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Fujii, Daisuke; Hosaka, Atsushi*; Iwanaka, Akihiro*; Sakai, Tadakatsu*; Tachibana, Motoi*
Physical Review D, 113(3), p.034003_1 - 034003_17, 2026/03
Times Cited Count：0 Percentile：0.00(Astronomy & Astrophysics)Understanding the behavior of QCD matter under strong coupling remains a difficult task due to its inherently non-perturbative character. In this context, we investigate a two-flavor hard-wall holographic model to explore finite-density QCD at zero temperature, incorporating effects from a nonzero quark mass. The dense matter phase is described by solving the classical equations of motion within a homogeneous ansatz. To establish a connection between the bulk gravity theory and boundary QCD observables, we perform holographic renormalization and formulate the corresponding holographic dictionary. In analyzing the phase structure, we highlight the importance of introducing an IR boundary term at the hard-wall cutoff. Within this setup, we identify a phase of baryonic matter characterized by a large baryon number density and a significantly reduced chiral condensate. We derive the equation of state for this phase and use it to compute the mass-radius relation for neutron stars.
Fujii, Daisuke; Hosaka, Atsushi*; Iwanaka, Akihiro*; Sakai, Tadakatsu*; Tachibana, Motoi*
Proceedings of Science (Internet), 500, p.135_1 - 135_6, 2026/01
Understanding strongly coupled QCD matter remains challenging due to its non-perturbative nature. We study finite-density, zero-temperature QCD in a two-flavor hard-wall holographic model with nonzero quark mass. The dense phase is obtained by solving the classical equations of motion under a homogeneous ansatz. To relate bulk fields to boundary observables, we perform holographic renormalization and construct the dictionary, emphasizing the essential role of an IR boundary term at the hard-wall cutoff. Within this setup we uncover a baryonic phase with large baryon number density and a strongly suppressed chiral condensate. From these solutions we derive the equation of state and compute neutron-star mass-radius relations, finding stars above two solar masses over a broad parameter range.
Fujii, Daisuke; Iwanaka, Akihiro*; Tanaka, Mitsuru*
Physical Review D, 112(9), p.094051_1 - 094051_12, 2025/11
Times Cited Count：0 Percentile：0.00(Astronomy & Astrophysics)In this study, we investigate the internal energy and stress distribution of the pion, as extracted from gravitational form factors within a top-down holographic QCD framework. We demonstrate that the confining pressure inside the pion is also predominantly governed by the QCD scale anomaly, consistent with earlier findings for the nucleon in the instant form, now confirmed in the light-front form for the pion. Furthermore, our analysis shows that, in the large-
limit realized in this holographic setup, the scalar glueball acts as the mediator of the confining pressure. These results provide further evidence for the universal role of the scale anomaly in hadron stability.
Yang-Mills theory in 
Kitazawa, Masakiyo*; Fujii, Daisuke; Iwanaka, Akihiro*; Suenaga, Daiki*
Proceedings of Science (Internet), 466, p.163_1 - 163_9, 2025/02
We examine the thermal properties and phase transitions of Yang-Mills theory formulated on the spacetime manifold , where two spatial directions are compactified. Using both lattice simulations and an effective model, we study the theory in Euclidean space with anisotropic spatial volumes. Our lattice analysis reveals that significant pressure anisotropy appears only when the compactified spatial dimensions are sufficiently short, in contrast to free scalar theories. Based on these results, we construct an effective theory where two Polyakov loops associated with the compactified directions are treated as dynamical degrees of freedom. This model, tuned to match the lattice thermodynamics, predicts a novel first-order phase transition terminating at critical points. Our findings suggest that the coupling between the two Polyakov loops plays a key role in driving this transition.
Fujii, Daisuke; Iwanaka, Akihiro*; Kitazawa, Masakiyo*; Suenaga, Daiki*
Physical Review D, 110(9), p.094016_1 - 094016_16, 2024/11
Times Cited Count：1 Percentile：17.19(Astronomy & Astrophysics)We investigate the thermodynamics and phase structure of Yang-Mills theory on 
in Euclidean spacetime in an effective-model approach. The model incorporates two Polyakov loops along two compactified directions as dynamical variables, and is constructed to reproduce thermodynamics on measured on the lattice. The model analysis indicates the existence of a novel first-order phase transition on in the deconfined phase, which terminates at critical points that should belong to the two-dimensional 
universality class. We argue that the interplay of the Polyakov loops induced by their cross term in the Polyakov-loop potential is responsible for the manifestation of the first-order transition.
Fujii, Daisuke; Iwanaka, Akihiro*; Tanaka, Mitsuru*
Physical Review D, 110(9), p.L091501_1 - L091501_8, 2024/11
Times Cited Count：13 Percentile：88.52(Astronomy & Astrophysics)The gravitational form factors (GFFs) of pions are calculated from a top-down holographic quantum chromodynamics (QCD) approach with momentum transfer dependence for the first time. It is important because the GFFs of hadrons have information on the internal stress distribution that may provide insight into the mechanism of how QCD forms hadrons. The forward limit value of this GFFs, i.e. the D-term, was also obtained. Furthermore, in this approach, we observe the so-called glueball dominance, in which pions have gravitational interactions via infinite glueball spectra.
Fujii, Daisuke; Iwanaka, Akihiro*; Hosaka, Atsushi*
Physical Review D, 106(1), p.014010_1 - 014010_6, 2022/07
Times Cited Count：5 Percentile：36.35(Astronomy & Astrophysics)The Roper resonance, the first excited state of the nucleon, is one of the best established baryon resonates. Yet, its properties have not been consistently explained by effective models of QCD, such as the non-relativistic quark model. In this paper, we propose an alternative approach in the Sakai-Sugimoto model that is one of the holographic models of QCD. In particular, we analyze the helicity amplitude of the electromagnetic transitions at the leading of 't Hooft coupling 
. The model incorporates baryon structure at short distance by nonlinear mesons surrounded by meson clouds at long distance. We demonstrate that the recently observed data by CLAS are explained in the present approach.
(1535) in the holographic QCDIwanaka, Akihiro*; Fujii, Daisuke*; Hosaka, Atsushi
Physical Review D, 105(11), p.114057_1 - 114057_6, 2022/06
Times Cited Count：5 Percentile：36.35(Astronomy & Astrophysics)no abstracts in English
Fujii, Daisuke; Iwanaka, Akihiro*; Suenaga, Daiki*; Kitazawa, Masakiyo*
no journal, ,
We discuss pure Yang-Mills theory with anisotropic boundary conditions on 
manifolds. The lattice QCD results show that anisotropy effects are suppressed until the spatial spread becomes significantly smaller near the critical temperature. We successfully reproduce the thermodynamics of lattice by extending the Polyakov loop model, which describes the usual finite temperature, on with parameters. Furthermore, by considering the physical background, we show that the competition between the two Polyakov loops introduced in the model and the existence of a new first-order phase transition are important.
Fujii, Daisuke; Iwanaka, Akihiro*
no journal, ,
The gravitational form factors of hadrons are form factors that characterize the matrix elements of the energy-momentum tensor and contain information on the stress distribution inside hadrons. Recently, the gravitational form factors of nucleons have been experimentally extracted and the extremely anisotropic behavior of the nucleon interior has been revealed. In this presentation, we present a study of the gravitational form factors of vector mesons using the Sakai-Sugimoto model, which is one of the top-down approaches to holographic QCD. We show the relationship between the hadron stability condition imposed on the forward limit of the gravitational form factors and the glueball spectra.
Fujii, Daisuke; Iwanaka, Akihiro*
no journal, ,
It is useful to investigate the resonant states of nucleons, which are elementary excitations of the QCD vacuum, to further elucidate their properties, since the ground state is governed by flavor symmetry. In this study, we investigate the dynamical properties of nucleon resonances, especially the electromagnetic transition amplitudes and decay processes due to strong interactions, using the Sakai-Sugimoto model, which is a top-down approach to holographic QCD. In addition, the gravitational form factor and the stress distribution obtained from it, which have attracted much attention in recent years, were also investigated using the same approach. As a result, we found an interesting relation between the stability condition for the stress distribution and the glueball spectra.
Fujii, Daisuke; Iwanaka, Akihiro*; Tanaka, Mitsuru*
no journal, ,
Understanding how quarks and gluons are confined inside hadrons is a core challenge in QCD. Internal forces (pressure and shear) are encoded in matrix elements of the energy-momentum tensor (EMT) via gravitational form factors (GFFs). The first experimental extraction of the proton's pressure distribution in 2018 spurred broad interest in probing hadron structure through GFFs. In this talk, we present our recent study of the pion's GFFs using a top-down holographic QCD framework (the Sakai-Sugimoto model). After a concise overview of the model and the mapping of QCD operators from the dual gravity theory, we provide analytical expressions and numerical results for the GFFs. We also discuss "glueball dominance", in which pion-graviton interactions are chiefly mediated by intermediate glueball states.
Fujii, Daisuke; Iwanaka, Akihiro*; Tanaka, Mitsuru*
no journal, ,
The mechanism by which quarks and gluons form hadrons via the strong interaction is not yet fully understood. In recent years, attempts to gain insight into this mechanism through the internal stress distributions of hadrons, extracted from the gravitational form factors that characterize matrix elements of the energy-momentum tensor, attracted increasing attention. In this talk, we compute the stress distribution inside the pion using holographic QCD and, in particular, discuss the origin of the confining pressure that binds quarks and gluons inside the pion.
Fujii, Daisuke; Iwanaka, Akihiro*
no journal, ,
The form factor is an important physical quantity for the elucidation of the internal structure of hadrons because it incorporates information about the internal structure of the extended particles. Recently, the gravitational form factor, which characterizes the matrix element of the energy-momentum tensor, has been experimentally observed, and its theoretical understanding has been attracting much attention. In this presentation, we will present our recent results on the gravitational form factor of vector mesons and the stress distribution obtained from it using the Sakai-Sugimoto model, which is a top-down approach to holographic QCD. We are the first to formulate the gravitational form factor of a vector meson using the Sakai-Sugimoto model. As a result, we succeeded in finding a deep relationship between the stability condition of the stress distribution of the vector meson and the glueball spectra.
Fujii, Daisuke; Iwanaka, Akihiro*
no journal, ,
Gravitational form factors of hadrons characterize the matrix elements of the energy-momentum tensor from which we can extract the pressure and shear force inside hadrons. In recent years, GFFs have been measured experimentally, and it will soon be possible to measure GFFs for hadrons at J-PARC. Before this, in this talk, we will discuss our recent work on pressure, shear force, and the GFFs of vector mesons from holographic QCD.
Fujii, Daisuke; Iwanaka, Akihiro*; Tanaka, Mitsuru*
no journal, ,
We calculated the gravitational form factors (GFFs) of pions, A (t) and D (t), using a top-down holographic QCD approach with momentum transfer dependence. The GFFs of hadrons have attracted attention because they contain information on the internal stress distribution, which may provide insights into the mechanisms of hadron formation by QCD. Our results show that the absolute values of D (t) dumps more rapidly than that of A (t), which are qualitatively consistent with the results of lattice QCD. Furthermore, we obtained the forward limit value of these GFFs, specifically the D-term, which is -1.
Fujii, Daisuke; Iwanaka, Akihiro*; Suenaga, Daiki*; Kitazawa, Masakiyo*
no journal, ,
The Matsubara formalism for the thermal quantum field theory introduces temperature into the theory as a boundary condition along the imaginary time direction of Euclidean spacetime. In this study, we consider the pure Yang-Mills theory on , which further imposes boundary conditions on the spatial direction, and discuss thermodynamic quantities and phase structures. Results from lattice QCD simulations show that anisotropic effects are suppressed until the spatial directional spread becomes significantly smaller near the critical temperature. By constructing the model to reproduce the lattice QCD results, it becomes clear that the system suggests the existence of a very rich phase structure.
Fujii, Daisuke; Iwanaka, Akihiro*; Suenaga, Daiki*; Kitazawa, Masakiyo*
no journal, ,
The Matsubara formalism for the thermal quantum field theory introduces temperature into the theory as a boundary condition along the imaginary time direction of Euclidean spacetime. In this study, we further consider the pure Yang-Mills theory on with boundary conditions in one spatial direction, and discuss thermodynamic quantities and their phase structures. The introducing of the boundary condition leads to the breaking of rotational symmetry, which results in anisotropy of the pressure. Results from lattice QCD simulations show that the anisotropic effect is suppressed until the spatial spread becomes significantly smaller near the critical temperature. This result is a very different behavior from that of free-particle systems. In order to reveal the mechanism behind this result, we employ an effective model with two Polyakov loops along the time and spatial directions. We show that introducing the competition between the two Polyakov loops as suggested in a previous study describes well the lattice data in the high temperature region. Furthermore, we show that a new first-order phase transition is suggested, which is different from the confinement phase transition.
Fujii, Daisuke; Iwanaka, Akihiro*; Hosaka, Atsushi*
no journal, ,
It is useful to investigate the resonant states of nucleons, which are elementary excitations of the QCD vacuum, to further elucidate their properties, because the ground state is dominated by the flavor symmetry. In this study, we investigate the dynamical properties of nucleon resonances, especially the electromagnetic transition amplitudes and decay processes due to strong interactions, using the Sakai-Sugimoto model, which is a top-down approach to holographic QCD. In addition, the gravitational form factor and the stress distribution obtained from it, which have attracted much attention in recent years, were also investigated using the same approach. As a result, we found an interesting relation between the stability condition for the stress distribution and the glueball spectra.
Fujii, Daisuke; Iwanaka, Akihiro*
no journal, ,
Gravitational form factors (GFFs) of hadrons characterize the matrix elements of the energy-momentum tensor from which we can extract the pressure and shear force inside hadrons. In recent years, GFFs have been measured experimentally, and it will soon be possible to measure GFFs for hadrons at J-PARC. Before this, in this talk, we will discuss our recent work on pressure, shear force, and the GFFs of vector mesons from holographic QCD.
