Postdoctoral Researcher in Theoretical Physics
My research focuses on gravitational theory from the viewpoint of differential geometry. I also have experience working in the private sector as a consultant at a big four firm, a systems engineer at an automotive company, and a production worker at a camera manufacturer. I love nature: forests, mountains, lakes, the sea, and the universe...
General relativity; Metric-affine gravity; Gauge theories of gravity; Modified/Extended theories of graivty; Quantum gravity; Geometric method for physics; Artificial Intelligence (AI) for physics.
My research aims to formulate Metric-Affine Gravity from the perspective of Gauge Theories of Gravity. In General Relativity, spacetime is described by a pseudo-Riemannian manifold, and gravitational effects are encoded in its curvature. However, from the perspective of more general differential geometry, torsion and non-metricity can also be considered in addition to curvature. Theories describing gravity in terms of curvature and torsion have long been studied within the framework of Poincaré Gauge Theories of Gravity. (For an introduction to Gauge Theories of Gravity, see Blagojević and Hehl. For a comprehensive review of Metric-Affine Gravity, see Hehl et al..) On the other hand, how to incorporate non-metricity into the framework of Gauge Theories of Gravity remains an open question. One reason is that non-metricity vanishes when the internal metric is fixed to the Minkowski metric and the connection is restricted to be Lorentz-algebra-valued. This suggests that the internal symmetries and the structure of the connection need to be reconsidered in order to understand the Geometrical Trinity of Gravity (, in detail, see Beltrán Jiménez, Heisenberg, and Koivisto,Universe 5 (2019) 173, ) in a unified manner from the perspective of Gauge Theories of Gravity. My research explores how gravity based on non-metricity can be consistently incorporated into the framework of the Geometrical Trinity of Gravity using Gauge Theories of Gravity. The Introduction begins with a brief introduction to General Relativity, Gauge Theories of Gravity, and Metric-Affine Gravity, and then invites readers to explore my research.
Kyosuke Tomonari,
``Schwarzschild spacetime in STEGR with information geometry'', in preparation for submission.
To be appeared in some preprint server (the manuscript currently very suffers from arXiv's moderation check).
Abstract:
We construct Schwarzschild spacetime within our information-geometric formulation of Symmetric Teleparallel Equivalent to General Relativity (STEGR) and investigate a possible probabilistic interpretation of its spatial geometry.
First, after reviewing $\alpha$-geometry based on Markov embeddings and introducing STEGR as an information-geometric theory, we reformulate this theory using the Arnowitt-Deser-Misner formalism, in which spacetime is foliated by three-dimensional spatial leaves endowed with Hessian structures.
In this formulation, we introduce the three-dimensional probability simplex $\mathcal{S}_{3}$ to provide a statistical description of the spatial leaves.
We then formulate conditions for preserving the Markov invariance of $(0,2)$- and $(0,3)$-tensors, which correspond, respectively, to the Fisher metric and the Amari-Chentsov tensor in a specific case during ADM evolution, together with field equations describing spatial leaves and their time evolution.
Solving this system in the static vacuum case, we reconstruct Schwarzschild spacetime.
In particular, we derive an explicit Hessian potential yielding a positive-definite spatial metric in the Schwarzschild exterior region.
Finally, we discuss the relations among the underlying geometries and the possibility of endowing the spatial leaves with a probabilistic character, and derive the explicit form of the Bregman divergence of the spatial leaves of Schwarzschild spacetime.
e-Print (Tentative): View in Gdrive
(This manuscript has not yet been publicly announced.
If you are interested in reading it, please contact me by email to request access.
The contact information is given at the end of this page.
The manuscript is available for online viewing only and cannot be downloaded or redistributed.
A publicly accessible preprint will be provided once it becomes available.)
Kyosuke Tomonari,
``STEGR with information geometry'',
Accepted for publication in the Special Issue ``Geometric Aspects of Gravity'',
edited by Lead Guest Editor Prof. Alexey Golovnev and Co-Guest Editors Prof. Maria Jose Guzman and Prof. Suddhasattwa Brahma,
in Progress in High Energy Physics.
e-Print: Jxiv:5821
Kyosuke Tomonari, Daniel Blixt, and Sebastian Bahamonde,
``Gauge-invariant cosmological perturbation in Type 3 New General Relativity and background-hierarchy bound'', Under Review.
e-Print: arXiv:2605.16869
Kyosuke Tomonari, Taishi Katsuragawa, Shin'ichi Nojiri,
``Cosmological perturbation in New General Relativity: propagating mode from the violation of local Lorentz invariance''
Published in: Chin.Phys.C 50 (2026) 6, 065105.
e-Print: arXiv:2509.18772
Kyosuke Tomonari, Taishi Katsuragawa, Shin'ichi Nojiri,
``Revisiting coincident GR in internal STEGR formulation''
Published in: Eur.Phys.J.C 86 (2026) 8, 913.
e-Print: arXiv:2506.22158
Kyosuke Tomonari,
``Degrees of freedom of new general relativity: Type 4, Type 7, and Type 9''
Published in: Phys.Lett.B 875 (2026) 140310.
e-Print: arXiv:2411.11118
Kyosuke Tomonari and Daniel Blixt,
``Degrees of freedom of new general relativity: Type 2, Type 3, Type 5, and Type 8''
Published in: Phys.Rev.D 112 (2025) 8, 084052.
e-Print: arXiv:2410.15056
Kyosuke Tomonari,
``STEGR in internal-space formulation: Formalisms, primary constraints, and possible internal symmetries''
Published in: J.Math.Phys. 66 (2025) 5, 052505.
e-Print: arXiv:2410.04848
Kyosuke Tomonari,
``A unified-description of curvature, torsion, and non-metricity of the metric-affine geometry with the M\"{o}bius representation''
Published in: Int.J.Geom.Meth.Mod.Phys. 22 (2025) 05, 2450333.
e-Print: arXiv:2312.11558
Kyosuke Tomonari and Sebastian Bahamonde,
``Dirac--Bergmann analysis and degrees of freedom of coincident f(Q)-gravity''
Published in: Eur.Phys.J.C 84 (2024) 4, 349, Eur.Phys.J.C 84 (2024) 5, 508 (erratum).
e-Print: arXiv:2308.06469
Kyosuke Tomonari,
``On the well-posed variational principle in degenerate point particle systems using embeddings of the symplectic manifold''
Published in: PTEP 2023 (2023) 6, 063A05.
e-Print: arXiv:2304.00877
Keisuke Izumi, Keigo Shimada, Kyosuke Tomonari, and Masahide Yamaguchi,
``Boundary conditions for constraint systems in variational principle''
Published in: PTEP 2023 (2023) 10, 103E03.
e-Print: arXiv:2303.03805
Daniel Blixt, Kyosuke Tomonari, and Sebastian Bahamonde,
``Renewed hope in new general relativity with boost violation'',
GeomGravX: 10 Years of Geometric Foundations of Gravity and eXtensions, June 30, 2026, poster talk.
Kyosuke Tomonari,
``Symmetry in metric-affine gauge theories of gravity toward phenomenology'',
Central China Normal University, May 22, 2025, invited talk.
Kyosuke Tomonari,
``Applications of Dirac--Bergmann analysis to Teleparallel Gravity Theories and Recent status'',
Annual Conference in the Physical Society of Japan, September 16, 2024, contributed talk.
Kyosuke Tomonari and Sebastian Bahamonde,
``Dirac--Bergmann analysis and degrees of freedom of coincident f(Q)-gravity'',
Kanto-region Joint Seminar, October 18, 2023, Invited talk.
Kyosuke Tomonari,
``On the well-posed variational principle in degenerate point particle systems using embeddings of the symplectic manifold'',
Annual conference in the Physical Society of Japan, September 18, 2023, contributed talk.
Kyosuke Tomonari and Sebastian Bahamonde,
``Dirac--Bergmann analysis and Degrees of Freedom of f(Q)-gravity'',
CAS-JSPS-IBS CTPU-CGA 2023 Summer Workshop on Cosmology, Gravity, and Particle Physics, August 29, 2023, contributed talk.
Kyosuke Tomonari, Keigo Shimada, Keisuke Izumi, Masahide Yamaguchi,
``On boundary conditions for variational principle'',
Spring Meeting in the Physical Society of Japan, March 22, 2023, contributed talk.
Kyosuke Tomonari,
``A holographic structure in gravitational action functionals motivated by general covariance'',
Joint workshop on General Relativity and Cosmology (JGRC), March 14, 2023, contributed talk.
Kyosuke Tomonari,
``The geometrical trinity of gravity, degrees of freedom and symmetry breaking'',
Summer CAS-JSPS workshop in cosmology, gravitation and particle physics, August 31, 2022, contributed talk.
Email: ktomonari.phys[at]gmail.com
Please replace [at] with @.