arXiv subjects

L. R. Livramento

Publications and source records attributed to L. R. Livramento.

9 recordsLinked to original sources

arXiv2026

Compact Q-balls and Q-shells within a $CP^N$ Skyrme-Faddeev type model

While $CP^N$ models with analytic potentials are known to support finite-energy compact Q-ball and Q-shell solutions, their behavior in more complex Lagrangian frameworks remains a subject of active research. This work explores these non-topological structures within an extended Skyrme-Faddeev-type model that incorporates quartic derivative terms. In this context, harmonic time dependence and the presence of quartic terms constitute two independent stabilization mechanisms that allow the configurations to circumvent Derrick's scaling argument. We investigate the necessary conditions for the existence of these solutions and analyze the influence of quartic terms on the properties of the resulting compactons, specifically examining the $E(Q)$ relationship between energy and Noether charge. Our findings provide valuable insights into the stability and characteristics of compact boson stars within $CP^N$ models featuring higher-order derivative terms.

hep-th↗

arXiv2025

A Generalized False Vacuum Skyrme model

We propose a generalization of the False Vacuum Skyrme model for any simple compact Lie groups $G$ that leads to Hermitian symmetric spaces. The Skyrme field that in the original theory takes its values in $SU(2)$ Lie group, now takes its values in $G$, while the remaining fields correspond to the entries of a symmetric, positive, and invertible $\dim G \times \dim G$-dimensional matrix $h$. This model is also an extension of the generalized BPS Skyrme model. We prove that the global minima correspond to the $h$ fields being self-dual solutions of the generalized BPS Skyrme model, together with a particular field configuration for the Skyrme field that leads to a spherically symmetric topological charge density. As in the case of the original model, the minimization of the energy leads to the so-called reduced problem, defined in the context of false vacuum decay. This imposes a condition on the Skyrme field, which, if satisfied, makes the total energy of the global minima, as well as the main properties of the model, equivalent to those obtained for the $G=SU(2)$ case. We study this condition and its consequences within the generalized rational map ansatz and show how it can be satisfied for $G=SU(p+q)$, where $p$ and $q$ are positive integers, with the Hermitian symmetric spaces being $SU(p+q)/SU(p) \otimes SU(q) \otimes U(1)$. In such a case, the model is completely equivalent to the $G=SU(2)$ False Vacuum Skyrme model, independent of the values of $p$ and $q$. We also provide a numerical study of the baryon density, RMS radius, and binding energy per nucleon, which deepens the previous analysis conducted for the $SU(2)$ False Vacuum Skyrme model. Additionaly, in the case of $G = SU(3)$, we have studied the application of our model to the description of the binding energies and masses of the $Λ$-hypernuclei.

hep-th↗

arXiv2025

Self-duality and the Holomorphic Ansatz in Generalized BPS Skyrme Model

We propose a generalization of the BPS Skyrme model for simple compact Lie groups $G$ that leads to Hermitian symmetric spaces. In such a theory, the Skyrme field takes its values in $G$, while the remaining fields correspond to the entries of a symmetric, positive, and invertible $\dim G \times \dim G$-dimensional matrix $h$. We also use the holomorphic map ansatz between $S^2 \rightarrow G/H \times U(1)$ to study the self-dual sector of the theory, which generalizes the holomorphic ansatz between $S^2 \rightarrow CP^N$. This ansatz is constructed using the fact that stable harmonic maps of the two $S^2$ spheres for compact Hermitian symmetric spaces are holomorphic or anti-holomorphic. Apart from some special cases, the self-duality equations do not fix the matrix $h$ entirely in terms of the Skyrme field, which is completely free, as it happens in the original self-dual Skyrme model for $G=SU(2)$. In general, the freedom of the $h$ fields tend to grow with the dimension of $G$. The holomorphic ansatz enable us to construct an infinite number of exact self-dual Skyrmions for each integer value of the topological charge and for each value of $N \geq 1$, in case of the $CP^N$, and for each values of $p,\,q\geq 1$ in case of $SU(p+q)/SU(p)\otimes SU(q)\otimes U(1)$.

hep-th↗

arXiv2025

Harmonic, Holomorphic and Rational Maps from Self-Duality

We propose a generalization of the so-called rational map ansatz on the Euclidean space $\mathbb{R}^3$, for any compact simple Lie group $G$ such that $G/{\widehat K}\otimes U(1)$ is an Hermitian symmetric space, for some subgroup ${\widehat K}$ of $G$. It generalizes the rational maps on the two-sphere $SU(2)/U(1)$, and also on $CP^N=SU(N+1)/SU(N)\otimes U(1)$, and opens up the way for applications of such ansätze on non-linear sigma models, Skyrme theory and magnetic monopoles in Yang-Mills-Higgs theories. Our construction is based on a well known mathematical result stating that stable harmonic maps $X$ from the two-sphere $S^2$ to compact Hermitian symmetric spaces $G/{\widehat K}\otimes U(1)$ are holomorphic or anti-holomorphic. We derive such a mathematical result using ideas involving the concept of self-duality, in a way that makes it more accessible to theoretical physicists. Using a topological (homotopic) charge that admits an integral representation, we construct first order partial differential self-duality equations such that their solutions also solve the (second order) Euler-Lagrange associated to the harmonic map energy $E=\int_{S^2} \mid dX\mid^2 dμ$. We show that such solutions saturate a lower bound on the energy $E$, and that the self-duality equations constitute the Cauchy-Riemann equations for the maps $X$. Therefore, they constitute harmonic and (anti)holomorphic maps, and lead to the generalization of the rational map ansätze in $\mathbb{R}^3$. We apply our results to construct approximate Skyrme solutions for the $SU(N)$ Skyrme model.

hep-th↗

arXiv2022

A False Vacuum Skyrme Model for Nuclear Matter

The low energy regime of Quantum Chromodynamics (QCD) presents enormous challenges due to its large coupling. Effective field theories, like the Skyrme model, are useful approaches to study properties of strong interaction at hadronic scales. We propose a Skyrme-type model with a self-dual sector and that treats the density of the baryonic charge as a self-interacting fluid. The dynamics reduces to Coleman's false vacuum problem for a scalar field that is a fractional power of that density. The main result is that such a Skyrme-type model is the first one to reproduce, with good accuracy, the experimental values of radii and binding energies for a very wide range of the mass number. The robust and simple properties of the model lead to many possible generalizations with implications not only in nuclear physics but also in other areas of Physics.

hep-th↗

arXiv2022

A Quasi Self-Dual Skyrme Model

It has been recently proposed a modification of the Skyrme model which admits an exact self-dual sector by the introduction of six scalar fields assembled in a symmetric, positive and invertible 3x3 matrix h. In this paper we study soft manners of breaking the self-duality of that model. The crucial observation is that the self-duality equations impose distinct conditions on the three eigenvalues of h, and on the three fields lying in the orthogonal matrix that diagonalizes h. We keep the self-duality equations for the latter, and break those equations associated to the eigenvalues. We perform the breaking by the addition of kinetic and potential terms for the h-fields, and construct numerical solutions using the gradient flow method to minimize the static energy. It is also shown that the addition of just a potential term proportional to the determinant of h, leads to a model with an exact self-dual sector, and with self-duality equations differing from the original ones by just an additional coupling constant.

hep-th↗

arXiv2022

False vacuum Skyrmions revisited

We consider the classical static soliton solutions of the Skyrme model with false vacuum potential. We make use of fully three-dimensional relaxation calculations to construct global energy minimizers in the sectors of topological degrees from $Q=1$ to $Q=6$. These solutions may be metastable, they contain a domain of true vacuum inside the core. Further, we explore small regions of negative topological charge density which appear for the Skyrmions of degrees $Q=3,5,6$.

hep-th↗

arXiv2020

Self-Duality in the Context of the Skyrme Model

We study a recently proposed modification of the Skyrme model that possesses an exact self-dual sector leading to an infinity of exact Skyrmion solutions with arbitrary topological (baryon) charge. The self-dual sector is made possible by the introduction, in addition to the usual three SU(2) Skyrme fields, of six scalar fields assembled in a symmetric and invertible three dimensional matrix h. The action presents quadratic and quartic terms in derivatives of the Skyrme fields, but instead of the group indices being contracted by the SU(2) Killing form, they are contracted with the h-matrix in the quadratic term, and by its inverse on the quartic term. Due to these extra fields the static version of the model, as well as its self-duality equations, are conformally invariant on the three dimensional space R^3. We show that the static and self-dual sectors of such a theory are equivalent, and so the only non-self-dual solution must be time dependent. We also show that for any configuration of the Skyrme SU(2) fields, the h-fields adjust themselves to satisfy the self-duality equations, and so the theory has plenty of non-trivial topological solutions. We present explicit exact solutions using a holomorphic rational ansatz, as well as a toroidal ansatz based on the conformal symmetry. We point to possible extensions of the model that break the conformal symmetry as well as the self-dual sector, and that can perhaps lead to interesting physical applications.

hep-th↗

arXiv2017

Compact Q-balls and Q-shells in the CPN type models

We show that the CPN model with odd number of scalar fields and V-shaped potential possesses finite energy compact solutions in the form of Q-balls and Q-shells. The solutions were obtained in 3+1 dimensions. Q-balls appears for N=1 and N=3 whereas Q-shells are present for higher odd values of N. We show that energy of these solutions behaves as E~|Q|^5/6, where Q is the Noether charge.

hep-th↗