Displaying similar documents to “The Probabilistic Zeta Function of the Alternating Group Alt ( p + 1 )

The Schreier Property and Gauss' Lemma

Daniel D. Anderson, Muhammad Zafrullah (2007)

Bollettino dell'Unione Matematica Italiana

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Let D be an integral domain with quotient field D . Recall that D is Schreier if D is integrally closed and for all x , y , z D { 0 } , x | y z implies that x = r s where r | y e s | z . A GCD domain is Schreier. We show that an integral domain D is a GCD domain if and only if (i) for each pair a , b D { 0 } , there is a finitely generated ideal B such that a D b D = B v and (ii) every quadratic in D [ X ] that is a product of two linear polynomials in K [ X ] is a product of two linear polynomials in D [ X ] . We also show that D is Schreier if and only if every...

Eisenstein ideal and reducible λ -adic Representations Unramified Outside a Finite Number of Primes.

Miriam Ciavarella (2006)

Bollettino dell'Unione Matematica Italiana

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The object of this note is to study certain 2-dimensional λ -adic representations of Gal ( Q ¯ / Q ) ; fixed p 1 , , p n distinct primes, we will consider representations ρ : G G L 2 ( A ) , given by the matrix ρ = ( a b c d ) which are unramified outside p 1 , , p n , and the residue characteristic of λ , which are a product of m representations over finite extensions of the ring of Witt vectors of the residue field and which are reducible modulo λ . In analogy with the theory of the modular representations, we will introduce the analogue of Mazur's Hecke...

A New L 1 -Lower Semicontinuity Result

Daniele Graziani (2007)

Bollettino dell'Unione Matematica Italiana

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The aim of this work is to prove a chain rule and an L 1 -lower semicontinuity theorems for integral functional defined on B V ( Ω ) . Moreover we apply this result in order to obtain new relaxation and Γ -convergence result without any coerciveness and any continuity assumption of the integrand f ( x , s , p ) with respect to the variable s .

Congruences between modular forms and related modules

Miriam Ciavarella (2006)

Bollettino dell'Unione Matematica Italiana

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We fix a prime and let M be an integer such that M ; let f S 2 ( Γ 1 ( M 2 ) ) be a newform supercuspidal of fixed type at and special at a finite set of primes. For an indefinite quaternion algebra over Q , of discriminant dividing the level of f , there is a local quaternionic Hecke algebra T associated to f . The algebra T acts on a module M f coming from the cohomology of a Shimura curve. Applying the Taylor-Wiles criterion and a recent Savitt's theorem, T is the universal deformation ring of a global...

A Montel Type Result for Subharmonic Functions

R. Supper (2009)

Bollettino dell'Unione Matematica Italiana

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This article is devoted to sequences ( u n ) n of subharmonic functions in N , with finite order, whose means J u n ( r ) (over spheres centered at the origin, with radius r) satisfy such a condition as: r > 0 , A r > 0 such that J u n ( r ) A r , n 𝐍 . The paper investigates under which conditions one may extract a pointwise or uniformly convergent subsequence.

Correctors for Parabolic Equations in a Heterogeneous Fibered Medium

Mourad Sfaxi, Ali Sili (2007)

Bollettino dell'Unione Matematica Italiana

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We study the problem of correctors in the framework of the homogenization of linear parabolic equations posed in a heterogeneous medium Ω made of two materials. The first one is located in a set F ϵ of cylindrical parallel fibers periodically distributed with a period of size ϵ , and the second one is located in the "matrix" M ϵ = Ω F ϵ . The ratio between the conductivity coefficients of the two materials is of order 1 / ϵ 2 . After writing the homogenized problem, we give a corrector result and prove...

Isomorphisms of Royden Type Algebras Over 𝕊 1

Teresa Radice, Eero Saksman, Gabriella Zecca (2009)

Bollettino dell'Unione Matematica Italiana

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Let 𝕊 1 and 𝔻 be the unit circle and the unit disc in the plane and let us denote by 𝒜 ( 𝕊 1 ) the algebra of the complex-valued continuous functions on 𝕊 1 which are traces of functions in the Sobolev class W 1 , 2 ( 𝔻 ) . On 𝒜 ( 𝕊 1 ) we define the following norm u = u L ( 𝕊 1 ) + ( 𝔻 | u ~ | 2 ) 1 / 2 where is the harmonic extension of u to 𝔻 . We prove that every isomorphism of the functional algebra 𝒜 ( 𝕊 1 ) is a quasitsymmetric change of variables on 𝕊 1 .

Conductor and separating degrees for sets of points in r and in 1 × 1

Lucia Marino (2006)

Bollettino dell'Unione Matematica Italiana

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We attempt to generalize conductor degree's results, known in 2 , to the case of 0-dimensional schemes of r . In the first part of this paper, we consider the problem of characterizing the sequences generators's degrees of the conductor which are compatible with a fixed postulation (or Hilbert function) for a set of points in r and we determine the conductor degree of every point in a r -partial intersection. In addition, we define the separating degree of a point for a 0-dimensional subscheme...

On the projective genus of surfaces

Pietro Sabatino (2006)

Bollettino dell'Unione Matematica Italiana

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Let X N be a smooth irreducible non degenerate surface over the complex numbers, N 4 . We define the projective genus of X , denoted by P G ( X ) , as the geometric genus of the singular curve of the projection of X from a general linear subspace of codimension four. Denote by g ( X ) the sectional genus of X . In this paper we conjecture that the only surfaces for which P G ( X ) = g ( X ) - 1 are the del Pezzo surface in 4 , in 5 and a conic bundle of degree 5 in 4 . We prove that for N 5 if P G ( X ) = g ( X ) - 1 + λ , λ a non negative integer, then g ( X ) λ + 1 + α where...

Some Separation Axioms Via Ideals

D. Sivaraj, V. Renuka Devi (2007)

Bollettino dell'Unione Matematica Italiana

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We introduce a new class of spaces, called Hausdorff modulo or T 2 mod spaces with respect to an ideal which contains the class of all Hausdorff spaces. Characterizations of these spaces are given and their properties are investigated. The concept of compactness modulo an ideal was introduced by Newcomb in 1967 and studied by Hamlett and Jankovic in 1990. We study the properties of -compact subsets in Hausdorff modulo spaces and generalize some results of Hamlett and Jankovic....

Geometry of Syzygies via Poncelet Varieties

Giovanna Ilardi, Paola Supino, Jean Vallès (2009)

Bollettino dell'Unione Matematica Italiana

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We consider the Grassmannian 𝔾 r ( k , n ) of ( k + 1 ) -dimensional linear subspaces of V n = H 0 ( 1 , 𝒪 1 ( n ) ) . We define 𝔛 k , r , d as the classifying space of the k -dimensional linear systems of degree n on 1 , whose bases realize a fixed number r of polynomial relations of fixed degree d , say r syzygies of degree d . Firstly, we compute the dimension of 𝔛 k , r , d . In the second part we make a link between 𝔛 k , r , d and the Poncelet varieties. In particular, we prove that the existence of linear syzygies implies the existence of singularities on the...

A Regular Threefold of General Type with p g = 0 and P 2 = 6

M. Cristina Ronconi (2009)

Bollettino dell'Unione Matematica Italiana

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The range of the bigenus P 2 is one of the unsolved problems concerning smooth complex projective regular threefolds of general type with p g = 0 : The examples in the literature have P 2 5 . In the present paper we present a non-singular threefold with p g = q 1 = q 2 = 0 ; P 2 = 6 ; the bicanonical map is stably birational.

A Note on Sectorial and R-Sectorial Operators

Alberto Venni (2008)

Bollettino dell'Unione Matematica Italiana

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The following results are proved: (i) if α , β + and A is a sectorial operator, then the set { t α A β ( t + A ) ; t > 0 } is bounded; (ii) the same set of operators is R-bounded if A is R-sectorial.

On the Dirichlet Problem with Orlicz Boundary Data

Gabriella Zecca (2007)

Bollettino dell'Unione Matematica Italiana

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Let us consider a Young's function Φ : + + satisfying the Δ 2 condition together with its complementary function Ψ , and let us consider the Dirichlet problem for a second order elliptic operator in divergence form: { L u = 0 in  B u | B = f B the unit ball of n . In this paper we give a necessary and sufficient condition for the L ϕ -solvability of the problem, where L ϕ is the Orlicz Space generated by the function Φ . This means solvability for f L Φ in the sense of [5], [8], where the case Φ ( t ) = t p is treated. ...

Connected Components of Hurwitz Spaces of Coverings with One Special Fiber and Monodromy Groups Contained in a Weyl Group of Type B d

Francesca Vetro (2008)

Bollettino dell'Unione Matematica Italiana

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Let X , X , Y be smooth projective complex curves with Y curve of genus 1 . Let d be an integer 3 , let e ¯ = ( e 1 , , e r ) be a partition of d and let | e | = i = 1 r ( e i - 1 ) . Let X 𝜋 X 𝑓 Y be a sequence of coverings where π is a degree 2 branched covering and f is a degree d covering, with monodromy group S d , branched in n 2 + 1 points, one of which is special point c whose local monodromy has cycle type given by e ¯ . Moreover the branch locus of the covering π is contained in f - 1 ( c ) . In this paper we prove the irreducibility...

Relaxation and gamma-convergence of supremal functionals

Francesca Prinari (2006)

Bollettino dell'Unione Matematica Italiana

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We prove that the Γ -limit in L μ of a sequence of supremal functionals of the form F k ( u ) = μ - ess sup Ω f k ( x , u ) is itself a supremal functional. We show by a counterexample that, in general, the function which represents the Γ -lim F ( , B ) of a sequence of functionals F k ( u , B ) = μ - ess sup B f k ( x , u ) can depend on the set B and wegive a necessary and sufficient condition to represent F in the supremal form F ( u , B ) = μ - ess sup B f ( x , u ) . As a corollary, if f represents a supremal functional, then the level convex envelope of f represents its weak* lower semicontinuous envelope. ...

A Result About C 2 -Rectifiability of One-Dimensional Rectifiable Sets. Application to a Class of One-Dimensional Integral Currents

Silvano Delladio (2007)

Bollettino dell'Unione Matematica Italiana

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Let γ , τ : [ a , b ] R k + 1 be a couple of Lipschitz maps such that γ = ± | γ | τ almost everywhere in [ a , b ] . Then γ ( [ a , b ] ) is a C 2 -rectifiable set, namely it may be covered by countably many curves of class C 2 embedded in R k + 1 . As a conseguence, projecting the rectifiable carrier of a one-dimensional generalized Gauss graph provides a C 2 -rectifiable set.

Squarefree Lexsegment Ideals with Linear Resolution

Vittoria Bonanzinga, Loredana Sorrenti (2008)

Bollettino dell'Unione Matematica Italiana

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In this paper we determine all squarefree completely lexsegment ideals which have a linear resolution. Let M d denote the set of all squarefree monomials of degree d in a polynomial ring k [ x 1 , , x n ] in n variables over a field k . We order the monomials lexicographically such that x 1 > x 2 > > x n , thus a lexsegment (of degree d ) is a subset of M d of the form L ( u , v ) = { w M d : u w v } for some u , v M d con u v . An ideal generated by a lexsegment is called a lexsegment ideal. We describe the procedure to determine when such an ideal has a linear...

Convergence to Equilibrium of the Solution of Kac's Kinetic Equation. A Probabilistic View

Eugenio Regazzini (2009)

Bollettino dell'Unione Matematica Italiana

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Let f ( , t ) be the probability density function representing the solution of Kac's Boltzmann-like equation at time t , with initial data f 0 , and let g σ be the Gaussian density with zero mean and variance σ 2 , σ 2 being the value of the second moment of f 0 . Henry McKean Jr. put forward the conjecture that the total variation distance between f ( , t ) and g σ goes to zero, as t + , with an exponential rate equal to - 1 / 4 . This lecture aims at explaining the main efforts made to a view to validating this conjecture,...

Cohomology of Tango bundle on 5

Daniele Faenzi (2006)

Bollettino dell'Unione Matematica Italiana

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The Tango bundle T is defined as the pull-back of the Cayley bundle over a smooth quadric Q 5 in 6 via a map f existing only in characteristic 2 and factorizing the Frobenius φ . The cohomology of T is computed in terms of S C , φ * ( C ) , Sym 2 ( C ) and C , which we handle with Borel-Bott-Weil theorem.

Threefolds with Kodaira Dimension 0 or 3

Ezio Stagnaro (2007)

Bollettino dell'Unione Matematica Italiana

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Using the theory of adjoints and pluricanonical adjoints, we construct three nonsingular threefolds, as desingularizations of degree six hypersurfaces in 4 , having the irregularities q 1 = q 2 = 0 and the following periodical sequences of plurigenera respectively ( p g , P 2 , P 3 , , P m , ) = ( 0 , 0 , 1 , 0 , 0 , 1 , ) , ( 0 , 0 , 0 , 1 , 0 , 0 , 0 , 1 , ) , ( 0 , 0 , 0 , 0 , 1 , 0 , 0 , 0 , 0 , 1 , ) . In the Appendix, starting from the second above-mentioned example, we construct a threefold of general type with q q 1 = q 2 = 0 , p g = 1 , P 2 = 2 whose m-canonical transformation is birational if and only if m 11 .

Eigenfunctions of the Laplace Operators for a Building of Type G ~ 2

A. M. Mantero, A. Zappa (2009)

Bollettino dell'Unione Matematica Italiana

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Let Δ be thick affine building of type G ~ 2 the Laplace operators of Δ ; associated with a pair ( y 1 , y 2 ) ; is the Poisson transform of a suitable finitely additive measure on the maximal boundary Ω of Δ ; by using only the combinatorial structure of Δ .

Asymptotics for Eigenvalues of a Non-Linear Integral System

D.E. Edmunds, J. Lang (2008)

Bollettino dell'Unione Matematica Italiana

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Let I = [ a , b ] , let 1 < q , p < , let u and v be positive functions with u L p ( I ) e v L q ( I ) and let T : L p ( I ) L q ( I ) be the Hardy-type operator given by ( T f ) ( x ) = v ( x ) a x f ( t ) u ( t ) d t , x I . We show that the asymptotic behavior of the eigenvalues λ of the non-linear integral system g ( x ) = ( T F ) ( x ) ( f ( x ) ) ( p ) = λ ( T * g ( p ) ) ) ( x ) (where, for example, t ( p ) = | t | p - 1 sgn ( t ) is given by lim n n λ ^ n ( T ) = c p , q I ( u v ) r ) 1 / r d t 1 / r , for 1 < p < q < lim n n λ ˇ n ( T ) = c p , q I ( u v ) r d t 1 / r for 1 < q < p < Here r = 1 p + 1 p , c p , q is an explicit constant depending only on p and q , λ ^ ( T ) = max ( s p n ( T , p , q ) ) , λ ˇ n ( T ) = min ( s p n ( T , p , q ) ) where s p n ( T , p , q ) stands for the set of all eigenvalues λ corresponding to eigenfunctions g with n zeros.

The Martingale Problem in Hilbert Spaces

Giuseppe Da Prato, Luciano Tubaro (2008)

Bollettino dell'Unione Matematica Italiana

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We consider an SPDE in a Hilbert space H of the form d X ( t ) = ( A X ( t ) + b ( X ( t ) ) ) d t + σ ( X ( t ) ) d W ( t ) , X ( 0 ) = x H and the corresponding transition semigroup P t f ( x ) = 𝔼 [ f ( X ( t , x ) ) ] . We define the infinitesimal generator L ¯ of P t through the Laplace transform of P t as in [1]. Then we consider the differential operator L φ = 1 2 Tr [ σ ( x ) σ * ( x ) D 2 φ ] + b ( x ) , D φ defined on a suitable set V of regular functions. Our main result is that if V is a core for L ¯ , then there exists a unique solution of the martingale problem defined in terms of L . Application to the Ornstein-Uhlenbeck equation and to some regular...

Groups Generated by (near) Mutually Engel Periodic Pairs

Piotr Słanina, Witold Tomaszewski (2007)

Bollettino dell'Unione Matematica Italiana

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We use notations: [ x , y ] = [ x , 1 y ] and [ x , k + 1 y ] e [ [ x , k y ] , y ] . We consider groups generated by x , y satisfying relations x = [ x , n y ] , y = [ y , n x ] or [ x , y ] = [ x , n y ] , [ y , x ] = [ y , n x ] . We call groups of the first type mep-groups and of the second type nmep-groups. We show many properties and examples of mep- and nmep-groups. We prove that if p is a prime then the group S l 2 ( p ) is a nmep-group. We give the necessary and sufficient conditions for metacyclic group to be a nmep-group and we show that nmep-groups with presentation x , y [ x , y ] = [ x , 2 y ] , [ y , x ] = [ y , 2 x ] , x n , y m are finite.

A remark on complex powers of analytic functions

Giuseppe Zampieri (1985)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Sia K n un compatto, f 0 una funzione analitica all'intorno di K , ed m la massima molteplicità in K degli zeri di f ; si prova che la potenza f λ ( λ , R e λ > 1 m ) è integrabile in K . L'estensione meromorfa dell'applicazione λ f λ da R e λ > 0 a tutto (con valori in 𝒟 ( K ) anziché in L 1 ( K ) ) era già stata provata in [1] e [2].

A New Proof of the Boundedness of Maximal Operators on Variable Lebesgue Spaces

D. Cruz-Uribe, L. Diening, A. Fiorenza (2009)

Bollettino dell'Unione Matematica Italiana

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We give a new proof using the classic Calderón-Zygmund decomposition that the Hardy-Littlewood maximal operator is bounded on the variable Lebesgue space L p ( ) whenever the exponent function p ( ) satisfies log-Hölder continuity conditions. We include the case where p ( ) assumes the value infinity. The same proof also shows that the fractional maximal operator M a , 0 < a < n , maps L p ( ) into L q ( ) , where 1 / p ( ) - 1 / q ( ) = a / n .

Some properties of perfect metric spaces

Angelo Bella, Biagio Ricceri (1983)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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In questa Nota, dati uno spazio metrico perfetto X ed un suo sottoinsieme K chiuso e raro, si dimostra l'esistenza di una funzione continua f : X [ 0 , 1 ] tale che i n t ( f - 1 ( t ) ) = per ogni t [ 0 , 1 ] , f ( x ) = 0 per ogni x K e f ( y ) = 1 per qualche y X K . In particolare, ciò permette di dare risposta simultaneamente a due questioni poste in [2]. Si mettono in evidenza, poi, ulteriori conseguenze di tale risultato.

On Relative γ k -Sets

Maddalena Bonanzinga, Filippo Cammaroto, Bruno A. Pansera (2007)

Bollettino dell'Unione Matematica Italiana

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In this note we show a relative version of γ k -set introduced and studied in [12]. We give several characterizations of this property; in particular one of the characterizations is Ramsey theoretical. Also we give a result involving a property of the corresponding mapping between function spaces.

On the adjoint system to a very ample divisor on a surface and connected inequalities. Nota I

Antonio Lanteri, Marino Palleschi (1981)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Siano: S una superficie algebrica proiettiva complessa non singolare, K un divisore canonico ed H un divisore molto ampio su S . Questo lavoro ha per oggetto lo studio dell'indice di autointersezione ( K + H ) 2 . Si dimostra, innanzitutto, la disuguaglianza ( K + H ) 2 0 , nell'ipotesi che la superficie S ottenuta immergendo S mediante il sistema lineare completo | H | non sia uno scroll. Questa disuguaglianza è connessa con alcuni risultati di Sommese e Van de Ven sulla generazione del fascio 𝒪 s ( K + H ) . La dimostrazione...

A note on singular and degenerate abstract equations

Angelo Favini (1982)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Si considera l’equazione astratta B A 1 u + A 0 u = h , dove A i ( i = 0 , 1 ) e B sono convenienti operatori lineari chiusi fra spazi di Banach, A i non è necessariamente invertibile, e A 0 , A 1 non commutano con B . Si studiano esistenza ed unicità delle soluzioni. Si indicano alcune applicazioni a certe equazioni differenziali degeneri o singolari.

𝐋 -embedding, Amalgamation and 𝐋 -elementary equivalence

Daniele Mundici (1982)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Ogni logica L genera canonicamente la L -equivalenza L e la L -immersione 𝐿 proprio come la logica del primo ordine genera l’equivalenza elementare e l’immersione elementare . Astraendo da L , è interessante studiare in sè relazioni d’equivalenza e di immersione generali tra strutture. Mostriamo che esiste una corrispondenza biunivoca tra relazioni d’equivalenza con la proprietà di Robinson e relazioni d’immersione con la proprietà di Amalgamazione Forte ( A P + ). Caratterizziamo algebricamente...

A generalized exponential map for an affinely homogeneous cone

Umberto Sampieri (1983)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Dato un cono V aperto non vuoto, convesso, regolare e affinemente omogeneo in uno spazio vettoriale reale W di dimensione finita si prova che per ogni v appartenente a V esiste un diffeomorfismo E v : W V che soddisfa le condizioni seguenti E1) E v ( 0 ) = v ; E2) det ( d E v ( y ) ) = Φ V ( E v ( y ) ) - 1 per ogni y appartenente a W ove Φ V : V 𝐑 + è la funzione caratteristica di V .

On the abstract Cauchy problem in the case of constant domains

Paolo Acquistapace, Brunello Terreni (1984)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Si studiano esistenza, unicità e regolarità delle soluzioni strette, classiche e forti u 𝐂 ( [ 0 , T ] , E ) dell'equazione di evoluzione non autonoma u ( t ) - A ( t ) u ( t ) = f ( t ) con il dato iniziale u ( 0 ) = x , in uno spazio di Banach E . Gli operatori A ( t ) sono generatori infinitesimali di semi-gruppi analitici ed hanno dominio indipendente da t e non necessariamente denso in E . Si danno condizioni necessarie e sufficienti per l'esistenza e la regolarità hölderiana della soluzione e della sua derivata.

Nodal curves in 3 ( )

Edoardo Ballico, Paolo Oliverio (1984)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Siano d , g , t interi con 0 t g ; se esiste in 3 ( ) una curva connessa, non singolare di grado d e genere g , allora esiste in 3 ( ) una curva irriducibile di grado d , genere aritmetico g e t nodi.

Evolution equations for a class of non­linear operators

Ennio De Giorgi, Marco Degiovanni, Antonio Marino, Mario Tosques (1983)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Se A è un operatore in uno spazio di Hilbert e V è un sotto insieme di questo spazio, in molti problemi si è indotti a modificare A sul «bordo» di V in modo da ottenere un operatore A tale che le soluzioni dell'equazione differenziale associata 0 U + A ~ ( U ) non escano da V . Se V non è convesso, l'operatore A non rientra nei casi classici esaminati, ad esempio, in [1]. In questo lavoro introduciamo alcune classi di operatori che contengono, in qualçhe caso significativo, quelli del genere sopra...

Estimates near the boundary for second order derivatives of solutions of the Dirichlet problem for the biharmonic equation

Vladimir A. Kondratiev, Olga A. Oleinik (1986)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Per ogni soluzione della (1) nel dominio limitato Ω ,, appartenente a H 0 2 ( Ω ) e soddisfacente le condizioni (2), si dimostra la maggiorazione (5), valida nell'intorno di ogni punto x 0 del contorno; si consente a Ω di essere singolare in x 0 .

Some Remarks on Prym-Tyurin Varieties

Giuliano Parigi (2007)

Bollettino dell'Unione Matematica Italiana

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The aims of the present paper can be described as follows: a) In [2] Beauville showed that if some endomorphism u a Jacobian J ( C ) has connected kernel, the principal polarization on J ( C ) induces a multiple of the principal polarization on the image of u . We reformulate and complete this theorem proving "constructively" the following: Theorem. Let Z J ( C ) be an abelian subvariety and Y its complementary variety. Z is a Prym-Tyurin variety with respect to J ( C ) if and only if the following sequence...

A curve of genus q with a Half-Canonical embedding in 𝐏 3

Sevin Recillas (1984)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Si costruiscono curve di genere g = 4 n 3 , n 3 che hanno 2 n - 3 ( 2 n - 2 - 1 ) fasci semicanonici L tali che h 0 ( L ) = 4 . Per n + 3 si dimostra che gli L sono molto ampi.

On a recursive formula for the sequence of primes and applications to the twin prime problem

Giovanni Fiorito (2006)

Bollettino dell'Unione Matematica Italiana

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In this paper we give a recursive formula for the sequence of primes { p n } and apply it to find a necessary and sufficient condition in order that a prime number p n + 1 is equal to p n + 2 . Applications of previous results are given to evaluate the probability that p n + 1 is of the form p n + 2 ; moreover we prove that the limit of this probability is equal to zero as n goes to . Finally, for every prime p n we construct a sequence whose terms that are in the interval [ p n 2 - 2 , p n + 1 2 - 2 [ are the first terms of two twin primes. This...

On the ampleness of K X L n for a polarized threefold ( X , L )

Antonio Lanteri, Marino Palleschi (1985)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Siano X una varietà algebrica proiettiva complessa non singolare tridimensionale, L un fibrato lineare ampio su X , e n 2 un intero. Si prova che, a meno di contrarre un numero finito di - 1 -piani di X , il fibrato K X L n è ampio ad eccezione di alcuni casi esplicitamente descritti. Come applicazione si dimostra l'ampiezza del divisore di ramificazione di un qualunque rivestimento di 𝐏 3 o della quadrica liscia di 𝐏 4 .

A note on semi-continuous mappings

Takashi Noiri (1973)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Se X ed Y sono spazi topologici, un'applicazione f : X Y dicesi semicontinua [3] se, per ogni insieme aperto V di Y , f - 1 ( V ) risulta un insieme semiaperto di X . Qui si studiano tali applicazioni e si dànno tre loro caratterizzazioni.

An Elliptic Problem with a Lower Order Term Having Singular Behaviour

Daniela Giachetti, François Murat (2009)

Bollettino dell'Unione Matematica Italiana

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We prove the existence of distributional solutions to an elliptic problem with a lower order term which depends on the solution u in a singular way and on its gradient D u with quadratic growth. The prototype of the problem under consideration is { - Δ u + λ u = ± | D u | 2 | u | k + f in Ω , u = 0 on Ω , where λ > 0 , k > 0 ; f ( x ) L ( Ω ) , f ( x ) 0 (and so u 0 ). If 0 < k < 1 , we prove the existence of a solution for both the "+" and the "-" signs, while if k 1 , we prove the existence of a solution for the "+" sign only.

A Note on Regular-closed Functions

Takashi Noiri (1981)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti

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Se X ed Y sono spazi topologici, una funzione f : X Y è detta regolarmente chiusa [5] se essa trasforma ogni insieme regolarmente chiuso di X in un insieme chiuso di Y . Si dimostra che una funzione regolarmente chiusa f : X Y risulta chiusa se X è normale.

A Note on -Maps

Zbigniew Duszyński (2007)

Bollettino dell'Unione Matematica Italiana

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Richness of the class of -maps [3] is investigated. Several consequences for the theory of quasi- -closed spaces are indicated.