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Fast genetic algorithm for roundness evaluation by the minimum zone tolerance (MZT) method
No full textAccording to ISO 1101, “A geometrical tolerance applied to a feature defines the tolerance zone within which that feature shall be contained”.
The main goal of the minimum zone tolerance (MZT) method is to achieve the best estimation of the roundness error, but it is computationally intensive. This paper describes the application of a genetic algorithm (GA) to minimize the computation time in the evaluation of CMM roundness errors of a large cloud of sampled points.
Computational experiments have shown that by selecting the optimal GA parameters, namely a combination of the five genetic parameters related to population size, crossover, mutation, stop condition, and search space, the computation time can be reduced by up to one order of magnitude, allowing real-time operation.
Optimization has been tested using seven CMM samples, obtained from different machining features. The performance of the optimized algorithm has been validated using four benchmark samples from the literature and with certified samples
The Roberge-Weiss endpoint in N_f = 2 QCD
No full textSUMMARY We present the results of extensive simulations regarding the critical
behavior at the endpoint of the Roberge-Weiss transition for N_f = 2 QCD. We
confirm early evidence, presented in arXiv:0909.0254, according to which the
Roberge-Weiss endpoint is first order in the limit of large or small quark
masses, and second order for intermediate masses. A systematic study of the
transition strength as a function of the quark mass in the first order regions,
permits us to estimate the tricritical values of the quark mass separating the
second order region from the first order ones
Vortices and Monopoles in Mass-deformed SO and USp Gauge Theories
No full textEffects of mass deformations on 1/2 Bogomol'nyi-Prasad-Sommerfield (BPS)
non-Abelian vortices are studied in 4d N=2 supersymmetric U(1) \times SO(2n)
and U(1) \times USp(2n) gauge theories, with Nf=2n quark multiplets. The 2d
N=(2,2) effective worldsheet sigma models on the Hermitian symmetric spaces
SO(2n)/U(n) and USp(2n)/U(n) found recently which describe the low-energy
excitations of the orientational moduli of the vortices, are generalized to the
respective massive sigma models. The continuous vortex moduli spaces are
replaced by a finite number (2^{n-1} or 2^{n}) of vortex solutions. The 1/2 BPS
kinks connecting different vortex vacua are magnetic monopoles in the 4d
theory, trapped inside the vortex core, with total configurations being 1/4 BPS
composite states. These configurations are systematically studied within the
semi-classical regime
Chiral Properties of Strong Interactions in a Magnetic Background
No full textWe investigate the chiral properties of QCD in presence of a magnetic
background field and in the low temperature regime, by lattice numerical
simulations of N_f = 2 QCD. We adopt a standard staggered discretization, with
a pion mass around 200 MeV, and explore a range of magnetic fields (180 MeV)^2
\leq|e|B \leq (700 MeV)^2, in which we study magnetic catalysis, i.e. the
increase of chiral symmetry breaking induced by the background field. We
determine the dependence of the chiral condensate on the external field,
compare our results with existing model predictions and show that a substantial
contribution to magnetic catalysis comes from the modified distribution of
non-Abelian gauge fields, induced by the magnetic field via dynamical quark
loop effects
Tobia Scarpa and «tea culture»
No full textWhen conceived in the best possible way, a design idea is a work of art and only its master can bring out its extraordinary and noble qualities. The paper illustrates the design process by Tobia Scarpa in relation to the oriental culture. Just like the great tea masters who were honoured to have paved the way for future progress and to have been superseded by their pupils, Tobia Scarpa may be proud of having undertaken a journey on which he had the strength and determination to fill his suitcase with so many values and elevated cultural contents, important for the progress and development of creativity in art and architecture
The entanglement entropy of one-dimensional gases
No full textWe introduce a systematic framework to calculate the bipartite entanglement
entropy of a spatial subsystem in a one-dimensional quantum gas which can be
mapped into a noninteracting fermion system. To show the wide range of
applicability of the proposed formalism, we use it for the calculation of the
entanglement in the eigenstates of periodic systems, in a gas confined by
boundaries or external potentials, in junctions of quantum wires and in a
time-dependent parabolic potential
Beyond canonical DC programs: the single reverse polar problem
No full textWe propose a novel generalization of the canonical DC problem (CDC), and we study the convergence of outer approximation algorithms for its solution which use an approximated oracle for checking the global optimality conditions. Although the approximated optimality conditions are similar to those of CDC, this new class of problems is shown to significantly differ from its special case. Indeed, outer approximation approaches for CDC need be substantially modified in order to cope with the more general problem, bringing to new algorithms. We develop a hierarchy of conditions that guarantee global convergence, and we build three different cutting plane algorithms relying on them.<br /
QCD, monopoles on the Lattice and gauge invariance
No full textThe number and the location of the monopoles observed on the lattice in QCD
configurations happens to depend strongly on the choice of the gauge used to
expose them, in contrast to the physical expectation that monopoles be gauge
invariant objects. It is proved by use of the non abelian Bianchi identities
(NABI) that monopoles are indeed gauge invariant, but the method used to detect
them depends, in a controllable way, on the choice of the abelian projection.
Numerical checks are presented
Shape flows for spectral optimization problems
No full textSUMMARY We consider a general formulation of gradient flow evolution for problems
whose natural framework is the one of metric spaces. The applications we deal
with are concerned with the evolution of {\it capacitary measures} with respect
to the -convergence dissipation distance and with the evolution of
domains in spectral optimization problems
Measuring Gravito-magnetic Effects by Multi Ring-Laser Gyroscope
No full textSUMMARY We propose an under-ground experiment to detect the general relativistic
effects due to the curvature of space-time around the Earth (de Sitter effect)
and to rotation of the planet (dragging of the inertial frames or
Lense-Thirring effect). It is based on the comparison between the IERS value of
the Earth rotation vector and corresponding measurements obtained by a
tri-axial laser detector of rotation. The proposed detector consists of six
large ring-lasers arranged along three orthogonal axes.
In about two years of data taking, the 1% sensitivity required for the
measurement of the Lense-Thirring drag can be reached with square rings of 6
side, assuming a shot noise limited sensitivity ().
The multi-gyros system, composed of rings whose planes are perpendicular to one
or the other of three orthogonal axes, can be built in several ways. Here, we
consider cubic and octahedron structures. The symmetries of the proposed
configurations provide mathematical relations that can be used to study the
stability of the scale factors, the relative orientations or the ring-laser
planes, very important to get rid of systematics in long-term measurements,
which are required in order to determine the relativistic effects