Proprietà spettrali di una classe di operatori quasi ellittici

Riassunto In questo lavoro ci occupiamo di problemi al contorno per una classe di operatori lineari quasi ellittici del tipoA+σ, dove σ è una perturbazione assegnata; proviamo che l'operatore associato al problema è di Fredholm con indice zero e studiamo le proprietà spettrali dell'operatore associato al problema con condizioni al contorno omogenee.

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Summary In this paper we study boundary value problems for linear quasi elliptic (A+σ)-type operators, where σ is an assigned perturbation; we prove that the related operator is a Fredholm operator whose index is zero. Then we study spectral properties of the operator related to the problem with homogeneous boundary conditions.

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Lavoro eseguito nell'Istituto di Scienze dell'Informazione dell'Università di Salerno, nell'ambito del Gruppo Nazionale per l'Analisi Funzionale e le sue Applicazioni del C.N.R.     

Etheno derivatives of adenine and cytosine (review)

The method of modification of heterocyclic bases of nucleic acids with chloroacetaldehyde and other α-halo carbonyl compounds is examined in this review. The mechanism, kinetics, and scope of the reaction, the chemical properties of modified derivatives of adenine and cytosine, and the possibilities of the application of etheno derivatives of adenine and cytosine in biochemistry and molecular biology are discussed. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 291–305, March, 1980.     

η → 3π decay and πη scattering in chiral SU(2) × SU(2) symmetry

The problem of η → 3π decay in chiral SU(2) × SU(2) symmetry is investigated. We argue that the well-known difficulties of the conventional pole model originate from underestimating the role of the η-meson pole graph. This model is shown to be suitable for describing η → 3π decay if the strong ηηππ vertex in the η-pole graph is determined by an SU(2) × SU(2)-invariant interaction. The π^o ? η transition constant g_πη is evaluated from U-spin invariance with the help of a current-mixing model: | g_πη | ≈ 0.05. It turns out that the experimental data on both the decay widths and the energy spectrum can be satisfied by fitting the value of the ηηππ coupling constant as a parameter. As a result, predictions for the s- and p-wave πη scattering lengths are obtained: |a_πη⁰| ≈ 0.2m_π^?1, |a_πη¹| ≈ 0.1m_π^?3.     

Investigation into the width of the near turbulent wake behind a sphere at M∞=2, Re∞=1.5·106

The results are given of a investigation whose aim was to test the effectiveness of using a correlation coefficient as a criterion for choosing the empirical law of growth of the near turbulent wake behind a sphere at M=2, Re=1.5·10⁶.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 137–139, May–June, 1980.We are sincerely grateful to G. I. Petrov for discussion and valuable comments and indebted to B. M. Filippov for assistance in the experiments.     

Stationary macroscopic motions of a relativistic gas and its relation to the symmetries of the gravitational field

On the basis of an investigation of the Einstein-Vlasov self-consistent system of equations, a classification is given of the gravitational fields due to a collisionless gravitating gas, using the groups of the motions. It is shown that the time-like Killing vector, directed along the vector of the macroscopic gas velocity, is the center of the group of motions G_r.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 15–20, June, 1979.     

Interference effects in photoionization of noble gas atoms outer s-subshells

A strong influence of ns²np⁶ → ns²np⁵ εd transition on the outer ns subshell photoionization cross section of noble gas atomsis demonstrated.