Finite-temperature chiral transition in QCD with quarks in the fundamental and adjoint representation

We study the nature of the finite-temperature chiral transition in QCD with N_f light quarks in the fundamental and adjoint representation. Universality and renormalization-group (RG) arguments show that the possibility of having a continuous transition is related to the existence of a stable fixed point (FP) in the RG flow of a 3D Landau-Ginzburg-Wilson Phi^4 theory with the same chiral symmetry-breaking pattern. The RG flow of these theories is studied by field-theoretical approaches, computing and analyzing high-order perturbative series, up to six loops. According to this RG analysis, the transition in QCD can be continuous only for N_f=2. In this case it belongs to the 3D O(4) universality class. We also find a stable FP corresponding to a 3D universality class with symmetry breaking U(2)_L x U(2)_R -> U(2)_V, which implies that the transition can be continuous also if the axial-anomaly effects are suppressed at Tc. In the case of quarks in the adjoint representation, we can have a continuous transition for N_f=1,2. For N_f=1 it belongs to the O(3) universality class. For N_f=2 it belongs to a new 3D universality class characterized by the symmetry breaking SU(4)->SO(4).Comment: 6 pages, Talk presented at Lattice 2005 (Non-zero temperature and density), Dublin, July 25-30, 200

Effective theories of finite volume QCD

Finite volume QCD close to the chiral limit cannot be described by chiral Perturbation Theory using the usual p-expansion when the correlation length of pions becomes larger than the size of the box. An alternative approach to this problem was proposed by Gasser and Leutwyler in 1987, it is referred to as $\epsilon$-expansion. In 1993 Shuryak and Verbaarschot conjectured that the spectral properties of the leading order of this alternative expansion were shared with a simpler theory called chiral Random Matrix Theory. In the following years this equivalence was widely used. In the first part of this work we prove this equivalence for any value of masses and for both zero and non-zero chemical potential. In particular the equivalence of all the low energy spectral properties imply the equivalence of the individual eigenvalue distributions, which are particularly useful to determine low energy constants from Lattice QCD with chiral fermions. In the second part, working in $\epsilon$-expansion with an accuracy up to the next to the leading order, we determine the volume and mass dependence of scalar and pseudoscalar two-point functions in $N_f$-flavour QCD, in the presence of an isospin chemical potential. Thanks to the non-vanishing chemical potential these correlation functions show a dependence on both chiral condensate and pion decay constant already at leading order

Sectoral Shifts, Diversification and Regional Unemployment: Evidence from Local Labour Systems in Italy

Using Local Labour Systems (LLSs) data, this work aims at assessing the effects of sectoral shifts and industry specialization patterns on regional unemployment in Italy over the years 2004-2008, when huge worker reallocation caused by changes in the international division of labour occurred. Italy represents an interesting case study because of the high degree of spatial heterogeneity in local labour market performance and the well-known North-South divide. Furthermore, the presence of strongly specialized LLSs (Industrial Districts, IDs) allows us to test whether IDs perform better than highly diversified urban areas thanks to the effect of agglomeration economies, or vice versa. Building on a semiparametric spatial auto-regressive framework, our empirical investigation documents that sectoral shifts and the degree of specialization exert a negative role on unemployment dynamics. By contrast, highly diversified areas turn out to be characterized by better labour market performances.unemployment, sectoral shift, diversification, spatial dependence, nonparametrics

Surgical approach to abdominal wall defects: history and new trends

AbstractWe briefly outline the history of hernia surgery development from the Ebers Papyrus to modern prosthetic repairs. The rapid evolution of anatomical, physiological and pathogenetic concepts has involved the rapid evolution of surgical treatments. From hernia sack cauterization to sack ligation, posterior wall repair (Bassini), and prosthetic reinforcement there has been an evident improvement in surgical treatment results that has stimulated surgeons to find new technical solutions over time. The introduction of prosthetic repair, the laparoscopic revolution, the impact of local anesthesia and the diffusion of day surgery have been the main advances of the last 50 years. Searching for new gold standards, the introduction of new devices has also led to new complications and problems. Research of the last 10 years has been directed to overcome prosthetic repair complications, introducing every year new meshes and materials. Lightweight meshes, composite meshes and biologic meshes are novelties of the last few years. We also take a look at future trends

A branch and bound approach for the design of decentralized supervisors in Petri net models

The paper addresses the design of compact and maximally permissive decentralized supervisors for Petri nets, based on generalized mutual exclusion constraints. Decentralization constraints are formulated with respect to the net transitions, instructing each local supervisor to detect and disable transitions of its own control site only. A solution is characterized in terms of the states it allows and its feasibility is assessed by means of two separate tests, one checking the required behavioral properties (e.g., liveness, reversibility and controllability) of the induced reachability subgraph and the other ensuring the existence of a decentralized supervisor enforcing exactly the considered set of allowed states. The second test employs an integer linear programming formulation. Maximal permissivity is ensured by efficiently exploring the solution space using a branch and bound method that operates on the reachable states. Particular emphasis is posed on the obtainment of the controllability property, both in the structural and the behavioral interpretation

The identification of wildlife-vehicle collision hotspots: Citizen science reveals spatial and temporal patterns

AbstractLinear infrastructures (e.g., roads, railways, pipelines, and powerlines) pose a serious threat to wildlife, due to the risk of wildlife-vehicle collisions (roadkills). The placement of mitigation measures, such as crossing structures, should consider species' life cycles and ecological requirements. Such an assessment would require data collection over large areas, which may be possible by employing citizen science. In this study, we aimed to identify spatio-temporal trends of roadkill occurrence using citizen science data from one of the most urbanized and biodiversity-rich regions of Italy. Temporal trends were analyzed using generalized additive models, while landscape patterns were assessed by identifying significant thresholds over land cover gradients, related to increases in relative roadkill abundance, by employing threshold indicator taxa analysis. Our approach recorded a total of 529 roadkills, including 33 different species, comprising 13 mammal, 10 bird, 6 reptile, and 2 amphibian species. Statistical analysis indicated significant temporal trends for the red fox, the European hedgehog, the stone marten and the European badger, with peaks in roadkill occurrence between the winter and spring months. Relative roadkill abundance increased mostly in landscapes with anthropogenic land cover classes, such as complex cultivations, orchards, or urban surfaces. Our results allowed us to develop a map of potential roadkill risk that could assist in planning the placement of mitigation measures. Citizen science contributions from highly populated areas allowed data collection over a large area and a dense road network, and also directly led to the evaluation of management decisional options

Transizioni chirali in QCD con fermioni nell'aggiunta

I toy-model come la QCD con simmetria $SU(2)$ di colore o la QCD con fermioni in rappresetntazione dell'aggiunta (brevemente aQCD), sono teorie che vengono studiate perché, anche se non realistiche, sono risolvibili o più facilmente esplorabili della teoria "vera" in alcuni settori. Il motivo che rende interessanti le teorie QCD-like sopra citate è che, possedendo i fermioni in rappresentazione reali del gruppo di gauge, non soffrono del "problema del segno". Quest'ultimo è un problema della QCD a densità barionica $mu eq0$ che deriva dal fatto che il determinante dell'operatore di Dirac $mathcal D=igamma_ umathcal D^ u+m_q+igamma_0mu$ in queste condizioni non è in generale reale: egin{equation} onumber det{mathcal D(mu)} eqdet{mathcal D^*(mu)}=det{mathcal D(mu)} end{equation} e ciò invalida gli usuali metodi di simulazioni Montecarlo. Per l'appunto nella QCD a due colori o nella aQCD questo problema non si pone. \ In questo lavoro studierò in particolare il caso della aQCD. In ragione della realità dei gruppi di gauge hanno un allargamento della simmetria globale $SU_V(N_f)oplus SU_A(N_f)oplus U_B(1) ightarrow SU(2N_f)$. Si sa che a temperatura nulla i fermioni di questa teoria condensano e il condensato chirale assume un VEV $media{overline psi psi} eq0$, che rompe spontaneamente la simmetria egin{equation} SU(2N_f) ightarrow SO(2N_f)label{simmetria} end{equation} Scopo del lavoro è sviluppare una teoria effettiva che descrive i gradi di libertà del condensato chirale, e studiare tramite i metodi di gruppo di rinormalizzazione applicati a questa teoria effetiva l'ordine della transizione chirale che si ha alla restorazione della simmetria ( ef{simmetria}) a temperatura finita. Il calcolo è stato fatto nel caso di $N_f$ generico sia considerando la presenza dell'anomalia assiale (simmetria $SU(2N_f)$) che trascurandola ($U(2N_f)$). Il risultato ottenuto è che le transizioni sono di I ordine

Non-linear analysis of pile groups under general loading conditions

A computer program (called PGROUPN) has been developed for the non-linear analysis of pile groups subjected to any combination of vertical loads, horizontal loads and moments. The code is based on a complete boundary element approach and may be regarded as a generic descendant of the program PGROUP (Banerjee & Driscoll, 1976) which has been extended in order to make the analysis numerically efficient for practical problems and to include the effects of soil nonlinearity by means of a stepwise linear incremental procedure. One of the main advantages of a non-linear analysis system over a linear elastic approach is that it has the desirable effect of demonstrating a reduction of the corner loads in larger groups in both the vertical and horizontal senses. This observation is of basic importance in practice because it offers the prospect of tangible improvements in design procedures and potential saving of materials. The non-linear analysis put forward in this thesis may be applied to large pile groups embedded in cohesive soil, specifically fully saturated clay under undrained conditions. The soil is modelled as an elastic-perfectly plastic material, which is assumed to behave linearly elastic at small strain levels, but fails when the stresses at the pile-soil interface reach certain limiting values. The analysis only requires the definition of three soil parameters whose physical meanings are clear, ie the (initial tangent) Young’s modulus Es, the Poisson’s ratio vs and the undrained shear strength Cu. This represents a significant advantage over more common load-transfer approaches which are based on either empirical parameters or the results of full-scale pile load tests. The validity and accuracy of the proposed PGROUPN solution have been verified by comparison with alternative numerical analysis for single piles and pile groups subjected to axial and lateral loads. Benchmark solutions in the linear and non-linear range are presented, and the critical question of estimation of soil parameters is addressed. Finally, two published case histories are described which demonstrate the applicability of the method to practical problems