arXiv subjects

Aldo Vera

Publications and source records attributed to Aldo Vera.

At least 19 recordsLinked to original sources

arXiv2026

Viscoelastic and thermal response on nuclear pasta states at finite baryon density

We compute the viscoelastic and thermal response of non-homogeneous hadronic condensates at finite baryon density representing crystals of baryonic tubes and layers. We describe them using analytic solutions of the Skyrme model in $3+1$ dimensions as ground states for a perturbative approach. At low enough temperatures, the lowest-energy excitations are described by a free massless scalar field theory in $1+1$ dimensions. We apply the Green-Kubo formulas to such excitations to obtain the elasticity tensor and other response coefficients. The analytic results of our computations are compared with available results on the nuclear pasta phase.

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arXiv2026

Semiclassical decay of de Sitter space into black holes with vortex-deformed horizons

We study the decay of de Sitter space into black holes whose horizons are dressed by BPS vortices of a $\mathrm{CP}^1$ action. The process is mediated by a regular Euclidean instanton obtained as a vortex-deformed generalization of the Nariai instanton. Its Euclidean geometry has the form $S^2\times\Sigma$, where $\Sigma$ is a compact surface whose geometry is shaped by the vortex configuration. The resulting decay rates are controlled by a discrete topological charge, showing that matter vortices open a new topologically organized family of decay channels for de Sitter space.

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arXiv2026

BPS lumps in the Nonminimal $CP^1$ Maxwell-Chern-Simons Model

We investigate self-dual radially symmetric configurations in the $CP^1$ model coupled to a Maxwell and Chern-Simons (CS) gauge fields through nonminimal interactions. Starting from the nonlinear $O(3)$-sigma model, we explicitly construct its classical mapping to the $CP^1$ formulation, highlighting the emergence of a local $U(1)$ gauge symmetry intrinsically associated with the Fubini-Study geometry of the target space. In the static regime, the combined effects of the Chern-Simons term and the Pauli-like nonminimal coupling modify the effective gauge connection, render the electric sector unavoidable, and give rise to magnetized and electrically polarized BPS lump configurations. By implementing the Bogomolnyi procedure, we determine the self-interaction potential required for self-duality and derive the corresponding BPS equations. We show that the magnetic flux remains quantized and is completely fixed by the asymptotic behavior of the gauge field, even in the presence of the Chern-Simons and nonminimal couplings. A detailed asymptotic analysis further reveals that finite-energy solutions necessarily correspond to lump-like configurations in which the $CP^1$ scalar field vanishes at spatial infinity. Numerical solutions of the BPS equations confirm that the resulting configurations are regular, spatially localized, and free of singularities, exhibiting confined magnetic flux together with a nontrivial localized electric field. These results show that the generalized $CP^1$-Maxwell-CS model supports self-dual solitons whose internal structure is rigidly governed by the target-space geometry rather than by spontaneous symmetry breaking.

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arXiv2026

Exact black holes and black branes with bumpy horizons supported by superfluid pions

We present exact solutions of the Einstein $SU(2)$ non-linear sigma model in $3+1$ spacetime dimensions, describing bumpy black holes and black branes. Using an Ansatz for superfluid pion multi-vortices, the matter sector reduces to a first-order BPS system, while the Einstein equations reduce to a Liouville equation with a smooth source governing the horizon deformation. These solutions describe horizons of different constant curvatures, with nontrivial bumpy geometries protected by an integer topological invariant, namely the vorticity, which also controls the number of bumps and the black hole thermodynamics. Remarkably, such horizons arise in a minimal and physically motivated matter model, without invoking exotic fields or modified gravity. The physical implications of these results in holography and astrophysics are briefly described.

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arXiv2025

Self-gravitating baryonic tubes supported by $\pi$- and $\omega$-mesons and its flat limit

In this paper, we construct self-gravitating topological solitons in the $SU(N)$ Einstein non-linear sigma model coupled to $\omega$-vector mesons in four space-time dimensions. These solutions represent tube-like configurations free of curvature singularities, carrying a non-vanishing topological charge that is identified as the baryon number. We show that by employing the maximal embedding Ansatz of $SU(2)$ into $SU(N)$ in the exponential representation, these tubes can be constructed for an arbitrary number of flavors, $N$, with the topological charge scaling proportionally to this number. The flat-space limit of the solutions, corresponding to an array of baryonic tubes within a finite volume, is analyzed in detail. Remarkably, while the total energy of the solitons at a finite volume is an increasing function of $N$, the binding energy decreases as the number of flavors increases. This analysis reaffirms that the inclusion of more than two flavors to the model systematically improves the physical predictions.

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arXiv2025

Universality of the chiral soliton lattice and its interaction with quark matter

In this paper, we show that the chiral soliton lattice (ChSL) is, in a precise sense, a universal feature of the low-energy limit of QCD minimally coupled to Maxwell theory. Here, we disclose that not only can the ChSL be obtained from the gauged Skyrme model in $3+1$ dimensions, including the back-reaction of the Maxwell $U(1)$ gauge field, we also demonstrate that the ChSL remains unchanged when higher-order terms arising from QCD, specifically the sub-leading corrections in the 't Hooft large $N_c$ expansion, are included. By considering a suitable ansatz adapted to describe topological solitons at finite baryon density in a constant magnetic field, the generalized Skyrme model coupled to the Maxwell theory is reduced to the effective Lagrangian of the ChSL phase, which describes a lattice of domain walls made of hadrons. One of the key points in this construction is the fact that even when the usual topological charge density vanishes, the presence of the Callan-Witten term in the topological charge density allows for a non-vanishing baryon number. In the present approach, the magnetic field can be external, as is usually assumed for the ChSL, or it can be self-consistently generated by the hadronic layers themselves. Finally, we show how our formulation allows us to study the coupling of the ChSL with quark matter. In particular, we derive the exact analytical spectrum of the Dirac equation in the high-density limit, providing a microscopic characterization of the fermionic excitations within the inhomogeneous hadronic background provided by the ChSL. The comparison of the present spectrum of the Dirac operator within the ChSL with the spectrum of the usual Dirac operator in a constant magnetic field discloses the fundamental role of both the quark-Skyrmion coupling and the hadronic profile in opening a gap and generating a shift in the spectrum itself.

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arXiv2025

Universal self-gravitating skyrmions

The self-gravitating skyrmion is an exact solution of the Einstein $SU(2)$-Skyrme model describing a topological soliton with baryon number $B=1$, living in a $4$-dimensional space-time in the presence of a cosmological constant. Here we show that, using the maximal embedding Ansatz of $SU(2)$ into $SU(N)$ in the Euler angles parametrization, this solution can be generalized to include arbitrary values of the flavor number and, consequently, allowing higher values of the topological charge. Also, we show that higher-order corrections in the 't Hooft expansion can be considered while still preserving the analytical nature of the solutions. Finally we will show that from the gravitational solutions it is possible to construct skyrmions in flat space-time at a finite volume.

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arXiv2024

Exact charged and rotating toroidal black hole in the Einstein $SU(N)$-Skyrme model

In this paper, we construct an exact solution of the Einstein $SU(N)$-Skyrme model in $D=4$ space-time dimensions describing a charged and rotating black hole with toroidal horizon. Rotation is added by applying an improper coordinate transformation to the known static toroidal black hole with Skyrme hair, while the electric charge is supplemented by considering a $U(1)$ gauge field interacting with Einstein gravity. We perform the thermal analysis in the grand canonical ensemble, explicitly showing the role that the flavor number plays. Some discussions about stability are also considered.

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arXiv2024

Superconducting multi-vortices and a novel BPS bound in chiral perturbation theory

We derive a novel BPS bound from chiral perturbation theory minimally coupled to electrodynamics at finite isospin chemical potential. At a critical value of the isospin chemical potential, a system of three first-order differential field equations (which implies the second-order field equations) for the gauge field and the hadronic profile can be derived from the requirement to saturate the bound. These BPS configurations represent magnetic multi-vortices with quantized flux supported by a superconducting current. The corresponding topological charge density is related to the magnetic flux density, but is screened by the hadronic profile. Such a screening effect allows to derive the maximal value of the magnetic field generated by these BPS magnetic vortices, being $B_{max}=2,04 \times 10^{14}G$. The solution for a single BPS vortex is discussed in detail, and some physical consequences, together with the comparison with the magnetic vortices in the Ginzburg-Landau theory at critical coupling, are described.

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arXiv2023

Exact modulated hadronic tubes and layers at finite volume in a cloud of $\pi$ and $\omega$ mesons

We construct topological soliton solutions describing baryonic tubes and layers with modulation in the $SU(2)$ non-linear sigma model coupled with $\omega$-mesons in $3+1$ dimensions. Using appropriate As\"antze for the pionic matter field and the $\omega$-mesons vector potential, the complete set of seven coupled partial differential equations can be solved analytically. These solutions represent modulated tubes and layers at finite volume with arbitrary baryon number, where the modulation of the solitons in one direction is determined by one of the three degrees of freedom of the pionic field, satisfying the equation of a two-dimensional free massless chiral scalar field. As expected, the inclusion of the $\omega$-mesons to the Non-linear sigma model allows to reduce the repulsion energy between baryons, which leads to a flattening of the tubes and layers in one direction, forming a kind of ``nuclear linguine phase''. Also, we show that this construction can be carried out even when higher order terms in the large $N_c$ expansion are included -- in particular the Skyrme term -- without spoiling the integrability of the field equations.

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arXiv2023

A note on the Hamiltonian structure of transgression forms

By incorporating two gauge connections, transgression forms provide a generalization of Chern-Simons actions that are genuinely gauge-invariant on bounded manifolds. In this work, we show that, when defined on a manifold with a boundary, the Hamiltonian formulation of a transgression field theory can be consistently carried out without the need to implement regularizing boundary terms at the level of first-class constraints. By considering boundary variations of the relevant functionals in the Poisson brackets, the surface integral in the very definition of a transgression action can be translated into boundary contributions in the generators of gauge transformations and diffeomorphisms. This prescription systematically leads to the corresponding surface charges of the theory, reducing to the general expression for conserved charges in (higher-dimensional) Chern-Simons theories when one of the gauge connections in the transgression form is set to zero.

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arXiv2023

Exact flavored black $p$-branes and self-gravitating instantons from toroidal black holes with Skyrme hair

In this paper, using the maximal embedding of $SU(2)$ into $SU(N)$ in the Euler angles parameterization, we construct a novel family of exact solutions of the Einstein $SU(N)$-Skyrme model. First, we present a hairy toroidal black hole in $D=4$ dimensions. This solution is asymptotically locally anti-de Sitter and is characterized by discrete hair parameters. Then, we perform a dimensional extension of the black hole to obtain black $p$-branes as solutions of the Einstein $SU(N)$-Non-linear sigma model in $D\geq5$ dimensions. These are homogeneous and topologically protected. Finally we show that, through a Wick rotation of the toroidal black hole, one can construct an exact self-gravitating instanton. The role that the flavor number $N$ plays in the geometry and thermodynamics of these configurations is also discussed.

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arXiv2023

Exact mapping from the $(3+1)$-dimensional Skyrme model to the $(1+1)$-dimensional sine-Gordon theory and some applications

A remarkable exact mapping, valid for low-enough energy scales and close to a sharp boundary distribution of hadronic matter, from the $(3+1)$-dimensional Skyrme model to the sine-Gordon theory in $(1+1)$ dimensions in the attractive regime is explicitly constructed. Besides the intrinsic theoretical interest to be able to describe the prototype of nonintegrable theories (namely, quantum chromodynamics in the infrared regime) in terms of the prototype of integrable relativistic field theories (namely, sine-Gordon theory in $(1+1)$ dimensions), we will show that this mapping can be extremely useful to analyze both equilibrium and out-of-equilibrium features of baryonic distributions in a cavity.

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arXiv2023

Solitonic self-sustained charge and energy transport on the superconducting cylinder

We present an exact time-dependent solution for a charged scalar field on a two-dimensional cylinder, that can be interpreted as representing a long-standing excitation on a $s$-wave superconducting state, which propagates along a nanotube constructed out of twisted bilayer graphene. The solution has a topological charge characterized by an integer number, which counts the winding of the Higgs phase winds around the cylinder. The resulting electric current generates its own electromagnetic field in a self-consistent way, without the need of any external fields to keep it alive.

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arXiv2022

Infinite conformal symmetry and emergent chiral (super)fields of topologically non-trivial configurations: From Yang-Mills-Higgs to the Skyrme model

The present manuscript discusses a remarkable phenomenon concerning non-linear and non-integrable field theories in $(3+1)$-dimensions, living at finite density and possessing non-trivial topological charges and non-Abelian internal symmetries (both local and global). With suitable types of ansätze, one can construct infinite-dimensional families of analytic solutions with non-vanishing topological charges (representing the Baryonic number) labelled by both two integers numbers and by free scalar fields in $(1+1)$-dimensions. These exact configurations represent $(3+1)$-dimensional topological solitons hosting $(1+1)$-dimensional chiral modes localized at the energy density peaks. First, we analyze the Yang-Mills-Higgs model, in which the fields depend on all the space-time coordinates (to keep alive the topological Chern-Simons charge), but in such a way to reduce the equations system to the field equations of two-dimensional free massless chiral scalar fields. Then, we move to the non-linear sigma model, showing that a suitable ansatz reduces the field equations to the one of a two-dimensional free massless scalar field. Then, we discuss the Skyrme model concluding that the inclusion of the Skyrme term gives rise to a chiral two-dimensional free massless scalar field (instead of a free massless field in two dimensions as in the non-linear sigma model) describing analytically spatially modulated Hadronic layers and tubes. The comparison of the present approach both with the instantons-dyons liquid approach and with Lattice QCD is shortly outlined.

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arXiv2022

Black holes and black strings in the Einstein $SU(N)$-non-linear sigma model

We construct analytical solutions describing black holes and black strings in the Einstein $SU(N)$-non-linear sigma model in $(3+1)$ dimensions. This construction is carried out using the maximal embbeding ansatz of $SU(2)$ together with the Euler parameterization of the $SU(N)$ group, in such a way that the non-linear sigma model equations are automatically satisfied for arbitrary values of the flavor number $N$ while the Einstein equations can be solved analytically. In particular, we construct black holes with spherical and flat horizons as well as black strings that present the geometry of a three-dimensional charged Bañados-Teitelboim-Zanelli black hole on the transverse section of the string. These configurations are not trivial embeddings of $SU(2)$ into $SU(N)$, which allow us to explicitly show the role that the flavor number plays on the geometry and thermodynamics of the black holes and black strings. Finally, we perform a thermal comparison between these configurations.

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arXiv2022

On the robustness of solitons crystals in the Skyrme model

In this work we analize how the inclusion of extra mesonic degrees of freedom affect the finite density solitons crystals of the Skyrme model. In particular, the first analytic examples of hadronic crystals at finite baryon density in both the Skyrme $ω$-mesons model as well as for the Skyrme $ρ$-mesons theory are constructed. These configurations have arbitrary topological charge and describe crystals of baryonic tubes surrounded by a cloud of vector-mesons. In the $ω$-mesons case, it is possible to reduce consistently the complete set of seven coupled non-linear field equations to just two integrable differential equations; one ODE for the Skyrmion profile and one PDE for the $ω$-mesons field. This analytical construction allows to show explicitly how the inclusion of $ω$-mesons in the Skyrme model reduces the repulsive interaction energy between baryons. In the Skyrme $ρ$-mesons case, it is possible to construct analytical solutions using a meron-type ansatz and fixing one of the couplings of the $ρ$-mesons action in terms of the others. We show that, quite remarkably, the values obtained for the coupling constants by requiring the consistency of our ansatz are very close to the values used in the literature to reduce nuclei binding energies of the Skyrme model without vector-mesons. Moreover, our analytical results are in qualitative agreement with the available results on the nuclear spaghetti phase.

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arXiv2022

Analytic meronic black holes, gravitating solitons and higher spins in the Einstein $SU(N)$-Yang-Mills theory

We construct meronic black holes and solitons in the Einstein $SU(N)$-Yang-Mills theory in $D=4$ and $D=5$ dimensions. These analytical solutions are found by combining the generalized hedgehog ansatz with the Euler parameterization of the $SU(N)$ group from which the Yang-Mills equations are automatically satisfied for all values of $N$ while the Einstein equations can be solved analytically. We explicitly show the role that the color number $N$ plays in the black hole thermodynamics as well as in the gravitational spin from isospin effect. Two remarkable results of our analysis are that, firstly, meronic black holes can be distinguished by colored black holes by looking at the spin from isospin effect (which is absent in the latter but present in the former). Secondly, using the theory of non-embedded ansatz for $SU(N)$ together with the spin from isospin effect, one can build fields of arbitrary high spin out of scalar fields charged under the gauge group. Hence, one can analyze interacting higher spin fields in asymptotically flat space-times without "introducing by hand" higher spin fields. Our analysis also discloses an interesting difference between the spin from isospin effect in $D=4$ and in $D=5$.

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