Two-scale convergence is a powerful mathematical tool in periodic homogenization developed for modelling media with periodic structure. The contribution deals with the classical definition, its problems, the ``dual'' definition based on the so-called periodic unfolding. Since in the case of domains with boundary the unfolding operator introduced by D. Cioranescu, A. Damlamian, G. Griso does not satisfy the crucial integral preserving property, the contribution proposes a modified unfolding operator...

We show that for every $\epsilon >0$, there is a set $A\subset {ℝ}^2$ such that ${\mathscr{H}}^1⌞A$ is a monotone measure, the corresponding tangent measures at the origin are not unique and ${\mathscr{H}}^1⌞A$ has the $1$-dimensional density between $1$ and $3+\epsilon$ everywhere on the support.

We derive sharp necessary conditions for weak sequential lower semicontinuity of integral functionals on Sobolev spaces, with an integrand which only depends on the gradient of a scalar field over a domain in ${ℝ}^N$. An emphasis is put on domains with infinite measure, and the integrand is allowed to assume the value $+\infty$.

We consider the lower semicontinuous functional of the form $I_f\left(u\right)={\int }_{\Omega }f\left(u\right)\mathrm{d}x$ where $u$ satisfies a given conservation law defined by differential operator of degree one with constant coefficients. We show that under certain constraints the well known Murat and Tartar’s $\Lambda$-convexity condition for the integrand $f$ extends to the new geometric conditions satisfied on four dimensional symplexes. Similar conditions on three dimensional symplexes were recently obtained by the second author. New conditions apply to quasiconvex...

We consider the lower semicontinuous functional of the form $I_f\left(u\right)={\int }_{\Omega }f\left(u\right)\mathrm{d}x$ where u satisfies a given conservation law defined by differential operator of degree one with constant coefficients. We show that under certain constraints the well known Murat and Tartar's Λ-convexity condition for the integrand f extends to the new geometric conditions satisfied on four dimensional symplexes. Similar conditions on three dimensional symplexes were recently obtained by the second author. New conditions apply...

We approximate, in the sense of Γ-convergence, free-discontinuity functionals with linear growth in the gradient by a sequence of non-local integral functionals depending on the average of the gradients on small balls. The result extends to higher dimension what we already proved in the one-dimensional case.

Questa nota tratta dell'approssimazione di funzionali, usati in problemi con discontinuità libere, mediante famiglie di funzionali non locali in cui il gradiente è sostituito dal rapporto incrementale. Vengono inoltre presentate alcune applicazioni di questa teoria a problemi variazionali e di evoluzione.

Given an open subset $\mathrm{\Omega }$ of ${ℝ}^n$ and a Borel function $f:\mathrm{\Omega }\times ℝ\times {ℝ}^n\to [0,+\mathrm{\infty }[$, conditions on $f$ are given which assure the lower semicontinuity of the functional ${\int }_{\mathrm{\Omega }}f(x,u,Du)dx$ with respect to different topologies.

Sia $f=f(x,z)$ quasiconvessa in $z$, quasiperiodica in $x$ nel senso di Besicovitch e soddisfi le disuguaglianze: $${|z|}^p\le f(x,z)\le \mathrm{\Lambda }(1+{|z|}^p).$$ Allora $f$ può essere omogeneizzata: esiste una funzione $\mathrm{\Psi }$ che dipende solo da $z$ tale che i funzionali $${\int }_{\mathrm{\Omega }}f(\frac{x}{ϵ},Du(x))dx\mathit{\hspace{1em}\hspace{1em}}u\in H^{1,p}(\mathrm{\Omega };{ℝ}^m)$$ convergono, per $ϵ$ tendente a $0$ (nel senso della $\mathrm{\Gamma }$-convergenza) a $${\int }_{\mathrm{\Omega }}\mathrm{\Psi }(Du(x))dx.$$ Inoltre si può dare una formula asintotica per $\mathrm{\Psi }$.