• Standard model effective field theory from on-shell amplitudes
    We present a general method of constructing unfactorizable on-shell amplitudes (amplitude basis) and build up their one-to-one correspondence to the independent and complete operator basis in effective field theory (EFT). We apply our method to the Standard Model EFT and identify the amplitude basis in dimensions 5 and 6, which correspond to the Weinberg operator and operators in the Warsaw basis, except for some linear combinations.
  • Effects of the formation time of parton shower on jet quenching in heavy-ion collisions
    Jet quenching has successfully served as a hard probe to study the properties of Quark-Gluon Plasma (QGP). As a multi-particle system, jets require time to develop from a highly virtual parton to a group of partons close to mass shells. In this study, we present a systematical analysis on the effects of this formation time on jet quenching in relativistic nuclear collisions. Jets from initial hard scatterings were simulated with Pythia, and their interactions with QGP were described using a Linear Boltzmann Transport (LBT) model that incorporates both elastic and inelastic scatterings between jet partons and the thermal medium. Three different estimations of the jet formation time were implemented and compared, including instantaneous formation, formation from single splitting, and formation from sequential splittings, before which no jet-medium interaction was assumed. We found that deferring the jet-medium interaction with a longer formation time not only affects the overall magnitude of the nuclear modification factor of jets but also its dependence on the jet transverse momentum.
  • Black hole shadow in f(R) gravity with nonlinear electrodynamics
    By analyzing the propagation of discontinuity in nonlinear electrodynamics, we numerically investigate the related black hole shadows of recently derived rotating black hole solutions in $f(R) $ gravity. In this context, the geodesic motion of the relevant perturbations is governed by an effective geometry, which is closely related to the underlying spacetime metric. We derive the effective geometry, and the latter is used to determine the trajectory of the propagation vector of an arbitrary finite discontinuity in the electrodynamic perturbations, namely, the photon. Subsequently, the image of the black hole is evaluated using the ray-tracing technique. Moreover, we discuss the physical relevance of metric parameters, such as the nonlinear coupling, spin, and charge, by studying their impact on the resultant black hole shadows.
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  • Relativistic polytropic models of charged anisotropic compact objects
    2023, 47(3): 035109-035109-19. doi: 10.1088/1674-1137/acae5b
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    In this paper, we introduce new viable solutions to the Einstein-Maxwell field equations by incorporating the features of anisotropic matter distributions within the realm of the general theory of relativity (${\rm GR}$). To obtain these solutions, we employed the Finch-Skea spacetime, along with a generalized polytropic equation of state (${\rm EoS}$). We constructed various models of generalized polytropes by assuming different values of the polytropic index, i.e., $\eta= \dfrac{1}{2},~ \dfrac{2}{3},~ 1$, and $ 2 $. Next, numerous physical characteristics of these considered models were studied via graphical analysis, and they were found to obey all the essential conditions for astrophysical compact objects. Furthermore, such outcomes of charged anisotropic compact star models could be reproduced in various other cases including linear, quadratic, and polytropic ${\rm EoS}$
  • Charged AdS black holes with finite electrodynamics in 4D Einstein-Gauss-Bonnet gravity
    2023, 47(3): 035108-035108-9. doi: 10.1088/1674-1137/acaaf4
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    Using a modified expression for the electric potential in the context of T-duality [Gaete and Nicolini, Phys. Lett. B, 2022], we obtained an exact charged solution within the 4D Einstein-Gauss-Bonnet (4D EGB) theory of gravity in the presence of a cosmological constant. We show that the solution also exists in the regularized 4D EGB theory. Moreover, we point out a correspondence between the black hole solution in the 4D EGB theory and the solution in the non-relativistic Horava–Lifshitz theory. The black hole solution is regular and free from singularity. As a special case, we derive a class of well known solutions in the literature.
  • Fractional phase transitions of RN-AdS black holes at their Davies points
    2023, 47(3): 035102-035102-7. doi: 10.1088/1674-1137/aca957
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    In this study, we investigate the phase transitions of the RN-AdS black hole at its Davies points according to the generalized Ehrenfest classification of phase transition established based on fractional derivatives. Notably, Davies points label the positions at which the heat capacity diverges. According to the usual Ehrenfest classification, second-order phase transitions occur at these points. For the RN-AdS black hole, the Davies points can be classified into two types. The first type corresponds to extreme values of the temperature, and the second type corresponds to the infection point (namely the critical point) of temperature. Employing the generalized Ehrenfest classification, we determine that the orders of phase transition at the two types of Davies points are different, that is, we note an order of 3/2 for the first type and 4/3 for the second type. Thus, this finer-grained classification can discriminate between phase transitions that are expected to lie in the same category, providing new insights leading toward a better understanding of black hole thermodynamics.
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