Abstract
We prove that the
$\infty $
-category of
$\mathrm{MGL} $
-modules over any scheme is equivalent to the
$\infty $
-category of motivic spectra with finite syntomic transfers. Using the recognition principle for infinite
$\mathbf{P} ^1$
-loop spaces, we deduce that very effective
$\mathrm{MGL} $
-modules over a perfect field are equivalent to grouplike motivic spaces with finite syntomic transfers.
Along the way, we describe any motivic Thom spectrum built from virtual vector bundles of nonnegative rank in terms of the moduli stack of finite quasi-smooth derived schemes with the corresponding tangential structure. In particular, over a regular equicharacteristic base, we show that
$\Omega ^\infty _{\mathbf{P} ^1}\mathrm{MGL} $
is the
$\mathbf{A} ^1$
-homotopy type of the moduli stack of virtual finite flat local complete intersections, and that for
$n>0$
,
$\Omega ^\infty _{\mathbf{P} ^1} \Sigma ^n_{\mathbf{P} ^1} \mathrm{MGL} $
is the
$\mathbf{A} ^1$
-homotopy type of the moduli stack of finite quasi-smooth derived schemes of virtual dimension
$-n$
.
Milnor classes of local complete intersections
