Relaxation and Γ-convergence of quadratic forms inBV(I; ℝ n )

We study the lower semicontinuous envelope and the Γ-limit of degenerate quadratic integral functionals, on the space of the vector-valued functions of bounded variation defined on an interval, which are still quadratic integral functionals. We give an integral representation formula involving a new «relaxed» matrix and some linear contraints on the derivative measure.     

Algebre Booleane e loro struttura interna analitica (funzionale e matriciale) e geometrica (metrica e topologica)

Sunto In un'algebra booleana finita si presenta il fatto nuovo che molte delle strutture in essa costruibili a partire dai suoi elementi, sono intimamente connesse, si da essere aspetti diversi della stessa cosa. Si rileva che funzioni intere (cioè quelle che si ottengono operando su una variabile booleana con le operazioni booleane) matrici, ideali, filtri (e le formazioni più ampie che sono gli intervalli) e classi di equivalenza, mostrano appunto questo allacciamento. Inoltre, ognuna di queste formazioni dà in sostanza origine ad altre algebre booleane o a queste isomorfe, o di queste qiù ampie. Quindi, in un certo senso, il campo booleano è completo, riproducendosi in sè per quasi tutte le strutture in esso fattibili. Ma vi è di piu. Se nella formulazione del concetto di misura si abbandona l'idea del numero, quale ? misura di estensione ?, riesce possibile stabilire un concetto di ? di stanza booleana ? di due elementi booleani, la quale soddisfi alla fondamentale relazione triangolare e alla condizione di annullarsi quando e solo quando gli elementi coincidono. Potremo perciò parlare di una metrica intrinseca di un'algebra diBoole; e attraverso opportune definizioni si può estendere questa metrica anche ad aggruppamenti di tre o quattro o più elementi. Ma definita che sia questa metrica ? interna ? viene anche definita, oltre la struttura algebrica, e quella di geometria metrica, una struttura topologica interna. Ed è appunto quanto esprimiamo im questo lavoro, ricollegandoci ad altri precedenti (*) A Enrico Bompiani in occasione del suo Giubileo scientifico     

The Muskat problem and related topics

In the paper, we consider the evolution of the free boundary separating two immiscible viscous fluids with different constant densities in an absolutely rigid solid body and in an elastic skeleton. The motion of the liquids is described by the Stokes equations driven by the input pressure and the force of gravity. For flows in a bounded domain, we prove the existence and uniqueness of classical solutions and emphasize the study of the properties of the moving boundary separating the two fluids.     

Pauli problem and related mathematical problems

We formulate several mathematical modifications of the Pauli problem of recovering the particle state from the results of measuring its coordinates and momenta, including the most abstract statement of the problem for two projection-valued measures. We describe how the Pauli problem reduces to the problem of finding the eigenvectors of certain operators. The performed analysis introduces the problems of modifications of Pauli pairs, and the considered topics and formulated problems require further study. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 157, No. 1, pp. 3–7, October, 2008.     

L 1-convergence of double cosine- and Walsh-Fourier series

We prove the convergence inL ¹([−gp, π)²)-norm of the double Fourier series of an integrable functionf(x, y) which is periodic and even with respect tox andy, with coefficientsa _jk satisfying certain conditions of Hardy-Karamata kind, and such thata _jk logj logk→0 asj, k→∞. These sufficient conditions become quite natural in particular cases. Then we extend these results to the convergence of double Walsh-Fourier series inL ¹ (0, 1)²)- norm. As a by-product, we obtain Tauberian conditions ensuring the convergence of a double numerical series provided it is Cesàro summable. This research was partially supported by the Hungarian National Foundation for Scientific Research under Grant # 234.     

The torus related Riemann problem

The Riemann jump problem is solved for analytic functions of several complex variables with the unit torus as the jump manifold. A well-posed formulation is given which does not demand any solvability conditions. The higher dimensional Plemelj-Sokhotzki formula for analytic functions in torus domains is established. The canonical functions of the Riemann problem for torus domains are represented and applied in order to construct solutions for both of the homogeneous and inhomogeneous problems. Thus contrary to earlier research the results are similar to the respective ones for just one variable. A connection between the Riemann and the Riemann-Hilbert boundary value problem for the unit polydisc is explained.     

Uniqueness theorems for a nonlinear Tricomi problem and the related evolution problem

We consider an initial-boundary value problem for the non-linear evolution equation in a cylinder Q_t = Ω × (0, t), where T[u] = yu_xx + u_yy is the Tricomi operator and l(u) a special differential operator of first order. In [10] we proved the existence of a generalized solution of problem (1) and the existence of a generalized solution of the corresponding stationary boundary value problem (non-linear Tricomi problem) In this paper we give sufficient conditions for the uniqueness of these solutions.     

半群上的Green(e)-关系

半群上的Green(e)-关系是半群上通常Green's关系的一种推广.借助半群的左(右)S-系及半群的双系深入研究了Green(e)-关系的代数性质,证明了每个H(e)-类R(e)e∩L(e)f为一个强无挠的(H(e)e,H(e)f)-双系,其中e,f为幂等元,并给出了每个含幂等元的D(e)-类的代数结构.     

Tauberian-type theorem for (e)-convergent sequences

We prove a Tauberian-type theorem for (e)-convergent sequences, which were introduced by the author in Karaev (2010) [4]. Our proof is based on the Berezin symbols technique of operator theory in the reproducing kernel Hilbert space.     

Free Completely J~(e)-simple Semigroups

A semigroup is called completely J~((e))-simple if it is isomorphic to some Rees matrix semigroup over a left cancellative monoid and each entry of whose sandwich matrix is in the group of units of the left cancellative monoid.It is proved that completely J~((e))-simple semigroups form a quasivarr ity.Moreover,the construction of free completely J~((e))-simple semigroups is given.It is found that a free completely J~((e))-simple semigroup is just a free completely J~*-simple semigroup and also a full subsemigroup of some completely simple semigroups.     

On Jc-contraction and related fixed-point problem with applications

We introduce J_c-contraction, which encompasses both F-contraction and JS-contraction. We investigate a fixed-point problem subject to J_c-contraction. The existence of the solutions to the linear matrix equation and system of fractional differential equations are discussed by the application of obtained results.     

An extremal problem related to probability

Summary We consider a walk from a stateA ₁ to a stateA _n+1 in which the probability of remaining atA _i isp _i , and the probability of progressing fromA _i toA _i+1 is 1 –p _i . The probabilityW _nk of reachingA _n+1 fromA ₁ in exactlyn + k steps can then be expressed as a polynomial of degreen + k in then variablesp ₁,,p _n . We determine the maximum value ofW _nk and the (unique) choice (p ₁,,p _n ) for which this extremum occurs.Dedicated to Professor Otto Haupt with best wishes on his 100th birthday     

ExponentialL 2-convergence of quantum Markov semigroups on\mathcal{B}(h)

With a quantum Markov semigroup (Τ _t ) _t≥0 on , whichhas a faithful normal invariant state ρ, we associate semigroupsT ^(s) (s∈[0],[1]) on the set of Hilbert-Schmidt operators onh defined by the rule . This allows us to use spectral theory to study the infinitesimal generatorL ^(s) of the semigroupT ^(s) and deduce information on the rate of the decay to equilibrium of Τ by means of estimates of the spectral gap ofL ^(s) . Fors=1/2, this method is applied to a class of quantum Markov semigroups on . We prove simple but reasonably general sufficient conditions, as well as necessary and sufficient conditions, for the gap(L ^(1/2)) to be positive. The exact value of the gap(L ^(1/2)) is computed or estimated for a certain class of equations motivated by classical probability or physical applications. Translated fromMatematicheskie Zametki, Vol. 68, No. 4, pp. 523–538, October, 2000.     

(Pre-)coxeter algebras and related topics

In this paper we discuss some relations between (pre-)Coxeter algebras and its related topics, and obtain some equivalent conditions.