arXiv subjects

Yuta Hamada

Publications and source records attributed to Yuta Hamada.

At least 19 recordsLinked to original sources

arXiv2026

Data analysis of millions of Type IIB flux vacua

We study the vacuum structure of flux compactifications of type IIB string theory on the degree 18 hypersurface in $\mathbb{CP}^4_{1,1,1,6,9}$ with two effective complex structure moduli. We scan $30{,}770{,}178$ flux choices compatible with the tadpole bound, and use a gradient-based constrained minimization based on the SLSQP algorithm to identify candidates for local minima of the scalar potential, yielding a dataset of millions of candidate flux vacua. Using the $1{,}296{,}633$ reliable solutions selected from this dataset, we analyze distributions and correlations of various physical quantities such as vacuum expectation values of moduli and vacuum energy. Using quadratic flux invariants as input features, we train a classifier to identify solutions satisfying the numerical SUSY criterion $|V|<10^{-4.5}$. On a randomly selected test set, selecting the top-ranked $5\%$ recovers $47.2\%$ of the SUSY test solutions. We also use supervised regression to predict the potential and moduli field values. In the regression comparison, quadratic flux invariant inputs improve prediction of potential value and the complex-structure coordinates, while the vanilla six flux parameters give better predictions for the axio-dilaton coordinates under the tested settings.

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arXiv2026

Reconstructing BPS String Charge Cone in 6d N=(1,0) Supergravity

The tensor branch of six-dimensional $\mathcal N=(1,0)$ supergravity is characterized by a spectrum of BPS strings charged under the two-form gauge fields. Their charges span a cone in the tensor charge lattice, whose extremal rays are generated by primitive BPS string charges that become tensionless at the boundaries of the tensor moduli space. We develop a systematic procedure, based entirely on effective field theory data, to reconstruct the primitive BPS string generators and thereby determine the complete closed BPS string cone of any 6d $(1,0)$ supergravity theory. The key ingredients are the universal {\it H}-string, which allows us to isolate a fixed sector determined by classified LST blocks and gauge anomaly data from the remaining gauge-neutral E-string sector, and a BPS refinement of the Completeness Conjecture that ensures population of the relevant charge rays. We further show that this reconstruction provides new constraints on the low-energy theory and can rule out candidate EFTs that pass all previously known local lattice and anomaly consistency conditions. Separately, for theories admitting geometric tensor bases, we explain how the same reconstruction determines the complete Mori cone of the corresponding Kähler surface.

hep-th↗

arXiv2026

Axion RG flows and the holographic dynamics of instanton densities

Axionic holographic RG flow solutions are studied in the context of general Einstein-Axion-Dilaton theories. A non-trivial axion profile is dual to the (non-perturbative) running of the $θ$-term for the corresponding instanton density operator. It is shown that a non-trivial axion solution is incompatible with a non-trivial (holographic) IR conformal fixed point. Imposing a suitable axion regularity condition allows to select the IR geometry in a unique way. The solutions are found analytically in the asymptotic UV and IR regimes, and it is shown that in those regimes the axion backreaction is always negligible. The axion backreaction may become important in the intermediate region of the bulk. To make contact with the axion probe limit solutions, a systematic expansion of the solution is developed. Several concrete examples are worked out numerically. It is shown that the regularity condition always implies a finite allowed range for the axion source parameter in the UV. This translates into the existence of a finite (but large) number of saddle-points in the large $N_c$ limit. This ties in well with axion-swampland conjectures.

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arXiv2026

Quantum Algorithms for Finding Vacua in the ADK Landscape

We study quantum algorithms for finding a vacuum with a small cosmological constant in the toy model for string Landscape proposed by Arkani-Hamed, Dimopoulos, and Kachru. First, we construct a function-value oracle and use it for Grover search with query complexity $\mathcal{O}(2^{N/2})$, where $N$ is the number of scalar fields. Then, we point out that, by exploiting the linearity of the vacuum energy, the problem can be reduced to a collision problem between two blocks of the bit string. With this structure, we construct two quantum algorithms with query complexity $\mathcal{O}(2^{N/3})$. Compared with the pseudo-polynomial classical algorithm of Denef and Douglas, the quantum algorithms yield a large reduction in computational cost for the physically motivated parameter values.

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arXiv2026

A Rotor-Dressed Semiton State in a Monopole--Fermion Model

In four-flavor massless QED with a magnetic monopole, a single incident fermion is scattered into a state carrying a half-integral current vector in each flavor channel, called the semiton. Recently, the semiton has been interpreted as a twisted-sector fermion, but its microscopic Hilbert-space representation has not been fully developed. In this Letter, using a bosonized fermion--rotor model, we construct the semiton state explicitly. This is achieved by first identifying the correct vacuum of the system, and then constructing a unitary operator that shifts the rotor and creates a particle-hole cloud in each flavor channel. The semiton state is obtained by applying this operator to an ordinary fermion state. The resulting state has a localized fermion flavor density in the core region and a half-integral semiton front at the wavepacket. We also show that the state carries the correct $U(1)_M$ charge expectation values and energy-density profile. Our result provides a concrete Hilbert-space realization of the varying-Fock-space interpretation of monopole--fermion scattering, advocated in previous works by the author and collaborators.

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arXiv2026

6d Supergravity Blocks

We propose a systematic framework for constructing six-dimensional supergravity theories with eight supercharges that respect all known consistency constraints, including anomaly cancellation and the non-perturbative ${\it H}$-string constraints recently discovered by Kim, Vafa, and Xu. The basic objects in this framework are ${\it supergravity\,blocks}$, which are minimal collections of tensor multiplets consisting of a single little string theory sharing the ${\it H}$-string charge together with additional tensors whose string charges intersect it positively. A characteristic feature of each supergravity block is that its Gram matrix has exactly one positive eigenvalue, and therefore it necessarily contains gravitational BPS strings that cannot become tensionless anywhere in tensor moduli space. Any consistent 6d $(1,0)$ supergravity theory can then be obtained by gluing compatible blocks and subsequently enhancing the gauge algebras and matter content. As a first step toward establishing this framework concretely, we provide a complete classification of the ${\it non\text{-}Higgsable\,supergravity\,blocks}$, (or ${\it non\text{-}Higgsable\,gravity\,blocks}$ for short) namely those built from tensor multiplets that support only non-Higgsable gauge algebras.

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arXiv2026

Rethinking quantum information in gravity and fields

This paper presents a curated selection of research questions at the intersection of quantum gravity and quantum information, chosen to highlight issues that we regard as particularly important for researchers in both fields. We organize the discussion into four main themes: the operational characterization of observables, the role of observers, quantum error correction, and the infinite-dimensionality of Hilbert spaces. We hope that addressing these questions will engage researchers across both communities and further strengthen the profound interplay between the two disciplines.

hep-th↗

arXiv2026

Black String in the Standard Model

The Swampland cobordism conjecture predicts various new objects in a theory with dynamical gravity. Applying this idea to the Standard Model of particle physics, a string object is predicted. We numerically constructed such an object as a black string solution.

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arXiv2026

A Casimir obstruction to asymptotically flat black-brane completions of non-supersymmetric 7-branes

We study axisymmetric 7-brane solutions in the dilaton-gravity sector of 10d supergravity, including the backreaction of the Casimir energy induced by monodromies around the transverse circle. Without Casimir energy, we find that the system is analytically solvable and admits locally flat asymptotics with arbitrary deficit angles, but the corresponding solutions contain a naked singularity at finite proper distance. We investigate whether this singularity can be replaced by a regular finite-horizon black-brane core once Casimir backreaction is included. We find that, within our ansatz, Casimir backreaction obstructs an asymptotically locally flat black-brane completion of the naked 7-brane solution.

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arXiv2026

Revisiting constraints on magnetogenesis from baryon asymmetry

Magnetic fields in the universe potentially serve as a messenger of primordial physics. The observationally suggested intergalactic magnetic fields may be a relic of helical primordial $\mathrm{U}(1)_Y$ magnetic fields, which may also explain the origin of the baryon asymmetry of the universe. This scenario has been considered to be not viable, which we revisit as well as the baryon isocurvature problem for non-helical primordial $\mathrm{U}(1)_Y$ magnetic fields, based on the recent discussion on the hot electroweak theory. We find that maximally helical fields can be the origin of both the intergalactic magnetic fields and the baryon asymmetry of the universe and that there can be a window for non-helical fields to explain the origin of the intergalactic magnetic fields if the Higgs dynamics during the electroweak crossover compensate the helicity decay with a $\lesssim10^{-9\text{--}-10}$ precision.

hep-ph↗

arXiv2025

Inflation models selected by the swampland distance conjecture with the Lyth bound

We investigate the extent to which the Swampland Conjecture can be employed to constrain large-field inflationary models from the perspective of quantum gravity consistency. In particular, we focus on the Swampland Distance Conjecture, which imposes an upper bound on the amplitude of primordial gravitational waves predicted by large-field inflation scenarios. This provides a striking contrast with the well-known Lyth bound, which yields a lower bound on the tensor-to-scalar ratio in such models. The two bounds thus play complementary roles in assessing the viability of inflationary scenarios. We demonstrate that, for certain representative large-field inflation models, the Swampland Distance Conjecture alone can impose more stringent upper limits on the tensor-toscalar ratio than current observational constraints from the cosmic microwave background. These findings highlight the utility of Swampland criteria as a theoretical discriminator among competing inflationary models, independent of empirical data.

hep-th↗

arXiv2025

Symmetries of Hot SM, Magnetic Flux & Baryogenesis from Helicity Decay

We revisit the electroweak crossover of the Standard Model (SM) in the early Universe, focusing on the interplay between generalized global symmetries, magnetic flux dynamics, and baryogenesis. Employing the dimensionally reduced 3d effective field theory of the SM at high temperature, we identify the symmetry structure -- including higher-form and magnetic symmetries -- and analyze their spontaneous breaking patterns across the crossover. We further define a gauge-invariant mixing angle that interpolates between $\mathrm{U}(1)_Y$ and $\mathrm{U}(1)_\mathrm{em}$ magnetic fields. Based on this framework, we examine baryogenesis via decaying magnetic helicity and identify three key effects: the baryon asymmetry is modified by an $\mathcal{O}(1)$ factor due to (1) the gauge-invariant definition of the mixing angle and (2) the approximate conservation of the unconfined magnetic flux; (3) a novel non-perturbative process in the presence of magnetic flux, which has been overlooked in previous analyses. Our findings suggest that the previous estimation of baryon asymmetry from the magnetic helicity decay may have sizable uncertainties, and we caution against relying on it, calling for further investigation.

hep-ph↗

arXiv2025

Magnetic Helicity, Magnetic Monopoles, and Higgs Winding

Changes in magnetic helicity are often discussed across a variety of fields, from condensed matter physics to early universe cosmology. It is frequently stated that the helicity change is given by the integral of the gauge field strength tensor and its dual over spacetime, $\int F \wedge F$. However, this is incorrect when magnetic monopoles once exist in the spacetime. In this paper, we show the correct formula of the helicity change in such a case for the Maxwell theory with the magnetic monopoles. We also discuss what happens when we embed the Maxwell theory with magnetic monopoles into non-Abelian gauge theories. We show that a similar formula holds for the 't Hooft--Polyakov monopole. In particular, we find the winding numbers and the zeroes of the Higgs field in the non-Abelian gauge theory play a crucial role in the helicity change. The same discussion is also applicable to the electroweak theory, and we discuss the implication of our findings to the baryon number change via the chiral anomaly in the early universe.

hep-ph↗

arXiv2025

Investigating 9d/8d non-supersymmetric branes and theories from supersymmetric heterotic strings

We consider heterotic string theories in nine and eight dimensions. We identify the disconnected part of the spacetime gauge group by studying the outer automorphism of the charge lattices. The absence of the global symmetry indicates the existence of non-supersymmetric codimension two branes. Moreover, we provide a list of gauge groups and matter contents of non-supersymmetric rank-reduced heterotic string theories (a branch corresponding to the $E_8$ string on $S^1$) from the orbifolding of the outer automorphism as well as the fermion parity. We also provide examples in eight dimensions.

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arXiv2025

More on 8d non-supersymmetric branes and heterotic strings

We determine the maximal gauge groups arising in $E_8$ heterotic string theory on $T^2$. Our analysis proceeds along two approaches. First, we start the moduli space of the supersymmetric heterotic string theory on $T^2$ focusing on points of maximal gauge enhancement. At these special points, the charge lattice can exhibit a $\mathbb{Z}_2$ outer automorphism corresponding to the bulk gauge symmetry. By orbifolding the worldsheet theory by it with the fermion parity, we obtain the maximal gauge group of the $E_8$ theory. Second, we directly study the toroidal compactification of 10d $E_8$ heterotic string. Both approaches agree, yielding a classification of $22$ maximal gauge groups. For each case, we present the corresponding massless spectrum. In light of the no global symmetry/cobordism conjecture in quantum gravity, our result also offer a classification of non-supersymmetric branes in 8d supersymmetric heterotic string theories.

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arXiv2025

A finite 6d supergravity landscape from anomalies

6d supergravities with non-abelian gauge group are subject to many consistency conditions. While the absence of local gauge and gravitational anomalies allows for infinitely many models, we show that those conditions stemming from the absence of both local and global anomalies together are strong enough to leave only finitely many consistent models. To do this we distill the consequences of anomaly cancellation into a high-dimensional linear program whose dual can be efficiently studied using standard techniques. We obtain a universal bound on the number of tensor multiplets $T \leq 11 \cdot 273 = 3003$ and show that this leads to a finite landscape of consistent non-abelian models. Interestingly, the model which saturates this bound has gauge group $[E_8 \times F_4 \times (G_2 \times \mathrm{SU}(2))^2]^{273}$, which bears a striking resemblance to the model which saturates the bound $T \leq 193$ for F-theory constructions.

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arXiv2024

Skill Transfer System that Visualizes and Presents Tactile Information in an AR Environment

In recent years, the lack of successors for traditional skills has become an issue. To solve this problem, we propose a skill transfer system that presents tactile information in spatial tasks as a color map on an AR space. We believe that providing the operator with feedback of the force and tactile information during the work is useful for learning skills that require time to master. Furthermore, by following the operator's hand and presenting tactile information, we expect to accelerate the learning of skills by not only presenting tactile information as a physical sensation, but also by making the operator associate tactile information with position.

cs.HC↗

arXiv2024

Towards a complete classification of 6D supergravities

The constraints arising from anomaly cancellation are particular strong for chiral theories in six dimensions. We make progress towards a complete classification of 6D supergravities with minimal supersymmetry and non-abelian gauge group. First, we generalize a previously known infinite class of anomaly-free theories which has $T\gg 9$ to essentially any semi-simple gauge group and infinitely many choices for hypermultiplets. The construction relies on having many decoupled sectors all selected from a list of four simple theories which we identify. Second, we use ideas from graph theory to rephrase the task of finding anomaly-free theories as constructing cliques in a certain multigraph. A branch-and-bound type algorithm is described which can be used to explicitly construct, in a $T$-independent way, anomaly-free theories with an arbitrary number of simple factors in the gauge group. We implement these ideas to generate an ensemble of $\mathcal{O}(10^7)$ irreducible cliques from which anomaly-free theories may be easily built, and as a special case obtain a complete list of $19,\!847$ consistent theories for $T=0$, for which the maximal gauge group rank is $24$. Modulo $\mathrm{U}(1)$, $\mathrm{SU}(2)$ and $\mathrm{SU}(3)$ simple factors and the new infinite families, we give a complete characterization of anomaly-free theories and show that the bound $T\leq 273$ is sharp.

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