arXiv subjects

Noah Porcelli

Publications and source records attributed to Noah Porcelli.

10 recordsLinked to original sources

arXiv2026

Bulk-deformations, Floer complex bordism, and Grothendieck-Riemann-Roch

Given a Liouville manifold, we compute a Floer-homotopical invariant -- the complexification of the lift of symplectic cohomology to complex cobordism -- in terms of a classical Floer-theoretic invariant, namely, symplectic cohomology bulk-deformed by the Chern character. We do this by giving an explicit model for the complexified homotopy groups of the MU-module spectrum associated to a complex-oriented flow category and proving a ``homotopy coherent'' version of the classical Grothedieck-Riemann-Roch theorem. Using the aforementioned relation, we establish a computable cohomological criterion, in terms of the pair-of-pants product and the BV operator on symplectic cohomology, for when this MU lift cannot be obtained via base change from the sphere spectrum; moreover, we give examples where this holds. Finally, we use this non-base change criterion to detect examples of non-trivial higher-dimensional complex cobordism classes of relative Gromov-Witten type moduli spaces in the context of a smooth complex projective variety relative to an ample smooth divisor.

math.SG↗

arXiv2026

Obstructions to homotopy invariance of loop coproduct via parametrised fixed-point theory

Given $f: M \to N$ a homotopy equivalence of compact manifolds with boundary, we use a construction of Geoghegan and Nicas to define its Reidemeister trace $[T] \in π_1^{st}(\mathcal{L} N, N)$. We realize the Goresky-Hingston coproduct as a map of spectra, and show that the failure of $f$ to entwine the spectral coproducts can be characterized by Chas-Sullivan multiplication with $[T]$. In particular, when $f$ is a simple homotopy equivalence, the spectral coproducts of $M$ and $N$ agree.

math.AT↗

arXiv2026

Open-closed maps and spectral local systems

Let $X$ be a graded Liouville domain. Fix a pair of infinite loop spaces $Ψ= (Θ\to Φ)$ living over $(BO \to BU)$. This determines a spectral Fukaya category $\mathcal{F}(X;Ψ)$ whenever $TX$ lifts to $Φ$, containing closed exact Lagrangians $L$ for which $TL$ lifts compatibly to $Θ$; and by Bott periodicity and index theory, a Thom spectrum $R$ with bordism theory $R_*$. This paper has two main goals: we incorporate rank one spectral local systems $ξ: L \to BGL_1(R)$ into the spectral category; and we prove that the bordism class $[(L,ξ)]$ defined by the open-closed map differs from the class $[L]$ by a multiplicative two-torsion element in $R^0(L)^{\times}$ determined by an action of the stable homotopy class of the Hopf map $η\in π_1^{st}$ on $ξ$. Methods include a twisting construction associating flow categories to spectral local systems, and a model for the open-closed map incorporating Schlichtkrull's construction of the trace map $BGL_1(R) \subseteq K(R) \to R$. The companion paper \cite{PS4} shows that (for Lagrangians which themselves admit spectral lifts) one can lift quasi-isomorphisms from $\mathbb{Z}$ to $Ψ$ at the cost of introducing rank one local systems. Together with the open-closed computation given here, this gives an essentially complete picture of the bordism-theoretic consequences of quasi-isomorphism in the classical exact Fukaya category.

math.SG↗

arXiv2026

Bordism from quasi-isomorphism

Let $X$ be a graded Liouville domain. Fix a pair of infinite loop spaces $Ψ= (Θ\to Φ)$ living over $(BO \to BU)$. This determines a spectral Fukaya category $\mathcal{F}(X;Ψ)$ whenever $TX$ lifts to $Φ$, containing closed exact Lagrangians $L$ for which $TL$ lifts compatibly to $Θ$; and by Bott periodicity and index theory, a Thom spectrum $R$ with bordism theory $R_*$. Suppose that $L$ and $K$ are quasi-isomorphic in the Fukaya category over $\mathbb{Z}$. We prove that: (a) if both lift to $\mathcal{F}(X;Ψ)$, then there is a rank one $R$-local system $ξ: L \to BGL_1(R)$ over $L$ so that $(L,ξ)$ and $K$ are quasi-isomorphic in the spectral Fukaya category; (b) when $X$ is polarised and $Ψ= (BO \times F \to BO)$, if only $K$ lifts to $\mathcal{F}(X;Ψ)$, then the composition $L \to B^2GL_1(R)$ of the stable Gauss map of $L$ and the delooped $J$-homomorphism is nullhomotopic. Combined with the computation of the open-closed fundamental class associated to $(L,ξ)$ in \cite{PS3}, these results have applications to bordism and stable homotopy types of quasi-isomorphic Lagrangians, to Hamiltonian monodromy groups, and to smooth structures on nearby Lagrangians. A key ingredient in the proofs is a new form of obstruction theory for flow categories `lying over' a manifold $L$, closely related to a `spectral Viterbo restriction functor' also introduced here.

math.SG↗

arXiv2025

Spectral Floer theory and tangential structures

In \cite{PS}, for a stably framed Liouville manifold $X$ we defined a Donaldson-Fukaya category $\mathcal{F}(X;\mathbb{S})$ over the sphere spectrum, and developed an obstruction theory for lifting quasi-isomorphisms from $\mathcal{F}(X;\mathbb{Z})$ to $\mathcal{F}(X;\mathbb{S})$. Here, we define a spectral Donaldson-Fukaya category for any `graded tangential pair' $Θ\to Φ$ of spaces living over $BO \to BU$, whose objects are Lagrangians $L\to X$ for which the classifying maps of their tangent bundles lift to $Θ\to Φ$. The previous case corresponded to $Θ= Φ= \{\mathrm{pt}\}$. We extend our obstruction theory to this setting. The flexibility to `tune' the choice of $Θ$ and $Φ$ increases the range of cases in which one can kill the obstructions, with applications to bordism classes of Lagrangian embeddings in the corresponding bordism theory $Ω^{(Θ,Φ),\circ}_*$. We include a self-contained discussion of when (exact) spectral Floer theory over a ring spectrum $R$ should exist, which may be of independent interest.

math.SG↗

arXiv2025

C^0 Lagrangian Monodromy

We prove that (under appropriate orientation assumptions), the action of a Hamiltonian homeomorphism ϕon the cohomology of a relatively exact Lagrangian fixed by ϕis the identity. This extends results of Hu-Lalonde-Leclercq and the author in the setting of Hamiltonian diffeomorphisms. We also prove a similar result regarding the action of ϕon relative cohomology.

math.SG↗

arXiv2025

On the parametrised Whitehead torsion of families of nearby Lagrangian submanifolds

Motivated by the strong nearby Lagrangian conjecture, we constrain the parametrised Whitehead torsion of a family of closed exact Lagrangian submanifolds in a cotangent bundle. We prove the parametrised Whitehead torsion admits a factorisation through simpler maps, in particular implying it is trivial on $π_0$, $π_1$, and that its image is divisible by the Euler characteristic. We provide concrete implications for the Lagrangian monodromy question in the case of a high dimensional torus. This generalises earlier work of Abouzaid and Kragh \cite{AbKr} on the $π_0$ version, using different methods. Our main tool is the theory of twisted generating functions, building on \cite{ACGK}.

math.SG↗

arXiv2024

Bordism of flow modules and exact Lagrangians

For a stably framed Liouville manifold X , we construct a "Donaldson-Fukaya category over the sphere spectrum" F(X; S). The objects are closed exact Lagrangians whose Gauss maps are nullhomotopic compatibly with the ambient stable framing, and the morphisms are bordism classes of framed flow modules over Lagrangian Floer flow categories; this is enriched in modules over the framed bordism ring. We develop an obstruction theory for lifting quasi-isomorphisms in the usual Fukaya category to quasi-isomorphisms in appropriate truncations or quotients of F(X; S). Applications include constraints on the smooth structure of exact Lagrangians in certain plumbings, and the construction of non-trivial symplectic mapping classes which act trivially on the integral Fukaya category for a wide class of affine varieties.

math.SG↗

arXiv2024

Lagrangian intersections and cuplength in generalised cohomology theories

We find lower bounds on the number of intersection points between two relatively exact Hamiltonian isotopic Lagrangians. The bounds are given in terms of the cuplength of the Lagrangian in various multiplicative generalised cohomology theories. The intersection of the Lagrangians need not be transverse, however, we require certain orientation assumptions. This gives stronger bounds than previous estimates on the number of self-intersection points of a suitable closed, relatively exact Lagrangian diffeomorphic to Sp$(2)$ or Sp$(3)$. Our proof uses Lusternik-Schnirelmann theory, following and extending work by Hofer.

math.SG↗

arXiv2024

Families of relatively exact Lagrangians, free loop spaces and generalised homology

We prove that (under appropriate orientation conditions, depending on $R$) a Hamiltonian isotopy $ψ^1$ of a symplectic manifold $(M, ω)$ fixing a relatively exact Lagrangian $L$ setwise must act trivially on $R_*(L)$, where $R_*$ is some generalised homology theory. We use a strategy inspired by that of Hu, Lalonde and Leclercq (\cite{Hu-Lalonde-Leclercq}), who proved an analogous result over $\mathbb{Z}/2$ and over $\mathbb{Z}$ under stronger orientation assumptions. However the differences in our approaches let us deduce that if $L$ is a homotopy sphere, $ψ^1|_L$ is homotopic to the identity. Our technical set-up differs from both theirs and that of Cohen, Jones and Segal (\cite{Cohen-Jones-Segal, Cohen}). We also prove (under similar conditions) that $ψ^1|_L$ acts trivially on $R_*(\mathcal{L} L)$, where $\mathcal{L} L$ is the free loop space of $L$. From this we deduce that when $L$ is a surface or a $K(π, 1)$, $ψ^1|_L$ is homotopic to the identity. Using methods of \cite{Lalonde-McDuff}, we also show that given a family of Lagrangians all of which are Hamiltonian isotopic to $L$ over a sphere or a torus, the associated fibre bundle cohomologically splits over $\mathbb{Z}/2$.

math.SG↗