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Published:   , doi: 10.1088/1674-1137/44/2/023101
Abstract:
The thermalization process of the holographic entanglement entropy (HEE) of an annular domain is investigated over the Vaidya-AdS geometry. We numerically determine the Hubeny-Rangamani-Takayanagi (HRT) surface which may be a hemi-torus or two disks, depending on the ratio of the inner radius to the outer radius of the annulus. More importantly, for some fixed ratio of two radii, it undergoes a phase transition or double phase transitions from a hemi-torus configuration to a two-disk configuration, or vice versa, during the thermalization. The occurrence of various phase transitions is determined by the ratio of two radii of the annulus. The rate of entanglement growth is also investigated during the thermal quench. The local maximal rate of entanglement growth occurs in the region with double phase transitions. Finally, if the quench process is fairly slow which may be controlled by the thickness of null shell, the region with double phase transitions vanishes.
Published:   , doi: 10.1088/1674-1137/44/1/013102
Abstract:
Mass spectra and wave functions for the doubly heavy baryons are computed in the picture that the two heavy quarks inside a baryon form a compact heavy 'diquark core' in color anti-triplet, then bind the rest light quark into a colorless baryon. The reduced two two-body problems are described by the relativistic Bethe-Salpeter equations (BSEs) with relevant QCD-inspired kernels. So far, in this work, we only focus on the doubly heavy baryons with \begin{document}$1^+$\end{document} heavy diquark cores. By solving the BSEs in the instantaneous approximation, we first present mass spectra and the relativistic wave functions for diquark cores, and then those for the low-lying states of \begin{document}$J^P=\frac{1}{2}^+$\end{document} and \begin{document}$\frac{3}{2}^+$\end{document} baryons with flavors \begin{document}$(ccq)$\end{document}, \begin{document}$(bcq)$\end{document}, and \begin{document}$(bbq)$\end{document}. Comparisons with other approaches are also presented.
Published:   , doi: 10.1088/1674-1137/44/2/024101
Abstract:
We investigate the mass spectrum of the \begin{document}$ss \bar s \bar s$\end{document} tetraquark states within the relativized quark model. By solving the Schrödinger-like equation with the relativized potential, the masses of the S− and P−wave \begin{document}$ss \bar s \bar s$\end{document} tetraquarks are obtained. The screening effects are also taken into account. It is found that the observed resonant structure \begin{document}$X(2239)$\end{document} in the \begin{document}$e^+e^- \to K^+K^-$\end{document} process by BESIII Collaboration can be assigned as a P−wave \begin{document}$1^{–-}$\end{document} \begin{document}$ss \bar s \bar s$\end{document} tetraquark state. Furthermore, the radiative transition and strong decay behaviors of this structure are also estimated, which can provide helpful information for future experimental searches.
Published:   , doi: 10.1088/1674-1137/44/1/015104
Abstract:
This paper is devoted to investigate charged vector particles tunneling via horizons of a pair of accelerating rotating charged NUT black hole under the influence of quantum gravitational effects. For this purpose, we use the modified Proca equation incorporating generalized uncertainty principle. Using the WKB approximation to the field equation, we obtain a modified tunneling rate and the corresponding corrected Hawking temperature for this black hole. Moreover, we analyze the graphical behavior of corrected Hawking temperature \begin{document}$T'_{H}$\end{document} with respect to the event horizon for the given black hole. By considering quantum gravitational effects on Hawking temperatures, we discuss the stability analysis of this black hole. For a pair of black holes, the temperature \begin{document}$T'_{H}$\end{document} increases with the increase in rotation parameters a and \begin{document}$\omega$\end{document}, correction parameter \begin{document}$\beta$\end{document}, black hole acceleration \begin{document}$\alpha$\end{document} and arbitrary parameter k and decreases with the increase in electric e and magnetic charges g.
Published:   , doi: 10.1088/1674-1137/44/1/013103
Abstract:
The theta-dependent gauge theories can be studied by using holographic duality through string theory on certain spacetimes. Via this correspondence we consider a stack of N0 dynamical D0-branes as D-instantons in the background sourced by Nc coincident nonextreme black D4-branes. According to the gauge-gravity duality this D0-D4 brane system corresponds to Yang-Mills theory with a theta angle at finite temperature. We solve the IIA supergravity action by taking account into a sufficiently small backreaction of the Dinstantons and obtain an analytical solution for our D0-D4-brane configuration. Then the dual theory in the large Nc limit can be holographically investigated with the gravity solution. In the dual field theory, we find the coupling constant exhibits the property of asymptotic freedom as it is expected in QCD. The contribution of the theta-dependence to the free energy gets suppressed at high temperature which is basically consistent with the calculation by using the Yang-Mills instanton. The topological susceptibility in the large Nc limit vanishes and this behavior remarkably agrees with the implications from the simulation results at finite temperature. Besides we finally find a geometrical interpretation of the theta-dependence in this holographic system.
Published:   , doi: 10.1088/1674-1137/44/1/015103
Abstract:
We study reheating in some one and two field realizations of fibre inflation. We find that reheating begins with a phase of preheating in which long wavelength fluctuation modes are excited. In two field models there is a danger that the parametric amplification of infrared fluctuations in the second scalar field - associated with an entropy mode - might induce an instability of the curvature fluctuations. We show that, at least in the models we consider, the entropy mode has a sufficiently large mass to prevent this instability. Hence, from the point of view of reheating the models we consider are well-behaved.
Published:   , doi: 10.1088/1674-1137/44/1/014103
Abstract:
The skyrmion stability at finite isospin chemical potential \begin{document}$\mu_I$\end{document} is studied by using the Skyrme Lagrangian with a finite pion mass \begin{document}$m_{\pi}$\end{document}. A critical value \begin{document}$\mu_{I{\rm c}}=\sqrt{3/2}m_{\pi}$\end{document} above which the stable soliton does not exist is found. We also explore some properties of skyrmion as function of \begin{document}$\mu_{I}$\end{document}, i.e., the isoscalar mean square radius and the isoscalar magnetic mean square radius. Finally, considering finite temperature effect to the skyrmion mass, by using the special shape for the profile of the skyrmoin, we obtain a critical temperature \begin{document}$T_{\rm c}$\end{document}, above which the skyrmion mass does not have a minimum, which can be interpreted as the occurrence of deconfinement phase transition.
Published:   , doi: 10.1088/1674-1137/44/1/014002
Abstract:
We propose the transverse velocity (\begin{document}$\beta_T$\end{document}) dependence of the anti-deuteron to deuteron ratio as a new observable to search for the QCD critical point in heavy-ion collisions. The QCD critical point can attract the system evolution trajectory in the QCD phase diagram, which is known as focusing effect. To quantify this effect, we employ thermal model and hadronic transport model to simulate the dynamical particle emission along a hypothetical focusing trajectory near critical point. We found the focusing effect can lead to anomalous \begin{document}$\beta_T$\end{document} dependence of \begin{document}$\bar{p}/p$\end{document}, \begin{document}$\bar{d}/d$\end{document} and \begin{document}$^3\overline{\rm{He}}/^3{\rm{He}}$\end{document} ratios. We examined the \begin{document}$\beta_T$\end{document} dependence of \begin{document}$\bar{p}/p$\end{document} and \begin{document}$\bar{d}/d$\end{document} ratios of central Au+Au collisions at \begin{document}$\sqrt {s_{\rm{NN}}} =$\end{document} 7.7 to 200 GeV measured by the STAR experiment at RHIC. Surprisingly, we only observe a negative slope in \begin{document}$\beta_T$\end{document} dependence of \begin{document}$\bar{d}/d$\end{document} ratio at \begin{document}$\sqrt {s_{\rm{NN}}} =$\end{document} 19.6 GeV, which indicates the trajectory evolution has passed through the critical region. In the future, we could constrain the location of the critical point and/or width of the critical region by making precise measurements on the \begin{document}$\beta_T$\end{document} dependence of \begin{document}$\bar{d}/d$\end{document} ratio at different energies and rapidity.
Published:   , doi: 10.1088/1674-1137/44/1/013101
Abstract:
The heavy quark effective field theory (HQEFT) provides an effective way to deal with the heavy meson decays. In the paper, we adopt two different correlators to derive the light-cone sum rules of the \begin{document}$B \to \pi$\end{document} transition form factors (TFFs) within the framework of HQEFT. We label those two LCSR results as LCSR-\begin{document}${\cal U}$\end{document} and LCSR-\begin{document}${\cal R}$\end{document}, which are for conventional correlator and right-handed correlator, respectively. We observe that the correlation parameter \begin{document}$|\rho_{\rm RU}|$\end{document} for the branching ratio \begin{document}${\cal B}(B \to \pi l \nu_{l})$\end{document} is \begin{document}$\sim 0.85$\end{document}, implying the consistency of the LCSRs under different correlators. Moreover, we obtain \begin{document}$|V_{ub}| _{{\rm LCSR}-{\cal U}} = (3.45^{+0.28}_{-0.20}\pm{0.13}_{\rm{exp}})\times10^{-3}$\end{document} and \begin{document}$|V_{ub}| _{{\rm LCSR}-{\cal R}} = (3.38^{+0.22}_{-0.16} \pm{0.12}_{\rm{exp}})\times10^{-3}$\end{document}. We then obtain \begin{document}$\cal{R}_{\pi}| _{{\rm LCSR}-{\cal U}} = 0.68^{+0.10}_{-0.09}$\end{document} and \begin{document}$\cal{R}_{\pi}| _{{\rm LCSR}-{\cal R}} = 0.65^{+0.13}_{-0.11}$\end{document}, both of them agree with the Lattice QCD predictions. Thus the HQEFT provides a useful framework for studying the B meson decays. Moreover, by using right-handed correlator, the twist-2 terms shall dominant the TFF \begin{document}$f^+(q^2)$\end{document}, which approaches over ~97% contribution in the whole \begin{document}$q^2$\end{document}-region; and the large twist-3 uncertainty for the conventional correlator is greatly suppressed. One can thus adopt the LCSR-\begin{document}${\cal R}$\end{document} prediction to test the properties of the various models for the pion twist-2 distribution amplitudes.
Published:   , doi: 10.1088/1674-1137/44/1/014101
Abstract:
We show that the data of \begin{document}$p_{T}$\end{document} spectra of \begin{document}$\Omega^{-}$\end{document} and \begin{document}$\phi$\end{document} at midrapidity in inelastic events in \begin{document}$pp$\end{document} collisions at \begin{document}$\sqrt{s}=$\end{document} 13 TeV exhibit a constituent quark number scaling property, which is a clear signal of quark combination mechanism at hadronization. We use a quark combination model under equal velocity combination approximation to systematically study the production of identified hadrons in \begin{document}$pp$\end{document} collisions at \begin{document}$\sqrt{s}$\end{document}= 13 TeV. The midrapidity data of \begin{document}$p_{T}$\end{document} spectra of proton, \begin{document}$\Lambda$\end{document}, \begin{document}$\Xi^{-}$\end{document}, \begin{document}$\Omega^{-}$\end{document}, \begin{document}$\phi$\end{document} and \begin{document}$K^{*}$\end{document} in inelastic events are simultaneously well fitted by the model. The data of multiplicity dependency of yields of these hadrons are also well understood. The strong \begin{document}$p_{T}$\end{document} dependence for data of \begin{document}$p/\phi$\end{document} ratio is well explained by the model, which further suggests that the production of two hadrons with similar masses is determined by their quark contents at hadronization. \begin{document}$p_{T}$\end{document} spectra of strange hadrons at midrapidity in different multiplicity classes in \begin{document}$pp$\end{document} collisions at \begin{document}$\sqrt{s}=$\end{document} 13 TeV are predicted to further test the model in the future. The midrapidity \begin{document}$p_{T}$\end{document} spectra of soft (\begin{document}$p_T < 2$\end{document} GeV/c) strange quark and up/down quark at hadronization in \begin{document}$pp$\end{document} collisions at \begin{document}$\sqrt{s}=$\end{document} 13 TeV are extracted.