Shell-filling effect in the entanglement entropies of spinful fermions.

We consider the von Neumann and Rényi entropies of the one-dimensional quarter-filled Hubbard model. We observe that for periodic boundary conditions the entropies exhibit an unexpected dependence on system size: for L=4 mod 8 the results are in agreement with expectations based on conformal field theory, while for L=0 mod 8 additional contributions arise. We explain this observation in terms of a shell-filling effect and develop a conformal field theory approach to calculate the extra term in the entropies.

Entanglement negativity in quantum field theory.

We develop a systematic method to extract the negativity in the ground state of a 1+1 dimensional relativistic quantum field theory, using a path integral formalism to construct the partial transpose ρ(A)(T(2) of the reduced density matrix of a subsystem [formula: see text], and introducing a replica approach to obtain its trace norm which gives the logarithmic negativity E=ln//ρ(A)(T(2))//. This is shown to reproduce standard results for a pure state. We then apply this method to conformal field theories, deriving the result E~(c/4)ln[ℓ(1)ℓ(2)/(ℓ(1)+ℓ(2))] for the case of two adjacent intervals of lengths ℓ(1), ℓ(2) in an infinite system, where c is the central charge.

θ dependence of the deconfinement temperature in Yang-Mills theories.

We determine the θ dependence of the deconfinement temperature of SU(3) pure gauge theory, finding that it decreases in the presence of a topological θ term. We do that by performing lattice simulations at imaginary θ, then exploiting analytic continuation. We also give an estimate of such dependence in the limit of a large number of colors N and compare it with our numerical results.

Entanglement entropy of one-dimensional gases.

We 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.

Exact solution for the Kardar-Parisi-Zhang equation with flat initial conditions.

We provide the first exact calculation of the height distribution at arbitrary time t of the continuum Kardar-Parisi-Zhang (KPZ) growth equation in one dimension with flat initial conditions. We use the mapping onto a directed polymer with one end fixed, one free, and the Bethe ansatz for the replicated attractive boson model. We obtain the generating function of the moments of the directed polymer partition sum as a Fredholm Pfaffian.

Combination of computer-aided detection algorithms for automatic lung nodule identification.

Purpose: The aim of this work is to evaluate the potential of combining different computer-aided detection (CADe) methods to increase the actual support for radiologists of automated systems in the identification of pulmonary nodules in CT scans.

Methods: The outputs of three different CADe systems developed by researchers of the Italian MAGIC-5 collaboration were combined. The systems are: the CAMCADe (based on a Channeler-Ant-Model which segments vessel tree and nodule candidates and a neural classifier), the RGVPCADe (a Region-Growing- Volume-Plateau algorithm detects nodule candidates and a neural network reduces false positives); the VBNACADe (two dedicated procedures, based respectively on a 3D dot-enhancement algorithm and on intersections of pleura surface normals, identifies internal and juxtapleural nodules, and a Voxel-Based-Neural-Approach reduces false positives.

Quantum quench in the transverse-field Ising chain.

We consider the time evolution of observables in the transverse-field Ising chain after a sudden quench of the magnetic field. We provide exact analytical results for the asymptotic time and distance dependence of one- and two-point correlation functions of the order parameter. We employ two complementary approaches based on asymptotic evaluations of determinants and form-factor sums.

Critical behavior and scaling in trapped systems.

We study the scaling properties of critical particle systems confined by a potential. Using renormalization-group arguments, we show that their critical behavior can be cast in the form of a trap-size scaling, resembling finite-size scaling theory, with a nontrivial trap critical exponent theta, which describes how the correlation length xi scales with the trap size l, i.e.

Efficient visible laser emission of GaN laser diode pumped Pr-doped fluoride scheelite crystals.

In the present work we report on the growth, spectroscopy and laser results of diode pumped Pr-doped LiYF(4), LiLuF(4) and LiGdF(4) fluoride, scheelite-type structure crystals. We measured the polarisation dependent absorption and emission properties as well as the decay time of the (3)P(0) level. Exploiting the (3)P(2) absorption around 444 nm, we obtained efficient laser emission under GaN laser diode pumping on several transitions from the green to the near infrared wavelength range.

Static and dynamic structure factors in three-dimensional randomly diluted Ising models.

We consider the three-dimensional randomly diluted Ising model and study the critical behavior of the static and dynamic spin-spin correlation functions (static and dynamic structure factors) at the paramagnetic-ferromagnetic transition in the high-temperature phase. We consider a purely relaxational dynamics without conservation laws, the so-called model A. We present Monte Carlo simulations and perturbative field-theoretical calculations.

Correlation functions of the one-dimensional attractive Bose gas.

The zero-temperature correlation functions of the one-dimensional attractive Bose gas with a delta-function interaction are calculated analytically for any value of the interaction parameter and number of particles, directly from the integrability of the model. We point out a number of interesting features, including zero recoil energy for a large number of particles, analogous to the Mössbauer effect.

Characterization of mammographic masses using a gradient-based segmentation algorithm and a neural classifier.

Computerized methods have recently shown a great potential in providing radiologists with a second opinion about the visual diagnosis of the malignancy of mammographic masses. The computer-aided diagnosis (CAD) system we developed for the mass characterization is mainly based on a segmentation algorithm and on the neural classification of several features computed on the segmented mass. Mass-segmentation plays a key role in most computerized systems.

Azimuthal anchoring energy at the interface between a nematic liquid crystal and a PTFE substrate.

The azimuthal anchoring energy of the nematic liquid crystal 4-pentyl-4'-cyanobiphenil (5CB) on a poly(tetrafluoroethylene) (teflon, PTFE) film is measured for the first time. The PTFE film is deposed using the Wittmann and Smith technique which consists on rubbing a bar of this polymer against a glass substrate at a controlled temperature and pressure. Measurements of the azimuthal anchoring energy are made with a reflectometric technique which provides high accuracy and sensitivity.

Chaotic behavior, collective modes, and self-trapping in the dynamics of three coupled Bose-Einstein condensates.

The dynamics of the three coupled bosonic wells (trimer) containing N bosons is investigated within a standard (mean-field) semiclassical picture based on the coherent-state method. Various periodic solutions (configured as pi-like, dimerlike, and vortex states) representing collective modes are obtained analytically when the fixed points of trimer dynamics are identified on the N=const submanifold in the phase space. Hyperbolic, maximum and minimum points are recognized in the fixed-point set by studying the Hessian signature of the trimer Hamiltonian.

Power-law time distribution of large earthquakes.

We study the statistical properties of time distribution of seismicity in California by means of a new method of analysis, the diffusion entropy. We find that the distribution of time intervals between a large earthquake (the main shock of a given seismic sequence) and the next one does not obey Poisson statistics, as assumed by the current models. We prove that this distribution is an inverse power law with an exponent mu=2.

25th-order high-temperature expansion results for three-dimensional Ising-like systems on the simple-cubic lattice.

25th-order high-temperature series are computed for a general nearest-neighbor three-dimensional Ising model with arbitrary potential on the simple cubic lattice. In particular, we consider three improved potentials characterized by suppressed leading scaling corrections. Critical exponents are extracted from high-temperature series specialized to improved potentials, obtaining gamma=1.

Improved high-temperature expansion and critical equation of state of three-dimensional Ising-like systems.

High-temperature series are computed for a generalized three-dimensional Ising model with arbitrary potential. Three specific "improved" potentials (suppressing leading scaling corrections) are selected by Monte Carlo computation. Critical exponents are extracted from high-temperature series specialized to improved potentials, achieving high accuracy; our best estimates are gamma=1.

Generalized crossover in multiparameter Hamiltonians.

Many systems near criticality can be described by Hamiltonians involving several relevant couplings and possessing many nontrivial fixed points. A simple and physically appealing characterization of the crossover lines and surfaces connecting different nontrivial fixed points is presented. Generalized crossover is related to the vanishing of the renormalization group function Z(-1)(t).

Canonical and noncanonical equilibrium distribution.

We address the problem of the dynamical foundation of noncanonical equilibrium. We consider, as a source of divergence from ordinary statistical mechanics, the breakdown of the condition of time scale separation between microscopic and macroscopic dynamics. We show that this breakdown has the effect of producing a significant deviation from the canonical prescription.

Fluctuation-dissipation process without a time scale.

We study the influence of a dissipation process on diffusion dynamics triggered by fluctuations with long-range correlations. We make the assumption that the perturbation process involved is of the same kind as those recently studied numerically and theoretically, with a good agreement between theory and numerical treatment. As a result of this assumption the equilibrium distribution departs from the ordinary canonical distribution.

Painleve' analysis of a variable coefficient Sine-Gordon equation.

In this paper we study a variable coefficient Sine-Gordon (vSG) equation given by theta(tt)-theta(xx)+F(x,t)sin theta=0 where F(x,t) is a real function. To establish if it may be integrable we have performed the standard test of Weiss, Tabor, and Carnevale (WTC). We have got that the (vSG) equation has the Painleve' property (Pp) if the function F(x,t) satisfies a well-defined nonlinear partial differential equation.