arXiv subjects

M. A. Marques

Publications and source records attributed to M. A. Marques.

At least 19 recordsLinked to original sources

arXiv2026

Large lumps

We introduce a procedure to obtain lump solutions via the formation of a kink-antikink pair, consisting of the superposition of kinks whose distance from the origin is controlled by a single parameter $a$. For large values of $a$, a wide plateau appears in the solution, which we call a large lump. The procedure involves the use of a first-order equation that allows the construction of the potential associated with the lump solution. We then investigate several known scalar field models where the parent kinks are capable of giving rise to novel lumps. The lump inherits the tails of the parent kink, allowing for either short-range exponential profiles or long-range profiles characterized by distinct power-law decays. We also show how to verify if an arbitrary lump solution can be obtained via our method and illustrate this possibility with a novel vacuumless lump.

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arXiv2026

Geometrically constrained multi-kink configurations in generalized impurity-doped field theories

This short communication investigates impurity coupling in generalized field theories where scalar coupling is introduced directly at the level of the kinetic and gradient contributions of the energy. We show that the fundamental aspects of the original theory, which has been previously investigated in the impurity-free setting, can be extended to the inhomogeneous scenario. In particular, an interpretation in terms of geometrically-constrained effective one-field theories with impurities is possible in the separable case. We show that BPS multi-kink configurations are possible in the model, as well as in the usual half-BPS scalar theories.

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arXiv2026

Compact structures in impurity-doped vacuumless systems

We investigate novel structures which arise from the compactification of vacuumless kinks in scalar field models coupled to impurities that preserve half the BPS sectors, described by first-order equations. We also investigate the behavior of the energy density and linear stability of the solutions. We show that compact vacuumless kinks cannot be obtained in impurity-free canonical models. By considering two distinct impurities, we study the conditions needed to induce compactification. In this scenario, stable half-compact or compact solutions are shown to emerge from the systems.

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arXiv2025

Magnetic monopoles in Yang-Mills-Higgs theory with impurities

In this work, BPS models built from the coupling of Yang-Mills-Higgs Lagrangian to impurities are investigated. We first consider scalar impurities, which in the BPS limit generate monopoles similar to those obtained in a previously considered class of $\mathrm{SU(2)}\times\mathrm{Z}_2$ or $\mathrm{SU(2)}\times\mathrm{SU(2)}$ models. We then focus on coupling with nonabelian impurities, defined as fixed backgrounds produced from fields transforming under the adjoint representation of SU(2), with a coupling chosen to preserve half of the BPS sectors. The nature of this coupling, the ensuing Bogomol'nyi bound and BPS equations, as well as the effect of these impurities in the abelianization that leads to the emergence of a U(1) gauge group are investigated. We study in greater detail impurities with spherical symmetry, and examine the manner in which impurity coupling changes the asymptotic behavior and range of monopole interactions. Moreover, we introduce a method that can be used to approximate solutions with the use of small perturbations around the Prasad-Sommerfield monopole, and discuss the possibility of extending the aforementioned results to dyons. In order to exemplify the most important properties of the theory, several specific impurity models are presented, with the respective monopole solutions are found numerically. These solutions present novel internal structure and multiple features that would not be possible in the original theory.

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arXiv2025

Generalized scalar field models in the presence of impurities

We study generalized scalar field models coupled to impurities in Minkowski spacetime with arbitrary dimensions. The investigation concerns a class of models that depends explicitly on the spacetime coordinates and also, it reveals the presence of a second-order tensor that can have null divergence if a first-order equation and a constraint are satisfied. We obtain the conditions to get compatibility between the equation of motion and the first-order equation, within a framework that is also used in the static case, to show that the introduction of an auxiliary function may allow to describe the energy density of the solution as a divergence. Stability of the solution under rescale of argument, translation in the space and small fluctuations are also fully investigated. We further illustrate the procedure considering the canonical model and also, the $k$-field and Born-Infeld-like models. The results show that stable solutions can be obtained in arbitrary dimensions, and the stability seems to be related to the first-order equation that emerges from imposing null divergence of the aforementioned tensor.

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arXiv2025

Super long-range vortices

In this work, we investigate the presence of vortex configurations with logarithmic tails, which we call super long-range vortices, in Maxwell-Higgs models with gauge field dynamics modified by generalized magnetic permeability in the Lagrangian density. By taking advantage of a first-order formalism, we study which behavior the magnetic permeability must have in order to allow for the presence of the logarithmic tails in the solutions. We also analyze the asymptotic behavior of the magnetic field and energy density. To illustrate our procedure, we present two models; one of them is described by analytical solutions.

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arXiv2025

Radially symmetric scalar field solutions in the presence of cuscuton term

In this work, we investigate radially symmetric solutions in arbitrary dimensions in scalar field models in the presence of the cuscuton term. We introduce a first-order formalism compatible with the equation of motion which supports field configurations engendering minimum energy and show that the cuscuton term does not induce instabilities in the solutions. To illustrate the general results, we study two distinct classes of models and present analytical solutions and the corresponding energy densities.

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arXiv2025

Scalar fields with impurities in arbitrary dimensions: first-order framework and exact solutions

We study a class of scalar field models coupled to impurities in arbitrary spacetime dimensions. The system admits the introduction of a second-order tensor that can be forced to obey an equality, if a first-order differential equation is satisfied, compatible with the equation of motion when the potential engenders a very specific form. In the case of static solutions, the energy density of the system can equal the divergence of an auxiliary vector function, which is included to help us solve the model. Stability of the field configuration under rescale of argument is investigated, and the procedure is illustrated considering distinct canonical models. The results show that exact solutions can be obtained in arbitrary dimensions, related to the presence of the first-order equation.

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arXiv2025

Bound states around vacuum in scalar ModMax model

In this work, we consider a two-dimensional scalar field model inspired by the dimensional reduction of a four-dimensional ModMax theory. Upon projecting out the 4D theory down to a 2D theory we obtain a theory which presents a constant electric field and two scalar fields. In order to investigate kinks, we include the presence of a potential and consider the static case with one of the fields in the vacuum, showing that the solutions for the non-uniform field can be mapped into the ones arising from the canonical model. By studying the linear stability of the model, we show that fluctuations around the uniform field are described by a Sturm-Liouville eigenvalue equation whose weight function depends on the non-uniform solution and the parameter of the ModMax model. Remarkably, the presence of the aforementioned weight may bring bound states to light, contrary to what occurs in the canonical model.

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arXiv2025

Super long-range kinks

In this work we investigate the presence of scalar field models supporting kink solutions with logarithmic tails, which we call super long-range structures. We first consider models with a single real scalar field and associate the long-range profile to the orders of vanishing derivatives of the potential at its minima. We then present a model whose derivatives are null in all orders and obtain analytical solutions with logarithmic falloff. We also show that these solutions are stable under small fluctuations. To investigate the forces between super long-range structures, we consider three methods and compare them. Next, we study two-field models in which the additional field is used to modify the kinetic term of the other. By using a first-order formalism based on the minimization of the energy, we explore the situation in which one of the fields can be obtained independently from the other. Within this framework, we unveil how to smoothly go from long- or short- to super long-range structures.

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arXiv2025

Analytical short- and long-range kink-like structures in scalar field models with polynomial interactions

We investigate a class of scalar field models which engender kink-like solutions in the presence of polynomial potentials that allows for modifications of the tails of the localized configurations. We introduce a parameter in the potential that controls the classical mass associated to its minima. By using the first-order framework developed by Bogomol'nyi, we obtain analytical solutions that become more and more interactive as we increase such parameter. By investigating the limit in which the parameter tends to infinite, the kink solution gets power law tails, and we show that this feature is related to the behavior of the classical mass, which vanishes in the aforementioned limit. We also investigate the stability against small fluctuations, with the results unveiling that, depending on the values of the parameter, the stability potential may support several bound states and also, it may attain a volcano-like profile.

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arXiv2025

Analytical solutions for Maxwell-scalar system on radially symmetric spacetimes

We investigate Maxwell-scalar models on radially symmetric spacetimes in which the gauge and scalar fields are coupled via the electric permittivity. We find the conditions that allow for the presence of minimum energy configurations. In this formalism, the charge density must be written exclusively in terms of the components of the metric tensor and the scalar field is governed by first-order equations. We also find a manner to map the aforementioned equation into the corresponding one associated to kinks in $(1,1)$ spacetime dimensions, so we get analytical solutions for three specific spacetimes. We then calculate the energy density and show that the energy is finite. The stability of the solutions against contractions and dilations, following Derrick's argument, and around small fluctuations in the fields is also investigated. In this direction, we show that the solutions obeying the first-order framework are stable.

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arXiv2024

Two-field models in the presence of impurities

This work deals with systems of two real scalar fields coupled to impurity functions, meant to model inhomogeneities often encountered in real physical applications. We investigate the theoretical properties of these systems and some of the consequences of impurity doping. We show that the theory may be modified in a way that preserves some BPS sectors, while also greatly impacting the behavior and internal structure of the solution, and exemplify those results with an investigation of a few interesting models in which impurities are coupled to a theory with a quartic potential. It is shown that, in the presence of impurities, the asymptotic behavior of field configurations may be changed, leading to solutions with different long-range properties, which are relevant to several physical applications. Our examples also highlight other important consequences that may follow from the addition of impurities, such as the presence of zero-modes that can significantly change the internal structure of a given solution without altering its energy, the creation of new topological sectors that did not exist in the impurity-free theory, and the possibility of stable, nontrivial configurations generated by topologically trivial boundary conditions. We have also shown that it is sometimes possible to find energy minimizers in BPS sectors which were unpopulated in the canonical theory. These features show that impurities allow for significant flexibility in both the form of energy minimizers and the boundary conditions used to generate them, which may potentially broaden the range of applicability of the theory.

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arXiv2024

Braneworlds in bumblebee gravity

We investigate thick-brane solutions within the five-dimensional bumblebee gravity in the presence of a real scalar field. Specifically, we implement the Lorentz symmetry breaking scenario within this context and obtain brane-like structures. Since the contribution of the bumblebee field is expected to be weak, we solve the field equations in the small-parameter regime. In this situation, we develop a first-order framework to describe the brane. The results show that the function which drives the bumblebee field may engender a lumplike structure whose shape depends on the parameters. On one hand, the effect of the non-minimal coupling, controlled by $ξ$, between the bumblebee field and gravity shifts the field from the vacuum expectation value. On the other hand, the aether parameter, $β$, is responsible for modifying the solution inside the brane.

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arXiv2024

Hybrid branes from split kinks

In this work, we investigate braneworld models generated by scalar fields in which one field has a split kink profile, in which a kink separates into two kinklike configurations. Our analysis covers models with two and three fields, examining the behavior of the most important quantities associated with the brane, such as the warp factor and the stability of the corresponding gravity sector. The results show that the brane is stable and supports a hybrid character, behaving as a thin and thick configuration.

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arXiv2024

Spatially localized scalar structures on hyperscaling violating geometries

In this work, we investigate probe scalar field models preserving covariance on fixed, static background geometries that present hyperscaling violation properties. We develop a first-order framework that rises from restrictions on the dynamical and hyperscaling violating exponents. The results show that stable, analytical kink-like solutions and their respective energy densities can be obtained for a general class of models. In the canonical model, in particular, these solutions minimize the energy of the system.

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arXiv2024

Geometrically constrained multifield models with BNRT solutions

In this paper, we investigate multifield models in which the two-field BNRT model is coupled to a third field through mediator functions in the Lagrangian density. To conduct the investigation, we obtain the equations of motion and develop a first-order formalism based on energy minimization. Two possibilities are considered: i) the third field acting in the mediator functions to modify the BNRT solutions; ii) the BNRT fields feeding the mediator function to produce effects in the kink solution of the third field. In the case i), the results show that the solutions may be related to the standard ones with the coordinate redefined in terms of the mediator functions if they are equal. This allows to induce effects similar to geometric constrictions in the core, or to compactify the tail of the BNRT solutions. If the mediator functions differ one from another, we show that the effects are distinct, with the compactification of just one of the two-field solutions. In the case ii), the orbit parameter of the model plays an important role, modifying the mediator function that induces changes in the profile of the kink associated to the third field.

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arXiv2024

Impurity-doped stable domain walls in spherically symmetric spacetimes

In this work, radially symmetric kink-like solutions in the presence of impurities are investigated for both flat and curved $D+1$ spacetimes, with geometry generated by a rotationally invariant background metric. We have examined the constraints placed upon the model by Derrick's theorem, and found out the Bogomol'nyi bound and equations of the symmetric restriction to this theory. Impurity-doped versions of a $ϕ^4$ model in two dimensions and a model with logarithmic potential in a Schwarzschild background have been explicitly worked out. The resulting configurations have been compared with those found in the homogeneous version of the theory, so that the effect of impurities in the form of solutions may be better appreciated. We have also generalized to higher dimensions some of the results that had been presented in the recent literature. These results relate to the possibility of BPS-preserving impurities, which we have found to still exist in the spacetimes considered in this work. We also investigate ways in which these results may be extended in a curved background.

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