Atomic parity violation and the HERA anomaly

We show that the two scenarios able to explain the HERA anomaly --- a new leptoquark coupling or a new contact interaction --- predict new contributions to atomic parity violation. These corrections are sufficiently large and different that a feasible reduction in the dominant atomic theory uncertainty could give some hint in favour of one of the two scenarios.Comment: 4 pages. Reference added, PDG value of weak charge revise

Frequency-splitting estimators of single-propagator traces

Single-propagator traces are the most elementary fermion Wick contractions which occur in numerical lattice QCD, and are usually computed by introducing random-noise estimators to profit from volume averaging. The additional contribution to the variance induced by the random noise is typically orders of magnitude larger than the one due to the gauge field. We propose a new family of stochastic estimators of single-propagator traces built upon a frequency splitting combined with a hopping expansion of the quark propagator, and test their efficiency in two-flavour QCD with pions as light as 190 MeV. Depending on the fermion bilinear considered, the cost of computing these diagrams is reduced by one to two orders of magnitude or more with respect to standard random-noise estimators. As two concrete examples of physics applications, we compute the disconnected contributions to correlation functions of two vector currents in the isosinglet omega channel and to the hadronic vacuum polarization relevant for the muon anomalous magnetic moment. In both cases, estimators with variances dominated by the gauge noise are computed with a modest numerical effort. Theory suggests large gains for disconnected three and higher point correlation functions as well. The frequency-splitting estimators and their split-even components are directly applicable to the newly proposed multi-level integration in the presence of fermions.Comment: 26 pages, 8 figures, LaTe

A Fast Learning Algorithm for Image Segmentation with Max-Pooling Convolutional Networks

We present a fast algorithm for training MaxPooling Convolutional Networks to segment images. This type of network yields record-breaking performance in a variety of tasks, but is normally trained on a computationally expensive patch-by-patch basis. Our new method processes each training image in a single pass, which is vastly more efficient. We validate the approach in different scenarios and report a 1500-fold speed-up. In an application to automated steel defect detection and segmentation, we obtain excellent performance with short training times

Learning Ground Traversability from Simulations

Mobile ground robots operating on unstructured terrain must predict which areas of the environment they are able to pass in order to plan feasible paths. We address traversability estimation as a heightmap classification problem: we build a convolutional neural network that, given an image representing the heightmap of a terrain patch, predicts whether the robot will be able to traverse such patch from left to right. The classifier is trained for a specific robot model (wheeled, tracked, legged, snake-like) using simulation data on procedurally generated training terrains; the trained classifier can be applied to unseen large heightmaps to yield oriented traversability maps, and then plan traversable paths. We extensively evaluate the approach in simulation on six real-world elevation datasets, and run a real-robot validation in one indoor and one outdoor environment.Comment: Webpage: http://romarcg.xyz/traversability_estimation

Exotic atoms at extremely high magnetic fields: the case of neutron star atmosphere

The presence of exotic states of matter in neutron stars (NSs) is currently an open issue in physics. The appearance of muons, kaons, hyperons, and other exotic particles in the inner regions of the NS, favored by energetic considerations, is considered to be an effective mechanism to soften the equation of state (EoS). In the so-called two-families scenario, the softening of the EoS allows for NSs characterized by very small radii, which become unstable and convert into a quark stars (QSs). In the process of conversion of a NS into a QS material can be ablated by neutrinos from the surface of the star. Not only neutron-rich nuclei, but also more exotic material, such as hypernuclei or deconfined quarks, could be ejected into the atmosphere. In the NS atmosphere, atoms like H, He, and C should exist, and attempts to model the NS thermal emission taking into account their presence, with spectra modified by the extreme magnetic fields, have been done. However, exotic atoms, like muonic hydrogen $(p\,\mu^-)$ or the so-called Sigmium $(\Sigma^+\,e^-)$, could also be present during the conversion process or in its immediate aftermath. At present, analytical expressions of the wave functions and eigenvalues for these atoms have been calculated only for H. In this work, we extend the existing solutions and parametrizations to the exotic atoms $(p\,\mu^-)$ and $(\Sigma^+\,e^-)$, making some predictions on possible transitions. Their detection in the spectra of NS would provide experimental evidence for the existence of hyperons in the interior of these stars.Comment: 10 pages, 6 figures, proceedings of the "International Conference on Exotic Atoms and Related Topics - EXA2017", Austrian Academy of Sciences, Austria, September 11-15, 201

Challenges of tsunami and conflict affected rural water supply in Sri Lanka

The water supply of the rural coastal areas in Sri Lanka is provided by private open dug wells, most of which have been flooded by sea water during the tsunami. The salinity of the well affected proved not to be the main problem, and early attempts to rehabilitate wells failed. Salinity reduction can only be achieved naturally, through the recharge of the aquifer. The true challenge for rural water supply is represented by bacteriological and agricultural contamination and sustainability of handpumps. Constructing back better means also an exit strategy from water trucking that does not focus on salinity, but introduces a new water quality awareness, and new water purification solutions, to the users. A lesson learned: in case of tsunami, do not try to rehabilitate the well, just wait for the rainy season

Ein nichtlineares Modell für das dynamische Verhalten von schwimmenden Offshore-Fundamenten

Among the renewable energies, the exploitation of offshore wind energy in deep waters is becoming more and more important, and it is expected to increase even more because of the intrinsic potential and the large availability of this resource. Deep-water wind turbines are usually installed over moored floating supports. Their dynamics depends on the complex interaction between the system and the environment making the use of numerical models almost inevitable for the design and optimization of such structures. In this context, a nonlinear model for the dynamics of moored floating platforms is developed. The dynamic problem of the platform is formulated in the framework of the dynamics of rigid bodies, referring to the mixed representation of the motion, which consists in the simultaneous use of two different bases. The formulation is developed for a wide range of loads (forces and torques) with particular attention to the transformations of the state variables. Both follower and non-follower loads are considered. The differential problem is solved with a recently developed time integration algorithm that considers the Lie group structure of the configuration space overcoming some critical aspects associated with the typical use of nautical angles and their time derivatives. The resulting formulation is very general and in principle can be exploited for the study of every system modelled as a rigid body, such as ships and hulls. The developed dynamic solver can be coupled with other models to study specific problems. In this work the assessment of the loads related to both the mooring system and the hydrodynamic action is addressed. In particular, mooring lines are modelled by means of a quasi-static formulation, whereas wave loads are evaluated with the linear hydrodynamic theory. In general, both the formulations guarantee a satisfying level of accuracy, even though in some specific cases the inertia and damping of the mooring lines as well as higher-order hydrodynamic terms should be included to improve the reliability of the model. The numerical model is tested against a number of dynamic problems for which the exact analytic solution is known, allowing a detailed assessment of the capabilities of the method. The dynamics of moored floating platforms is then investigated discussing the effect of different strategies of simulation on the system response and the role of the main parameters affecting the motion.Die Bedeutung von Offshore-Windenergie unter den erneuerbaren Energieträgern nimmt momentan stark zu und weitere Zuwächse werden aufgrund der weiten Verfügbarkeit dieser Energiequelle und ihres intrinsischen Potenzials erwartet. Windkraftanlagen in Tiefwasser werden normalerweise mittels schwimmenden Offshore-Fundamenten am Meeresboden verankert. Ihr dynamisches Verhalten hängt von der komplexen Interaktion zwischen dem System und der Umgebung ab, weshalb numerische Modelle unerlässlich für die Entwicklung und Optimierung solcher Strukturen sind. Daher wird ein nichtlineares Modell zur Beschreibung des dynamischen Verhaltens von schwimmenden Offshore-Fundamenten vorgestellt. Dafür wird ein analytischer Ansatz aus dem Bereich der Dynamik starrer Körper unter Verwendung einer gemischten Darstellung der Bewegung entwickelt. Dieser Ansatz berücksichtigt eine große Bandbreite an Belastungen (Kräfte und Momente) unter Beachtung der Transformation der Zustandsvariablen. Dabei werden sowohl Lasten mit raumfesten als auch mit veränderlichen Wirkrichtungen berücksichtigt. Die Lösung des Differentialgleichungssystems erfolgt mittels eines Zeitintegrationsverfahrens, das die Struktur der Lie-Gruppe des betrachteten Raumes berücksichtigt und eine Vereinfachung in Bezug auf die allgemein verwendeten Eulerschen Winkel darstellt. Der resultierende Ansatz ist allgemeingültig und kann prinzipiell auf jedes beliebige, als starrer Körper modellierte System angewendet werden. Der dynamische Gleichungslöser wird mit zusätzlichen Modellen zur Ermittlung der, von der Verankerung verursachten, Reaktionskräfte und -momente und der Beanspruchung durch hydrodynamische Lasten gekoppelt. Dabei werden die Ankertrossen mittels eines quasi-statischen Ansatzes modelliert und die Belastung durch Wellen wird nach der linearen hydrodynamischen Theorie bestimmt. Generell liefern beide Ansätze eine hohe Genauigkeit, in einigen Spezialfällen sollten die Massenträgheit und Dämpfung der Verankerung sowie hydrodynamische Terme höherer Ordnung zur Verbesserung des Modells berücksichtigt werden. Das numerische Modell wird anhand einer Reihe dynamischer Problemstellungen mit exakten, analytischen Lösungen validiert, wodurch die allgemeingültige Anwendbarkeit der Methode belegt wird. Abschließend wird das dynamische Verhalten von schwimmenden Offshore-Fundamenten hinsichtlich verschiedener Simulationsstrategien und des Einflusses der Hauptparameter auf die Bewegung untersucht

Resistenza di travi in cemento armato deteriorate dalla corrosione: confronto fra risultati sperimentali e teorici

La valutazione della resistenza di strutture in cemento armato dipende principalmente dalle proprietà dei materiali, dalla geometria e dalle incertezze legate al modello applicato. La corrosione delle armature è generalmente considerata la principale causa del deterioramento di tali strutture e può influire sia sul comportamento allo stato limite ultimo sia allo stato limite di esercizio. Nella presente tesi si applicano le indicazioni per il calcolo delle incertezze di modello descritte nel Probabilistic Model Code of the Joint Committee on Structural Safety e si propone un procedimento per la valutazione di strutture in cemento armato deteriorate dalla corrosione. I parametri statistici delle incertezze dei modelli di resistenza sono stimati applicando le formulazioni dell’Eurocodice UNI-EN 1992-1-1, relativamente al calcolo della resistenza a flessione, e del Model Code 2010 e del modello sperimentale di A. Mári, relativamente al calcolo della resistenza a taglio, opportunamente modificate per tenere conto degli effetti della corrosione sulla resistenza degli elementi strutturali. Le informazioni inerenti alle proprietà dei materiali, alla geometria e all’aderenza sono state introdotte all’interno dei suddetti modelli per stabilire la residua capacità portante. Comparando i risultati teorici con quelli ottenuti a seguito di una campagna sperimentale su travi in cemento armato con armature corrose a causa dell’esposizione ad ambiente marino aggressivo durante 70 anni, sono stati individuati i modelli maggiormente affidabili, che peraltro presentano deviazioni leggermente maggiori rispetto a quelle riscontrate nel caso di strutture integre. Infine, è stata implementata una procedura generale di valutazione di strutture deteriorate che prevede l’utilizzo dei modelli di flessione e di taglio maggiormente affidabili; mediante l’applicazione di tale metodologia al campione di travi testate, è stato verificato che tale metodo permette di compiere una stima affidabile del comportamento di strutture in cemento armato degradate dalla corrosione