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A comparison of three recent selection theorems

Caterina Maniscalco (2007)

Mathematica Bohemica

We compare a recent selection theorem given by Chistyakov using the notion of modulus of variation, with a selection theorem of Schrader based on bounded oscillation and with a selection theorem of Di Piazza-Maniscalco based on bounded 𝒜 , Λ -oscillation.

A descriptive definition of a BV integral in the real line

Diana Caponetti, Valeria Marraffa (1999)

Mathematica Bohemica

A descriptive characterization of a Riemann type integral, defined by BV partition of unity, is given and the result is used to prove a version of the controlled convergence theorem.

Area functionals and Godbillon-Vey cocycles

Takashi Tsuboi (1992)

Annales de l'institut Fourier

We investigate the natural domain of definition of the Godbillon-Vey 2- dimensional cohomology class of the group of diffeomorphisms of the circle. We introduce the notion of area functionals on a space of functions on the circle, we give a sufficiently large space of functions with nontrivial area functional and we give a sufficiently large group of Lipschitz homeomorphisms of the circle where the Godbillon-Vey class is defined.

Chain rules and p-variation

R. Norvaiša (2002)

Studia Mathematica

The main result is a Young-Stieltjes integral representation of the composition ϕ ∘ f of two functions f and ϕ such that for some α ∈ (0,1], ϕ has a derivative satisfying a Lipschitz condition of order α, and f has bounded p-variation for some p < 1 + α. If given α ∈ (0,1], the p-variation of f is bounded for some p < 2 + α, and ϕ has a second derivative satisfying a Lipschitz condition of order α, then a similar result holds with the Young-Stieltjes integral replaced by its extension.

Convergence of series of dilated functions and spectral norms of GCD matrices

Christoph Aistleitner, István Berkes, Kristian Seip, Michel Weber (2015)

Acta Arithmetica

We establish a connection between the L² norm of sums of dilated functions whose jth Fourier coefficients are ( j - α ) for some α ∈ (1/2,1), and the spectral norms of certain greatest common divisor (GCD) matrices. Utilizing recent bounds for these spectral norms, we obtain sharp conditions for the convergence in L² and for the almost everywhere convergence of series of dilated functions.

Curves in Banach spaces which allow a C 1 , BV parametrization or a parametrization with finite convexity

Jakub Duda, Luděk Zajíček (2013)

Czechoslovak Mathematical Journal

We give a complete characterization of those f : [ 0 , 1 ] X (where X is a Banach space) which allow an equivalent C 1 , BV parametrization (i.e., a C 1 parametrization whose derivative has bounded variation) or a parametrization with bounded convexity. Our results are new also for X = n . We present examples which show applicability of our characterizations. For example, we show that the C 1 , BV and C 2 parametrization problems are equivalent for X = but are not equivalent for X = 2 .

Differences of two semiconvex functions on the real line

Václav Kryštof, Luděk Zajíček (2016)

Commentationes Mathematicae Universitatis Carolinae

It is proved that real functions on which can be represented as the difference of two semiconvex functions with a general modulus (or of two lower C 1 -functions, or of two strongly paraconvex functions) coincide with semismooth functions on (i.e. those locally Lipschitz functions on for which f + ' ( x ) = lim t x + f + ' ( t ) and f - ' ( x ) = lim t x - f - ' ( t ) for each x ). Further, for each modulus ω , we characterize the class D S C ω of functions on which can be written as f = g - h , where g and h are semiconvex with modulus C ω (for some C > 0 ) using a new notion of...

Discrete approximation of the Mumford-Shah functional in dimension two

Antonin Chambolle, Gianni Dal Maso (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

The Mumford-Shah functional, introduced to study image segmentation problems, is approximated in the sense of vergence by a sequence of integral functionals defined on piecewise affine functions.

Équations de transport dont les vitesses sont partiellement B V

Nicolas Lerner (2003/2004)

Séminaire Équations aux dérivées partielles

Nous démontrons l’unicité des solutions faibles pour une classe d’équations de transport dont les vitesses sont partiellement à variations bornées. Nous nous intéressons à des champs de vecteurs du type a 1 ( x 1 ) · x 1 + a 2 ( x 1 , x 2 ) · x 2 , a 1 B V ( x 1 N 1 ) , a 2 L x 1 1 B V ( x 2 N 2 ) , avec une borne sur la divergence de chacun des champs a 1 , a 2 . Ce modèle a été étudié récemment dans [LL] par C. Le Bris et P.-L. Lions avec une régularité W 1 , 1  ; nous montrons ici également que, dans le cas W 1 , 1 , le contrôle L de la divergence totale du champ est suffisant. Notre méthode consiste à démontrer...

Existence of discontinuous absolute minima for certain multiple integrals without growth properties

Lamberto Cesari (1988)

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

In the present paper the author discusses certain multiple integrals I ( u ) of the calculus of variations satisfying convexity conditions, and no growth property, and the corresponding Serrin integrals ( u ) , to which the existence theorems in [3,4,5] do not apply. However, in the present paper, the integrals I ( u ) and ( u ) are reduced to simpler form H ( v ) and ( v ) to which the existence theorems above apply. Thus, we derive that I ( u ) ( u ) , H ( v ) ( v ) , we obtain the existence of the absolute minimum for the Serrin forms ( u ) and ( v ) , and...

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