Regularity for quasilinear PDEs in Carnot groups via Riemannian approximation

 We study the interior regularity of weak solutions to subelliptic quasilinear PDEs in Carnot groups of the formΣi=1m1Xi (Φ(|∇Hu|2)Xiu) = 0.Here ∇Hu = (X1u,...,Xmiu) is the horizontal gradient, δ > 0 and the exponent p ∈ [2, p*), where p* depends on the step ν and the homogeneous dimension Q of the group, and it is given byp* = min {2ν ∕ ν-1 , 2Q+8 ∕ Q-2}.Sunto. Studiamo la regolarità interna delle soluzioni deboli di EDP, quasilineari subellittiche in gruppi di Carnot, della formaΣi=1m1Xi (Φ(|∇Hu|2)Xiu) = 0.Qui ∇Hu = (X1u,...,Xmiu) è il gradiente orizzontale, δ > 0 e l'esponente p ∈ [2, p*), dove p* dipende dal passo ν e dalla dimensione omogenea Q del gruppo ed è dato dap* = min {2ν ∕ ν-1 , 2Q+8 ∕ Q-2}

Threshold Saturation in Spatially Coupled Constraint Satisfaction Problems

We consider chains of random constraint satisfaction models that are spatially coupled across a finite window along the chain direction. We investigate their phase diagram at zero temperature using the survey propagation formalism and the interpolation method. We prove that the SAT-UNSAT phase transition threshold of an infinite chain is identical to the one of the individual standard model, and is therefore not affected by spatial coupling. We compute the survey propagation complexity using population dynamics as well as large degree approximations, and determine the survey propagation threshold. We find that a clustering phase survives coupling. However, as one increases the range of the coupling window, the survey propagation threshold increases and saturates towards the phase transition threshold. We also briefly discuss other aspects of the problem. Namely, the condensation threshold is not affected by coupling, but the dynamic threshold displays saturation towards the condensation one. All these features may provide a new avenue for obtaining better provable algorithmic lower bounds on phase transition thresholds of the individual standard model

Decay estimates and a vanishing phenomenon for the solutions of critical anisotropic equations

We investigate the asymptotic behavior of solutions of anisotropic equations of the form $-\sum_{i=1}^n\partial_{x_i}(\left|\partial_{x_i}u\right|^{p_i-2}\partial_{x_i}u)=f(x,u)$ in $\mathbb{R}^n$, where $p_i>1$ for all $i=1,\dotsc,n$ and $f$ is a Caratheodory function with critical Sobolev growth. This problem arises in particular from the study of extremal functions for a class of anisotropic Sobolev inequalities. We establish decay estimates for the solutions and their derivatives, and we bring to light a vanishing phenomenon which occurs when the maximum value of the exponents $p_i$ exceeds a critical value.Comment: Final version to appear in Advances in Mathematic

C1,αC^{1,\alpha}-Regularity of Quasilinear equations on the Heisenberg Group

In this article, we reproduce results of classical regularity theory of quasilinear elliptic equations in the divergence form, in the setting of Heisenberg Group. The conditions encompass a very wide class of equations with isotropic growth conditions, which are a generalization of the $p$-Laplace type equations in this respect; these also include all equations with polynomial or exponential type growth. In addition, some even more general conditions have also been explored.Comment: long versio

Maximum Principle for Quasi-linear Backward Stochastic Partial Differential Equations

In this paper we are concerned with the maximum principle for quasi-linear backward stochastic partial differential equations (BSPDEs for short) of parabolic type. We first prove the existence and uniqueness of the weak solution to quasi-linear BSPDE with the null Dirichlet condition on the lateral boundary. Then using the De Giorgi iteration scheme, we establish the maximum estimates and the global maximum principle for quasi-linear BSPDEs. To study the local regularity of weak solutions, we also prove a local maximum principle for the backward stochastic parabolic De Giorgi class