arXiv subjects

Andrei Mikhailov

Publications and source records attributed to Andrei Mikhailov.

At least 19 recordsLinked to original sources

arXiv2026

MARS: Multi-Specialist LLM Relay System for Competitive Programming

Large Language Models excel at code generation, yet competitive programming exposes a persistent failure mode: existing multi-agent pipelines distribute work over generic planner, coder, and debugger roles and delegate the choice of algorithmic technique to the backbone alone. We present MARS (Multi-Agent Relay of Specialized LLMs), a prompt-only framework in which each agent is a topic specialist---dynamic programming, graphs, strings, geometry, and so on---grounded by retrieval-augmented generation over an algorithm-theory corpus. Given a problem, retrieval selects a small team of relevant specialists; a starter writes an initial C++17 solution, and each subsequent turn runs the candidate against public examples in a sandbox, lets the active specialist keep, repair, or hand off the draft, and forwards a structured packet to the next specialist. A single infrastructure-fixer pass normalizes boilerplate at the end. On the CodeContests test split with Gemma 4, MARS reaches $0.624 \pm 0.006$ pass rate at $2.3$ recorded pipeline stages per task ($+14.4$ percentage points over direct prompting), closing most of the gap to CodeSIM ($0.731$) at $3.3{\times}$ lower wall-clock cost and substantially smaller variance in per-task token spend. The source code is available on GitHub: https://github.com/fckand/mars.

cs.AI↗

arXiv2026

Supersymmetry bicomplex of pure spinor AdS background

Infinitesimal deformations of $\text{AdS}_5 \times \mathbb{S}^5$ form a representation of the AdS supersymmetry algebra. The structure of this representation has not yet been completely described in the literature. Some information can be obtained just from the fact that the space of deformations is the cohomology of a nilpotent BRST operator. We can consider the bicomplex formed by the BRST operator and the Lie cohomology differential, and its two spectral sequences. Their matching imposes some constraints on the structure of representations, which we start exploring in this paper. In particular, we clarify the structure of ghost number three zero modes.

hep-th↗

arXiv2025

B-RNS-GSS formalism and $L_{\infty}$-actions

Pure spinor formalism and RNS formalism are related by a chain of equivalences constructed by introducing and integrating-out BRST quartets. This is known as B-RNS-GSS formalism. The first step is to add BRST quartets to the RNS model and do a similarity transformation on the space of fields. We show that this step can be understood as a strictification procedure which lifts a strong homotopy action of the supersymmetry algebra to a quasiisomorphic strict action. This observation allows us to clarify the details of the B-RNS-GSS derivation. We obtain a closed formula for the similarity transformation as a path-ordered exponential, and derive the supersymmetric currents.

hep-th↗

arXiv2024

Deformations of AdS and exact sequences

We give examples of cohomologies of the superconformal algebra, relevant to computations in the AdS supergravity. Our main examples are deformations of $AdS_5\times S^5$ transforming in finite-dimensional representations of the superconformal algebra at the linearized level. In the study of correlation functions, it is important to compute the resolution of BRST-exact products of vertex operators. The resolution is typically non-covariant, because of cohomological obstacles. Using the pure spinor formalism, we develop a framework to describe these obstacles, and formulate conjectures about their structure.

hep-th↗

arXiv2024

Yang-Mills algebra and symmetry transformations of vertex operators

Linearized solutions of SUGRA equations of motion are described in the pure spinor formalism by vertex operators. Under supersymmetry transformations, they transform covariantly only up to BRST exact terms. We identify the cohomology class which is the obstacle for exact covariance. Computations are simplified by using the formalism of quadratic algebras.

hep-th↗

arXiv2024

Transformations of Currents in Sigma-Models with Target Space Supersymmetry

We develop a framework for systematic study of symmetry transformations of sigma-model currents in a special situation, when symmetries have a well-defined projection onto the target space. We then apply this formalism to pure spinor sigma-models, and describe the resulting geometric structures in the target space (which in our approach includes the pure spinor ghosts). We perform a detailed study of the transformation properties of currents, using the formalism of equivariant cohomology. We clarify the descent procedure for the ''universal'' deformation corresponding to changing the overall scale of the worldsheet action. We also study the contact terms in the OPE of BRST currents, and derive some relations between currents and vertex operators which perhaps have not been previously acknowledged. We also clarify the geometrical meaning of the ''minimalistic'' BV action for pure spinors in AdS.

hep-th↗

arXiv2023

Insertion of vertex operators using BV formalism

We develop a general framework for the insertion of vertex operator on the string worldsheet, in BV formalism. Such insertions correspond to deformations of the Master Action which breaks the gauge symmetry to a subgroup, and then restoring the full gauge symmetry by integrating over a cycle in the space of Lagrangian submanifolds. We provide the general construction, global on the moduli space, which was previously conjectured in a form local on the worldsheet. We explain how the enhancement of the gauge symmetry in equivariant BV formalism can be seen as an application of the general idea of BV effective action. We derive an integral formula for the deformation of the contraction operator due to the vertex insertion.

hep-th↗

arXiv2022

Normal form of nilpotent vector field near the tip of the pure spinor cone

Pure spinor formalism implies that supergravity equations in space-time are equivalent to the requirement that the worldsheet sigma-model satisfies certain properties. Here we point out that one of these properties has a particularly transparent geometrical interpretation. Namely, there exists an odd nilpotent vector field on some singular supermanifold, naturally associated to space-time. All supergravity fields are encoded in this vector field, as coefficients in its normal form. The nilpotence implies, modulo some zero modes, that they satisfy the SUGRA equations of motion.

hep-th↗

arXiv2021

Derived brackets in bosonic string worldsheet sigma-model

We study the worldsheet theory of bosonic string from the point of view of the BV formalism. We explicitly describe the derived Poisson structure which arizes when we expand the Master Action near a Lagrangian submanifold. The BV formalism allows us to clarify the mechanism of holomorphic factorization of string amplitudes.

hep-th↗

arXiv2021

A minimalistic pure spinor sigma-model in AdS

The $b$-ghost of the pure spinor formalism in a general curved background is not holomorphic. For such theories, the construction of the string measure requires the knowledge of the action of diffeomorphisms on the BV phase space. We construct such an action for the pure spinor sigma-model in $AdS_5\times S^5$. From the point of view of the BV formalism, this sigma-model belongs to the class of theories where the expansion of the Master Action in antifields terminates at the quadratic order. We show that it can be reduced to a simpler degenerate sigma-model, preserving the AdS symmetries. We construct the action of the algebra of worldsheet vector fields on the BV phase space of this minimalistic sigma-model, and explain how to lift it to the original model.

hep-th↗

arXiv2020

DGLA Dg and BV formalism

Differrential Graded Lie Algebra Dg was previously introduced in the context of current algebras. We show that under some conditions, the problem of constructing equivariantly closed form from closed invariant form is reduces to construction of a representation of Dg. This includes equivariant BV formalism. In particular, an analogue of intertwiner between Weil and Cartan models allows to clarify the general relation between integrated and unintegrated vertex operators in string worldsheet theory.

hep-th↗

arXiv2020

Geometrical framework for picture changing operators in the pure spinor formalism

It is well known in NSR string theory, that vertex operators can be constructed in various ``pictures''. Recently this was discussed in the context of pure spinor formalism. NSR picture changing operators have an elegant super-geometrical interpretation. In this paper we provide a generalization of this super-geometrical construction, which is also applicable to the pure spinor formalism.

hep-th↗

arXiv2019

Deformations, renormgroup, symmetries, AdS/CFT

We consider the deformations of a supersymmetric quantum field theory by adding spacetime-dependent terms to the action. We propose to describe the renormalization of such deformations in terms of some cohomological invariants, a class of solutions of a Maurer-Cartan equation. We consider the strongly coupled limit of $N=4$ supersymmetric Yang-Mills theory. In the context of AdS/CFT correspondence, we explain what corresponds to our invariants in classical supergravity. There is a leg amputation procedure, which constructs a solution of the Maurer-Cartan equation from tree diagramms of SUGRA. We consider a particular example of the beta-deformation. It is known that the leading term of the beta-function is cubic in the parameter of the beta-deformation. We give a cohomological interpretation of this leading term. We conjecture that it is actually encoded in some simpler cohomology class, which is quadratic in the parameter of the beta-deformation.

hep-th↗

arXiv2019

Observations of radio sources near the Sun

Geodetic Very Long Baseline Interferometry (VLBI) data are capable of measuring the light deflection caused by the gravitational field of the Sun and large planets with high accuracy. The parameter $γ$ of the parametrized Post-Newtonian (PPN) formalism estimated using observations of reference radio sources near the Sun should be equal to unity in the general relativity. We have run several VLBI experiments tracking reference radio sources from 1 to 3 degrees from the Sun. The best formal accuracy of the parameter $γ$ achieved in the single-session mode is less than 0.01 percent, or better than the formal accuracy obtained with a global solution included all available observations at arbitrary elongation from the Sun. We are planning more experiments starting from 2020 using better observing conditions near the minimum of the Solar activity cycle.

astro-ph.IM↗

arXiv2019

On worldsheet curvature coupling in pure spinor sigma-model

We discuss the relation between unintegrated and integrated vertex operators in string worldsheet theory, in the context of BV formalism. In particular, we clarify the origin of the Fradkin-Tseytlin term. We first consider the case of bosonic string, and then concentrate on the case of pure spinor superstring in $AdS_5\times S^5$. In particular, we compute the action of $b_0 - \bar{b}_0$ on the beta-deformation vertex. As a by-product, we formulate some new conjectures on general finite-dimensional vertices.

hep-th↗

arXiv2018

A geometrical point of view on linearized beta-deformations

It is known that the supermultiplet of beta-deformations of ${\cal N}=4$ supersymmetric Yang-Mills theory can be described in terms of the exterior product of two adjoint representations of the superconformal algebra. We present a super-geometrical interpretation of this fact, by evaluating the deforming operator on some special coherent states in the space of supersingletons. We also discuss generalization of this approach to other finite-dimensional deformations of the ${\cal N}=4$ supersymmetric Yang-Mills theory.

hep-th↗

arXiv2018

Testing General Relativity with geodetic VLBI: what profit from a single, specially designed experiment?

Context. We highlight the capabilities of the geodetic VLBI technique to test General relativity in the classical astrometric style, i.e., measuring the deflection of light in the vicinity of the Sun. Aims. In previous studies, the parameter was estimated by global analyses of thousands of geodetic VLBI sessions. Here we estimate from a single session where the Sun has approached two strong reference radio sources 0229+131 and 0235+164 at an elongation angle of 1-3 degrees. Methods. The AUA020 VLBI session of 1 May 2017 was designed to obtain more than 1000 group delays from the two radio sources. The Solar corona effect was effectively calibrated with the dual-frequency observations even at small elongation from the Sun. Results. We obtained with a precision better than what is obtained through global analyses of thousands of standard geodetic sessions over decades. Current results demonstrate that the modern VLBI technology is capable of establishing new limits on observational test of General Relativity.

astro-ph.IM↗

arXiv2018

Integration over families of Lagrangian submanifolds in BV formalism

Gauge fixing is interpreted in BV formalism as a choice of Lagrangian submanifold in an odd symplectic manifold. A natural construction defines an integration procedure on families of Lagrangian submanifolds. In string perturbation theory, the moduli space integrals of higher genus amplitudes can be interpreted in this way. We discuss the role of gauge symmetries in this construction. We derive the conditions which should be imposed on gauge symmetries for the consistency of our integration procedure. We explain how these conditions behave under the deformations of the worldsheet theory. In particular, we show that integrated vertex operator is actually an inhomogeneous differential form on the space of Lagrangian submanifolds.

hep-th↗