. When a new execution environment became active, it is automatically recognized by the Batch System Manager and is then ready to be used

Durum wheat grain yield and quality as affected by S rate under Mediterranean conditions

The decreased inputs of S from atmospheric acidic deposition, the use of low S-containing fertilisers, and the decrease of organic matter content in soil resulted in S deficiency in many agricultural regions of the world. Sulphur fertilisation significantly affects grain yield and protein composition of cereals, thus altering the technological quality of grain. Field experiments were conducted in central Italy in two subsequent seasons to investigate the effects ofNand S application on five commercial wheat cultivarsknownto differ in yield potential and grain N content. Fertiliser treatments were two levels of N fertiliser (120 kgNha−1 and 180 kgNha−1) and three levels of S fertiliser (not applied, 60 kg S ha−1, and 120 kg S ha−1). Analyzed characters were dry weight and N and S uptake of grain and vegetative plant part, and grain quality characters. Variations in weather pattern – and especially in rainfall – between years significantly influenced grain yield and N and S content of grain, but did not affect quality parameters. Nitrogen and S application also significantly affected grain yield and the quality characteristicsW, P/L, dry gluten and SDS, although no interactive effect between treatments was observed. The highest protein content and W in grain was obtained with the combination of the highest fertiliser rates: 180 kgNha−1 and 120 kg S ha−1. Genotypes differed for yield stability between years, in that grain production was decreased in the driest year only in the varieties Claudio and Creso, but they responded similarly to N and S fertilisation. Genotypes differed also for protein concentration and quality parameters, and, on average, the varieties Duilio, Simeto and Svevo gave better performances. Differences in grain quality parameters were maintained through years, indicating that these traits are under strong genetic control