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Mikhail Markov

Publications and source records attributed to Mikhail Markov.

3 recordsLinked to original sources

Asymptotic boundary structure of Lagrangian gauge theories

Given a local gauge theory on spacetime with boundary, it naturally defines another gauge theory which can be regarded as a theory of the boundary values. For Lagrangian theories, it comes equipped with the presymplectic structure which can be used to define one or another version of Hamiltonian-like formulation of the initial model. This relation is especially manifest for AKSZ sigma models and more-generally gauge PDEs with compatible presymplectic structure in which case the boundary system is again a gauge PDE with presymplectic structure. In the context of (flat space) holography one is interested in boundaries at infinity, also known as asymptotic boundaries. The gauge PDE framework naturally extends to this setup, resulting in the notion of gauge PDE with asymptotic boundaries. Although this works perfectly well at the level of equations of motion, the extension to Lagrangian systems appears quite subtle because the presymplectic structure capturing the Lagrangian is divergent at the boundary. We show that any $Q$-cocycle in the bulk (and presymplectic structure in particular) determines a pair of compatible $Q$-cocycles of the boundary gauge PDE: the renormalized one of the same ghost-degree, and the anomaly cocycle of degree one lower. For the latter, the construction is somewhat analogous to the residue map known in the context of b-geometry. The general formalism is exemplified by scalar and Maxwell fields on AdS and Minkowski spaces. It turns out that in the AdS case the natural action determined by the anomaly presymplectic structure is precisely the one known as the holographic Weyl anomaly in the AdS/CFT context while its null-infinity counterpart was known in a few very particular cases only.

hep-th

Boundary structure of gauge fields on asymptotically AdS spaces

We study the boundary structure of asymptotically AdS gravity and (gauge) fields defined on this background by employing the gauge PDE approach. The essential step of the construction is the incorporation of the boundary-defining function among the fields of the theory, which allows us to realise the asymptotic boundary as a space-time submanifold by employing the gauge PDE implementation of Penrose's concept of asymptotically-simple space. In so doing the gauge PDE describing the boundary structure is obtained by restricting to the boundary of spacetime and simultaneously restricting to the boundary of the field space by setting the boundary defining function to zero. To implement this step systematically we introduce a notion of $Q$-boundary which seems to be new. The main concrete result of this work is the construction of an efficient boundary calculus, which gives a recursive procedure to obtain the explicit form of the equations satisfied by the boundary fields and their gauge transformations for boundary dimension $d \geq 3$. These include obstruction equations (such as Bach equation or Yang-Mills equation for $d=4$) and generalised conservation equations in the subleading sector. In particular, we derive the explicit form of the higher conformal Yang-Mills equation for $d=8$. The approach is very general and, in principle, applies to generic (gauge) fields on the Einstein gravity background producing a conformally-invariant gauge theory on the boundary, which describes their boundary structure. It can be considered an extension of the Fefferman-Graham construction, which takes into account both the leading and subleading sectors of the bulk fields.

math-ph

Asymptotic symmetries of gravity in the gauge PDE approach

We propose a framework to study local gauge theories on manifolds with boundaries and asymptotic symmetries, which is based on representing them as so-called gauge PDEs. These objects extend the conventional BV-AKSZ sigma-models to the case of not necessarily topological and diffeomorphism invariant systems and are known to behave well with respect to restrictions to submanifolds and boundaries. We introduce the notion of gauge PDE with boundaries, which takes into account generic boundary conditions, and apply the framework to asymptotically flat gravity. In so doing we start with a suitable representation of gravity as a gauge PDE with boundaries which implements the Penrose's description of asymptotically simple spacetimes. We then derive the minimal model of the gauge PDE induced on the boundary and observe that it provides the Cartan (frame-like) description of a (curved) conformal Carollian structure on the boundary. Furthermore, imposing a suitable version of the familiar boundary conditions in the induced boundary gauge PDE immediately leads to the conventional BMS algebra of asymptotic symmetries. Finally, we briefly sketch the construction in the case of asymptotically (A)dS gravity.

math-ph