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27
Critical nonlinear elliptic equations with singularities and cylindrical symmetry, preprint SISSA
, 2002
"... We study the existence of solutions to a semilinear elliptic equation in the whole space. The equation has a cylindrical symmetry and we find cylindrical solutions. The main features of the problem are that the potential has a large set of singularities (i.e. a subspace), and that the nonlinearity ..."
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Cited by 15 (2 self)
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We study the existence of solutions to a semilinear elliptic equation in the whole space. The equation has a cylindrical symmetry and we find cylindrical solutions. The main features of the problem are that the potential has a large set of singularities (i.e. a subspace), and that the nonlinearity has a double powerlike behaviour, subcritical at infinity and supercritical near the origin. We also show that our results imply the existence of solitary waves with nonvanishing angular momentum for nonlinear evolution equations of Schrödinger and KleinGordon type. Stampato nel mese di Aprile 2005 presso il Centro Stampa
Quasiperiodic solutions of completely resonant forced wave equations, preprint Sissa
, 2005
"... Abstract. We prove existence of quasiperiodic solutions with two frequencies of completely resonant, periodically forced nonlinear wave equations with periodic spatial boundary conditions. We consider both the cases the forcing frequency is: (Case A) a rational number and (Case B) an irrational num ..."
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Cited by 7 (2 self)
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Abstract. We prove existence of quasiperiodic solutions with two frequencies of completely resonant, periodically forced nonlinear wave equations with periodic spatial boundary conditions. We consider both the cases the forcing frequency is: (Case A) a rational number and (Case B) an irrational number.
Homogenization of fiber reinforced brittle materials: the intermediate case. Preprint SISSA
, 2009
"... Abstract. We analyze the behavior of a fragile material reinforced by a reticulated elastic unbreakable structure in the case of antiplane shear. The microscopic geometry of this material is described by means of two small parameters: the period ε of the grid and the ratio δ between the thickness of ..."
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Cited by 5 (2 self)
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Abstract. We analyze the behavior of a fragile material reinforced by a reticulated elastic unbreakable structure in the case of antiplane shear. The microscopic geometry of this material is described by means of two small parameters: the period ε of the grid and the ratio δ between the thickness of the fibers and the period ε. We show that the asymptotic behavior as ε → 0+ and δ → 0+ depends dramatically on the relative size of these parameters. Indeed, in the two cases considered, i.e., ε δ and ε δ, we obtain two different limit models: a perfectly elastic model and an elastic model with macroscopic cracks, respectively.
Preprint SISSA 129/96/EP/A Kicked Neutron Stars and Microlensing
, 1996
"... Due to the large kick velocities with which neutron stars are born in supernovae explosions, their spatial distribution is more extended than that of their progenitor stars. The large scale height of the neutron stars above the disk plane makes them potential candidates for microlensing of stars in ..."
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Due to the large kick velocities with which neutron stars are born in supernovae explosions, their spatial distribution is more extended than that of their progenitor stars. The large scale height of the neutron stars above the disk plane makes them potential candidates for microlensing of stars in the Large Magellanic Cloud. Adopting for the distribution of kicks the measured velocities of young pulsars, we obtain a microlensing optical depth of τ ∼ 2N10 × 10 −8 (where N10 is the total number of neutron stars born in the disk in units of 10 10). The event duration distribution has the interesting property of being peaked at T ∼ 60 – 80 d, but for the rates to be relevant for the present microlensing searches would require N10 ∼> 1, a value larger than the usually adopted ones (N10 ∼ 0.1 – 0.2). The ongoing searches of baryonic dark matter in the Galaxy by means of microlensing of stars in the Large Magellanic Cloud (LMC) have produced very surprising results recently. Indeed, the first five events obtained by the EROS (Aubourg et al. 1993) and
Multimatrix models without continuous limit”, preprint SISSAISAS 211/92/EP
, 1992
"... We derive the discrete linear systems associated to multi–matrix models, the corresponding discrete hierarchies and the appropriate coupling conditions. We also obtain the W1+ ∞ constraints on the partition function. We then apply to multi– matrix models the technique, developed in previous papers, ..."
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Cited by 11 (0 self)
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We derive the discrete linear systems associated to multi–matrix models, the corresponding discrete hierarchies and the appropriate coupling conditions. We also obtain the W1+ ∞ constraints on the partition function. We then apply to multi– matrix models the technique, developed in previous papers, of extracting hierarchies of differential equations from lattice ones without passing through a continuum limit. In a q–matrix model we find 2q coupled differential systems. The corresponding differential hierarchies are particular versions of the KP hierarchy. We show that the multi–matrix partition function is a τ–function of these hierarchies. We discuss a few examples in the dispersionless limit.
Bolle: Fast Arnold's diffusion in three time scales systems, preprint SISSA
"... Abstract: We consider the problem of Arnold Diffusion for nearly integrable partially isochronous Hamiltonian systems with three time scales. By means of a careful shadowing analysis, based on a variational technique, we prove that, along special directions, Arnold diffusion takes place with fast (p ..."
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Cited by 1 (1 self)
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Abstract: We consider the problem of Arnold Diffusion for nearly integrable partially isochronous Hamiltonian systems with three time scales. By means of a careful shadowing analysis, based on a variational technique, we prove that, along special directions, Arnold diffusion takes place with fast (polynomial) speed, even though the “splitting determinant ” is exponentially small. 1
Preprint SISSA 6/96/A Cosmic Microwave Background non–Gaussian signatures from analytical texture models
, 1996
"... Using an analytical model for the Cosmic Microwave Background anisotropies produced by textures, we compute the resulting collapsed three–point correlation function and the rms expected value due to the cosmic variance. We apply our calculations to the COBE–DMR experiment and discuss the constraints ..."
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Using an analytical model for the Cosmic Microwave Background anisotropies produced by textures, we compute the resulting collapsed three–point correlation function and the rms expected value due to the cosmic variance. We apply our calculations to the COBE–DMR experiment and discuss the constraints that can be put to the model parameters. We also show that an experiment with smaller angular resolution can tighten these bounds. Typeset using REVTEX 1 I.
The complete structure of the nonlinear W4 and W5 algebras from quantum Miura transformation, SISSA preprint SISSA/76/93/EP
, 1993
"... Starting from the wellknown quantum Miura transformation for the Lie algebra An, we compute explicitly the OPEs for n = 3 and 4. The primary fields with spin 3, 4 and 5 are found (for general n). By using these primary fields and the OPEs from quantum Miura transformation, we derive the complete st ..."
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Cited by 5 (1 self)
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Starting from the wellknown quantum Miura transformation for the Lie algebra An, we compute explicitly the OPEs for n = 3 and 4. The primary fields with spin 3, 4 and 5 are found (for general n). By using these primary fields and the OPEs from quantum Miura transformation, we derive the complete structure of the nonlinear W4 and W5 algebras. It is known that the quantum Miura transformation for the Lie algebra An ≃ sl(n + 1) gives a quadratic nonlinear algebra [1]. This algebra is believed to be identical with the nonlinear extended conformal algebra Wn+1, generated by fields Wk’s with the integer k ranging from 2 to n + 1. For n = 1 and n = 2, this gives the Virasoro algebra and the wellknown Zamolodchikov’s nonlinear W3 algebra [2]. For the general case such identification is not established explicitly. The problem with this identification comes from the fact that the basis fields in the quantum Miura transformation are not primary fields and the higher spin fields in Wn are all primary fields (by definition). It is still an important open problem to find a primary basis in the quantum Miura transformation. Given the difficulty
Results 1  10
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27