Leonid Petrov
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View article: Dim cores of radio-bright AGN jets: VLBI and <i>Gaia</i> astrometry pinpoint different parsec-scale features
Dim cores of radio-bright AGN jets: VLBI and <i>Gaia</i> astrometry pinpoint different parsec-scale features Open
Astrometry with the very long baseline radio interferometry (VLBI) allows to determine the position of a point close to the source’s brightest compact detail at milliarcsecond scales. For most active galactic nuclei (AGNs), this compact de…
View article: A unified model of feed rotation in radio telescopes and GNSS antennas
A unified model of feed rotation in radio telescopes and GNSS antennas Open
We describe a model that accounts for the phase rotation that occurs when a receiver or transmitter changes orientation while observing or emitting circularly polarized electromagnetic waves. This model extends work detailing Global Naviga…
View article: A unified model of feed rotation in radio telescopes and GNSS antennas
A unified model of feed rotation in radio telescopes and GNSS antennas Open
We describe a model that accounts for the phase rotation that occurs when a receiver or transmitter changes orientation while observing or emitting circularly polarized electromagnetic waves. This model extends work detailing Global Naviga…
View article: Hierarchical Lexical Manifold Projection in Large Language Models: A Novel Mechanism for Multi-Scale Semantic Representation
Hierarchical Lexical Manifold Projection in Large Language Models: A Novel Mechanism for Multi-Scale Semantic Representation Open
The integration of structured hierarchical embeddings into transformer-based architectures introduces a refined approach to lexical representation, ensuring that multi-scale semantic relationships are preserved without compromising computa…
View article: The Radio Fundamental Catalog. I. Astrometry
The Radio Fundamental Catalog. I. Astrometry Open
We present an all-sky catalog of absolute positions and estimates of correlated flux density of 21,942 compact radio sources determined from processing interferometric visibility data of virtually all very long baseline interferometry (VLB…
View article: Extracting Geodetic Data from GNSS-VLBI Co-Observation
Extracting Geodetic Data from GNSS-VLBI Co-Observation Open
We have been developing a novel interferometer formed directly between a Very Long Baseline Interferometry (VLBI) radio telescope and a Global Navigation Satellite Systems (GNSS) antenna/receiver. This interferometer is enabled by the High…
View article: The Radio Fundamental Catalogue. I. Astrometry
The Radio Fundamental Catalogue. I. Astrometry Open
We present an all-sky catalog of absolute positions and estimates of correlated flux density of 21,942 compact radio sources determined from processing interferometric visibility data of virtually all very long baseline interferometry (VLB…
View article: A millisecond pulsar position determined to 0.2 mas precision with VLBI
A millisecond pulsar position determined to 0.2 mas precision with VLBI Open
Context . Precise millisecond pulsar (MSP) positions determined with very long baseline interferometry (VLBI) hold the key to building the connection between the kinematic and dynamic reference frames respectively used for VLBI and pulsar …
View article: Hook-length Formulas for Skew Shapes via Contour Integrals and Vertex Models
Hook-length Formulas for Skew Shapes via Contour Integrals and Vertex Models Open
The number of standard Young tableaux of a skew shape $λ/μ$ can be computed as a sum over excited diagrams inside $λ$. Excited diagrams are in bijection with certain lozenge tilings, with flagged semistandard tableaux and also nonintersect…
View article: Grothendieck Shenanigans: Permutons from pipe dreams via integrable probability
Grothendieck Shenanigans: Permutons from pipe dreams via integrable probability Open
We study random permutations arising from reduced pipe dreams. Our main model is motivated by Grothendieck polynomials with parameter $β=1$ arising in K-theory of the flag variety. The probability weight of a permutation is proportional to…
View article: A millisecond pulsar position determined to 0.2 milliarcsecond precision with VLBI
A millisecond pulsar position determined to 0.2 milliarcsecond precision with VLBI Open
Precise millisecond pulsar (MSP) positions determined with very long baseline interferometry (VLBI) hold the key to building the connection between the kinematic and dynamic reference frames respectively used by VLBI and pulsar timing. The…
View article: Radio Astrometry at Different Frequencies
Radio Astrometry at Different Frequencies Open
The very long baseline interferometry technique allows us to determine the positions of thousands of radio sources using the absolute astrometry approach. I have investigated the impacts of a selection of observing frequencies in a range f…
View article: The Black Hole Explorer: operating a hybrid observatory
The Black Hole Explorer: operating a hybrid observatory Open
We present a baseline science operations plan for the Black Hole Explorer\n(BHEX), a space mission concept aiming to confirm the existence of the\npredicted sharp ``photon ring" resulting from strongly lensed photon\ntrajectories around bl…
View article: The Black Hole Explorer: Operating a Hybrid Observatory
The Black Hole Explorer: Operating a Hybrid Observatory Open
We present a baseline science operations plan for the Black Hole Explorer (BHEX), a space mission concept aiming to confirm the existence of the predicted sharp ``photon ring" resulting from strongly lensed photon trajectories around black…
View article: Tilted biorthogonal ensembles, Grothendieck random partitions, and determinantal tests
Tilted biorthogonal ensembles, Grothendieck random partitions, and determinantal tests Open
We study probability measures on partitions based on symmetric Grothendieck polynomials. These deformations of Schur polynomials introduced in the K-theory of Grassmannians share many common properties. Our Grothendieck measures are analog…
View article: Tilted biorthogonal ensembles, Grothendieck random partitions, and determinantal tests
Tilted biorthogonal ensembles, Grothendieck random partitions, and determinantal tests Open
We study probability measures on partitions based on symmetric Grothendieck polynomials. These deformations of Schur polynomials introduced in the K-theory of Grassmannians share many common properties. Our Grothendieck measures are analog…
View article: <i>RadioAstron</i>discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84
<i>RadioAstron</i>discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84 Open
We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C 84 (NGC 1275) at the centre of the Perseus cluster. The observations were carried out during a perigee passage of the Sp…
View article: First observations with a GNSS antenna to radio telescope interferometer
First observations with a GNSS antenna to radio telescope interferometer Open
We describe the design of a radio interferometer composed of a Global Navigation Satellite Systems (GNSS) antenna and a Very Long Baseline Interferometry (VLBI) radio telescope. Our eventual goal is to use this interferometer for geodetic …
View article: Single-band VLBI Absolute Astrometry
Single-band VLBI Absolute Astrometry Open
The ionospheric path delay impacts single-band, very long baseline interferometry (VLBI) group delays, which limits their applicability for absolute astrometry. I consider two important cases: when observations are made simultaneously in t…
View article: Asymptotics of noncolliding q-exchangeable random walks
Asymptotics of noncolliding q-exchangeable random walks Open
We consider a process of noncolliding $q$-exchangeable random walks on $\mathbb{Z}$ making steps $0$ (straight) and $-1$ (down). A single random walk is called $q$-exchangeable if under an elementary transposition of the neighboring steps …
View article: VGOS VLBI Intensives between MACGO12M and WETTZ13S for the rapid determination of UT1-UTC
VGOS VLBI Intensives between MACGO12M and WETTZ13S for the rapid determination of UT1-UTC Open
In this work, we present a status update and results of the designated research and development VLBI Intensive program VGOS-INT-S, observed between MACGO12M and WETTZ13S for the rapid determination of the Earth's phase of rotation, express…
View article: Precise VLBI/GNSS ties with micro-VLBI
Precise VLBI/GNSS ties with micro-VLBI Open
We present here a concept of measuring local ties between collocated GNSS and VLBI stations using the microwave technique that effectively transforms a GNSS receiver to an element of a VLBI network. This is achieved by modifying the signal…
View article: Irreversible Markov dynamics and hydrodynamics for KPZ states in the stochastic six vertex model
Irreversible Markov dynamics and hydrodynamics for KPZ states in the stochastic six vertex model Open
We introduce a family of Markov growth processes on discrete height functions defined on the 2-dimensional square lattice. Each height function corresponds to a configuration of the six vertex model on the infinite square lattice. We focus…
View article: VGOS VLBI Intensives Between macgo12m and wettz13s for the Rapid Determination of UT1-UTC
VGOS VLBI Intensives Between macgo12m and wettz13s for the Rapid Determination of UT1-UTC Open
In this work, we present a status update and preliminary results of the designated research and development VLBI Intensive program VGOS-INT-S, observed between macgo12m and wettz13s for the rapid determination of the Earth’s phase of rotat…
View article: A Concept of Precise VLBI/GNSS Ties with Micro-VLBI
A Concept of Precise VLBI/GNSS Ties with Micro-VLBI Open
We present here a concept of measuring local ties between collocated GNSS and VLBI stations using the microwave technique that effectively transforms a GNSS receiver to an element of a VLBI network. This is achieved by modifying the signal…
View article: Rewriting History in Integrable Stochastic Particle Systems
Rewriting History in Integrable Stochastic Particle Systems Open
Many integrable stochastic particle systems in one space dimension (such as TASEP - Totally Asymmetric Simple Exclusion Process - and its $q$-deformation, the $q$-TASEP) remain integrable if we equip each particle with its own speed parame…
View article: Single band VLBI absolute astrometry
Single band VLBI absolute astrometry Open
The ionospheric path delay impacts single-band very long baseline interferometry (VLBI) group delays, which limits their applicability for absolute astrometry. I consider two important cases: when observations are made simultaneously at tw…
View article: Noncolliding Macdonald Walks with an Absorbing Wall
Noncolliding Macdonald Walks with an Absorbing Wall Open
The branching rule is one of the most fundamental properties of the Macdonald symmetric polynomials. It expresses a Macdonald polynomial as a nonnegative linear combination of Macdonald polynomials with smaller number of variables. Taking …
View article: Noncolliding Macdonald Walks with an Absorbing Wall
Noncolliding Macdonald Walks with an Absorbing Wall Open
The branching rule is one of the most fundamental properties of the Macdonald symmetric polynomials. It expresses a Macdonald polynomial as a nonnegative linear combination of Macdonald polynomials with smaller number of variables. Taking …
View article: Irreversible Markov Dynamics and Hydrodynamics for KPZ States in the Stochastic Six Vertex Model
Irreversible Markov Dynamics and Hydrodynamics for KPZ States in the Stochastic Six Vertex Model Open
We introduce a family of Markov growth processes on discrete height functions defined on the 2-dimensional square lattice. Each height function corresponds to a configuration of the six vertex model on the infinite square lattice. We focus…