Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Using partially restored isospin symmetry, we calculate the nuclear matrix elements for a special decay mode of a two-neutrino double beta decay – the decay to the first 2<jats:sup>+</jats:sup> excited states. Employing the realistic CD–Bonn nuclear force, we analyze the dependence of the nuclear matrix elements on the isovector and isoscalar parts of proton–neutron particle–particle interactions. The dependence on the different nuclear matrix elements is observed, and the results are explained. We also provide the phase space factors using numerical electron wavefunctions and properly chosen excitation energies. Finally, we present our results for the half-lives of this decay mode for different nuclei. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>This study employs the relativistic mean field theory with the Green's function method to study the single-particle resonant states. In contrast to our previous work [Phys. Rev. C, <jats:bold>90</jats:bold>: 054321 (2014)], the resonant states are identified by searching for the poles of Green's function or the extremes of the density of states. This new approach is highly effective for all kinds of resonant states, no matter whether they are broad or narrow. The dependence on the space size for the resonant energies, widths, and the density distributions in the coordinate space has been checked and was found to be very stable. Taking <jats:sup>120</jats:sup>Sn as an example, four new broad resonant states <jats:inline-formula> <jats:tex-math><?CDATA $ 2g_{7/2} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_084105_M2.jpg" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA $ 2g_{9/2} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_084105_M3.jpg" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA $ 2h_{11/2} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_084105_M4.jpg" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math><?CDATA $ 1j_{13/2} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_084105_M5.jpg" xlink:type="simple" /> </jats:inline-formula> were observed, and the accuracy for the width of the very narrow resonant state <jats:inline-formula> <jats:tex-math><?CDATA $ 1h_{9/2} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_084105_M6.jpg" xlink:type="simple" /> </jats:inline-formula> was highly improved to <jats:inline-formula> <jats:tex-math><?CDATA $ 1\times 10^{-8} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_084105_M7.jpg" xlink:type="simple" /> </jats:inline-formula> MeV. Further, our results are very close to those obtained using the complex momentum representation method and the complex scaling method. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>By modeling the fragmentation process using a dynamic model and permitting only evaporation in the statistical code, the main features of a projectile fragmentation at 600 MeV/u were considered in our previous study [Phys. Rev. C, <jats:bold>98</jats:bold>: 014610 (2018)]. In this study, we extend this to the isospin dependence of a projectile fragmentation at several hundreds of MeV/u. We searched for isospin observables related to the isospin fractionation to extract the symmetry energy, and found that at the pre-equilibrium stage of the collisions an isospin diffusion will take place and affect the isospin of the final fragments. The isospin fractionation plays a part during the fragmenting stage. Compared to the soft symmetry energy, the stiff symmetry energy provides a smaller repulsive force for neutrons and an attractive force for the protons in a neutron-rich system at a subnormal density, and hence causes a smaller isospin asymmetry of the gas phase, leaving a more neutron-rich liquid phase. An observable robust isospin is proposed to extract the slope of the symmetry energy at normal density based on the isospin dependence of the projectile fragmentation at hundreds of MeV/u. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The solutions of the relativistic viscous hydrodynamics for longitudinally expanding fireballs are investigated with the Navier-Stokes theory and Israel-Stewart theory. The energy and the Euler conservation equations for the viscous fluid are derived in Rindler coordinates, by assuming that the longitudinal expansion effect is small. Under the perturbation assumption, an analytical perturbation solution for the Navier-Stokes approximation and numerical solutions for the Israel-Stewart approximation are presented. The temperature evolution with both shear viscous effect and longitudinal acceleration effect in the longitudinal expanding framework are presented. The specific temperature profile shows symmetric Gaussian shape in the Rindler coordinates. Further, we compare the results from the Israel-Stewart approximation with the results from the Bjorken and the Navier-Stokes approximations, in the presence of the longitudinal acceleration expansion effect. We found that the Israel-Stewart approximation gives a good description of the early stage evolutions than the Navier-Stokes theory.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>As a next-generation complex extensive air shower array with a large field of view, the large high altitude air shower observatory (LHAASO) is very sensitive to the very-high-energy gamma rays from ~300 GeV to 1 PeV and may thus serve as an important probe for the heavy dark matter (DM) particles. In this study, we make a forecast for the LHAASO sensitivities to the gamma-ray signatures resulting from DM decay in dwarf spheroidal satellite galaxies (dSphs) within the LHAASO field of view. Both individual and combined limits for 19 dSphs incorporating the uncertainties of the DM density profile are explored. Owing to the large effective area and strong capability of the photon-proton discrimination, we find that LHASSSO is sensitive to the signatures from decaying DM particles above <jats:inline-formula> <jats:tex-math><?CDATA ${\cal{O}}(1)$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085001_M1.jpg" xlink:type="simple" /> </jats:inline-formula> TeV. The LHAASO sensitivity to the DM decay lifetime reaches <jats:inline-formula> <jats:tex-math><?CDATA ${\cal{O}} (10^{26}) \sim {\cal{O}} (10^{28})$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085001_M2.jpg" xlink:type="simple" /> </jats:inline-formula> s for several decay channels at the DM mass scale from 1 TeV to 100 TeV. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The quintessence-like potential of vacuum energy can meet the requirements from both quantum gravity and the accelerating expansion of the universe. The anti-de Sitter (AdS) vacuum in string theory must be lifted to the meta-stable dS vacuum with a positive vacuum energy density to explain the accelerating expansion of the universe. Based on possible large-scale Lorentz violation, we define an effective cosmological constant that depends not only on the bare cosmological constant but also on the Lorentz violation effect. We find that the evolution of the effective cosmological constant exhibits the behavior of the quintessence potential when the bare cosmological constant originates from the string landscape, in contrast to the existence of a local minimum during evolution when the bare cosmological constant is supplied by the swampland. The critical value of the bare cosmological constant is approximately zero for the behavior transition. The frozen large-scale Lorentz violation can uplift the AdS vacua to an effective quintessence-like one in this sense.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The spatial-dependent propagation (SDP) model has been demonstrated to account for the spectral hardening of both primary and secondary Cosmic Rays (CRs) nuclei above about 200 GV. In this work, we further apply this model to the latest AMS-02 observations of electrons and positrons. To investigate the effect of different propagation models, both homogeneous diffusion and SDP are compared. In contrast to the homogeneous diffusion, SDP brings about harder spectra of background CRs and thus enhances background electron and positron fluxes above tens of GeV. Thereby, the SDP model could better reproduce both electron and positron energy spectra when introducing a local pulsar. The influence of the background source distribution is also investigated, where both axisymmetric and spiral distributions are compared. We find that considering the spiral distribution leads to a larger contribution of positrons for energies above multi-GeV than the axisymmetric distribution. In the SDP model, when including a spiral distribution of sources, the all-electron spectrum above TeV energies is thus naturally described. In the meantime, the estimated anisotropies in the all-electrons spectrum show that in contrary to the homogeneous diffusion model, the anisotropy under SDP is well below the observational limits set by the Fermi-LAT experiment, even when considering a local source.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we propose a homogeneous curvaton mechanism that operates during the preheating process and in which the effective mass is running (i.e., its potential consists of a coupling term and an exponential term whose contribution is subdominant thereto). This mechanism can be classified into either narrow resonance or broad resonance cases, with the spectral index of the curvaton consituting the deciding criteria. The inflationary potential is that of chaotic inflation (i.e., a quadratic potential), which could result in a smooth transition into the preheating process. The entropy perturbations are converted into curvature perturbations, which we validate using the <jats:inline-formula> <jats:tex-math><?CDATA $ \delta N $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085103_M1.jpg" xlink:type="simple" /> </jats:inline-formula> formalism. By neglecting the exponential term's contribution to the curvaton potential, we calculate the power spectrum <jats:inline-formula> <jats:tex-math><?CDATA $ P_\zeta $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085103_M2.jpg" xlink:type="simple" /> </jats:inline-formula> and the nonlinear non-Gaussian parameter <jats:inline-formula> <jats:tex-math><?CDATA $ f_{NL} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085103_M3.jpg" xlink:type="simple" /> </jats:inline-formula>. Our calculations analytically show that these two observables are independent of the inflaton potential. Finally, when the curvaton decays (and the inflaton field vanishes), the exponential potential approaches a constant value similar to that of the cosmological constant, which may play the role of dark energy. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Rastall gravity is a modification of Einstein's general relativity in which the energy-momentum conservation is not satisfied and depends on the gradient of the Ricci curvature. It is currently in dispute whether Rastall gravity is equivalent to general relativity (GR). In this work, we constrain the theory using the rotation curves of low surface brightness (LSB) spiral galaxies. By fitting the rotation curves of LSB galaxies, we obtain parameter <jats:inline-formula> <jats:tex-math><?CDATA $\beta$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085104_M1.jpg" xlink:type="simple" /> </jats:inline-formula> of the Rastall gravity. The <jats:inline-formula> <jats:tex-math><?CDATA $\beta$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085104_M2.jpg" xlink:type="simple" /> </jats:inline-formula> values of LSB galaxies satisfy the weak energy condition (WEC) and strong energy condition (SEC). Combining the <jats:inline-formula> <jats:tex-math><?CDATA $\beta$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_8_085104_M3.jpg" xlink:type="simple" /> </jats:inline-formula> values of type Ia supernovae and the gravitational lensing of elliptical galaxies on Rastall gravity, we conclude that Rastall gravity may be equivalent to general relativity. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, we investigate the invariant-mass distribution of top-quark pairs near the 2<jats:italic>m<jats:sub>t</jats:sub> </jats:italic> threshold, which strongly influences the determination of the top-quark mass <jats:italic>m<jats:sub>t</jats:sub> </jats:italic>. Higher-order non-relativistic corrections lead to large contributions, which are not included in the state-of-the-art theoretical predictions. A factorization formula is derived to resum such corrections to all orders in the strong-coupling, and necessary ingredients are calculated to perform the resummation at next-to-leading power. We combine the resummation with fixed-order results and present phenomenologically relevant numerical results. The resummation effect significantly increases the differential cross-section in the threshold region and makes the theoretical prediction more compatible with experimental data. We estimate that using our prediction in the determination of <jats:italic>m<jats:sub>t</jats:sub> </jats:italic> will lead to a value closer to the direct measurement result. </jats:p>