arXiv subjects

Tobias Frederico

Publications and source records attributed to Tobias Frederico.

At least 37 records · Page 2Linked to original sources

arXiv2025

Proto-neutron Stars with Dark Matter Admixture: A Single-Fluid Approach

This work investigates the impact of dark matter (DM) on the microscopic and macroscopic properties of proto-neutron stars (PNSs). We employ a single-fluid framework in which DM interacts with ordinary matter (OM) via the Higgs portal and remains in thermal equilibrium through non-gravitational interactions. Using a quasi-static approximation, we analyze the evolution of PNSs during the Kelvin-Helmholtz phase by varying the DM mass while keeping the entropy per baryon and lepton fraction fixed. Our results show that DM absorbs thermal energy from the stellar medium without efficient re-emission, thereby altering neutrino emission and affecting the star's thermal evolution history. Furthermore, neutrinos contribute significantly to pressure support in the PNS phase, inhibiting DM mass accretion during neutrino-trapped stages. Based on the requirement to satisfy the observed $2,\rm M_\odot$ neutron star mass constraint and to maintain consistency with supernova remnant data, we suggest an upper limit of $m_χ\leq 0.62,\rm GeV$ for the DM mass that can accrete in evolving PNSs, within the model framework. In contrast, we established that cold neutron stars (NSs) can support higher DM masses without compromising equilibrium stability, owing to increased central density, enhanced gravitational binding energy, and reduced thermal pressure.

astro-ph.HE↗

arXiv2025

Hyperons and $Δ$'s in rotating protoneutron stars: Local properties

The structural evolution of rotating protoneutron stars encodes essential information about their observable signatures, while microscopic properties provide complementary knowledge to advance observational investigations. Using a relativistic mean-field model with density-dependent couplings that account for temperature and particle composition, we investigate rotation, neutrino-emission-driven changes in angular momentum, particle distributions, temperature profiles, and sound speed to probe the internal dynamics of protoneutron star matter. Additionally, we track the evolution of macroscopic quantities such as energy distribution and gravitational mass and establish direct links between microphysics and global evolution. Extending the framework of Phys. Rev. D 112, 023007 (2025), which focuses on the global properties of rotating protoneutron star evolution, our results reveal that protoneutron star deformation and thermal evolution are governed by angular momentum, mass, and composition. Exotic matter (hyperons and $Δ$-resonances) and rapid rotation enhance deformation leading to a reduction in core temperature, whereas slowly rotating stars like PSR J0740$+$6620 remain nearly spherical. Our predicted equatorial radii for PSR J0740$+$6620, $13.0\ \mathrm{km} < R_e < 13.5\ \mathrm{km}$, are consistent with NICER measurements. These findings constrain the EoS, requiring a self-consistent treatment of rotation, mass-dependent compression, and composition-driven modeling to accurately model protoneutron star evolution in the context of multi-messenger astrophysics.

astro-ph.HE↗

arXiv2025

Hot quark matter and merger remnants

This work investigates hot quark matter under the thermodynamic conditions characteristic of a binary neutron star (BNS) merger remnants. We used the density-dependent quark mass model (DDQM) to access the microscopic nuclear equation of state (EoS) in a series of snapshots. The strange quark matter (SQM) is studied at finite temperature and entropy, in the presence of electrons and muons and their corresponding neutrinos to simulate the BNS merger conditions. For the first time, we introduced temperature into the DDQM model using a lattice QCD-motivated approach to construct both isentropic and isothermal EoSs. We observe that as the entropy of the SQM increases, the merger remnant becomes more massive and increases in size, whereas the neutrino abundance also increases. In the fixed-temperature case, on the other hand, we observe that the entropy spreads from the surface towards the center of the remnant. We determine the particle distribution in the core of the remnants, the structure of the remnant, the temperature profile, sound velocity, and the polytropic index, and discuss their effects. The strange-quark star (SQS) remnants satisfy the $2\,{\rm M_\odot}$ mass constraint associated with neutron stars (NS).

hep-ph↗

arXiv2025

Hyperons and $Δ$'s in rotating protoneutron stars: Global properties

Rotation plays an important role in the evolution of most types of stars, in particular, it can have a strong influence on the evolution of a newly born proto-neutron star. In this study, we investigate the effects of rotation on four snapshots of the evolution of proto-neutron stars with hyperons and $Δ$-resonances in their cores, from birth as neutrino-rich objects to maturity as cold, catalyzed neutron stars. We focus on the effects of uniform rotation on the macroscopic structure of the star at three rotational frequencies -- 346.53 Hz, 716 Hz, and the Kepler frequency. Our investigation indicates that the impact of rotation at frequencies of $346.53$~Hz and $716$~Hz causes minor changes in the maximum gravitational mass but leads to significant changes in the stellar radius, particularly for stars with masses smaller than $2$~\msun. However, we observe drastic changes in the star's mass and radius when considering the Kepler frequency. In addition, we investigate other relevant characteristics of the rotating proto-neutron stars as they evolve such as the moment of inertia, compactness, central temperature, and Kerr parameter. Our results suggest that the inclusion of new degrees of freedom in the stellar core lead the star to be more sensitive to rotational dynamics, owing to an increase in compactness, a decrease in the central temperature, and a decrease in the moment of inertia.

hep-ph↗

arXiv2025

Strongly Interacting Quark Matter in Massive Quark Stars

This paper investigates the properties of strongly coupled matter at high baryon densities ($ρ_B$) in quark stars (QSs). The QS model is based on the density-dependent quark mass (DDQM) framework, modified (MDDQM) by enhancing the single-gluon interaction to generate higher repulsive pressure. The model parameters are constrained using Bayesian inference, incorporating observational data from the pulsars HESS J1731$-$347, PSR J0030$+$0451, PSR J0740$+$6620, and PSR J0952$-$0607. Our results show that the MDDQM model produces QSs with higher mass and compactness compared to the DDQM model. Among the four MDDQM parameterizations studied, two yield maximum star masses of 1.86 and 2.10 $\rm M_\odot$ and exhibit near-conformal behavior in the underlying quark matter (QM). The other two parameterizations, yielding QS masses of 2.30 and 2.37 $\rm M_\odot$, correspond to a stronger interaction in the underlying QM. These findings provide important insights into the equation of state of deconfined QM and its implications for the structure and stability of QSs.

nucl-th↗

arXiv2025

Gluonic contributions to the pion parton distribution functions

We investigate the role of a dynamical gluon in the pion within the Basis Light-Front Quantization (BLFQ) framework and compare it with the solution of the Minkowski space Bethe-Salpeter equation (BSE), focusing on contributions beyond the valence sector. We develop a framework to compute the quark-antiquark-gluon component of the pion, starting from its valence light-front wave function. Additionally, the quark and gluon parton distribution functions (PDFs) are derived by considering this higher Fock component in the pion state. The proposed operator, which acts on the valence state to produce the quark-antiquark-gluon component of the pion, is tested against results from BLFQ for its contribution to the quark and gluon PDFs, as well as with results from the BSE. In the BLFQ framework, we identify the effect of dynamical chiral symmetry breaking on the pion structure through the enhancement of the spin-flip matrix element. This enhancement is captured in the $|q\bar{q}g\rangle$ component of the light-front wave function and the associated gluon PDF. We explicitly demonstrate an enhancement of the low-$x$ contribution in the quark PDF, which is associated with the large spin-flip matrix element, which also drives the $π-ρ$ mass splitting. The proposed framework also enables an exploration of the effect of the dressed gluon mass for a given valence state at the pion scale. We show that when the gluon mass vanishes, departing from the constituent gluon picture, it has a significant impact on the gluon PDF.

hep-ph↗

arXiv2025

Supernova Remnants with Mirror Dark Matter and Hyperons

For the first time, we use relativistic mean-field (RMF) approximation with density-dependent couplings, adjusted by the DDME2 parameterization, to investigate the effects of dark matter on supernova remnants. We calculate the nuclear equation of state for nuclear and dark matter separately, under the thermodynamic conditions related to the evolution of supernova remnants. A mirrored model is adopted for dark matter, and its effect on remnant matter is studied using a two-fluid scenario. At each stage of the remnant evolution, we assume that dark and ordinary matter have the same entropy and lepton fraction, and a fixed proportion of dark matter mass fraction is added to the stellar matter to observe its effects on some microscopic and macroscopic properties of the star. We observe that dark matter in the remnant core reduces the remnant's maximum mass, radius, and tidal deformability. Moreover, dark matter heats the remnant matter and alters particle distributions, thereby decreasing its isospin asymmetry and increasing the sound speed through the matter.

hep-ph↗

arXiv2024

Proto-neutron stars with quark cores

This work investigates the evolution of proto-neutron stars (PNSs) from birth as neutrino-rich objects to maturity as cold-catalyzed neutrino-poor objects with nucleonic and non-nucleonic degrees of freedom. The focus is on the star's core where the nucleons, hyperons, and the $Δ$-isobars are expected to dissolve into a ``soup" of deconfined quarks, at higher baryon densities, to establish a possible hadron-quark phase transition. We separately calculate the nuclear equations of state (EoS) for the hadronic matter (composed of all the baryon octet and $Δ$-isobars) and the strange quark matter (SQM) under the same thermodynamic conditions characteristic of PNS and proto-strange star (PSS) evolution and construct the hybrid EoS using Maxwell's construction. The study allows us to determine the hadron-quark phase transitions along the evolution lines of the star. We observed a phase transition from hadronic matter to quark matter (QM) phase when the neutrinos have completely escaped from the star's core. The EoSs utilized are constrained to meet the $2\,\rm M_\odot$ threshold in accordance with the observational data.

nucl-th↗

arXiv2024

Solving the homogeneous Bethe-Salpeter equation with a quantum annealer

The homogeneous Bethe-Salpeter equation (hBSE), describing a bound system in a genuinely relativistic quantum-field theory framework, was solved for the first time by using a D-Wave quantum annealer. After applying standard techniques of discretization, the hBSE, in ladder approximation, can be formally transformed in a generalized eigenvalue problem (GEVP), with two square matrices: one symmetric and the other non symmetric. The latter matrix poses the challenge of obtaining a suitable formal approach for investigating the non symmetric GEVP by means of a quantum annealer, i.e to recast it as a quadratic unconstrained binary optimization problem. A broad numerical analysis of the proposed algorithms, applied to matrices of dimension up to 64, was carried out by using both the proprietary simulated-anneaing package and the D-Wave Advantage 4.1 system. The numerical results very nicely compare with those obtained with standard classical algorithms, and also show interesting scalability features.

hep-ph↗

arXiv2024

Lepton-neutron interaction and S-wave low energy parameters

A lepton-neutron potential in configuration space is obtained. It is based on the Coulomb plus hyperfine interaction Hamiltonian integrated over the neutron charge and magnetic densities. Different parametrisations of the neutron electromagnetic form factors are compared. It is given in the operator form with a central, spin-spin, tensor and spin-orbit terms. The potentials for lowest partial waves states are presented. We compute the lepton-neutron lepton ($ln$) low-energy parameters for the S-waves, estimate the zero-energy cross sections for higher angular momentum states, and point out a possible divergence in the partial wave summation due to the spin-orbit potential.

hep-ph↗

arXiv2023

A dynamical holographic QCD model for spontaneous chiral symmetry breaking and confinement

In this paper, we present a holographic realization of spontaneous chiral symmetry breaking and confinement. The latter is realized by building a solution of 5d Einstein-dilaton gravity leading to a confining quark antiquark potential. The 4d currents and the quark mass operator associated with chiral symmetry breaking and creation of meson states are mapped to 5d fields whose dynamics is given by a non-Abelian Higgs action. We introduce a non-minimal dilaton coupling to the tachyon potential which has two parameters, one of them controlling the presence or absence of spontaneous chiral symmetry breaking and the other controlling the sign of the chiral condensate as the quark mass grows. We calculate the masses of vector, scalar, axial-vector and pseudoscalar mesons, focusing on the effect of chiral symmetry breaking on the spectrum. In the chiral limit we identify the emergence of a massless state in the pseudoscalar meson spectrum, i.e., the pion. We calculate all meson decay constants and confirm that the pion satisfies the Gell-Mann-Oakes relation in the light quark regime.

hep-ph↗

arXiv2023

Enhanced charm CP asymmetries from final state interactions

We show that final state interactions (FSI) within a CPT invariant two-channel framework can enhance the charge-parity (CP) violation difference between $D^0\toπ^-π^+$ and $D^0\to K^-K^+$ decays up to the current experimental value. This result relies upon: (i) the dominant tree level diagram, (ii) the well-known experimental values for the $D^ 0\toπ^-π^+$ and $D^ 0\to K^-K^+$ branching ratios, and (iii) the $ππ\to ππ$ and $ππ\to K K $ scattering data to extract the strong phase difference and inelasticity. Based on well-grounded theoretical properties, we find the sign and bulk value of the $ΔA_{CP}$ and $A_{CP}(D^0 \to π^-π^+)$ recently observed by the LHCb Collaboration.

hep-ph↗

arXiv2023

Universal tetramer limit-cycle at the unitarity limit

We demonstrate that a four-boson limit-cycle independent of the Efimov one appears in Hamiltonian systems at the unitary limit. The model interaction contains two-, three- and four-body short-range potentials, which disentangle the interwoven three- and four-boson cycles, for the universal trimer and tetramer energy levels, respectively. The limit-cycle associated with the correlation between the energies of two successive universal tetramer levels for fixed weakly bound trimer is found to be largely model independent. This is a universal manifestation of an independent four-boson scale associated with a cycle beyond the Efimov one.

physics.atm-clus↗

arXiv2022

Proton quark distributions from a light-front Faddeev-Bethe-Salpeter approach

The projection onto the Light-Front of a Minkowski space Faddeev-Bethe-Salpeter equation model truncated at the valence level is applied to study the proton structure with constituent quarks. The dynamics of the model has built-in: (i) a bound diquark brought by a contact interaction, and (ii) the separation by Λ_QCD of the infrared and ultraviolet interaction regions. The model parameters are fine tuned to reproduce the proton Dirac electromagnetic form factor and mass. From that, the non-polarized longitudinal and transverse momentum distributions were computed. The results for the evolved non-polarized valence parton distributions suggest that: (i) the explicit consideration of the spin degree of freedom of both quark and diquark seems not relevant to it, and (ii) the comparison with the global fit from the NNPDF4.0 calls for higher Fock components of the wave function beyond the valence one.

hep-ph↗

arXiv2022

Scaling of the $^{19}$B two-neutron halo properties close to unitarity

We explore the description of the bound $^{19}$B isotope in terms of a $^{17}$B+n+n three-body system where the two-body subsystems $^{17}$B+n and neutron-neutron (nn) have virtual states close to the continuum. Dimensionless scaling functions for the root-mean-square (rms) radii are defined and studied for different parameters of the neutron-core potential and considering three different models for neutron-neutron interaction. The scaling functions for the radii are rooted on the universal behavior of three-body systems close to the Efimov limit and depend only on dimensionless quantities formed by the two-neutron separation energies and scattering lengths. Our results show in practice the model independence of these scaling functions close to unitarity. We provide an estimation of the different rms relative separation distances between the constituents, as well as of the proton and matter radii.

nucl-th↗

arXiv2022

Dynamical mass generation in Minkowski space at QCD scale

We undertake the challenging task to reveal the properties of dressed light-quarks in the space- and time-like regions. For that aim, we solved the Dyson-Schwinger equation (DSE) in Minkowski space for the quark propagator in a QCD inspired model, focusing on the realization of dynamical chiral symmetry breaking (DCSB) in the large coupling regime. The DSE is considered in the quenched approximation within the rainbow-ladder truncation with a massive gluon and a Pauli-Villars term, which is used to tune the infrared (IR) physics of the model. The solution of the DSE in Minkowski space is performed by resorting to the integral representation of the quark self-energy and propagator, which leads to a coupled set of closed self-consistent equations for the spectral densities, taking into account finite on-mass-shell renormalization. The parameters of the model are chosen such that the gluon mass scale is consistent with recent lattice QCD (LQCD) calculations, the Pauli-Villars mass is lowered down to about 1 GeV to concentrate strength in the infrared momentum region, and the coupling constant and renormalized mass are tuned to reproduce LQCD results for the quark mass function in the Landau gauge. Future application to study the pion consistently with DCSB within the Bethe-Salpeter framework with self-energies in Minkowski space is also delineated.

hep-ph↗

arXiv2022

Global CP asymmetries in charmless three-body $B$ decays with final state interactions

We propose a theoretical framework to understand the observable charge-parity (CP) violation in charmless three-body $B^\pm$ decays. The decay amplitudes put together the $ππ\to KK $ re-scattering and the U-spin symmetry, treated within a CPT invariant framework. This approach applied to a two-channel model provides the magnitudes and signs of the ratios of the global CP asymmetries for $B^\pm \to K^\pm π^+ π^- \,$, $B^\pm \to K^\pm K^+ K^- \,$, $B^\pm \to π^\pm K^+ K^- \,$ and $B^\pm \to π^\pm π^+π^- \,$ decays, compatible with those obtained from the available experimental data. In addition, by considering the neutral channels we predict the ratios for the global CP asymmetries for these decays.

hep-ph↗

arXiv2021

Fixed-Point Few-Body Hamiltonians in Quantum Mechanics

We revisited how Weinberg's ideas in Nuclear Physics influenced our own work and lead to a renormalization group invariant framework within the quantum mechanical few-body problem, and we also update the discussion on the relevant scales in the limit of short-range interactions. In this context, it is revised the formulation of the subtracted scattering equations and fixed-point Hamiltonians applied to few-body systems, in which the original interaction contains point-like singularities, such as Dirac-delta and/or its derivatives. The approach is being illustrated by considering two-nucleons described by singular interactions. This revision also includes an extension of the renormalization formalism to three-body systems, which is followed by an updated discussion on the applications to four particles.

nucl-th↗