86,721 research outputs found
On the Hamilton's isoperimetric ratio in complete Riemannian manifolds of finite volume
No full textWe study a family of geometric variational functionals introduced by Hamilton, and considered later by Daskalopulos, Sesum, Del Pino and Hsu, in order to understand the behavior of maximal solutions of the Ricci flow both in compact and noncompact complete Riemannian manifolds of finite volume. The case of dimension two has some peculiarities, which force us to use different ideas from the corresponding higher-dimensional case. Under some natural restrictions, we investigate sufficient and necessary conditions which allow us to show the existence of connected regions with a connected complementary set (the so-called “separating regions”). In dimension higher than two, the associated problem of minimization is reduced to an auxiliary problem for the isoperimetric profile (with the corresponding investigation of the minimizers). This is possible via an argument of compactness in geometric measure theory valid for the case of complete finite volume manifolds. Moreover, we show that the minimum of the separating variational problem is achieved by an isoperimetric region. The dimension two requires different techniques of proof. The present results develop a definitive theory, which allows us to circumvent the shortening curve flow approach of the above mentioned authors at the cost of some applications of the geometric measure theory and of the Ascoli-Arzela’s Theorem
Two bounds on the noncommuting graph
No full textErdős introduced the noncommuting graph in order to study the number of commuting elements in a
finite group. Despite the use of combinatorial ideas, his methods involved several techniques of classical analysis.
The interest for this graph has become relevant during the last years for various reasons. Here we deal with a
numerical aspect, showing for the first time an isoperimetric inequality and an analytic condition in terms of Sobolev
inequalities. This last result holds in the more general context of weighted locally finite graphs
Impiccamento accidentale in corso di manovre autoerotiche. Segnalazione casistica e revisione bibliografica
No full textThe role of platelet-rich plasma in association with bone grafting for treatment of residual alveolar cleft
No full textOn the QCD Sum Rule Determination of the Strange Quark Mass
No full textIn the QCD Sum Rule determination of m s using the two-point correlator of divergences of \DeltaS = 1 vector currents, the final uncertainty on m s is mainly due to the hadronic spectral function. Using a specific parameterization which fully takes into account the available experimental data on the Kß (I = 1=2; J P = 0 + ) system, characterized by the presence of a relevant nonresonant component in addition to the resonant one, we find m s (1 GeV ) 120 MeV . In particular, varying only the parameters describing the nonresonant Kß component and n f =3 MS we obtain m s (1 GeV ) = 125 \Gamma 160 MeV . This result is smaller than analogous ones obtained by using a parameterization in terms of only resonant states. We discuss how to systematically improve the determination of m s by this method. Light `current' quark masses have an important role in the theoretical description of low energy hadronic physics, and their actual values are needed as an input to quantitatively pre..
L'ecografia carotidea nell'arterosclerosi:comparazione con i riscontri anatomo-patologici
No full textCENSIMENTO DEI RISCHI NELLE LAVORAZIONI ARTIGIANE DEL TERRITORIO DI SETTE U.S.L. PUGLIESI. CRITERI METODOLOGICI E ANALISI DEI RISULTATI
No full text
Phase diagram of a generalized Winfree model
No full textWe study the phase diagram of a generalized Winfree model. The modification is such that the coupling
depends on the fraction of synchronized oscillators, a situation which has been noted in some experiments on
coupled Josephson junctions and mechanical systems. We let the global coupling k be a function of the
Kuramoto order parameter r through an exponent z such that z=1 corresponds to the standard Winfree model,
z1 strengthens the coupling at low r low amount of synchronization, and at z1, the coupling is weakened
for low r. Using both analytical and numerical approaches, we find that z controls the size of the incoherent
phase region and that one may make the incoherent behavior less typical by choosing z1. We also find that
the original Winfree model is a rather special case; indeed, the partial locked behavior disappears for z1. At
fixed k and varying , the stability boundary of the locked phase corresponds to a transition that is continuous
for z1. This change in the nature of the transition is in accordance with a previous
study of a similarly modified Kuramoto model
- …
