Searcharxiv⌕ Search

arXiv subjects

Michele Schiavina

Publications and source records attributed to Michele Schiavina.

At least 19 recordsLinked to original sources
arXiv2026

Milnor metric for Morse--Smale flows from field theory

We study the partition function of Abelian $BF$ theory with an axial gauge fixing condition given by a Morse--Smale vector field, and we show that it recovers the Milnor metric on the determinant line on the twisted cohomology of the manifold. To do this we use the Batalin--Vilkovisky formalism and, in particular, a BV pushforward to cohomology in two steps. In this context, the Milnor metric serves as the generalisation of the Ruelle dynamical zeta function evaluated at zero for systems containing both closed orbits and critical points. This, together with a classic result due to Schwarz on the partition function of $BF$ theory in the Lorenz gauge, provides a field-theoretic realisation of Fried's conjecture, which is true for Morse--Smale flows.

math-ph↗
arXiv2026

Homotopies for Lagrangian field theory

Consider the variational bicomplex for $\mathcal{E}$ the space of sections of a graded, affine bundle. Local functionals $\mathcal{F}$ are defined as an equivalence class of density-valued functionals, which represent Lagrangian densities. A choice of a $k$-symplectic local form $ω$ on $\mathcal{E}$ induces a Lie$[k]$ algebra structure on (Hamiltonian) local functionals $(\mathcal{F}_{\mathrm{ham}},\{\cdot,\cdot\}_{\mathrm{ham}})$. For any $ω$ and any choice of a cohomological vector field $Q$ compatible with $ω$, we build three explicit $L_\infty$ algebras on a resolution of $\mathcal{F}_{\mathrm{ham}}$, which are all $L_\infty$ quasi-isomorphic to a dgL$[k]$a $(\mathcal{F}_{\mathrm{ham}},d_{\mathrm{ham}},\{\cdot,\cdot\}_{\mathrm{ham}})$. In particular, one of our equivalent $L_\infty$ algebras is a dgL$[k]$ algebra. In the case $k=-1$, this provides an explicit lift of the standard Batalin--Vilkovisky framework to local forms enriched by the $L_\infty$ structure, in terms of local homotopies, which interprets the modified classical master equation as a Maurer--Cartan equation for the distinguished dgL$[k]$a we construct. We conjecture that the data of a lift to local forms of a BV theory contains a homotopy moment map on the cohomology of the Koszul complex of the underlying Lagrangian field theory.

math-ph↗
arXiv2026

Perturbative algebraic quantum field theory with smoothened boundary

We formulate quantisation of gauge field theories on globally hyperbolic Lorentzian manifolds with marked hypersurfaces within the framework of perturbative algebraic quantum field theory (pAQFT) enriched by the Batalin, Fradkin, Vilkovisky formalism (BV/BFV). This allows one to incorporate some crucial aspects of the local functorial approach to gauge field theory on manifolds with boundary within the algebraic setting. In particular, we provide a pAQFT-formulation of the modified classical and quantum master equations (after Cattaneo, Mnev and Reshetikhin CMR), as well as a constructive way to build a renormalised quantum BFV operator correcting the failure of the Quantum Master Equation by means of boundary terms (in the appropriate sense). We find that the renormalised quantum homotopy dg Lie algebra arising from the Anomalous Master Ward Identity becomes curved when boundaries are considered. The failure of the quantum master equation is thus encoded by a nontrivial curvature term in an $L_\infty$ algebra. As a byproduct, we recover previous results of Hollands' on the relation between the (boundary) BRST charge and the BV operator, and we recover CMR's ansatz for the quantum BFV operator at leading perturbative order on causal cylinders in Abelian Yang--Mills theory.

math-ph↗
arXiv2025

Double BFV quantisation of 3d Gravity

We extend the cohomological setting developed by Batalin, Fradkin and Vilkovisky (BFV), which produces a resolution of coisotropic reduction in terms of hamiltonian dg manifolds, to the case of nested coisotropic embeddings $C\hookrightarrow C_\circ \hookrightarrow F$ inside a symplectic manifold $F$. To this, we naturally assign $\underline{C}$ and $\underline{C_\circ}$, as well as the respective BFV dg manifolds. We show that the data of a nested coisotropic embedding defines a natural graded coisotropic embedding inside the BFV dg manifold assigned to $\underline{C}$, whose reduction can further be resolved using the BFV prescription. We call this construction \emph{double BFV resolution}, and we use it to prove that "resolution commutes with reduction" for a general class of nested coisotropic embeddings. We then deduce a quantisation of $\underline{C}$, from the (graded) geometric quantisation of the double BFV Hamiltonian dg manifold (when it exists), following the quantum BFV prescription. As an application, we provide a well defined candidate space of (physical) quantum states of three-dimensional Einstein--Hilbert theory, which is thought of as a partial reduction of the Palatini--Cartan model for gravity.

math-ph↗
arXiv2025

Phase spaces in field theory: Reduction vs. resolution

In this note we review the concept of phase space in classical field theory, discussing several variations on the basic notion, as well as the relation between them. In particular we will focus on the case where the field theory admits local (gauge) symmetry, in which case the physical phase space of the system emerges after a (usually singular) quotient with respect to the action of the symmetry group. We will highlight the symplectic and Poisson underpinnings of the reduction procedure that defines a phase space, and discuss how one can replace quotients with graded smooth objects within classical field theory via cohomological resolutions, a practice that goes under the name of Batalin--Vilkovisky formalism. Special attention is placed on the reduction and resolution of gauge theories on manifolds with corners, which famously depend on a number of arbitrary choices. We phrase these choices in terms of homotopies for the variational bicomplex, and define a homotopy version of Noether's current and conservation theorem.

math-ph↗
arXiv2025

On the local constancy of regularized superdeterminants along special families of differential operators

We consider the flat-regularized determinant of families of operators of the form $D_τ=[δ_τ,d_\nabla]$, where $τ\toδ_τ$ are families of degree $-1$ maps in the twisted de Rham complex $\left(Ω^\bullet(M,E),d_\nabla\right)$ generalizing the (twisted) Hodge codifferential. We show that under suitable assumptions, both geometrical and analytical in nature, the flat-regularized determinant of $D_τ$, restricted to the subspace $\mathrm{im}(δ_τ)$, is constant in $τ$. The general result we present implies both local constancy of the Ray--Singer torsion and of the value at zero of the Ruelle zeta function for a contact Anosov flow, upon choosing $δ_τ= δ_{g_τ}$, the Hodge codifferential for a family of metrics, and $δ_τ=ι_{X_τ}$, the contraction along a family of (regular, contact) Anosov vector fields, respectively.

math.DG↗
arXiv2024

Null Hamiltonian Yang-Mills theory: Soft symmetries and memory as superselection

Soft symmetries for Yang-Mills theory are shown to correspond to the residual Hamiltonian action of the gauge group on the Ashtekar-Streubel phase space, which is the result of a partial symplectic reduction. The associated momentum map is the electromagnetic memory in the abelian theory, or a nonlinear, gauge-equivariant, generalization thereof in the nonabelian case. This result follows from an application of Hamiltonian reduction by stages, enabled by the existence of a natural normal subgroup of the gauge group on a null codimension-1 submanifold with boundaries. The first stage is coisotropic reduction of the Gauss constraint, and it yields a symplectic extension of the Ashtekar-Streubel phase space (up to a covering). Hamiltonian reduction of the residual gauge action leads to the fully-reduced phase space of the theory. This is a Poisson manifold, whose symplectic leaves, called superselection sectors, are labelled by the (gauge classes of the generalized) electric flux across the boundary. In this framework, the Ashtekar-Streubel phase space arises as an intermediate reduction stage that enforces the superselection of the electric flux at only one of the two boundary components. These results provide a natural, purely Hamiltonian, explanation of the existence of soft symmetries as a byproduct of partial symplectic reduction, as well as a motivation for the expected decomposition of the quantum Hilbert space of states into irreducible representations labelled by the Casimirs of the Poisson structure on the reduced phase space.

math-ph↗
arXiv2023

Gravity with torsion as deformed $BF$ theory

We study a family of (possibly non topological) deformations of $BF$ theory for the Lie algebra obtained by quadratic extension of $\mathfrak{so}(3,1)$ by an orthogonal module. The resulting theory, called quadratically extended General Relativity (qeGR), is shown to be classically equivalent to certain models of gravity with dynamical torsion. The classical equivalence is shown to promote to a stronger notion of equivalence within the Batalin--Vilkovisky formalism. In particular, both Palatini--Cartan gravity and a deformation thereof by a dynamical torsion term, called (quadratic) generalised Holst theory, are recovered from the standard Batalin--Vilkovisky formulation of qeGR by elimination of generalised auxiliary fields.

math-ph↗
arXiv2023

Hamiltonian gauge theory with corners: constraint reduction and flux superselection

We study gauge theories on spacetime manifolds with a codimension-$1$ submanifold with boundary. We characterise the reduced phase space of the theory whenever it is described by a local momentum map for the action of the gauge group $\mathcal{G}$, by means of Fréchet reduction by stages. The momentum map decomposes into a bulk term called constraint map, defining a coisotropic constraint set, and a boundary term called flux map. In the first stage, constraint reduction, the constraint set is the zero of a momentum map for a normal subgroup $\mathcal{G}_\circ\subset\mathcal{G}$, called constraint gauge group. In the second stage, flux superselection, the flux map is the momentum map for the residual action of the flux gauge group $\underline{\mathcal{G}}\doteq\mathcal{G}/\mathcal{G}_\circ$, which also controls equivariance. The reduced phase space of the theory, when smooth, is then only a partial Poisson manifold $\underline{\underline{\mathcal{C}}}\simeq \underline{\mathcal{C}}/\underline{\mathcal{G}}$. Its symplectic leaves are called \emph{flux superselection sectors}, for they provide a classical analogue of, and a road map to, the phenomenon of quantum superselection. To corners, we further assign a symplectic Lie algebroid over a Poisson manifold, $\mathsf{A}_{\partial} \to \mathcal{P}_{\partial}$, and show how on-shell configurations $\mathcal{C}_{\partial}\subset\mathcal{P}_{\partial}$ are also Poisson. Both $\mathcal{C}_{\partial}$ and $\underline{\underline{\mathcal{C}}}$ fibrate over a common space of superselections, labeling the Casimirs of both Poisson structures. We showcase the formalism by explicitly working out the first and second stage reductions for a broad class of Yang--Mills theories, where $\underline{\underline{\mathcal{C}}}$ is found to be a Weinstein space, and discuss further applications to topological theories.

math-ph↗
arXiv2023

BV Quantization

This note gives an overview of the BV formalism in its various incarnations and applications.

math-ph↗
arXiv2023

Perturbative BF theory in axial, Anosov, gauge

The twisted Ruelle zeta function of a contact, Anosov vector field is shown to be equal, as a meromorphic function of the complex parameter $\hbar\in\mathbb{C}$ and up to a phase, to the partition function of an $\hbar$-linear quadratic perturbation of $BF$ theory, using an "axial" gauge fixing condition given by the Anosov vector field. Equivalently, it is also obtained as the expectation value of the same quadratic, $\hbar$-linear, perturbation, within a perturbative quantisation scheme for $BF$ theory, suitably generalised to work when propagators have distributional kernels.

math-ph↗
arXiv2023

BV equivalence with boundary

An extension of the notion of classical equivalence of equivalence in the Batalin--(Fradkin)--Vilkovisky (BV) and (BFV) framework for local Lagrangian field theory on manifolds possibly with boundary is discussed. Equivalence is phrased in both a strict and a lax sense, distinguished by the compatibility between the BV data for a field theory and its boundary BFV data, necessary for quantisation. In this context, the first- and second-order formulations of non-Abelian Yang--Mills and of classical mechanics on curved backgrounds, all of which admit a strict BV-BFV description, are shown to be pairwise equivalent as strict BV-BFV theories. This in particular implies that their BV-complexes are quasi-isomorphic. Furthermore, Jacobi theory and one-dimensional gravity coupled with scalar matter are compared as classically-equivalent reparametrisation-invariant versions of classical mechanics, but such that only the latter admits a strict BV-BFV formulation. They are shown to be equivalent as lax BV-BFV theories and to have isomorphic BV cohomologies. This shows that strict BV-BFV equivalence is a strictly finer notion of equivalence of theories.

math-ph↗
arXiv2023

A Lie-Rinehart algebra in general relativity

We construct a Lie-Rinehart algebra over an infinitesimal extension of the space of initial value fields for Einstein's equations. The bracket relations in this algebra are precisely those of the constraints for the initial value problem. The Lie-Rinehart algebra comes from a slight generalization of a Lie algebroid in which the algebra consists of sections of a sheaf rather than a vector bundle. (An actual Lie algebroid had been previously constructed by Blohmann, Fernandes, and Weinstein over a much larger extension.) The construction uses the BV-BFV (Batalin-Fradkin-Vilkovisky) approach to boundary value problems, starting with the Einstein equations themselves, to construct an $L_\infty$-algebroid over a graded manifold which extends the initial data. The Lie-Rinehart algebra is then constructed by a change of variables. One of the consequences of the BV-BFV approach is a proof that the coisotropic property of the constraint set follows from the invariance of the Einstein equations under space-time diffeomorphisms.

math-ph↗
arXiv2021

General Relativity and the AKSZ construction

In this note the AKSZ construction is applied to the BFV description of the reduced phase space of the Einstein-Hilbert and of the Palatini--Cartan theories in every space-time dimension greater than two. In the former case one obtains a BV theory for the first-order formulation of Einstein--Hilbert theory, in the latter a BV theory for Palatini--Cartan theory with a partial implementation of the torsion-free condition already on the space of fields. All theories described here are BV versions of the same classical system on cylinders. The AKSZ implementations we present have the advantage of yielding a compatible BV-BFV description, which is the required starting point for a quantization in presence of a boundary.

math-ph↗
arXiv2021

Kähler fibrations in quantum information theory

We discuss the fibre bundle of co-adjoint orbits of compact Lie groups, and show how it admits a compatible Kähler structure. The case of the unitary group allows us to reformulate the geometric framework of quantum information theory. In particular, we show that the Fisher information tensor gives rise to a structure that is sufficiently close to a Kähler structure to generalise some classical result on co-adjoint orbits.

math-ph↗
arXiv2021

Boundary structure of General Relativity in tetrad variables

An explicit, geometric description of the first-class constraints and their Poisson brackets for gravity in the Palatini-Cartan formalism (in space-time dimension greater than three) is given. The corresponding Batalin- Fradkin-Vilkovisky (BFV) formulation is also developed.

math-ph↗
arXiv2020

Generalized Spontaneous Symmetry Breaking

We propose a new type of symmetry breaking mechanism that takes boundaries into account, and show how it can detect surface modes by interpreting them as the order parameter associated with a generalized symmetry breaking. We argue that this mechanism is analogous to, and yet distinct from, the standard Ginzburg-Landau scenarios, and show how the two communicate through the specification of boundary conditions.

cond-mat.mtrl-sci↗