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Entanglement and particle correlations of Fermi gases in harmonic traps
No full textWe investigate quantum correlations in the ground state of noninteracting
Fermi gases of N particles trapped by an external space-dependent harmonic
potential, in any dimension. For this purpose, we compute one-particle
correlations, particle fluctuations and bipartite entanglement entropies of
extended space regions, and study their large-N scaling behaviors. The
half-space von Neumann entanglement entropy is computed for any dimension,
obtaining S_HS = c_l N^(d-1)/d ln N, analogously to homogenous systems, with
c_l=1/6, 1/(6\sqrt{2}), 1/(6\sqrt{6}) in one, two and three dimensions
respectively. We show that the asymptotic large-N relation S_A\approx \pi^2
V_A/3, between the von Neumann entanglement entropy S_A and particle variance
V_A of an extended space region A, holds for any subsystem A and in any
dimension, analogously to homogeneous noninteracting Fermi gases
Entanglement entropies in free fermion gases for arbitrary dimension
No full textWe study the entanglement entropy of connected bipartitions in free fermion
gases of N particles in arbitrary dimension d. We show that the von Neumann and
Renyi entanglement entropies grow asymptotically as N^(1-1/d) ln N, with a
prefactor that is analytically computed using the Widom conjecture both for
periodic and open boundary conditions. The logarithmic correction to the
power-law behavior is related to the area-law violation in lattice free
fermions. These asymptotic large-N behaviors are checked against exact
numerical calculations for N-particle systems
Come scegliere il sistema CAD
No full textRIASSUNTO: Nel mercato dei software CAD manca una vera e propria guida che aiuti l’azienda nella scelta del sistema più congeniale. Questo articolo propone un metodo per la
scelta di un CAD nel panorama odierno, che ne ha visto un grande sviluppo e con sempre più novità, con considerazioni economiche relative ad un caso di studio SUMMARY: The market of CAD software lacks a proper guide that will help the company in choosing the most suitable configuration. This article proposes a method with economic considerations related to a case stud
Interplay between temperature and trap effects in one-dimensional lattice systems of bosonic particles
No full textWe investigate the interplay of temperature and trap effects in cold particle
systems at their quantum critical regime, such as cold bosonic atoms in optical
lattices at the transitions between Mott-insulator and superfluid phases. The
theoretical framework is provided by the one-dimensional Bose-Hubbard model in
the presence of an external trapping potential, and the trap-size scaling
theory describing the large trap-size behavior at a quantum critical point. We
present numerical results for the low-temperature behavior of the particle
density and the density-density correlation function at the Mott transitions,
and within the gapless superfluid phase
Roundness Evaluation by Genetic Algorithms
No full textRoundness is one of the most common features in machining, and various criteria may be used for roundness errors evaluation. The minimum zone tolerance (MZT) method produces more accurate solutions than data fitting methods like least squares interpolation. The problem modeling and the application of Genetic Algorithms (GA) for the roundness evaluation is reviewed here. Guidelines for the GA parameters selection are also provided based on computation experiments
A Controllably Adhesive Climbing Robot Using Magnetorheological Fluid
No full textThe novel adhesive effects of magnetorheological fluid for use in climbing robotics were experimentally measured and compared to existing derived models. Contrary to these models, the fluid thickness between two parallel plates was found to have little effect on the adhesive failure strength and a positive effect on time to failure. Target surface roughness was found to have a detrimental effect on pull-off adhesion and a positive effect for shearing loads. A robot capable of adhering to ceilings was designed and shown to be capable of holding 7.6 kPa of adhesive stress in both shear on rough vertical surfaces and normal force on glass sheets, demonstrating a novel form of adhesion on a wide range of surface roughnesses and orientations
A vanishing result for strictly -convex domains
No full textIn view of Andreotti and Grauert (Bull Soc Math France 90:193–259, 1962) vanishing theorem for q -complete domains in Cn , we reprove a vanishing result by Sha (Invent Math 83(3):437–447, 1986), and Wu (Indiana Univ Math J 36(3):525–548, 1987), for the de Rham cohomology of strictly p -convex domains in Rn in the sense of Harvey and Lawson (The foundations of p -convexity and p -plurisubharmonicity in riemannian geometry. arXiv:1111.3895v1 [math.DG]). Our proof uses the L2 -techniques developed by Hörmander (An introduction to complex analysis in several variables, 3rd edn. North-Holland Publishing Co, Amsterdam 1990), and Andreotti and Vesentini (Inst Hautes Études Sci Publ Math 25:81–130, 1965)
Symplectic manifolds and cohomological decomposition
No full textGiven a closed symplectic manifold, we study when the Lefschetz decomposition
induced by the -representation yields a
decomposition of the de Rham cohomology. In particular, this holds always true
for the second de Rham cohomology group, or if the symplectic manifold
satisfies the Hard Lefschetz Condition
Constraints on the two-flavor QCD phase diagram from imaginary chemical potential
No full textSUMMARY We review our knowledge of the phase diagram of QCD as a function of
temperature, chemical potential and quark masses. The presence of tricritical
lines at imaginary chemical potential mu=i pi/3 T, with known scaling behaviour
in their vicinity, puts constraints on this phase diagram, especially in the
case of two light flavors. We show first results in our project to determine
the finite-temperature behaviour in the two-flavour chiral limit
Supersymmetry Breaking on Gauged Non-Abelian Vortices
No full textThere are a large number of systems characterized by a completely broken
gauge symmetry, but with an unbroken global color-flavor diagonal symmetry,
i.e., systems in the so-called color-flavor locked phase. If the gauge symmetry
breaking supports vortices, the latter develop non-Abelian orientational
zero-modes and become non-Abelian vortices, a subject of intense study in the
last several years. In this paper we consider the effects of weakly gauging the
full exact global flavor symmetry in such systems, deriving an effective
description of the light excitations in the presence of a vortex. Surprising
consequences are shown to follow. The fluctuations of the vortex orientational
modes get diffused to bulk modes through tunneling processes. When our model is
embedded in a supersymmetric theory, the vortex is still 1/2 BPS saturated, but
the vortex effective action breaks supersymmetry spontaneously