BPHZ renormalisation and vanishing subcriticality asymptotics of the fractional $\Phi^3_d$ model

Nils Berglund (1) , Yvain Bruned (2)

1 IDP - Institut Denis Poisson
2 School of Mathematics - University of Edinburgh

We consider stochastic PDEs on the $d$-dimensional torus with fractional Laplacian of parameter $\rho\in(0,2]$, quadratic nonlinearity and driven by space-time white noise. These equations are known to be locally subcritical, and thus amenable to the theory of regularity structures, if and only if $\rho > d/3$. Using a series of recent results by the second named author, A. Chandra, I. Chevyrev, M. Hairer and L. Zambotti, we obtain precise asymptotics on the renormalisation counterterms as the mollification parameter $\varepsilon$ becomes small and $\rho$ approaches its critical value. In particular, we show that the counterterms behave like a negative power of $\varepsilon$ if $\varepsilon$ is superexponentially small in $(\rho-d/3)$, and are otherwise of order $\log(\varepsilon^{-1})$. This work also serves as an illustration of the general theory of BPHZ renormalisation in a relatively simple situation.

Mots clés: Subcriticality boundary; BPHZ renormalisation; Subcriticality boundary.; Fractional Laplacian; Stochastic partial differential equations; Regularity structures

Domaines: Probabilités [math.PR]; Equations aux dérivées partielles [math.AP]; Physique mathématique [math-ph]

Nils Berglund, Yvain Bruned. BPHZ renormalisation and vanishing subcriticality asymptotics of the fractional $\Phi^3_d$ model. 2021. ⟨hal-02199627⟩